909 research outputs found
Evolution of the disc atmosphere in the X-ray binary MXB 1659-298, during its 2015-2017 outburst
We report on the evolution of the X-ray emission of the accreting neutron
star (NS) low mass X-ray binary (LMXB), MXB 1659-298, during its most recent
outburst in 2015-2017. We detected 60 absorption lines during the soft state
(of which 21 at more than 3 ), that disappeared in the hard state
(e.g., the Fe xxv and Fe xxvi lines). The absorbing plasma is at rest, likely
part of the accretion disc atmosphere. The bulk of the absorption features can
be reproduced by a high column density () of highly
ionised () plasma. Its disappearance during the
hard state is likely the consequence of a thermal photo-ionisation instability.
MXB 1659-298's continuum emission can be described by the sum of an absorbed
disk black body and its Comptonised emission, plus a black body component. The
observed spectral evolution with state is in line with that typically observed
in atoll and stellar mass black hole LMXB. The presence of a relativistic Fe
K disk-line is required during the soft state. We also tentatively
detect the Fe xxii doublet, whose ratio suggests an electron density of the
absorber of , hence, the absorber is likely located at
from the illuminating source, well inside the Compton and
outer disc radii. MXB 1659-298 is the third well monitored atoll LMXB
showcasing intense Fe xxv and Fe xxvi absorption during the soft state that
disappears during the hard state.Comment: MNRAS in pres
Multiwavelength campaign on Mrk 509. XIII. Testing ionized-reflection models on Mrk 509
Active Galactic Nuclei (AGN) are the most luminous persistent objects in the
universe. An excess of X-ray emission below about 2 keV, called soft-excess, is
very common in Type 1 AGN spectra. The origin of this feature remains debated.
Originally modeled with a blackbody, there are now several possibilities to
model the soft-excess, including warm Comptonization and blurred ionized
reflection. In this paper, we test ionized-reflection models on Mrk 509, a
bright Seyfert 1 galaxy for which we have a unique data set, in order to
determine whether it can be responsible for the strong soft-excess. We use ten
simultaneous XMM-Newton and INTEGRAL observations performed every four days. We
present here the results of the spectral analysis, the evolution of the
parameters and the variability properties of the X-ray emission. The
application of blurred ionized-reflection models leads to a very strong
reflection and an extreme geometry, but fails to reproduce the broad-band
spectrum of Mrk 509. Two different scenarios for blurred ionized reflection are
discussed: stable geometry and lamp-post configuration. In both cases we find
that the model parameters do not follow the expected relations, indicating that
the model is fine-tuned to fit the data without physical justification. A
large, slow variation of the soft-excess without counterpart in the hard X-rays
could be explained by a change in ionization of the reflector. However, such a
change does not naturally follow from the assumed geometrical configuration.
Warm Comptonization remains the most probable origin of the soft-excess in this
object. Nevertheless, it is possible that both ionized reflection and warm
Comptonization mechanisms can explain the soft-excess in all objects, one
dominating the other one, depending on the physical conditions of the disk and
the corona.Comment: 12 pages, A&A accepte
Multiwavelength campaign on Mrk 509 XIV. Chandra HETGS spectra
We present in this paper the results of a 270 ks Chandra HETGS observation in
the context of a large multiwavelength campaign on the Seyfert galaxy Mrk 509.
The HETGS spectrum allows us to study the high ionisation warm absorber and the
Fe-K complex in Mrk 509. We search for variability in the spectral properties
of the source with respect to previous observations in this campaign, as well
as for evidence of ultra-fast outflow signatures. The Chandra HETGS X-ray
spectrum of Mrk 509 was analysed using the SPEX fitting package. We confirm the
basic structure of the warm absorber found in the 600 ks XMM-Newton RGS
observation observed three years earlier, consisting of five distinct
ionisation components in a multikinematic regime. We find little or no
variability in the physical properties of the different warm absorber phases
with respect to previous observations in this campaign, except for component D2
which has a higher column density at the expense of component C2 at the same
outflow velocity (-240 km/s). Contrary to prior reports we find no -700 km/s
outflow component. The O VIII absorption line profiles show an average covering
factor of 0.81 +/- 0.08 for outflow velocities faster than -100 km/s, similar
to those measured in the UV. This supports the idea of a patchy wind. The
relative metal abundances in the outflow are close to proto-solar. The narrow
component of the Fe Kalpha emission line shows no changes with respect to
previous observations which confirms its origin in distant matter. The narrow
line has a red wing that can be interpreted to be a weak relativistic emission
line. We find no significant evidence of ultra-fast outflows in our new
spectrum down to the sensitivity limit of our data.Comment: 12 pages, 9 figures, accepted for publication in Astronomy &
Astrophysic
Prospective randomized comparison of laparoscopic versus open adrenalectomy for sporadic pheochromocytoma.
BACKGROUND: Laparoscopic adrenalectomy for pheochromocytoma remains subject of
debate, owing to the systemic consequences of pneumoperitoneum in patients with
catecholamine-secreting tumors.
METHODS: A prospective randomized study was conducted (2000-2006), evaluating
cardiovascular instability during open (n = 9, group A) or laparoscopic (n = 13,
group B) adrenalectomy for pheochromocytoma. Haemodynamic parameters were
recorded by invasive monitoring.
RESULTS: Haemodynamic instability was observed in 3/9 (group A) and 6/13 patients
(group B), with a mean of 1.8 and 2.2 hypertensive peaks per patient (p = n.s.).
Blood loss (164 +/- 94 cc versus 48 +/- 36 cc, p < 0.05) and operative time (180
+/- 40 versus 158 +/- 45 min, p = n.s.) favored laparoscopic procedures.
Postoperative morbidity and mortality were nil. Hospital stay was shorter in
group B (p < 0.05). Long-term follow-up was always normal.
CONCLUSIONS: Laparoscopic approach for pheochromocytoma can be as safe as open
surgery; intraoperative haemodynamic instability, although usually controlled
with success, remains a source of concern
NuSTAR + XMM-Newton monitoring of the neutron star transient AX J1745.6-2901
AX J1745.6-2901 is a high-inclination (eclipsing) transient neutron star (NS)
Low Mass X-ray Binary (LMXB) showcasing intense ionised Fe K absorption. We
present here the analysis of 11 XMM-Newton and 15 NuSTAR new data-sets
(obtained between 2013-2016), therefore tripling the number of observations of
AX J1745.6-2901 in outburst. Thanks to simultaneous XMM-Newton and NuSTAR
spectra, we greatly improve on the fitting of the X-ray continuum. During the
soft state the emission can be described by a disk black body (
keV and inner disc radius km), plus hot ( keV)
black body radiation with a small emitting radius ( km)
likely associated with the boundary layer or NS surface, plus a faint
Comptonisation component. Imprinted on the spectra are clear absorption
features created by both neutral and ionised matter. Additionally, positive
residuals suggestive of an emission Fe K disc line and consistent with
relativistic ionised reflection are present during the soft state, while such
residuals are not significant during the hard state. The hard state spectra are
characterised by a hard () power law, showing no evidence
for a high energy cut off ( keV) and implying a small optical
depth (). The new observations confirm the previously witnessed trend
of exhibiting strong Fe K absorption in the soft state, that significantly
weakens during the hard state. Optical (GROND) and radio (GMRT) observations
suggest for AX J1745.6-2901 a standard broad band SED as typically observed in
accreting neutron stars.Comment: Accepted for publication in MNRA
PG 1211+143: probing high frequency lags in a high mass AGN
We present the timing analysis of the four archived XMM-Newton observations
of PG 1211+143. The source is well-known for its spectral complexity,
comprising a strong soft-excess and different absorption systems. Soft energy
band (0.3-0.7 keV) lags are detected over all the four observations, in the
frequency range \nu \lsim 6 \times 10^{-4} Hz, where hard lags, similar to
those observed in black hole X-ray binaries, are usually detected in smaller
mass AGN. The lag magnitude is energy-dependent, showing two distinct trends
apparently connectable to the two flux levels at which the source is observed.
The results are discussed in the context of disk- and/or corona-reprocessing
scenarios, and of disk wind models. Similarities with the high-frequency
negative lag of 1H 0707-495 are highlighted, and, if confirmed, they would
support the hypothesis that the lag in PG 1211+143 represents the signature of
the same underlying mechanism, whose temporal characteristics scale with the
mass of the central object.Comment: 6 pages, 6 figures, accepted for publication in MNRAS Letter
Multiwavelength campaign on Mrk 509 XV. A global modeling of the broad emission lines in the Optical, UV and X-ray bands
We model the broad emission lines present in the optical, UV and X-ray
spectra of Mrk 509, a bright type 1 Seyfert galaxy. The broad lines were
simultaneously observed during a large multiwavelength campaign, using the
XMM-Newton-OM for the optical lines, HST-COS for the UV lines and
XMM-Newton-RGS and Epic for the X-ray lines respectively. We also used FUSE
archival data for the broad lines observed in the far-ultra-violet. The goal is
to find a physical connection among the lines measured at different wavelengths
and determine the size and the distance from the central source of the emitting
gas components. We used the "Locally optimally emission Cloud" (LOC) model
which interprets the emissivity of the broad line region (BLR) as regulated by
powerlaw distributions of both gas density and distances from the central
source. We find that one LOC component cannot model all the lines
simultaneously. In particular, we find that the X-ray and UV lines likely may
originate in the more internal part of the AGN, at radii in the range
~5x10^{14}-3x10^{17} cm, while the optical lines and part of the UV lines may
likely be originating further out, at radii ~3x10^{17}-3x^{18} cm. These two
gas components are parametrized by a radial distribution of the luminosities
with a slope gamma of ~1.15 and ~1.10, respectively, both of them covering at
least 60% of the source. This simple parameterization points to a structured
broad line region, with the higher ionized emission coming from closer in,
while the emission of the low-ionization lines is more concentrated in the
outskirts of the broad line region.Comment: 10 pages, 5 figures, accepted for publication in Astronomy and
Astrophysic
Ex vivo effect of vascular wall stromal cells secretome on enteric ganglia
BACKGROUND Mesenchymal stromal cell (MSC)-based therapy is currently under study to treat inflammatory bowel diseases. MSC bioactive products could represent a valid alternative to overcome issues associated with systemic whole-cell therapies. However, MSC anti-inflammatory mechanisms differ between rodents and humans, impairing the reliability of preclinical models. AIM To evaluate the effect of conditioned medium (CM) derived from porcine vascular wall MSCs (pVW-MSCs) on survival and differentiation of porcine and Guinea pig enteric ganglia exposed to lipopolysaccharide (LPS). METHODS Primary cultures of enteric ganglia were obtained by mechanic and enzymatic digestion of ileum resections from Guinea pigs (Cavia porcellus) (GPEG) and pigs (Suus scrofa) (PEG). pVW-MSCs were derived by enzymatic digestion from vascular wall resections of porcine aorta and tested by immunoflowcytometry for MSC immune profile. Enteric ganglia were treated with increasing concentrations of LPS, CM derived by pVW-MSCs or a combination of CM and LPS 1 \u3bcg/mL. Cell count and morphometric analysis of HuD positive neurons and glial fibrillary acidic protein positive glial cells were performed by immunofluorecent staining of cultured ganglia. RESULTS PEG showed a higher number of neurons compared to GPEG. Overall, CM exerted a protective role on LPS-treated enteric ganglia. CM in combination with LPS increased the number of glial cells per ganglion in both cultures evoking glial cells differentiation in porcine cultures. CONCLUSION These findings suggest an immunomodulating activity of pVW-MSCs mediators on the enteric nervous system in inflammatory conditions
- …