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491. Magnetic CVs spectra & other variable objects II.
ID:
ivo://CDS.VizieR/J/AJ/159/114
Title:
Magnetic CVs spectra & other variable objects II.
Short Name:
J/AJ/159/114
Date:
21 Oct 2021
Publisher:
CDS
Description:
This is the second paper of a series presenting our search for magnetic cataclysmic variables (mCVs) among candidates selected mostly from the Catalina Real-Time Transient Survey. We present the identification spectra, obtained at the SOAR Telescope, as well as magnitudes and Gaia distances for 45 objects. Of these, 39 objects are identified as CVs, from which 8 targets show observational characteristics of mCVs, being 7 polars and 1 intermediate polar. The remaining 31 CVs in our sample are probably non-magnetic systems, in low (22 systems) or high (9 systems) accretion states. Six targets of the sample are not CVs (5 active galactic nuclei and 1 T-Tauri star). Among the 8 objects with mCV spectra, 6 are new classifications. Three polars were observed in low-accretion state, either revealing photospheric features of the secondary star and allowing the estimation of their spectral type, or presenting H{beta} Zeeman components associated to the white dwarf (WD) magnetic field. In addition to the results obtained in the first paper of the series, and depending on the confirmation of these classifications by observational follow-up, our results would increase the sample of known polars by about 9%.
492. Margoni-Stagni variables
ID:
ivo://CDS.VizieR/J/other/IBVS/4431
Title:
Margoni-Stagni variables
Short Name:
J/other/IBVS/443
Date:
21 Oct 2021
Publisher:
CDS
Description:
In a 1984 publication, "A search for new variable stars in the Milky Way field at l=780{deg}, b=-60{deg}", R. Margoni and R. Stagni give finding charts, light curves, and elements for 99 new variable stars. A follow-up paper (Margoni et al., 1989A&AS...81..393M) contains additional observations for the same stars. About three-quarters of these are now named variables. I have gone through this list to determine precise positions for all the stars, and have made identifications with the IRAS and GSC catalogues.
493. MASCARA bright variable stars light curves
ID:
ivo://CDS.VizieR/J/A+A/617/A32
Title:
MASCARA bright variable stars light curves
Short Name:
J/A+A/617/A32
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Multi-site All-Sky CAmeRA (MASCARA) aims to find the brightest transiting planet systems by monitoring the full sky at magnitudes 4<V<8.4, taking data every 6.4 seconds. The northern station has been operational on La Palma since February 2015. These data can also be used for other scientific purposes, such as the study of variable stars. In this paper we aim to assess the value of MASCARA data for studying variable stars by determining to what extent known variable stars can be recovered and characterised, and how well new, unknown variables can be discovered. We used the first 14 months of MASCARA data, consisting of the light curves of 53401 stars with up to one million flux points per object. All stars were cross-matched with the VSX catalogue to identify known variables. The MASCARA light curves were searched for periodic flux variability using generalised Lomb-Scargle periodograms. If significant variability of a known variable was detected, the found period and amplitude were compared with those listed in the VSX database. If no previous record of variability was found, the data were phase folded to attempt a classification. Of the 1919 known variable stars in the MASCARA sample with periods 0.1<P<10-days, amplitudes >2%, and that have more than 80 hours of data, 93.5% are recovered. In addition, the periods of 210 stars without a previous VSX record were determined, and 282 candidate variable stars were newly identified. We also investigated whether second order variability effects could be identified. The O'Connell effect is seen in seven eclipsing binaries, of which two have no previous record of this effect. MASCARA data are very well suited to study known variable stars. They also serve as a powerful means to find new variables among the brightest stars in the sky. Follow-up is required to ensure that the observed variability does not originate from faint background objects.
494. 2MASS interferometric calibrator candidates
ID:
ivo://CDS.VizieR/J/ApJS/203/33
Title:
2MASS interferometric calibrator candidates
Short Name:
J/ApJS/203/33
Date:
21 Oct 2021
Publisher:
CDS
Description:
We aim to provide a list of sources found to be unresolved from direct observations with high angular resolution and dynamic range, which can be used to choose interferometric calibrators. To this purpose, we have used a large number of lunar occultations recorded with the ISAAC instrument at the Very Large Telescope to select sources found to be unresolved and without close companions. An algorithm has been used to determine the limiting angular resolution achieved for each source, taking into account a noise model built from occulted and unocculted portions of the light curves. We have obtained upper limits on the angular sizes of 556 sources, with magnitudes ranging from Ks~4 to 10, with a median of 7.2mag. The upper limits on possible undetected companions (within ~0.5") range from Ks~8 to 13, with a median of 11.5mag. One-third of the sources have angular sizes <=1mas, and two-thirds have sizes <=2mas. This list of unresolved sources matches well the capabilities of current large interferometric facilities. We also provide available cross-identifications, magnitudes, spectral types, and other auxiliary information. A fraction of the sources are found to be potentially variable. The list covers parts of the Galactic Bulge and in particular the vicinity of the Galactic Center, where extinction is very significant and traditional lists of calibrators are often insufficient.
495. Massive binaries in the LMC
ID:
ivo://CDS.VizieR/J/ApJ/748/96
Title:
Massive binaries in the LMC
Short Name:
J/ApJ/748/96
Date:
21 Oct 2021
Publisher:
CDS
Description:
The stellar mass-luminosity relation is poorly constrained by observations for high-mass stars. We describe our program to find eclipsing massive binaries in the Magellanic Clouds using photometry of regions rich in massive stars, and our spectroscopic follow-up to obtain radial velocities and orbits. Our photometric campaign identified 48 early-type periodic variables, of which only 15 (31%) were found as part of the microlensing surveys. Spectroscopy is now complete for 17 of these systems, and in this paper we present analysis of the first two, LMC 172231 and ST2-28, simple detached systems of late-type O dwarfs of relatively modest masses. Our orbit analysis yields very precise masses (~2%), and we use tomography to separate the components and determine effective temperatures by model fitting, necessary for determining accurate (0.05-0.07 dex) bolometric luminosities in combination with the light-curve analysis. Our approach allows more precise comparisons with evolutionary theory than previously possible. To our considerable surprise, we find a small, but significant, systematic discrepancy: all of the stars are slightly undermassive, by typically 11% (or overluminous by 0.2 dex) compared with that predicted by the evolutionary models. We examine our approach for systematic problems, but find no satisfactory explanation. The discrepancy is in the same sense as the long-discussed and elusive discrepancy between the masses measured from stellar atmosphere analysis with the stellar evolutionary models, and might suggest that either increased rotation or convective overshooting is needed in the models.
496. 2MASS large-amplitude variable stars
ID:
ivo://CDS.VizieR/J/AJ/138/1508
Title:
2MASS large-amplitude variable stars
Short Name:
J/AJ/138/1508
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of variable stars in the near-infrared wavelength detected with overlapping regions of the Two Micron All Sky Survey public images, and discuss their properties. The investigated region is in the direction of the Galactic center (-30{deg}<~l<~20, |b|<~20), which covers the entire bulge. We have detected 136 variable stars, of which six are already known and 118 are distributed in the |b|<5{deg} region. Additionally, 84 variable stars have optical counterparts in Digitized Sky Survey images. The three diagrams (color-magnitude, light variance, and color-color diagrams) indicate that most of the detected variable stars should be large-amplitude and long-period variables such as Mira variables or OH/IR stars. The number density distribution of the detected variable stars implies that they trace the bar structure of the Galactic bulge.
497. Mass loss from Miras with and without Tc
ID:
ivo://CDS.VizieR/J/A+A/622/A120
Title:
Mass loss from Miras with and without Tc
Short Name:
J/A+A/622/A120
Date:
21 Oct 2021
Publisher:
CDS
Description:
We follow-up on a previous finding that AGB Mira variables containing the third dredge-up indicator technetium (Tc) in their atmosphere form a different sequence of K-[22] colour as a function of pulsation period than Miras without Tc. A near- to mid-infrared colour such as K-[22] is a good probe for the dust mass-loss rate of the stars. Contrary to what might be expected, Tc-poor Miras show redder K-[22] colours (i.e. higher dust mass-loss rates) than Tc-rich Miras at a given period. Here, the previous sample is extended and the analysis is expanded towards other colours and dust spectra. The most important aim is to investigate if the same two sequences can be revealed in the gas mass-loss rate. We analysed new optical spectra and expanded the sample by including more stars from the literature. Near- and mid-IR photometry and ISO dust spectra of our stars were investigated where available. Literature data of gas mass-loss rates of Miras and semi-regular variables were collected and analysed. Our results show that Tc-poor Miras are redder than Tc-rich Miras in a broad range of the mid-IR, suggesting that the previous finding based on the K-[22] colour is not due to a specific dust feature in the 22-micron band. We establish a linear relation between K-[22] and the gas mass-loss rate. We also find that the 13 micron feature disappears above K-[22]~2.17mag, corresponding to dM/dt}_g_~2.6x10^-7^M_{sun}/yr. No similar sequences of Tc-poor and Tc-rich Miras in the gas mass-loss rate vs. period diagram are found, most probably owing to limitations in the available data. Different hypotheses to explain the observation of two sequences in the P vs. K-[22] diagram are discussed and tested, but so far, none of them convincingly explains the observations. Nevertheless, we might have found an hitherto unknown but potentially important process influencing mass loss on the TP-AGB.
498. 2MASS photometry of cataclysmic variables
ID:
ivo://CDS.VizieR/J/other/NewA/13.133
Title:
2MASS photometry of cataclysmic variables
Short Name:
J/other/NewA/13.
Date:
21 Oct 2021
Publisher:
CDS
Description:
Spatial distribution, galactic model parameters and luminosity function of cataclysmic variables (CVs) in the solar neighbourhood have been found using distances estimated from the period-luminosity-colours (PLCs) relation of CVs. It can be concluded that exponential function fits better to the observational z-distributions of the whole CVs in the sample, non-magnetic CVs and dwarf novae, while the sech^2^ function is more appropriate for nova-like stars and polars. The vertical scaleheight of CVs is 158+/-14pc for the 2MASS J band limiting apparent magnitude of 15.8. The discrepancies between the theoretical and observational population studies of CVs can be at least partly removed if the sech^2^ density function is used in deriving the galactic model parameters. We estimated the vertical scaleheights of 128+/-20pc and 160+/-5pc for dwarf novae and nova-like stars, respectively. The local space density of CVs is found ~3x10^-5^pc^-3^ which is in agreement with the lower limit of the theoretical predictions. The luminosity function of CVs shows a trend toward higher space density at low luminosity, implying an increase in the number of short-period systems.
499. Maxima of short period pulsating stars
ID:
ivo://CDS.VizieR/J/other/JAVSO/39.23
Title:
Maxima of short period pulsating stars
Short Name:
J/other/JAVSO/39
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper contains times of maxima for 56 short period pulsating stars (primarily RR Lyrae and delta Scuti stars). This represents a portion of the CCD observations received by the AAVSO Short Period Pulsator (SPP) section in 2010 along with some earlier data.
500. M31B eclipsing binaries and Cepheids
ID:
ivo://CDS.VizieR/J/AJ/115/1016
Title:
M31B eclipsing binaries and Cepheids
Short Name:
J/AJ/115/1016
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have undertaken a long-term project, DIRECT, to obtain the direct distances to two important galaxies in the cosmological distance ladder - M31 and M33 - using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult to detect, DEBs provide us with the potential to determine these distances with an accuracy better than 5%. The extensive photometry obtained in order to detect DEBs provides us with good light curves for the Cepheid variables. These are essential to the parallel project to derive direct Baade-Wesselink distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries, the distance estimates will be free of any intermediate steps. As a first step in the DIRECT project, between 1996 September and 1997 January we obtained 36 full nights on the Michigan-Dartmouth-MIT Observatory 1.3m telescope and 45 full/partial nights on the F.L. Whipple Observatory 1.2m telescope to search for DEBs and new Cepheids in the M31 and M33 galaxies. In this paper, first in a series, we present the catalog of variable stars, most of them newly detected, found in the field M31B [({alpha},{delta})=(11.20{deg}, 41.59{deg}), J2000.0]. We have found 85 variable stars: 12 eclipsing binaries, 38 Cepheids, and 35 other periodic, possible long-period or nonperiodic variables. The catalog of variables, as well as their photometry and finding charts, is available via anonymous ftp and the World Wide Web: http://cfa-www.harvard.edu/~kstanek/DIRECT.