SCExAO AND GPI Y JH BAND PHOTOMETRY AND INTEGRAL FIELD SPECTROSCOPY OF THE YOUNG BROWN DWARF COMPANION TO HD 1160

SCExAO AND GPI Y JH BAND PHOTOMETRY AND INTEGRAL FIELD SPECTROSCOPY OF THE YOUNG BROWN DWARF COMPANION TO HD 1160

Authors:

Garcia et al

Abstract:
We present high signal-to-noise ratio, precise Y JH photometry and Y band (0.957–1.120 μm) spectroscopy of HD 1160 B, a young substellar companion discovered from the Gemini NICI Planet Finding Campaign using the Subaru Coronagraphic Extreme Adaptive Optics instrument and the Gemini Planet Imager. HD 1160 B has typical mid-M dwarf-like infrared colors and a spectral type of M5.5${}_{-0.5}^{+1.0}$, where the blue edge of our Y band spectrum rules out earlier spectral types. Atmospheric modeling suggests HD 1160 B has an effective temperature of 3000–3100 K, a surface gravity of log g = 4–4.5, a radius of 1.55 ± 0.10 R J, and a luminosity of log L/L ⊙ = −2.76 ± 0.05. Neither the primary's Hertzspring–Russell diagram position nor atmospheric modeling of HD 1160 B show evidence for a subsolar metallicity. Interpretation of the HD 1160 B spectroscopy depends on which stellar system components are used to estimate the age. Considering HD 1160 A, B and C jointly, we derive an age of 80–125 Myr, implying that HD 1160 B straddles the hydrogen-burning limit (70–90 M J). If we consider HD 1160 A alone, younger ages (20–125 Myr) and a brown dwarf-like mass (35–90 M J) are possible. Interferometric measurements of the primary, a precise Gaia parallax, and moderate-resolution spectroscopy can better constrain the system's age and how HD 1160 B fits within the context of (sub)stellar evolution.

System Architectures of PZ Tel and HD 1160 Revisited

First light of the VLT planet finder SPHERE - II. The physical properties and the architecture of the young systems PZ Tel and HD 1160 revisited

Authors:

Maire et al

Abstract:

Context.

The young systems PZ Tel and HD 1160, hosting known low-mass companions, were observed during the commissioning of the new planet finder SPHERE with several imaging and spectroscopic modes.

Aims.

We aim to refine the physical properties and architecture of both systems. Methods. We use SPHERE commissioning data and REM observations, as well as literature and unpublished data from VLT/SINFONI, VLT/NaCo, Gemini/NICI, and Keck/NIRC2.

Results.

We derive new photometry and confirm the nearly daily photometric variability of PZ Tel A. Using literature data spanning 38 yr, we show that the star also exhibits a long-term variability trend. The 0.63-3.8 mic SED of PZ Tel B allows us to revise its properties: spectral type M7+/-1, Teff=2700+/-100 K, log(g) less than 4.5 dex, log(L/L_Sun)=-2.51+/-0.10 dex, and mass 38-72 MJ. The 1-3.8 mic SED of HD 1160 B suggests a massive brown dwarf or a low-mass star with spectral type M5.5-7.0, Teff=3000+/-100 K, [M/H]=-0.5-0.0 dex, log(L/L_Sun)=-2.81+/-0.10 dex, and mass 39-168 MJ. We confirm the deceleration and high eccentricity (e greater than 0.66) of PZ Tel B. For e less than 0.9, the inclination, longitude of the ascending node, and time of periastron passage are well constrained. The system is seen close to an edge-on geometry. We reject other brown dwarf candidates outside 0.25" for both systems, and massive giant planets (greater than 4 MJ) outside 0.5" for the PZ Tel system. We also show that K1-K2 color can be used with YJH low-resolution spectra to identify young L-type companions, provided high photometric accuracy (less than 0.05 mag) is achieved.

Conclusions.

SPHERE opens new horizons in the study of young brown dwarfs and giant exoplanets thanks to high-contrast imaging capabilities at optical and near-infrared wavelengths, as well as high signal-to-noise spectroscopy in the near-infrared from low (R~30-50) to medium resolutions (R~350).