Search

Start Over Subject photometry
4251. New brown dwarfs in upper Sco
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.
4252. New candidate globular clusters in NGC 5128
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.
4253. New candidate members in young associations
ID:
ivo://CDS.VizieR/J/A+A/590/A13
Title:
New candidate members in young associations
Short Name:
J/A+A/590/A13
Date:
21 Oct 2021
Publisher:
CDS
Description:
The young associations offer us one of the best opportunities to study the properties of young stellar and sub-stellar objects and directly image planets thanks to their proximity (<200pc) and age (5-150Myr). However, many previous works have been limited to identifying the brighter, more active members (1Msun) due to photometric survey sensitivities limiting the detections of lower-mass objects. We search the field of view of 542 previously identified members of the young associations to identify wide / extremely wide (1000-100,000au in physical separation) companions. Methods. We have combined 2MASS near-infrared photometry (J, H, K) with proper motion values (from UCAC4, PPMXL, NOMAD) to identify companions in the field of view of known members. We collated further photometry and spectroscopy from the literature and conducted our own high-resolution spectroscopic observations for a sub-sample of candidate members. This complementary information allowed us to assess the efficiency of our method. We identified 84 targets (45:0.2-1.3M_{sun}_, 17:0.08-0.2M_{sun}_, 22:<0.08M_{sun}_) in our analysis, 10 of which have been identified from spectroscopic analysis in previous young association works. For 33 of these 84 we were able to further assess their membership using a variety of properties (X-ray emission, UV excess, H{alpha}, lithium and KI equivalent widths, radial velocities, and CaH indices). We derive a success rate of 76-88% for this technique based on the consistency of these properties. Once confirmed, the targets identified in this work would significantly improve our knowledge of the lower-mass end of the young associations. Additionally, these targets would make an ideal new sample for the identification and study of planets around nearby young stars. Given the predicted sub-stellar mass of the majority of these new candidate members and their proximity, high-contrast imaging techniques would facilitate the search for new low-mass planets.
4254. New carbon stars from LAMOST survey
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.
4255. New catalog of APOGEE radial velocity standard stars
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.
4256. New catalog of variable stars in M37 field
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/).
4257. New close binary systems from the SDSS DR5
ID:
ivo://CDS.VizieR/J/AJ/134/741
Title:
New close binary systems from the SDSS DR5
Short Name:
J/AJ/134/741
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the latest catalog of more than 1200 spectroscopically selected close binary systems observed with the Sloan Digital Sky Survey through Data Release Five. We use the catalog to search for magnetic white dwarfs in cataclysmic variable progenitor systems. Given that approximately 25% of cataclysmic variables contain a magnetic white dwarf, and that our large sample of close binary systems should contain many progenitors of cataclysmic variables, it is quite surprising that we find only two potential magnetic white dwarfs in this sample.
4258. New companions to nearby low-mass stars
ID:
ivo://CDS.VizieR/J/MNRAS/429/859
Title:
New companions to nearby low-mass stars
Short Name:
J/MNRAS/429/859
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present high-angular-resolution optical I-band imaging of 451 late K to mid-M nearby stars. These observations have been performed with Astralux and FastCam using the lucky imaging technique. We found 70 companions with separations between 0.1 and 3.5-arcsec, out of which 28 are new discoveries. We derive a total binary fraction of 20.3^+6.9^_-5.2_ per cent. Follow-up observations have been carried out for 16 of these new binaries and all of them were confirmed as physically associated systems. Parallaxes are available for 70 per cent of the binary sample, providing reliable estimates of physical separations. We have measured separations and position angles as an initial stage for a systematic follow-up aimed to determine orbital parameters.
4259. New DENIS nearby L and late-M dwarfs
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.
4260. New Dwarf novae in SDSS, GALEX and astrom. cat.
ID:
ivo://CDS.VizieR/J/MNRAS/402/436
Title:
New Dwarf novae in SDSS, GALEX and astrom. cat.
Short Name:
J/MNRAS/402/436
Date:
21 Oct 2021
Publisher:
CDS
Description:
By cross-matching blue objects from the Sloan Digital Sky Survey with Galaxy Evolution Explorer and the astrometric catalogues USNO-B1.0, GSC2.3 and CMC14, 64 new dwarf nova candidates with one or more observed outbursts have been identified. 14 of these systems are confirmed as cataclysmic variables through existing and follow-up spectroscopy. A study of the amplitude distribution and an estimate of the outburst frequency of these new dwarf novae and those discovered by the Catalina Real-time Transient Survey indicate that besides systems that are faint because they are farther away, there also exists a population of intrinsically faint dwarf novae with rare outbursts.