Search

Start Over Subject optical astronomy
2311. New globular clusters in M 31
ID:
ivo://CDS.VizieR/J/AJ/134/706
Title:
New globular clusters in M 31
Short Name:
J/AJ/134/706
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the result of a wide-field survey of globular clusters (GCs) in M31 covering a 3{deg}x3{deg} field centered on M31. We have searched for GCs on CCD images taken with Washington CMT1 filters at the KPNO 0.9m telescope using the following steps: (1) inspection of morphological parameters given by the SExtractor package such as stellarity, full width at half-maximum, and ellipticity; (2) consulting the spectral types and radial velocities obtained from spectra taken with the Hydra spectrograph at the WIYN 3.5m telescope; and (3) visual inspection of the images of each object. We have found 1164 GCs and GC candidates, of which 605 are newly found GCs and GC candidates and 559 are previously known GCs. Among the new objects there are 113 genuine GCs, 258 probable GCs, and 234 possible GCs, according to our classification criteria. Among the known objects there are 383 genuine GCs, 109 probable GCs, and 67 possible GCs. In total there are 496 genuine GCs, 367 probable GCs, and 301 possible GCs. Most of these newly found GCs have T1 magnitudes of 17.5-19.5mag [17.9<V<19.9mag assuming (C-T1)~1.5], and (C-T1) colors in range 1-2.
2312. New HIP-based parallaxes for 424 faint stars
ID:
ivo://CDS.VizieR/J/ApJS/150/455
Title:
New HIP-based parallaxes for 424 faint stars
Short Name:
J/ApJS/150/455
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of 424 common proper-motion companions to Hipparcos stars with good (>3{sigma}) parallaxes, thereby effectively providing new parallaxes for these companions. Compared with typical stars in the Hipparcos catalog, these stars are substantially dimmer. The catalog includes 20 white dwarfs and an additional 29 stars with M_V_>14, the great majority of the latter being M dwarfs.
2313. New hot subdwarf stars
ID:
ivo://CDS.VizieR/J/MNRAS/457/3396
Title:
New hot subdwarf stars
Short Name:
J/MNRAS/457/3396
Date:
21 Oct 2021
Publisher:
CDS
Description:
Recent massive sky surveys in different bandwidths are providing new opportunities to modern astronomy. The Virtual Observatory (VO) represents the adequate framework to handle the huge amount of information available and filter out data according to specific requirements. In this work, we applied a selection strategy to find new, uncatalogued hot subdwarfs making use of VO tools. We used large area catalogues like GALEX, Sloan Digital Sky Survey (SDSS), SuperCosmos and Two Micron All Sky Survey (2MASS) to retrieve photometric and astrometric information of stellar objects. To these objects, we applied colour and proper motion filters, together with an effective temperature cutoff, aimed at separating hot subdwarfs from other blue objects such as white dwarfs, cataclysmic variables or main-sequence OB stars. As a result, we obtained 437 new, uncatalogued hot subdwarf candidates. Based on previous results, we expect our procedure to have an overall efficiency of at least 80 per cent. Visual inspection of the 68 candidates with SDSS spectrum showed that 65 can be classified as hot subdwarfs: 5 sdOs, 25 sdOBs and 35 sdBs. This success rate above 95 per cent proves the robustness and efficiency of our methodology. The spectral energy distribution of 45 per cent of the subdwarf candidates showed infrared excesses, a signature of their probable binary nature. The stellar companions of the binary systems so detected are expected to be late-type main-sequence stars. A detailed determination of temperatures and spectral classification of the cool companions will be presented in a forthcoming work.
2314. New L and T dwarfs from the SDSS
ID:
ivo://CDS.VizieR/J/AJ/131/2722
Title:
New L and T dwarfs from the SDSS
Short Name:
J/AJ/131/2722
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present near-infrared observations of 71 newly discovered L and T dwarfs, selected from imaging data of the Sloan Digital Sky Survey (SDSS) using the i-dropout technique. Sixty-five of these dwarfs have been classified spectroscopically according to the near-infrared L dwarf classification scheme of Geballe et al. (2002ApJ...564..466G) and the unified T dwarf classification scheme of Burgasser et al. (2006, Cat. <J/ApJ/637/1067>). The spectral types of these dwarfs range from L3 to T7 and include the latest types yet found in the SDSS. Six of the newly identified dwarfs are classified as early to mid-L dwarfs according to their photometric near-infrared colors, and two others are classified photometrically as M dwarfs. We also present new near-infrared spectra for five previously published SDSS L and T dwarfs, and one L dwarf and one T dwarf discovered by Burgasser et al. (2006, Cat. <J/ApJ/637/1067>) from the Two Micron All Sky Survey. The new SDSS sample includes 27 T dwarfs and 30 dwarfs with spectral types spanning the complex L-T transition (L7-T3).
2315. Newly identified star clusters in Gaia DR2
ID:
ivo://CDS.VizieR/J/ApJS/245/32
Title:
Newly identified star clusters in Gaia DR2
Short Name:
J/ApJS/245/32
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the Star cluster Hunting Pipeline (SHiP) that can identify star clusters in Gaia second data release (DR2) data and establish a star cluster catalog for the Galactic disk. A friend-of-friend-based cluster finder method is used to identify star clusters using five-dimensional stellar parameters, l,b,{omega},{mu}_{alpha}_cos{delta}, and {mu}_{delta}_. Our new catalog contains 2443 star cluster candidates identified from disk stars located within |b|=25{deg} and with G<18mag. An automatic isochrone fitting scheme is applied to all cluster candidates. With a combination of parameters obtained from isochrone fitting, we classify cluster candidates into three classes (Class 1, 2, and 3). Class 1 clusters are the most probable star cluster candidates with the most stringent criteria. Most of these clusters are nearby (within 4kpc). Our catalog is crossmatched with three Galactic star cluster catalogs, Kharchenko+ (2013, J/A+A/558/A53), Cantat-Gaudin+ (2018, J/A+A/618/A93 and 2019, J/A+A/624/A126), and Bica+ (2019, J/AJ/157/12). The proper motion and parallax of matched star clusters are in good agreement with these earlier catalogs. We discover 76 new star cluster candidates that are not listed in these three catalogs. The majority of these are clusters older than log(age/yr)=8.0 and are located in the inner disk with |b|<5{deg}. The recent discovery of new star clusters suggests that current Galactic star cluster catalogs are still incomplete. Among the Class 1 cluster candidates, we find 56 candidates for star cluster groups.
2316. Newly rich galaxy clusters identified in SDSS-DR12
ID:
ivo://CDS.VizieR/J/ApJ/807/178
Title:
Newly rich galaxy clusters identified in SDSS-DR12
Short Name:
J/ApJ/807/178
Date:
21 Oct 2021
Publisher:
CDS
Description:
Accurately determining the mass of galaxy clusters is fundamental for many studies of cosmology and galaxy evolution. We collect and rescale the cluster masses of 1191 clusters of 0.05<z<0.75 estimated by X-ray or Sunyaev-Zeldovich measurements and use them to calibrate the optical mass proxy. The total r-band luminosity (in units of L*) of these clusters is obtained by using spectroscopic and photometric data of the Sloan Digital Sky Survey (SDSS). We find that the correlation between the cluster mass M_500_ and total r-band luminosity L_500_ significantly evolves with redshift. After correcting for the evolution, we define a new cluster richness R_L*,500_=L_500_E(z)^1.40^ as the optical mass proxy. By using this newly defined richness and the recently released SDSS DR12 spectroscopic data, we update the WHL12 (Wen et al. 2012, J/ApJS/199/34) cluster catalog and identify 25419 new rich clusters at high redshift. In the SDSS spectroscopic survey region, about 89% of galaxy clusters have spectroscopic redshifts. The mass can be estimated with a scatter of 0.17dex for the clusters in the updated catalog.
2317. New members of Cygnus OB2 from Gaia DR2
ID:
ivo://CDS.VizieR/J/MNRAS/502/6080
Title:
New members of Cygnus OB2 from Gaia DR2
Short Name:
J/MNRAS/502/6080
Date:
21 Oct 2021
Publisher:
CDS
Description:
Due to the high quality of Gaia DR2 stellar parallaxes and proper motions, we can study the Cygnus OB2 region up to G=17.5mag in circular region centred at (l,b)=(79.8{deg},+0.8{deg}) of radius 1{deg}. We detect four over-densities in the Vector Point Diagram. We apply a parametric model of the proper motion distribution and determine their mean proper motions, identify their members and estimate their distances by analyzing the parallaxes of the most probable members. We confirm that one of these regions is Cygnus OB2, whose mean proper motion is (pmRA*cosDE,pmDE)=(-2.71+/-0.02,-4.24+/-0.02)mas/yr. We identify 2767 astrometric members at an estimated distance of 1683 {+/-} 5 pc. A detailed comparison of these members with 333 photometric and spectroscopic Cygnus OB2 members shows that 33 stars of the last group are not members, 16 of them are O-B stars. 300 members in common lead to estimate a distance to the association of 1669+/-6pc. One of the remaining over-densities is the open cluster UCB585 for which we find eight more members, located at ~1460pc. The other two groups count 179 and 188 proper motion members which are distributed throughout the region and situated at a distance of ~1280 pc. The estimated distances of these four groups suggest the existence of different substructures in the Cygnus OB2 region along the line of sight.
2318. New minima timings and RVs for 3 eclipsing binaries
ID:
ivo://CDS.VizieR/J/AJ/153/36
Title:
New minima timings and RVs for 3 eclipsing binaries
Short Name:
J/AJ/153/36
Date:
21 Oct 2021
Publisher:
CDS
Description:
Eclipsing binaries remain crucial objects for our understanding of the universe. In particular, those that are components of multiple systems can help us solve the problem of the formation of these systems. Analysis of the radial velocities together with the light curve produced for the first time precise physical parameters of the components of the multiple systems V773 Cas, QS Aql, and BR Ind. Their visual orbits were also analyzed, which resulted in slightly improved orbital elements. What is typical for all these systems is that their most dominant source is the third distant component. The system V773 Cas consists of two similar G1-2V stars revolving in a circular orbit and a more distant component of the A3V type. Additionally, the improved value of parallax was calculated to be 17.6 mas. Analysis of QS Aql resulted in the following: the inner eclipsing pair is composed of B6V and F1V stars, and the third component is of about the B6 spectral type. The outer orbit has high eccentricity of about 0.95, and observations near its upcoming periastron passage between the years 2038 and 2040 are of high importance. Also, the parallax of the system was derived to be about 2.89 mas, moving the star much closer to the Sun than originally assumed. The system BR Ind was found to be a quadruple star consisting of two eclipsing K dwarfs orbiting each other with a period of 1.786 days; the distant component is a single-lined spectroscopic binary with an orbital period of about 6 days. Both pairs are moving around each other on their 148 year orbit.
2319. New OB star candidates in Carina Arm
ID:
ivo://CDS.VizieR/J/MNRAS/450/3855
Title:
New OB star candidates in Carina Arm
Short Name:
J/MNRAS/450/3855
Date:
21 Oct 2021
Publisher:
CDS
Description:
O and early B stars are at the apex of galactic ecology, but in the Milky Way, only a minority of them may yet have been identified. We present the results of a pilot study to select and parametrize OB star candidates in the Southern Galactic plane, down to a limiting magnitude of g=20. A 2 deg^2^ field capturing the Carina Arm around the young massive star cluster, Westerlund 2, is examined. The confirmed OB stars in this cluster are used to validate our identification method, based on selection from the (u-g, g-r) diagram for the region. Our Markov Chain Monte Carlo fitting method combines VPHAS+ u, g, r, i with published J, H, K photometry in order to derive posterior probability distributions of the stellar parameters log(Teff) and distance modulus, together with the reddening parameters A_0_ and R_V_. The stellar parameters are sufficient to confirm OB status while the reddening parameters are determined to a precision of {sigma}(A_0_)~0.09 and {sigma}(R_V_)~0.08. There are 489 objects that fit well as new OB candidates, earlier than ~ B2. This total includes 74 probable massive O stars, 5 likely blue supergiants and 32 reddened subdwarfs. This increases the number of previously known and candidate OB stars in the region by nearly a factor of 10. Most of the new objects are likely to be at distances between 3 and 6 kpc. We have confirmed the results of previous studies that, at these longer distances, these sight lines require non-standard reddening laws with 3.5<R_V_<4.
2320. 570 new open clusters in the Galactic disc
ID:
ivo://CDS.VizieR/J/A+A/635/A45
Title:
570 new open clusters in the Galactic disc
Short Name:
J/A+A/635/A45
Date:
21 Oct 2021
Publisher:
CDS
Description:
Open clusters are key targets for studies of Galaxy structure and evolution, and stellar physics. Since the Gaia data release 2 (DR2), the discovery of undetected clusters has shown that previous surveys were incomplete. Our aim is to exploit the Big Data capabilities of machine learning to detect new open clusters in Gaia DR2, and to complete the open cluster sample to enable further studies of the Galactic disc. We use a machine-learning based methodology to systematically search the Galactic disc for overdensities in the astrometric space and identify the open clusters using photometric information. First, we used an unsupervised clustering algorithm, DBSCAN, to blindly search for these overdensities in Gaia DR2 (l, b, varpi, mu_alpha_*, mu_delta_), then we used a deep learning artificial neural network trained on colour-magnitude diagrams to identify isochrone patterns in these overdensities, and to confirm them as open clusters. We find 570 new open clusters distributed along the Galactic disc in the region |b|<20{deg}. We detect substructure in complex regions, and identify the tidal tails of a disrupting cluster UBC 274 of ~3Gyr located at ~2kpc. Adapting the mentioned methodology to a Big Data environment allows us to target the search using the physical properties of open clusters instead of being driven by computational limitations. This blind search for open clusters in the Galactic disc increases the number of known open clusters by 45%.