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17181. Void Galaxy Survey, photometry and structure
ID:
ivo://CDS.VizieR/J/MNRAS/464/666
Title:
Void Galaxy Survey, photometry and structure
Short Name:
J/MNRAS/464/666
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyse photometry from deep B-band images of 59 void galaxies in the Void Galaxy Survey (VGS), together with their near-infrared 3.6{mu}m and 4.5{mu}m Spitzer photometry. The VGS galaxies constitute a sample of void galaxies that were selected by a geometric-topological procedure from the Sloan Digital Sky Survey Data Release 7 data release, and which populate the deep interior of voids. Our void galaxies span a range of absolute B-magnitude from M_B_=-15.5 to -20, while at the 3.6{mu}m band their magnitudes range from M_3.6_=-18 to -24. Their B-[3.6] colour and structural parameters indicate these are star-forming galaxies. A good reflection of the old stellar population, the near-infrared band photometry also provide a robust estimate of the stellar mass, which for the VGS galaxies we confirm to be smaller than 3x10^10^M_{sun}_. In terms of the structural parameters and morphology, our findings align with other studies in that our VGS galaxy sample consists mostly of small late-type galaxies. Most of them are similar to Sd-Sm galaxies, although a few are irregularly shaped galaxies. The sample even includes two early-type galaxies, one of which is an AGN. Their Sersic indices are nearly all smaller than n=2 in both bands and they also have small half-light radii. In all, we conclude that the principal impact of the void environment on the galaxies populating them mostly concerns their low stellar mass and small size.
17182. Volume-limited sample of cool dwarfs. I. L0-T8 dwarfs
ID:
ivo://CDS.VizieR/J/AJ/161/42
Title:
Volume-limited sample of cool dwarfs. I. L0-T8 dwarfs
Short Name:
J/AJ/161/42
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new volume-limited sample of L0-T8 dwarfs out to 25pc defined entirely by parallaxes, using our recent measurements from UKIRT/WFCAM along with Gaia DR2 and literature parallaxes. With 369 members, our sample is the largest parallax-defined volume-limited sample of L and T dwarfs to date, yielding the most precise space densities for such objects. We find the local L0-T8 dwarf population includes 5.5%{+/-}1.2% young objects (<~200Myr) and 2.6%{+/-}1.6% subdwarfs, as expected from recent studies favoring representative ages <~4Gyr for the ultracool field population. This is also the first volume-limited sample to comprehensively map the transition from L to T dwarfs (spectral types ~L8-T4). After removing binaries, we identify a previously unrecognized, statistically significant (>4.4{sigma}) gap ~0.5mag wide in (J-K)_MKO_ colors in the L/T transition, i.e., a lack of such objects in our volume-limited sample, implying a rapid phase of atmospheric evolution. In contrast, the most successful models of the L/T transition to date-the "hybrid" models of Saumon & Marley-predict a pileup of objects at the same colors where we find a deficit, demonstrating the challenge of modeling the atmospheres of cooling brown dwarfs. Our sample illustrates the insights to come from even larger parallax-selected samples from the upcoming Legacy Survey of Space and Time by the Vera Rubin Obsevatory.
17183. Volume-limited sample of M7-M9.5 dwarfs <20pc
ID:
ivo://CDS.VizieR/J/ApJ/705/1416
Title:
Volume-limited sample of M7-M9.5 dwarfs <20pc
Short Name:
J/ApJ/705/1416
Date:
21 Oct 2021
Publisher:
CDS
Description:
In a volume-limited sample of 63 ultracool dwarfs of spectral type M7-M9.5, we have obtained high-resolution spectroscopy with UVES at the Very Large Telescope and HIRES at Keck Observatory. In this first paper we introduce our volume-complete sample from DENIS and 2MASS targets, and we derive radial velocities and space motion. Kinematics of our sample are consistent with the stars being predominantly members of the young disk. The kinematic age of the sample is 3.1Gyr. We find that six of our targets show strong Li lines implying that they are brown dwarfs younger than several hundred million years. Five of the young brown dwarfs were unrecognized before. Comparing the fraction of Li detections to later spectral types, we see a hint of an unexpected local maximum of this fraction at spectral type M9. It is not yet clear whether this maximum is due to insufficient statistics, or to a combination of physical effects including spectral appearance of young brown dwarfs, Li line formation, and the star formation rate at low masses.
17184. VPDs and CMDs of Berkeley32, Berkeley98 and King23
ID:
ivo://CDS.VizieR/J/AJ/161/102
Title:
VPDs and CMDs of Berkeley32, Berkeley98 and King23
Short Name:
J/AJ/161/102
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using the photometric and kinematical data from Gaia Data Release 2, three old open clusters namely Berkeley32 (Be32), Berkeley98 (Be98), and King23 are investigated. The latter two of these clusters are poorly studied in the literature. The numbers of the most probable cluster members are 563, 260, and 114 for Be32, Be98, and King23, respectively, with membership probabilities higher than 80% and lying within the clusters limiting radii. Mean proper motions (PMs; {mu}_{alpha}_cos_{delta}_ and {mu}_{delta}_) of the clusters are determined as (-0.34{+/-}0.008, -1.60{+/-}0.006), (-1.34{+/-}0.007, -3.22{+/-}0.008), and (-0.46{+/-}0.009, -0.87{+/-}0.012)mas/yr. The errors mentioned in the PMs are the Gaussian fitting errors. The blue straggler stars (BSS) in all three old clusters were found to exhibit centralized radial distribution. The clusters' radii are determined as 9.4', 12.95', and 6.6' for Be32, Be98, and King23 using radial density profiles. Ages of the clusters determined by isochrone fitting are 4.90{+/-}0.22, 3.23{+/-}0.15, and 1.95{+/-}0.22Gyr. The errors given in the clusters ages are the internal errors. The mass function slopes are found to be flatter than Salpeter's value for all three clusters. All three clusters are found to be dynamically relaxed. Galactic orbits are derived for these clusters, which demonstrate that the studied clusters follow a circular path around the Galactic center.
17185. VPHAS+ DR2 survey
ID:
ivo://CDS.VizieR/II/341
Title:
VPHAS+ DR2 survey
Short Name:
II/341
Date:
21 Oct 2021
Publisher:
CDS
Description:
The primary goal of the VST Photometric H{alpha} Survey of the Southern Galactic Plane and Bulge (VPHAS+) is to collect single-epoch ugri broad-band and Ha narrow-band photometry across the southern Galactic Plane within the latitude range -5{deg}<b<+5{deg} down to point source magnitudes of ~21 or better. The VPHAS+ footprint also includes the inner Galactic Bulge, defined as a 20x20 deg^2^ box around the Galactic Centre: this assures optical coverage of the full VVV footprint. For all massive OBA stars this survey is deep enough to explore all but the most heavily obscured locations of the southern Plane, reaching to >4kpc from the Sun. These data will increase the number of known southern emission line stars by up to an order of magnitude, yielding much better statistics on important short-lived types of object. The wide-area uniform photometry obtained will also facilitate stellar population studies, capable of tracing structure over much of the southern Plane. VPHAS+ will trawl the star-formation history of the Galaxy as seen in stellar remnants of all types.
17186. V photometry of bright stars of M33
ID:
ivo://CDS.VizieR/J/MNRAS/370/1429
Title:
V photometry of bright stars of M33
Short Name:
J/MNRAS/370/1429
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have conducted a long-term V-band photometric monitoring of M33 on 95 nights during four observing seasons (2000-2003). A total number of 6418 light curves of bright objects in the range of 14-21mag have been obtained. All measurements are publicly available. A total of 127 new variables were detected, of which 28 are periodic. 10 previously known non-periodic variables were identified as periodic, three of which are Cepheids, and another previously known periodic variable was identified as an eclipsing binary. Our derived periods range from 2.11 to almost 300d. For 50 variables we have combined our observations with those of the DIRECT project, obtaining light curves of up to 500 measurements, with a time-span of ~7yr. We have detected a few interesting variables, including a 99.3d periodic variable with a 0.04mag amplitude, at the position of supernova remnant (SNR) 19.
17187. V, R and I light curves of 4 new low-mass M-type EBs
ID:
ivo://CDS.VizieR/J/AJ/156/220
Title:
V, R and I light curves of 4 new low-mass M-type EBs
Short Name:
J/AJ/156/220
Date:
21 Oct 2021
Publisher:
CDS
Description:
We performed multicolor photometric and spectroscopic observations of four new low-mass M-type eclipsing binaries (HAT 225-03429, CRTS J085623.0+282620, CRTS J110302.4+201611, 2MASS J16344899+3716423) in 2017. We obtained new VRI light curves and minimum times of these four systems. Based on our minimum times, we updated the orbital periods and the linear ephemerides using the least squares method. We analyzed these four systems using the Wilson-Devinney program, and obtained the orbital and starspot parameters. The results of our analysis of the light curves indicate that HAT 225-03429 and CRTS J085623.0+282620 are detached eclipsing binaries, CRTS J110302.4+201611 is a semi-detached eclipsing binary, and 2MASS J16344899+3716423 is a contact binary. We performed LAMOST spectroscopic studies of chromospheric activity indicators (H{alpha}, H{beta}, H{gamma}, H{delta}, and Ca II H&K lines) for these four systems for the first time. We first determined their spectral types and calculated the equivalent widths of their chromospheric active indicators. These indicators show that the four low-mass M-type eclipsing binaries are active. Furthermore, the radii of these stars are notably larger than model predictions for their masses, except for the secondary component of HAT 225-03429 and the primary component of CRTS J110302.4+201611.
17188. VRB photometry of red supergiants
ID:
ivo://CDS.VizieR/J/ApJ/501/153
Title:
VRB photometry of red supergiants
Short Name:
J/ApJ/501/153
Date:
21 Oct 2021
Publisher:
CDS
Description:
Knowledge of the red supergiant (RSG) population of nearby galaxies allows us to probe massive star evolution as a function of metallicity; however, contamination by foreground Galactic dwarfs dominates surveys for red stars in Local Group galaxies beyond the Magellanic Clouds. Model atmospheres predict that low-gravity supergiants will have B-V values that are redder by several tenths of a magnitude than foreground dwarfs at a given V-R color, a result that is largely independent of reddening. We conduct a BVR survey of several fields in the Local Group galaxies NGC 6822, M33, and M31 as well as neighboring control fields and identify RSG candidates from CCD photometry. The survey is complete to V=20.5, corresponding to M_V_=-4.5 or an M_bol_ of -6.3 for the reddest stars. Follow-up spectroscopy at the Ca II triplet of 130 stars is used to demonstrate that our photometric criterion for identifying RSGs is highly successful (96% for stars brighter than V=19.5; 82% for V=19.5-20.5). Classification spectra are also obtained for a number of stars in order to calibrate color with spectral type empirically.
17189. VR CCD photometry of variable stars in the GC NGC 4147
ID:
ivo://CDS.VizieR/J/AJ/158/51
Title:
VR CCD photometry of variable stars in the GC NGC 4147
Short Name:
J/AJ/158/51
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results of a search for variable stars in a region of the globular cluster NGC 4147 based on photometric observations with a 4Kx4K CCD imager mounted at the axial port of the recently installed 3.6 m Devasthal optical telescope (DOT) at Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, India. We performed time series photometry of NGC 4147 in the V and R bands, and identified 42 periodic variables in the region of NGC 4147, 28 of which have been detected for the first time. Seventeen variable stars are located within the half-light radius ~<0.48', of which 10 stars are newly identified variables. Two of the 10 variables are located within the core radius ~<0.09'. Based on their location in the V/(V-R) color-magnitude diagram and variability characteristics, seven, eight, five, and one newly identified probable member variables are classified as RRc, EA/E, EW, and SX Phe, respectively. The metallicity of NGC 4147 estimated from the light curves of RRab and RRc stars with the help of Fourier decomposition is found to be characteristic of Oosterhoff II. The distance derived using the light curves of RRab stars is consistent with that obtained from the observed V/(V-R) color-magnitude diagram.
17190. VRc observations of LMC long-period red variables
ID:
ivo://CDS.VizieR/J/MNRAS/330/137
Title:
VRc observations of LMC long-period red variables
Short Name:
J/MNRAS/330/137
Date:
21 Oct 2021
Publisher:
CDS
Description:
146 long-period red variable stars in the Large Magellanic Cloud (LMC) from the three-year Microlensing Observations in Astrophysics (MOA) project data base were analysed. A careful periodic analysis was performed on these stars and a catalogue of their magnitudes, colours, periods and amplitudes is presented. We convert our blue and red magnitudes to K-band values using 19 oxygen-rich stars. A group of red short-period stars separated from the Mira sequence has been found on a (log P,K) diagram. They are located at the short period side of the Mira sequence consistent with the work of Wood & Sebo (1996MNRAS.282..958W). There are two interpretations for such stars; a difference in pulsation mode or a difference in chemical composition. We investigated the properties of these stars together with their colour, amplitude and periodicity. We conclude that they have small amplitudes and less regular variability. They are likely to be higher-mode pulsators. A large scatter has also been found on the long-period side of the (logP,K) diagram. This is possibly a systematic spread given that the blue band of our photometric system covers both standard B and V bands and affects carbon-rich stars.

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