- ID:
- ivo://CDS.VizieR/J/AJ/158/13
- Title:
- The first 300 stars observed by the GPIES
- Short Name:
- J/AJ/158/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a statistical analysis of the first 300 stars observed by the Gemini Planet Imager Exoplanet Survey. This subsample includes six detected planets and three brown dwarfs; from these detections and our contrast curves we infer the underlying distributions of substellar companions with respect to their mass, semimajor axis, and host stellar mass. We uncover a strong correlation between planet occurrence rate and host star mass, with stars M_*_>1.5 M_{sun}_ more likely to host planets with masses between 2 and 13 M_Jup_ and semimajor axes of 3-100 au at 99.92% confidence. We fit a double power-law model in planet mass (m) and semimajor axis (a) for planet populations around high-mass stars (M_*_>1.5 M_{sun}_) of the form d^2^N/(dm da){prop.to}m^{alpha}^{alpha}^{beta}^, finding {alpha}=-2.4+/-0.8 and {beta}=-2.0+/-0.5, and an integrated occurrence rate of 9_-4_^+5^% between 5-13 M_Jup_ and 10-100 au. A significantly lower occurrence rate is obtained for brown dwarfs around all stars, with 0.8_-0.5_^+0.8^% of stars hosting a brown dwarf companion between 13-80 M_Jup_ and 10-100 au. Brown dwarfs also appear to be distributed differently in mass and semimajor axis compared to giant planets; whereas giant planets follow a bottom-heavy mass distribution and favor smaller semimajor axes, brown dwarfs exhibit just the opposite behaviors. Comparing to studies of short-period giant planets from the radial velocity method, our results are consistent with a peak in occurrence of giant planets between ~1 and 10 au. We discuss how these trends, including the preference of giant planets for high-mass host stars, point to formation of giant planets by core/pebble accretion, and formation of brown dwarfs by gravitational instability.
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- ID:
- ivo://CDS.VizieR/J/AJ/156/286
- Title:
- The LEECH exoplanet imaging survey
- Short Name:
- J/AJ/156/286
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the largest L' (3.8 {mu}m) direct imaging survey for exoplanets to date, the Large Binocular Telescope Interferometer Exozodi Exoplanet Common Hunt (LEECH). We observed 98 stars with spectral types from B to M. Cool planets emit a larger share of their flux in L' compared to shorter wavelengths, affording LEECH an advantage in detecting low-mass, old, and cold-start giant planets. We emphasize proximity over youth in our target selection, probing physical separations smaller than other direct imaging surveys. For FGK stars, LEECH outperforms many previous studies, placing tighter constraints on the hot-start planet occurrence frequency interior to ~20 au. For less luminous, cold-start planets, LEECH provides the best constraints on giant-planet frequency interior to ~20 au around FGK stars. Direct imaging survey results depend sensitively on both the choice of evolutionary model (e.g., hot- or cold-start) and assumptions (explicit or implicit) about the shape of the underlying planet distribution, in particular its radial extent. Artificially low limits on the planet occurrence frequency can be derived when the shape of the planet distribution is assumed to extend to very large separations, well beyond typical protoplanetary dust-disk radii (~<50 au), and when hot-start models are used exclusively. We place a conservative upper limit on the planet occurrence frequency using cold-start models and planetary population distributions that do not extend beyond typical protoplanetary dust-disk radii. We find that ~<90% of FGK systems can host a 7-10 M_Jup_ planet from 5 to 50 au. This limit leaves open the possibility that planets in this range are common.
- ID:
- ivo://CDS.VizieR/J/ApJ/846/93
- Title:
- The multiplicity of M dwarfs in young moving groups
- Short Name:
- J/ApJ/846/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We image 104 newly identified low-mass (mostly M-dwarf) pre-main sequence (PMS) members of nearby young moving groups (YMGs) with Magellan Adaptive Optics (MagAO) and identify 27 stellar binaries with instantaneous projected separation as small as 40mas. Fifteen were previously unknown. The total number of multiple systems in this sample including spectroscopic and visual binaries from the literature is 36, giving a raw stellar multiplicity rate of at least 35_-4_^+5^% for this population. In the separation range of roughly 1-300au in which infrared AO imaging is most sensitive, the raw multiplicity rate is at least 24_-4_^+5^% for binaries resolved by the MagAO infrared camera (Clio). The M-star subsample of 87 stars yields a raw multiplicity of at least 30_-4_^+5^% over all separations, 21_-4_^+5^% for secondary companions resolved by Clio from 1 to 300au (23_-4_^+5^% for all known binaries in this separation range). A combined analysis with binaries discovered by the Search for Associations Containing Young stars shows that stellar multiplicity fraction as a function of mass over the range of 0.2 to 1.2M_{sun}_ appears to be linearly flat, in contrast to the field, where multiplicity increases with mass. After bias corrections are applied, the multiplicity of low-mass YMG members (0.2-0.6M_{sun}_) is in excess of the field. The overall multiplicity fraction is also consistent with being constant in age and across YMGs, which suggests that multiplicity rates for this mass range are largely set by 10Myr without appreciable evolution thereafter.
- ID:
- ivo://CDS.VizieR/J/AJ/156/49
- Title:
- The solar neighborhood. XLIII. New nearby stars
- Short Name:
- J/AJ/156/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a novel search of most of the southern sky for nearby red dwarfs having low proper motions, with specific emphasis on those with {mu}<0.18"/yr, the lower cutoff of Luyten's classic proper-motion catalog. We used a tightly constrained search of the SuperCOSMOS database and a suite of photometric distance relations for photographic BRI and 2MASS JHK_s_ magnitudes to estimate distances to more than 14 million red dwarf candidates. Here we discuss 29 stars in 26 systems estimated to be within 25 pc, all of which have {mu}<0.18"/yr, that we have investigated using milliarcsecond astrometry, VRI photometry, and low-resolution spectroscopy. In total, we present the first parallaxes of 20 star systems, 9 of which are within 25 pc. We have additionally identified 14 young M dwarfs, of which 3 are new members of the nearby young moving groups, and 72 new giants, including two new carbon stars. We also present the entire catalog of 1215 sources we have identified by this means.
- ID:
- ivo://CDS.VizieR/J/AJ/154/191
- Title:
- The solar neighborhood. XLII. New nearby subdwarfs
- Short Name:
- J/AJ/154/191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Parallaxes, proper motions, and optical photometry are presented for 51 systems consisting of 37 cool subdwarf and 14 additional high proper motion systems. Thirty-seven systems have parallaxes reported for the first time, 15 of which have proper motions of at least 1"/yr. The sample includes 22 newly identified cool subdwarfs within 100 pc, of which three are within 25 pc, and an additional five subdwarfs from 100 to 160 pc. Two systems-LSR 1610-0040 AB and LHS 440 AB-are close binaries exhibiting clear astrometric perturbations that will ultimately provide important masses for cool subdwarfs. We use the accurate parallaxes and proper motions provided here, combined with additional data from our program and others, to determine that effectively all nearby stars with tangential velocities greater than 200 km/s are subdwarfs. We compare a sample of 167 confirmed cool subdwarfs to nearby main sequence dwarfs and Pleiades members on an observational Hertzsprung-Russell diagram using M_V_ versus (V-K_s_) to map trends of age and metallicity. We find that subdwarfs are clearly separated for spectral types K5-M5, indicating that the low metallicities of subdwarfs set them apart in the H-R diagram for (V-K_s_)=3-6. We then apply the tangential velocity cutoff and the subdwarf region of the H-R diagram to stars with parallaxes from Gaia Data Release 1 and the MEarth Project to identify a total of 29 new nearby subdwarf candidates that fall clearly below the main sequence.
- ID:
- ivo://CDS.VizieR/J/AJ/155/265
- Title:
- The solar neighborhood. XLIV. RECONS discoveries
- Short Name:
- J/AJ/155/265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the 44 systems discovered to be within 10 pc of the Sun by the RECONS team, primarily via the long-term astrometry program at the CTIO/SMARTS 0.9 m that began in 1999. The systems-including 41 with red dwarf primaries, 2 white dwarfs, and 1 brown dwarf-have trigonometric parallaxes greater than 100 mas, with errors of 0.4-2.4 mas in all but one case. We provide updated astrometric, photometric (VRIJHK magnitudes), spectral type, and multiplicity information here. Among these are 14 systems that are new entries to the 10 pc sample, including the first parallaxes for 9 systems and new values for 5 systems that had previous parallaxes with errors greater than 10 mas or values placing them beyond 10 pc. We also provide new data for 22 systems known to lie within 10 pc and 9 systems reported to be closer than that horizon but for which new parallaxes place them further away, bringing the total to 75 systems. The 44 systems added by RECONS comprise one of every 7 systems known within 10 pc. We illustrate the evolution of the 10 pc sample from the 191 systems known when the final Yale Parallax Catalog was published in 1995 to the 317 systems known today. Even so close to the Sun, additional discoveries of white, red, and brown dwarfs are possible, both as primaries and secondaries, although we estimate that at least 90% of the stellar systems closer than 10 pc have now been identified.
- ID:
- ivo://CDS.VizieR/J/AJ/154/151
- Title:
- The solar neighborhood .XXXX. New young stars
- Short Name:
- J/AJ/154/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As a step toward completing and characterizing the census of the solar neighborhood, we present astrometric, photometric, and spectroscopic observations of 32 systems observed with the Cerro Tololo Inter-American Observatory 0.9 m and 1.5 m telescopes. Astrometry from the 0.9 m indicates that among the 17 systems that had no previous published trigonometric parallaxes, 14 are within 25 pc. In the full sample, nine systems have proper motions larger than 0.5"/yr, including 2MASS J02511490-0352459, which exceeds 2.0"/yr. VRI photometry from the 0.9 m and optical spectra from the 1.5 m indicate that the targets have V=11-22 mag and spectral types M3.0V-L3.0V. For 2MASS J23062928-0502285 (TRAPPIST-1), we present updated astrometry and photometric variability based on over 12 years of observations. Of the nine binaries in the sample, two promise mass determinations in the next decade: LHS 6167AB, an M4.5V system for which we present an accurate parallax placing the binary at 9.7 pc, and 2MASS J23515048-2537367AB, an M8.5V system at 21.1 pc for which we present the first evidence of an unseen, low-mass companion. Most importantly, Na I and K I gravity indicators, H{alpha} measurements, long-term photometric variability, locations on the H-R diagram, and kinematic assessments indicate that as many as 13 of the systems are young, including candidate members of young moving groups, with ages less than ~120 Myr.
- ID:
- ivo://CDS.VizieR/J/AJ/156/271
- Title:
- The stellar membership of the Taurus SFR
- Short Name:
- J/AJ/156/271
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The high-precision astrometry from the second data release of the Gaia mission (Cat. I/345) has made it possible to greatly improve the census of members of nearby clusters and associations. I have applied the Gaia data to the Taurus star-forming region, refining the sample of known members and identifying candidates for undiscovered members. The resulting samples of members and candidates provide the best constraints to date on the distribution of ages and the initial mass function (IMF) in Taurus. Several studies over the last 30 years have proposed the existence of a population of older stars (>~10 Myr) that is associated with the Taurus clouds. The data from Gaia demonstrate that such a population does not exist. Meanwhile, previous IMF estimates for small fields surrounding the Taurus aggregates have exhibited a surplus of K7-M0 stars (0.7-0.8 M_{sun}_) relative to star-forming clusters such as IC 348 and the Orion Nebula Cluster. However, that difference disappears when the new census of the entire region is considered, which should be complete for spectral types earlier than M6-M7 at A_J_<1. Thus, there is little variation in the stellar IMF across the 3-4 orders of magnitude in stellar density that are present in nearby star-forming regions. Finally, I note that the proper motions of two previously known members, KPNO 15 and 2MASS J04355209+2255039, indicate that they may have been ejected from the same location within the L1536 cloud ~7200 years ago.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/150
- Title:
- The Taurus-Auriga ecosystem. I.
- Short Name:
- J/ApJ/838/150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The census of Taurus-Auriga has been assembled over seven decades and inherited the biases and incompleteness of the input studies. The unusual shape of its inferred initial mass function (IMF) and the existence of isolated disk-bearing stars suggest that additional (likely disk-free) members remain to be discovered. We therefore have begun a global reassessment of the census of Taurus-Auriga that exploits new data and better definitions of youth and kinematic membership. As a first step, we reconsider the membership of all disk-free candidate members from the literature with spectral type >=F0, 3h50min<{alpha}5h40min, and 14{deg}<{delta}<34{deg}. We combine data from the literature with Keck/HIRES and UH88/SNIFS spectra to test the membership of these candidates using the positions in the Hertzsprung-Russel diagram, proper motions, radial velocities, H{alpha}, lithium, and surface gravity. We find 218 confirmed or likely Taurus members, 160 confirmed or likely interlopers, and only 18 that lack sufficient evidence to draw firm conclusions. A significant fraction of these stars (81/218=37%) are not included in the most recent canonical member lists. There are few additional members to the immediate vicinity of the molecular clouds, preserving the IMFs that have been deemed anomalous in past work. Many of the likely Taurus members are instead distributed broadly across the search area. When combined with the known disk hosts, our updated census reveals two regimes: a high-density population with a high disk fraction (indicative of youth) that broadly traces the molecular clouds, and a low-density population with low disk fraction (hence likely older) that most likely represents previous generations of star formation.
- ID:
- ivo://CDS.VizieR/J/ApJS/197/38
- Title:
- The WIRED survey. II.
- Short Name:
- J/ApJS/197/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the launch of the Wide-field Infrared Survey Explorer (WISE), a new era of detecting planetary debris and brown dwarfs (BDs) around white dwarfs (WDs) has begun with the WISE InfraRed Excesses around Degenerates (WIRED) Survey. The WIRED Survey is sensitive to substellar objects and dusty debris around WDs out to distances exceeding 100pc, well beyond the completeness level of local WDs. In this paper, we present a cross-correlation of the preliminary Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) WD catalog between the WISE, Two-Micron All Sky Survey (2MASS), UKIRT Infrared Deep Sky Survey (UKIDSS), and SDSS DR7 photometric catalogs. From ~18000 input targets, there are WISE detections comprising 344 "naked" WDs (detection of the WD photosphere only), 1020 candidate WD+M dwarf binaries, 42 candidate WD+BD systems, 52 candidate WD+dust disk systems, and 69 targets with indeterminate infrared excess. We classified all of the detected targets through spectral energy distribution model fitting of the merged optical, near-IR, and WISE photometry. Some of these detections could be the result of contaminating sources within the large (~6") WISE point-spread function; we make a preliminary estimate for the rates of contamination for our WD+BD and WD+disk candidates and provide notes for each target of interest.
