本文利用 AstroSat 观测和 JeTCAF 模型分析黑洞暂现源 Swift J1658.2–4242 的光谱与时变，估计其质量吸积率、日冕尺寸和黑洞质量，并揭示观测特性主要由吸积率和吸收柱密度变化引起。
摘要：
我们给出了对黑洞 X 射线暂现源 Swift J1658.2–4242 的 X 射线光谱和时变分析，该源由 AstroSat 观测。利用 JeTCAF 模型分析了三个时段的数据，以估计质量吸积率并理解流的几何结构。在这些观测中，最佳拟合盘质量吸积率（$\dot m_d$）在 $0.90^{+0.02}_{-0.01}$ 到 $1.09^{+0.04}_{-0.03}$ $\dot M_{\rm Edd}$ 之间变化，而晕质量吸积率从 $0.15^{+0.01}_{-0.01}$ 变化到 $0.25^{+0.02}_{-0.01}$ $\dot M_{\rm Edd}$。我们估计了动态日冕的尺寸，它从 $64.9^{+3.9}_{-3.1}$ 显著变化到 $34.5^{+2.0}_{-1.5}$ $r_g$，并且一个中等偏高的喷流/外流准直因子表明存在各向同性外流。推断出的高盘质量吸积率和较大的日冕尺寸表明该源可能处于黑洞 X 射线双星的中等至软光谱态。由不同模型组合估计的黑洞质量约为 $14 M_\odot$。此外，我们从模型拟合参数计算了准周期振荡（QPO）频率，这些频率与观测到的 QPO 相符。我们进一步从光变曲线的衰减轮廓和光谱参数计算了该系统的双星参数。在假设伴星为中期或晚期 K 型星的情况下，估计该系统的轨道周期为 $4.0\pm0.4$ 小时。我们使用 JeTCAF 模型的分析揭示了该源光谱-时变行为的物理起源，观测到的性质主要归因于质量吸积率和吸收柱密度的变化。
英文摘要：
We present the X-ray spectral and temporal analysis of the black hole X-ray transient Swift J1658.2--4242 observed by {\it AstroSat}. Three epochs of data have been analysed using the JeTCAF model to estimate the mass accretion rates and to understand the geometry of the flow. The best-fit disc mass accretion rate ($\dot m_d$) varies between $0.90^{+0.02}_{-0.01}$ to $1.09^{+0.04}_{-0.03}$ $\dot M_{\rm Edd}$ in these observations, while the halo mass accretion rate changes from $0.15^{+0.01}_{-0.01}$ to $0.25^{+0.02}_{-0.01}$ $\dot M_{\rm Edd}$. We estimate the size of the dynamic corona, that varies substantially from $64.9^{+3.9}_{-3.1}$ to $34.5^{+2.0}_{-1.5}$ $r_g$ and a moderately high jet/outflow collimation factor stipulates isotropic outflow. The inferred high disc mass accretion rate and bigger corona size indicate that the source might be in the intermediate to soft spectral state of black hole X-ray binaries. The mass of the black hole estimated from different model combinations is $\sim 14 M_\odot$. In addition, we compute the quasi-periodic oscillation (QPO) frequencies from the model-fitted parameters, which match the observed QPOs. We further calculate the binary parameters of the system from the decay profile of the light curve and the spectral parameters. The estimated orbital period of the system is $4.0\pm0.4$ hr by assuming the companion as a mid or late K-type star. Our analysis using the JeTCAF model sheds light on the physical origin of the spectro-temporal behaviour of the source, and the observed properties are mainly due to the change in both the mass accretion rates and absorbing column density.
We present a comprehensive multi-frequency study of the HBL 1ES 1959+650 using data from various facilities during the period 2016-2017, including X-ray data from {\it AstroSat} and {\it Swift} during the historically high X-ray flux state of the source observed until February 2021. The unprecedented quality of X-ray data from high cadence monitoring with the {\it AstroSat} during 2016-2017 enables us to establish a detailed description of X-ray flares in 1ES 1959+650. The synchrotron peak shifts significantly between different flux states, in a manner consistent with a geometric (changing Dop…
OJ 287 is a well-studied binary black hole system, that occasionally exhibits bright X-ray and optical flares. Here we present a detailed spectral study of its second brightest X-ray flare observed during 2019-2020 using archival Swift and NuSTAR observations along with ToO observations from AstroSat. The entire flaring period is divided into three states, defined as low, intermediate, and high states. The variation of hardness ratio (HR) with 0.3-10.0 keV integrated flux suggests a \enquote{softer-when-brighter} behavior, as also previously reported based on flux-index variations. Simultaneou…
We present the observational results from a detailed timing analysis of the black hole candidate Swift J1658.2-4242 during its 2018 outburst with the observations of Hard X-ray Modulation Telescope (Insight-HXMT), Neutron Star Interior Composition Explorer (NICER) and AstroSat in 0.1-250keV. The evolution of intensity, hardness and integrated fractional root mean square (rms) observed by Insight-HXMT and NICER are presented in this paper. Type-C quasi-periodic oscillations (QPOs) observed by NICER (0.8-3.5Hz) and Insight-HXMT (1-1.6Hz) are also reported in this work. The features of the QPOs a…
We present a 140ks observation of NGC 4593 with XMM-Newton providing simultaneous and continuous PN X-ray and OM UV (UVW1 2910Å) lightcurves which sample short-timescale variations better than previous observations. These observations were simultaneous with 22d of Swift X-ray and UV/optical monitoring, reported previously, and 4d of AstroSat X-ray (SXT), far (FUV 1541Å), and near (NUV 2632Å) UV allowing lag measurements between them and the highly-sampled XMM. From the XMM we find that UVW1 lags behind the X-rays by 29.5$\pm$1.3ks, $\sim$half the lag previously determined from the Swift monito…
SwiftJ0243.6+6124, the first Galactic ultra-luminous X-ray pulsar, was observed during its 2017-2018 outburst with \emph{AstroSat} at both sub- and super-Eddington levels of accretionwith X-ray luminosities of $L_{X}{\sim}7{\times}10^{37}$ and $6{\times}10^{38}$$ergs^{-1}$, respectively.Our broadband timing and spectral observations show that X-ray pulsations at ${\sim}9.85\rm{s}$ have been detected up to 150keV when the source was accreting at the super-Eddington level.The pulse profiles are a strong function of both energy and source luminosity,showing a double-peaked profile with pulse frac…
We present the X-ray timing and spectral analysis of the new Galactic X-ray transient Swift J1658.2-4242 observed with LAXPC and SXT instruments onboard {\it Astrosat}. We detect prominent C-type quasi-periodic oscillations (QPOs) of frequencies varying from $\sim 1.5$ Hz to $\sim 6.6$ Hz along with distinct 2nd harmonics and sub-harmonics. The QPO detected at $\sim 1.56$ Hz drifts to a higher centroid frequency of $\sim 1.74$ in the course of the observation, while the QPO detected at $\sim 6.6$\,Hz disappeared during hard flarings. The fractional rms at the QPO and the sub-harmonic frequenci…
AstroSat is a multi-wavelength satellite launched on 2015 September 28. The CZT Imager of AstroSat on its very first day of operation detected a long duration gamma-ray burst (GRB) namely GRB 151006A. Using the off-axis imaging and spectral response of the instrument, we demonstrate that CZT Imager can localise this GRB correct to about a few degrees and it can provide, in conjunction with Swift, spectral parameters similar to that obtained from Fermi/GBM. Hence CZT Imager would be a useful addition to the currently operating GRB instruments (Swift and Fermi). Specifically, we argue that the C…
We present the results of Target of Opportunity (ToO) observations made with AstroSat of the newly discovered black hole binary MAXI J1535-571. We detect prominent C-type Quasi-periodic Oscillations (QPOs) of frequencies varying from 1.85 Hz to 2.88 Hz, along with distinct harmonics in all the AstroSat observations. We note that while the fundamental QPO is seen in the 3 - 50 keV energy band, the harmonic is not significant above ~ 35 keV. The AstroSat observations were made in the hard intermediate state, as seen from state transitions observed by MAXI and Swift. We attempt spectral modelling…
I have used a sample of long Gamma Ray Bursts (GRBs) common to both \emph{Swift} and \emph{Fermi} to re-derive the parameters of the Yonetoku correlation. This allowed me to self-consistently estimate pseudo redshifts of all the bursts with unknown redshifts. This is the first time such a large sample of GRBs from these two instruments are used, both individually and in conjunction, to model the long GRB luminosity function. The GRB formation rate is modelled as the product of the cosmic star formation rate and a GRB formation efficiency for a given stellar mass. An exponential cut-off powerla…
We present the X-ray spectral and timing analysis of the transient black hole X-ray binary 4U 1630-47, observed with the AstroSat, Chandra and MAXI space missions during its soft X-ray outburst in 2016. The outburst, from the rising phase until the peak, is neither detected in hard X-rays (15-50 keV) by the Swift/BAT nor in radio. Such non-detection along with the source behavior in the hardness-intensity and color-color diagrams obtained using MAXI data confirm that both Chandra and AstroSat observations were performed during the high soft spectral state. The High Energy Grating (HEG) spectru…
Galactic transient black hole candidate (BHC) MAXI J1535-571 was discovered on 2017 September 02 simultaneously by {\it MAXI}/GSC and {\it Swift}/BAT instruments. It has also been observed by India's first multi-wavelength astronomy-mission satellite {\it AstroSat}, during the rising phase of its 2017-18 outburst. We make both the spectral and the temporal analysis of the source during 2017 September 12-17 using data of {\it AstroSat}'s Large Area X-ray Proportional Counter (LAXPC) in the energy range of $3-40$~keV to infer the accretion flow properties of the source. Spectral analysis is done…
We study accretion disk-corona connection in Seyfert 1 galaxies using simultaneous UV/X-ray observations of NGC 4593 (July 14-18, 2016) and NGC 7469 (October 15-19, 2017) performed with AstroSat. We use the X-ray (0.5-7.0 keV) data acquired with the Soft X-ray Telescope (SXT) and the UV (FUV: 130-180 nm, NUV: 200-300 nm) data obtained with the Ultra-Violet Imaging Telescope (UVIT). We also use the contemporaneous Swift observations of NGC 4593 and demonstrate AstroSat's capability for X-ray/UV correlation studies. We performed UV/X-ray cross-correlation analysis using the Interpolated and the …
We report the analysis of simultaneous multi-wavelength data of the high energy peaked blazar RGB J0710+591 from the LAXPC, SXT and UVIT instruments on-board AstroSat. The wide band X-ray spectrum (0.35 -- 30 keV) is modelled as synchrotron emission from a non-thermal distribution of high energy electrons. The spectrum is unusually curved, with a curvature parameter $β_p \sim 6.4$ for a log parabola particle distribution, or a high energy spectral index $p_2 > 4.5$ for a broken power-law distribution. The spectrum shows more curvature than an earlier quasi-simultaneous analysis of Swift-XRT/Nu…
We study the spectral and temporal properties of MAXI J0637-430 during its 2019-2020 outburst using \textit{NICER}, \textit{AstroSat} and \textit{Swift-XRT} data. The source was in a disc dominant state within a day of its detection and traces out a `c' shaped profile in the HID, similar to the `mini'-outbursts of the recurrent BHB 4U 1630-472. Energy spectrum is obtained in the $0.5-10$ keV band with \textit{NICER} and \textit{Swift-XRT}, and $0.5-25$ keV with \textit{AstroSat}. The spectra can be modelled using a multicolour disc emission (\textit{diskbb}) convolved with a thermal Comptonisa…
IGR J17091--3624 is a transient galactic black hole which has a distinct quasi-periodic variability known as `heartbeat', similar to the one observed in GRS 1915+105. In this paper, we report the results of $\sim 125$ ks \textit{AstroSat} observations of this source during the 2016 outburst. For the first time a double peaked QPO (DPQ) is detected in a few time segments of this source with a difference of $δf ~\sim12$ mHz between the two peaks. The nature of the DPQ was studied based on hardness ratios and using the static as well as the dynamic power spectrum. Additionally, a low frequency (2…
Evolution of the Inner Accretion Flow in Swift J1727.8$-$1613 across Intermediate States: Insights from Broadband Spectral and Timing Analysis
Inter-University Centre for Astronomy and Astrophysics（天文与天体物理大学间中心）；Institute of Astronomy, National Tsing Hua University（国立清华大学天文研究所）；Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文学中心）；Department of Pure and Applied Physics, Guru Ghasidas Vishwavidyalaya (A Central University)（古鲁·加西达斯维什瓦维迪亚亚拉（一所中央大学）纯与应用物理系）
We present a comprehensive spectral and temporal study of the black hole X-ray transient MAXI J1820+070 during its outbursts in 2018 using Swift/XRT, NICER, NuSTAR and AstroSat observations. The Swift/XRT and NICER spectral study shows a plateau in the light curve with spectral softening (hardness changes from $\sim$ $2.5$ to $2$) followed by a gradual decline without spectral softening during the first outburst. Also, spectral modelling suggests that the first outburst is in the low/hard state throughout with a truncated disk whereas the thermal disk emission dominates during the second outbu…
We carried out a detailed study of the temporal and broadband spectral behaviour of one of the brightest misaligned active galaxies in gamma-rays, NGC 1275 utilising 11 years of Fermi, and available Swift and AstroSat observations. Based on the cumulative flux distribution of the gamma-ray lightcurve, we identified four distinct activity states and noticed an increase in the baseline flux during the first three states. Similar nature of the increase in the average flux was also noticed in X-ray and UV bands. A large flaring activity in gamma-rays was noticed in the fourth state. The source was…
In $2016-17$, the Galactic transient black hole candidate GRS 1716-249 exhibited an outburst event after a long period of quiescence of almost 23 years. The source remained in the outbursting phase for $\sim 9$ months. We study the spectral and temporal properties of the source during this outburst using archival data from four astronomy satellites, namely MAXI, Swift, NuSTAR and AstroSat. Initial spectral analysis is done using combined disk black body and power-law models. For a better understanding of the accretion flow properties, we studied spectra with the physical two component advectiv…
A comprehensive study of the nucleus and western hotspot of Pictor A is carried out using AstroSat observations, 13 years of Fermi, and archival Swift observations, along with other published data. We report the first detection of the western hotspot of Pictor A in the far-UV band using observations from AstroSat-UVIT. The broad-band SED of the western hotspot is explained by a multizone emission scenario where X-ray emission is caused by synchrotron emission process in the substructures embedded in the diffuse region, while the emission in radio to optical is caused by synchrotron emission pr…
Aims: Flip-flops are top-hat-like X-ray flux variations which occur in some transient accreting black hole binary systems and feature simultaneous changes in the spectral hardness and the Power Density Spectrum (PDS). They occur at a crucial time in the evolution of these systems, when the accretion disk emission starts to dominate over coronal emission. Flip-flops have only rarely been observed and are poorly understood. Methods: We detect 15 flip-flops in the 2018 outburst of Swift J1658.2-4242, in observations by XMM-Newton, NuSTAR, Astrosat, Swift, Insight-HXMT, INTEGRAL, and ATCA. We anal…
In this paper, we employ Machine Learning algorithms on multi-mission observations for the classification of accretion states of outbursting Black hole X-ray binaries for the first time. Archival data from RXTE, Swift, MAXI and AstroSat observatories are used to generate the hardness intensity diagrams (HIDs) for outbursts of the sources XTE J1859+226 (1999 outburst), GX 339-4 (2002, 2004, 2007 and 2010 outbursts), IGR J17091-3624 (2016 outburst), and MAXI J1535-571 (2017 outburst). Based on variation of X-ray flux, hardness ratios, presence of various types of Quasi-periodic Oscillations (QPO…
Accreting X-ray pulsars (XRPs) undergo luminous X-ray outbursts during which the luminosity-dependent spectral and timing features of the neutron star's emission can be analyzed in detail, thus shedding light on the accretion regime at work. We took advantage of a monitoring campaign performed with NuSTAR, Swift/XRT, AstroSat and NICER, to follow the Be/X-ray Binary 2S 1553-542 along one of its rare outbursts and trace its spectral and timing evolution. We report the discovery of a luminosity-dependent cyclotron line energy for the first time in this source. The pulse profiles and pulsed fract…
We report spectral analysis of the persistent black hole X-ray binary, 4U 1957+115, using AstroSat, Swift and NuSTAR observations carried out between 2016-2019. Modelling with a disk emission, thermal comptonization and blurred reflection components revealed that the source was in the high soft state with the disk flux $\sim 87$ % of the total and high energy photon index $\sim2.6$. There is an evidence that either the inner disk radius varied by $\sim25$ % or the colour hardening factor changed by $\sim12$ %. The values of the inner disk radius imply that for a non-spinning black hole, the bl…
The origins of X-ray and radio emissions during an X-ray binary outburst are comparatively better understood than those of ultraviolet, optical and infrared radiation. This is because multiple competing mechanisms peak in these mid-energy ranges. Ascertaining the true emission mechanism and segregating the contribution of different mechanisms, if present, is important for correct understanding of the energetics of the system and hence its geometry. We have studied the multi-wavelength spectral energy distribution of the galactic X-ray binary GRS 1716-249 ranging from near infrared (0.0005 keV)…
We analyze X-ray light curves of the blazar Mrk 421 obtained from the Soft X-ray Imaging Telescope and the Large Area X-Ray Proportional Counter instrument onboard the Indian space telescope $AstroSat$ and archival observations from $Swift$. We show that the X-ray power spectral density (PSD) is a piece-wise power-law with a break, i.e., the index becomes more negative below a characteristic "break-timescale". Galactic black hole X-ray binaries and Seyfert galaxies exhibit a similar characteristic timescale in their X-ray variability that is proportional to their respective black hole mass. X-…
A precessing jet from a supermassive black hole: multi-wavelength observations of S5 1044+71
Université Paris Cité, CNRS, Astroparticule et Cosmologie（巴黎西岱大学，法国国家科学研究中心，粒子与宇宙学）；Institut d’Astrophysique Spatiale（天体物理研究所）；ZAH Landessternwarte, Universität Heidelberg（海德堡大学天文台）；Max-Planck-Institut für Kernphysik（马克斯·普朗克核物理研究所）；ICRANet-Armenia（ICRANet亚美尼亚）
