- 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.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/384/1399
- Title:
- Proper motions of field L and T dwarfs
- Short Name:
- J/MNRAS/384/1399
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The proper motion measurements for 142 previously known L and T dwarfs are presented. From this sample we identify and discuss eight high-velocity L dwarfs. We also find four new wide common proper motion binaries/multiple systems. Using the moving cluster methods we have also identified a number of L dwarfs that may be members of the Ursa Major (age~400Myr), the Hyades (age~625Myr) and the Pleiades (age~125Myr) moving groups.
- ID:
- ivo://CDS.VizieR/J/MNRAS/390/1517
- Title:
- Proper motions of field L and T dwarfs
- Short Name:
- J/MNRAS/390/1517
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By using images taken with Wide Field Camera (WFCAM) on United Kingdom Infrared Telescope (UKIRT) and Son of ISAAC (SofI) on the New Technology Telescope (NTT) and combining them with Two Micron All Sky Survey (2MASS) we have measured proper motions for 125 L and T dwarfs in the dwarf archive. Two of these L dwarfs appear to have M dwarf common proper motion companions, and two also appear to be high-velocity dwarfs, indicating possible membership of the thick disc. We have also compared the motion of these 125 objects to that of numerous moving groups, and have identified new members of the Hyades, Ursa Major and Pleiades moving groups. These new objects, as well as those identified in Jameson et al. have allowed us to refine the L dwarf sequence for Ursa Major that was defined by Jameson et al, 2008 (Cat. J/MNRAS/384/1399).
- ID:
- ivo://CDS.VizieR/J/PASJ/59/335
- Title:
- Properties of 160 F-K disk dwarfs/subgiants
- Short Name:
- J/PASJ/59/335
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The properties of 160 F, G, and K disk dwarfs/subgiants (including 27 planet-host stars) mostly within -0.6<~[Fe/H]<~+0.4, the Okayama Astrophysical Observatory spectrum collection of which had been made open to the public recently, were extensively investigated with particular attention to determining (1) the mass and the age with the help of theoretical stellar evolution calculations, (2) the kinematic parameters of orbital motions in the Galaxy, and (3) the abundances of 15 elements (Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, and Zn) by analyzing the spectra in this database. The resulting characteristics are discussed in terms of several relevant topics of interest, such as a validity check for assuming LTE, the [X/Fe] vs. [Fe/H] diagram containing information on the chemical evolution of the Galactic disk, the age-metallicity-kinematics relation, and the difference/similarity between stars with and without planets.
- ID:
- ivo://CDS.VizieR/J/ApJ/789/102
- Title:
- Properties of late M-dwarfs
- Short Name:
- J/ApJ/789/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The distribution of multiplicity among low-mass stars is a key issue to understanding the formation of stars and brown dwarfs, and recent surveys have yielded large enough samples of nearby low-mass stars to study this issue statistically to good accuracy. Previously, we have presented a multiplicity study of ~700 early/mid M-type stars observed with the AstraLux high-resolution Lucky Imaging cameras. Here, we extend the study of multiplicity in M-type stars through studying 286 nearby mid/late M-type stars, bridging the gap between our previous study and multiplicity studies of brown dwarfs. Most of the targets have been observed more than once, allowing us to assess common proper motion to confirm companionship. We detect 68 confirmed or probable companions in 66 systems, of which 41 were previously undiscovered. Detections are made down to the resolution limit of ~100 mas of the instrument. The raw multiplicity in the AstraLux sensitivity range is 17.9%, leading to a total multiplicity fraction of 21%-27% depending on the mass ratio distribution, which is consistent with being flat down to mass ratios of ~0.4, but cannot be stringently constrained below this value. The semi-major axis distribution is well represented by a log-normal function with {mu}_a_= 0.78 and {sigma}_a_= 0.47, which is narrower and peaked at smaller separations than for a Sun-like sample. This is consistent with a steady decrease in average semi-major axis from the highest-mass binary stars to the brown dwarf binaries.
- 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/A+A/658/A115
- Title:
- Proxima Cen ESPRESSO RV and FWHM
- Short Name:
- J/A+A/658/A115
- Date:
- 21 Feb 2022 11:58:12
- Publisher:
- CDS
- Description:
- Proxima Centauri is the closest star to the Sun. This small, low-mass, mid M dwarf is known to host an Earth-mass exoplanet with an orbital period of 11.2 days within the habitable zone, as well as a long-period planet candidate with an orbital period of close to 5yr. We report on the analysis of a large set of observations taken with the ESPRESSO spectrograph at the aimed at a thorough evaluation of the presence of a third low-mass planetary companion, which started emerging during a previous campaign. Radial velocities (RVs) were calculated using both a cross-correlation function (CCF) and a template matching approach. The RV analysis includes a component to model Proxima`s activity using a Gaussian process (GP). We use the CCF's full width at half maximum to help constrain the GP, and we study other simultaneous observables as activity indicators in order to assess the nature of any potential RV signals. We detect a signal at 5.12+/-0.04 days with a semi-amplitude of 39+/-7cm/s. The analysis of subsets of the ESPRESSO data, the activity indicators, and chromatic RVs suggest that this signal is not caused by stellar variability but instead by a planetary companion with a minimum mass of 0.26+/-0.05M_{sun}_ (about twice the mass of Mars) orbiting at 0.029 au from the star. The orbital eccentricity is well constrained and compatible with a circular orbit.
- ID:
- ivo://CDS.VizieR/J/A+A/639/A77
- Title:
- Proxima Cen RV, FWHM and fluxes
- Short Name:
- J/A+A/639/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The discovery of Proxima b marked one of the most important milestones in exoplanetary science in recent years. Yet the limited precision of the available radial velocity data and the difficulty in modelling the stellar activity calls for a confirmation of the Earth-mass planet. We aimed to confirm the presence of Proxima b using independent measurements obtained with the new ESPRESSO spectrograph, and refine the planetary parameters taking advantage of its improved precision. We analysed 63 spectroscopic ESPRESSO observations of Proxima (Gl 551) taken during 2019. We obtained radial velocity measurements with a typical radial velocity photon noise of 26cm/s. We combined these data with archival spectroscopic observations and newly obtained photometric measurements to model the stellar activity signals and disentangle them from planetary signals in the radial velocity (RV) data. We ran a joint Markov chain Monte Carlo analysis on the time series of the RV and full width half maximum of the cross-correlation function to model the planetary and stellar signals present in the data, applying Gaussian process regression to deal with the stellar activity signals. We confirm the presence of Proxima b independently in the ESPRESSO data and in the combined ESPRESSO+HARPS+UVES dataset. The ESPRESSO data on its own shows Proxima b at a period of 11.218+/-0.029-days, with a minimum mass of 1.29+/-0.13Me. In the combined dataset we measure a period of 11.18427+/-0.00070 days with a minimum mass of 1.173+/-0.086Me. We get a clear measurement of the stellar rotation period (87+/-12d) and its induced RV signal, but no evidence of stellar activity as a potential cause for the 11.2-days signal. We find some evidence for the presence of a second short-period signal, at 5.15-days with a semi-amplitude of only 40cm/s. If caused by a planetary companion, it would correspond to a minimum mass of 0.29+/-0.08Me. We find that for the case of Proxima, the full width half maximum of the cross-correlation function can be used as a proxy for the brightness changes and that its gradient with time can be used to successfully detrend the RV data from part of the influence of stellar activity. The activity-induced RV signal in the ESPRESSO data shows a trend in amplitude towards redder wavelengths. Velocities measured using the red end of the spectrograph are less affected by activity, suggesting that the stellar activity is spot dominated. This could be used to create differential RVs that are activity dominated and can be used to disentangle activity-induced and planetary-induced signals. The data collected excludes the presence of extra companions with masses above 0.6Me at periods shorter than 50-days.
- ID:
- ivo://CDS.VizieR/J/A+A/339/123
- Title:
- PSR J1012+5307 evolutionary tracks
- Short Name:
- J/A+A/339/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a set of evolutionary tracks for white dwarfs with helium cores in the mass range from 0.179 to 0.414M_{sun}_. The tracks are based on a 1M_{sun}_ model sequence extending from the pre-main sequence stage up to the tip of the red-giant branch. Applying large mass loss rates at appropriate positions forced the models to move off the giant branch.The further evolution was then followed across the Hertzsprung-Russell diagram and down the cooling branch.
- ID:
- ivo://CDS.VizieR/J/AJ/157/100
- Title:
- Radial velocities and bisector spans for K2-287
- Short Name:
- J/AJ/157/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of K2-287b, a Saturn mass planet orbiting a G-dwarf with a period of P~15 days. First uncovered as a candidate using K2 campaign 15 data, follow-up photometry and spectroscopy were used to determine a mass M_P_=0.317+/-0.026 M_J_, radius R_P_=0.833+/-0.013 R_J_, period P=14.893291+/-0.000025 days, and eccentricity e=0.476+/-0.026. The host star is a metal-rich V=11.410+/-0.129 mag G-dwarf for which we estimate a mass M_*_=1.056_-0.021_^+0.022^ M_{sun}__, radius R_*_=1.070+/-0.010 R_{sun}_, metallicity [Fe/H]=0.20+/-0.05, and T_eff_=5673+/-75 K. This warm eccentric planet with a time-averaged equilibrium temperature of T_eq_~800 K adds to the small sample of giant planets orbiting nearby stars whose structure is not expected to be affected by stellar irradiation. Follow-up studies on the K2-287 system could help constrain theories of planet migration in close-in orbits.
