arXiv subjects

M. Mehdipour

Publications and source records attributed to M. Mehdipour.

75 records · Page 5Linked to original sources

arXiv2011

Multiwavelength campaign on Mrk 509. V. Chandra-LETGS observation of the ionized absorber

We present here the results of a 180 ks Chandra-LETGS observation as part of a large multi-wavelength campaign on Mrk 509. We study the warm absorber in Mrk 509 and use the data from a simultaneous HST-COS observation in order to assess whether the gas responsible for the UV and X-ray absorption are the same. We analyzed the LETGS X-ray spectrum of Mrk 509 using the SPEX fitting package. We detect several absorption features originating in the ionized absorber of the source, along with resolved emission lines and radiative recombination continua. The absorption features belong to ions with, at least, three distinct ionization degrees. The lowest ionized component is slightly redshifted (v = +73 km/s) and is not in pressure equilibrium with the others, and therefore it is not likely part of the outflow, possibly belonging to the interstellar medium of the host galaxy. The other components are outflowing at velocities of -196 and -455 km/s, respectively. The source was observed simultaneously with HST-COS, finding 13 UV kinematic components. At least three of them can be kinematically associated with the observed X-ray components. Based on the HST-COS results and a previous FUSE observation, we find evidence that the UV absorbing gas might be co-located with the X-ray absorbing gas and belong to the same structure.

astro-ph.CO↗

arXiv2011

Multiwavelength campaign on Mrk 509. VI. HST/COS observations of the far-ultraviolet spectrum

We present medium resolution (R~20,000) HST/COS ultraviolet spectra covering 1155-1760 A of the Seyfert 1 Mrk 509 obtained simultaneously with a Chandra/LETGS spectrum as part of a multiwavelength campaign in 2009 that included observations with XMM-Newton, SWIFT, and Integral. Our high S/N spectrum detects additional complexity in the absorption troughs from a variety of sources in Mrk 509, including the outflow from the active nucleus, the ISM and halo of the host galaxy, and infalling clouds or stripped gas from a merger that are illuminated by the AGN. Variability between the STIS and COS observation of the -400 km/s component allows us to set an upper limit on its distance of < 250 pc. Similarly, variability of a component at +150 km/s between two prior FUSE observations limits its distance to < 1.5 kpc. The UV absorption only partially covers the emission from the AGN nucleus. Covering fractions are lower than those previously seen with STIS, and are comparable to those seen with FUSE. Given the larger apertures of COS and FUSE compared to STIS, we favor scattered light from an extended region near the AGN as the explanation for the partial covering. As observed in prior X-ray and UV spectra, the UV absorption has velocities comparable to the X-ray absorption, but the bulk of the ultraviolet absorption is in a lower ionization state with lower total column density than the gas responsible for the X-ray absorption. We conclude that the outflow from the active nucleus is a multiphase wind.

astro-ph.CO↗

arXiv2010

The warm absorber and X-ray variability of the Seyfert 1 galaxy NGC 3516 as seen by the XMM-Newton RGS

We present a new analysis of the soft and medium energy X-ray spectrum of the Seyfert 1 galaxy NGC 3516 taken with the Reflection Grating Spectrometer (RGS) and European Photon Imaging Camera (EPIC) on board the XMM-Newton observatory. We examine four observations made in October 2006. We investigate whether the observed variability is due to absorption by the warm absorber and/or is intrinsic to the source emission. We analyse in detail the EPIC-pn and RGS spectra of each observation separately. The warm absorber in NGC 3516 is found to consist of three phases of ionisation, two of which have outflow velocities of more than 1000 km/s. The third phase (the least ionised one) is much slower at 100 km/s. One of the high ionisation phases, with log xi of 2.4, is found to have a partial covering fraction of about 60%. It has previously been suggested that the passage of a cloud, part of a disk wind, in front of the source (producing a change in the covering fraction) was the cause of a significant dip in the lightcurve during one of the observations. From our modelling of the EPIC-pn and RGS spectra, we find that variation in the covering fraction cannot be solely responsible for this. We show that intrinsic change in the source continuum plays a much more significant role in explaining the observed flux and spectral variability than originally thought.

astro-ph.CO↗