- ID:
- ivo://CDS.VizieR/J/MNRAS/450/3490
- Title:
- 15 new brown dwarfs in Orion OB1a/25 Ori group
- Short Name:
- J/MNRAS/450/3490
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of 15 new brown dwarfs belonging to the ~7Myr old 25 Orionis group and Orion OB1a subassociation with spectral types between M6 and M9 and estimated masses between ~0.07 and ~0.01M_{sun}_. By comparing them through a Bayesian method with low-mass stars (0.8<~M/M_{sun}_ <~0.1) from previous works in the 25 Orionis group, we found statistically significant differences in the number fraction of classical T Tauri stars, Weak T Tauri stars, class II, evolved discs and purely photospheric emitters at both sides of the substellar mass limit. Particularly, we found a fraction of 3.9^+2.4^_-1.6_ percent low-mass stars classified as Classic T Tauri star and class II or evolved discs, against a fraction of 33.3^+10.8^_-9.8_ percent in the substellar mass domain. Our results support the suggested scenario in which the dissipation of discs is less efficient for decreasing mass of the central object.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/418/1231
- Title:
- New brown dwarfs in upper Sco
- Short Name:
- J/MNRAS/418/1231
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the results of a search for brown dwarfs in the Upper Scorpius Association using data from the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Cluster Survey. Candidate young brown dwarfs were first chosen by their position in colour magnitude diagrams with further selection based on proper motions to ensure Upper Scorpius membership. Proper motions were derived by comparing UKIDSS and Two Micron All Sky Survey (2MASS) data. Using that method we identify 19 new brown dwarfs in the southern part of the association. In addition there are up to eight likely members with slightly higher dispersion velocity. The ratio of brown dwarfs to stars was found to be consistent with other areas in Upper Scorpius. It was also found to be similar to other results from young clusters with OB associations, and lower than those without, suggesting the brown dwarf formation rate may be a function of environment.
- 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_).
- ID:
- ivo://CDS.VizieR/J/A+A/635/A14
- Title:
- New R Coronae Borealis stars
- Short Name:
- J/A+A/635/A14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue contains 2356 entries. It was created to list targets of interest that have similar near- and mid-infrared characteristics than R Coronae Borealis (RCB) stars which are hydrogen-deficient carbon-rich supergiant stars known to possess warm circumstellar shells. It is therefore a catalogue enriched in such objects and further spectroscopic follow-ups are needed to reveal the true nature of each target. The catalogue was produced from a series of selection criteria on the infrared colours and brightness of sources published in the WISE All-Sky data release, and also listed in the 2MASS catalogue. These sources spread over the entire sky. The selection criteria are described in section 2 of the paper.
- ID:
- ivo://CDS.VizieR/J/A+A/497/619
- Title:
- New ultra-cool dwarfs from SDSS and 2MASS
- Short Name:
- J/A+A/497/619
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We try to identify ultra-cool dwarfs from the seventh Data Release of the Sloan Digital Sky Survey (SDSS DR7) with SDSS i-z and r-z colors. We also obtain proper motion data from SDSS, 2MASS, and UKIDSS and improve spectral typing from SDSS and 2MASS photometric colors.
- ID:
- ivo://CDS.VizieR/J/A+A/598/A92
- Title:
- New ultracool subdwarfs
- Short Name:
- J/A+A/598/A92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We developed an efficient method to search for late-type subdwarfs. We carried out a search cross-matching SDSS, 2MASS, and UKIDSS with VO tools. We considered different photometric and proper motion criteria for our selection. We identified 100 late-type subdwarf candidates. We obtained our own low-resolution optical spectra for 71 of our candidates and retrieved Sloan spectra for 30 of them (9 in common to the 71). We classified 92 candidates based on optical spectra. Our new discoveries include 49 subdwarfs, 25 extreme subdwarfs, six ultrasubdwarfs, one subdwarf/extreme subdwarf, and two dwarfs/subdwarfs. In addition, we discovered three early-L subdwarfs. We double the numbers of cool subdwarfs and derived a surface density of late-type subdwarfs.
- 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/A+A/417/651
- Title:
- NEXXUS ROSAT survey of coronal X-ray
- Short Name:
- J/A+A/417/651
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a final summary of all ROSAT X-ray observations of nearby stars. All available ROSAT observations with the ROSAT PSPC, HRI and WFC have been matched with the CNS4 catalog of nearby stars and the results gathered in the NEarby X-ray and XUV-emitting Stars (NEXXUS) data base. New volume-limited samples of F/G-stars (table 1), K-stars (table 2), and M-stars (table 3) are constructed within which detection rates of more than 90% are obtained.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A16
- Title:
- NGC 6774 cool stars rotation periods
- Short Name:
- J/A+A/644/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gyrochronology allows the derivation of ages for cool main sequence stars based on their observed rotation periods and masses, or a suitable proxy thereof. It is increasingly well-explored for FGK stars, but requires further measurements for older ages and K-M-type stars. We study the 2.7Gyr-old open cluster Ruprecht 147 to compare it with the previously-studied, but far more distant, NGC 6819 cluster, and especially to measure cooler stars than was previously possible there. We constructed an inclusive list of 102 cluster members from prior work, including Gaia DR2, and for which light curves were also obtained during Campaign 7 of the Kepler/K2 space mission. We placed them in the cluster color-magnitude diagram and checked the related information against appropriate isochrones. The light curves were then corrected for data systematics using Principal Component Analysis on all observed K2 C07 stars and subsequently subjected to periodicity analysis. Periodic signals are found for 32 stars, 21 of which are considered to be both highly reliable and to represent single, or effectively single, Ru 147 stars. These stars cover the spectral types from late-F to mid-M stars, and they have periods ranging from 6d-33d, allowing for a comparison of Ruprecht 147 to both other open clusters and to models of rotational spindown. The derived rotation periods connect reasonably to, overlap with, and extend to lower masses the known rotation period distribution of the 2.5 Gyr-old cluster NGC 6819. The data confirm that cool stars lie on a single surface in rotation period-mass-age space, and they simultaneously challenge its commonly assumed shape. The shape at the low mass region of the color-period diagram at the age of Ru 147 favors a recently-proposed model which requires a third mass-dependent timescale in addition to the two timescales required by a former model, suggesting that a third physical process is required to model rotating stars effectively.
- ID:
- ivo://CDS.VizieR/J/MNRAS/420/2884
- Title:
- NGC 1960 IRAC and MIPS photometry
- Short Name:
- J/MNRAS/420/2884
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of Spitzer IRAC (3.6-8um) and MIPS (24um) imaging of members of the 16^+10^_-5_ Myr old open cluster NGC 1960 (M36). Models of terrestrial planet formation indicate that rocky planets are likely to achieve their final masses at around 10-30Myr, and thus this cluster is at an interesting epoch for planet formation. We find 21 B-F5 type stars and 14 F6-K9 type stars which have 24um excess emission, and thus determine that >30 per cent of B-F5 type stars and >23 per cent of F6-K9 type stars in this cluster have 24um excess emission. These excess frequencies are similar to those observed in other clusters of similar age. Three early-type stars have excesses at near-infrared wavelengths. Analysis of their spectral energy distributions confirms that these are true debris discs and not remnant primordial or transitional discs. None of the 61 Sun-like stars has confirmed near-infrared excess, and we can place a limit on the frequency of 8um excess emission around Sun-like stars of <7 per cent. All of the detected excesses are consistent with emission from debris discs and are not primordial.
