41 research outputs found
The XMM Cluster Survey: Present status and latest results
The XMM Cluster Survey (XCS) is a serendipitous search for galaxy clusters using all publicly available data in the XMMâ Newton Science Archive. Our recent first data release (XCSâDR1) contains 503 optically confirmed groups and clusters, among which 256 new to the literature and 357 whose Xâray emission was detected for the first time. We discuss their properties and provide an update on the work being done. As examples of the applications of XCSâDR1, we mention the 17 fossil groups/clusters identified with the help of the Sloan Digital Sky Survey. Their brightest galaxies have stellar populations and starâformation histories which are similar to normal brightest cluster galaxies, but their stellar masses are significantly larger and correspond to a much bigger fraction of the total group/cluster optical luminosity. We also highlight the 15 clusters expected tobe also detected by the Planck satellite, and characterize the expected overlap between the final XCS and Planck cluster catalogues. (© 2013 WILEYâVCH Verlag GmbH & Co. KGaA, Weinheim)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98104/1/462_ftp.pd
Black Hole Results from XMM-Newton
XMM-Newton is one of the most successful science missions of the European Space Agency. Since 2003 every year about 300 articles are published in refereed journals making directly use of XMM-Newton data. All XMM-Newton calls for observing proposals are highly oversubscribed by factors of six and more. In the following some scientic highlights of XMM-Newton observations of black holes are summarized
The Nature of the Broad--Line--Region in the Radio--Loud AGN 3C390.3
We present an analysis of the ultraviolet and X-Ray variability of the Broad-
Line-Radio Galaxy 3C390.3 over 15 years. The UV continuum showed large
variations with amplitudes of up to a factor of 10. We find: (1) The variations
of CIV and Ly_alpha are highly correlated with the UV continuum, and are
delayed with respect to the continuum variations by 50-110 days with the red
wing of both CIV and Ly_alpha , leading the blue wing; (2) The CIV/Ly_alpha
ratio is positively correlated with both the continuum flux and UV line
strength, a behavior different from other AGNs studied so far; (3) The blue
sides of the Ly_alpha and CIV profiles are similar to the blue side of the
Balmer lines, while the red sides are different, suggesting a different origin
for the red peak in the Balmer lines. Our results suggest: (1) The broad CIV
and Ly_alpha emitting gas is infalling towards the central object; (2) The
overall behaviour of the CIV/Ly_alpha ratio and the absence of a big blue bump,
strongly indicate the coexistence of optically thick as well as optically thin
BLR clouds; (3) Assuming circular symmetry and predominantly circular motion,
the BLR gas is situated at 8325 lightdays from the central source; (4)
Under these assumptions and with the derived circular velocity of 2850 km s, the central mass inside this radius is confined to
; (6) Comparing our results with
those obtained from VLBI and observations of the Fe line, suggests
the association of the BLR with a disk, inclined at 9812 degrees with
respect to the direction of superluminal motion of the radio blobs.Comment: MNRAS in pres
Finding AGN in Deep X-ray Flux States with Swift
We report on our ongoing project of finding Active Galactic Nuclei (AGN) that
go into deep X-ray flux states detected by Swift. Swift is performing an
extensive study on the flux and spectral variability of AGN using Guest
Investigator and team fill-in programs followed by triggering XMM_Newton for
deeper follow-up observations. So far this program has been very successful and
has led to a number of XMM-Newton follow up observations, including Mkn 335, PG
0844+349, and RX J2340.8-5329. Recent analysis of new Swift AGN observations
reveal several AGN went into a very low X-ray flux state, particularly
Narrow-Line Seyfert 1 galaxies. One of these is RX J2317-4422, which dropped by
a factor of about 60 when compared to the ROSAT All-Sky Survey.Comment: 6 pages, 3 figures, Proceedings of the "10 Years of Swift" Meeting
held in Rome in December 2014. Submitted to Po
A Huge Drop in X-ray Luminosity of the Non-Active Galaxy RXJ1242.6-1119A, and First Post-Flare Spectrum - Testing the Tidal Disruption Scenario
It has been suggested that an unavoidable consequence of the existence of
supermassive black holes, and the best diagnostic of their presence in
non-active galaxies, would be occasional tidal disruption of stars captured by
the black holes. These events manifest themselves in form of luminous flares
powered by accretion of debris from the disrupted star into the black hole.
Candidate events among optically non-active galaxies emerged in the past few
years. For the first time, we have looked with high spatial and spectral
resolution at one of these most extreme variability events ever recorded among
galaxies. Here, we report measuring a factor ~200 drop in luminosity of the
X-ray source RXJ 1242-1119 with the X-ray observatories Chandra and XMM-Newton,
and perform key tests of the favored outburst scenario, tidal disruption of a
star by a supermassive black hole. We show that the detected `low-state'
emission has properties such that it must still be related to the flare. The
power-law shaped post-flare X-ray spectrum indicates a `hardening' compared to
outburst. The inferred black hole mass, the amount of liberated energy, and the
duration of the event favor an accretion event of the form expected from the
(partial or complete) tidal disruption of a star (abstract abbreviated).Comment: to appear in March 1 issue of ApJ Letters (submitted Nov. 10,
accepted in Dec. 2003); background information available at
http://www.xray.mpe.mpg.de/~skomossa
The outburst of the changing-look AGN IRAS23226-3843 in 2019
IRAS23226-3843 has previously been classified as a changing-look AGN based on
X-ray and optical spectral variations. In 2019, Swift observations revealed a
strong rebrightening in X-ray and UV fluxes in comparison to observations in
2017. We took follow-up Swift, XMM-Newton, and NuSTAR observations together
with optical spectra (SALT and SAAO 1.9m telescope) from 2019 until 2021.
IRAS23226-3843 showed a strong X-ray and optical outburst in 2019. It varied in
the X-ray and optical continuum by a factor of 5 and 1.6, respectively, within
two months. This corresponds to a factor of 3 in the optical after correction
for the host galaxy contribution. The Balmer and FeII emission-line intensities
showed comparable variability amplitudes. The Halpha profiles changed from a
blue-peaked profile in the years 1997 and 1999 to a broad double-peaked profile
in 2017 and 2019. However, there were no major profile variations in the
extremely broad double-peaked profiles despite the strong intensity variations
in 2019. One year after the outburst, the optical spectral type changed and
became a Seyfert type 2 in 2020. Blue outflow components are present in the
Balmer lines and in the Fe band in the X-rays. A deep broadband
XMM-Newton/NuSTAR spectrum was taken during the maximum state in 2019. This
spectrum is qualitatively very similar to a spectrum taken in 2017, but by a
factor of 10 higher. The soft X-ray band appears featureless. The soft excess
is well modeled with a Comptonization model. A broadband fit with a power-law
continuum, Comptonized soft excess, and Galactic absorption gives a good fit to
the combined EPIC-pn and NuSTAR spectrum. In addition, we see a complex and
broadened Fe K emission-line profile in the X-rays. The changing-look character
in IRAS23226-3843 is most probably caused by changes in the accretion rate --
based on the short-term variations on timescales of weeks to months.Comment: 21 pages, 14 figures, Astronomy & Astrophysics in pres