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Register a new userLong term X-ray variability characteristics of the narrow-line Seyfert 1 galaxy RE~J1034+396
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We present the results of our study of the long term X-ray variability characteristics of the Narrow Line Seyfert 1 galaxy RE J1034+396. We use data obtained from the AstroSat satellite along with the light curves obtained from XMM-Newton and Swift-XRT. We use the 0.3 - 7.0 keV and 3 - 20 keV data, respectively, from the SXT and the LAXPC of AstroSat. The X-ray spectra in the 0.3 - 20 keV region are well fit with a model consisting of a power-law and a soft excess described by a thermal-Compton emission with a large optical depth, consistent with the earlier reported results. We have examined the X-ray light curves in the soft and hard X-ray bands of SXT and LAXPC, respectively, and find that the variability is slightly larger in the hard band. To investigate the variability characteristics of this source at different time scales, we have used X-ray light curves obtained from XMM-Newton data (200 s to 100 ks range) and Swift-XRT data (1 day to 100 day range) and find that there are evidences to suggest that the variability sharply increases at longer time scales. We argue that the mass of the black hole in RE J1034+396 is likely to be $sim$3 $times$ 10$^6$ M$_odot$, based on the similarity of the observed QPO to the high frequency QPO seen in the Galactic black hole binary, GRS 1915+105.
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We analyse eight XMM-Newton observations of the bright Narrow-Line Seyfert 1 galaxy Arakelian 564 (Ark 564). These observations, separated by ~6 days, allow us to look for correlations between the simultaneous UV emission (from the Optical Monitor) with not only the X-ray flux but also with the different X-ray spectral parameters. The X-ray spectra from all the observations are found to be adequately fitted by a double Comptonization model where the soft excess and the hard X-ray power law are represented by thermal Comptonization in a low temperature plasma and hot corona, respectively. Apart from the fluxes of each component, the hard X-ray power law index is found to be variable. These results suggest that the variability is associated with changes in the geometry of the inner region. The UV emission is found to be variable and well correlated with the high energy index while the correlations with the fluxes of each component are found to be weaker. Using viscous time-scale arguments we rule out the possibility that the UV variation is due to fluctuating accretion rate in the outer disc. If the UV variation is driven by X-ray reprocessing, then our results indicate that the strength of the X-ray reprocessing depends more on the geometry of the X-ray producing inner region rather than on the X-ray luminosity alone.
The ultra-soft narrow-line Seyfert 1 galaxy 1H 0707-495 is a well-known and highly variable active galactic nucleus (AGN), with a complex, steep X-ray spectrum, and has been studied extensively with XMM-Newton. 1H 0707-495 was observed with the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) aboard the Spectrum-Roentgen-Gamma (SRG) mission on October 11, 2019, for about 60,000 seconds as one of the first calibration and pointed verification phase (CalPV) observations. The eROSITA light curves show significant variability in the form of a flux decrease by a factor of 58 with a 1 sigma error confidence interval between 31 and 235. This variability is primarily in the soft band, and is much less extreme in the hard band. No strong ultraviolet variability has been detected in simultaneous XMM-Newton Optical Monitor observations. The UV emission is about 10^44 erg s^-1, close to the Eddington limit. 1H 0707-495 entered the lowest hard flux state seen in 20 years of XMM-Newton observations. In the eROSITA All-Sky Survey (eRASS) observations taken in April 2020, the X-ray light curve is still more variable in the ultra-soft band, but with increased soft and hard band count rates more similar to previously observed flux states. A model including relativistic reflection and a variable partial covering absorber is able to fit the spectra and provides a possible explanation for the extreme light-curve behaviour. The absorber is probably ionised and therefore more transparent to soft X-rays. This leaks soft X-rays in varying amounts, leading to large-amplitude soft-X-ray variability.
We present the first results from a detailed analysis of a new, long ($sim100$ ks) XMM-Newton observation of the narrow-line Seyfert 1 galaxy PG 1404$+$226 which showed a large-amplitude, rapid X-ray variability by a factor of $sim7$ in $sim10$ ks with an exponential rise and a sharp fall in the count rate. We investigate the origin of the soft X-ray excess emission and rapid X-ray variability in the source through time-resolved spectroscopy and fractional root-mean-squared (rms) spectral modeling. The strong soft X-ray excess below 1 keV observed both in the time-averaged and time-resolved spectra is described by the intrinsic disk Comptonization model as well as the relativistic reflection model where the emission is intensive merely in the inner regions ($r_{rm in}<1.7 r_{rm g}$) of an ionized accretion disk. We detected no significant UV variability while the soft X-ray excess flux varies together with the primary power-law emission (as $F_{{rm primary}}propto F_{{rm excess}}^{1.54}$), although with a smaller amplitude, as expected in the reflection scenario. The observed X-ray fractional rms spectrum is approximately constant with a drop at $sim0.6$ keV and is described by a non-variable emission line component with the observed energy of $sim0.6$ keV and two variable spectral components: a more variable primary power-law emission and a less variable soft excess emission. Our results suggest the `lamppost geometry for the primary X-ray emitting hot corona which illuminates the innermost accretion disk due to strong gravity and gives rise to the soft X-ray excess emission.
We present for the first time the timing and spectral analyses for a narrow-line Seyfert 1 galaxy, SBS 1353+564, using it{XMM-Newton} and it{Swift} multi-band observations from 2007 to 2019. Our main results are as follows: 1) The temporal variability of SBS 1353+564 is random, while the hardness ratio is relatively constant over a time span of 13 years; 2) We find a prominent soft X-ray excess feature below 2 keV, which cannot be well described by a simple blackbody component; 3) After comparing the two most prevailing models for interpreting the origin of the soft X-ray excess, we find that the relativistically smeared reflection model is unable to fit the data above 5 keV well and the X-ray spectra do not show any reflection features, such as the Fe Kalpha emission line. However, the warm corona model can obtain a good fitting result. For the warm corona model, we try to use three different sets of spin values to fit the data and derive different best-fitting parameter sets; 4) We compare the UV/optical spectral data with the extrapolated values of the warm corona model to determine which spin value is more appropriate for this source, and we find that the warm corona model with non-spin can sufficiently account for the soft X-ray excess in SBS 1353+564.
We present joint textit{XMM-Newton} and textit{NuSTAR} observations of the `bare narrow line Seyfert 1 Ton S180 ($z=0.062$), carried out in 2016 and providing the first hard X-ray view of this luminous galaxy. We find that the 0.4--30 keV band cannot be self-consistently reproduced by relativistic reflection models, which fail to account simultaneously for the soft and hard X-ray emission. The smooth soft excess prefers extreme blurring parameters, confirmed by the nearly featureless nature of the RGS spectrum, while the moderately broad Fe K line and the modest hard excess above 10 keV appear to arise in a milder gravity regime. By allowing a different origin of the soft excess, the broadband X-ray spectrum and overall spectral energy distribution (SED) are well explained by a combination of: (a) direct thermal emission from the accretion disc, dominating from the optical to the far/extreme UV; (b) Comptonization of seed disc photons by a warm ($kT_{rm e}sim0.3$ keV) and optically thick ($tausim10$) corona, mostly contributing to the soft X-rays; (c) Comptonization by a standard hot ($kT_{rm e} gtrsim 100$ keV) and optically thin ($tau<0.5$) corona, responsible for the primary X-ray continuum; and (d) reflection from the mid/outer part of the disc. The two coronae are suggested to be rather compact, with $R_{rm hot} lesssim R_{rm warm} lesssim 10$ R$_{rm g}$. Our SED analysis implies that Ton S180 accretes at super-Eddington rates. This is a key condition for the launch of a wind, marginal (i.e., 3.1$sigma$ significance) evidence of which is indeed found in the RGS spectrum.
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