70 research outputs found
Investigation of Cyclic O−C Changes in a Sample of Eclipsing Binaries
In this work we present an analysis of cyclic or pseudo-cyclic O–C behavior in a sample of 29 eclipsing binaries, selected to exhibit large-amplitude changes in O–C. We attempt to explain the period variations by: 1) the light time travel effect due to an unseen third body orbiting a system; 2) a sudden jump in the linear ephemeris caused by either variations in the mass transfer rate or CME ejections. A search for tertiary components was carried out with adaptive optics imaging for six systems exhibiting the highest amplitude in their O–C diagrams
The Absolute Parameters of The Detached Eclipsing Binary V482 Per
We present the results of the spectroscopic, photometric and orbital period
variation analyses of the detached eclipsing binary \astrobj{V482~Per}. We
derived the absolute parameters of the system (M = 1.51 M,
M = 1.29 M, R = 2.39 R, R = 1.45
R, L = 10.15 L, L = 3.01 L) for the
first time in literature, based on an analysis of our own photometric and
spectroscopic observations. We confirm the nature of the variations observed in
the system's orbital period, suggested to be periodic by earlier works. A light
time effect due to a physically bound, star-sized companion (M = 2.14
M) on a highly eccentric (e = 0.83) orbit, seems to be the most
likely cause. We argue that the companion can not be a single star but another
binary instead. We calculated the evolutionary states of the system's
components, and we found that the primary is slightly evolving after the Main
Sequence, while the less massive secondary lies well inside it.Comment: Published in New Astronomy, Vol. 41, p. 42-4
Is there a circumbinary planet around NSVS 14256825?
The cyclic behaviour of (O-C) residuals of eclipse timings in the sdB+M
eclipsing binary NSVS 14256825 was previously attributed to one or two
Jovian-type circumbinary planets. We report 83 new eclipse timings that not
only fill in the gaps in those already published but also extend the time span
of the (O-C) diagram by three years. Based on the archival and our new data
spanning over more than 17 years we re-examined the up to date system (O-C).
The data revealed systematic, quasi-sinusoidal variation deviating from an
older linear ephemeris by about 100 s. It also exhibits a maximum in the (O-C)
near JD 2,456,400 that was previously unknown. We consider two most credible
explanations of the (O-C) variability: the light propagation time due to the
presence of an invisible companion in a distant circumbinary orbit, and
magnetic cycles reshaping one of the binary components, known as the Applegate
or Lanza-Rodono effect. We found that the latter mechanism is unlikely due to
the insufficient energy budget of the M-dwarf secondary. In the framework of
the third-body hypothesis, we obtained meaningful constraints on the Keplerian
parameters of a putative companion and its mass. Our best-fitting model
indicates that the observed quasi-periodic (O-C) variability can be explained
by the presence of a brown dwarf with the minimal mass of 15 Jupiter masses
rather than a planet, orbiting the binary in a moderately elliptical orbit (~
0.175) with the period of ~ 10 years. Our analysis rules out two planets model
proposed earlier.Comment: 17 pages, 9 figures, 4 tables, accepted to A
Far-infrared photometry of OJ 287 with the Herschel Space Observatory
Context: The blazar OJ 287 has shown a approximate to 12 year quasi-periodicity over more than a century, in addition to the common properties of violent variability in all frequency ranges. It is the strongest known candidate to have a binary singularity in its central engine.Aims: We aim to better understand the different emission components by searching for correlated variability in the flux over four decades of frequency measurements.Methods: We combined data at frequencies from the millimetric to the visible to characterise the multifrequency light curve in April and May 2010. This includes the only photometric observations of OJ 287 made with the Herschel Space Observatory: five epochs of data obtained over 33 days at 250, 350, and 500 mu m with Herschel-SPIRE.Results: Although we find that the variability at 37 GHz on timescales of a few weeks correlates with the visible to near-IR spectral energy distribution, there is a small degree of reddening in the continuum at lower flux levels that is revealed by the decreasing rate of decline in the light curve at lower frequencies. However, we see no clear evidence that a rapid flare detected in the light curve during our monitoring in the visible to near-IR light curve is seen either in the Herschel data or at 37 GHz, suggesting a low-frequency cut-off in the spectrum of such flares.Conclusions: We see only marginal evidence of variability in the observations with Herschel over a month, although this may be principally due to the poor sampling. The spectral energy distribution between 37 GHz and the visible can be characterised by two components of approximately constant spectral index: a visible to far-IR component of spectral index alpha = -0.95, and a far-IR to millimetric spectral index of alpha = -0.43. There is no evidence of an excess of emission that would be consistent with the 60 mu m dust bump found in many active galactic nuclei.</p
Catching profound optical flares in blazars
Flaring episodes in blazars represent one of the most violent processes
observed in extra-galactic objects. Studies of such events shed light on the
energetics of the physical processes occurring in the innermost regions of
blazars, which cannot otherwise be resolved by any current instruments. In this
work, we present some of the largest and most rapid flares captured in the
optical band in the blazars 3C 279, OJ 49, S4 0954+658, TXS 1156+295 and PG
1553+113. The source flux was observed to increase by nearly ten times within a
timescale of a few weeks. We applied several methods of time series analysis
and symmetry analysis. Moreover, we also performed searches for periodicity in
the light curves of 3C 279, OJ 49 and PG 1553+113 using the Lomb-Scargle method
and found plausible indications of quasi-periodic oscillations (QPOs). In
particular, the 33- and 22-day periods found in 3C 279, i.e. a 3:2 ratio, are
intriguing. These violent events might originate from magnetohydrodynamical
instabilities near the base of the jets, triggered by processes modulated by
the magnetic field of the accretion disc. We present a qualitative treatment as
the possible explanation for the observed large amplitude flux changes in both
the source-intrinsic and source-extrinsic scenarios.Comment: 11 pages, 6 figures, MNRAS accepte
Profound optical flares from the relativistic jets of active galactic nuclei
Intense outbursts in blazars are among the most extreme phenomena seen in
extragalactic objects. Studying these events can offer important information
about the energetic physical processes taking place within the innermost
regions of blazars, which are beyond the resolution of current instruments.
This work presents some of the largest and most rapid flares detected in the
optical band from the sources 3C 279, OJ 49, S4 0954+658, Ton 599, and PG
1553+113, which are mostly TeV blazars. The source flux increased by nearly ten
times within a few weeks, indicating the violent nature of these events. Such
energetic events might originate from magnetohydrodynamical instabilities near
the base of the jets, triggered by processes modulated by the magnetic field of
the accretion disc. We explain the emergence of flares owing to the injection
of high-energy particles by the shock wave passing along the relativistic jets.
Alternatively, the flares may have also arisen due to geometrical effects
related to the jets. We discuss both source-intrinsic and source-extrinsic
scenarios as possible explanations for the observed large amplitude flux
changes.Comment: 8 pages, 2 figures, 38th International Cosmic Ray Conference
(ICRC2023) proceeding
Promise of Persistent Multi-Messenger Astronomy with the Blazar OJ 287
Successful observations of the seven predicted bremsstrahlung flares from the unique bright blazar OJ 287 firmly point to the presence of a nanohertz gravitational wave (GW) emitting supermassive black hole (SMBH) binary central engine. We present arguments for the continued monitoring of the source in several electromagnetic windows to firmly establish various details of the SMBH binary central engine description for OJ 287. In this article, we explore what more can be known about this system, particularly with regard to accretion and outflows from its two accretion disks. We mainly concentrate on the expected impact of the secondary black hole on the disk of the primary on 3 December 2021 and the resulting electromagnetic signals in the following years. We also predict the times of exceptional fades, and outline their usefulness in the study of the host galaxy. A spectral survey has been carried out, and spectral lines from the secondary were searched for but were not found. The jet of the secondary has been studied and proposals to discover it in future VLBI observations are mentioned. In conclusion, the binary black hole model explains a large number of observations of different kinds in OJ 287. Carefully timed future observations will be able to provide further details of its central engine. Such multi-wavelength and multidisciplinary efforts will be required to pursue multi-messenger nanohertz GW astronomy with OJ 287 in the coming decades
Refining the prediction for OJ 287 next impact flare arrival epoch
The bright blazar OJ~287 routinely parades high brightness bremsstrahlung
flares which are explained as being a result of a secondary supermassive black
hole (SMBH) impacting the accretion disk of a primary SMBH in a binary system.
We begin by showing that these flares occur at times predicted by a simple
analytical formula, based on the Kepler equation, which explains flares since
1888. The next impact flare, namely the flare number 26, is rather peculiar as
it breaks the typical pattern of two impact flares per 12 year cycle. This will
be the third bremsstrahlung flare of the current cycle that follows the already
observed 2015 and 2019 impact flares from OJ~287. Unfortunately, astrophysical
considerations make it difficult to predict the exact arrival epoch of the
flare number 26. In the second part of the paper, we describe our recent OJ~287
observations. They show that the pre-flare light curve of flare number 22,
observed in 2005, exhibits similar activity as the pre-flare light curve in
2022, preceding the expected flare number 26 in our model. We argue that the
pre-flare activity most likely arises in the primary jet whose activity is
modulated by the transit of the secondary SMBH through the accretion disk of
the primary. Observing the next impact flare of OJ~287 in October 2022 will
substantiate the theory of disk impacts in binary black hole systems.Comment: 16 pages, 2 figure
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