Number of results to display per page
Search Results
4312. New ultracool subdwarfs
- 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/other/NewA/49.50
- Title:
- New Variables in 3 Galactic open clusters
- Short Name:
- J/other/NewA/49.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This project is a massive near-infrared (NIR) search for variable stars in highly reddened and obscured open cluster (OC) fields projected on regions of the Galactic bulge and disk. The search is performed using photometric NIR data in the J-, H- and Ks - bands obtained from the Vista Variables in the Via Lactea (VVV) Survey. We performed in each cluster field a variability search using Stetson's variability statistics to select the variable candidates. Later, those candidates were subjected to a frequency analysis using the Generalized Lomb-Scargle and the Phase Dispersion Minimization algorithms. The number of independent observations range between 63 and 73. The newly discovered variables in this study, 157 in total in three different known OCs, are classified based on their light curve shapes, periods, amplitudes and their location in the corresponding color-magnitude (J-Ks,Ks)(J-Ks,Ks) and color-color (H-Ks,J-H)(H-Ks,J-H) diagrams. We found 5 possible Cepheid stars which, based on the period-luminosity relation, are very likely type II Cepheids located behind the bulge. Among the newly discovered variables, there are eclipsing binaries, {delta} Scuti, as well as background RR Lyrae stars. Using the new version of the Wilson & Devinney code as well as the "Physics Of Eclipsing Binaries" (PHOEBE) code, we analyzed some of the best eclipsing binaries we discovered. Our results show that these studied systems turn out to be ranging from detached to double-contact binaries, with low eccentricities and high inclinations of approximately 80{deg}. Their surface temperatures range between 3500K and 8000K.
- ID:
- ivo://CDS.VizieR/J/other/IBVS/6137
- Title:
- New variables in M5 (NGC 5904)
- Short Name:
- J/other/IBVS/613
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report twelve variables not previously detected in the globular cluster M5 (NGC 5904); one SX Phe and eleven semi-regular variables (SR). Their identifications, equatorial coordinates, ephemerides, and light curves are given. Furthermore, we have explored the light curves of a group of stars whose variability has not been confirmed and that are marked as probable non-variables in the CVSGC. Finally, we offer detailed identifications for some of the known variables in crowded regions that were misidentified in previous studies. We shall also address the cases of the cataclysmic variable or U Gem type V101 and of the variable blue straggler V159.
4315. New variables in ONC
- ID:
- ivo://CDS.VizieR/J/MNRAS/400/603
- Title:
- New variables in ONC
- Short Name:
- J/MNRAS/400/603
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Since 2004, we have been engaged in a long-term observing programme to monitor young stellar objects (YSOs) in the Orion Nebula Cluster (ONC). We have collected about 2000 frames in V, R and I broad-band filters on more than 200 nights distributed over five consecutive observing seasons. The high-quality and time-extended photometric data give us an opportunity to address various phenomena associated with young stars.
- ID:
- ivo://CDS.VizieR/J/AZh/91/382
- Title:
- New variable stars in field SA9
- Short Name:
- J/AZh/91/382
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The new stage of work on digitizing the astronomical plates of the Sternberg Astronomical Institute's collection and searching for new variable stars using the digitized photographic plates includes a considerable improvement of the automated search techniques for objects with variable brightnesses. In particular, the technique for taking into account the non-linear response of the photographic light detector has been improved. Applying the improved techniques to 182 digitized images of a 10{deg}x10{deg} field centered at SA9, obtained from scanning photographic plates taken with the Sternberg Astronomical Institute 40-cm astrograph, has enabled the discover and study of 77 new variable stars (MDV 519-595). These include 3 Cepheids, 2 probableBY Draconis stars, 65 eclipsing binaries, 3RR Lyrae stars, 1 high-amplitude {delta} Scuti star (HADS), and 3 irregular variables. Special CCD observations have confirmed the presence of brightness variations in 7 of the 77 variables that were initially considered uncertain.
- ID:
- ivo://CDS.VizieR/J/other/RAA/18.92
- Title:
- New variable stars in 104 Her field
- Short Name:
- J/other/RAA/18.9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using 172 plates taken with the 40-cm astrograph of the Sternberg Astronomical Institute (Lomonosov Moscow University) in 1976-1994 and digitized with a resolution of 2400 dpi, we discovered and studied 275 new variable stars. We present the list of our new variables with all necessary information concerning their brightness variations. As in our earlier studies, the new discoveries show a rather large number of high-amplitude Delta Scuti variables, predicting that many stars of this type remain not detected in the whole sky. We also performed automated classification of the newly discovered variable stars based on the Random Forest algorithm. The results of the automated classification were compared to traditional classification and showed that automated classification was possible even with noisy photographic data. However, further improvement of automated techniques is needed, which is especially important when considering the very large numbers of new discoveries expected from all-sky surveys.
- ID:
- ivo://CDS.VizieR/J/other/RMxAA/44.365
- Title:
- New variable stars in NGC 6366
- Short Name:
- J/other/RMxAA/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New CCD photometry of NGC 6366 has lead to the discovery of some variable stars. Two possible Anomalous Cepheids (or Pop II Cepheids), three long period variables, one SX Phe and one eclipsing binary have been found. Also a list of 10 candidate variables is reported. The light curve of the RRab star, V1, has been decomposed into its Fourier harmonics, and the Fourier parameters were used to estimate the star's metallicity and distance; [Fe/H]=-0.87+/-0.14 and d=3.2+/-0.1kpc. It is argued that V1 may not be a member of the cluster but rather a more distant object. If this is so, an upper limit for the distance to the cluster of 2.8+/-0.1kpc can be estimated. The P-L relationship for SX Phe stars and the identified modes in the newly discovered SX Phe variable, V6, allow yet another independent determination of the distance to the cluster of d=2.7+/-0.1kpc. The M_V_-[Fe/H] relationship for RR Lyrae stars is addressed and the case of V1 is discussed.
- ID:
- ivo://CDS.VizieR/J/AZh/87/1087
- Title:
- New variable stars in 66 Oph field
- Short Name:
- J/AZh/87/1087
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the course of a program to digitize the astronomical plates of the Sternberg Astronomical Institute's plate stacks, we are developing algorithms for searching for new variable stars and studying them using digitized photographic plates. We have discovered and studied 480 new variable stars in a 10{deg}x10{deg} field of view centered on 66 Ophiuchi. The digitized plate negatives used are from the 40-cm astrograph, and are 30x30cm in size. These stars include three new Cepheids of the Galaxy's spherical component, 157 eclipsing binaries, 11 high-amplitude {delta} Scuti stars (HADSs), 144 RR Lyrae stars, 110 irregular variables (109 LB and one white star), and 55 semi-regular red variables.
- ID:
- ivo://CDS.VizieR/J/A+AS/49/715
- Title:
- New variable stars in Sgr B
- Short Name:
- J/A+AS/49/715
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 621 new variable stars have been detected on plates obtained with the Schmidt telescopes of the Mount Palomar Observatory (1968) and of the European Southern Observatory (1976-1980). The astrometric measurements (ESO-CERN) and the photometrical ones (CDCA) which have followed the detection the variable stars (Observatoire de Lyon) have led to determine the parameters {alpha}, {delta}, l, b, R(Max), R(Min), {delta}m. So we notice that: - 379 variable stars have an amplitude of variation in magnitude between 0.5 and 2.0 (delm/N histogram). -The number of variable stars strongly decreases towards the great amplitudes. -The surface density of variable stars by square degree in this central galactic direction increases from 2 to 21 in the explored field of 5.5degx5.5deg size.
