159 research outputs found
A highly-ionized absorber as a new explanation for the spectral changes during dips from X-ray binaries
Until now, the spectral changes observed from persistent to dipping intervals
in dipping low-mass X-ray binaries were explained by invoking progressive and
partial covering of an extended emission region. Here, we propose a novel and
simpler way to explain these spectral changes, which does not require any
partial covering and hence any extended corona, and further has the advantage
of explaining self-consistently the spectral changes both in the continuum and
the narrow absorption lines that are now revealed by XMM-Newton. In 4U 1323-62,
we detect Fe XXV and Fe XXVI absorption lines and model them for the first time
by including a complete photo-ionized absorber model rather than individual
Gaussian profiles. We demonstrate that the spectral changes both in the
continuum and the lines can be simply modeled by variations in the properties
of the ionized absorber. From persistent to dipping the photo-ionization
parameter decreases while the equivalent hydrogen column density of the ionized
absorber increases. In a recent work (see Diaz Trigo et al. in these
proceedings), we show that our new approach can be successfully applied to all
the other dipping sources that have been observed by XMM-Newton.Comment: 5 pages, 5 figures, to appear in the proceedings of "The X-ray
Universe 2005", San Lorenzo de El Escorial (Spain), 26-30 September 200
Extreme summer temperatures in Iberia: health impacts and associated synoptic conditions
This paper examines the effect of extreme summer temperatures on daily mortality in two large cities of Iberia: Lisbon (Portugal) and Madrid (Spain). Daily mortality and meteorological variables are analysed using the same methodology based on Box-Jenkins models. Results reveal that in both cases there is a triggering effect on mortality when maximum daily temperature exceeds a given threshold (34&deg;C in Lisbon and 36&deg;C in Madrid). The impact of most intense heat events is very similar for both cities, with significant mortality values occurring up to 3 days after the temperature threshold has been surpassed. This impact is measured as the percentual increase of mortality associated to a 1&deg;C increase above the threshold temperature. In this respect, Lisbon shows a higher impact, 31%, as compared with Madrid at 21%. The difference can be attributed to demographic and socio-economic factors. Furthermore, the longer life span of Iberian women is critical to explain why, in both cities, females are more susceptible than males to heat effects, with an almost double mortality impact value. <P style="line-height: 20px;"> The analysis of Sea Level Pressure (SLP), 500hPa geopotential height and temperature fields reveals that, despite being relatively close to each other, Lisbon and Madrid have relatively different synoptic circulation anomalies associated with their respective extreme summer temperature days. The SLP field reveals higher anomalies for Lisbon, but extending over a smaller area. Extreme values in Madrid seem to require a more western location of the Azores High, embracing a greater area over Europe, even if it is not as deep as for Lisbon. The origin of the hot and dry air masses that usually lead to extreme heat days in both cities is located in Northern Africa. However, while Madrid maxima require&nbsp;wind blowing directly from the south, transporting heat from Southern Spain and Northern Africa, Lisbon maxima occur under more easterly conditions, when Northern African air flows over the central Iberian plateau, which had been previously heated
Variations in the dip properties of the low-mass X-ray binary XB 1254-69 observed with XMM-Newton and INTEGRAL
We have analysed data from five XMM-Newton observations of XB 1254-69, one of
them simultaneous with INTEGRAL, to investigate the mechanism responsible for
the highly variable dips durations and depths seen from this low-mass X-ray
binary. Deep dips were present during two observations, shallow dips during one
and no dips were detected during the remaining two observations. At high (1-4
s) time resolution ``shallow dips'' are seen to include a few, very rapid, deep
dips whilst the ``deep'' dips consist of many similar very rapid, deep,
fluctuations. The folded V-band Optical Monitor light curves obtained when the
source was undergoing deep, shallow and no detectable dipping exhibit
sinusoid-like variations with different amplitudes and phases. We fit EPIC
spectra obtained from "persistent" or dip-free intervals with a model
consisting of disc-blackbody and thermal comptonisation components together
with Gaussian emission features at 1 and 6.6 keV modified by absorption due to
cold and photo-ionised material. None of the spectral parameters appears to be
strongly correlated with the dip depth except for the temperature of the disc
blackbody which is coolest (kT ~ 1.8 keV) when deep dips are present and
warmest (kT ~ 2.1 keV) when no dips are detectable. We propose that the changes
in both disc temperature and optical modulation could be explained by the
presence of a tilted accretion disc in the system. We provide a revised
estimate of the orbital period of 0.16388875 +/- 0.00000017 day.Comment: 16 pages, 10 figures, 4 tables. Accepted for publication in A&
Simultaneous detection of an intrinsic absorber and a compact jet emission in the X-ray binary IGR J17091-3624 during a hard accretion state
We present a detailed analysis of three XMM-Newton observations of the black
hole low-mass X-ray binary IGR~J17091-3624 taken during its 2016 outburst.
Radio observations obtained with the Australia Telescope Compact Array (ATCA)
indicate the presence of a compact jet during all observations. From the best
X-ray data fit results we concluded that the observations were taken during a
transition from a hard accretion state to a hard-intermediate accretion state.
For Observations 1 and 2 a local absorber can be identified in the EPIC-pn
spectra but not in the RGS spectra, preventing us from distinguishing between
absorption local to the source and that from the hot ISM component. For
Observation 3, on the other hand, we have identified an intrinsic ionized
static absorber in both EPIC-pn and RGS spectra. The absorber, observed
simultaneously with a compact jet emission, is characterized by an ionization
parameter of 1.96< log({\xi}) <2.05 and traced mainly by Ne X, Mg XII, Si XIII
and Fe XVIII.Comment: 13 pages, 10 figure
A search for signatures of interactions of X-ray binary outflows with their environments with ALMA
We observed the X-ray binaries CirX-1, ScoX-1, GRS 1915+105, GX13+1, and
CygX-1 with the Atacama Large Millimeter/submillimeter Array (ALMA). Unresolved
continuum emission is found at the positions of all the sources at a frequency
of 92 GHz, with flux densities ranging between 0.8 and 10 mJy/beam. In all
cases the emission can be associated with jets that have been extensively
observed at lower frequencies. We searched for line emission from H
recombination, SiO,H2O, and CH3OH at the positions of all the sources and, for
CirX-1 and CygX-1, also at regions where shocks associated with an interaction
between the jet and the interstellar medium had previously been observed. The
search did not yield any significant detection, resulting in 3 upper
limits between 0.65 and 3.7 K km s for the existence of line emission in
these regions. In contrast, we detected spatially unresolved SiO emission in
the field of view of GX13+1, and we tentatively associate this emission with a
SiO maser in a potential young stellar object or evolved star. We also found
spatially extended line emission at two additional sites in the field of view
of GX13+1 that we tentatively associate with emission from SO and CH3OH; we
speculate that it may be associated with a star-forming region, but again we
cannot rule out alternative origins such as emission from evolved stars.Comment: Accepted for publication in A&
XMM-Newton observations reveal the disappearance of the wind in 4U1630-47
We report on XMM-Newton observations of the black hole X-ray binary 4Uâ1630â47 during its 2012â2013 outburst. The first five observations monitor the source as its luminosity increases across the highâsoft state of accretion. In the sixth observation the source has made a transition to an âanomalousâ state, characterised by a significant contribution of electron scattering. A thermally/radiatively driven disc wind is present in the first four observations, which becomes more photoionised as the luminosity increases with time. In the fifth observation, the wind is not observed any more as a consequence of strong photoionisation and the low sensitivity of this observation. This overall trend is then consistent with a fully ionised wind causing the electron scattering characteristic of the anomalous state in the sixth observation. A broad iron emission line co-exists with the absorption features from the wind in the first four observations but is not visible in the last two observations. We find that the changes in the state of the wind as measured from modelling the absorption features with a self-consistent warm absorber model are correlated to the changes in the broad iron line. When the latter is modelled with a reflection component we find that the reflection fraction decreases as the illumination increases. We propose that the changes in both the absorption and broad emission lines are caused by the increasing luminosity and temperature of the accretion disc along the soft state. Such changes ultimately enable the transition to a state where the wind is fully ionised and consequently Comptonisation plays a significant role
XMM-Newton and INTEGRAL spectroscopy of the microquasar GRO J1655-40 during its 2005 outburst
We report on two simultaneous XMM-Newton and INTEGRAL observations of the
microquasar GRO J1655-40 during the 2005 outburst when the source was in its
high-soft state. The 0.3-200 keV spectra are complex with an overall continuum
which may be modeled using an absorbed blackbody together with a weak, steep,
power-law component. In addition, there is evidence for the presence of both a
relativistically broadened Fe K line and a highly photo-ionized absorber. The
photo-ionized absorber is responsible for strong K absorption lines of Fe XXV
and Fe XXVI in the EPIC pn spectra and blue-shifted (v = -540 +/- 120 km/s) Ne
X and Fe XXIV features in the RGS spectra. The parameters of the photo-ionized
absorber were different during the two observations with the ionization
parameter, logxi, decreasing from 3.60 +/- 0.04 to 3.30 +/- 0.04 erg cm/s and
the column density decreasing from (5.2 +/- 1.0) x 10^22 atom cm-2 to (1.5 +/-
1.0) x 10^22 atom cm-2 during the first and second observations as the 0.5-200
keV GRO J1655-40 luminosity decreased by around a half. At 90% confidence the
INTEGRAL data show no evidence of a break in the power-law component up to
energies of 380 keV and 90 keV for the first and second observations,
respectively.Comment: Accepted for publication in A&A (submitted: 11 April 2006). 12 pages,
7 figure
A systematic analysis of the broad Fe Kalpha line in neutron star LMXBs with XMM-Newton
We analysed the XMM-Newton archival observations of 16 neutron star (NS)
low-mass X-ray binaries (LMXBs) to study the Fe K emission in these objects.
The sample includes all the observations of NS LMXBs performed in EPIC pn
Timing mode with XMM-Newton publicly available until September 30, 2009. We
performed a detailed data analysis considering pile-up and background effects.
The properties of the iron lines differed from previous published analyses due
to either incorrect pile-up corrections or different continuum
parameterization. 80% of the observations for which a spectrum can be extracted
showed significant Fe line emission. We found an average line centroid of 6.67
0.02 keV and a finite width, , of 0.33 0.02 keV. The
equivalent width of the lines varied between 17 and 189 eV, with an average
weighted value of 42 eV. For sources where several observations were
available the Fe line parameters changed between observations whenever the
continuum changed significantly. The line parameters did not show any
correlation with luminosity. Most important, we could fit the Fe line with a
simple Gaussian component for all the sources. The lines did not show the
asymmetric profiles that were interpreted as an indication of relativistic
effects in previous analyses of these LMXBs.Comment: Accepted for publication in A&
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