- ID:
- ivo://CDS.VizieR/J/A+A/485/931
- Title:
- Young stars and brown dwarfs in Ori OB1b
- Short Name:
- J/A+A/485/931
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present here exhaustive lists of known young stars and new candidate members around Alnilam and Mintaka in the Ori OB1b association as well as of fore- and background sources. A total of 133 stars display features of extreme youth, including early spectral types, lithium in absorption, or mid-infrared flux excess. Other two young brown dwarf and 289 star candidates have been identified from an optical/near-infrared colour-magnitude diagram. We list additional 74 known objects that might belong to the association. This compilation of tables can serve as an input for characterisation of the stellar and high-mass substellar populations in the Orion Belt.
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24062. Young stars in Cepheus OB3b
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/545
- Title:
- Young stars in Cepheus OB3b
- Short Name:
- J/MNRAS/403/545
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric study of I-band variability in the young association Cepheus OB3b. The study is sensitive to periodic variability on time-scales of less than a day, to more than 20d. After rejection of contaminating objects using V, I, R and narrow-band H{alpha} photometry, we find 475 objects with measured rotation periods, which are very likely pre-main-sequence members of the Cep OB3b star-forming region.
- ID:
- ivo://CDS.VizieR/J/AJ/130/188
- Title:
- Young stars in Trumpler 37 and NGC 7160
- Short Name:
- J/AJ/130/188
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of MMT observations of young stars for our study of protoplanetary disks at ages 1-10Myr in two young clusters located in the Cepheus OB2 region: Trumpler 37 (embedded in the HII region IC 1396) and NGC 7160. Using low-resolution optical spectra from the Hectospec multifiber spectrograph, we have tripled the number of known low-mass cluster members, identifying 130 new members in Tr 37 and 30 in NGC 7160. We use indicators of youth (Li absorption at 6707{AA}) and accretion/chromospheric activity (H{alpha} emission) to identify and classify the low-mass cluster members. We derive spectral types for all the low-mass candidates and calculate the individual extinctions and the average over the clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/889/50
- Title:
- Young stars near CG30 in the Gum Nebula
- Short Name:
- J/ApJ/889/50
- Date:
- 10 Nov 2021 13:50:07
- Publisher:
- CDS
- Description:
- We have conducted a high-dispersion (R~34000) optical spectroscopic study of 10 young stars near the cometary globule CG 30 in the Gum Nebula, a diffuse HII region home to at least 32 cometary globules. All 10 spectroscopically observed stars at the nebula's northern edge are of low mass (spectral types M4.5-K5), have broad H{alpha} emission, and show spectral veiling. Eight of the 10 are classical T Tauri stars. We spectroscopically measure the photospheric properties of CG 30 IRS 4 inside CG 30. Though embedded, CG 30 IRS 4 is T Tauri-like, with relatively slow projected rotation and moderate veiling. Undepleted Li absorptions, strong H{alpha} emissions, and positions well above the main sequence on an H-R diagram suggest that the 10 stars are <~1Myr old. Using our measurements, previous spectroscopy, and previous photometry of 11 other young stars in the area, we determine stellar, kinematic, and accretion properties of a total of 21 young stars. Shared radial velocities, proper motions, distances, and ages suggest that 14 of the young stars (including CG 30 IRS 4) are kinematically related to CG 30. From Gaia DR2 distances to six of these stars, we derive a distance of 358.1+/-2.2pc to the cometary globule complex CG 30/31/38. The CG 30 association has an accretor fraction of 29%+/-14%, low for quiescent clusters of similar age but consistent with other irradiated clusters. The Gum Nebula's moderate radiation environment (G_0_=6.6_-2.7_^+3.2^ at CG 30) may be strong enough to shorten disk lifetimes.
24065. Young stars near the Sun
- ID:
- ivo://CDS.VizieR/J/other/ARA+A/42.685
- Title:
- Young stars near the Sun
- Short Name:
- J/other/ARA+A/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Until the late 1990s the rich Hyades and the sparse UMa clusters were the only coeval, comoving concentrations of stars known within 60 pc of Earth. Both are hundreds of millions of years old. Then beginning in the late 1990s the TW Hydrae Association, the Tucana/Horologium Association, the beta Pictoris Moving Group, and the AB Doradus Moving Group were identified within ~60pc of Earth, and the eta Chamaeleontis cluster was found at 97pc. These young groups (ages 8-50Myr), along with other nearby, young stars, will enable imaging and spectroscopic studies of the origin and early evolution of planetary systems.
- ID:
- ivo://CDS.VizieR/J/A+AS/124/449
- Title:
- Young stars south of Taurus-Auriga
- Short Name:
- J/A+AS/124/449
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of intermediate resolution spectroscopy of 131 optical counterparts to 115 ROSAT All-Sky Survey X-ray sources south of the Taurus-Auriga dark cloud complex. These objects have been selected as candidate young stars from a total of 1084 ROSAT sources in a ~300 square degree area. We identify 30 objects as low-mass PMS stars on the basis of the LiI{lambda}6708{AA} doublet in their spectrum, a signature of their young age. All these stars have a spectral type later than F7 and show spectral characteristics typical of weak-line and post-T Tauri stars. The presence of young objects several parsecs away from the regions of ongoing star formation is discussed in the light of the current models of T Tauri dispersal.
- ID:
- ivo://CDS.VizieR/J/ApJ/840/87
- Title:
- Young star systems observed with SALT
- Short Name:
- J/ApJ/840/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic and kinematic analysis of 79 nearby M dwarfs in 77 systems. All of these dwarfs are low-proper-motion southern hemisphere objects and were identified in a nearby star survey with a demonstrated sensitivity to young stars. Using low-resolution optical spectroscopy from the Red Side Spectrograph on the South African Large Telescope, we have determined radial velocities, H-alpha, lithium 6708{AA}, and potassium 7699{AA} equivalent widths linked to age and activity, and spectral types for all of our targets. Combined with astrometric information from literature sources, we identify 44 young stars. Eighteen are previously known members of moving groups within 100pc of the Sun. Twelve are new members, including one member of the TW Hydra moving group, one member of the 32 Orionis moving group, 9 members of Tucana- Horologium, one member of Argus, and two new members of AB Doradus. We also find 14 young star systems that are not members of any known groups. The remaining 33 star systems do not appear to be young. This appears to be evidence of a new population of nearby young stars not related to the known nearby young moving groups.
- ID:
- ivo://CDS.VizieR/J/A+A/557/A29
- Title:
- Young stellar clusters in the Rosette
- Short Name:
- J/A+A/557/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Rosette complex is a well studied region of the galactic plane which presents the apparent characteristics of a triggered star forming region. This is however still debated as no strong evidence corroborates this statement. We focused on characterizing the young stellar population in the Rosette to improve our understanding of the processes that regulate the star formation in this region. We propose an original method relying on the joint analysis of the star color and density in the near-infrared. It yielded the identification of 13 clusters, 2 of them being new discoveries. Based on their spectral index from UKIDSS K-band to WISE W3-band, we identified 535 YSO candidates within these cluster boundaries.
24069. 2403 young stellar groups
- ID:
- ivo://CDS.VizieR/J/A+A/644/A101
- Title:
- 2403 young stellar groups
- Short Name:
- J/A+A/644/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The purpose of this work is to study the properties of the spatial distribution of the young population in three nearby galaxies in order to better understand the first stages of star formation. We used ACS/HST photometry and the "path-linkage criterion" in order to obtain a catalog of young stellar groups (YSGs) in the galaxy NGC 2403. We studied the internal distribution of stars in these YSGs using the Q parameter. We extended these analyses to the YSGs detected in in NGC 300 and NGC 253 our previous works. We built the young stars' density maps for these three galaxies. Through these maps, we were able to identify and study young stellar structures on larger scales. We found 573 YSGs in the galaxy NGC 2403, for which we derived their individual sizes, densities, luminosity function, and other fundamental characteristics. We find that the vast majority of the YSGs in NGC 2403, NGC 300 and NGC 253 present inner clumpings, following the same hierarchical behavior that we observed in the young stellar structures on larger scales in these galaxies. We derived values of the fractal dimension for these structures between ~1.5 and 1.6. These values are very similar to those obtained in other star forming galaxies and in the interstellar medium, suggesting that the star formation process is regulated by supersonic turbulence.
- ID:
- ivo://CDS.VizieR/J/ApJ/727/64
- Title:
- Young stellar groups and their most massive stars
- Short Name:
- J/ApJ/727/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the masses and spatial distributions of 14 young stellar groups in Taurus, Lupus3, ChaI, and IC348. These nearby groups, which typically contain 20-40 members, have membership catalogs complete to ~0.02M_{sun}_, and are sufficiently young that their locations should be similar to where they formed. These groups show five properties seen in clusters having many more stars and much greater surface density of stars: (1) a broad range of masses, (2) a concentration of the most massive star toward the center of the group, (3) an association of the most massive star with a high surface density of lower mass stars, (4) a correlation of the mass of the most massive star with the total mass of the group, and (5) the distribution of a large fraction of the mass in a small fraction of the stars.
