- ID:
- ivo://CDS.VizieR/J/AJ/154/134
- Title:
- Planetary-mass brown dwarfs in the Taurus SFR
- Short Name:
- J/AJ/154/134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the initial results from a survey for planetary-mass brown dwarfs in the Taurus star-forming region. We have identified brown dwarf candidates in Taurus using proper motions and photometry from several ground- and space- based facilities. Through spectroscopy of some of the more promising candidates, we have found 18 new members of Taurus. They have spectral types ranging from mid-M to early-L, and they include the four faintest known members in extinction-corrected K_s_, which should have masses as low as ~4-5 M_Jup_ according to evolutionary models. Two of the coolest new members (M9.25, M9.5) have mid-IR excesses that indicate the presence of disks. Two fainter objects with types of M9-L2 and M9-L3 also have red mid-IR colors relative to photospheres at =<L0, but since the photospheric colors are poorly defined at >L0, it is unclear whether they have excesses from disks. We also have obtained spectra of candidate members of the IC 348 and NGC 1333 clusters in Perseus that were identified by Luhman et al. Eight candidates are found to be probable members, three of which are among the faintest and least-massive known members of the clusters (~5 M_Jup_).
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/705/1226
- Title:
- Planet-bearing stars in Spitzer
- Short Name:
- J/ApJ/705/1226
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the MIPS camera on the Spitzer Space Telescope, we have searched for debris disks around 104 stars known from radial velocity studies to have one or more planets. Combining this new data with 42 already published observations of planet-bearing stars, we find that 14 of the 146 systems have IR excess at 24 and/or 70um. Only one star, HD 69830, has IR excess exclusively at 24um, indicative of warm dust in the inner system analogous to that produced by collisions in the solar system's asteroid belt. For the other 13 stars with IR excess the emission is stronger at 70um, consistent with cool dust (<100K) located beyond 10AU, well outside of the orbital location of the known planets.
- ID:
- ivo://CDS.VizieR/J/ApJ/814/130
- Title:
- Planet occurrence rates calculated for KOIs
- Short Name:
- J/ApJ/814/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Trends in the planet population with host star mass provide an avenue to constrain planet formation theories. We derive the planet radius distribution function for Kepler stars of different spectral types, sampling a range in host star masses. We find that M dwarf stars have 3.5 times more small planets (1.0-2.8R_{Earth}_) than main-sequence FGK stars, but two times fewer Neptune-sized and larger (>2.8R_{Earth}_) planets. We find no systematic trend in the planet size distribution between spectral types F, G, and K to explain the increasing occurrence rates. Taking into account the mass-radius relationship and heavy-element mass of observed exoplanets, and assuming those are independent of spectral type, we derive the inventory of the heavy-element mass locked up in exoplanets at short orbits. The overall higher planet occurrence rates around M stars are not consistent with the redistribution of the same mass into more, smaller planets. At the orbital periods and planet radii where Kepler observations are complete for all spectral types, the average heavy-element mass locked up in exoplanets increases roughly inversely with stellar mass from 4M_{Earth}_ in F stars to 5M_{Earth}_in G and K stars to 7M_{Earth}_ in M stars. This trend stands in stark contrast with observed protoplanetary disk masses that decrease toward lower mass stars, and provides a challenge for current planet formation models. Neither models of in situ formation nor migration of fully formed planets are consistent with these results. Instead, these results are indicative of large-scale inward migration of planetary building blocks --either through type-I migration or radial drift of dust grains-- that is more efficient for lower mass stars, but does not result in significantly larger or smaller planets.
- ID:
- ivo://CDS.VizieR/J/AJ/154/46
- Title:
- Proper motions and photometry for members of Cha I
- Short Name:
- J/AJ/154/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a search for planetary-mass brown dwarfs in the Chamaeleon I star-forming region using proper motions and photometry measured from optical and infrared images from the Spitzer Space Telescope, the Hubble Space Telescope, and ground-based facilities. Through near-IR spectroscopy at Gemini Observatory, we have confirmed six of the candidates as new late-type members of Chamaeleon I ({>=}M8). One of these objects, ChaJ11110675-7636030, has the faintest extinction-corrected M_K_ among known members, which corresponds to a mass of 3-6M_Jup_ according to evolutionary models. That object and two other new members have redder mid-IR colors than young photospheres at {<=}M9.5, which may indicate the presence of disks. However, since those objects may be later than M9.5 and the mid-IR colors of young photospheres are ill-defined at those types, we cannot determine conclusively whether color excesses from disks are present. If ChaJ11110675-7636030 does have a disk, it would be a contender for the least-massive known brown dwarf with a disk. Since the new brown dwarfs that we have found extend below our completeness limit of 6-10M_Jup_, deeper observations are needed to measure the minimum mass of the initial mass function in Chamaeleon I.
- ID:
- ivo://CDS.VizieR/J/AJ/144/129
- Title:
- Properties of 83 known stellar SiO maser sources
- Short Name:
- J/AJ/144/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out simultaneous observations of four maser lines, SiO v=1,2, ^29^SiO v=0,J=1-0, and H_2_O 6_16_-5_23_, toward 83 known SiO maser sources without H_2_O maser detections using the Korean VLBI Network single dish telescopes. Both SiO and H_2_O masers were detected from 14 sources, resulting in a detection rate of 16.9%. H_2_O maser emission without SiO maser emission was detected from one source. Therefore, H_2_O maser emission was newly detected from 15 sources. SiO maser emission without H_2_O detection was detected from 55 sources, which gives a total SiO maser detection rate of 83.1% when including sources that have both SiO and H_2_O maser emission detected. SiO v=2 maser emission was detected from nine sources without v=1 maser detection. The SiO v=2 maser sources without the v=1 maser detections need to be investigated, with a large number of v=2 only maser sources related to the development of dust shells and their evolutionary sequence from asymptotic giant branch (AGB) to post-AGB stars. The average values of the peak and integrated antenna temperature ratios of H_2_O to SiO masers are 0.44 and 0.28 in the 14 sources that have both SiO and H_2_O detections. Observational characteristics of several individual sources are noted and the dependence of the different maser intensity ratios on the stellar phase is discussed. In addition, the observational results of SiO and H_2_O masers are discussed in IRAS two-color diagrams.
- ID:
- ivo://CDS.VizieR/J/AJ/156/213
- Title:
- Properties of N2K stars & new gas giant companions
- Short Name:
- J/AJ/156/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The N2K planet search program was designed to exploit the planet-metallicity correlation by searching for gas giant planets orbiting metal-rich stars. Here, we present the radial velocity measurements for 378 N2K target stars that were observed with the HIRES spectrograph at Keck Observatory between 2004 and 2017. With this data set, we announce the discovery of six new gas giant exoplanets: a double-planet system orbiting HD 148164 (Msini of 1.23 and 5.16 M_JUP_) and single planet detections around HD 55696 (Msini=3.87 M_JUP_), HD 98736 (Msini=2.33 M_JUP_), HD 203473 (Msini=7.8 M_JUP_), and HD 211810 (Msini=0.67 M_JUP_). These gas giant companions have orbital semimajor axes between 1.0 and 6.2 au and eccentricities ranging from 0.13 to 0.71. We also report evidence for three gravitationally bound companions with Msini between 20 and 30 M_JUP_, placing them in the mass range of brown dwarfs, around HD 148284, HD 214823, and HD 217850, and four low-mass stellar companions orbiting HD 3404, HD 24505, HD 98630, and HD 103459. In addition, we present updated orbital parameters for 42 previously announced planets. We also report a nondetection of the putative companion HD 73256 b. Finally, we highlight the most promising candidates for direct imaging and astrometric detection, and we find that many hot Jupiters from our sample could be detectable by state-of-the-art telescopes such as Gaia.
- ID:
- ivo://CDS.VizieR/J/AJ/155/207
- Title:
- Properties of yellow supergiant stars in the SMC
- Short Name:
- J/AJ/155/207
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We recently discovered a yellow supergiant (YSG) in the Small Magellanic Cloud (SMC) with a heliocentric radial velocity of ~300 km/s, which is much larger than expected for a star at its location in the SMC. This is the first runaway YSG ever discovered and only the second evolved runaway star discovered in a galaxy other than the Milky Way. We classify the star as G5-8 I and use de-reddened broad-band colors with model atmospheres to determine an effective temperature of 4700+/-250 K, consistent with what is expected from its spectral type. The star's luminosity is then log L/L_{sun}_~4.2~0.1, consistent with it being a ~30 Myr 9 M_{sun}_ star according to the Geneva evolution models. The star is currently located in the outer portion of the SMC's body, but if the star's transverse peculiar velocity is similar to its peculiar radial velocity, in 10 Myr the star would have moved 1.6{deg} across the disk of the SMC and could easily have been born in one of the SMC's star-forming regions. Based on its large radial velocity, we suggest it originated in a binary system where the primary exploded as a supernovae, thus flinging the runaway star out into space. Such stars may provide an important mechanism for the dispersal of heavier elements in galaxies given the large percentage of massive stars that are runaways. In the future, we hope to look into additional evolved runaway stars that were discovered as part of our other past surveys.
- ID:
- ivo://CDS.VizieR/J/ApJ/847/31
- Title:
- Protoplanetary disk data in Cha I and Lupus
- Short Name:
- J/ApJ/847/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we investigate the relation between disk mass and mass accretion rate to constrain the mechanism of angular momentum transport in protoplanetary disks. We find a correlation between dust disk mass and mass accretion rate in Chamaeleon I with a slope that is close to linear, similar to the one recently identified in Lupus. We investigate the effect of stellar mass and find that the intrinsic scatter around the best-fit M_dust_-M_*_ and dM_acc_/dt-M_*_ relations is uncorrelated. We simulate synthetic observations of an ensemble of evolving disks using a Monte Carlo approach and find that disks with a constant {alpha} viscosity can fit the observed relations between dust mass, mass accretion rate, and stellar mass but overpredict the strength of the correlation between disk mass and mass accretion rate when using standard initial conditions. We find two possible solutions. In the first one, the observed scatter in M_dust_ and dM_acc_/dt is not primordial, but arises from additional physical processes or uncertainties in estimating the disk gas mass. Most likely grain growth and radial drift affect the observable dust mass, while variability on large timescales affects the mass accretion rates. In the second scenario, the observed scatter is primordial, but disks have not evolved substantially at the age of Lupus and Chamaeleon I owing to a low viscosity or a large initial disk radius. More accurate estimates of the disk mass and gas disk sizes in a large sample of protoplanetary disks, through either direct observations of the gas or spatially resolved multiwavelength observations of the dust with ALMA, are needed to discriminate between both scenarios or to constrain alternative angular momentum transport mechanisms such as MHD disk winds.
- ID:
- ivo://CDS.VizieR/J/ApJ/858/41
- Title:
- PS1 proper-motion survey for brown dwarfs. I. Taurus
- Short Name:
- J/ApJ/858/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We are conducting a proper-motion survey for young brown dwarfs in the Taurus-Auriga molecular cloud based on the Pan-STARRS1 3{pi} Survey. Our search uses multi-band photometry and astrometry to select candidates, and is wider (370deg^2^) and deeper (down to ~3M_Jup_) than previous searches. We present here our search methods and spectroscopic follow-up of our high-priority candidates. Since extinction complicates spectral classification, we have developed a new approach using low-resolution (R~100) near-infrared spectra to quantify reddening-free spectral types, extinctions, and gravity classifications for mid-M to late-L ultracool dwarfs (<=100-3M_Jup_ in Taurus). We have discovered 25 low-gravity (VL-G) and the first 11 intermediate-gravity (INT-G) substellar (M6-L1) members of Taurus, constituting the largest single increase of Taurus brown dwarfs to date. We have also discovered 1 new Pleiades member and 13 new members of the Perseus OB2 association, including a candidate very wide separation (58kau) binary. We homogeneously reclassify the spectral types and extinctions of all previously known Taurus brown dwarfs. Altogether our discoveries have thus far increased the substellar census in Taurus by ~40% and added three more L-type members (<~5-10M_Jup_). Most notably, our discoveries reveal an older (>10Myr) low-mass population in Taurus, in accord with recent studies of the higher-mass stellar members. The mass function appears to differ between the younger and older Taurus populations, possibly due to incompleteness of the older stellar members or different star formation processes.
- ID:
- ivo://CDS.VizieR/III/172
- Title:
- Radial Velocities from Objective Prism Plates
- Short Name:
- III/172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate positions and radial velocities are determined from 32 objective-prism plates for two areas. Each field is observed twice with opposite dispersion, allowing adjustment of coordinates for spectra not at the plate centers. From the adjusted coordinates and plate overlap, positions are determined with average mean errors: 0.0135 s in RA and 0.177 arcsec in Dec for Area I (near the South Galactic Pole); 0.0315 s in RA, 0.144 arcsec in Dec for Area II (near the galactic plane). Observations were taken by J.D. MacConnell and G. Araya with a six degree prism on the Curtis Schmidt telescope at Cerro Tololo.
