Are Niven Rings Around Pulsars Detectable?

Are the Dyson rings around pulsars detectable?

Authors:

Osmanov

Abstract:
In the previous paper (Osmanov 2016) (henceforth Paper-I) we have extended the idea of Freeman Dyson and have shown that a supercivilization has to use ring-like megastructures around pulsars instead of a spherical shell. In this work we reexamine the same problem in the observational context and we show that facilities of modern IR telescopes (VLTI and WISE) might efficiently monitor the nearby zone of the solar system and search for the IR Dyson-rings up to distances of the order of 0.2kpc, corresponding to the current highest achievable angular resolution, 0.001mas. In this case the total number of pulsars in the observationally reachable area is about 64±21. We show that pulsars from the distance of the order of ∼1kpc are still visible for WISE as point-like sources but in order to confirm that the object is the neutron star, one has to use the UV telescopes, which at this moment cannot provide enough sensitivity.

Highly Magnetized Pulsars may Produce Repeating Fast Radio Bursts When Encountering Asteroids

REPEATING FAST RADIO BURSTS FROM HIGHLY MAGNETIZED PULSARS TRAVELING THROUGH ASTEROID BELTS

Authors:

Dai et al

Abstract:

Very recently, Spitler et al. and Scholz et al. reported their detections of 16 additional bright bursts in the direction of the fast radio burst (FRB) 121102. This repeating FRB is inconsistent with all of the catastrophic event models put forward previously for hypothetically non-repeating FRBs. Here, we propose a different model, in which highly magnetized pulsars travel through the asteroid belts of other stars. We show that a repeating FRB could originate from such a pulsar encountering a large number of asteroids in the belt. During each pulsar-asteroid impact, an electric field induced outside of the asteroid has such a large component parallel to the stellar magnetic field that electrons are torn off the asteroidal surface and accelerated to ultra-relativistic energies instantaneously. The subsequent movement of these electrons along magnetic field lines will cause coherent curvature radiation, which can account for all of the properties of an FRB. In addition, this model can self-consistently explain the typical duration, luminosity, and repetitive rate of the 17 bursts of FRB 121102. The predicted occurrence rate of repeating FRB sources may imply that our model would be testable in the next few years.

SXP 214: AN X-RAY PULSAR IN THE SMALL MAGELLANIC CLOUD, CROSSING THE CIRCUMSTELLAR DISK OF THE COMPANION

SXP 214: AN X-RAY PULSAR IN THE SMALL MAGELLANIC CLOUD, CROSSING THE CIRCUMSTELLAR DISK OF THE COMPANION

Authors:

Hong et al

Abstract:

Located in the Small Magellanic Cloud (SMC), SXP 214 is an X-ray pulsar in a high mass X-ray binary system with a Be-star companion. A recent survey of the SMC under a Chandra X-ray Visionary program found that the source was in a transition when the X-ray flux was on a steady rise. The Lomb–Scargle periodogram revealed a pulse period of 211.49 ± 0.42 s, which is significantly (>5σ) shorter than the previous measurements made with XMM-Newton and RXTE. This implies that the system has gone through sudden spin-up episodes recently. The pulse profile shows a sharp eclipse-like feature with a modulation amplitude of >95%. The linear rise of the observed X-ray luminosity from lesssim2× to $7\times {10}^{35}$ erg s−1 is correlated with a steady softening of the X-ray spectrum, which can be described by the changes in the local absorption from N H ~ 1024 to lesssim1020 cm−2 for an absorbed power-law model. The soft X-ray emission below 2 keV was absent in the early part of the observation when only the pulsating hard X-ray component was observed, whereas at later times, both soft and hard X-ray components were observed to be pulsating. A likely explanation is that the neutron star was initially hidden in the circumstellar disk of the companion, and later came out of the disk with the accreted material that continued fueling the observed pulsation.

Circum Pulsar Disks Detected Around PSR 1931+24 & B0656+14

About detection of precessing circumpulsar disks

Author:

Grimani

Abstract:

Detections of circumpulsar disks and planetary systems through electromagnetic observations appear quite rare. In the case of PSR 1931+24 and B0656+14, the hypothesis of a precessing disk penetrating the pulsar light cylinder is found consistent with radio and gamma observations from these stars. Disk self-occultation and precession may affect electromagnetic measurements. We investigate here under which conditions gravitational waves generated by circumpulsar disk precession may be detected by the proposed second generation space interferometers DECIGO (DECI-hertz Interferometer Gravitational Wave Observatory) and BBO (Big Bang Observer). The characteristics of circumpulsar detectable precessing disks are estimated as a function of distance from the Solar System. Speculations on detection rates are presented.

Do asteroids evaporate near pulsars?

Do asteroids evaporate near pulsars? Induction heating by pulsar waves revisited

Authors:

Kotera et al

Abstract:

We investigate the evaporation of close-by pulsar companions, such as planets, asteroids, and white dwarfs, by induction heating. Assuming that the outflow energy is dominated by a Poynting flux (or pulsar wave) at the location of the companions, we calculate their evaporation timescales, by applying the Mie theory. Depending on the size of the companion compared to the incident electromagnetic wavelength, the heating regime varies and can lead to a total evaporation of the companion. In particular, we find that inductive heating is mostly inefficient for small pulsar companions, although it is generally considered the dominant process. Small objects like asteroids can survive induction heating for 104years at distances as small as 1R⊙ from the neutron star. For degenerate companions, induction heating cannot lead to evaporation and another source of heating (likely by kinetic energy of the pulsar wind) has to be considered. It was recently proposed that bodies orbiting pulsars are the cause of fast radio bursts; the present results explain how those bodies can survive in the pulsar's highly energetic environment.

Limits on Exoplanet Formation Around Pulsars

Limits on Planet Formation Around Young Pulsars and Implications for Supernova Fallback Disks

Authors:

Kerr et al

Abstract:

We have searched a sample of 151 young, energetic pulsars for periodic variation in pulse time-of-arrival arising from the influence of planetary companions. We are sensitive to objects with masses two orders of magnitude lower than those detectable with optical transit timing, but we find no compelling evidence for pulsar planets. For the older pulsars most likely to host planets, we can rule out Mercury analogues in one third of our sample and planets with masses greater 0.4M⊕ and periods Pb less than 1 yr in all but 5% of such systems. If pulsar planets form primarily from supernova fallback disks, these limits imply that such disks do not form, are confined to less than 0.1 AU radii, are disrupted, or form planets more slowly (greater than 2 Myr) than their protoplanetary counterparts.

Sudden Spin Slowing in 2005 of Pulsar PSR J0738-4042 Probably due to Asteroid Impacts

Reduced spin-down rate of PSR J0738-4042 explained as due to an asteroid disruption event

Authors:

Yu et al

Abstract:

Long term observations by Brook et al. reveal that the derivative of rotational frequency of PSR J0738-4042 changed abruptly in 2005. Originally, the spin-down rate was relatively stable, with the rotational frequency derivative of −1.14×10−14 s−2. After September 2005, the derivative began to rise up. About 1000 days later, it arrived at another relatively stable value of about −0.98×10−14 s−2, indicating that the pulsar is spinning-down relatively slowly. To explain the observed spin-down rate change, we resort to an asteroid disrupted by PSR J0738-4042. In our model, the orbital angular momentum of the asteroid is assumed to be parallel to that of the rotating pulsar, so that the pronounced reduction in the spin-down rate can be naturally explained as due to the transfer of the angular momentum from the disrupted material to the central pulsar. The derived magnetospheric radius is about 4.0×109 cm, which is smaller than the tidal disruption radius (4.9×1010 cm). Our model is self-consistent. It is shown that the variability of the spin-down rate of PSR J0738-4042 can be quantitatively accounted for by the accretion from the asteroid disrupted by the central pulsar.

Detecting Circumstellar Disks Around Pulsars

Detection of precessing circumpulsar disks

Author:

Grimani

Abstract:

Experimental evidences indicate that formations of disks and planetary systems around pulsars are allowed. Unfortunately, direct detections through electromagnetic observations appear to be quite rare. In the case of PSR 1931+24, the hypothesis of a rigid precessing disk penetrating the pulsar light cylinder is found consistent with radio transient observations from this star. Disk self-occultation and precession may limit electromagnetic observations. Conversely, we show here that gravitational waves generated by disk precessing near the light cylinder of young and middle aged pulsars would be detected by future space interferometers with sensitivities like those expected for DECIGO (DECI-hertz Interferometer Gravitational Wave Observatory) and BBO (Big Bang Observer). The characteristics of circumpulsar detectable precessing disks are estimated as a function of distance from the Solar System. Speculations on upper limits to detection rates are presented.

Circumstellar Disks Around Pulsars

Searching for debris disks around isolated pulsars

Author:

Wang

Abstract:

Different pieces of observational evidence suggest the existence of disks around isolated neutron stars. Such disks could be formed from supernova fallback when neutron stars are born in core-collapse supernova explosions. Efforts have been made to search for disks around different classes of pulsars, which include millisecond pulsars, young neutron star classes (magnetars, central compact objects, and X-ray dim isolated neutron stars), and regular radio pulsars. We review the main results from observations at wavelengths of from optical to sub-millimeter/millimeter.