189 research outputs found
Proving strong magnetic fields near to the central black hole in the quasar PG0043+039 via cyclotron lines
The optical luminous quasar PG0043+039 has not been detected before in deep
X-ray observations indicating the most extreme optical-to-X-ray slope index
of all quasars. This study aims to detect PG0043+039 in a deep
X-ray exposure. Furthermore, we wanted to check out whether this object shows
specific spectral properties in other frequency bands. We took deep X-ray
(XMM-Newton), far-ultraviolet (HST), and optical (HET, SALT telescopes) spectra
of PG0043+039 simultaneously in July 2013. We just detected PG0043+039 in our
deep X-ray exposure. The steep gradient is
consistent with an unusual steep gradient with
seen in the UV/far-UV continuum. The optical/UV
continuum flux has a clear maximum near 2500 {\AA}. The UV spectrum is very
peculiar because it shows broad humps in addition to known emission lines. A
modeling of these observed humps with cyclotron lines can explain their
wavelength positions, their relative distances, and their relative intensities.
We derive plasma temperatures of T 3keV and magnetic field strengths
of B 2 G for the line-emitting regions close to the
black hole.Comment: 4 pages, 3 figures, Astronomy & Astrophysics in pres
Space Astronomy for the mid-21st Century: Robotically Maintained Space Telescopes
The historical development of ground based astronomical telescopes leads us
to expect that space-based astronomical telescopes will need to be operational
for many decades. The exchange of scientific instruments in space will be a
prerequisite for the long lasting scientific success of such missions.
Operationally, the possibility to repair or replace key spacecraft components
in space will be mandatory. We argue that these requirements can be fulfilled
with robotic missions and see the development of the required engineering as
the main challenge. Ground based operations, scientifically and technically,
will require a low operational budget of the running costs. These can be
achieved through enhanced autonomy of the spacecraft and mission independent
concepts for the support of the software. This concept can be applied to areas
where the mirror capabilities do not constrain the lifetime of the mission.Comment: 4 pages, accepted in February 2012 for publication in A
A long hard look at the minimum state of PG 2112+059 with XMM-Newton
XMM-Newton successfully detected the minimum state of PG 2112+059 during a
short snapshot observation and performed a long follow-up observation. The high
signal-to-noise spectra are modelled assuming different emission scenarios and
compared with archival spectra taken by XMM-Newton and Chandra.
The PG 2112+059 X-ray spectra acquired in May 2007 allowed the detection of a
weak iron fluorescent line, which is interpreted as being caused by reflection
from neutral material at some distance from the primary X-ray emitting source.
The X-ray spectra of PG 2112+059 taken at five different epochs during
different flux states can be interpreted within two different scenarios. The
first consists of two layers of ionised material with column densities of N_H
~5 x 10^22 cm^-2 and N_H ~3.5 x 10^23 cm^-2, respectively. The first layer is
moderately ionised and its ionisation levels follow the flux changes, while the
other layer is highly ionised and does not show any correlation with the flux
of the source. The spectra can also be interpreted assuming reflection by an
ionised accretion disk seen behind a warm absorber. The warm absorber
ionisation is consistent with being correlated with the flux of the source,
which provides an additional degree of self-consistency with the overall
reflection-based model. We explain the spectral variability with light bending
according to the models of Miniutti and Fabian and constrain the black hole
spin to be a/M > 0.86. Both scenarios also assume that a distant cold reflector
is responsible for the Fe K \alpha emission line.
Light bending provides an attractive explanation of the different states of
PG 2112+059 and may also describe the physical cause of the observed properties
of other X-ray weak quasars.Comment: 15 pages, 12 figures, A&A latex, accepted for publication in
Astronomy & Astrophysic
The XMM-Newton view of PG quasars: II. Properties of the Fe K-alpha line
The properties of the fluorescence Fe K-alpha emission lines of a sample of
38 quasars (QSOs) observed with XMM-Newton are studied. These objects are
included in the optically selected sample from the Palomar-Green (PG) Bright
Quasar Survey with an X-ray luminosity 1.3E43<L(2-10 keV)<5.1E45 ergs/s and
z<1.72. For each object in the sample, we investigated the presence of both
narrow and broad iron lines in detail. A total of 20 out of the 38 QSOs show
evidence of an Fe K-alpha emission line with a narrow profile. The majority of
the lines are consistent with an origin in low ionization material, which is
likely to be located in the outer parts of the accretion disk, the molecular
torus, and/or the Broad Line Region. The average properties of the narrow Fe
K-alpha emission line observed in the sample are similar to those of Seyfert
type galaxies as inferred from recent XMM-Newton and Chandra studies. A broad
line has been significantly detected in only three objects. Furthermore, we
studied the relationship between the equivalent width (EW) of the iron line and
the hard band X-ray luminosity for radio quiet quasars. The analysis indicates
that no clear correlation between the strength of the line and the hard X-ray
luminosity is present, and our results do not show compelling evidence for an
anticorrelation between these two quantities, i.e. the so-called X-ray Baldwin
effect.Comment: 10 pages, 3 figures, accepted by A&
An X-ray Study of Local Infrared Bright Galaxies
We are carrying out detailed study of the X-ray and infrared (IR) properties
of a sample of local (d < 70 Mpc) luminous infrared galaxies (LIRGs) using
XMM-Newton and Spitzer (imaging and spectroscopy). The main goal is to study
the extreme processes of star formation and/or active galactic nuclei (AGN)
taking place in this cosmologically important class of galaxies. In this
proceedings we present the preliminary results obtained from the analysis of
the XMM-Newton X-ray images and the X-ray spectral modeling.Comment: 5 pages, to appear in Highlights of Spanish Astrophysics VI,
Proceedings of the IX Scientific Meeting of the Spanish Astronomical Society
held on September 13-17, 2010, in Madrid, Spai
X-ray high-resolution spectroscopy reveals feedback in a Seyfert galaxy from an ultra fast wind with complex ionization and velocity structure
Winds outflowing from Active Galactic Nuclei (AGNs) may carry significant
amount of mass and energy out to their host galaxies. In this paper we report
the detection of a sub-relativistic outflow observed in the Narrow Line Seyfert
1 Galaxy IRAS17020+4544 as a series of absorption lines corresponding to at
least 5 absorption components with an unprecedented wide range of associated
column densities and ionization levels and velocities in the range of
23,000-33,000 km/s, detected at X-ray high spectral resolution (E/Delta E
~1000) with the ESA's observatory XMM-Newton. The charge states of the material
constituting the wind clearly indicate a range of low to moderate ionization
states in the outflowing gas and column densities significantly lower than
observed in highly ionized ultra fast outflows. We estimate that at least one
of the outflow components may carry sufficient energy to substantially suppress
star formation, and heat the gas in the host galaxy. IRAS17020+4544 provides
therefore an interesting example of feedback by a moderately luminous AGN
hosted in a spiral galaxy, a case barely envisaged in most evolution models,
which often predict that feedback processes take place in massive elliptical
galaxies hosting luminous quasars in a post merger phase.Comment: 8 pages, 3 figures, to appear on ApJ Letter
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