90 research outputs found
First Results from the XMM-Newton Slew Survey
We have attempted to analyse all the available data taken by XMM-Newton as it
slews between targets. This slew survey, the resultant source catalogue and the
analysis procedures used are described in an accompanying paper. In this letter
we present the initial science results from the survey. To date, detailed
source-searching has been performed in three X-ray bands (soft, hard and total)
in the EPIC-pn 0.2-12 keV band over ~6300 sq.degrees (~15% of the sky), and of
order 4000 X-ray sources have been detected (~55% of which have IDs). A great
variety of sources are seen, including AGN, galaxies, clusters and groups,
active stars, SNRs, low- and high-mass XRBs and white dwarfs. In particular, as
this survey constitutes the deepest ever hard-band 2-12 keV all-sky survey, a
large number of hard sources are detected. Furthermore, the great sensitivity
and low-background of the EPIC-pn camera are especially suited to emission from
extended sources, and interesting spatial structure is observed in many
supernova remnants and clusters of galaxies. The instrument is very adept at
mapping large areas of the X-ray sky. Also, as the slew survey is well matched
to the ROSAT all-sky survey, long-term variability studies are possible, and a
number of extremely variable X-ray sources, some possibly due to the tidal
disruption of stars by central supermassive black holes, have been discovered.Comment: 4 Pages, 3 Figs, to appear in PASJ (2006) 58, No 6. Colour version
available at http://www.star.le.ac.uk/~amr30/publications.htm
SRG/eROSITA X-ray shadowing study of giant molecular clouds
SRG/eROSITA is situated in a halo orbit around L2 where the highly variable
solar wind charge exchange (SWCX) emission from Earth's magnetosheath is
expected to be negligible. The soft X-ray foreground emissions from the local
hot bubble (LHB) and the remaining heliospheric SWCX emissions could be studied
in unprecedented detail with eROSITA All-Sky Survey (eRASS) data in a 6-month
cadence and better spectral resolution than ROSAT. We aim to use eRASS data of
the sight lines towards three giant molecular clouds away from the Galactic
plane to isolate and study the soft X-ray diffuse foreground emission. These
X-ray shadows will serve as calibration baselines for the future
three-dimensional structural study of the LHB. We conducted spectral analysis
on the diffuse X-ray spectra of these clouds from the first four eRASSs to
estimate and separate the heliospheric SWCX contribution from the LHB emission.
We find the density of the LHB to be independent of the sight line with cm, but not the temperature. We report a lower
temperature of keV towards ChamaeleonII &
III (ChaII & III) than Ophiuchus (Oph) and Corona Australis (CrA), in which
we measured and keV, respectively. We measured
the emission measure of the LHB to be cmpc at
medium Galactic latitudes (). A monotonic increase in the
SWCX contribution has been observed since the start of 2020, coincidental with
the beginning of solar cycle 25. For Oph, SWCX has dominated the LHB in the
-keV band intensity since eRASS2. We observed lower SWCX
contributions in ChaII & III and CrA, consistent with the expected
decreasing solar wind ion density at high heliographic latitudes.Comment: 22 pages, 15 figures. Accepted for publication in A&
SRG/eROSITA and XMM-Newton observations of Vela Jr
The Vela supernova remnant complex is a region containing at least three
supernova remnants: Vela, Puppis A, and Vela Jr. With the launch of the
spectro-imaging X-ray telescope eROSITA on board the Spectrum Roentgen Gamma
(SRG) mission, it became possible to observe the one degree wide Vela Jr in its
entirety. Although several previous pointed Chandra and XMM-Newton observations
are available, it is only the second time after the ROSAT all-sky survey that
the whole remnant was observed in X-rays with homogeneous sensitivity. Vela Jr
is one of the few remnants emitting in the TeV band, making it an important
object in shock acceleration studies. However, the age and distance
determination using X-ray emission is largely hampered by the presence of the
Vela SNR along the same line. With the eROSITA data set our aim is to
characterize the emission of Vela Jr and distinguish it from Vela emission, and
also to characterize the spectral emission of the inner remnant. We processed
the eROSITA data dividing the whole remnant into seven different regions. In
addition, images of the whole remnant were employed to pinpoint the position of
the geometric center and constrain the proper motion of the CCO. We also
employed archival XMM-Newton pointed observations of the NW rim to determine
the cutoff energy of the electrons and the expansion velocity. We find the
magnetic field can vary between 2 G and 16 G in the NW rim. We also
find that the remnant spectrum is uniformly featureless in most regions, except
for two inner regions where an extra thermal model component improves the fit.
We obtain new coordinates for the geometric remnant center, resulting in a
separation of only 35.2 15.8" from the position of the CCO. As a result,
we reinforce the association between the CCO and a proposed faint optical/IR
counterpart.Comment: Accepted for publication in A&
Source Matching in the SDSS and RASS: Which Galaxies are Really X-ray Sources?
The current view of galaxy formation holds that all massive galaxies harbor a
massive black hole at their center, but that these black holes are not always
in an actively accreting phase. X-ray emission is often used to identify
accreting sources, but for galaxies that are not harboring quasars
(low-luminosity active galaxies), the X-ray flux may be weak, or obscured by
dust. To aid in the understanding of weakly accreting black holes in the local
universe, a large sample of galaxies with X-ray detections is needed. We
cross-match the ROSAT All Sky Survey (RASS) with galaxies from the Sloan
Digital Sky Survey Data Release 4 (SDSS DR4) to create such a sample. Because
of the high SDSS source density and large RASS positional errors, the
cross-matched catalog is highly contaminated by random associations. We
investigate the overlap of these surveys and provide a statistical test of the
validity of RASS-SDSS galaxy cross-matches. SDSS quasars provide a test of our
cross-match validation scheme, as they have a very high fraction of true RASS
matches. We find that the number of true matches between the SDSS main galaxy
sample and the RASS is highly dependent on the optical spectral classification
of the galaxy; essentially no star-forming galaxies are detected, while more
than 0.6% of narrow-line Seyferts are detected in the RASS. Also, galaxies with
ambiguous optical classification have a surprisingly high RASS detection
fraction. This allows us to further constrain the SEDs of low-luminosity active
galaxies. Our technique is quite general, and can be applied to any
cross-matching between surveys with well-understood positional errors.Comment: 10 pages, 10 figures, submitted to The Astronomical Journal on 19
June 200
Improving XMM-Newton EPIC pn data at low energies: method and application to the Vela SNR
High quantum efficiency over a broad spectral range is one of the main
properties of the EPIC pn camera on-board XMM-Newton. The quantum efficiency
rises from ~75% at 0.2 keV to ~100% at 1 keV, stays close to 100% until 8 keV,
and is still ~90% at 10 keV. The EPIC pn camera is attached to an X-ray
telescope which has the highest collecting area currently available, in
particular at low energies (more than 1400 cm2 between 0.1 and 2.0 keV). Thus,
this instrument is very sensitive to the low-energy X-ray emission. However,
X-ray data at energies below ~0.2 keV are considerably affected by detector
effects, which become more and more important towards the lowest transmitted
energies. In addition to that, pixels which have received incorrect offsets
during the calculation of the offset map at the beginning of each observation,
show up as bright patches in low-energy images. Here we describe a method which
is not only capable of suppressing the contaminations found at low energies,
but which also improves the data quality throughout the whole EPIC pn spectral
range. This method is then applied to data from the Vela supernova remnant.Comment: Proc. SPIE Vol. 5488: Astronomical Telescopes and Instrumentation, UV
- Gamma-Ray Space Telescope Systems, Eds. Guenther Hasinger and Martin J.
Turner, 22-24 June 2004, Glasgow, Scotland United Kingdo
Characterization of the Particle-induced Background of XMM-Newton EPIC-pn: Short- and Long-term Variability
The particle-induced background of X-ray observatories is produced by galactic cosmic ray (GCR) primary protons, electrons, and He ions. Events due to direct interaction with the detector are usually removed by onboard processing. The interactions of these primary particles with the detector environment produce secondary particles that mimic X-ray events from celestial sources, and are much more difficult to identify. The filter-wheel closed data from the XMM-Newton EPIC-pn camera in small window mode (SWM) contains both the X-ray-like background events, and the events due to direct interactions with the primary particles. From this data, we demonstrate that X-ray-like background events are spatially correlated with the primary particle interaction. This result can be used to further characterize and reduce the non-X-ray background in silicon-based X-ray detectors in current and future missions. We also show that spectrum and pattern fractions of secondary particle events are different from those produced by cosmic X-rays
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