- 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/AJ/143/84
- Title:
- New candidate globular clusters in NGC 5128
- Short Name:
- J/AJ/143/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used new wide-field imaging with the Magellan IMACS camera to search for globular cluster (GC) candidates around NGC 5128, the nearest giant E galaxy. The imaging data are in the B and R broadband filters and cover a 1.55 deg^2^ field centered on the galaxy, corresponding to an area about 90*90kpc^2^ at the distance of NGC 5128. All the fields were taken under exceptionally high-quality seeing conditions (FWHM=0.4-0.5" in R). Using this material we are able, for the first time in the literature, to construct a homogeneous list of GC candidates covering a wide span of the NGC 5128 halo and unusually free of field contaminants (foreground stars and faint background galaxies). Selecting the measured objects by color, magnitude, ellipticity, and profile size gives us a final catalog of 833 new high-quality GC candidates brighter than R=21 (0.8mag fainter than the standard GC luminosity function turnover point). The measured positions have better than 0.2" precision in both coordinates.
- ID:
- ivo://CDS.VizieR/J/other/RAA/15.1671
- Title:
- New carbon stars from LAMOST survey
- Short Name:
- J/other/RAA/15.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon stars are excellent kinematic tracers of galaxies and can serve as a viable standard candle, so it is worthwhile to automatically search for them in a large amount of spectra. In this paper, we apply the efficient manifold ranking algorithm to search for carbon stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) pilot survey, whose performance and robustness are verified comprehensively with four test experiments. Using this algorithm, we find a total of 183 carbon stars, and 158 of them are new findings. According to different spectral features, our carbon stars are classified as 58 C-H stars, 11 C-H star candidates, 56 C-R stars, ten C-R star candidates, 30 C-N stars, three C-N star candidates, and four C-J stars. There are also ten objects which have no spectral type because of low spectral quality, and a composite spectrum consisting of a white dwarf and a carbon star. Applying the support vector machine algorithm, we obtain the linear optimum classification plane in the J-H versus H-Ks color diagram which can be used to distinguish C-H from C-N stars with their J-H and H-Ks colors. In addition, we identify 18 dwarf carbon stars with their relatively high proper motions, and find three carbon stars with FUV detections likely have optical invisible companions by cross matching with data from the Galaxy Evolution Explorer. In the end, we detect four variable carbon stars with the Northern Sky Variability Survey, the Catalina Sky Survey and the LINEAR variability databases. According to their periods and amplitudes derived by fitting light curves with a sinusoidal function, three of them are likely semiregular variable stars and one is likely a Mira variable star.
- ID:
- ivo://CDS.VizieR/J/AJ/156/90
- Title:
- New catalog of APOGEE radial velocity standard stars
- Short Name:
- J/AJ/156/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalog of 18080 radial velocity (RV) standard stars selected from the APOGEE data. These RV standard stars are observed at least three times and have a median stability (3{sigma}_RV_) around 240 m/s over a time baseline longer than 200 days. They are largely distributed in the northern sky and could be extended to the southern sky by the future APOGEE-2 survey. Most of the stars are red giants (J-K_s_>=0.5) owing to the APOGEE target selection criteria. Only about 10 per cent of them are main-sequence stars. The H-band magnitude range of the stars is 7-12.5 mag with the faint limit much fainter than the magnitudes of previous RV standard stars. As an application, we show the new set of standard stars to determine the RV zero points of the RAVE, the LAMOST, and the Gaia-RVS Galactic spectroscopic surveys.
- ID:
- ivo://CDS.VizieR/J/AJ/150/27
- Title:
- New catalog of variable stars in M37 field
- Short Name:
- J/AJ/150/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive re-analysis of stellar photometric variability in the field of the open cluster M37 following the application of a new photometry and de-trending method to the MMT/Megacam image archive. This new analysis allows a rare opportunity to explore photometric variability over a broad range of timescales, from minutes to a month. The intent of this work is to examine the entire sample of more than 30000 objects for periodic, aperiodic, and sporadic behaviors in their light curves. We show a modified version of the fast {chi}^2^ periodogram algorithm (F{chi}^2^) and change-point analysis as tools for detecting and assessing the significance of periodic and non-periodic variations. The benefits of our new photometry and analysis methods are evident. A total of 2306 stars exhibit convincing variations that are induced by flares, pulsations, eclipses, starspots, and unknown causes in some cases. This represents a 60% increase in the number of variables known in this field. Moreover, 30 of the previously identified variables are found to be false positives resulting from time-dependent systematic effects. The new catalog includes 61 eclipsing binary systems, 92 multiperiodic variable stars, 132 aperiodic variables, and 436 flare stars, as well as several hundreds of rotating variables. Based on extended and improved catalog of variables, we investigate the basic properties (e.g., period, amplitude, type) of all variables. The catalog can be accessed through the web interface (http://stardb.yonsei.ac.kr/).
- ID:
- ivo://CDS.VizieR/J/MNRAS/383/831
- Title:
- New DENIS nearby L and late-M dwarfs
- Short Name:
- J/MNRAS/383/831
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on new nearby L and late-M dwarfs (d_phot_<=30pc) discovered in our search for nearby ultracool dwarfs (I-J>=3.0, later than M8.0) in the Galactic plane (|b|<15{deg}) over 4800 deg^2^ in the Deep Near Infrared Survey of t he Southern Sky (DENIS) data base. We used late-M (>=M8.0), L and T dwarfs with accurate trigonometric parallaxes to calibrate the M_J_ versus I-J colour-luminosity relation. The resulting photometric distances have standard errors of ~15 per cent, which we used to select candidates dphot <=30pc. We measured proper motions from multi-epoch images found in the public archives ALADIN, DSS, 2MASS and DENIS, with at least three distinct epochs and time baselines of 10-21yr. We then used the Maximum Reduced Proper Motion method to select 28 candidates as ultracool dwarfs (M8.0-L8.0) and to reject one as a distant red star. Our low-resolution optical spectra confirmed that 26 were indeed ultracool dwarfs, with spectral types from M8.0 to L5.5. Two contaminants and one rejected by the maximum reduced proper motion cut-off were all reddened F-K main sequence stars. 20 of these 26 ultracool dwarfs are new nearby ultracool dwarf members, three L dwarfs within 15pc with one L3.5 at only ~10pc.
- ID:
- ivo://CDS.VizieR/J/ApJS/206/9
- Title:
- New EGOs from Spitzer GLIMPSE II survey. I.
- Short Name:
- J/ApJS/206/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have produced a catalog containing 98 newly identified massive young stellar object (MYSO) candidates associated with ongoing outflows (known as extended green objects, or EGOs). These have been identified from the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) II data set and our new identifications increase the number of known EGOs to ~400 in our Galaxy, adding to the ~300 previously identified EGOs reported by Cyganowski et al. (2008, Cat. J/AJ/136/2391) from the GLIMPSE I survey. The high detection rate (~70%) of 95 GHz class I methanol masers achieved in a survey toward 57 of these new EGOs with the Mopra 22m radio telescope demonstrates that the new EGOs are associated with outflows. Investigations of the mid-infrared properties and physical associations with other star formation tracers (e.g., infrared dark clouds, class I and II methanol masers, and millimeter Bolocam Galactic Plane Survey sources) reveal that the newly identified EGOs are very similar in nature to those in the sample of Cyganowski et al. All of the observational evidence supports the hypothesis that EGOs correspond to MYSOs at the earliest evolutionary stage, with ongoing outflow activity, and active rapid accretion.
- ID:
- ivo://CDS.VizieR/J/ApJ/735/86
- Title:
- NEWFIRM MBS: photometric catalogs
- Short Name:
- J/ApJ/735/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep near-IR (NIR) medium-bandwidth photometry over the wavelength range 1-1.8um in the All-wavelength Extended Groth strip International Survey (AEGIS) and Cosmic Evolution Survey (COSMOS) fields. The observations were carried out using the NOAO Extremely Wide-Field Infrared Imager (NEWFIRM) on the Mayall 4m Telescope on Kitt Peak as part of the NEWFIRM Medium-Band Survey (NMBS), an NOAO survey program. In this paper, we describe the full details of the observations, data reduction, and photometry for the survey. We also present a public K-selected photometric catalog, along with accurate photometric redshifts. The redshifts are computed with 37 (20) filters in the COSMOS (AEGIS) fields, combining the NIR medium-bandwidth data with existing UV (Galaxy Evolution Explorer), visible and NIR (Canada-France-Hawaii Telescope and Subaru Telescope), and mid-IR (Spitzer/IRAC) imaging. We find excellent agreement with publicly available spectroscopic redshifts, with {sigma}_z_/(1+z)~1%-2% for ~4000 galaxies at z=0-3. The NMBS catalogs contain ~13000 galaxies at z>1.5 with accurate photometric redshifts and rest-frame colors. Due to the increased spectral resolution obtained with the five NIR medium-band filters, the median 68% confidence intervals of the photometric redshifts of both quiescent and star-forming galaxies are a factor of about two times smaller when comparing catalogs with medium-band NIR photometry to NIR broadband photometry.
- ID:
- ivo://CDS.VizieR/J/A+A/532/A131
- Title:
- New Galactic star clusters in VVV survey
- Short Name:
- J/A+A/532/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- VISTA Variables in the Via Lactea (VVV) is one of the six ESO Public Surveys operating on the new 4-meter Visible and Infrared Survey Telescope for Astronomy (VISTA). VVV is scanning the Milky Way bulge and an adjacent section of the disk, where star formation activity is high. One of the principal goals of the VVV Survey is to find new star clusters of different ages. In order to trace the early epochs of star cluster formation we concentrated our search in the directions to those of known star formation regions, masers, radio, and infrared sources. The disk area covered by VVV was visually inspected using the pipeline processed and calibrated KS-band tile images for stellar overdensities. Subsequently, we examined the composite JHKS and ZJKS color images of each candidate. PSF photometry of 15x15arcmin fields centered on the candidates was then performed on the Cambridge Astronomy Survey Unit reduced images. After statistical field-star decontamination, color-magnitude and color-color diagrams were constructed and analyzed.
