283 research outputs found
Subaru/SCExAO First-light Direct Imaging of a Young Debris Disk around HD 36546
We present H-band scattered light imaging of a bright debris disk around the A0 star HD 36546 obtained from the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system with data recorded by the HiCIAO camera using the vector vortex coronagraph. SCExAO traces the disk from r ~ 0.”3 to r ~ 1'' (34–114 au). The disk is oriented in a near east–west direction (PA ~ 75°), is inclined by i ~ 70°–75°, and is strongly forward-scattering (g > 0.5). It is an extended disk rather than a sharp ring; a second, diffuse dust population extends from the disk's eastern side. While HD 36546 intrinsic properties are consistent with a wide age range (t ~ 1–250 Myr), its kinematics and analysis of coeval stars suggest a young age (3–10 Myr) and a possible connection to Taurus-Auriga's star formation history. SCExAO's planet-to-star contrast ratios are comparable to the first-light Gemini Planet Imager contrasts; for an age of 10 Myr, we rule out planets with masses comparable to HR 8799 b beyond a projected separation of 23 au. A massive icy planetesimal disk or an unseen super-Jovian planet at r > 20 au may explain the disk's visibility. The HD 36546 debris disk may be the youngest debris disk yet imaged, is the first newly identified object from the now-operational SCExAO extreme AO system, is ideally suited for spectroscopic follow-up with SCExAO/CHARIS in 2017, and may be a key probe of icy planet formation and planet–disk interactions
Subaru/SCExAO First-light Direct Imaging of a Young Debris Disk around HD 36546
We present H-band scattered light imaging of a bright debris disk around the A0 star HD 36546 obtained from the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system with data recorded by the HiCIAO camera using the vector vortex coronagraph. SCExAO traces the disk from r ~ 0.”3 to r ~ 1'' (34–114 au). The disk is oriented in a near east–west direction (PA ~ 75°), is inclined by i ~ 70°–75°, and is strongly forward-scattering (g > 0.5). It is an extended disk rather than a sharp ring; a second, diffuse dust population extends from the disk's eastern side. While HD 36546 intrinsic properties are consistent with a wide age range (t ~ 1–250 Myr), its kinematics and analysis of coeval stars suggest a young age (3–10 Myr) and a possible connection to Taurus-Auriga's star formation history. SCExAO's planet-to-star contrast ratios are comparable to the first-light Gemini Planet Imager contrasts; for an age of 10 Myr, we rule out planets with masses comparable to HR 8799 b beyond a projected separation of 23 au. A massive icy planetesimal disk or an unseen super-Jovian planet at r > 20 au may explain the disk's visibility. The HD 36546 debris disk may be the youngest debris disk yet imaged, is the first newly identified object from the now-operational SCExAO extreme AO system, is ideally suited for spectroscopic follow-up with SCExAO/CHARIS in 2017, and may be a key probe of icy planet formation and planet–disk interactions
A substellar companion to Pleiades HII 3441
We find a new substellar companion to the Pleiades member star, Pleiades HII 3441, using the Subaru telescope with adaptive optics. The discovery is made as part of the high-contrast imaging survey to search for planetary-mass and substellar companions in the Pleiades and young moving groups. The companion has a projected separation of 0.”49 ± 0.”02 (66 ± 2 au) and a mass of 68 ± 5 M_J based on three observations in the J-, H-, and Ks-bands. The spectral type is estimated to be M7 (∼2700 K), and thus no methane absorption is detected in the H band. Our Pleiades observations result in the detection of two substellar companions including one previously reported among 20 observed Pleiades stars, and indicate that the fraction of substellar companions in the Pleiades is about 10.0^(+26.1)_(−8.8)% This is consistent with multiplicity studies of both the Pleiades stars and other open clusters
The young binary HD 102077: Orbit, spectral type, kinematics, and moving group membership
The K-type binary star HD 102077 was proposed as a candidate member of the TW
Hydrae Association (TWA) which is a young (5-15 Myr) moving group in close
proximity (~50 pc) to the solar system. The aim of this work is to verify this
hypothesis by different means. We first combine diffraction-limited
observations from the ESO NTT 3.5m telescope in SDSS-i' and -z' passbands and
ESO 3.6m telescope in H-band with literature data to obtain a new, amended
orbit fit, estimate the spectral types of both components, and reanalyse the
Hipparcos parallax and proper motion taking the orbital motion into account.
Moreover, we use two high-resolution spectra of HD 102077 obtained with the
fibre-fed optical echelle spectrograph FEROS at the MPG/ESO 2.2m telescope to
determine the radial velocity and the lithium equivalent width of the system.
The trajectory of HD 102077 is well constrained and we derive a total system
mass of M and a semi-major axis of AU. From the i'-z' colours we infer an integrated spectral type of K2V,
and individual spectral types of K0 +/- 1 and K5 +/- 1. The radial velocity
corrected for the orbital motion of the system is km/s. Even
though the parallax determination from the Hipparcos data is not influenced by
the orbital motion, the proper motion changes to mas/yr and mas/yr. With
the resultant space motion, the probability of HD 102077 being a member of TWA
is less than 1%. Furthermore, the lithium equivalent width of m\AA
is consistent with an age between 30 Myr and 120 Myr and thus older than
the predicted age of TWA. In conclusion, HD 102077's age, galactic space
motion, and position do not fit TWA or any other young moving group
Scaling K2. I. Revised Parameters for 222,088 K2 Stars and a K2 Planet Radius Valley at 1.9 R_⊕
Previous measurements of stellar properties for K2 stars in the Ecliptic Plane Input Catalog largely relied on photometry and proper motion measurements, with some added information from available spectra and parallaxes. Combining Gaia DR2 distances with spectroscopic measurements of effective temperatures, surface gravities, and metallicities from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) DR5, we computed updated stellar radii and masses for 26,838 K2 stars. For 195,250 targets without a LAMOST spectrum, we derived stellar parameters using random forest regression on photometric colors trained on the LAMOST sample. In total, we measured spectral types, effective temperatures, surface gravities, metallicities, radii, and masses for 222,088 A, F, G, K, and M-type K2 stars. With these new stellar radii, we performed a simple reanalysis of 299 confirmed and 517 candidate K2 planet radii from Campaigns 1–13, elucidating a distinct planet radius valley around 1.9 R_⊕, a feature thus far only conclusively identified with Kepler planets, and tentatively identified with K2 planets. These updated stellar parameters are a crucial step in the process toward computing K2 planet occurrence rates
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