Related papers: Changing-look event in NGC 3516: continuum or obsc…

We present results on the location, physical conditions, and geometry of the outflow in the Seyfert 1 galaxy NGC 3783 from a study of the variable intrinsic UV absorption. Based on 18 observations with HST/STIS and 6 observations with FUSE,…

We report on multi-band observations of the transient source Swift J0840.7-3516, which was detected in outburst in 2020 February by the Neil Gehrels Swift Observatory. The outburst episode lasted just ~5 days, during which the X-ray…

We present results from RXTE data obtained during a systematic monitoring program of four Seyfert galaxies (NGC5548, NGC5506, MCG-6-30-15 and NGC4051). We studied the variability of three hardness ratios derived from the light curves in…

Spectroscopic data in wavelengths 900--3000A have been obtained in a low flux state of the nucleus of the Seyfert 1 galaxy NGC 3516. The line profiles show P Cygni characteristics, particularly in O VI 1032A, and are compared with data from…

We have observed four low-luminosity active galactic nuclei classified as Type 1 LINERs with the X-ray Telescope (XRT) and the UltraViolet-Optical Telescope (UVOT) onboard Swift, in an attempt to clarify the main powering mechanism of this…

We report on the first XMM-Newton observation of the highly X-ray variable, radio-quiet, Narrow-Line Seyfert 1 galaxy IRAS 13224-3809 obtained during the guaranteed time programme with a 64 ks exposure. The most remarkable spectral feature…

(Abridged) Active galactic nuclei show a wealth of interesting physical processes, some of which are poorly understood. We want to address a number of open questions, including the location and physics of the outflow from AGN, the nature of…

The Narrow Line Seyfert 1 galaxy NGC4051 shows unusual low flux states, lasting several months, when the 2-10 keV X-ray spectrum becomes unusually hard (photon index<1) while the spectrum at lower X-ray energies is dominated by a large soft…

The Be X-ray binary EXO 2030+375 was in an extended low luminosity state during most of 2016. We observed this state with NuSTAR and Swift, supported by INTEGRAL observations as well as optical spectroscopy with the NOT. We present a…

We present the results of a 17 ks Chandra observation of the nearby dwarf spiral galaxy NGC 4395, focusing on the X-ray properties of the moderate-mass black hole that resides in its nucleus. Chandra affords the first high-quality,…

We present optical observations of the low-luminosity Seyfert 1 nucleus of NGC 4395, as part of a multiwavelength reverberation-mapping program. Observations were carried out over two nights in 2004 April at Lick, Wise, and Kitt Peak…

CSS J102913+404220 is a peculiar narrow line Seyfert 1 galaxy with an energetic nuclear optical outburst. We present a detailed analysis of its multi-wavelength photometric and spectroscopic observations covering a period of decade since…

We report the results of two Chandra ACIS-S observations from February and August 2003 of the highly X-ray variable Narrow-Line Seyfert 1 galaxy RX J2217.9--5941. Observations spanning the time from the ROSAT All Sky Survey (RASS) through…

Mrk 590 is a Changing Look AGN currently in an unusual repeat X-ray and UV flaring state. Here, we report on deep X-ray observations with XMM-Newton, NuSTAR, and NICER, obtained at a range of X-ray flux levels. We detect a prominent soft…

We report on the XMM-Newton timing properties of the most X-ray variable, radio-quiet, NLS1 IRAS 13224-3809. IRAS 13224-3809 continues to display the extremely variable behavior that was previously observed with ROSAT and ASCA; however, no…

Using a geometry consisting of a hot central Comptonizing plasma surrounded by a thin accretion disk, we model the optical through hard X-ray spectral energy distributions of the type 1 Seyfert galaxies NGC 3516 and NGC 7469. As in the…

Spectroscopic observations of the low luminosity Seyfert 1 nucleus in NGC 3516 obtained with the Hubble Space Telescope show that the visible spectrum is dominated by the Balmer emission lines of Hydrogen (H) and a continuum luminosity that…

Swift has initiated a new era of understanding the extremes of active galactic nuclei (AGN) variability, their drivers and underlying physics. This is based on its rapid response, high sensitivity, good spatial resolution, and its ability…

The Seyfert 1 galaxy NGC4151 is characterized by complex X-ray absorption, well described by a dual absorber, composed of a uniform mildly ionized gas and a cold system that partially covers the central source. However, in one of the 5…

We present a spectroscopic analysis of XMM-Newton and NuSTAR observations of the 'complex' NLS1 PG 1535+547 at redshift $z=0.038$. These observations span three epochs: 2002 and 2006 with XMM-Newton alone, covering the $0.3-10$ keV energy…