اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدStrong UV and X-ray variability of the Narrow Line Seyfert 1 Galaxy WPVS 007 -- on the nature of the X-ray low state
150
0
0.0
(
0
)
تأليف
Dirk Grupe
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We report on multi-wavelength observations of the X-ray transient Narrow Line Seyfert 1 (NLS1) galaxy WPVS 007. The galaxy was monitored with Swift between October 2005 and July 2013, after it had undergone a dramatic drop in its X-ray flux earlier. For the first time, we are able to repeatedly detect this NLS1 in X-rays again. This increased number of detections in the last couple of years may suggest that the strong absorber that has been found in this AGN is starting to become leaky, and may eventually disappear. The X-ray spectra obtained for WPVS 007 are all consistent with a partial covering absorber model. A spectrum based on the data during the extreme low X-ray flux states shows that the absorption column density is of the order of 4 x 10^23 cm^-2 with a covering fraction of 95%. WPVS 007 also displays one of the strongest UV variabilities seen in Narrow Line Seyfert 1s. The UV continuum variability anti-correlates with the optical/UV slope alpha-UV which suggests that the variability primarily may be due to reddening. The UV variability time scales are consistent with moving dust `clouds located beyond the dust sublimation radius of approximately 20 ld. We present for the first time near infrared JHK data of WPVS 007, which reveal a rich emission-line spectrum. Recent optical spectroscopy does not indicate significant variability in the broad and FeII emission lines, implying that the ionizing continuum seen by those gas clouds has not significantly changed over the last decades. All X-ray and UV observations are consistent with a scenario in which an evolving Broad Absorption Line (BAL) flow obscures the continuum emission. As such, WPVS 007 is an important target for our understanding of BAL flows in low-mass active galactic nuclei (AGN).
قيم البحث
اقرأ أيضاً
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) w
ith 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.
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-X
RT. 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.
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 wi
th 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 detailed broadband UV/optical to X-ray spectral variability of the Seyfert 1 galaxy 1H 0419-577 using six XMM-Newton observations performed during 2002-2003. These observations covered a large amplitude variability event in which the soft
X-ray (0.3-2 keV) count rate increased by a factor of ~4 in six months. The X-ray spectra during the variability are well described by a model consisting of a primary power law, blurred and distant reflection. The 2-10 keV power-law flux varied by a factor ~7 while the 0.3-2 keV soft X-ray excess flux derived from the blurred reflection component varied only by a factor of ~2. The variability event was also observed in the optical and UV bands but the variability amplitudes were only at the 6-10% level. The variations in the optical and UV bands appear to follow the variations in the X-ray band. During the rising phase, the optical bands appear to lag behind the UV band but during the declining phase, the optical bands appear to lead the UV band. Such behavior is not expected in the reprocessing models where the optical/UV emission is the result of reprocessing of X-ray emission in the accretion disc. The delayed contribution of the broad emission lines in the UV band or the changes in the accretion disc/corona geometry combined with X-ray reprocessing may give rise to the observed behavior of the variations.
It is arguably in the X-ray regime that Narrow-line Seyfert 1 galaxies (NLS1s) exhibit the most extreme behaviour. Spectral complexity, rapid and large amplitude flux variations, and exceptional spectral variability are well known characteristics. Ho
wever, NLS1s are not eccentric, but form a continuous sequence with typical Seyfert 1 galaxies. Understanding the extreme behaviour displayed by NLS1s will provide insight to the general AGN phenomenon. In this review, I will examine some of the important NLS1 X-ray discoveries over the past twenty years. I will then explore recent work that looks at the nature of the primary X-ray source (i.e. the corona) in NLS1s, demonstrating how the corona can be compact, dynamic, and in some cases consistent with collimated outflow. X-ray observations of NLS1s will be key in determining the nature of the corona, resolving the disc-jet connection, and determining the origin of the radio loud/quiet dichotomy in AGN.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
