720 research outputs found
Identification of WISE J000100.45+065259.6 as an M8.5+T5 Spectral Binary Candidate
[not part of RNAAS note] We report the discovery of WISE J000100.45+065259.6
as a very low mass star/brown dwarf spectral binary candidate, on the basis of
low resolution near-infrared spectroscopy obtained with IRTF/SpeX.
Decomposition of the spectrum indicates component types of M8.5+T5 with a
predicted = 3.5. As the majority of confirmed spectral binary
candidates to date are very closely-separated systems ( 3 AU;
15~yr), this source may provide mass measurements across the
hydrogen burning limit within the decade.Comment: 3 pages, 1 figure, accepted to Research Notes of the AA
Single and Composite Hot Subdwarf Stars in the Light of 2MASS Photometry
Utilizing the Two Micron All Sky Survey (2MASS) Second Incremental Data
Release Catalog, we have retrieved near-IR magnitudes for several hundred hot
subdwarfs (sdO and sdB stars) drawn from the "Catalogue of Spectroscopically
Identified Hot Subdwarfs" (Kilkenny, Heber, & Drilling 1988, 1992). This sample
size greatly exceeds that of previous studies of hot subdwarfs. Examining 2MASS
photometry alone or in combination with visual photometry (Johnson BV or
Stromgren uvby) available in the literature, we show that it is possible to
identify hot subdwarf stars that exhibit atypically red IR colors that can be
attributed to the presence of an unresolved late type companion. Utilizing this
large sample, we attempt for the first time to define an approximately volume
limited sample of hot subdwarfs. We discuss the considerations, biases, and
difficulties in defining such a sample.
We find that, of the hot subdwarfs in Kilkenny et al., about 40% in a
magnitude limited sample have colors that are consistent with the presence of
an unresolved late type companion. Binary stars are over-represented in a
magnitude limited sample. In an approximately volume limited sample the
fraction of composite-color binaries is about 30%.Comment: to appear in Sept 2003 AJ, 41 pages total, 12 figures, 2 tables are
truncated (full tables to appear in electronic journal or available by
request
Assessing the C/O Ratio Formation Diagnostic: A Potential Trend with Companion Mass
The carbon-to-oxygen (C/O) ratio in an exoplanet atmosphere has been
suggested as a potential diagnostic of planet formation. Now that a number of
exoplanets have measured C/O ratios, it is possible to examine this diagnostic
at a population level. Here, we present an analysis of currently measured C/O
ratios of directly imaged and transit/eclipse planets. First, we derive
atmospheric parameters for the substellar companion HD 284149 b using data that
were taken with the OSIRIS integral field spectrograph at the W.M. Keck
Observatory and report two non-detections from our ongoing imaging spectroscopy
survey of exoplanetary atmospheres with Keck/OSIRIS. We find an effective
temperature of ~K, with a range of 2291--2624~K, , with a range of 4.38--4.91, and [M/H] = 0.37, with a range of
0.10--0.55. These values are in agreement with previous studies done by
Bonavita et al. (2014, 2017). We derive a C/O of 0.589 for
HD 284149 b. We then add this measurement to the growing list of C/O ratios for
directly imaged planets from the literature, and compare them with those
available from a sample of transit/eclipse planets. There is a trend in C/O
ratio with companion mass (M), with a break seen around 4
M. We run a Kolmogorov-Smirnov and an Anderson-Darling test on
planets above and below this mass boundary, and find that they are two distinct
populations. This could be additional evidence of two distinct populations
possibly having two different formation pathways, with companion mass as a
primary indicator of most likely formation scenario.Comment: 20 pages, 12 figure
Radial velocities and kinematic ages of nearby T dwarfs from Keck/NIRSPEC high-resolution spectroscopy
Stars and planetary system
The Perkins INfrared Exosatellite Survey (PINES) II. Transit Candidates and Implications for Planet Occurrence around L and T Dwarfs
We describe a new transit detection algorithm designed to detect single
transit events in discontinuous Perkins INfrared Exosatellite Survey (PINES)
observations of L and T dwarfs. We use this algorithm to search for transits in
131 PINES light curves and identify two transit candidates: 2MASS
J18212815+1414010 (2MASS J1821+1414) and 2MASS J08350622+1953050 (2MASS
J0835+1953). We disfavor 2MASS J1821+1414 as a genuine transit candidate due to
the known variability properties of the source. We cannot rule out the
planetary nature of 2MASS J0835+1953's candidate event and perform follow-up
observations in an attempt to recover a second transit. A repeat event has yet
to be observed, but these observations suggest that target variability is an
unlikely cause of the candidate transit. We perform a Markov chain Monte Carlo
simulation of the light curve and estimate a planet radius ranging from
to , depending on the
host's age. Finally, we perform an injection and recovery simulation on our
light curve sample. We inject planets into our data using measured M dwarf
planet occurrence rates and attempt to recover them using our transit search
algorithm. Our detection rates suggest that, assuming M dwarf planet occurrence
rates, we should have roughly a 1 chance of detecting a candidate that
could cause the transit depth we observe for 2MASS J0835+1953. If 2MASS
J0835+1953 b is confirmed, it would suggest an enhancement in the occurrence of
short-period planets around L and T dwarfs in comparison to M dwarfs, which
would challenge predictions from planet formation models.Comment: 23 pages, 15 figures, accepted to A
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