Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/646/1215
- Title:
- Low-mass stars and brown dwarfs in NGC 2024
- Short Name:
- J/ApJ/646/1215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a near-infrared spectroscopic study of candidate brown dwarfs and low-mass stars in the young cluster NGC 2024. Using FLAMINGOS on the KPNO 2.1m and 4m telescopes, we have obtained spectra of ~70 new members of the cluster and classified them via the prominent J- and H-band water absorption features. Derived spectral types range from ~M1 to later than M8 with typical classification errors of 0.5-1 subclasses. By combining these spectral types with JHK photometry, we place these objects on the H-R diagram and use pre-main-sequence evolutionary models to infer masses and ages. The mean age for this low-mass population of NGC 2024 is 0.5Myr, and derived masses range from ~0.7 to 0.02M_{sun}_ with 23 objects falling below the hydrogen-burning limit. The logarithmic mass function rises to a peak at ~0.2M_{sun}_ before turning over and declining into the substellar regime. There is a possible secondary peak at ~0.035M_{sun}_ ; however, the errors are also consistent with a flat IMF in this region. The ratio of brown dwarfs to stars is similar to that found in the Trapezium but roughly twice the ratio found in IC 348, leading us to conclude that the substellar IMF in young clusters may be dependent on the local star-forming environment.
- ID:
- ivo://CDS.VizieR/J/MNRAS/408/2457
- Title:
- Low-mass stars and brown dwarfs in Praesepe
- Short Name:
- J/MNRAS/408/2457
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Presented are the results of a large and deep optical-near-infrared multi-epoch survey of the Praesepe open star cluster using data from the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Clusters Survey. Multiple colour-magnitude diagrams were used to select potential members and proper motions were used to assign levels of membership probability. From our sample, 145 objects were designated as high probability members (p>=0.6) with most of these having been found by previous surveys although 14 new cluster members are also identified. Our membership assignment is restricted to the bright sample of objects (Z<18). From the fainter sample, 39 candidates were found from an examination of multiple colour-magnitude plots.
- ID:
- ivo://CDS.VizieR/J/A+A/544/A111
- Title:
- Low-mass stars in Coma Ber
- Short Name:
- J/A+A/544/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Little is known about the population of the Coma Berenices open cluster (age~500Myr) below 0.2M_{sun}_, and statistics show that there is a prominent deficit of very low-mass objects in this mass range compared to younger open clusters with ages of <250Myr. We search for very low-mass stars and substellar objects (brown dwarfs) in the Coma open cluster to derive the present-day cluster mass function below 0.2M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/MNRAS/342/1241
- Title:
- Low-mass stars in M45 and M44
- Short Name:
- J/MNRAS/342/1241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present near-infrared J-, H- and K-band photometry and optical spectroscopy of low-mass star and brown dwarf (BD) candidates in the Pleiades and Praesepe open clusters. We flag non-members from their position in K, I-K and J, J-K colour-magnitude diagrams (CMDs), and J-H, H-K two-colour diagrams.
- ID:
- ivo://CDS.VizieR/J/AJ/154/14
- Title:
- Low-mass stars in 25 Ori group and Orion OB1a
- Short Name:
- J/AJ/154/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Orion OB1a sub-association is a rich low-mass star (LMS) region. Previous spectroscopic studies have confirmed 160 LMSs in the 25 Orionis stellar group (25 Ori), which is the most prominent overdensity of Orion OB1a. Nonetheless, the current census of the 25 Ori members is estimated to be lower than 50% complete, leaving a large number of members to be still confirmed. We retrieved 172 low-resolution stellar spectra in Orion OB1a observed as ancillary science in the SDSS-III/BOSS survey, for which we classified their spectral types and determined physical parameters. To determine memberships, we analyzed the H{alpha} emission, LiI{lambda}6708 absorption, and NaI{lambda}{lambda}8183,8195 absorption as youth indicators in stars classified as M type. We report 50 new LMSs spread across the 25 Orionis, ASCC18, and ASCC20 stellar groups with spectral types from M0 to M6, corresponding to a mass range of 0.10{<=}m/M_{Sun}_{<=}0.58. This represents an increase of 50% in the number of known LMSs in the area and a net increase of 20% in the number of 25 Ori members in this mass range. Using parallax values from the Gaia DR1 catalog, we estimated the distances to these three stellar groups and found that they are all co-distant, at 338+/-66pc. We analyzed the spectral energy distributions of these LMSs and classified their disks into evolutionary classes. Using H-R diagrams, we found a suggestion that 25 Ori could be slightly older than the other two observed groups in Orion OB1a.
- ID:
- ivo://CDS.VizieR/J/A+A/488/167
- Title:
- Low-mass stars in {sigma} Ori and {lambda} Ori
- Short Name:
- J/A+A/488/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a detailed membership selection and studied the accretion properties of low-mass stars in the two apparently very similar young (1-10Myr) clusters {sigma} Ori and {lambda} Ori. We observed 98 and 49 low-mass (0.2-1.0M_{sun}_stars in {sigma} Ori and {lambda} Ori respectively, using the multi-object optical spectrograph FLAMES at the VLT, with the high-resolution (R~17000) HR15N grating (6470-6790{AA}). We used radial velocities, Li and H{alpha} to establish cluster membership and H{alpha} and other optical emission lines to analyze the accretion properties of members. We identified 65 and 45 members of the {sigma} Ori and {lambda} Ori clusters, respectively, and discovered 16 new candidate binary systems.
- ID:
- ivo://CDS.VizieR/J/A+A/559/A3
- Title:
- Low-mass stars in Trumpler 37
- Short Name:
- J/A+A/559/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of accretion and protoplanetary disks around M-type stars in the 4 Myr-old cluster Tr 37. With a well-studied solar-type population, Tr 37 is a benchmark for disk evolution. We used low-resolution spectroscopy to identify and classify 141 members (78 new ones) and 64 probable members, mostly M-type stars. H{alpha} emission provides information about accretion. Optical, 2MASS, Spitzer, and WISE data are used to trace the spectral energy distributions (SEDs) and search for disks. We construct radiative transfer models to explore the structures of full-disks, pre-transition, transition, and dust-depleted disks.
- ID:
- ivo://CDS.VizieR/V/80
- Title:
- Low-Mass Stars' Membership in Alpha Persei Cluster
- Short Name:
- V/80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains the tabulated results of a combined astrometric, photometric, and spectroscopic search for low-mass members in the intermediate-age open cluster Alpha Persei. It contains information on 132 new members and likely members, and 16 uncertain members of Alpha Per. The new membership information suggested to the author a revised age of the cluster to approximately 8x10+7yr. Tabulated data include AP number, VBI photometry, 1950 coordinates, relative proper motions with errors, H-alpha equivalent widths, and spectral type. Included are the individual membership determinations, based on H-alpha emission, spectral type, and echelle spectra data. The photometric data were obtained with the Lick Obs. 1-m Nickel Telescope using a TI 500x500 pixel CCD in B, V, and I bands. Low dispersion CCD spectra centered on H-alpha for candidates whose V-I photometry indicated likely membership using the Lick 1-m Nickel and 3-m Shane telescopes. High-dispersion echelle spectra were obtained for many bright candidates using the Hamilton echelle spectrographic with the Shane and Coude auxiliary telescopes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/423/2966
- Title:
- Low-mass stars spectroscopy in NGC 2516
- Short Name:
- J/MNRAS/423/2966
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present far-red, intermediate-resolution spectroscopy of 572 photometrically selected, low-mass stars (0.2<M/M_{sun}_<0.7) in the young open cluster NGC 2516, using the FLAMES spectrograph at the Very Large Telescope. Precise radial velocities confirm membership for 210 stars that have published rotation periods from spot-modulated light curves and for another 144 stars in which periodic modulation could not be found. The two subsamples are compared and no significant differences are found between their positions in colour-magnitude diagrams, the distribution of their projected equatorial velocities or their levels of chromospheric activity.