- ID:
- ivo://CDS.VizieR/J/A+A/568/A49
- Title:
- Long-term photometry of pre-MS stars
- Short Name:
- J/A+A/568/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To broaden the search and study stars in the early evolutionary phase, we investigated a sample of 17 pre-main sequence objects previously detected as either H{alpha} emission-line pre-main sequence stars or T Tauri variables located in the field of the North America/Pelican Nebula complex. Johnson-Cousins B, V, Rc, Ic magnitudes and mean color indices for the program stars are determined from more than 12400 measurements from archive photographic plates and from CCD data collected at 7 observatories covering the period of almost 60 years from 1954 up to 2013. We complemented previously rare insights on the photometry of the program stars and presented their photometric history, which for almost all program stars is the first long term photometric monitoring on a timescale of 6 decades. Eight program stars are found to be classical T Tauri stars of variability type II, while 6 program stars are weak-line T Tauri stars of variability type I. For the first time, periodicity is found for three stars: V1716 Cyg indicates a 4.15 day period, V2051 Cyg indicates a 384 day period, and V521 Cyg a period of 503 days.
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Search Results
- ID:
- ivo://CDS.VizieR/J/other/PASA/32.11
- Title:
- Long-term UBVRI photometry of GM Cep
- Short Name:
- J/other/PASA/32.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results from UBVRI photometric observations of the pre-main sequence star GM Cephei obtained in the period April 2011 - August 2014 are reported in the paper. Presented data are a continuation of our photometric monitoring of the star started in 2008. GM Cep is located in the field of the young open cluster Trumpler 37 and over the past years it has been an object of intense photometric and spectral studies. The star shows a strong photometric variability interpreted as a possible outburst from EXor type in previous studies. Our photometric data for a period of over six years show a large amplitude variability ({Delta}V~2.3mag) and several deep minimums in brightness are observed. The analysis of the collected multicolor photometric data show the typical of UX Ori variables a colour reversal during the minimums in brightness. The observed decreases in brightness have a different shape, and evidences of periodicity are not detected. At the same time, high amplitude rapid variations in brightness typical for the classical T Tauri stars also present on the light curve of GM Cep. The spectrum of GM Cep shows the typical of classical T Tauri stars wide H alpha emission line and absorption lines of some metals. We calculate the outer radius of the H{alpha} emitting region as 10.4+/-0.5R_{sun}_ and the accretion rate as 1.8x10^-7^M_{sun}_/yr.
- ID:
- ivo://CDS.VizieR/J/MNRAS/447/1267
- Title:
- Low-mass members of the Octans association
- Short Name:
- J/MNRAS/447/1267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Octans association is one of several young stellar moving groups recently discovered in the Solar neighbourhood and hence a valuable laboratory for studies of stellar, circumstellar disc and planetary evolution. However, a lack of low-mass members or any members with trigonometric parallaxes means the age, distance and space motion of the group are poorly constrained. To better determine its membership and age, we present the first spectroscopic survey for new K- and M-type Octans members, resulting in the discovery of 29 UV-bright K5-M4 stars with kinematics, photometry and distances consistent with existing members. Nine new members possess strong LiI 6708 absorption, which allow us to estimate a lithium age of 30-40Myr, similar to that of the Tucana-Horologium association and bracketed by the firm lithium depletion boundary ages of the beta Pictoris (20Myr) and Argus/IC 2391 (50Myr) associations. Several stars also show hints in our medium-resolution spectra of fast rotation or spectroscopic binarity. More so than other nearby associations, Octans is much larger than its age and internal velocity dispersion imply. It may be the dispersing remnant of a sparse, extended structure which includes some younger members of the foreground Octans-Near association recently proposed by Zuckerman and collaborators.
- ID:
- ivo://CDS.VizieR/J/AJ/131/3016
- Title:
- Low-mass objects in Upper Scorpius
- Short Name:
- J/AJ/131/3016
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a wide-field photometric survey covering ~200^{deg}^2 toward the Upper Scorpius OB association. Data taken in the R and I bands with the Quest-2 camera on the Palomar 48inch (1.2m) telescope were combined with the Two Micron All Sky Survey JHK_S_ survey and used to select candidate pre-main-sequence stars. Follow-up spectroscopy with the Palomar 200inch (5.1m) telescope of 62 candidate late-type members identified 43 stars that have surface gravity signatures consistent with association membership.
- ID:
- ivo://CDS.VizieR/J/ApJ/688/377
- Title:
- Low-mass objects in Upper Scorpius. II.
- Short Name:
- J/ApJ/688/377
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present continued results from a wide-field, ~150{deg}^2^, optical photometric and spectroscopic survey of the northern part of the ~5Myr old Upper Scorpius OB association. Photometry and spectral types were used to derive effective temperatures and luminosities and place newly identified association members onto a theoretical Hertzsprung-Russell diagram. From our survey, we have discovered 145 new low-mass members of the association and determined ~10% of these objects to be actively accreting material from a surrounding circumstellar disk.
- 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/ApJ/578/914
- Title:
- Low-mass stars in Taurus
- Short Name:
- J/ApJ/578/914
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The basic sample of young stars in Taurus used in this paper is taken from the tabulation of Kenyon & Hartmann (1995, Cat. <J/ApJS/101/117>) with various additions. A few new low-mass stars were added from the studies of Briceno et al. (1998AJ....115.2074B, 1999AJ....118.1354B). I further added a few stars from the ROSAT All-Sky Survey (RASS) studies of Wichmann et al. (1996A&A...312..439W, 2000A&A...359..181W).
- ID:
- ivo://CDS.VizieR/J/AJ/128/805
- Title:
- Low-mass stars in the Cepheus OB2 region
- Short Name:
- J/AJ/128/805
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first identification of low-mass (spectral types K-M) stars in the young clusters Tr37 and NGC7160, members of the CepOB2 association. This is part of a program to follow the evolution of protoplanetary accretion disks through the ages thought to be crucial to understanding disk dissipation and planet formation (~3-10Myr). Combining optical photometry and optical spectroscopy, we have identified ~40 members in Tr37 and ~15 in NGC7160, using several independent tests for determining the membership (optical colors, optical variability, H{alpha} emission, and Li{lambda}6707 absorption).
- ID:
- ivo://CDS.VizieR/J/AJ/120/479
- Title:
- Low-mass stars in the Upper Sco association
- Short Name:
- J/AJ/120/479
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Upper Scorpius association is the OB association nearest to the Sun (145pc). Its young age (~5Myr) makes it an ideal place to search for low-mass stars and brown dwarfs, as these objects should be relatively bright. We have performed a photometric search for the low-mass members of the association, using the R, I, and Z filters. The completeness limit is I~18.5, and the saturation limit is I~13. We obtain 138 candidate members, covering nearly the entire M spectral type range. We find an excess of brown dwarf candidates over the number predicted by a Miller-Scalo initial mass function. In addition, we have performed infrared imaging and low-resolution optical spectroscopy of selected candidates. We find that the infrared observations confirm the spectral types obtained with the optical photometry. Furthermore, we find H{alpha} in emission in 20 of the 22 objects observed spectroscopically. As H{alpha} is an indicator of youth, we believe that these 20 objects may belong to the association. One of them, UScoCTIO 128, has a very strong and constant H{alpha} line (equivalent width -130{AA}), and its position in the color-magnitude diagram suggests that it is a brown dwarf with mass 0.02M_{sun}_. Confirmation of this and the other candidates will have to wait for higher resolution observations that can reveal spectroscopic mass indicators such as LiI and gravity indicators such as KI and the subordinate lines of NaI.
- 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.