- ID:
- ivo://CDS.VizieR/J/AJ/134/1162
- Title:
- 11 new T dwarfs in 2MASS
- Short Name:
- J/AJ/134/1162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of 11 new T dwarfs, found during the course of a photometric survey for mid-to-late T dwarfs in the 2MASS Point Source Catalog and from a proper-motion-selected sample of ultracool dwarfs in the 2MASS Working Database. Using the NASA Infrared Telescope Facility SpeX spectrograph, we obtained low-resolution (R~150) spectroscopy, allowing us to derive near-infrared spectral types of T2-T8. We also present improved signal-to-noise ratio SpeX low-resolution spectroscopy of the near-infrared T0 standard SDSS J120747.17+024424.8 and T1 standard SDSSp J083717.22-000018.3. One of these new T dwarfs, 2MASS J13243559+6358284, was also discovered independently by Metchev et al.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/312/439
- Title:
- New T Tauri stars in Taurus-Auriga
- Short Name:
- J/A+A/312/439
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On the basis of the ROSAT All-Sky-Survey, a study of the Taurus-Auriga star forming region has been performed in order to search for hitherto undiscovered T Tauri stars. Our study covers an area of about 280 square degrees, located between 4^h^ and 5^h^ in right ascension and between 15deg and 34deg in declination. Identification of ROSAT All-Sky Survey sources in this area by means of optical spectroscopy revealed 2 new classical T Tauri stars (CTTS) and 66 new weak-line-T Tauri stars (WTTS) with W_{lambda}_(H{alpha})<=10A. Additional pointed ROSAT observations led to the identification of 6 more WTTS and 2 CTTS, giving a total of 76 new T Tauri stars. The large area of our study, as compared with previous works, allows us to study the spatial distribution of WTTS in this star forming region. We find the WTTS of our survey to be distributed over the whole region investigated. There is a noticeable decline of the surface density from south to north within our study area, but the spatial distribution extends most probably beyond our study region. No clustering towards the population of T Tauri stars known prior to ROSAT in Taurus-Auriga could be observed. We suggest that the WTTS found in our study might in part be somewhat older than the previously known T Tauri stars in Taurus-Auriga, and that their broad spatial distribution is due to the typical velocity dispersion of a few km/s measured for Taurus T Tauri stars, in which case for some of our WTTS an age on the order of 10^7^years would be required for reaching the observed distances from the Taurus dark clouds. We estimate a WTTS/CTTS ratio of about 6 within our study area, but conclude that because of the different spatial distribution of WTTS and CTTS this ratio will be most probably significantly larger for a more extended area.
- ID:
- ivo://CDS.VizieR/J/A+AS/123/329
- Title:
- New weak-line T Tauri stars in Lupus
- Short Name:
- J/A+AS/123/329
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present first results obtained by a survey of the Lupus star forming region in search of new T Tauri stars. This study has been performed on the basis of deep pointed ROSAT observations in the Lupus dark clouds as well as data from the ROSAT All-Sky-Survey in the surrounding, less obscured regions. Our survey covers an area of about 230 square degrees, located between 15^h^6^m^ and 16^h^24^m^ in right ascension and between -47{deg} and -32{deg} in declination. Identification of ROSAT All-Sky-Survey sources in this area by means of optical spectroscopy revealed 89 T Tauri stars, 86 of them "weak-line" T Tauri stars (WTTS not known from previous studies of this region. Our pointed ROSAT observations led to the identification of 47 more T Tauri stars, giving a total of 136 new T Tauri stars. The large area of our study, as compared with previous works, allows us to study the spatial distribution of WTTS in this star forming region on alarge scale. We find the new WTTS to be distributed over the whole area of our survey, indicating that their spatial distribution might extend well beyond our study area. Contrary to the Lupus T Tauri stars known prior to this study, the WTTS discovered by the ROSAT All-Sky-Survey are not clustered in the regions of highest extinction, i.e. the dark clouds.
- ID:
- ivo://CDS.VizieR/J/A+AS/132/173
- Title:
- New weak-line T Tauri stars in Taurus-Auriga
- Short Name:
- J/A+AS/132/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of an extensive search for weak-line T Tauri stars (WTTS) in the outskirts of the Taurus-Auriga molecular cloud on the basis of the ROSAT All-Sky Survey Bright Source Catalog (Cat. <IX/10>). Our surveyed region extends from 2h 40m to 5h 40m in right ascension and from 10deg to 40deg in declination, with the central part of Taurus-Auriga(4h<{alpha}<5h, 15deg<{delta}<34deg), accomplished by Wichmann et al. (1996, Cat. <J/A+A/312/439>), excluded. Within a sky coverage of about 10$^{3}$ square degrees, 219 X-ray sources fullfill the criteria for selecting program sources suggested by Neuhauser et al. (1995A&A...295L...5N) and 164 of these X-ray sources were found to have at least one optical counterpart with E magnitude brighter than 16. Low-resolution spectroscopic observation has been carried out in order to discard early type stars and galaxies from the sample, additional intermediate-resolution spectra of a sub-sample of 156 late type optical counterparts were obtained for spectral classification and for the calculation of the equivalent width of H{alpha} emission and LiI line absorption at 6707{AA}. Excluding 2 previously identified WTTS, a total of 75 new candidate WTTS and one possible classical T Tauri star have been discovered in our study. The majority of the newly found Li-rich optical counterparts are believed to b e PMS stars rather than ZAMS stars as those of the Pleiades.
- ID:
- ivo://CDS.VizieR/J/A+A/319/184
- Title:
- New WTTS in the Chamaeleon complex
- Short Name:
- J/A+A/319/184
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse the nature of the optical counterparts of the ROSAT all-sky survey (RASS) X-ray sources identified with new weak-line T Tauri (WTTS) stars in the Chamaeleon star forming region (SFR). The new WTTS are distributed throughout the whole SFR, while the classical T Tauri stars (CTTS) are found only in the cloud cores. Adopting a distance of 150pc we derive the stellar parameters and place the new WTTS in the HR diagram. By comparison with theoretical pre-main sequence (PMS) evolutionary tracks, we find masses in the range of 0.2-2.5M_{sun}_ and ages from a few 10^5^yr to 5x10^7^yr. Many of the youngest WTTS are located far away from the main Chamaeleon dark clouds.
- ID:
- ivo://CDS.VizieR/J/ApJS/196/4
- Title:
- New young star candidates in Taurus-Auriga
- Short Name:
- J/ApJS/196/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Taurus Molecular Cloud subtends a large solid angle on the sky, in excess of 250deg^2^. The search for legitimate Taurus members to date has been limited by sky coverage as well as the challenge of distinguishing members from field interlopers. The Wide-field Infrared Survey Explorer has recently observed the entire sky, and we take advantage of the opportunity to search for young stellar object (YSO) candidate Taurus members from a ~260deg^2^ region designed to encompass previously identified Taurus members. We use near- and mid-infrared colors to select objects with apparent infrared excesses and incorporate other catalogs of ancillary data to present a list of rediscovered Taurus YSOs with infrared excesses (taken to be due to circumstellar disks), a list of rejected YSO candidates (largely galaxies), and a list of 94 surviving candidate new YSO-like Taurus members. There is likely to be contamination lingering in this candidate list, and follow-up spectra are warranted.
- ID:
- ivo://CDS.VizieR/J/AJ/156/76
- Title:
- New young stars and brown dwarfs in Upper Sco
- Short Name:
- J/AJ/156/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To improve the census of the Upper Sco association (~11 Myr, ~145 pc), we have identified candidate members using parallaxes, proper motions, and color-magnitude diagrams from several wide-field imaging surveys and have obtained optical and infrared spectra of several hundred candidates to measure their spectral types and assess their membership. We also have performed spectroscopy on a smaller sample of previously known or suspected members to refine their spectral types and evidence of membership. We have classified 530 targets as members of Upper Sco, 377 of which lack previous spectroscopy. Our new compilation of all known members of the association contains 1631 objects. Although the census of Upper Sco has expanded significantly over the last decade, there remain hundreds of candidates that lack spectroscopy. The precise parallaxes and proper motions from the second data release of Gaia should extend down to substellar masses in Upper Sco, which will greatly facilitate the identification of the undiscovered members.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/2465
- Title:
- New young stars in Pisces Moving Group
- Short Name:
- J/MNRAS/473/2465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the kinematically unbiased technique described in Binks, Jeffries & Maxted (2015MNRAS.452..173B, Cat. J/MNRAS/452/173), we present optical spectra for a further 122 rapidly-rotating (rotation periods < 6 days), X-ray active FGK stars, selected from the SuperWASP survey. We identify 17 new examples of young, probably single stars with ages of <200Myr and provide additional evidence for a new northern hemisphere kinematic association: the Pisces Moving Group (MG). The group consists of 14 lithium-rich G- and K-type stars, that have a dispersion of only ~3km/s in each Galactic space velocity coordinate. The group members are approximately co-eval in the colour-magnitude diagram, with an age of 30-50 Myr, and have similar, though not identical, kinematics to the Octans-Near MG.
- ID:
- ivo://CDS.VizieR/J/ApJ/671/605
- Title:
- NGC 2264 and ONC PMS stars in the infrared
- Short Name:
- J/ApJ/671/605
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of pre-main-sequence star rotation periods reveal slow rotators in young clusters of various ages, indicating that angular momentum is somehow removed from these rotating masses. The mechanism by which spin-up is regulated as young stars contract has been one of the longest standing problems in star formation. Attempts to observationally confirm the prevailing theory that magnetic interaction between the star and its circumstellar disk regulates these rotation periods have produced mixed results. In this paper, we use the unprecedented disk identification capability of the Spitzer Space Telescope to test the star-disk interaction paradigm in two young clusters, NGC 2264 and the Orion Nebula Cluster (ONC).
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/3597
- Title:
- NGC 2282 BVI Ha observations
- Short Name:
- J/MNRAS/454/3597
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of the stellar content of NGC 2282, a young cluster in the Monoceros constellation, using deep optical BVI and INT Photometric H{alpha} Survey (IPHAS) photometry along with infrared (IR) data from UKIRT Infrared Deep Sky Survey and Spitzer-IRAC. Based on the stellar surface density analysis using nearest neighbourhood method, the radius of the cluster is estimated as ~3.15-arcmin. From optical spectroscopic analysis of eight bright sources, we have classified three early B-type members in the cluster, which includes, HD 289120, a previously known B2V-type star, a Herbig Ae/Be star (B0.5 Ve) and a B5 V star. From spectrophotometric analyses, the distance to the cluster has been estimated as ~1.65kpc. The K-band extinction map is estimated using nearest neighbourhood technique, and the mean extinction within the cluster area is found to be A_V_~3.9mag. Using IR colour-colour criteria and H{alpha}-emission properties, we have identified a total of 152 candidate young stellar objects (YSOs) in the region, of which, 75 are classified as Class II, nine are Class I YSOs. Our YSO catalogue also includes 50 H{alpha}-emission line sources, identified using slitless spectroscopy and IPHAS photometry data. Based on the optical and near-IR colour-magnitude diagram analyses, the cluster age has been estimated to be in the range of 2-5Myr, which is in agreement with the estimated age from disc fraction (~58 per cent). Masses of these YSOs are found to be ~0.1-2.0M_{sun}_. Spatial distribution of the candidate YSOs shows spherical morphology, more or less similar to the surface density map.
