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5941. Short-period variables in young open cluster Stock 8
ID:
ivo://CDS.VizieR/J/AJ/158/68
Title:
Short-period variables in young open cluster Stock 8
Short Name:
J/AJ/158/68
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present time-series photometry in the field of Stock 8 and identified 130 short-period variable stars. Twenty-eight main-sequence and 23 pre-main-sequence variables are found to be part of cluster Stock 8. The main-sequence variables are classified as slow pulsators of the B-type, {beta} Cep, and {delta} Scuti stars. Fourteen main-sequence stars could be new class variables as discussed by Mowlavi et al. (2013, J/A+A/554/A108) and Lata et al. (2011MNRAS.418.1346L; 2012MNRAS.427.1449L; 2014, J/MNRAS/442/273; 2016MNRAS.456.2505L). The age and mass of pre-main-sequence variables are found to be ~<5 Myr and in the mass range of 0.5-2.8 M_{sun}_, respectively. These pre-main-sequence stars could be T-Tauri variables. We have found 5 and 2 of 23 pre-main-sequence variables as classical T-Tauri stars and Herbig Ae/Be stars, respectively, whereas 16 pre-main-sequence stars are classified as weak-line T-Tauri stars.
5942. Short-period variables near Galactic Centre
ID:
ivo://CDS.VizieR/J/MNRAS/429/385
Title:
Short-period variables near Galactic Centre
Short Name:
J/MNRAS/429/385
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the result of our near-infrared survey of short-period variable stars (P<60d) in a field of view of 20'x30' towards the Galactic Centre (GC). Forty-five variables are discovered and we classify the variables based on their light-curve shapes and other evidence. In addition to 3 classical Cepheids reported previously, we find 16 type II Cepheids, 24 eclipsing binaries, 1 pulsating star with P=0.265d (RR Lyr or {delta} Sct) and 1 Cepheid-like variable whose nature is uncertain. Eclipsing binaries are separated into the foreground objects and those significantly obscured by interstellar extinction. One of the reddened binaries contains an O-type supergiant and its light curve indicates an eccentric orbit. We discuss the nature and distribution of type II Cepheids as well as the distance to the GC based on these Cepheids and other distance indicators. The estimates of R_0_(GC) we obtained based on photometric data agree with previous results obtained with kinematics of objects around the GC. Furthermore, our result gives support to the reddening law obtained by Nishiyama and collaborators, A_Ks_/E(H-Ks)=1.44, because a different reddening law would result in a rather different distance estimate.
5943. Short-period var. stars OmegaWhite survey
ID:
ivo://CDS.VizieR/J/MNRAS/454/507
Title:
Short-period var. stars OmegaWhite survey
Short Name:
J/MNRAS/454/507
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the goals, strategy and first results of the OmegaWhite survey: a wide-field high-cadence g-band synoptic survey which aims to unveil the Galactic population of short-period variable stars (with periods <80min), including ultracompact binary star systems and stellar pulsators. The ultimate goal of OmegaWhite is to cover 400deg^2^ along the Galactic plane reaching a depth of g=21.5mag (10{sigma}), using OmegaCam on the VLT Survey Telescope (VST). The fields are selected to overlap with surveys such as the Galactic Bulge Survey and the VST Photometric H{alpha} Survey of the Southern Galactic Plane for multiband colour information. Each field is observed using 38 exposures of 39s each, with a median cadence of ~2.7min for a total duration of two hours. Within an initial 26deg^2^, we have extracted the light curves of 1.6 million stars, and have identified 613 variable candidates which satisfy our selection criteria. Furthermore, we present the light curves and statistical properties of 20 sources which have the highest likelihood of being variable stars. One of these candidates exhibits the colours and light-curve properties typically associated with ultracompact AM CVn binaries, although its spectrum exhibits weak Balmer absorption lines and is thus not likely to be such a binary system. We also present follow-up spectroscopy of five other variable candidates, which identifies them as likely low-amplitude {delta} Sct pulsating stars.
5944. Short-term variability of comet C/2012S1
ID:
ivo://CDS.VizieR/J/A+A/575/A52
Title:
Short-term variability of comet C/2012S1
Short Name:
J/A+A/575/A52
Date:
21 Oct 2021
Publisher:
CDS
Description:
We observed comet C/2012 S1 (ISON) during six nights in February 2013 when it was at 4.8AU from the Sun. At this distance and time the comet was not very active and it was theoretically possible to detect photometric variations likely due to the rotation of the cometary nucleus. The goal of this work is to obtain differential photometry of the comet inner coma using different aperture radii in order to derive a possible rotational period.
5945. Short-term variability of 29 minor planets
ID:
ivo://CDS.VizieR/J/A+A/522/A93
Title:
Short-term variability of 29 minor planets
Short Name:
J/A+A/522/A93
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results of 6 years of observations, reduced and analyzed with the same tools in a systematic way. We present completely new data on 15 objects (1998SG35, 2002GB10, 2003EL61, 2003FY128, 2003MW12, 2003OP32, 2003WL7, 2004SB60, 2004UX10, 2005CB79, 2005RM43, 2005RN43, 2005RR43, 2005UJ438, 2007UL126 (or 2002KY14)), for 5 objects we present a new analysis of previously published results plus additional data (2000WR106, 2002CR46, 2002TX300, 2002VE95, 2005FY9) and for 9 objects we present a new analysis of data already published (1996TL66, 1999TZ1, 2001YH140, 2002AW197, 2002LM60, 2003AZ84, 2003CO1, 2003VS2, 2004DW). Lightcurves, possible rotation periods and photometric amplitudes are reported for all of them. The photometric variability is smaller than previously thought: the mean amplitude of our sample is 0.1mag and only around 15% of our sample has a larger variability than 0.15mag. The smaller variability than previously thought seems to be a bias of previous observations. We find a very weak trend of faster spinning objects towards smaller sizes, which appears to be consistent with the fact that the smaller objects are more collisionally evolved, but could also be a specific feature of the Centaurs, the smallest objects in our sample.We also find that the smaller the objects, the larger their amplitude, which is also consistent with the idea that small objects are more collisionally evolved and thus more deformed. Average rotation rates from our work are 7.5h for the whole sample, 7.6h for the TNOs alone and 7.3h for the Centaurs. All of them appear to be somewhat faster than what one can derive from a compilation of the scientific literature and our own results. Maxwellian fits to the rotation rate distribution give mean values of 7.5h (for the whole sample) and 7.3h (for the TNOs only). Assuming hydrostatic equilibrium we can determine densities from our sample under the additional assumption that the lightcurves are dominated by shape effects, which is likely no realistic. The resulting average density is 0.92g/cm^3^ which is not far from the density constraint that one can derive from the apparent spin barrier that we observe.
5946. Sh 2-205 Vilnius photometry
ID:
ivo://CDS.VizieR/J/BaltA/22/223
Title:
Sh 2-205 Vilnius photometry
Short Name:
J/BaltA/22/223
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of CCD photometry in the seven-color Vilnius system for 922 stars down to V~17mag in a 1.5 square degree field at the northern edge of the HII region Sh2-205, at the Perseus and Camelopardalis border. Using the intrinsic color indices and photometric reddening-free Q-parameters, two-dimensional spectral types for most stars are determined.
5947. sigma Gem BV photometry
ID:
ivo://CDS.VizieR/J/A+A/646/A6
Title:
sigma Gem BV photometry
Short Name:
J/A+A/646/A6
Date:
21 Oct 2021
Publisher:
CDS
Description:
We aim to study the spot evolution and differential rotation in the magnetically active cool K-type giant star sigma Gem from broadband photometry and continuous spectroscopic observations that span 150 nights. We use high-resolution, high signal-to-noise ratio spectra obtained with the Hertzsprung SONG telescope to reconstruct surface (photospheric) temperature maps with Doppler imaging techniques. The 303 observations span 150 nights and allow for a detailed analysis of the spot evolution and surface differential rotation. The Doppler imaging results are compared to simultaneous broadband photometry from the Tennessee State University T3 0.4m Automated Photometric Telescope. The activity from the stellar chromosphere, which is higher in the stellar atmosphere, is also studied using SONG observations of Balmer Halpha line profiles and correlated with the photospheric activity. The temperature maps obtained during eight consecutive stellar rotations show mainly high-latitude or polar spots, with the main spot concentrations above latitude 45{deg}. The spots concentrate around phase 0.25 near the beginning of our observations and around phase 0.75 towards the end. The photometric observations confirm a small jump in spot phases that occurred in February 2016. The cross-correlation of the temperature maps reveals rather strong solar-like differential rotation, giving a relative surface differential rotation coefficient of alpha=0.10+/-0.02. There is a weak correlation between the locations of starspots and enhanced emission in the chromosphere at some epochs.
5948. {sigma} Gem V-band differential light curve
ID:
ivo://CDS.VizieR/J/A+A/562/A107
Title:
{sigma} Gem V-band differential light curve
Short Name:
J/A+A/562/A107
Date:
21 Oct 2021
Publisher:
CDS
Description:
We model the photometry of RS CVn star sigma Geminorum to obtain new information on the changes of the surface starspot distribution, that is, activity cycles, differential rotation, and active longitudes. We used the previously published continuous period search (CPS) method to analyse V-band differential photometry obtained between the years 1987 and 2010 with the T3 0.4m Automated Telescope at the Fairborn Observatory. The CPS method divides data into short subsets and then models the light-curves with Fourier-models of variable orders and provides estimates of the mean magnitude, amplitude, period, and light-curve minima. These light-curve parameters are then analysed for signs of activity cycles, differential rotation and active longitudes.
5949. 3{sigma} hard sample of XMDS survey
ID:
ivo://CDS.VizieR/J/A+A/467/73
Title:
3{sigma} hard sample of XMDS survey
Short Name:
J/A+A/467/73
Date:
21 Oct 2021
Publisher:
CDS
Description:
Our goal is to probe the populations of obscured and unobscured AGN investigating their optical-IR and X-ray properties as a function of X-ray flux, luminosity and redshift within a hard X-ray selected sample with wide multiwavelength coverage. We selected a sample of 136 X-ray sources detected at a significance of >=3{sigma} in the 2-10keV band (F_2-10_>~10^-14^erg/cm^2^/s) in a ~1deg^2^ area in the XMM Medium Deep Survey (XMDS, Cat. <J/A+A/439/413>). The XMDS area is covered with optical photometry from the VVDS and CFHTLS surveys and infrared Spitzer data from the SWIRE survey. Based on the X-ray luminosity and X-ray to optical ratio, 132 sources are likely AGN, of which 122 have unambiguous optical - IR identification. The observed optical and IR spectral energy distributions of all identified sources are fitted with AGN/galaxy templates in order to classify them and compute photometric redshifts. X-ray spectral analysis is performed individually for sources with a sufficient number of counts and using a stacking technique for subsamples of sources at different flux levels. Hardness ratios are used to estimate X-ray absorption in individual weak sources.
5950. sigma Ori low-mass stars
ID:
ivo://CDS.VizieR/J/MNRAS/356/89
Title:
sigma Ori low-mass stars
Short Name:
J/MNRAS/356/89
Date:
21 Oct 2021
Publisher:
CDS
Description:
Intermediate-resolution (R~7000) spectroscopy is presented for 76 photometrically selected very low-mass (0.04<M<0.3M_{sun}_) candidate members of the young cluster around sigma Orionis (sigma Ori). More than two-thirds appear to be genuine cluster members on the basis that they exhibit Li I 6708{AA} absorption, weak Na I 8183/8195{AA} features and a radial velocity consistent with the cluster mean. Photometric selection alone therefore appears to be very effective in identifying cluster members in this mass range. Only six objects appear to be certain non-members; however, a substantial subset of 13 candidates have ambiguous or contradictory indications of membership and lack Li absorption. Together with an observed spread in the equivalent width of the Li absorption feature in the cooler stars of our sample, this indicates that there may be deficiencies in our understanding of the formation of this line in cool, low-gravity objects.