144 research outputs found
The SSS phase of RS Ophiuchi observed with Chandra and XMM-Newton I.: Data and preliminary Modeling
The phase of Super-Soft-Source (SSS) emission of the sixth recorded outburst
of the recurrent nova RS Oph was observed twice with Chandra and once with
XMM-Newton. The observations were taken on days 39.7, 54.0, and 66.9 after
outburst. We confirm a 35-sec period on day 54.0 and found that it originates
from the SSS emission and not from the shock. We discus the bound-free
absorption by neutral elements in the line of sight, resonance absorption lines
plus self-absorbed emission line components, collisionally excited emission
lines from the shock, He-like intersystem lines, and spectral changes during an
episode of high-amplitude variability. We find a decrease of the oxygen K-shell
absorption edge that can be explained by photoionization of oxygen. The
absorption component has average velocities of -1286+-267 km/s on day 39.7 and
of -771+-65 km/s on day 66.9. The wavelengths of the emission line components
are consistent with their rest wavelengths as confirmed by measurements of
non-self absorbed He-like intersystem lines. We have evidence that these lines
originate from the shock rather than the outer layers of the outflow and may be
photoexcited in addition to collisional excitations. We found collisionally
excited emission lines that are fading at wavelengths shorter than 15A that
originate from the radiatively cooling shock. On day 39.5 we find a systematic
blue shift of -526+-114 km/s from these lines. We found anomalous He-like f/i
ratios which indicates either high densities or significant UV radiation near
the plasma where the emission lines are formed. During the phase of strong
variability the spectral hardness light curve overlies the total light curve
when shifted by 1000sec. This can be explained by photoionization of neutral
oxygen in the line of sight if the densities of order 10^{10}-10^{11} cm^{-3}.Comment: 16 pages, 10 figures, 4 tables. Accepted by ApJ; v2: Co-author
Woodward adde
Calibration and in orbit performance of the reflection grating spectrometer onboard XMM-Newton
Context: XMM-Newton was launched on 10 December 1999 and has been operational
since early 2000. One of the instruments onboard XMM-Newton is the reflection
grating spectrometer (RGS). Two identical RGS instruments are available, with
each RGS combining a reflection grating assembly (RGA) and a camera with CCDs
to record the spectra. Aims: We describe the calibration and in-orbit
performance of the RGS instrument. By combining the preflight calibration with
appropriate inflight calibration data including the changes in detector
performance over time, we aim at profound knowledge about the accuracy in the
calibration. This will be crucial for any correct scientific interpretation of
spectral features for a wide variety of objects. Methods: Ground calibrations
alone are not able to fully characterize the instrument. Dedicated inflight
measurements and constant monitoring are essential for a full understanding of
the instrument and the variations of the instrument response over time.
Physical models of the instrument are tuned to agree with calibration
measurements and are the basis from which the actual instrument response can be
interpolated over the full parameter space. Results: Uncertainties in the
instrument response have been reduced to < 10% for the effective area and < 6
mA for the wavelength scale (in the range from 8 A to 34 A. The remaining
systematic uncertainty in the detection of weak absorption features has been
estimated to be 1.5%. Conclusions: Based on a large set of inflight calibration
data and comparison with other instruments onboard XMM-Newton, the calibration
accuracy of the RGS instrument has been improved considerably over the
preflight calibrations.Comment: Accepted for publication in Astronomy and Astrophysics, Astronomical
instrumentation sectio
From X-ray dips to eclipse: Witnessing disk reformation in the recurrent nova USco
The 10th recorded outburst of the recurrent eclipsing nova USco was observed
simultaneously in X-ray, UV, and optical by XMM-Newton on days 22.9 and 34.9
after outburst. Two full passages of the companion in front of the nova ejecta
were observed, witnessing the reformation of the accretion disk. On day 22.9,
we observed smooth eclipses in UV and optical but deep dips in the X-ray light
curve which disappeared by day 34.9, then yielding clean eclipses in all bands.
X-ray dips can be caused by clumpy absorbing material that intersects the line
of sight while moving along highly elliptical trajectories. Cold material from
the companion could explain the absence of dips in UV and optical light. The
disappearance of X-ray dips before day 34.9 implies significant progress in the
formation of the disk. The X-ray spectra contain photospheric continuum
emission plus strong emission lines, but no clear absorption lines. Both
continuum and emission lines in the X-ray spectra indicate a temperature
increase from day 22.9 to day 34.9. We find clear evidence in the spectra and
light curves for Thompson scattering of the photospheric emission from the
white dwarf. Photospheric absorption lines can be smeared out during scattering
in a plasma of fast electrons. We also find spectral signatures of resonant
line scattering that lead to the observation of the strong emission lines.
Their dominance could be a general phenomenon in high-inclination systems such
as Cal87.Comment: Submitted to ApJ. 16 pages, 16 figure
A Spectroscopic Study of a Large Sample of Wolf-Rayet Galaxies
We analyze long-slit spectral observations of 39 Wolf-Rayet (WR) galaxies
with heavy element mass fraction ranging over 2 orders of magnitude, from
Zsun/50 to 2Zsun. Nearly all galaxies in our sample show broad WR emission in
the blue region of the spectrum (the blue bump) consisting of an unresolved
blend of N III 4640, C III 4650, C IV 4658 and He II 4686 emission lines. Broad
C IV 5808 emission (the red bump) is detected in 30 galaxies. Additionally,
weaker WR emission lines are identified, most often the N III 4512 and Si III
4565 lines, which have very rarely or never been seen and discussed before in
WR galaxies. These emission features are characteristic of WN7-WN8 and WN9-WN11
stars respectively.
We derive the numbers of early WC (WCE) and late WN (WNL) stars from the
luminosities of the red and blue bumps, and the number of O stars from the
luminosity of the Hbeta emission line. Additionally, we propose a new technique
for deriving the numbers of WNL stars from the N III 4512 and Si III 4565
emission lines. This technique is potentially more precise than the blue bump
method because it does not suffer from contamination of WCE and early WN (WNE)
stars and nebular gaseous emission.
The N(WR)/N(O+WR) ratio decreases with decreasing metallicity, in agreement
with predictions of evolutionary synthesis models. The N(WC)/N(WN) ratios and
the equivalent widths of the blue bump EW(4650) and of the red bump EW(5808)
derived from observations are also in satisfactory agreement with theoretical
predictions.Comment: 49 pages, 9 figures, to appear in Astrophys.
X-ray Pulsations from the region of the Supergiant Fast X-ray Transient IGR J17544-2619
Phase-targeted RXTE observations have allowed us to detect a transient 71.49
\pm 0.02 s signal that is most likely to be originating from the supergiant
fast X-ray transient IGR J17544-2619. The phase-folded light curve shows a
possible double-peaked structure with a pulsed flux of ~4.8*10^-12 erg cm^-2
s^-1 (3-10 keV). Assuming the signal to indicate the spin period of the neutron
star in the system, the provisional location of IGR J17544-2619 on the Corbet
diagram places the system within the classical wind-fed supergiant XRB region.
Such a result illustrates the growing trend of supergiant fast X-ray transients
to span across both of the original classes of HMXB in Porb - Pspin space.Comment: 7 pages, 6 figures, Accepted for publication in Astronomy and
Astrophysics main journa
Planck Intermediate Results. IV. The XMM-Newton validation programme for new Planck galaxy clusters
We present the final results from the XMM-Newton validation follow-up of new
Planck galaxy cluster candidates. We observed 15 new candidates, detected with
signal-to-noise ratios between 4.0 and 6.1 in the 15.5-month nominal Planck
survey. The candidates were selected using ancillary data flags derived from
the ROSAT All Sky Survey (RASS) and Digitized Sky Survey all-sky maps, with the
aim of pushing into the low SZ flux, high-z regime and testing RASS flags as
indicators of candidate reliability. 14 new clusters were detected by XMM,
including 2 double systems. Redshifts lie in the range 0.2 to 0.9, with 6
clusters at z>0.5. Estimated M500 range from 2.5 10^14 to 8 10^14 Msun. We
discuss our results in the context of the full XMM validation programme, in
which 51 new clusters have been detected. This includes 4 double and 2 triple
systems, some of which are chance projections on the sky of clusters at
different z. We find that association with a RASS-BSC source is a robust
indicator of the reliability of a candidate, whereas association with a FSC
source does not guarantee that the SZ candidate is a bona fide cluster.
Nevertheless, most Planck clusters appear in RASS maps, with a significance
greater than 2 sigma being a good indication that the candidate is a real
cluster. The full sample gives a Planck sensitivity threshold of Y500 ~ 4 10^-4
arcmin^2, with indication for Malmquist bias in the YX-Y500 relation below this
level. The corresponding mass threshold depends on z. Systems with M500 > 5
10^14 Msun at z > 0.5 are easily detectable with Planck. The newly-detected
clusters follow the YX-Y500 relation derived from X-ray selected samples.
Compared to X-ray selected clusters, the new SZ clusters have a lower X-ray
luminosity on average for their mass. There is no indication of departure from
standard self-similar evolution in the X-ray versus SZ scaling properties.
(abridged)Comment: accepted by A&
Credit bureaus between risk-management, creditworthiness assessment and prudential supervision
"This text may be downloaded for personal research purposes only. Any additional reproduction for other purposes, whether in hard copy or electronically, requires the consent of the author. If cited or quoted, reference should be made to the full name of the author, the title, the working paper or other series, the year, and the publisher."This paper discusses the role and operations of consumer Credit Bureaus in the European Union in the context of the economic theories, policies and law within which they work. Across Europe there is no common practice of sharing the credit data of consumers which can be used for several purposes. Mostly, they are used by the lending industry as a practice of creditworthiness assessment or as a risk-management tool to underwrite borrowing decisions or price risk. However, the type, breath, and depth of information differ greatly from country to country. In some Member States, consumer data are part of a broader information centralisation system for the prudential supervision of banks and the financial system as a whole. Despite EU rules on credit to consumers for the creation of the internal market, the underlying consumer data infrastructure remains fragmented at national level, failing to achieve univocal, common, or defined policy objectives under a harmonised legal framework. Likewise, the establishment of the Banking Union and the prudential supervision of the Euro area demand standardisation and convergence of the data used to measure debt levels, arrears, and delinquencies. The many functions and usages of credit data suggest that the policy goals to be achieved should inform the legal and institutional framework of Credit Bureaus, as well as the design and use of the databases. This is also because fundamental rights and consumer protection concerns arise from the sharing of credit data and their expanding use
Inflows and Outflows in the Dwarf Starburst Galaxy NGC 5253: High-Resolution HI Observations
VLA and Parkes 64 m radiotelescope 21-cm observations of the starburst dwarf
galaxy NGC 5253 reveal a multi-component non-axisymmetric HI distribution. The
component associated with the stellar body shows evidence for a small amount of
rotational support aligned with the major axis, in agreement with optically
measured kinematics and consistent with the small galaxian mass. Approximately
20-30% of the HI emission is associated with a second component, an HI "plume"
extending along the optical minor axis to the southeast. We consider outflow,
inflow, and tidal origins for this feature. Outflow appears improbable, inflow
is a possibility, and tidal debris is most consistent with the observations.
These observations also reveal a filamentary third component that includes an
800 pc diameter HI shell or bubble to the west of the nucleus, coinciding with
an Halpha shell. The mass of HI in the shell may be as large as ~4x10^6 Msun.
This large mass, coupled with the lack of expansion signatures in the neutral
and ionized gas (v<30 km/s), suggests that this feature may be an example of a
starburst-blown bubble stalled by interaction with a massive neutral envelope.
Many other HI kinematic features closely resemble those seen in Halpha emission
from the ionized gas, supporting the interpretation of neutral and ionized gas
outflow at velocities of ~30 km/s. Comparison between extinction estimates from
the Balmer emission-line decrement and the HI column densities suggest a
gas-to-dust ratio 2-3 times the Galactic value in this low-metallicity (Z=1/4
Zsun) galaxy.Comment: 36 pages, 12 figures; Accepted for Publication in the Astronomical
Journal ; a postscript version with high resolution figures can be found at
http://physics.uwyo.edu/~chip/Papers
The HarveyâBradshaw Index adapted to a mobile application compared with In-clinic assessment: the MediCrohn Study
[Abstract]
Objectives: Mobile apps are useful tools in e-health and self-management strategies in disease monitoring. We evaluated the HarveyâBradshaw index (HBI) mobile app self-administered by the patient to see if its results agreed with HBI in-clinic assessed by a physician.
Methods: Patients were enrolled in a 4-month prospective study with clinical assessments at months 1 and 4. Patients completed mobile app HBI and within 48âh, HBI was performed by a physician (gold standard). HBI scores characterized Crohn's disease (CD) as remission <5 or active â„5. We determined agreement per item and total HBI score and intraclass correlation coefficients (ICCs). BlandâAltman plot was performed. HBI changes in disease activity from month 1 to month 4 were determined.
Results: A total of 219 patients were enrolled. All scheduled assessments (385 pairs of the HBI questionnaire) showed a high percentage of agreement for remission/activity (92.4%, Îșâ=â0.796), positive predictive value (PPV) for remission of 98.2%, and negative predictive value of 76.7%. High agreement was also found at month 1 (93.15%, Îșâ=â0.82) and month 4 (91.5%, Îșâ=â0.75). BlandâAltman plot was more uniform when the HBI mean values were <5 (remission). ICC values were 0.82, 0.897, and 0.879 in all scheduled assessments, 1 and 4 months, respectively.
Conclusions: We found a high percentage of agreement between patients' self-administered mobile app HBI and in-clinic physician assessment to detect CD activity with a remarkably high PPV for remission. The mobile app HBI might allow a strict control of inflammation by remote monitoring and flexible follow-up of CD patients. Reduction of sanitary costs could be possible
New constraints on protostellar jet collimation from high-density gas UV tracers
The analysis of high-resolution profiles of the semiforbidden UV lines of C III](1908) and Si III](1892) in the spectra of T Tauri stars (TTSs) shows the following : (1) There is C III](1908) and Si III](1892) emission at velocities that are similar to those observed in the optical forbidden lines formed in the TTSs jets. The luminosity of the UV lines is comparable to that of the optical lines. (2) The comparison between the optical and UV light curves indicates that the C III](1908) and Si III](1892) emission of RY Tau is not associated with accretion shocks, but it is produced farther than 2 R-* from the star. (3) The profiles of the UV semiforbidden lines are significantly broader than those of the optical forbidden lines. These profiles cannot be produced in a narrow collimated beam, and they are most likely produced in a bow-shaped shock wave formed at the base of the optical jet, where the hot gas emits in a broad range of projected radial velocities. (4) The atmosphere of RU Lup contributes significantly to the Si III](1892) emission. (5) A puzzling narrow feature is observed close to the C III](1908) line. The feature is blueshifted by -260 km s(-1), which corresponds to the wind terminal velocity measured in the P Cygni profile of the Mg II (UV1) lines. Moreover, constraints are derived on the characteristics of the C III](1908) and Si III](1892) emitting region in RY Tau. It is shown that 4.7 less than or equal to log T-e less than or equal to 5.0 and 10(9) cm(-3) less than or equal to N-e less than or equal to 10(11) cm(-3) provided that the emission is produced in a collisional plasma and that the 1665 Angstrom feature observed in low-dispersion International Ultraviolet Explorer (IUE) spectra is confirmed to be O III](1665) emission produced in the wind. These very high densities are difficult to generate in the shocks produced by the magnetic pinching of centrifugally driven magnetized disk winds. The data also suggest that the shocked layer has a radius of some few stellar radii and it is closer than similar to 38 R-* to the star
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