Enhanced optical activity 12 days before X-ray activity, and a 4 day X-ray delay during outburst rise, in a low-mass X-ray binary
A. J. Goodwin, D. M. Russell, D. K. Galloway, M. C. Baglio, A. S. Parikh, D. A. H. Buckley, J. Homan, D. M. Bramich, J. J. M. in 't Zand, C. O. Heinke, E. J. Ko… 展开作者
A. J. Goodwin, D. M. Russell, D. K. Galloway, M. C. Baglio, A. S. Parikh, D. A. H. Buckley, J. Homan, D. M. Bramich, J. J. M. in 't Zand, C. O. Heinke, E. J. Kotze, D. de Martino, A. Papitto, F. Lewis, R. Wijnands
X-ray transients, such as accreting neutron stars, periodically undergo outbursts, thought to be caused by a thermal-viscous instability in the accretion disk. Usually outbursts of accreting neutron stars are identified when the accretion disk has undergone an instability, and the persistent X-ray flux has risen to a threshold detectable by all sky monitors on X-ray space observatories. Here we present the earliest known combined optical, UV, and X-ray monitoring observations of the outburst onset of an accreting neutron star low mass X-ray binary system. We observed a significant, continuing increase in the optical i'-band magnitude starting on July 25, 12 days before the first X-ray detection with Swift/XRT and NICER (August 6), during the onset of the 2019 outburst of SAX J1808.4-3658. We also observed a 4 day optical to X-ray rise delay, and a 2 day UV to X-ray delay, at the onset of the outburst. We present the multiwavelength observations that were obtained, discussing the theory of outbursts in X-ray transients, including the disk instability model, and the implications of the delay. This work is an important confirmation of the delay in optical to X-ray emission during the onset of outbursts in low mass X-ray binaries, which has only previously been measured with less sensitive all sky monitors. We find observational evidence that the outburst is triggered by ionisation of hydrogen in the disk.
A pictorial atlas of the spectroscopic evolution at optical wavelengths is presented for the first 18 days of the 2021 outburst of the recurrent nova RS Oph, prior to the emergence of high ionization emission lines. The spectra presented here have been obtained at daily cadence with the Asiago 1.22m + B&C (3200-7900 Ang, 2.3 Å/pix) and Varese 0.84m + Echelle telescopes (4250-8900 Å, resolving power 18,000). The spectra have been fully calibrated in IRAF, absolutely fluxed, and heliocentric corrected. The Echelle spectra have been also corrected for telluric absorptions.
We present the earliest available soft X-ray observations of XTE J1810-187, the prototypical transient magnetar, obtained 75--84 days after its 2018 outburst with the Neutron Star Interior Composition Explorer (NICER). Using a series of observations covering eight days we find that its decreasing X-ray flux is well-described by either a blackbody plus power-law or a two-blackbody spectral model. The 2-10 keV flux of the source varied from (1.206+/-0.007)x10^{-10} to (1.125+/-0.004)x10^{-10} erg s^{-1} cm^{-2}, a decrease of about 7% within our observations and 44% from that measured 7-14 days …
We present results from quasi-simultaneous multiwavelength observations of the Galactic black hole X-ray transient MAXI J1820$+$070 during the decay of the 2018 outburst and its entire subsequent mini-outburst in March 2019. We fit the X-ray spectra with phenomenological and Comptonizaton models and discuss the X-ray spectral evolution comparing with the multiwavelength behaviour of the system. The system showed a rebrightening in UV/Optical/NIR bands 7-days after the soft-to-hard transition during the main outburst decay while it was fading in X-rays and radio. In contrast, the mini-outburst …
AX J0049.4-7323 is a Be/X-ray binary that shows an unusual and poorly understood optical variability that consists of periodic and bright optical outbursts, simultaneous with X-ray outbursts, characterised by a highly asymmetric profile. The periodicity of the outbursts is thought to correspond to the orbital period of the neutron star. To understand the behaviour shown by this source, we performed the first multi-wavelength monitoring campaign during the periastron passage of December 2017. The monitoring lasted for ~37 days and consisted of X-ray, near-ultraviolet, and optical data from the …
Evolution of variability properties of Galactic transient sources is a diagnostic tool to understand various regimes of the accretion flow and its dynamics close to the central black hole. In this paper, we concentrate on the variability properties of the X-ray transient XTE J1650-500 and investigate the evolution of viscous delay, time lag, QPO frequency, and their energy dependence throughout the rising phase as observed by RXTE during its outburst in 2001. Our analysis reveals (1) a delay of 12 \pm 1 days between one day averaged hard (5-12 keV) and soft (1.5-3 keV) photon light-curves as o…
Simulations on the collision between debris stream and outer dusty torus: a possible channel for forming fast-rise and long-delayed radio outburst in tidal disruption events
MAXI J1807+132 is an X-ray transient discovered during the decay of an outburst in 2017. We present optical and X-ray monitoring of the source over more than 125 days, from outburst to quiescence. The outburst decay is characterized by the presence of several re-flares with a quasi-periodic recurrence time of $\sim 6.5$ days. We detect broad H and He emission lines during outburst, characteristic of transient low mass X-ray binaries. These emission lines show strong variability from epoch to epoch and, in particular, during the early stages are found embedded into deep and very broad absorptio…
Transient LMXBs that host neutron stars (NSs) provide excellent laboratories for probing the dense matter physics present in NS crusts. During accretion outbursts in LMXBs, exothermic reactions may heat the NS crust, disrupting the crust-core equilibrium. When the outburst ceases, the crust cools to restore thermal equilibrium with the core. Monitoring this evolution allows us to probe the dense matter physics in the crust. Properties of the deeper crustal layers can be probed at later times after the end of the outburst. We report on the unexpected late-time temperature evolution (>2000 days …
Chandra and RXTE Observations of 1E 1547.0-5408: Comparing the 2008 and 2009 Outbursts
我们目前的结果，从观测磁星1 E 1547.0-5408（SGR J1550-5418）采取的钱德拉X射线天文台和罗西X射线定时探测器（RXTE）后，源的爆发在2008年10月和2009年1月。在钱德拉观测的时间跨度（分别涵盖2008年和2009年事件后的第4天至第23天和第2天至第16天）期间，源光谱形状保持稳定，而脉冲星在2008年同一时间段的自旋下降率增加了2.2倍。光谱变化的缺乏表明磁星自旋下降和辐射变化之间的解耦，因此自旋下降推断的磁场强度和推断光谱之间。我们还发现，在2008年和2009年的钱德拉数据中，相位平均通量和脉冲分数之间存在很强的反相关性，但在2008年之前的测量中没有。我们讨论这些结果的背景下的磁星模型。
SXP4.78 was originally discovered in 2000 as a pulsar in the Small Magellanic Cloud (SMC) by the Rossi X-ray Timing Explorer (RXTE) but it was not spatially located at that time. A new detection in 2018 with the Neil Gehrels Swift Observatory during a Type II outburst permitted its position to be accurately located and its optical counterpart identified. We report X-ray and optical monitoring covering epochs before and during the outburst. Using photometric data we show the long-term variability of the Be disc where we present flux and colour changes associated with the disc growth and decay o…
Hour time-scale QPOs in the X-ray and radio emission of LS I +61$^{\circ}$303
LS I +61 $^{\circ}$ 303是一颗X射线双星，每27天会有一次射电爆发。先前对该恒星系统的研究揭示了叠加在大型射电爆发上的射电微耀斑。本文介绍了利用Westerbork综合射电望远镜（WSRT）对LS I +61 $^{\circ}$ 303进行的2.2 GHz射电观测。使用各种定时分析方法，我们发现显着的准周期振荡（QPO）的55分钟稳定超过4天的持续时间。我们还使用从朱雀卫星获得的X射线波长的档案数据。我们在这里报告的第一次显着的X射线QPO约2小时，目前超过21小时的时间跨度。我们将我们的结果与之前报道的QPO观测结果进行了比较，得出的结论是QPO似乎与射电爆发有关，而与爆发的幅度无关。最后，在磁重联的背景下讨论了不同的QPO时间尺度。
Outbursts from cataclysmic variables, such as dwarf novae (DNe), are prevalent throughout the galaxy and are known to emit strongly in the ultraviolet (UV). However, the UV emission of DNe has not been studied extensively compared with the optical. Characterising in detail the physical processes responsible for DN outburst behaviour requires further UV data. Here we report, as part of our recently launched Transient UV Objects Project (TUVO), the discovery of TUVO-21acq, a new transient which we detected in the UV using data from the Ultraviolet Optical Telescope aboard Swift. We detected two …
We present the discovery that ASASSN-14ko is a periodically flaring AGN at the center of the galaxy ESO 253-G003. At the time of its discovery by the All-Sky Automated Survey for Supernovae (ASAS-SN), it was classified as a supernova close to the nucleus. The subsequent six years of V- and g-band ASAS-SN observations reveal that ASASSN-14ko has nuclear flares occurring at regular intervals. The seventeen observed outbursts show evidence of a decreasing period over time, with a mean period of $P_0 = 114.2 \pm 0.4$ days and a period derivative of $\dot{P} = -0.0017\pm0.0003$. The most recent out…
Two long AstroSat Soft X-ray Telescope observations were taken of the third recorded outburst of the Symbiotic Recurrent Nova, V3890 Sgr. The first observing run, 8.1-9.9 days after the outburst, initially showed a stable intensity level with a hard X-ray spectrum that we attribute to shocks between the nova ejecta and the pre-existing stellar companion. On day 8.57, the first, weak, signs appeared of Super Soft Source (SSS) emission powered by residual burning on the surface of the White Dwarf. The SSS emission was observed to be highly variable on time scales of hours. After day 8.9, the SSS…
The flash-ionised SN Ibn 2025kzr: H-free CSM formed during a precursor outburst 55 days prior to explosion
DTU Space, Technical University of Denmark（丹麦技术大学空间中心）；South African Astronomical Observatory（南非天文台）；Department of Astronomy, University of Cape Town（开普敦大学天文学系）；Department of Physics, University of the Free State（自由邦大学物理系）；Department of Physics, Stellenbosch University（斯坦伦布什大学物理系）；Department of Astrophysics/IMAPP, Radboud University（拉德堡德大学天体物理学系/IMAPP）；The Inter-University Institute for Data Intensive Astronomy, University of Cape Town（开普敦大学跨大学数据密集型天文研究所）；Department of Particle Physics and Astrophysics, Weizmann Institute of Science（魏茨曼科学研究所粒子物理与天体物理系）
