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3481. Light-curve models of black hole
ID:
ivo://CDS.VizieR/J/A+A/625/A152
Title:
Light-curve models of black hole
Short Name:
J/A+A/625/A152
Date:
21 Oct 2021
Publisher:
CDS
Description:
In the new era of gravitational wave (GW) and multi-messenger astrophysics, the detection of a GW signal from the coalescence of a black hole - neutron star (BHNS) binary remains a highly anticipated discovery. This kind of system is expected to be within reach of the second generation of ground-based detectors. In this context, we develop a series of versatile semi-analytical models to predict the properties of all the electromagnetic (EM) counterparts of BHNS mergers.We include the nuclear-decay-powered kilonova emission, its radio remnant, the prompt emission from the jet and the related afterglow. The properties of these counterparts depend upon those of the outflows that result from the partial disruption of the NS during the merger and from the accretion disc around the remnant, which are necessary ingredients for transient EM emission to accompany the GW signal. We therefore define ways to relate the properties of these outflows to those of the progenitor binary, establishing a link between the binary parameters and the counterpart properties. From the resulting model, we anticipate the variety of light curves that can emerge after a BHNS coalescence, from the radio up to gamma-rays. These light curves feature universal traits which are the imprint of the dynamics of the emitting outflows, but at the same time they show a clear dependence on the BH mass and spin, though with a high degree of degeneracy. The latter can be deduced by joint GW - EM analysis. In this paper, we perform a proof-of-concept multi-messenger parameter estimation of a BHNS merger with an associated kilonova, to test how the information from the EM counterpart can complement that from the GW signal. Our results indicate that the observation and modeling of the kilonova can help to break the degeneracies in the GW parameter space, leading to better constraints on, e.g., the BH spin.
3482. Light curve of (2060) Chiron
ID:
ivo://CDS.VizieR/J/A+A/576/A18
Title:
Light curve of (2060) Chiron
Short Name:
J/A+A/576/A18
Date:
21 Oct 2021
Publisher:
CDS
Description:
We propose that several short-duration events observed in past stellar occultations by Chiron were produced by ring material. Some similarities between these events and the characteristics of Chariklo's rings could indicate common mechanisms around centaurs. From a reanalysis of the stellar occultation data in the literature, we determined two possible orientations of the pole of Chiron's rings, with ecliptic coordinates {lambda}=(352+/-10){deg}, {beta}=(37+/-10){deg} or {lambda}=(144+/-10){deg}, {beta}=(24+/-10){deg}. The mean radius of the rings is (324+/-10)km. One can use the rotational lightcurve amplitude of Chiron at different epochs to distinguish between the two solutions for the pole. Both solutions imply a lower lightcurve amplitude in 2013 than in 1988, when the rotational lightcurve was first determined. We derived Chiron's rotational lightcurve in 2013 from observations at the 1.23m CAHA telescope, and indeed its amplitude was smaller than in 1988. We also present a rotational lightcurve in 2000 from images taken at the CASLEO 2.15m telescope that is consistent with our predictions. Out of the two poles, the {lambda}=(144+/-10){deg}, {beta}=(24+/-10){deg} solution provides a better match to a compilation of rotational lightcurve amplitudes from the literature and those presented here. We also show that using this preferred pole orientation, Chiron's long-term brightness variations are compatible with a simple model that incorporates the changing brightness of the rings while the tilt angle with respect to the Earth is changing with time. Also, the variability of the water ice band in Chiron's spectra as seen in the literature can be explained to a large degree by an icy ring system whose tilt angle changes with time and whose composition includes water ice, analogously to the case of Chariklo. We present several possible formation scenarios for the rings from qualitative points of view and speculate on why rings might be common in centaurs. We also speculate on whether the known bimodal color distribution of the centaurs could be due to centaurs with rings and centaurs without rings.
3483. Light curve of CR Boo over 1990-2012
ID:
ivo://CDS.VizieR/J/PASP/125/126
Title:
Light curve of CR Boo over 1990-2012
Short Name:
J/PASP/125/126
Date:
21 Oct 2021
Publisher:
CDS
Description:
Two telescopes are used at the Morgan-Monroe Observatory of Indiana University for autonomous long-term photometric monitoring of stellar sources, mostly cataclysmic variable stars. The instrumentation is designed and implemented to be appropriate for multiyear automated monitoring. The capabilities and limitations of the equipment are described, along with accounts of the software, the reduction procedures, the motivations for the scientific programs, and the execution of the observing campaigns. Data on the AM CVn-type cataclysmic variable CR Boo are presented and discussed as an example of the kinds of light curves generated at this facility. The He-rich disk in CR Boo has SU UMa-type outburst behavior, with both superoutbursts and what appear to be dwarf nova outbursts. However, the light curve is quite irregular and displays a wide variety of unusual features such as switching among several superoutburst recurrence intervals, and having intervals of dwarf nova-like outbursts that seem to come and go. We discuss the likelihood that deterministic chaos is responsible for these irregularities.
3484. Light curve of EROS2 J005135-714459
ID:
ivo://CDS.VizieR/J/A+A/486/891
Title:
Light curve of EROS2 J005135-714459
Short Name:
J/A+A/486/891
Date:
21 Oct 2021
Publisher:
CDS
Description:
For seven years, the EROS-2 project obtained a mass of photometric data on variable stars. We present a peculiar Cepheid-like star, in the direction of the Small Magellanic Cloud, which demonstrates unusual photometric behaviour over a short time interval.
3485. Light curve of HD 172189
ID:
ivo://CDS.VizieR/J/A+A/468/637
Title:
Light curve of HD 172189
Short Name:
J/A+A/468/637
Date:
21 Oct 2021
Publisher:
CDS
Description:
The eclipsing delta-Scuti star HD 172189 is a probable member of the open cluster IC 4756 and a promising candidate target for the CoRoT mission. The detection of pulsation modes is the first step in the asteroseismological study of the star. Further, the calculation of the orbital parameters of the binary system allows us to make a dynamical determination of the mass of the star, which works as an important constraint to test and calibrate the asteroseismological models. We performed a detailed frequency analysis of 210 hours of photometric data of HD 172189 obtained from the STEPHI XIII campaign. We have identified six pulsation frequencies with a 99% confidence level and a seventh with a 65% confidence level, in the range between 100-300uHz. In addition, three eclipses were observed during the campaign, allowing us to improve the determination of the orbital period of the system.
3486. Light curve of HR Lyr over 1991-2012
ID:
ivo://CDS.VizieR/J/AJ/147/105
Title:
Light curve of HR Lyr over 1991-2012
Short Name:
J/AJ/147/105
Date:
21 Oct 2021
Publisher:
CDS
Description:
The 22 yr light curve of HR Lyr, acquired with a typical cadence of 2-6 days, is examined for periodic and quasi-periodic variations. No persistent periodicities are revealed. Rather, the light curve variations often take the form of nearly linear rises and falls having typical e-folding times of about 100 days. Occasional ~0.6mag outbursts are also seen, with properties similar to those of small outbursts found in some nova-like cataclysmic variables. When the photometry is formed into yearly averages, a decline of 0.012+/-0.005mag/yr is apparent, consistent with the fading of irradiation-induced Mdot following the nova. The equivalent width of H{alpha} is tabulated at three epochs over the interval 1986-2008 in order to compare with a recent result for DK Lac in which H{alpha} was found to be fading 50 yr after the nova. However, our results for such a fading in HR Lyr are inconclusive.
3487. Light curve of K2-292 (HD 119130)
ID:
ivo://CDS.VizieR/J/A+A/623/A114
Title:
Light curve of K2-292 (HD 119130)
Short Name:
J/A+A/623/A114
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery and characterisation of a new transiting planet from Campaign 17 of the Kepler extended mission K2. The planet K2-292 b is a warm sub-Neptune on a 17-d orbit around a bright (V=9.9mag) solar-like G3 V star with a mass and radius of Ms=1.00+/-0.03M_{sun}_ and Rs=1.09+/-0.03R_{sun}_ respectively. We model simultaneously the K2 photometry and CARMENES spectroscopic data and derive a radius of Rp=2.63_-0.10+^+0.12^R_{earth}_ and mass of Mp=24.5_-4.4_^+4.4^M_{earth}_, yielding a mean density of 7.4_-1.5_^+1.6^g/cm^3^, which makes it one of the densest sub-Neptune planets known to date. We also detect a linear trend in radial velocities of HD 119130 that suggests a long-period companion with a minimum mass on the order of 33M_{earth}_. If confirmed, it would support a formation scenario of K2-292 b by migration caused by Kozai-Lidov oscillations.
3488. Light curve of 2MASS J05352184-0546085
ID:
ivo://CDS.VizieR/J/ApJ/664/1154
Title:
Light curve of 2MASS J05352184-0546085
Short Name:
J/ApJ/664/1154
Date:
21 Oct 2021
Publisher:
CDS
Description:
The newly discovered brown dwarf eclipsing binary 2MASS J05352184-0546085 provides a unique laboratory for testing the predictions of theoretical models of brown dwarf formation and evolution. The finding that the lower mass brown dwarf in this system is hotter than its higher mass companion represents a challenge to brown dwarf evolutionary models, none of which predict this behavior. Here we present updated determinations of the basic physical properties of 2M0535-05, bolstering the surprising reversal of temperatures with mass in this system. We compare these measurements with widely used brown dwarf evolutionary tracks, and find that the temperature reversal can be explained by some models if the components of 2M0535-05 are mildly non-coeval, possibly consistent with dynamical simulations of brown dwarf formation. Alternatively, a strong magnetic field on the higher mass brown dwarf might explain its anomalously low surface temperature, consistent with emerging evidence that convection is suppressed in magnetically active, low-mass stars. Finally, we discuss future observational and theoretical work needed to further characterize and understand this benchmark system.
3489. Light curve of OGLE-2018-BLG-0677
ID:
ivo://CDS.VizieR/J/AJ/159/256
Title:
Light curve of OGLE-2018-BLG-0677
Short Name:
J/AJ/159/256
Date:
08 Dec 2021
Publisher:
CDS
Description:
We report the analysis of the microlensing event OGLE-2018-BLG-0677. A small feature in the light curve of the event leads to the discovery that the lens is a star-planet system. Although there are two degenerate solutions that could not be distinguished for this event, both lead to a similar planet-host mass ratio. We perform a Bayesian analysis based on a Galactic model to obtain the properties of the system and find that the planet corresponds to a super- Earth/sub-Neptune with a mass of M_planet_=3.96_-2.66_^+5.88^M_{Earth}_. The host star has a mass of M_host_=0.12_-0.08_^+0.14^M_{odot}_. The projected separation for the inner and outer solutions are 0.63_-0.17_^+0.20^au and 0.72_-0.19_^+0.23^au respectively. At {Delta}{chi}^2^={chi}^2^(1L1S-{chi}^2^(2L1S)=46, this is by far the lowest {Delta}{chi}^2^ for any securely detected microlensing planet to date, a feature that is closely connected to the fact that it is detected primarily via a "dip" rather than a "bump."
3490. Light curve of R Cygni
ID:
ivo://CDS.VizieR/J/A+A/390/585
Title:
Light curve of R Cygni
Short Name:
J/A+A/390/585
Date:
21 Oct 2021
Publisher:
CDS
Description:
A detailed analysis of the century long visual light curve of the long-period Mira star R Cygni is presented and discussed. The data were collected from the publicly available databases of the AFOEV, the BAAVSS and the VSOLJ. The full light curve consists of 26655 individual points obtained between 1901 and 2001. The light curve and its periodicity were analysed with help of the O-C diagram, Fourier analysis and time-frequency analysis. The results demonstrate the limitations of these linear methods. The next step was to investigate the possible presence of low-dimensional chaos in the light curve. For this, a smoothed and noise-filtered signal was created from the averaged data and with the help of time delay embedding, we have tried to reconstruct the attractor of the system. The main result is that R Cygni shows such period-doubling events that can be interpreted as being caused by a repetitive bifurcation of the chaotic attractor between a period 2T orbit and chaos. The switch between these two states occurs in a certain compact region of the phase space, where the light curve is characterized by ~1500-day long transients. The Lyapunov spectrum was computed for various embedding parameters confirming the chaotic attractor, although the exponents suffer from quite high uncertainty because of the applied approximation. Finally, the light curve is compared with a simple one zone model generated by a third-order differential equation which exhibits well-expressed period-doubling bifurcation. The strong resemblance is another argument for chaotic behaviour. Further studies should address the problem of global flow reconstruction, including the determination of the accurate Lyapunov exponents and dimension.