A System of Three Super Earths Transiting the Late K-Dwarf GJ 9827 at Thirty Parsecs

A System of Three Super Earths Transiting the Late K-Dwarf GJ 9827 at Thirty Parsecs
Authors: 

Rodriguez et al 

Abstract: 

We report the discovery of three small transiting planets orbiting GJ 9827, a bright (K = 7.2) nearby late K-type dwarf star. GJ 9827 hosts a 1.64+0.22−0.20 R⊕ super Earth on a 1.2 day period, a 1.29+0.17−0.16 R⊕ super Earth on a 3.6 day period, and a 2.08+0.28−0.26 R⊕ super Earth on a 6.2 day period. The radii of the planets transiting GJ 9827 span the transition between predominantly rocky and gaseous planets, and GJ 9827 b and c fall in or close to the known gap in the radius distribution of small planets between these populations. At a distance of ∼30 parsecs, GJ 9827 is the closest exoplanet host discovered by K2 to date, making these planets well-suited for atmospheric studies with the upcoming James Webb Space Telescope. The GJ 9827 system provides a valuable opportunity to characterize interior structure and atmospheric properties of coeval planets spanning the rocky to gaseous transition.

Three Small Super-Earths Transiting the nearby star GJ 9827

Three Small Super-Earths Transiting the nearby star GJ 9827

Authors:

Niraula et al

Abstract:

We report on the discovery of three transiting planets around GJ~9827. The planets have radii of 1.75+0.11−0.12, 1.36+0.09−0.09, and 2.10+0.15−0.15~R⊕, and periods of 1.20896, 3.6480, and 6.2014 days, respectively. The detection was made in Campaign 12 observations as part of our K2 survey of nearby stars. GJ~9827 is a V=10.39~mag K6V star at distance of 30.3 parsecs and the nearest star to be found hosting planets by Kepler and K2. The radial velocity follow-up, high resolution imaging, and detection of multiple transiting objects near commensurability drastically reduce the false positive probability. The orbital periods of GJ~9827~b, c and d planets are very close to the 1:3:5 mean motion resonance. Our preliminary analysis shows that GJ~9827 planets are excellent candidates for atmospheric observations. Besides, the planetary radii span both sides of the rocky and gaseous divide, hence the system will be an asset in expanding our understanding of the threshold.

Rocky exoplanets are expected to be eroded by space weather in a similar way as in the solar system. In particular, Mercury is one of the dramatically eroded planets whose material continuously escapes into its exosphere and further into space. This escape is well traced by sodium atoms scattering sunlight. Due to solar wind impact, micrometeorite impacts, photo-stimulated desorption and thermal desorption, sodium atoms are released from surface regolith. Some of these released sodium atoms are escaping from Mercury's gravitational-sphere. They are dragged anti-Sun-ward and form a tail structure. We expect similar phenomena on exoplanets. The hot super-Earth 61 Vir b orbiting a G3V star at only 0.05 au may show a similar structure. Because of its small separation from the star, the sodium release mechanisms may be working more efficiently on hot super-Earths than on Mercury, although the strong gravitational force of Earth-sized or even more massive planets may be keeping sodium atoms from escaping from the planet. Here, we performed model simulations for Mercury (to verify our model) and 61 Vir b as a representative super-Earth. We have found that sodium atoms can escape from this exoplanet due to stellar wind sputtering and micrometeorite impacts, to form a sodium tail. However, in contrast to Mercury, the tail on this hot super-Earth is strongly aligned with the anti-starward direction because of higher light pressure. Our model suggests that 61 Vir b seems to have an exo-base atmosphere like that of Mercury.

Space Weathering of Super-Earths: Model Simulations of Exospheric Sodium Escape from 61 Virgo b

Authors:

Yoneda et al

Abstract:

Rocky exoplanets are expected to be eroded by space weather in a similar way as in the solar system. In particular, Mercury is one of the dramatically eroded planets whose material continuously escapes into its exosphere and further into space. This escape is well traced by sodium atoms scattering sunlight. Due to solar wind impact, micrometeorite impacts, photo-stimulated desorption and thermal desorption, sodium atoms are released from surface regolith. Some of these released sodium atoms are escaping from Mercury's gravitational-sphere. They are dragged anti-Sun-ward and form a tail structure. We expect similar phenomena on exoplanets. The hot super-Earth 61 Vir b orbiting a G3V star at only 0.05 au may show a similar structure. Because of its small separation from the star, the sodium release mechanisms may be working more efficiently on hot super-Earths than on Mercury, although the strong gravitational force of Earth-sized or even more massive planets may be keeping sodium atoms from escaping from the planet. Here, we performed model simulations for Mercury (to verify our model) and 61 Vir b as a representative super-Earth. We have found that sodium atoms can escape from this exoplanet due to stellar wind sputtering and micrometeorite impacts, to form a sodium tail. However, in contrast to Mercury, the tail on this hot super-Earth is strongly aligned with the anti-starward direction because of higher light pressure. Our model suggests that 61 Vir b seems to have an exo-base atmosphere like that of Mercury.

Extinction and the Dimming of KIC 8462852

Extinction and the Dimming of KIC 8462852

Authors:

Meng et al

Abstract:

To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star over a wide wavelength range from the UV to the mid-infrared from 2015 October through 2016 December, using Swift, Spitzer and AstroLAB IRIS. The star faded in a manner similar to the long-term fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period reported is 22.1 ± 9.7 mmag yr−1 in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in the ground-based B measurements, 14.0 ± 4.5 mmag in V, and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2 mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at gsim3σ by three different observatories operating from the UV to the IR. The presence of long-term secular dimming means that previous spectral energy distribution models of the star based on photometric measurements taken years apart may not be accurate. We find that stellar models with ${T}_{\mathrm{eff}}=7000\mbox{--}7100$ K and ${A}_{V}\sim 0.73$ best fit the Swift data from UV to optical. These models also show no excess in the near-simultaneous Spitzer photometry at 3.6 and 4.5 μm, although a longer wavelength excess from a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of the fading favors a relatively neutral color (i.e., ${R}_{V}\gtrsim 5$, but not flat across all the bands) compared with the extinction law for the general interstellar medium (${R}_{V}=3.1$), suggesting that the dimming arises from circumstellar material.

A 1574-day periodicity of transits orbiting KIC 8462852

A 1574-day periodicity of transits orbiting KIC 8462852

Authors:

Sacco et al

Abstract:
Observations of the main sequence F3 V star KIC 8462852 (also known as Boyajian's star) revealed extreme aperiodic dips in flux up to 20% during the four years of the Kepler mission. Smaller dips (< 2%) were also observed with ground-based telescopes between May and September 2017. We investigated possible correlation between recent dips and the major dips in the last 100 days of the Kepler mission. We compared Kepler light curve data, 2017 data from two observatories (TFN, OGG) which are part of the Las Cumbres Observatory (LCO) network and Sternberg observatory archival data, and determined that observations are consistent with a 1,574-day (4.31 year) periodicity of a transit (or group of transits) orbiting Boyajian's star within the habitable zone. It is unknown if transits that have produced other major dips as observed during the Kepler mission (e.g. D792) share the same orbital period. Nevertheless, the proposed periodicity is a step forward in guiding future observation efforts.

Optical Polarimetry of KIC 8462852 in May-August 2017

Optical Polarimetry of KIC 8462852 in May-August 2017 

Authors:

Steele et al

Abstract: 

We present optical polarimetry in the period May-August 2017 of the enigmatic "dipping" star KIC 8462852. During that period three ~1% photometric dips were reported by other observers. We measured the average absolute polarization of the source, and find no excess or unusual polarization compared to a nearby comparison star. We place tight upper limits on any change in the degree of polarization of the source between epochs in- and out-of-dip of less than 0.1% (8500-Ang.) and less than 0.2% (7050-Ang. and 5300-Ang.). How our limits are interpreted depends on the specific model being considered. If the whole stellar disk were covered by material with an optical depth of ~0.01 then the fractional polarisation introduced by this material must be less than 10-20%. While our non-detection does not constrain the comet scenario, it predicts that even modest amounts of dust that have properties similar to Solar System comets may be detectable. We note that the sensitivity of our method scales with the depth of the dip. Should a future ~20% photometric dip be observed (as was previously detected by Kepler) our method would constrain any induced polarization associated with any occulting material to 0.5-1.0%.

Detection of a repeated transit signature in the light curve of the enigma star KIC 8462852: a 928-day period?

Detection of a repeated transit signature in the light curve of the enigma star KIC 8462852: a 928-day period?

Authors:

Kiefer et al

Abstract:
As revealed by its peculiar Kepler light curve, the enigmatic star KIC 8462852 undergoes short and deep flux dimmings at a priori unrelated epochs. It presents nonetheless all other characteristics of a quiet 1 Gyr old F3V star. These dimmings resemble the absorption features expected for the transit of dust cometary tails. The exocomet scenario is therefore most commonly advocated. We reanalyzed the Kepler data and extracted a new high-quality light curve to allow for the search of shallow signature of single or a few exocomets. We discovered that among the 22 flux dimming events that we identified, two events present a striking similarity. These events occurred 928.25 days apart, lasted for 4.4 days with a drop of the star brightness by 1000 ppm. We show that the light curve of these events is well explained by the occultation of the star by a giant ring system, or the transit of a string of half a dozen of exocomets with a typical dust production rate of 105-106 kg/s. Assuming that these two similar events are related to the transit of the same object, we derive a period of 928.25 days. The following transit was expected in March 2017 but bad weather prohibited us to detect it from ground-based spectroscopy. We predict that the next event will occur from the 3rd to the 8th of October 2019.

Inside-Out Planet Formation. IV. Pebble Evolution and Planet Formation Timescales

Inside-Out Planet Formation. IV. Pebble Evolution and Planet Formation Timescales

Authors:

Hu et al

Abstract:
Systems with tightly-packed inner planets (STIPs) are very common. Chatterjee & Tan proposed Inside-Out Planet Formation (IOPF), an in situ formation theory, to explain these planets. IOPF involves sequential planet formation from pebble-rich rings that are fed from the outer disk and trapped at the pressure maximum associated with the dead zone inner boundary (DZIB). Planet masses are set by their ability to open a gap and cause the DZIB to retreat outwards. We present models for the disk density and temperature structures that are relevant to the conditions of IOPF. For a wide range of DZIB conditions, we evaluate the gap opening masses of planets in these disks that are expected to lead to truncation of pebble accretion onto the forming planet. We then consider the evolution of dust and pebbles in the disk, estimating that pebbles typically grow to sizes of a few cm during their radial drift from several tens of AU to the inner, ≲1AU-scale disk. A large fraction of the accretion flux of solids is expected to be in such pebbles. This allows us to estimate the timescales for individual planet formation and entire planetary system formation in the IOPF scenario. We find that to produce realistic STIPs within reasonable timescales similar to disk lifetimes requires disk accretion rates of ∼10−9M⊙yr−1 and relatively low viscosity conditions in the DZIB region, i.e., Shakura-Sunyaev parameter of α∼10−4.

X-ray photoevaporation’s limited success in the formation of planetesimals by the streaming instability

X-ray photoevaporation’s limited success in the formation of planetesimals by the streaming instability

Authors:

Ercolano et al

Abstract:

The streaming instability is often invoked as solution to the fragmentation and drift barriers in planetesimal formation, catalysing the aggregation of dust on kyr time-scales to grow km-sized cores. However, there remains a lack of consensus on the physical mechanism(s) responsible for initiating it. One potential avenue is disc photoevaporation, wherein the preferential removal of relatively dust-free gas increases the disc metallicity. Late in the disc lifetime, photoevaporation dominates viscous accretion, creating a gradient in the depleted gas surface density near the location of the gap. This induces a local pressure maximum that collects drifting dust particles, which may then become susceptible to the streaming instability. Using a one-dimensional viscous evolution model of a disc subject to internal X-ray photoevaporation, we explore the efficacy of this process to build planetesimals. Over a range of parameters, we find that the amount of dust mass converted into planetesimals is often <1 a="" across="" an="" and="" are="" at="" au.="" be="" best="" common="" conclude="" considered="" contrast="" cores.="" debris="" discs="" driven="" far-ultra-violet="" few="" for="" formation="" in="" investigation="" large="" m="" may="" mechanism="" model="" most="" of="" our="" photoevaporation="" planetary="" rather="" recent="" relevant="" reported="" results="" similar="" spread="" tens="" than="" that="" the="" to="" we="">100 au) disc radii. The discrepancies are primarily a consequence of the different photoevaporation profiles assumed. Until observations more tightly constrain photoevaporation models, the relevance of this process to the formation of planets remains uncertain.

The structure of young embedded protostellar discs

The structure of young embedded protostellar discs

Authors:

MacFarlane et al

Abstract:
Young protostellar discs provide the initial conditions for planet formation. The properties of these discs may be different from those of late-phase (T Tauri) discs due to continuing infall from the envelope and protostellar variability resulting from irregular gas accretion. We use a set of hydrodynamic simulations to determine the structure of discs forming in collapsing molecular clouds. We examine how radiative feedback from the host protostar affects the disc properties by examining three regimes: without radiative feedback, with continuous radiative feedback and with episodic feedback, similar to FU Ori-type outbursts. We find that the radial surface density and temperature profiles vary significantly as the disc accretes gas from the infalling envelope. These profiles are sensitive to the presence of spiral structure, induced by gravitational instabilities, and the radiative feedback provided by the protostar, especially in the case when the feedback is episodic. We also investigate whether mass estimates from position–velocity (PV) diagrams are accurate for early-phase discs. We find that the protostellar system mass (i.e. the mass of the protostar and its disc) is underestimated by up to 20 per cent, due to the impact of an enhanced radial pressure gradient on the gas. The mass of early-phase discs is a significant fraction of the mass of the protostar, so PV diagrams cannot accurately provide the mass of the protostar alone. The enhanced radial pressure gradient expected in young discs may lead to an increased rate of dust depletion due to gas drag, and therefore to a reduced dust-to-gas ratio.

Is There a Temperature Limit in Planet Formation at 1000 K?

Is There a Temperature Limit in Planet Formation at 1000 K?

Authors:

Demirci et al

Abstract:
Dust drifting inward in protoplanetary disks is subject to increasing temperatures. In laboratory experiments, we tempered basaltic dust between 873 K and 1273 K and find that the dust grains change in size and composition. These modifications influence the outcome of self-consistent low speed aggregation experiments showing a transition temperature of 1000\,K. Dust tempered at lower temperatures grows to a maximum aggregate size of 2.02±0.06 mm, which is 1.49±0.08 times the value for dust tempered at higher temperatures. A similar size ratio of 1.75±0.16 results for a different set of collision velocities. This transition temperature is in agreement with orbit temperatures deduced for observed extrasolar planets. Most terrestrial planets are observed at positions equivalent to less than 1000 K. Dust aggregation on the millimeter-scale at elevated temperatures might therefore be a key factor for terrestrial planet formation.

Episodic accretion: the interplay of infall and disc instabilities

Episodic accretion: the interplay of infall and disc instabilities

Authors:

Kuffmeier et al

Abstract:
Using zoom-simulations carried out with the adaptive mesh-refinement code RAMSES with a dynamic range of up to 227≈1.34×108 we investigate the accretion profiles around six stars embedded in different environments inside a (40 pc)3 giant molecular cloud, the role of mass infall and disc instabilities on the accretion profile, and thus on the luminosity of the forming protostar. Our results show that the environment in which the protostar is embedded determines the overall accretion profile of the protostar. Infall onto the circumstellar disc may trigger gravitational disc instabilities in the disc at distances of around ~10 to ~50 AU leading to rapid transport of angular momentum and strong accretion bursts. These bursts typically last for about ~10 to a ~100 years, consistent with typical orbital times at the location of the instability, and enhance the luminosity of the protostar. Calculations with the stellar evolution code \mesa\ show that the accretion bursts induce significant changes in the protostellar properties, such as the stellar temperature and radius. We apply the obtained protostellar properties to produce synthetic observables with RadMC and predict that accretion bursts lead to observable enhancements around 20 to 200 μm in the spectral energy distribution of Class 0 type young stellar objects.

Mottled protoplanetary disk ionization by magnetically-channeled T Tauri star energetic particles

Mottled protoplanetary disk ionization by magnetically-channeled T Tauri star energetic particles 

Authors: 

Fraschetti et al 

Abstract:
The evolution of protoplanetary disks is believed to be driven largely by angular momentum transport resulting from magnetized disk winds and turbulent viscosity. The ionization of the disk that is essential for these processes has been thought due to host star coronal X-rays but could also arise from energetic particles produced by coronal flares or by travelling shock waves and advected by the stellar wind. We have performed test-particle numerical simulations of energetic protons propagating into a realistic T~Tauri stellar wind, including a superposed small-scale magnetostatic turbulence. The isotropic (Kolmogorov power spectrum) turbulent component is synthesised along the individual particle trajectories. We have investigated the particle energy range, [0.1−10] GeV, consistent with expectations from {\it Chandra} X-ray observations of large flares on T~Tauri stars and with recent indications by the {\it Herschel} Space Observatory of a significant contribution of energetic particles to the disk ionization of young stars. In contrast with a previous theoretical study finding dominance of energetic particle ionization over X-ray ionization throughout the disk, we find that the disk ionization is likely dominated by X-rays over much of its area except within narrow regions where the energetic particles are channeled onto the disk by the strongly-tangled and turbulent magnetic field lines. The radial thickness of such regions is ∼5 stellar radii close to the star and broadens with increasing radial distance. In these regions, the disk ionization due to energetic particles can locally dominate the stellar X-ray contribution. This likely continues out to large distances from the star (10 AU or greater) where particles can be copiously advected and diffused by the turbulent wind.

The optical+infrared L dwarf spectral sequence of young planetary-mass objects in the Upper Scorpius association

The optical+infrared L dwarf spectral sequence of young planetary-mass objects in the Upper Scorpius association


Authors:

Lodieu et al

Abstract:

We present the results of photometric and spectroscopic follow-ups of the lowest mass member candidates in the nearest OB association, Upper Scorpius (5-10 Myr; 145+/-17 pc), with the Gran Telescopio de Canarias (GTC) and European Southern Observatory (ESO) Very Large Telescope (VLT). We confirm the membership of the large majority (>80%) of the candidates selected originally photometrically and astrometrically based on their spectroscopic features, weak equivalent widths of gravity-sensitive doublets, and radial velocities. Confirmed members follow a sequence over a wide magnitude range (J=17.0-19.3 mag) in several colour-magnitude diagrams with optical, near-, and mid-infrared photometry, and have near-infrared spectral types in the L1-L7 interval with likely masses below 15 Jupiter masses. We find that optical spectral types tend to be earlier than near-infrared spectral types by a few subclasses for spectral types later than M9. We investigate the behaviour of spectral indices defined in the literature as a function of spectral type and gravity by comparison with values reported in the literature for young and old dwarfs. We also derive effective temperatures in the 1900-1600K from fits of synthetic model-atmosphere spectra to the observed photometry but we caution the procedure carries large uncertainties. We determine bolometric corrections for young L dwarfs with ages of ~5-10 Myr (Upper Sco association) and find them similar in the J-band but larger by 0.1-0.4 mag in the K-band with respect to field L dwarfs. Finally, we discovered two faint young L dwarfs, VISTAJ1607-2146 (L4.5) and VISTAJ1611-2215 (L5) that have Hα emission and possible flux excesses at 4.5 microns, pointing towards the presence of accretion from a disk onto the central objects of mass below ~15 Jupiter masses at the age of 5-10 Myr.

A Survey For Planetary-mass Brown Dwarfs in the Taurus and Perseus Star-forming Regions

A Survey For Planetary-mass Brown Dwarfs in the Taurus and Perseus Star-forming Regions

Authors:

Esplin et al

Abstract:
We present the initial results from a survey for planetary-mass brown dwarfs in the Taurus star-forming region. We have identified brown dwarf candidates in Taurus using proper motions and photometry from several ground- and space-based facilities. Through spectroscopy of some of the more promising candidates, we have found 18 new members of Taurus. They have spectral types ranging from mid M to early L and they include the four faintest known members in extinction-corrected K_s, which should have masses as low as ~4-5 M_Jup according to evolutionary models. Two of the coolest new members (M9.25, M9.5) have mid-IR excesses that indicate the presence of disks. Two fainter objects with types of M9-L2 and M9-L3 also have red mid-IR colors relative to photospheres at <=L0, but since the photospheric colors are poorly defined at >L0, it is unclear whether they have excesses from disks. We also have obtained spectra of candidate members of the IC 348 and NGC 1333 clusters in Perseus that were identified by Luhman et al. (2016). Eight candidates are found to be probable members, three of which are among the faintest and least-massive known members of the clusters (~5 M_Jup).

First Detection of a Strong Magnetic Field on a Bursty Brown Dwarf: Puzzle Solved

First Detection of a Strong Magnetic Field on a Bursty Brown Dwarf: Puzzle Solved 

Authors:

Beryungia et al

Abstract:
We report the first direct detection of a strong, 5 kG magnetic field on the surface of an active brown dwarf. LSR J1835+3259 is an M8.5 dwarf exhibiting transient radio and optical emission bursts modulated by fast rotation. We have detected the surface magnetic field as circularly polarized signatures in the 819 nm sodium lines when an active emission region faced the Earth. Modeling Stokes profiles of these lines reveals the effective temperature of 2800 K and log gravity acceleration of 4.5. These parameters place LSR J1835+3259 on evolutionary tracks as a young brown dwarf with the mass of 55±4 MJ and age of 22±4 Myr. Its magnetic field is at least 5.1 kG and covers at least 11% of the visible hemisphere. The active region topology recovered using line profile inversions comprises hot plasma loops with a vertical stratification of optical and radio emission sources. These loops rotate with the dwarf in and out of view causing periodic emission bursts. The magnetic field is detected at the base of the loops. This is the first time that we can quantitatively associate brown dwarf non-thermal bursts with a strong, 5 kG surface magnetic field and solve the puzzle of their driving mechanism. This is also the coolest known dwarf with such a strong surface magnetic field. The young age of LSR J1835+3259 implies that it may still maintain a disk, which may facilitate bursts via magnetospheric accretion, like in higher-mass T Tau-type stars. Our results pave a path toward magnetic studies of brown dwarfs and hot Jupiters.

Possible formation pathways for the low density Neptune-mass planet HAT-P-26b

Possible formation pathways for the low density Neptune-mass planet HAT-P-26b  

Authors:

Ali-Dib et al

Abstract:

We investigate possible pathways for the formation of the low density Neptune-mass planet HAT-P-26b. We use two formation different models based on pebbles and planetesimals accretion, and includes gas accretion, disk migration and simple photoevaporation. The models tracks the atmospheric oxygen abundance, in addition to the orbital period, and mass of the forming planets, that we compare to HAT-P-26b. We find that pebbles accretion can explain this planet more naturally than planetesimals accretion that fails completely unless we artificially enhance the disk metallicity significantly. Pebble accretion models can reproduce HAT-P-26b with either a high initial core mass and low amount of envelope enrichment through core erosion or pebbles dissolution, or the opposite, with both scenarios being possible. Assuming a low envelope enrichment factor as expected from convection theory and comparable to the values we can infer from the D/H measurements in Uranus and Neptune, our most probable formation pathway for HAT-P-26b is through pebble accretion starting around 10 AU early in the disk’s lifetime.

Investigating the physical properties of transiting hot Jupiters with the 1.5-m Kuiper Telescope

Investigating the physical properties of transiting hot Jupiters with the 1.5-m Kuiper Telescope

Authors:

Turner et al

Abstract:

We present new photometric data of 11 hot Jupiter transiting exoplanets (CoRoT-12b, HAT-P-5b, HAT-P-12b, HAT-P-33b, HAT-P-37b, WASP-2b, WASP-24b, WASP-60b, WASP-80b, WASP-103b and XO-3b) in order to update their planetary parameters and to constrain information about their atmospheres. These observations of CoRoT-12b, HAT-P-37b and WASP-60b are the first follow-up data since their discovery. Additionally, the first near-UV transits of WASP-80b and WASP-103b are presented. We compare the results of our analysis with previous work to search for transit timing variations (TTVs) and a wavelength dependence in the transit depth. TTVs may be evidence of a third body in the system, and variations in planetary radius with wavelength can help constrain the properties of the exoplanet’s atmosphere. For WASP-103b and XO-3b, we find a possible variation in the transit depths which may be evidence of scattering in their atmospheres. The B-band transit depth of HAT-P-37b is found to be smaller than its near-IR transit depth and such a variation may indicate TiO/VO absorption. These variations are detected from 2–4.6σ, so follow-up observations are needed to confirm these results. Additionally, a flat spectrum across optical wavelengths is found for five of the planets (HAT-P-5b, HAT-P-12b, WASP-2b, WASP-24b and WASP-80b), suggestive that clouds may be present in their atmospheres. We calculate a refined orbital period and ephemeris for all the targets, which will help with future observations. No TTVs are seen in our analysis with the exception of WASP-80b and follow-up observations are needed to confirm this possible detection.

The Influence of Coronal Mass Ejections on the Mass-loss Rates of Hot-Jupiters

The Influence of Coronal Mass Ejections on the Mass-loss Rates of Hot-Jupiters

Authors:

Cherenkov et al

Abstract:

Hot-Jupiters are subject to extreme radiation and plasma flows coming from their host stars. Past ultraviolet Hubble Space Telescope observations, supported by hydrodynamic models, confirmed that these factors lead to the formation of an extended envelope, part of which lies beyond the Roche lobe. We use gas-dynamic simulations to study the impact of time variations in the parameters of the stellar wind, namely that of coronal mass ejections (CMEs), on the envelope of the typical hot-Jupiter HD 209458b. We consider three CMEs characterized by different velocities and densities, taking their parameters from typical CMEs observed for the Sun. The perturbations in the ram-pressure of the stellar wind during the passage of each CME tear off most of the envelope that is located beyond the Roche lobe. This leads to a substantial increase of the mass-loss rates during the interaction with the CME. We find that the mass lost by the planet during the whole crossing of a CME is of ≈1015 g, regardless of the CME taken into consideration. We also find that over the course of 1 Gyr, the mass lost by the planet because of CME impacts is comparable to that lost because of high-energy stellar irradiation.

Precise masses for the transiting planetary system HD 106315 with HARPS

Precise masses for the transiting planetary system HD 106315 with HARPS

Authors:

Barros et al

Abstract:

The multi-planetary system HD 106315 was recently found in K2 data . The planets have periods of Pb∼9.55 and Pc∼21.06days, and radii of rb=2.44±0.17 and rc=4.35±0.23 R⊕. The brightness of the host star (V=9.0 mag) makes it an excellent target for transmission spectroscopy. However, to interpret transmission spectra it is crucial to measure the planetary masses. We obtained high precision radial velocities for HD~106315 to determine the mass of the two transiting planets discovered with Kepler K2. Our successful observation strategy was carefully tailored to mitigate the effect of stellar variability. We modelled the new radial velocity data together with the K2 transit photometry and a new ground-based partial transit of HD 106315c to derive system parameters. We estimate the mass of HD 106315b to be 12.6 ± 3.2 M⊕ and the density to be 4.7±1.7gcm−3, while for HD 106315c we estimate a mass of 15.2 ± 3.7 M⊕ and a density of 1.01±0.29g\,cm−3. Hence, despite planet c having a radius almost twice as large as planet b, their masses are consistent with one another. We conclude that HD 106315c has a thick hydrogen-helium gaseous envelope. A detailed investigation of HD 106315b using a planetary interior model constrains the core mass fraction to be 5-29\%, and the water mass fraction to be 10-50\%. An alternative, not considered by our model, is that HD 106315b is composed of a large rocky core with a thick H-He envelope. Transmission spectroscopy of these planets will give insight into their atmospheric compositions and also help constrain their core compositions.

Aerosol Properties of the Atmospheres of Extrasolar Giant Planets

Aerosol Properties of the Atmospheres of Extrasolar Giant Planets

Authors:

Lavvas et al

Abstract:

We use a model of aerosol microphysics to investigate the impact of high-altitude photochemical aerosols on the transmission spectra and atmospheric properties of close-in exoplanets, such as HD 209458 b and HD 189733 b. The results depend strongly on the temperature profiles in the middle and upper atmospheres, which are poorly understood. Nevertheless, our model of HD 189733 b, based on the most recently inferred temperature profiles, produces an aerosol distribution that matches the observed transmission spectrum. We argue that the hotter temperature of HD 209458 b inhibits the production of high-altitude aerosols and leads to the appearance of a clearer atmosphere than on HD 189733 b. The aerosol distribution also depends on the particle composition, photochemical production, and atmospheric mixing. Due to degeneracies among these inputs, current data cannot constrain the aerosol properties in detail. Instead, our work highlights the role of different factors in controlling the aerosol distribution that will prove useful in understanding different observations, including those from future missions. For the atmospheric mixing efficiency suggested by general circulation models, we find that the aerosol particles are small (~nm) and probably spherical. We further conclude that a composition based on complex hydrocarbons (soots) is the most likely candidate to survive the high temperatures in hot-Jupiter atmospheres. Such particles would have a significant impact on the energy balance of HD 189733 b's atmosphere and should be incorporated in future studies of atmospheric structure. We also evaluate the contribution of external sources to photochemical aerosol formation and find that their spectral signature is not consistent with observations.

Spin–Orbit Misalignments of Three Jovian Planets via Doppler Tomography

Spin–Orbit Misalignments of Three Jovian Planets via Doppler Tomography

Authors:

Johnson et al

Abstract:
We present measurements of the spin–orbit misalignments of the hot Jupiters HAT-P-41 b and WASP-79 b, and the aligned warm Jupiter Kepler-448 b. We obtain these measurements with Doppler tomography, where we spectroscopically resolve the line profile perturbation during the transit due to the Rossiter–McLaughlin effect. We analyze time series spectra obtained during portions of five transits of HAT-P-41 b, and find a value of the spin–orbit misalignment of $\lambda =-{22.1}_{-6.0}^{{+0.8}^{^\circ }}$. We reanalyze the radial velocity Rossiter–McLaughlin data on WASP-79 b obtained by Addison et al. using Doppler tomographic methodology. We measure $\lambda =-{99.1}_{-3.9}^{{+4.1}^{^\circ }}$, consistent with but more precise than the value found by Addison et al. For Kepler-448 b we perform a joint fit to the Kepler light curve, Doppler tomographic data, and a radial velocity data set from Lillo-Box et al. We find an approximately aligned orbit ($\lambda =-{7.1}_{-2.8}^{{+4.2}^{^\circ }}$), in agreement with the value found by Bourrier et al. Through analysis of the Kepler light curve we measure a stellar rotation period of ${P}_{\mathrm{rot}}=1.27\pm 0.11$ days, and use this to argue that the full three-dimensional spin–orbit misalignment is small, $\psi \sim 0^\circ $.

The discovery and mass measurement of a new ultra-short-period planet: EPIC~228732031b

The discovery and mass measurement of a new ultra-short-period planet: EPIC~228732031b

Authors:

Dai et al

Abstract:
We report the discovery of a new ultra-short-period planet and summarize the properties of all such planets for which the mass and radius have been measured. The new planet, EPIC~228732031b, was discovered in {\it K2} Campaign 10. It has a radius of 1.81+0.16−0.12 R⊕ and orbits a G dwarf with a period of 8.9 hours. Radial velocities obtained with Magellan/PFS and TNG/HARPS-N show evidence for stellar activity along with orbital motion. We determined the planetary mass using two different methods: (1) the "floating chunk offset" method, based only on changes in velocity observed on the same night, and (2) a Gaussian process regression based on both the radial-velocity and photometric time series. The results are consistent and lead to a mass measurement of 6.5±1.6 M⊕, and a mean density of 6.0+3.0−2.7~g~cm−3.

OGLE-2017-BLG-0173Lb: Low Mass-Ratio Planet in a "Hollywood" Microlensing Event

OGLE-2017-BLG-0173Lb: Low Mass-Ratio Planet in a "Hollywood" Microlensing Event

Authors:

Hwang et al

Abstract:
We present the discovery of microlensing planet OGLE-2017-BLG-0173Lb, with planet-host mass ratio q=6.5×10−5, among the lowest ever detected. The planetary perturbation is nevertheless quite strongly detected, with Δχ2∼10,000, because it arises from a bright (therefore, large) source passing over, and partially enveloping, the planetary caustic. We present a simple formalism that can be used to estimate the sensitivity of other giant-source ("Hollywood") events to planets and show that they can lead to detections close to, but perhaps not quite reaching, the Earth/Sun mass ratio of 3×10−6. The best estimated Bayesian parameters for this system are host-mass M=0.42+0.40−0.24M⊙, planet mass, mp=9+11−6M⊕, and projected separation $a_\perp \sim 4\,\au$. The measured lens-source relative proper motion $\mu=6\,\masyr$ will permit imaging of the lens in about 15 years or at first light on adaptive-optics imagers on next-generation ("30 meter") telescopes, whichever comes first.

How Mini Neptunes Form

The formation of mini-Neptunes

Authors:

Venturini et al

Abstract:

Mini-Neptunes seem to be common planets. In this work we investigate the possible formation histories and predicted occurrence rates of mini-Neptunes assuming the planets form beyond the iceline. We consider pebble and planetesimal accretion accounting for envelope enrichment and two different opacity conditions. We find that the formation of mini-Neptunes is a relatively frequent output when envelope enrichment by volatiles is included, and that there is a "sweet spot" for mini-Neptune formation with a relatively low solid accretion rate of ~10^{-6} Earth masses per year. This rate is typical for low/intermediate-mass protoplanetary disks and/or disks with low metallicities. With pebble accretion, envelope enrichment and high opacity favor the formation of mini-Neptunes, with more efficient formation at large semi-major axes (~30 AU) and low disk viscosity. For planetesimal accretion, such planets can form also without enrichment, with the opacity being a key aspect in the growth history and favorable formation location. Finally, we show that the formation of Neptune-like planets remains a challenge for planet formation theories.

Obliquity and Eccentricity Constraints For Terrestrial Exoplanets

Obliquity and Eccentricity Constraints For Terrestrial Exoplanets

Authors:

Kane et al

Abstract:

Exoplanet discoveries over recent years have shown that terrestrial planets are exceptionally common. Many of these planets are in compact systems that result in complex orbital dynamics. A key step towards determining the surface conditions of these planets is understanding the latitudinally dependent flux incident at the top of the atmosphere as a function of orbital phase. The two main properties of a planet that influence the time-dependent nature of the flux are the obliquity and orbital eccentricity of the planet. We derive the criterion for which the flux variation due to obliquity is equivalent to the flux variation due to orbital eccentricity. This equivalence is computed for both the maximum and average flux scenarios, the latter of which includes the effects of the diurnal cycle. We apply these calculations to four known multi-planet systems (GJ 163, K2-3, Kepler-186, Proxima Centauri), where we constrain the eccentricity of terrestrial planets using orbital dynamics considerations and model the effect of obliquity on incident flux. We discuss the implications of these simulations on climate models for terrestrial planets and outline detectable signatures of planetary obliquity.

Space Technology for Directly Imaging and Characterizing Exo-Earths

Space Technology for Directly Imaging and Characterizing Exo-Earths

Authors:

Crill et al

Abstract:

The detection of Earth-like exoplanets in the habitable zone of their stars, and their spectroscopic characterization in a search for biosignatures, requires starlight suppression that exceeds the current best ground-based performance by orders of magnitude. The required planet/star brightness ratio of order 1e-10 at visible wavelengths can be obtained by blocking stellar photons with an occulter, either externally (a starshade) or internally (a coronagraph) to the telescope system, and managing diffracted starlight, so as to directly image the exoplanet in reected starlight. Coronagraph instruments require advancement in telescope aperture (either monolithic or segmented), aperture obscurations (obscured by secondary mirror and its support struts), and wavefront error sensitivity (e.g. line-of-sight jitter, telescope vibration, polarization). The starshade, which has never been used in a science application, benefits a mission by being decoupled from the telescope, allowing a loosening of telescope stability requirements. In doing so, it transfers the difficult technology from the telescope system to a large deployable structure (tens of meters to greater than 100 m in diameter) that must be positioned precisely at a distance of tens of thousands of kilometers from the telescope. We describe in this paper a roadmap to achieving the technological capability to search for biosignatures on an Earth-like exoplanet from a future space telescope. Two of these studies, HabEx and LUVOIR, include the direct imaging of Earth-sized habitable exoplanets as a central science theme.

All-sky Radio SETI

All-sky Radio SETI

Authors:

Garrett et al

Abstract:
Over the last decade, Aperture Arrays (AA) have successfully replaced parabolic dishes as the technology of choice at low radio frequencies - good examples are the MWA, LWA and LOFAR. Aperture Array based telescopes present several advantages, including sensitivity to the sky over a very wide field-of-view. As digital and data processing systems continue to advance, an all-sky capability is set to emerge, even at GHz frequencies. We argue that assuming SETI events are both rare and transitory in nature, an instrument with a large field-of-view, operating around the so-called water-hole (1-2 GHz), might offer several advantages over contemporary searches. Sir Arthur C. Clarke was the first to recognise the potential importance of an all-sky radio SETI capability, as presented in his book, Imperial Earth. As part of the global SKA (Square Kilometre Array) project, a Mid-Frequency Aperture Array (MFAA) prototype known as MANTIS (Mid- Frequency Aperture Array Transient and Intensity-Mapping System) is now being considered as a precursor for SKA-2. MANTIS can be seen as a first step towards an all-sky radio SETI capability at GHz frequencies. This development has the potential to transform the field of SETI research, in addition to several other scientific programmes.

Protoplanetary disc ‘isochrones’ and the evolution of discs in the M – M d plane

Protoplanetary disc ‘isochrones’ and the evolution of discs in the M – M d plane 

Authors:

Lodato et al

Abstract:
In this paper, we compare simple viscous diffusion models for the disc evolution with the results of recent surveys of the properties of young protoplanetary discs. We introduce the useful concept of ‘disc isochrones’ in the accretion rate - disc mass plane and explore a set of Montecarlo realization of disc initial conditions. We find that such simple viscous models can provide a remarkable agreement with the available data in the Lupus star forming region, with the key requirement that the average viscous evolutionary timescale of the discs is comparable to the cluster age. Our models produce naturally a correlation between mass accretion rate and disc mass that is shallower than linear, contrary to previous results and in agreement with observations. We also predict that a linear correlation, with a tighter scatter, should be found for more evolved disc populations. Finally, we find that such viscous models can reproduce the observations in the Lupus region only in the assumption that the efficiency of angular momentum transport is a growing function of radius, thus putting interesting constraints on the nature of the microscopic processes that lead to disc accretion.

Mid-Infrared Polarization of Herbig Ae/Be Discs

Mid-Infrared Polarization of Herbig Ae/Be Discs

Authors:

Li et al 

Abstract:
We measured mid-infrared polarization of protoplanetary discs to gain new insight into their magnetic fields. Using CanariCam at the 10.4 m Gran Telescopio Canarias, we detected linear polarization at 8.7, 10.3, and 12.5 ${\mu} {\rm m}$ from discs around eight Herbig Ae/Be stars and one T-Tauri star. We analyzed polarimetric properties of each object to find out the most likely interpretation of the data. While the observed mid-infrared polarization from most objects is consistent with polarized emission and/or absorption arising from aligned dust particles, we cannot rule out polarization due to dust scattering for a few objects in our sample. For those objects for which polarization can be explained by polarized emission and/or absorption, we examined how the derived magnetic field structure correlates with the disc position angle and inclination. We found no preference for a certain type of magnetic field. Instead, various configurations (toroidal, poloidal, or complex) are inferred from the observations. The detection rate (64 per cent) of polarized mid-infrared emission and/or absorption supports the expectation that magnetic fields and suitable conditions for grain alignment are common in protoplanetary discs around Herbig Ae/Be stars.

Chemical enrichment of the planet forming region as probed by accretion

Chemical enrichment of the planet forming region as probed by accretion

Authors:

Booth et al

Abstract:

The chemical conditions in the planet forming regions of protoplanetary discs remain difficult to observe directly. Gas accreting from the disc on to the star provides a way to measure the elemental abundances because even refractory species are in an atomic gaseous form. Here we compare the abundance ratios derived from UV lines probing T Tauri accretion streams to simple models of disc evolution. Although the interpretation of line ratios in terms of abundances is highly uncertain, discs with large cavities in mm images tend to have lower Si emission. Since this can naturally be explained by the suppressed accretion of dust, this suggests that abundance variations are at least partially responsible for the variations seen in the line ratios. Our models of disc evolution due to grain growth, radial drift and the flux of volatile species carried as ices on grain surfaces, give rise to a partial sorting of the atomic species based on the volatility of their dominant molecular carriers. This arises because volatiles are left behind at their snow lines while the grains continue to drift. We show that this reproduces the main features seen in the accretion line ratio data, such as C/N ratios that are a few times solar and the correlation between the Si to volatile ratio with mm-flux. We highlight the fact that developing a more robust linkage between line ratios and abundance ratios and acquiring data for larger samples has the potential to cast considerable light on the chemical history of protoplanetary discs.

Planet formation and disk-planet interactions

Planet formation and disk-planet interactions

Authors:

Kley

Abstract:

This review is based on lectures given at the 45th Saas-Fee Advanced Course 'From Protoplanetary Disks to Planet Formation' held in March 2015 in Les Diablerets, Switzerland. Starting with an overview of the main characterictics of the Solar System and extrasolar planets, we describe the planet formation process in terms of the sequential accretion scenario. First the growth processes of dust particles to planetesimals and subsequently to terrestrial planets or planetary cores are presented. This is followed by the formation process of the giant planets either by core accretion or gravitational instability. Finally, the dynamical evolution of the orbital elements as driven by disk-planet interaction and the overall evolution of multi-object systems is presented.

Global Simulations of the Inner Regions of Protoplanetary Disks with Comprehensive Disk Microphysics

Global Simulations of the Inner Regions of Protoplanetary Disks with Comprehensive Disk Microphysics

Author: 

Bai

Abstract:
The gas dynamics of weakly ionized protoplanetary disks (PPDs) is largely governed by the coupling between gas and magnetic fields, described by three non-ideal magnetohydrodynamical (MHD) effects (Ohmic, Hall, ambipolar). Previous local simulations incorporating these processes have revealed that the inner regions of PPDs are largely laminar accompanied by wind-driven accretion. We conduct 2D axisymmetric, fully global MHD simulations of these regions (∼1−20 AU), taking into account all non-ideal MHD effects, with tabulated diffusion coefficients and approximate treatment of external ionization and heating. With net vertical field aligned with disk rotation, the Hall-shear instability strongly amplifies horizontal magnetic field, making the overall dynamics dependent on initial field configuration. Following disk formation, the disk likely relaxes into an inner zone characterized by asymmetric field configuration across the midplane that smoothly transitions to a more symmetric outer zone. Angular momentum transport is driven by both MHD winds and laminar Maxwell stress, with both accretion and decretion flows present at different heights, and modestly asymmetric winds from the two disk sides. With anti-aligned field polarity, weakly magnetized disks settle into an asymmetric field configuration with supersonic accretion flow concentrated at one side of disk surface, and highly asymmetric winds between the two disk sides. In all cases, the wind is magneto-thermal in nature characterized by mass loss rate exceeding the accretion rate. More strongly magnetized disks give more symmetric field configuration and flow structures. Deeper far-UV penetration leads to stronger and less stable outflows. Implications for observations and planet formation are also discussed.

Effect of dust radial drift on viscous evolution of gaseous disk

Effect of dust radial drift on viscous evolution of gaseous disk

Authors:

Kanagawa et al

Abstract:

The total amount of dust (or "metallicity") and the dust distribution in protoplanetary disks are crucial for planet formation. Dust grains radially drift due to gas--dust friction, and the gas is affected by the feedback from dust grains. We investigate the effects of the feedback from dust grains on the viscous evolution of the gas, taking into account the vertical dust settling. The feedback from the grains pushes the gas outward. When the grains are small and the dust-to-gas mass ratio is much smaller than unity, the radial drift velocity is reduced by the feedback effect but the gas still drifts inward. When the grains are sufficiently large or piled-up, the feedback is so effective that forces the gas flows outward. Although the dust feedback is affected by dust settling, we found that the 2D approximation reasonably reproduces the vertical averaged flux of gas and dust. We also performed the 2D two-fluid hydrodynamic simulations to examine the effect of the feedback from the grains on the evolution of the gas disk. We show that when the feedback is effective, the gas flows outward and the gas density at the region within ∼10 AU is significantly depleted. As a result, the dust-to-gas mass ratio at the inner radii may significantly excess unity, providing the environment where planetesimals are easily formed via, e.g., streaming instability. We also show that a simplified 1D model well reproduces the results of the 2D two-fluid simulations, which would be useful for future studies.

Extrasolar Planets and Their Host Stars

Extrasolar Planets and Their Host Stars

Authors:

von Braun et al

Abstract:
In order to understand the exoplanet, you need to understand its parent star. Astrophysical parameters of extrasolar planets are directly and indirectly dependent on the properties of their respective host stars. These host stars are very frequently the only visible component in the systems. This book describes our work in the field of characterization of exoplanet host stars using interferometry to determine angular diameters, trigonometric parallax to determine physical radii, and SED fitting to determine effective temperatures and luminosities. The interferometry data are based on our decade-long survey using the CHARA Array. We describe our methods and give an update on the status of the field, including a table with the astrophysical properties of all stars with high-precision interferometric diameters out to 150 pc (status Nov 2016). In addition, we elaborate in more detail on a number of particularly significant or important exoplanet systems, particularly with respect to (1) insights gained from transiting exoplanets, (2) the determination of system habitable zones, and (3) the discrepancy between directly determined and model-based stellar radii. Finally, we discuss current and future work including the calibration of semi-empirical methods based on interferometric data.

VLA observations of the disk around the young brown dwarf 2MASS J044427+2512

VLA observations of the disk around the young brown dwarf 2MASS J044427+2512 

Authors:

Ricci et al

Abstract:

We present multi-wavelength radio observations obtained with the VLA of the protoplanetary disk surrounding the young brown dwarf 2MASS J04442713+2512164 (2M0444) in the Taurus star forming region. 2M0444 is the brightest known brown dwarf disk at millimeter wavelengths, making this an ideal target to probe radio emission from a young brown dwarf. Thermal emission from dust in the disk is detected at 6.8 and 9.1 mm, whereas the 1.36 cm measured flux is dominated by ionized gas emission. We combine these data with previous observations at shorter sub-mm and mm wavelengths to test the predictions of dust evolution models in gas-rich disks after adapting their parameters to the case of 2M0444. These models show that the radial drift mechanism affecting solids in a gaseous environment has to be either completely made inefficient, or significantly slowed down by very strong gas pressure bumps in order to explain the presence of mm/cm-sized grains in the outer regions of the 2M0444 disk. We also discuss the possible mechanisms for the origin of the ionized gas emission detected at 1.36 cm. The inferred radio luminosity for this emission is in line with the relation between radio and bolometric luminosity valid for for more massive and luminous young stellar objects, and extrapolated down to the very low luminosity of the 2M0444 brown dwarf.

Radio Emission from Ultra-Cool Dwarfs

Radio Emission from Ultra-Cool Dwarfs

Author:

Williams

Abstract:

The 2001 discovery of radio emission from ultra-cool dwarfs (UCDs), the very low-mass stars and brown dwarfs with spectral types of ~M7 and later, revealed that these objects can generate and dissipate powerful magnetic fields. Radio observations provide unparalleled insight into UCD magnetism: detections extend to brown dwarfs with temperatures less than 1000 K, where no other observational probes are effective. The data reveal that UCDs can generate strong (kG) fields, sometimes with a stable dipolar structure; that they can produce and retain nonthermal plasmas with electron acceleration extending to MeV energies; and that they can drive auroral current systems resulting in significant atmospheric energy deposition and powerful, coherent radio bursts. Still to be understood are the underlying dynamo processes, the precise means by which particles are accelerated around these objects, the observed diversity of magnetic phenomenologies, and how all of these factors change as the mass of the central object approaches that of Jupiter. The answers to these questions are doubly important because UCDs are both potential exoplanet hosts, as in the TRAPPIST-1 system, and analogues of extrasolar giant planets themselves.

HATS-43b, HATS-44b, HATS-45b, and HATS-46b: Four Short Period Transiting Giant Planets in the Neptune-Jupiter Mass Range

HATS-43b, HATS-44b, HATS-45b, and HATS-46b: Four Short Period Transiting Giant Planets in the Neptune-Jupiter Mass Range

Authors:

Brahm et al

Abstract:

We report the discovery of four short period extrasolar planets transiting moderately bright stars from photometric measurements of the HATSouth network coupled to additional spectroscopic and photometric follow-up observations. While the planet masses range from 0.26 to 0.90 MJ, the radii are all approximately a Jupiter radii, resulting in a wide range of bulk densities. The orbital period of the planets range from 2.7d to 4.7d, with HATS-43b having an orbit that appears to be marginally non-circular (e= 0.173±0.089). HATS-44 is notable for a high metallicity ([Fe/H]= 0.320±0.071). The host stars spectral types range from late F to early K, and all of them are moderately bright (13.3 less than V less than 14.4), allowing the execution of future detailed follow-up observations. HATS-43b and HATS-46b, with expected transmission signals of 2350 ppm and 1500 ppm, respectively, are particularly well suited targets for atmospheric characterisation via transmission spectroscopy.

EPIC 220504338b: A dense hot-Jupiter transiting a solar analogue

EPIC 220504338b: A dense hot-Jupiter transiting a solar analogue   

Authors:

Espinoza et al

Abstract:

We present the discovery of EPIC 220504338b, a dense hot-Jupiter discovered using photometry from Campaign 8 of the Kepler-2 (K2) mission and high-resolution spectroscopic follow up obtained with the FEROS spectrograph. The planet orbits a V = 13.68 solar analogue in a P=5.81760+0.00003−0.00003/+0.00003 day orbit, has a radius of 0.93+0.10−0.07RJ/0.93−0.07+0.10RJ and a mass of 1.29+0.13−0.14MJ/1.29−0.14+0.13MJ. With a density of 1.97+0.60−0.53/1.97−0.53+0.60 gr/cm3, the planet is among the densest systems known having masses below 2 MJ and Teq greater than 1000, and is just above the temperature limit at which inflation mechanisms are believed to start being important. Based on its mass and radius, we estimate that EPIC 220504338b should have a heavy element content on the order of ∼ 110 M⊕ or greater.

Phase Offsets and the Energy Budgets of Hot Jupiters

Phase Offsets and the Energy Budgets of Hot Jupiters

Authors:

Schwartz et al

Abstract:
Thermal phase curves of short-period planets on circular orbits provide joint constraints on the fraction of incoming energy that is reflected (Bond albedo) and the fraction of absorbed energy radiated by the night hemisphere (heat recirculation efficiency). Many empirical studies of hot Jupiters have implicitly assumed that the dayside is the hottest hemisphere and the nightside is the coolest hemisphere. For a given eclipse depth and phase amplitude, an orbital lag between a planet's peak brightness and its eclipse (a phase offset) implies that planet's nightside emits greater flux. To quantify how phase offsets impact the energy budgets of short-period planets, we compile all infrared observations of the nine planets with multi-band eclipse depths and phase curves. Accounting for phase offsets shifts planets to lower Bond albedo and greater day--night heat transport, usually by ≲1σ. We find a somewhat higher nightside temperature for WASP-43b, but the planet still exhibits an unusually high day-night temperature contrast compared to other planets of the same irradiation temperature. For WASP-12b, our more accurate analysis suggests that the planet has a slightly lower Bond albedo, and much greater day-night recirculation efficiency than previously reported. The planet no longer fits the trend of increasing day-night temperature contrast with greater instellation.

No large population of unbound or wide-orbit Jupiter-mass planets

No large population of unbound or wide-orbit Jupiter-mass planets

Authors:

Mroz et al

Abstract:
Gravitational microlensing is the only method capable of exploring the entire population of free-floating planets down to Mars-mass objects, because the microlensing signal does not depend on the brightness of the lensing object. A characteristic timescale of microlensing events depends on the mass of the lens: the less massive the lens, the shorter the microlensing event. A previous analysis of 474 microlensing events found an excess of very short events (1-2 days) - more than known stellar populations would suggest - indicating the existence of a large population of unbound or wide-orbit Jupiter-mass planets (reported to be almost twice as common as main-sequence stars). These results, however, do not match predictions of planet formation theories and are in conflict with surveys of young clusters. Here we report the analysis of a six times larger sample of microlensing events discovered during the years 2010-2015. Although our survey has very high sensitivity (detection efficiency) to short-timescale (1--2 days) microlensing events, we found no excess of events with timescales in this range, with a 95% upper limit on the frequency of Jupiter-mass free-floating or wide-orbit planets of 0.25 planet per main-sequence star. We detected a few possible ultrashort-timescale events (with timescales of less than 0.5 day), which may indicate the existence of Earth- and super-Earth-mass free-floating planets, as predicted by planet-formation theories

Discovery of a warm, dusty giant planet around HIP65426

Discovery of a warm, dusty giant planet around HIP65426

Authors:

Chauvin et al

Abstract:
The SHINE program is a large high-contrast near-infrared survey of 600 young, nearby stars. It is aimed at searching for and characterizing new planetary systems using VLT/SPHERE's unprecedented high-contrast and high-angular resolution imaging capabilities. It also intends at placing statistical constraints on the occurrence and orbital properties of the giant planet population at large orbits as a function of the stellar host mass and age to test planet formation theories. We use the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE to acquire high-constrast coronagraphic differential near-infrared images and spectra of the young A2 star HIP65426. It is a member of the ~17 Myr old Lower Centaurus-Crux association. At a separation of 830 mas (92 au projected) from the star, we detect a faint red companion. Multi-epoch observations confirm that it shares common proper motion with HIP65426. Spectro-photometric measurements extracted with IFS and IRDIS between 0.95 and 2.2um indicate a warm, dusty atmosphere characteristic of young low surface-gravity L5-L7 dwarfs. Hot-start evolutionary models predict a luminosity consistent with a 6-12 MJup, Teff=1300-1600 K and R=1.5 RJup giant planet. Finally, the comparison with Exo-REM and PHOENIX BT-Settl synthetic atmosphere models gives consistent effective temperatures but with slightly higher surface gravity solutions of log(g)=4.0-5.0 with smaller radii (1.0-1.3 RJup). Given its physical and spectral properties, HIP65426b occupies a rather unique placement in terms of age, mass and spectral-type among the currently known imaged planets. It represents a particularly interesting case to study the presence of clouds as a function of particle size, composition, and location in the atmosphere, to search for signatures of non-equilibrium chemistry, and finally to test the theory of planet formation and evolution.

Kepler-30: the Cesar of TTV variations

Kepler-30: the Cesar of TTV variations


Authors:

Panichi et al

Abstract:
We study the orbital architecture, physical character of planets, formation and long-term evolution of the Kepler-30 planetary system, detected and announced in 2012 by the KEPLER team. We show that it belongs to a particular class of very compact and quasi-resonant, yet long-term stable planetary systems. We re-analyzed light-curves of the host star spanning Q1-Q17 quarters. A huge variability of the Transit Timing Variations (TTV) exceeding 2 days is induced by a massive Jovian planet located between two Neptune-like companions. The innermost pair is near to the 2:1 mean motion resonance (MMR), and the outermost pair is close to the 19:8 MMR. Our re-analysis of photometric data allows us to constrain better than before the orbital elements, planets' radii and masses, which are 9.2±0.1, 536±5, and 23.7±1.3 Earth masses for Kepler-30b, Kepler-30c and Kepler-30d, respectively. The masses of the inner planets are determined within ∼1% uncertainty. We inferred the internal structures of the Kepler-30 planets and their bulk densities in a wide range from ∼0.19±0.01 g⋅cm−3 for Kepler-30d, ∼0.96±0.15 g⋅cm−3 for Kepler-30b, to ∼1.71±0.13 g⋅cm−3 for Jovian planet Kepler-30c, respectively. We attempt to explain the origin of this unique planetary system and a deviation of the orbits from exact MMRs by the planetary migration scenario. We anticipate that the Jupiter-mass planet plays an important role in determining the present dynamical state of this system.

ALMA Observes Exoplanet Formation Around V1247 Orionis

The quest to discover how planets found in the far reaches of the universe are born has taken a new, crucial twist.

A new study by an international team of scientists, led by Stefan Kraus from the University of Exeter, has given a fascinating new insight into one of the most respected theories of how planets are formed.

Young stars start out with a massive disk of gas and dust that over time, astronomers think, either diffuses away or coalesces into planets and asteroids.

However, scientists are still searching for a complete understanding of how these early formations come together to form asteroid-sized objects. One reason has been that drag in the disk produced by surrounding gas makes the grains move inward toward the star - which can in turn deplete the disk rapidly in a process known as "radial drift."

In the new research, the team use high powered telescopes to target the star V1247 Orionis -, a young, hot star surrounded by a dynamic ring of gas and dust.

The team produced a detailed image of the star and its surrounding dust disc, shown in two parts: a clearly defined central ring of matter and a more delicate crescent structure located further out.

The region between the ring and crescent, visible as a dark strip, is thought to be caused by a young planet carving its way through the disc. As the planet moves around in its orbit, its motion creates areas of high pressure on either side of its path, similar to how a ship creates bow waves as it cuts through water.

These areas of high pressure could become protective barriers around sites of planet formation; dust particles are trapped within them for millions of years, allowing them the time and space to clump together and grow.

link.

Redox States of Initial Atmospheres Outgassed on Rocky Planets and Planetesimals

Redox States of Initial Atmospheres Outgassed on Rocky Planets and Planetesimals

Authors:

Schaefer et al

Abstract:

The Earth and other rocky planets and planetesimals in the solar system formed through the mixing of materials from various radial locations in the solar nebula. This primordial material likely had a range of oxidation states as well as bulk compositions and volatile abundances. We investigate the oxygen fugacity produced by the outgassing of mixtures of solid meteoritic material, which approximate the primitive nebular materials. We find that the gas composition and oxygen fugacity of binary and ternary mixtures of meteoritic materials vary depending on the proportion of reduced versus oxidized material, and also find that mixtures using differentiated materials do not show the same oxygen fugacity trends as those using similarly reduced but undifferentiated materials. We also find that simply mixing the gases produced by individual meteoritic materials together does not correctly reproduce the gas composition or oxygen fugacity of the binary and ternary mixtures. We provide tabulated fits for the oxygen fugacities of all of the individual materials and binary mixtures that we investigate. These values may be useful in planetary formation models, models of volatile transport on planetesimals or meteorite parent bodies, or models of trace element partitioning during metal-silicate fractionation.

Lidov-Kozai Stability Regions in the Alpha Centauri system

Lidov-Kozai stability regions in the alpha Centauri system

Authors:

Guippone et al

Abstract:
The stability of planets in the alpha-Centauri AB stellar system has been studied extensively. However, most studies either focus on the orbital plane of the binary or consider inclined circular orbits.

Here, we numerically investigate the stability of a possible planet in the alpha-Centauri AB binary system for S-type orbits in an arbitrary spatial configuration. In particular, we focus on inclined orbits and explore the stability for different eccentricities and orientation angles.

We show that large stable and regular regions are present for very eccentric and inclined orbits, corresponding to libration in the Lidov-Kozai resonance. We additionally show that these extreme orbits can survive over the age of the system, despite the effect of tides. Our results remain qualitatively the same for any compact binary system.

Anthropics of Aluminum-26 Decay and Biological Homochirality

Anthropics of Aluminum-26 Decay and Biological Homochirality

Author:

Sandora

Abstract:

Results of recent experiment reinstate feasibility to the hypothesis that biomolecular homochirality originates from beta decay. Coupled with hints that this process occurred extraterrestrially suggests aluminum-26 as the most likely source. If true, then its appropriateness is highly dependent on the half-life and energy of this decay. Demanding that this mechanism hold places new constraints on the anthropically allowed range for multiple parameters, including the electron mass, difference between up and down quark masses, the fine structure constant, and the electroweak scale. These new constraints on particle masses are tighter than those previously found. However, one edge of the allowed region is nearly degenerate with an existing bound, which, using what is termed here as `the principle of noncoincident peril', is argued to be a strong indicator that the fine structure constant must be an environmental parameter in the multiverse.

Exoplanets and SETI

Exoplanets and SETI

Author:

Wright

Abstract:
The discovery of exoplanets has both focused and expanded the search for extraterrestrial intelligence. The consideration of Earth as an exoplanet, the knowledge of the orbital parameters of individual exoplanets, and our new understanding of the prevalence of exoplanets throughout the galaxy have all altered the search strategies of communication SETI efforts, by inspiring new "Schelling points" (i.e. optimal search strategies for beacons). Future efforts to characterize individual planets photometrically and spectroscopically, with imaging and via transit, will also allow for searches for a variety of technosignatures on their surfaces, in their atmospheres, and in orbit around them. In the near-term, searches for new planetary systems might even turn up free-floating megastructures.

Exoplanet Transits as the Foundation of an Interstellar Communications Network

Exoplanet Transits as the Foundation of an Interstellar Communications Network

Author:
Forgan

Abstract:

Two fundamental problems for extraterrestrial intelligences (ETIs) attempting to establish interstellar communication are timing and energy consumption. Humanity's study of exoplanets via their transit across the host star highlights a means of solving both problems. An ETI 'A' can communicate with ETI 'B' if B is observing transiting planets in A's star system, either by building structures to produce artificial transits observable by B, or by emitting signals at B during transit, at significantly lower energy consumption than typical electromagnetic transmission schemes.

This can produce a network of interconnected civilisations, establishing contact via observing each other's transits. Assuming that civilisations reside in a Galactic Habitable Zone (GHZ), I conduct Monte Carlo Realisation simulations of the establishment and growth of this network, and analyse its properties in the context of graph theory.

I find that at any instant, only a few civilisations are correctly aligned to communicate via transits. However, we should expect the true network to be cumulative, where a "handshake" connection at any time guarantees connection in the future via e.g. electromagnetic signals. In all our simulations, the cumulative network connects all civilisations together in a complete network. If civilisations share knowledge of their network connections, the network can be fully complete on timescales of order a hundred thousand years. Once established, this network can connect any two civilisations either directly, or via intermediate civilisations, with a path much less than the dimensions of the GHZ.

A Wideband Data Recorder System for the Robert C. Byrd Green Bank Telescope

The Breakthrough Listen Search for Intelligent Life: A Wideband Data Recorder System for the Robert C. Byrd Green Bank Telescope

Authors:

MacMahon et al

Abstract:
The Breakthrough Listen Initiative is undertaking a comprehensive search for radio and optical signatures from extraterrestrial civilizations. An integral component of the project is the design and implementation of wide-bandwidth data recorder and signal processing systems. The capabilities of these systems, particularly at radio frequencies, directly determine survey speed; further, given a fixed observing time and spectral coverage, they determine sensitivity as well. Here, we detail the Breakthrough Listen wide-bandwidth data recording system deployed at the 100-m aperture Robert C. Byrd Green Bank Telescope. The system digitizes up to 6 GHz of bandwidth at 8 bits for both polarizations, storing the resultant 24 GB/s of data to disk. This system is among the highest data rate baseband recording systems in use in radio astronomy. A future system expansion will double recording capacity, to achieve a total Nyquist bandwidth of 12 GHz in two polarizations. In this paper, we present details of the system architecture, along with salient configuration and disk-write optimizations used to achieve high-throughput data capture on commodity compute servers and consumer-class hard disk drives.

A Millimeter Continuum Size-Luminosity Relationship for Protoplanetary Disks

A Millimeter Continuum Size-Luminosity Relationship for Protoplanetary Disks

Authors:

Tripathi et al

Abstract:
We present a sub-arcsecond resolution survey of the 340 GHz dust continuum emission from 50 nearby protoplanetary disks, based on new and archival observations with the Submillimeter Array. The observed visibility data were modeled with a simple prescription for the radial surface brightness profile. The results were used to extract intuitive, empirical estimates of the emission "size" for each disk, Reff, defined as the radius that encircles a fixed fraction of the total continuum luminosity, Lmm. We find a significant correlation between the sizes and luminosities, such that Reff∝L0.5mm, providing a confirmation and quantitative characterization of a putative trend that was noted previously. This correlation suggests that these disks have roughly the same average surface brightness interior to their given effective radius, ~0.2 Jy arcsec−2 (or 8 K in brightness temperature). The same trend remains, but the 0.2dex of dispersion perpendicular to this relation essentially disappears, when we account for the irradiation environment of each disk with a crude approximation of the dust temperatures based on the stellar host luminosities. We consider two (not mutually exclusive) explanations for the origin of this size-luminosity relationship. Simple models of the growth and migration of disk solids can account for the observed trend for a reasonable range of initial conditions, but only on timescales that are much shorter than the nominal ages present in the sample. An alternative scenario invokes optically thick emission concentrated on unresolved scales, with filling factors of a few tens of percent, that are perhaps manifestations of localized particle traps.

Magnetic fields in circumstellar disks: The potential of Zeeman observations

Magnetic fields in circumstellar disks: The potential of Zeeman observations

Authors:

Brauer et al

Abstract:

Context.

Recent high angular resolution polarimetric continuum observations of circumstellar disks provide new insights into their magnetic field. However, direct constraints are limited to the plane of sky component of the magnetic field. Observations of Zeeman split spectral lines are a potential approach to enhance these insights by providing complementary information.

Aims.

We investigate which constraints for magnetic fields in circumstellar disks can be obtained from Zeeman observations of the 113 GHz CN lines. Furthermore, we analyze the requirements to perform these observations and their dependence on selected quantities.

Methods.

We simulate the Zeeman splitting with the radiative transfer (RT) code POLARIS (Reissl et al. 2016) extended by our Zeeman splitting RT extension ZRAD (Brauer et al. 2017), which is based on the line RT code Mol3D (Ober et al. 2015).

Results.

We find that Zeeman observations of the 113 GHz CN lines provide significant insights into the magnetic field of circumstellar disks. However, with the capabilities of recent and upcoming instrument/observatories, even spatially unresolved observations would be challenging. Nevertheless, these observations are feasible for the most massive disks with a strong magnetic field and high abundance of CN/H. The most restrictive quantity is the magnetic field strength, which should be at least in the order of ∼1 mG. In addition, the inclination of the disk should be around 60deg to preserve the ability to derive the line-of-sight (LOS) magnetic field strength and to obtain a sufficiently high circularly polarized flux.

A precessing Be disk as a possible model for occultation events in GX 304-1

A precessing Be disk as a possible model for occultation events in GX 304-1

Authors:

Kühnel et al

Abstract:

We report on the RXTE detection of a sudden increase in the absorption column density, NH, during the 2011 May outburst of GX 304-1. The NH increased up to ∼16×1022 atoms cm−2, which is a factor of 3-4 larger than what is usually measured during the outbursts of GX 304-1 as covered by RXTE. Additionally, an increase in the variability of the hardness ratio as calculated from the energy resolved RXTE-PCA light curves is measured during this time range. We interpret these facts as an occultation event of the neutron star by material in the line of sight. Using a simple 3D model of an inclined and precessing Be disk around the Be type companion, we are able to qualitatively explain the NH evolution over time. We are able to constrain the Be-disk density to be on the order of 10−11 g cm−3. Our model strengthens the idea of inclined Be disks as origin of double-peaked outbursts as the derived geometry allows accretion twice per orbit under certain conditions.

Magnetically Induced Disk Winds and Transport in the HL Tau Disk

Magnetically Induced Disk Winds and Transport in the HL Tau Disk

Authors:

Hasegawa et al

Abstract:
The mechanism of angular momentum transport in protoplanetary disks is fundamental to understand the distributions of gas and dust in the disks. The unprecedented, high spatial resolution ALMA observations taken toward HL Tau and subsequent radiative transfer modeling reveal that a high degree of dust settling is currently achieved at the outer part of the HL Tau disk. Previous observations however suggest a high disk accretion rate onto the central star. This configuration is not necessarily intuitive in the framework of the conventional viscous disk model, since efficient accretion generally requires a high level of turbulence, which can suppress dust settling considerably. We develop a simplified, semi-analytical disk model to examine under what condition these two properties can be realized in a single model. Recent, non-ideal MHD simulations are utilized to realistically model the angular momentum transport both radially via MHD turbulence and vertically via magnetically induced disk winds. We find that the HL Tau disk configuration can be reproduced well when disk winds are properly taken into account. While the resulting disk properties are likely consistent with other observational results, such an ideal situation can be established only if the plasma β at the disk midplane is β0≃2×104 under the assumption of steady accretion. Equivalently, the vertical magnetic flux at 100 au is about 0.2 mG. More detailed modeling is needed to fully identify the origin of the disk accretion and quantitatively examine plausible mechanisms behind the observed gap structures in the HL Tau disk.

Generation of inclined protoplanetary discs and misaligned planets through mass accretion I: Coplanar secondary discs

Generation of inclined protoplanetary discs and misaligned planets through mass accretion I: Coplanar secondary discs

Authors:

Xiang-Gruess et al

Abstract:

We study the three-dimensional evolution of a viscous protoplanetary disc which accretes gas material from a second protoplanetary disc during a close encounter in an embedded star cluster. The aim is to investigate the capability of the mass accretion scenario to generate strongly inclined gaseous discs which could later form misaligned planets. We use smoothed particle hydrodynamics to study mass transfer and disc inclination for passing stars and circumstellar discs with different masses. We explore different orbital configurations to find the parameter space which allows significant disc inclination generation. Thies et al. (2011) suggested that significant disc inclination and disc or planetary system shrinkage can generally be produced by the accretion of external gas material with a different angular momentum. We found that this condition can be fullfilled for a large range of gas mass and angular momentum. For all encounters, mass accretion from the secondary disc increases with decreasing mass of the secondary proto-star. Thus, higher disc inclinations can be attained for lower secondary stellar masses. Variations of the secondary disc’s orientation relative to the orbital plane can alter the disc evolution significantly. The results taken together show that mass accretion can change the three-dimensional disc orientation significantly resulting in strongly inclined discs. In combination with the gravitational interaction between the two star-disc systems, this scenario is relevant for explaining the formation of highly inclined discs which could later form misaligned planets.

Detecting Water's Dissociation in Protoplanetary Disks

The 1600 Angstrom Emission Bump in Protoplanetary Disks: A Spectral Signature of H2O Dissociation

Authors:

France et al

Abstract:

The FUV continuum spectrum of many accreting pre-main sequence stars, Classical T Tauri Stars (CTTSs), does not continue smoothly from the well-studied Balmer continuum emission in the NUV, suggesting that additional processes contribute to the short-wavelength emission in these objects. The most notable spectral feature in the FUV continuum of some CTTSs is a broad emission approximately centered at 1600~\AA, which has been referred to as the "1600 A Bump". The origin of this feature remains unclear. We have assembled archival FUV spectra of 37 disk-hosting systems observed by the {\it Hubble Space Telescope}. Clear 1600 A Bump emission is observed above the smooth, underlying 1100-1800 A continuum spectrum in 19/37 Classical T Tauri disks in the HST sample, with the detection rate in transition disks (8/8) being much higher than in primordial or non-transition sources (11/29). We describe a spectral deconvolution analysis to separate the Bump (spanning 1490~--~1690 A) from the underlying FUV continuum, finding an average Bump luminosity, L(Bump7 x 10^{29} erg s^{-1}. We find that the 1600 A Bump is characterized by a peak wavelength of 1598.6 +/- 3.3 A.
Contrary to previous studies, we find that this feature is inconsistent with models of H2 excited by electron-impact. We show that this Bump emits roughly 10-80% of the total fluorescent H2 luminosity for stars with well-defined Bump features. Energetically, this suggests that the carrier of the 1600 A Bump emission is powered by Ly-a photons. We argue that the most likely mechanism is Ly-a-driven dissociation of H2O in the inner disk, r < 2 AU. We demonstrate that non-thermally populated H2O fragments can qualitatively account for the observed emission (discrete and continuum), and find that the average Ly-a-driven H2O dissociation rate is 1.7x 10^{42} water molecules s^{-1}.

Emission lines in the atmosphere of the irradiated brown dwarf WD0137-349B

Emission lines in the atmosphere of the irradiated brown dwarf WD0137-349B

Authors:
Longstaff et al

Abstract:

We present new optical and near-infrared spectra of WD0137-349; a close white dwarf - brown dwarf non-interacting binary system with a period of ≈114 minutes. We have confirmed the presence of Hα emission and discovered He, Na, Mg, Si, K, Ca, Ti, and Fe emission lines originating from the brown dwarf atmosphere. This is the first brown dwarf atmosphere to have been observed to exhibit metal emission lines as a direct result of intense irradiation. The equivalent widths of many of these lines show a significant difference between the day and night sides of the brown dwarf. This is likely an indication that efficient heat redistribution may not be happening on this object, in agreement with models of hot Jupiter atmospheres. The Hα line strength variation shows a strong phase dependency as does the width. We have simulated the Ca II emission lines using a model that includes the brown dwarf Roche geometry and limb darkening and we estimate the mass ratio of the system to be 0.135±0.004. We also apply a gas-phase equilibrium code using a prescribed DRIFT-PHOENIX model to examine how the chemical composition of the brown dwarf upper atmosphere would change given an outward temperature increase, and discuss the possibility that this would induce a chromosphere above the brown dwarf atmosphere.

HH1165: The First Large-scale Herbig–Haro Jet Driven by a Proto-brown Dwarf

First Large-scale Herbig–Haro Jet Driven by a Proto-brown Dwarf

Authors:

Riaz et al

Abstract:

We report the discovery of a new Herbig–Haro jet, HH 1165, in SOAR narrow-band imaging of the vicinity of the σ Orionis cluster. HH 1165 shows a spectacular extended and collimated spatial structure, with a projected length of 0.26 pc, a bent C-shaped morphology, multiple knots, and fragmented bow shocks at the apparent ends of the flow. The Hα image shows a bright halo with a clumpy distribution of material seen around the driving source, and curved reflection nebulosity tracing the outflow cavities. The driving source of HH 1165 is a Class I proto-brown dwarf, Mayrit 1701117 (M1701117), with a total (dust+gas) mass of ~36 M Jup and a bolometric luminosity of ~0.1 L ⊙. High-resolution VLT/UVES spectra of M1701117 show a wealth of emission lines indicative of strong outflow and accretion activity. SOAR/Goodman low-resolution spectra along the jet axis show an asymmetrical morphology for HH 1165. We find a puzzling picture wherein the northwest part exhibits a classical HH jet running into a pre-dominantly neutral medium, while the southern part resembles an externally irradiated jet. The C-shaped bending in HH 1165 may be produced by the combined effects from the massive stars in the ionization front to the east, the σ Orionis core to the west, and the close proximity to the B2-type star HR 1950. HH 1165 shows all of the signatures to be considered as a scaled-down version of parsec-length HH jets, and can be termed as the first sub-stellar analog of a protostellar HH jet system.