- ID:
- ivo://CDS.VizieR/J/PASP/125/809
- Title:
- New nearby M, L, and T dwarfs
- Short Name:
- J/PASP/125/809
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In our effort to complete the census of low-mass stars and brown dwarfs in the immediate solar neighborhood, we present spectra, photometry, proper motions, and distance estimates for 42 low-mass star and brown dwarf candidates discovered by the Wide-field Infrared Survey Explorer (WISE). We also present additional follow-up information on 12 candidates selected using WISE data but previously published elsewhere. The new discoveries include 15 M dwarfs, 17 L dwarfs, five T dwarfs, and five objects of other types. Among these discoveries is a newly identified "unusually red L dwarf" (WISE J223527.07+451140.9), four peculiar L dwarfs whose spectra are most readily explained as unresolved L+T binary systems, and a T9 dwarf (WISE J124309.61+844547.8). We also show that the recently discovered red L dwarf WISEP J004701.06+680352.1 may be a low-gravity object and hence young and potentially low-mass (<25M_Jup_).
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/158/251
- Title:
- New reduction of UVES data for 35 M dwarfs
- Short Name:
- J/AJ/158/251
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The UVES (Ultraviolet and Visible Spectrometer) M Dwarf Planet Search program surveyed 40 M dwarfs and 1 M giant from 2000 through 2007 March. Two of the M dwarfs were double-lined spectroscopic binaries. The 38 single-lined M dwarfs in this survey are among the nearest and brightest M dwarfs. Starting with the reduced 1D spectra provided by the UVES team, we reanalyzed the UVES velocities of Proxima Cen as part of the "Pale Red Dot" program. The velocity rms decreased from 3.6 to 2.3 m/s. Motivated by this result, we have harvested all of the raw data from the UVES M Dwarf Planet Search from the European Southern Observatory (ESO) archives and have written custom packages to generate 1D spectra from the raw data, and velocities from the 1D spectra. The median improvement in the velocity rms from the new analysis is 1.8 m/s. Six of the 38 M dwarfs from the original study had a velocity rms<4 m/s. In the reanalysis presented here, 22 of these stars have a velocity rms<4 m/s. We improve the upper limits on possible planets orbiting these stars by a factor of typically two to three. For many of these M dwarfs, these observations represent the first epoch of high-precision velocity measurements.
- ID:
- ivo://CDS.VizieR/J/A+A/446/485
- Title:
- New very low-mass members in Taurus
- Short Name:
- J/A+A/446/485
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a large scale optical survey of the Taurus cloud, covering a total area of 28deg^2^, and encompassing the densest parts of the cloud as well as their surroundings, down to a mass detection limit of 15 Jupiter masses. We present the optical spectroscopic follow-up observations of 97 photometrically selected potential new low-mass Taurus members, of which 27 are strong late-M spectral type SpType<M4V candidates. We derive spectral types, visual absorption and luminosity class estimates and discuss our criteria to assess Taurus membership. These observations reveal 5 new VLM Taurus members and 12 new brown dwarfs. Combining our observations with previously published results, we derive an updated substellar to stellar ratio in Taurus of Rss=0.23+/-0.05. This ratio now appears consistent with the value previously derived in the Trapezium cluster under similar assumptions of 0.26+/-0.04. We find indications that the relative numbers of brown dwarfs with respect to stars is decreased by a factor 2 in the central regions of the aggregates with respect to the more distributed population. Our findings are best explained in the context of the embryo-ejection model where brown dwarfs originate from dynamical interactions in small N unstable multiple systems.
- ID:
- ivo://CDS.VizieR/J/AJ/159/267
- Title:
- Observations & radial velocity of HATS-71b
- Short Name:
- J/AJ/159/267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of HATS-71b, a transiting gas giant planet on a P=3.7955day orbit around a G=15.35mag M3 dwarf star. HATS-71 is the coolest M dwarf star known to host a hot Jupiter. The loss of light during transits is 4.7%, more than in any other confirmed transiting planet system. The planet was identified as a candidate by the ground-based HATSouth transit survey. It was confirmed using ground-based photometry, spectroscopy, and imaging, as well as space-based photometry from the NASA Transiting Exoplanet Survey Satellite mission (TIC234523599). Combining all of these data, and utilizing Gaia DR2, we find that the planet has a radius of 1.024{+/-}0.018R_J_ and mass of 0.37{+/-}0.24M_J_ (95% confidence upper limit of <0.80M_J_), while the star has a mass of 0.4861{+/-}0.0060M_{sun}_ and a radius of 0.4783{+/-}0.0060R_{sun}_.
- ID:
- ivo://CDS.VizieR/J/ApJ/876/115
- Title:
- Optical follow-up of ASAS-SN M dwarf flares
- Short Name:
- J/ApJ/876/115
- Date:
- 18 Jan 2022 15:06:46
- Publisher:
- CDS
- Description:
- The All-sky Automated Survey for Supernovae (ASAS-SN) is the only project in existence to scan the entire sky in optical light approximately every day, reaching a depth of g~18mag. Over the course of its first 4yr of transient alerts (2013-2016), ASAS-SN observed 53 events classified as likely M dwarf flares. We present follow-up photometry and spectroscopy of all 53 candidates, confirming flare events on 47 M dwarfs, one K dwarf, and one L dwarf. The remaining four objects include a previously identified T Tauri star, a young star with outbursts, and two objects too faint to confirm. A detailed examination of the 49 flare star light curves revealed an additional six flares on five stars, resulting in a total of 55 flares on 49 objects ranging in V-band contrast from {Delta}V=-1 to -10.2mag. Using an empirical flare model to estimate the unobserved portions of the flare light curve, we obtain lower limits on the V-band energy emitted during each flare, spanning log(E_V_/erg)=32-35, which are among the most energetic flares detected on M dwarfs. The ASAS-SN M dwarf flare stars show a higher fraction of H{alpha} emission, as well as stronger H{alpha} emission, compared to M dwarfs selected without reference to activity, consistent with belonging to a population of more magnetically active stars. We also examined the distribution of tangential velocities, finding that the ASAS-SN flaring M dwarfs are likely to be members of the thin disk and are neither particularly young nor old.
- ID:
- ivo://CDS.VizieR/J/ApJS/183/261
- Title:
- Optical photometry of the ONC
- Short Name:
- J/ApJS/183/261
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present U, B, V, I broadband, 6200{AA} TiO medium band, and H{alpha} narrow band photometry of the Orion Nebula Cluster (ONC) obtained with the WFI imager at the ESO/MPI 2.2 telescope at La Silla Observatory. The nearly simultaneous observations cover the entire ONC in a field of about 34x34arcmin^2^. They enable us to determine stellar colors avoiding the additional scatter in the photometry induced by stellar variability typical of pre-main-sequence stars. We identify 2612 point-like sources in the I band; 58%, 43%, and 17% of them are also detected in V, B, and U, respectively. 1040 sources are identified in the H{alpha} band. In this paper we present the observations, the calibration techniques adopted, and the resulting catalog. We show the derived color-magnitude diagram of the population and discuss the completeness of our photometry. We define a spectrophotometric TiO index that takes into account the fluxes in the V, I, and TiO bands. Comparing it with spectral types of ONC members in the literature, we find a correlation between the index and the spectral type valid for M-type stars, which is accurate to better than 1 spectral subclass for M3-M6 types and better than 2 spectral subclasses for M0-M2 types. This allows us to newly classify 217 stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/214/17
- Title:
- Orbital monitoring of AstraLux binaries
- Short Name:
- J/ApJS/214/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Orbital monitoring of M-type binaries is essential for constraining their fundamental properties. This is particularly useful in young systems, where the extended pre-main-sequence evolution can allow for precise isochronal dating. Here, we present the continued astrometric monitoring of the more than 200 binaries of the AstraLux Large Multiplicity Survey, building both on our previous work, archival data, and new astrometric data spanning the range of 2010-2012. The sample is very young overall --all included stars have known X-ray emission, and a significant fraction (18%) of them have recently also been identified as members of young moving groups in the solar neighborhood. We identify ~30 targets that both have indications of being young and for which an orbit either has been closed or appears possible to close in a reasonable time frame (a few years to a few decades). One of these cases, GJ 4326, is, however, identified as probably being substantially older than has been implied from its apparent moving group membership, based on astrometric and isochronal arguments. With further astrometric monitoring, these targets will provide a set of empirical isochrones, against which theoretical isochrones can be calibrated, and which can be used to evaluate the precise ages of nearby young moving groups.
- ID:
- ivo://CDS.VizieR/J/MNRAS/444/1793
- Title:
- 25 Ori group low-mass stars
- Short Name:
- J/MNRAS/444/1793
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a survey of the low-mass star and brown dwarf population of the 25 Orionis group. Using optical photometry from the CIDA (Centro de Investigaciones de Astronomia Francisco J. Duarte, Merida, Venezuela) Deep Survey of Orion, near-IR photometry from the Visible and Infrared Survey Telescope for Astronomy and low-resolution spectroscopy obtained with Hectospec at the MMT telescope, we selected 1246 photometric candidates to low-mass stars and brown dwarfs with estimated masses within 0.02<~M/M_{sun}_<~0.8 and spectroscopically confirmed a sample of 77 low-mass stars as new members of the cluster with a mean age of ~7Myr. We have obtained a system initial mass function of the group that can be well described by either a Kroupa power-law function with indices {alpha}3=-1.73+/-0.31 and {alpha}2=0.68+/-0.41 in the mass ranges 0.03<=M/M_{sun}_<=0.08 and 0.08<=M/M_{sun}_<=0.5, respectively, or a Scalo lognormal function with coefficients m_c_=0.21^+0.02^_-0.02_ and {sigma}=0.36+/-0.03 in the mass range 0.03<=M/M_{sun}_<=0.8. From the analysis of the spatial distribution of this numerous candidate sample, we have confirmed the east-west elongation of the 25 Orionis group observed in previous works, and rule out a possible southern extension of the group. We find that the spatial distributions of low-mass stars and brown dwarfs in 25 Orionis are statistically indistinguishable. Finally, we found that the fraction of brown dwarfs showing IR excesses is higher than for low-mass stars, supporting the scenario in which the evolution of circumstellar discs around the least massive objects could be more prolonged.
- ID:
- ivo://CDS.VizieR/J/ApJ/817/1
- Title:
- Palomar/MSU and SDSS-DR7 M dwarfs with GALEX obs.
- Short Name:
- J/ApJ/817/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of Galaxy Evolution Explorer Near-UV (NUV) and Far-UV (FUV) photometry for the Palomar/MSU and SDSS DR7 spectroscopic M dwarf catalogs. The catalog contains NUV measurements matched to 577 spectroscopically confirmed M dwarfs and FUV measurements matched to 150 spectroscopically confirmed M dwarfs. Using these data, we find that NUV and FUV luminosities strongly correlate with H{alpha} emission, a typical indicator of magnetic activity in M dwarfs. We also examine the fraction of M dwarfs with varying degrees of strong line emission at NUV wavelengths. Our results indicate that the frequency of M dwarf NUV emission peaks at intermediate spectral types, with at least ~30% of young M4-M5 dwarfs having some level of activity. For mid-type M dwarfs, we show that NUV emission decreases with distance from the Galactic plane, a proxy for stellar age. Our complete matched source catalog is available online.
- ID:
- ivo://CDS.VizieR/III/198
- Title:
- Palomar/MSU nearby star spectroscopic survey
- Short Name:
- III/198
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Third Catalogue of Nearby Stars (Gliese & Jahreiss, "Preliminary Version of the third Catalogue of Nearby Stars" (CNS3), 1991, catalog <V/70>) includes over 1850 stars which lie north of Dec.= -30{deg} and are either identified as spectral type M, or are unclassified but with an absolute visual magnitude estimate M_V_ > +8.0. Although there is no uniformity in selection criteria, and many of the stars lack basic data (radial velocities, spectral types, accurate photometry), the observational properties of these stars underlie most estimates of the fundamental characteristics of the Galactic Disk. We have obtained optical spectroscopy of 1746 of the 1876 stars -- the remaining 130 are binary companions of brighter stars and inaccessible to our observations. These spectra allow us, first, to exclude 61 stars as either degenerates or as misclassified earlier-type (B-K) stars lying beyond the 25 pc limit; to establish radial velocities accurate to +/-10km/s for all stars confirmed as late-type dwarfs; to determine spectral types and absolute magnitudes from the TiO bandstrength, allowing more accurate distance estimates for stars with inaccurate (or no) trigonometric parallax measurements; and to identify stars with H{alpha} emission (chromospherically active stars) and with strong CaH absorption (perhaps including some metal-poor disk subdwarfs). We have determined the nearby-star luminosity function from complete samples derived by applying both the distance limits defined by Wielen (1974, Highlights of Astron. 3, 395) and by using limits derived from our own analysis. Spectroscopic data for the southern stars (Dec.<-30{deg}) in the PMSU survey are also presented. The data were combined with the data from paper I to obtain a list of all the magnetically active dMe stars in the survey.
