385 research outputs found
XMM-Newton Slew Survey observations of the gravitational wave event GW150914
The detection of the first gravitational wave (GW) transient GW150914
prompted an extensive campaign of follow-up observations at all wavelengths.
Although no dedicated XMM-Newton observations have been performed, the
satellite passed through the GW150914 error box during normal operations. Here
we report the analysis of the data taken during these satellite slews performed
two hours and two weeks after the GW event. Our data cover 1.1 square degrees
and 4.8 square degrees of the final GW localization region. No credible X-ray
counterpart to GW150914 is found down to a sensitivity of 6E-13 erg/cm2/s in
the 0.2-2 keV band. Nevertheless, these observations show the great potential
of XMM-Newton slew observations for the search of the electromagnetic
counterparts of GW events. A series of adjacent slews performed in response to
a GW trigger would take <1.5 days to cover most of the typical GW credible
region. We discuss this scenario and its prospects for detecting the X-ray
counterpart of future GW detections.Comment: 6 pages, 3 figures, 2 tables. Accepted for publication in ApJ Letter
Improvement of the Rotation Arch of the Posterior Interosseous Pedicle Flap Preserving Both Reverse Posterior and Anterior Interosseous Vascular Sources.
Abstract
PURPOSE:
The reverse posterior interosseous artery flap has several advantages, not sacrificing any major blood vessel, but its relatively short pedicle limits the use to cover defects up to the metacarpophalangeal joint. Our purpose is to demonstrate that the ligature of the anterior interosseous artery (AIA), proximal to the communicating branch with the posterior interosseous artery, leads to an improved flap rotation arch, preserving both vascular sources.
METHODS:
Sixteen fresh cadavers with latex perfusion were analyzed before and after our technique of elongation, and the so-obtained measures were standardized in "percentage of elongation of the pedicle." Eight patient with the loss of substance at the dorsal aspect of the hand have been treated with this technique, and results were evaluated in terms of flap survival and complication rates.
RESULTS:
The medium length of the pedicle in the normal flap was 10.8\u2009cm, and after the section of the AIA, the medium length of the pedicle was 13.6\u2009cm with a medium increase of 2.8\u2009cm. It means a medium increase of 24% of the length of the pedicle. In all patients treated, full coverage of the defect was obtained, and we did not experience major complications.
CONCLUSIONS:
This anatomical study supported by our clinical experience demonstrates that the use of the variant described above permits to reach more distal part of the hand without being afraid to stretch the pedicle because of the connection with the anastomotic arcades of the AIA at the wrist reducing the risk of ischemia of the flap
The anomalous X-ray pulsar 1E 1048.1-5937: Phase resolved spectroscopy with the XMM-Newton satellite
We report on an observation of the Anomalous X-ray Pulsar 1E 1048.1-5937
performed with the XMM-Newton satellite. The phase averaged spectrum of 1E
1048.1-5937 is well described by the sum of a power law with photon index ~2.9
and a blackbody with temperature ~0.6 keV, without evidence for significant
absorption or emission lines. The above spectral parameters do not vary during
the phases corresponding to the broad pulse, while the off pulse emission shows
a different spectrum characterized by a soft excess at energies below ~1.5 keV.
The XMM-Newton observation and a re-analysis of archival BeppoSAX data, show
that the spectral parameters and flux of 1E 1048.1-5937 did not change
significantly during observations spanning the last four years. All the data
are consistent with a 2-10 keV luminosity varying in the range ~(5-7) 10^33
erg/s (for a distance of 3 kpc).Comment: 7 pages, 5 figures, accepted for publication in A&
Behind the dust curtain: the spectacular case of GRB 160623A
We report on the X-ray dust-scattering features observed around the afterglow
of the gamma ray burst GRB 160623A. With an XMM-Newton observation carried out
~2 days after the burst, we found evidence of at least six rings, with angular
size expanding between ~2 and 9 arcmin, as expected for X-ray scattering of the
prompt GRB emission by dust clouds in our Galaxy. From the expansion rate of
the rings, we measured the distances of the dust layers with extraordinary
precision: 528.1 +\- 1.2 pc, 679.2 +\- 1.9 pc, 789.0 +\- 2.8 pc, 952 +\- 5 pc,
1539 +\- 20 pc and 5079 +\- 64 pc. A spectral analysis of the ring spectra,
based on an appropriate dust-scattering model (BARE-GR-B from Zubko et al.
2004}) and the estimated burst fluence, allowed us to derive the column density
of the individual dust layers, which are in the range 7x10^20-1.5x10^22 cm^-2.
The farthest dust-layer (i.e. the one responsible for the smallest ring) is
also the one with the lowest column density and it is possibly very extended,
indicating a diffuse dust region. The properties derived for the six
dust-layers (distance, thickness, and optical depth) are generally in good
agreement with independent information on the reddening along this line of
sight and on the distribution of molecular and atomic gas.Comment: 9 pages, 10 figures, 1 table; accepted for publication in MNRA
Giant outburst from the supergiant fast X-ray transient IGR J17544-2619: accretion from a transient disc?
Supergiant fast X-ray transients (SFXTs) are high mass X-ray binaries
associated with OB supergiant companions and characterised by an X-ray flaring
behaviour whose dynamical range reaches 5 orders of magnitude on timescales of
a few hundred to thousands of seconds. Current investigations concentrate on
finding possible mechanisms to inhibit accretion in SFXTs and explain their
unusually low average X-ray luminosity. We present the Swift observations of an
exceptionally bright outburst displayed by the SFXT IGR J17544-2619 on 2014
October 10 when the source achieved a peak luminosity of erg
s. This extends the total source dynamic range to 10, the
largest (by a factor of 10) recorded so far from an SFXT. Tentative evidence
for pulsations at a period of 11.6 s is also reported. We show that these
observations challenge, for the first time, the maximum theoretical luminosity
achievable by an SFXT and propose that this giant outburst was due to the
formation of a transient accretion disc around the compact object.Comment: Accepted for publication in Astronomy and Astrophysics Letters. 5
pages, 5 figures, 2 table
Long Term Study of the Double Pulsar J0737-3039 with XMM-Newton: pulsar timing
The relativistic double neutron star binary PSR J0737-3039 shows clear
evidence of orbital phase-dependent wind-companion interaction, both in radio
and X-rays. In this paper we present the results of timing analysis of PSR
J0737-3039 performed during 2006 and 2011 XMM-Newton Large Programs that
collected ~20,000 X-ray counts from the system. We detected pulsations from PSR
J0737-3039A (PSR A) through the most accurate timing measurement obtained by
XMM-Newton so far, the spin period error being of 2x10^-13 s. PSR A's pulse
profile in X-rays is very stable despite significant relativistic spin
precession that occurred within the time span of observations. This yields a
constraint on the misalignment between the spin axis and the orbital momentum
axis Delta_A ~6.6^{+1.3}_{-5.4} deg, consistent with estimates based on radio
data. We confirmed pulsed emission from PSR J0737-3039B (PSR B) in X-rays even
after its disappearance in radio. The unusual phenomenology of PSR B's X-ray
emission includes orbital pulsed flux and profile variations as well as a loss
of pulsar phase coherence on time scales of years. We hypothesize that this is
due to the interaction of PSR A's wind with PSR B's magnetosphere and
orbital-dependent penetration of the wind plasma onto PSR B closed field lines.
Finally, the analysis of the full XMM-Newton dataset provided evidences of
orbital flux variability (~7%) for the first time, involving a bow-shock
scenario between PSR A's wind and PSR B's magnetosphere.Comment: Comments: 16 Pages, 6 Figures. Accepted for publication in
Astrophysical Journal (Draft Version
The X-ray afterglow of GRB030329 at early and late times
Thanks to its extraordinary brightness, the X-ray afterglow of GRB030329
could be studied by XMM-Newton up to two months after the prompt Gamma-ray
emission.
We present the results of two XMM-Newton observations performed on May 5 and
29, as well as an analysis of the Rossi-XTE data of the early part of the
afterglow, discussing in particular the stability of the X-ray spectrum and
presenting upper limits on the presence of X-ray emission lines.Comment: 4 pages, 2 figures, to appear in the Santa Fe GRB Conference
Proceedings, 200
Unveiling the nature of RX J0002+6246 with XMM-Newton
The X-ray source RX J0002+6246 was discovered close to the supernova remnant
CTB1 in a ROSAT observation performed in 1992. The source phenomenology (soft
spectrum, apparent lack of counterparts, possible pulsations at 242 ms, hints
for surrounding diffuse emission) led to interpret it as an isolated neutron
star in a new supernova remnant. We have analysed an archival XMM-Newton
observation performed in 2001. The source coordinates, as computed on the
XMM-Newton images, coincide with those of a bright source listed in optical and
infrared catalogues. The X-ray spectrum is well described by an optically thin
plasma model. No fast pulsations are seen, nor clear evidence of a supernova
remnant associated to the source. Thus, we conclude that RX J0002+6246 is not
an isolated neutron star, but the X-ray counterpart of the bright
optical/infrared source, most likely a F7 spectral class star located at about
0.2 kpc.Comment: 5 pages, 2 figures and 1 table. Accepted for publication in Monthly
Notices of the Royal Astronomical Society Main Journa
XMM-Newton Spectroscopy of the Accretion-Driven Millisecond X-ray Pulsar XTE J1751-305 in Outburst
We present an analysis of the first high-resolution spectra measured from an
accretion-driven millisecond X-ray pulsar in outburst. We observed XTE
J1751-305 with XMM-Newton on 2002 April 7 for approximately 35 ksec. Using a
simple absorbed blackbody plus power-law model, we measure an unabsorbed flux
of (6.6 +/- 0.1) * 10^(-10) erg/cm^2/s (0.5--10.0 keV). A hard power-law
component (Gamma = 1.44 +/- 0.01) contributes 83% of the unabsorbed flux in the
0.5-10.0 keV band, but a blackbody component (kT = 1.05 +/- 0.01 keV) is
required. We find no clear evidence for narrow or broad emission or absorption
lines in the time-averaged spectra, and the sensitivity of this observation has
allowed us to set constraining upper-limits on the strength of important
features. The lack of line features is at odds with spectra measured from some
other X-ray binaries which share some similarities with XTE J1751-305. We
discuss the implications of these findings on the accretion flow geometry in
XTE J1751-305.Comment: 5 pages, 3 figures (2 color). ApJ Letters, accepted. Uses
emulateapj.st
Chandra Observations of 1RXS J141256.0+792204 (Calvera)
We report the results of a 30 ks Chandra ACIS-S observation of the isolated
compact object 1RXS J141256.0+792204 (Calvera). The X-ray spectrum is
adequately described by an absorbed neutron star hydrogen atmosphere model with
an effective temperature at infinity of 88.3 +/- 0.8 eV and radiation radius at
infinity of 4.1 +/- 0.1 km/kpc. The best-fit blackbody spectrum yields
parameters consistent with previous measurements; although the fit itself is
not statistically acceptable, systematic uncertainties in the pile-up
correction may contribute to this. We find marginal evidence for narrow
spectral features in the X-ray spectrum between 0.3 and 1.0 keV. In one
interpretation, we find evidence at 81%-confidence for an absorption edge at
0.64 (+0.08) (-0.06) keV with an equivalent width of ~70 eV; if this feature is
real, it is reminiscent of features seen in the isolated neutron stars RX
J1605.3+3249, RX J0720.4-3125, and 1RXS J130848.6+212708 (RBS 1223). In an
alternative approach, we find evidence at 88%-confidence for an unresolved
emission line at energy 0.53 +/- 0.02 keV, with an equivalent width of ~28 eV;
the interpretation of this feature, if real, is uncertain. We search for
coherent pulsations up to the Nyquist frequency of 1.13 Hz and set an upper
limit of 8.0% rms on the strength of any such modulation. We derive an improved
position for the source and set the most rigorous limits to-date on any
associated extended emission on arcsecond scales. Our analysis confirms the
basic picture of Calvera as the first isolated compact object in the
ROSAT/Bright Source Catalog discovered in six years, the hottest such object
known, and an intriguing target for multiwavelength study.Comment: Submitted to ApJ. AASTeX, 19 pages, 2 figure
- …