We investigate the long-term optical variability of the Be/X-ray binary GRO J2058+42 and the possible connection with periods of enhanced X-ray activity. We performed an optical spectroscopic and photometric analysis on data collected during about 18 years. We also present the first optical polarimetric observations of this source. The long-term optical light curves in the $BVRI$ bands and the evolution of the H$α$ equivalent width display a sinusoidal pattern with maxima and minima that repeat every $\sim$9.5 years. The amplitude of this variability increases as the wavelength increases. The H$α$ equivalent width varied from about $-0.3$ to $-15$ Å. We found a significant decrease in the polarization degree during the low optical state. The optical maxima occur near periods of enhanced X-ray activity and are followed by a drop in the optical emission. Unlike many other Be/X-ray binaries, GRO 2058+42 does not display $V/R$ variability. The long-term optical variability agrees with the standard model of a Be/X-ray binary, where the circumstellar disk of the Be star grows and dissipates on timescales of 9--10 years. We find that the dissipation of the disk started after a major X-ray outburst. However, the stability of the H$α$ line shape as a double-peak profile and the lack of asymmetries suggest the absence of a warped disk and argue against the presence of a highly distorted disk during major X-ray outbursts.
H-alpha Emission Variability in the gamma-ray Binary LS I +61 303
LS I +61 303是一个非常罕见的高质量X射线双星（HMXB）的例子，也表现出MeV-TeV的发射，使其成为少数几个“伽马射线双星”之一。在这里，我们提出的H-α光谱显示出强烈的变化，在26.5天的轨道周期和十年的时间尺度。我们检测到的螺旋密度波的证据，在被拱星盘的部分轨道。H-α谱线轮廓也显示出一个戏剧性的发射爆发前不久apastron，观察作为一个红移的肩膀线轮廓，作为紧凑的源移动几乎直接远离观察者。我们调查了这个红肩的几个可能的起源，包括一个吸积盘，质量转移流，和一个紧凑的脉冲星风星云，通过Be星的风和相对论脉冲星风之间的冲击形成。
We studied the variability of the linear polarization and brightness of the $γ$-ray binary LS I +61 303. High-precision BVR photopolarimetric observations were carried out with the Dipol-2 polarimeter on the 2.2 m remotely controlled UH88 telescope at Mauna Kea Observatory and the 60 cm Tohoku telescope at Haleakala Observatory (Hawaii) over 140 nights in 2016--2019. We determined the position angle of the intrinsic polarization $θ\simeq 11^\circ$, which can either be associated with the projection of the Be star's decretion disk axis on the plane of sky, or can differ from it by $90^\circ$. U…
EXO 1745-248 is a transient neutron-star low-mass X-ray binary that resides in the globular cluster Terzan 5. We studied the transient during its quiescent state using 18 Chandra observations of the cluster acquired between 2003 and 2016. We found an extremely variable source, with a luminosity variation in the 0.5-10 keV energy range of $\sim3$ orders of magnitude (between $3\times10^{31}$ erg s$^{-1}$ and $2\times10^{34}$ erg s$^{-1}$) on timescales from years down to only a few days. Using an absorbed power-law model to fit its quiescent spectra, we obtained a typical photon index of $\sim1…
Variability of VHE $γ$-ray emission from the binary PSR B1259-63/LS 2883
本文研究了从双星系统PSR B 1259 -63/LS 2883的方向观测到的$γ$射线强度在其三次近星点通过期间的变化。一个简单而直接的方法是适用于公布的数据与成像大气切伦科夫技术。不管检测过程中的许多问题，该方法仅适用于在指定区域中记录的非常高能量的光子的数量。在该方案的范围内，我们认识到变化归因于高水平的显着性的内在源活动的变化。
The high-mass X-ray binary LS I +61°303 exhibits variability in its radio and X-ray emissions, ranging from minute to hour time-scales. At such short time-scales, not much is known about the possible correlations between these two emissions from this source, which might offer hints to their origin. Here, we study the relationship between these emissions using simultaneous X-ray and radio monitoring. We present new radio observations using the Arcminute Microkelvin Imager Large Array telescope at two frequency bands, 13-15.5 and 15.5-18 GHz. We also describe new X-ray observations performed usi…
Variability in the orbital profiles of the X-ray emission of the gamma-ray binary LS I +61 303
利用Rossi X射线定时探测器（RXTE）正比计数器阵列（PCA）对$γ$双星LS I +61 303进行了35个完整的轨道运动周期的观测分析。这构成了迄今为止针对该来源分析的最大连续X射线监测数据集。这种扩展分析使我们能够报告：a）发现X射线发射的轨道轮廓的可变性，b）在源的典型总体行为之上存在几个（最近的）短耀斑，给定PCA视场，其可能与或可能不与LS I +61 303相关联，和c）仅使用软X射线数据确定轨道周期。
In the last 10 years multi-wavelength fast variability studies of low mass X-ray binaries have shown a dramatic development. A key discovery was the detection of O-IR sub-second fluctuations in two black-hole transients, lagging the X-rays by $\approx$0.1 s. This demonstrated how the fluctuations observed in the inflow could be transferred to the jet, allowing therefore also to study in a completely new way the physical processes which take place at the base of the jet. In this paper we review the latest developments of the study of jets with this new approach, focusing on the results obtained…
The cataclysmic variable MV Lyr was present in the Kepler field yielding a light curve with the duration of almost 1500 days with 60 second cadence. Such high quality data of this nova-like system with obvious fast optical variability show multicomponent power density spectra. Our goal is to study the light curve from different point of view, and perform a shot profile analysis. We search for characteristics not discovered with standard power density spectrum based methods. The shot profile method identifies individual shots in the light curve, and averages them in order to get all substructur…
Quasi-simultaneous Optical Flux and Polarization Variability of the Binary Super Massive Black Hole Blazar OJ 287 from 2015 to 2023: Detection of an Anticorrelation in Flux and Polarization Variability
Much of the parameter space relevant to the evolution of astrophysical circumbinary accretion discs remains unexplored. We have carried out a suite of circumbinary disc simulations surveying both disc thickness and kinematic viscosity, using both constant-$ν$ and constant-$α$ prescriptions. We focus primarily on disc aspect ratios between $0.1$ and $0.033$, and on viscosities between $ν=0.0005$ and $ν=0.008$ (in units of binary semi-major axis and orbital frequency), and specialise to circular equal-mass binaries. Both factors strongly influence the evolution of the binary semi-major axis: at …
We present the results of long-term monitoring of the X-ray emission from the ultraluminous X-ray source XMMUJ122939.9+075333 in the extragalactic globular cluster RZ2109. The combination of the high X-ray luminosity, short term X-ray variability, X-ray spectrum, and optical emission suggest that this system is likely an accreting black hole in a globular cluster. To study the long-term behavior of the X-ray emission from this source, we analyze both new and archival Chandra and XMM-Newton observations, covering 16 years from 2000 to 2016. For all of these observations, we fit extracted spectr…
The photometric light curve of PG1302-102 shows periodic variability which makes this object one of the most plausible supermassive black hole binary candidate. Interestingly, the most recent study of its updated optical light curve reports a decrease in significance of periodicity which may suggest that the binary model is less favorable. Here, we model the PG 1302-102 light curve, spanning almost 20 years, with a supermassive black hole binary system in which a perturbation in the accretion disk of more massive component is present. Our model reproduces well the observed light curve with a s…
Context. Colliding wind binaries are massive systems featuring strong, interacting stellar winds which may act as particle accelerators. Therefore, such binaries are good candidates for detection at high energies. However, only the massive binary Eta Carinae has been firmly associated with a gamma-ray signal. A second system, gamma^2 Velorum, is positionally coincident with a gamma-ray source, but unambiguous identification remains lacking. Aims. Observing orbital modulation of the flux would establish an unambiguous identification of the binary gamma^2 Velorum as the gamma-ray source detected…
We analyzed multiwavelength observations of the previously identified Galactic center X-ray binary CXO 174528.79-290942.8 (XID 6592) and determine that the near-infrared counterpart is a red supergiant based on its spectrum and luminosity. Scutum X-1 is the only previously known X-ray binary with a red supergiant donor star and closely resembles XID 6592 in terms of X-ray luminosity (L$_{\mathrm{X}}$), absolute magnitude, and IR variability (L$_{\mathrm{IR,var}}$), supporting the conclusion that XID 6592 contains a red supergiant donor star. The XID 6592 infrared counterpart shows variability …
Here we confirm the short periodic variability of a subparsec supermassive binary black hole (SMBBH) candidate Mrk 231 in the extended optical photometric data set collected by the Catalina Real-Time Transient Survey (CRTS) and All-Sky Automated Survey for Supernovae (ASAS-SN). Using the Lomb-Scargle periodogram and 2DHybrid method, we detected the significant periodicity of ~ 1.1 yr beyond a damped random walk model in the CRTS+ASAS-SN optical data set. Mrk 231 has been previously proposed as a SMBBH candidate with a highly unequal mass ratio (q~ 0.03), very tight mutual separation of ~590 AU…
AX J0049.4-7323 is a Be/X-ray binary in the Small Magellanic Cloud hosting a ~750 s pulsar which has been observed over the last ~17 years by several X-ray telescopes. Despite numerous observations, little is known about its X-ray behaviour. Therefore, we coherently analysed archival Swift, Chandra, XMM-Newton, RXTE, and INTEGRAL data, and we compared them with already published ASCA data, to study its X-ray long-term spectral and flux variability. AX J0049.4-7323 shows a high X-ray variability, spanning more than three orders of magnitudes, from L ~ 1.6E37 erg/s (0.3-8 keV, d=62 kpc) down to …
Based on our dedicated Swift monitoring program, MOMO, OJ 287 is one of the best-monitored blazars in the X-ray--UV--optical regime. Here, we report results from our accompanying, dense, multi-frequency (1.4--44 GHz) radio monitoring of OJ 287 between 2015 and 2022 covering a broad range of activity states. Fermi gamma-ray observations are added. We characterize the radio flux and spectral variability in detail, including DCF and other variability analyses, and discuss its connection with the multiwavelength emission. Deep fades of radio and optical--UV fluxes are found to occur every 1--2 yea…
The bright quasar PG1302-102 has been identified as a candidate supermassive black hole binary from its near-sinusoidal optical variability. While the significance of its optical periodicity has been debated due to the stochastic variability of quasars, its multi-wavelength variability in the ultraviolet (UV) and optical bands is consistent with relativistic Doppler boost caused by the orbital motion in a binary. However, this conclusion was based previously on sparse UV data which were not taken simultaneously with the optical data. Here we report simultaneous follow-up observations of PG1302…
Because of its complex clumpy wind, prominent cyclotron resonant scattering features, intrinsic variability and convenient physical parameters (close distance, high inclination, small orbital separation) which facilitate the observation and analysis of the system, Vela X-1 is one of the key systems to understand accretion processes in high-mass X-ray binaries on all scales. We revisit Vela X-1 with two new observations taken with NuSTAR at orbital phases ~0.68-0.78 and ~0.36-0.52 which show a plethora of variability and allow us to study the accretion geometry and stellar wind properties of th…
Context. Gamma-ray binaries are systems composed of a massive star and a compact object whose interaction leads to particle acceleration up to relativistic energies. In the last fifteen years, a few binaries have been discovered to emit at high energies, but their number is still scarce. The TeV source HESS J1832-093 has been proposed as a binary candidate, although its nature is unclear. Neither a GeV counterpart nor a period was found for it. Aims. The purpose of this work is to search for a gamma-ray source at GeV energies to understand the origin of the TeV signal. For an unambiguous ident…
Redback millisecond pulsars (MSPs) typically show pronounced orbital variability in their X-ray emission due to our changing view of the intrabinary shock (IBS) between the pulsar wind and stellar wind from the companion. Some redbacks ("transitional" MSPs) have shown dramatic changes in their multiwavelength properties, indicating a transition from a radio pulsar state to an accretion-powered state. The redback MSP 47 Tuc W showed clear X-ray orbital variability in the Chandra ACIS-S observations in 2002, which were not detectable in the longer Chandra HRC-S observations in 2005-06, suggestin…
The Multi-wavelength Characteristics of the TeV Binary LS I +61$^\circ$ 303
本文研究了TeV双星LS I +61 $^\circ$ 303的射电、软X射线、硬X射线和γ射线（GeV和TeV）能量特性。长期的变化特性作为一个功能的阶段的二元周期的26.496天，以及阶段的超轨道周期的1626天，分为一个矩阵的观测到10个$\times$ 10阶段的这两个时期。结果表明，长周期光变可以用超轨道周期的正弦函数来描述，相位和振幅随双星周期相位系统地变化。我们还发现了一个明确的波长依赖的变化，在这种变化的描述。为了理解辐射机制，我们定义了三个状态的轨道/超轨道相位矩阵和检查的宽带光谱能量分布。导出的源参数表明，排放几何形状占主导地位的喷流结构显示出系统的变化与轨道/超轨道周期。我们认为LS I +61 $^\circ$ 303可能是一个具有稳定喷流的微类星体。
Exotic optical variability in the black hole X-ray binary IGR J17091-3624
Yale University（耶鲁大学）；New York University Abu Dhabi（纽约大学阿布扎比分校）；Instituto de Astrofísica de Canarias（加那利天体物理研究所）；Universidad de La Laguna（拉古纳大学）；Kapteyn Astronomical Institute, University of Groningen（格罗宁根大学卡普坦天文研究所）；University of Southampton（南安普顿大学）；Instituto Argentino de Radioastronomía (CCT La Plata, CONICET（阿根廷射电天文学研究所）；CICPBA（意大利国家天体物理研究所布雷拉天文台）；UNLP)；INAF, Osservatorio Astronomico di Brera
The event GW170817/GRB 170817A, discovered via the successful joint observation of its gravitational wave radiation and its multi-wavelength electromagnetic counterparts, was the first definite "smoking-gun" from the merger of two neutron stars (NSs). However, the remnant of the merger remains unknown. Piro et al. recently claimed that a low-significance X-ray variability in GRB 170817A. By systematically comparing the properties of variability in the afterglow of GRB 170817A and X-ray flares in GRB afterglows, we find that this X-ray variability seems to share similar statistical correlations…
