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21951. Times of minima for 18 SMC eclipsing binaries
ID:
ivo://CDS.VizieR/J/A+A/572/A71
Title:
Times of minima for 18 SMC eclipsing binaries
Short Name:
J/A+A/572/A71
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Danish 1.54-meter telescope at the La Silla observatory was used for photometric monitoring of selected eccentric eclipsing binaries located in the Small Magellanic Cloud. The new times of minima were derived for these systems, which are needed for accurate determination of the apsidal motion. Moreover, many new times of minima were derived from the photometric databases OGLE and MACHO. Eighteen early-type eccentric-orbit eclipsing binaries were studied. Their O-C diagrams of minima timings were analysed and the parameters of the apsidal motion were obtained. The light curves of these eighteen binaries were analysed using the program PHOEBE, giving the light curve parameters. For several systems, the additional third light also was detected.
21952. Times of minima for 1SWASP J234401.81-212229.1
ID:
ivo://CDS.VizieR/J/A+A/558/A71
Title:
Times of minima for 1SWASP J234401.81-212229.1
Short Name:
J/A+A/558/A71
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report our investigation of 1SWASP J234401.81-212229.1, a variable with a 18461.6s period. After identification in a 2011 search of the SuperWASP archive for main-sequence eclipsing binary candidates near the distribution's short-period limit of ~0.20d, it was measured to be undergoing rapid period decrease in our earlier work, though later observations supported a cyclic variation in period length. Spectroscopic data obtained in 2012 with the Southern African Large Telescope did not, however, support the interpretation of the object as a normal eclipsing binary. Here, we consider three possible explanations consistent with the data: a single-star oblique rotator model in which variability results from stable cool spots on opposite magnetic poles; a two-star model in which the secondary is a brown dwarf; and a three-star model involving a low-mass eclipsing binary in a hierarchical triple system. We conclude that the latter is the most likely model.
21953. Times of minima of eclipsing binaries in 2003
ID:
ivo://CDS.VizieR/J/other/IBVS/5502
Title:
Times of minima of eclipsing binaries in 2003
Short Name:
J/other/IBVS/550
Date:
21 Oct 2021
Publisher:
CDS
Description:
Times of minima for a number of neglected eclipsing binaries are presented.
21954. Times of minimum light for EQ Tau
ID:
ivo://CDS.VizieR/J/AJ/147/98
Title:
Times of minimum light for EQ Tau
Short Name:
J/AJ/147/98
Date:
21 Oct 2021
Publisher:
CDS
Description:
New photometric data of EQ Tau observed in 2010 and 2013 are presented. Light curves obtained in 2000 and 2004 by Yuan & Qian and 2001 by Yang & Liu, together with our two newly determined sets of light curves, were analyzed using the Wilson-Devinney code. The five sets of light curves exhibit very obvious variations, implying that the light curves of EQ Tau show a strong O'Connell effect. We found that EQ Tau is an A-type shallow contact binary with a contact degree of f=11.8%; variable dark spots on the primary component of EQ Tau were also observed. Using 10 new times of minimum light, together with those collected from the literature, the orbital period change of EQ Tau was analyzed. We found that its orbital period includes a secular decrease (dP/dt=-3.63x10^-8^days/yr) and a cyclic oscillation (A_3_=0.0058 days and P_3_=22.7 yr). The secular increase of the period can be explained by mass transfer from the more massive component to the less massive one or/and angular momentum loss due to a magnetic stellar wind. The Applegate mechanism cannot explain the cyclic orbital period change. A probable transit-like event was observed in 2010. Therefore, the cyclic orbital period change of EQ Tau may be due to the light time effect of a third body.
21955. Times of minimum light for IR Cas
ID:
ivo://CDS.VizieR/J/AJ/148/96
Title:
Times of minimum light for IR Cas
Short Name:
J/AJ/148/96
Date:
21 Oct 2021
Publisher:
CDS
Description:
The first photometric analysis of IR Cas was carried out based on the new observed BVRI light curves. The symmetric light curves and nearly flat secondary minimum indicate that very precise photometric results can be determined. We found that IR Cas is a near contact binary with the primary component filling its Roche lobe. An analysis of the O-C diagram based on all available times of minimum light reveals evidence for a periodic change with a semi-amplitude of 0.0153days and a period of 39.7yr superimposed on a secular decrease at a rate of dp/dt=-1.28(+/-0.09)x10^-7^days/yr. The most reasonable explanation for the periodic change is the light time-travel effect due to a third body. The period decrease may be caused by mass transfer from the primary component to the secondary. With the decreasing period, IR Cas would eventually evolve into a contact system.
21956. Times of minimum light for TY UMa
ID:
ivo://CDS.VizieR/J/AJ/149/120
Title:
Times of minimum light for TY UMa
Short Name:
J/AJ/149/120
Date:
21 Oct 2021
Publisher:
CDS
Description:
TY UMa is an F-type eclipsing binary star. Four-color light curves and radial velocities of this system were presented and simultaneously analyzed using the W-D code. It is found that TY UMa is a W-subtype shallow contact binary system (f=13.4%) with a mass ratio of q=2.523. In order to explain the asymmetric light curve of this binary, a dark spot on the less massive component was employed. Our newly determined 31 times of minimum light, including those collected from the literature, have been used to analyze orbital period changes of TY UMa. The complicated period variation could be sorted into a secular period increase at a rate of d_p_/d_t_=+5.18(+/-0.21)x10^-7^days/yr, a 51.7yr periodic modulation (A_3_=0.0182days), and a very small amplitude cyclic oscillation with a period of 10.0yr (A_4_=0.0015days). The long-term increase of the period can be explained by mass transfer from the less massive component to the more massive one. The Applegate mechanism may impossibly explain the two cyclic components in the period. The two cyclic variations are very likely caused by the light travel time effect of third and fourth components, suggesting that TY UMa is a quadruple system.
21957. Times of transits and occultations of WASP-12b
ID:
ivo://CDS.VizieR/J/AJ/154/4
Title:
Times of transits and occultations of WASP-12b
Short Name:
J/AJ/154/4
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new transit and occultation times for the hot Jupiter WASP-12b. The data are compatible with a constant period derivative: P.=-29+/-3ms/yr and P/P.=3.2Myr. However, it is difficult to tell whether we have observed orbital decay or a portion of a 14-year apsidal precession cycle. If interpreted as decay, the star's tidal quality parameter Q_star_ is about 2*10^5^. If interpreted as precession, the planet's Love number is 0.44+/-0.10. Orbital decay appears to be the more parsimonious model: it is favored by {Delta}_{chi}^2^_=5.5 despite having two fewer free parameters than the precession model. The decay model implies that WASP-12 was discovered within the final ~0.2% of its existence, which is an unlikely coincidence but harmonizes with independent evidence that the planet is nearing disruption. Precession does not invoke any temporal coincidence, but it does require some mechanism to maintain an eccentricity of {approx}0.002 in the face of rapid tidal circularization. To distinguish unequivocally between decay and precession will probably require a few more years of monitoring. Particularly helpful will be occultation timing in 2019 and thereafter.
21958. Times of X-ray minima & orbit numbers of Cyg X-3
ID:
ivo://CDS.VizieR/J/ApJ/871/244
Title:
Times of X-ray minima & orbit numbers of Cyg X-3
Short Name:
J/ApJ/871/244
Date:
21 Oct 2021
Publisher:
CDS
Description:
By using available archival X-ray data, we significantly extended the list of times of X-ray minima. The new list includes 65 data points obtained by critically reanalyzing RXTE ASM data, 88 data points based on observations by MAXI, and 2 data points based on observations by SUZAKU and AstroSat. Analyzing the data along with times of X-ray minima available from the literature, we provide the most accurate estimate of the rate of period change to date. We do not confirm the existence of a second derivative of the orbital period suggested by some authors earlier. Instead, we find that the changes in the period can be fit by a sum of quadratic and sinusoidal functions. The period of sinusoidal variations is 15.79yr. They can be related either to apsidal motion in the close binary with eccentricity e~0.03 or to the presence of a third body with a mass of about 0.7M_{sun}_ located at a distance ~16 au from the close binary.
21959. Time stability of the ICRF2 axes
ID:
ivo://CDS.VizieR/J/A+A/553/A122
Title:
Time stability of the ICRF2 axes
Short Name:
J/A+A/553/A122
Date:
21 Oct 2021
Publisher:
CDS
Description:
I assess the astrometric stability of the 295 defining sources of the current best realization of the International Celestial Reference System (ICRS): the second realization of the International Celestial Reference Frame (ICRF2), constructed and published in 2009 after the analysis of millions of VLBI observations at 2 and 8 GHz between 1979.6 and 2009.2. I also assess the time evolution of the ICRF2 axis stability. I derived coordinate time series of hundreds of quasars monitored by the regular geodetic VLBI program of the International VLBI Service for Geodesy and Astrometry (IVS). The axis stability was studied by constructing annual reference frames based on the ICRF2 defining sources. The time variable frame stability was obtained by computing the deformation parameters that lead from one frame to the next. I show that, although the astrometric stability of some of the ICRF2 defining sources has slightly degraded since 2009.2, the ensemble still constitutes a very stable reference frame. The current estimation of the axis stability over 1979.6-2013.1 remains at the same level as the one estimated over 1979.6-2009.2, i.e., on the order of 20uas for each axis.
21960. Timing data for the classical Cepheid l Car
ID:
ivo://CDS.VizieR/J/ApJ/824/1
Title:
Timing data for the classical Cepheid l Car
Short Name:
J/ApJ/824/1
Date:
21 Oct 2021
Publisher:
CDS
Description:
The classical Cepheid l Carinae is an essential calibrator of the Cepheid Leavitt Law as a rare long-period Galactic Cepheid. Understanding the properties of this star will also constrain the physics and evolution of massive (M>=8M_{sun}_) Cepheids. The challenge, however, is precisely measuring the star's pulsation period and its rate of period change. The former is important for calibrating the Leavitt Law and the latter for stellar evolution modeling. In this work, we combine previous time-series observations spanning more than a century with new observations to remeasure the pulsation period and compute the rate of period change. We compare our new rate of period change with stellar evolution models to measure the properties of l Car, but find models and observations are, at best, marginally consistent. The results imply that l Car does not have significantly enhanced mass-loss rates like that measured for {delta} Cephei. We find that the mass of l Car is about 8-10M_{sun}_. We present Hubble Space Telescope Cosmic Origins Spectrograph observations that also differ from measurements for {delta} Cep and {beta} Dor. These measurements further add to the challenge of understanding the physics of Cepheids, but do hint at the possible relation between enhanced mass-loss and ultraviolet emission, perhaps both due to the strength of shocks propagating in the atmospheres of Cepheids.

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