Related papers: Outburst Morphology in the Soft X-ray Transient Aq…
We present a model of a viscously evolving accretion disc around a magnetized neutron star. The model features the varying outer radius of the hot ionized part of the disc due to cooling and the varying inner radius of the disc due to…
We have found a new clue to the transition mechanism between optical high/X-ray off and optical low/X-ray on states of the LMC supersoft X-ray source RX J0513.9-6951. A sharp ~1 mag drop is common to the CI Aql 2000 outburst. These drops…
In this paper we report the long-term optical observation of the faint soft X-ray transient SAX J1810.8-2609 from OGLE and MOA. We have focused on the 2007 outburst, and also did the cross-correlate between its optical light curves and the…
We have discovered a spectral transition from the low/hard (LH) state to the high/soft (HS) state when Aquila X-1 was {\em declining} in observations made with the {\it Rossi X-Ray Timing Explorer (RXTE)}. The 2--200 keV energy flux…
We obtained R- and I-band CCD photometry of the soft X-ray transient/neutron- star binary Aql X-1 in 1998 June while it was at quiescence. We find that its light curve is dominated by ellipsoidal variations, although the ellipsoidal…
We study the 2018 outburst of Aql X-1 via the monitor of all sky X-ray image (MAXI) data. We show that the outburst starting in February 2018 is a member of short-low class in the frame of outburst duration and the peak count rate although…
We have studied the evolution of the Low Frequency Quasi-Periodic Oscillations (LFQPOs) during the rising phase of seven outbursts of the neutron star Soft X-ray Transient (SXT) Aql X$-$1 observed with the \textit{Rossi X-ray Timing…
We study the accretion/ejection processes (i.e. disc/jet coupling) in the neutron star X-ray binary Aquila X-1 via a multi-wavelength approach. We use in the radio band the publicly available VLA archive containing observations of the…
Accretion conditions and morphologies of X-ray transients containing neutron stars are still poorly understood. Circinus X-1 is an enigmatic case where we observe X-ray flux changes covering four orders of magnitude. We observed Circinus…
Context: To follow the early evolution of stars we need to understand how young stars accrete and eject mass. It is generally assumed that the FU Orionis phenomenon is related to the variations in the disk accretion, but many questions…
We show that a typical X-ray outburst light curve of Aql X-1 can be reproduced by accretion onto the neutron star in the frame of the disk instability model without invoking partial accretion or propeller effect. The knee and the subsequent…
We present a deep study of the long-term X-ray light curve of 4U 1608-52 by investigating the fast rising exponential decay (FRED) outbursts, low intensity state (LIS) and quiescent intervals. By calibrating the onset times of the…
We report on a long-term optical monitoring of the neutron star X-ray binary Centaurus X-4 performed during the last 13.5 years. This source has been in quiescence since its outburst in 1979. Our monitoring reveals the overall evolution of…
The flat spectrum radio quasar (FSRQ) PKS 0208-512 underwent three outbursts at the optical-near-infrared (OIR) wavelengths during 2008-2011. The second OIR outburst did not have a gamma-ray counterpart despite being comparable in…
We suggest a new scenario to explain the outburst light curves of black hole soft X-ray transients together with the secondary maximum and the bump seen on their decay phases. Our explanations are based on the disk instability models…
I point to an interesting similarity in the radio and the soft X-ray light curves between the November 2009 outburst of the X-ray binary Aquila X-1 and some solar flares. The ratio of the soft X-ray and radio luminosities of Aquila X-1 in…
In the canonical understanding of transient X-ray sources the accretion during quiescence occurs via a geometrically thin disk in the outer part and via an advection-dominated hot coronal flow/ADAF in the inner part. The inner part…
We present a study of the evolution of the optical and X-ray fluxes during outbursts of two short-period cataclysmic variables, the confirmed intermediate polar CC Scl and the intermediate polar candidate FS Aur. We found that the X-ray and…
The occurrence of new FU Orionis-like objects is fundamental to understand the outburst mechanism in young stars and their role in star formation and disk evolution. Our work is aimed at investigating the properties of the recent outburst…
I briefly review the theory of soft X-ray transient systems. Irradiation of the accretion disc faces by the central X-ray source determines both the occurrence and the nature of the outbursts, in particular forcing these to be long viscous…