945 research outputs found
The transitional millisecond pulsar IGR J18245-2452 during its 2013 outburst at X-rays and soft gamma-rays
IGR~J18245--2452/PSR J1824--2452I is one of the rare transitional accreting
millisecond X-ray pulsars, showing direct evidence of switches between states
of rotation powered radio pulsations and accretion powered X-ray pulsations,
dubbed transitional pulsars. IGR~J18245--2452 is the only transitional pulsar
so far to have shown a full accretion episode, reaching an X-ray luminosity of
~erg~s permitting its discovery with INTEGRAL in 2013. In
this paper, we report on a detailed analysis of the data collected with the
IBIS/ISGRI and the two JEM-X monitors on-board INTEGRAL at the time of the 2013
outburst. We make use of some complementary data obtained with the instruments
on-board XMM-Newton and Swift in order to perform the averaged broad-band
spectral analysis of the source in the energy range 0.4 -- 250~keV. We have
found that this spectrum is the hardest among the accreting millisecond X-ray
pulsars. We improved the ephemeris, now valid across its full outburst, and
report the detection of pulsed emission up to keV in both the ISGRI
() and Fermi/GBM () bandpass. The alignment of the
ISGRI and Fermi GBM 20 -- 60 keV pulse profiles are consistent at a $\sim25\
\mu$s level. We compared the pulse profiles obtained at soft X-rays with \xmm\
with the soft \gr-ray ones, and derived the pulsed fractions of the fundamental
and first harmonic, as well as the time lag of the fundamental harmonic, up to
s, as a function of energy. We report on a thermonuclear X-ray burst
detected with \Integ, and using the properties of the previously type-I X-ray
burst, we show that all these events are powered primarily by helium ignited at
a depth of g cm. For such a helium
burst the estimated recurrence time of d is in
agreement with the observations.Comment: 10 pages, 6 Figures, 3 Tables Astronomy and Astrophysics Journal,
accepted for publication on the 13th of April 201
Discovery of new quasi-periodic oscillations in the X-ray transient source V~0332+53
We report the discovery of a new quasi-period oscillation (QPO) at 0.22 Hz,
centered on the source spin frequency of the high mass X-ray binary system
V~0332+53 when the source was observed during its November 2004/March 2005
outburst by {\em RXTE}. Besides this new QPO, we also detected the known 0.05
Hz QPO. Both the 0.22 and 0.05 Hz QPOs stand out clearly at a mid-flux level of
the outburst within January 15--19 2005, and later at an even lower flux level
as the width of 0.22 Hz QPO drops. No evolution of the centroid frequency with
the flux is seen in either QPO. The rms value below 10 keV is around 4--6% for
both QPOs and decreases at higher energies. We discuss our results in the
context of current QPO models.Comment: 5 figures, 12 pages. AASTex preprint style. (In 2005, ApJ Let., 629,
L33
Flexibility of Gender Stereotypes: Italian Study on Comparative Gender-consistent and Gender-inconsistent Information
The topic of this study is flexibility in gender stereotyping linked to attribution of toys, socio-cognitive traits, and occupations in 160 Italian children aged 6 to 12 years. We used the Gender Toys Choice, the Gender Traits Choice, and the Gender Jobs Choice, a selected set of colored cards containing masculine and feminine stimuli to assign to a male or female or both male and female silhouette (the flexible-choice technique). In order to verify the change of flexibility in gender stereotyping, we made use of four cartoon stories with male and female characters with typical or atypical traits and performing gender-consistent or gender-inconsistent activities. Results indicated that the exposure to cartoon stories with gender-inconsistent information rather than cartoon stories with gender-consistent information increased flexibility in gender stereotyping, showing age differences in favor of children aged 11-12. Implications in relation to the developmental-constructivist approach were noted
La citt\ue0 come laboratorio di trasformazione. Processi partecipativi e modelli urbani circolari.
In contemporary European cities, urban transformations in terms of conservation, development and adaptive reuse follow new models whose adoption, acceptance and impact are closely dependent on different elements, including the need to attract new investment, the stimulation of the tourism economy, the capital allocation: these factors if not properly controlled and managed can compromise cities\u2019 future sustainable growth. The research group of the Department of Architecture of Bologna, working with the Institute of Social Sciences of the University of Lisbon, is focusing its lines of research and experimentation on the historical city, working together under the umbrella of H2020 ROCK project, on the introduction of factors of innovation (technological, environmental, social and economic) in the processes of urban transformation can pursue challenges of systemic and integrated value and become engines of growth and sustainable development at urban scale. The paper illustrates the ROCK circular urban system approach and its replication potential in different territorial contexts, such as Bologna and Bogot\ue0, in connection with BOND project
Optical Photometry and Spectroscopy of the Accretion-Powered Millisecond Pulsar HETE J1900.1-2455
We present phase resolved optical photometry and spectroscopy of the
accreting millisecond pulsar HETE J1900.1-2455. Our R-band light curves exhibit
a sinusoidal modulation, at close to the orbital period, which we initially
attributed to X-ray heating of the irradiated face of the secondary star.
However, further analysis reveals that the source of the modulation is more
likely due to superhumps caused by a precessing accretion disc. Doppler
tomography of a broad Halpha emission line reveals an emission ring, consistent
with that expected from an accretion disc. Using the velocity of the emission
ring as an estimate for the projected outer disc velocity, we constrain the
maximum projected velocity of the secondary to be 200 km/s, placing a lower
limit of 0.05 Msun on the secondary mass. For a 1.4 Msun primary, this implies
that the orbital inclination is low, < 20 degrees. Utilizing the observed
relationship between the secondary mass and orbital period in short period
cataclysmic variables, we estimate the secondary mass to be ~0.085 Msun, which
implies an upper limit of ~2.4 Msun for the primary mass.Comment: 8 pages, 6 figures; Accepted for publication in MNRAS. Minor
revisions to match final published versio
Multi-wavelength observations of IGR J17544-2619 from quiescence to outburst
In this paper we report on a long multi-wavelength observational campaign of
the supergiant fast X-ray transient prototype IGR J17544-2619. A 150 ks-long
observation was carried out simultaneously with XMM-Newton and NuSTAR, catching
the source in an initial faint X-ray state and then undergoing a bright X-ray
outburst lasting about 7 ks. We studied the spectral variability during
outburst and quiescence by using a thermal and bulk Comptonization model that
is typically adopted to describe the X-ray spectral energy distribution of
young pulsars in high mass X-ray binaries. Although the statistics of the
collected X-ray data were relatively high we could neither confirm the presence
of a cyclotron line in the broad-band spectrum of the source (0.5-40 keV), nor
detect any of the previously reported tentative detection of the source spin
period. The monitoring carried out with Swift/XRT during the same orbit of the
system observed by XMM-Newton and NuSTAR revealed that the source remained in a
low emission state for most of the time, in agreement with the known property
of all supergiant fast X-ray transients being significantly sub-luminous
compared to other supergiant X-ray binaries. Optical and infrared observations
were carried out for a total of a few thousands of seconds during the
quiescence state of the source detected by XMM-Newton and NuSTAR. The measured
optical and infrared magnitudes were slightly lower than previous values
reported in the literature, but compatible with the known micro-variability of
supergiant stars. UV observations obtained with the UVOT telescope on-board
Swift did not reveal significant changes in the magnitude of the source in this
energy domain compared to previously reported values.Comment: Accepted for publication on A&A. V2: few typos correcte
First observations of the X-ray transient EXO 2030+375 with IBIS/ISGRI
We present a first INTEGRAL observation of the 42s transient X-ray pulsar EXO
2030+375 with IBIS/ISGRI. The source was detected during Cyg X-1 observations
in December 2002. We analyzed observations during the outburst period from 9 to
21 December 2002 with a total exposure time of ~770 kiloseconds. EXO 2030+375
was almost always detected during single ~30 minute exposures in the 18-45
energy bands. The source light curve shows the characteristic outburst shape
observed in this source.Comment: 4 pages, 3 figures (1 in CMYK color), accepted by Astronomy and
Astrophysics, INTEGRAL special issue, 200
Engineering of janus-like dendrimers with peptides derived from glycoproteins of herpes simplex virus type 1: Toward a versatile and novel antiviral platform
Novel antiviral nanotherapeutics, which may inactivate the virus and block it from entering host cells, represent an important challenge to face viral global health emergencies around the world. Using a combination of bioorthogonal copper-catalyzed 1,3-dipolar alkyne/azide cycloaddition (CuAAC) and photoinitiated thiol–ene coupling, monofunctional and bifunctional peptidodendrimer conjugates were obtained. The conjugates are biocompatible and demonstrate no toxicity to cells at biologically relevant concentrations. Furthermore, the orthogonal addition of multiple copies of two different antiviral peptides on the surface of a single dendrimer allowed the resulting biocon-jugates to inhibit Herpes simplex virus type 1 at both the early and the late stages of the infection process. The presented work builds on further improving this attractive design to obtain a new class of therapeutics
The 2015 outburst of the accretion-powered pulsar IGR J00291+5934: INTEGRAL and Swift observations
The pulsar IGR J00291 + 5934 is the fastest-known accretion-powered X-ray pulsar, discovered during a transient outburst in 2004. In this paper, we report on INTEGRAL and Swift observations during the 2015 outburst, which lasts for similar to 25 d. The source has not been observed in outburst since 2008, suggesting that the long-term accretion rate has decreased by a factor of two since discovery. The averaged broad-band (0.1-250 keV) persistent spectrum in 2015 is well described by a thermal Comptonization model with a column density of NH4 approximate to 10(21) cm(-2), a plasma temperature of kT(e) approximate to 50 keV, and a Thomson optical depth of tau(T) approximate to 1. Pulsations at the known spin period of the source are detected in the INTEGRAL data up to the similar to 150 keV energy band. We also report on the discovery of the first thermonuclear burst observed from IGR J00291 + 5934, which lasts around 7 min and occurs at a persistent emission level corresponding to roughly 1 : 6% of the Eddington accretion rate. The properties of the burst suggest it is powered primarily by helium ignited at a depth of y(ign) approximate to 1.5 x 10(9) g cm(-2) following the exhaustion by steady burning of the accreted hydrogen. The Swift/BAT data from the first similar to 20 s of the burst provide indications of a photospheric radius expansion phase. Assuming this is the case, we infer a source distance of d = 4 : 2 +/- 0.5 kpc
Influence of Compton scattering on the broad-band X-ray spectra of intermediate polars
Context. The majority of cataclysmic variables observed in the hard X-ray energy band are intermediate polars where the magnetic field is strong enough to channel the accreting matter to the magnetic poles of the white dwarf. A shock above the stellar surface heats the gas to fairly high temperatures (10-100 keV). The post-shock region cools mostly via optically thin bremsstrahlung.Aims. We investigate the influence of Compton scattering on the structure and the emergent spectrum of the post-shock region. We also study the effect it has on the mass of the white dwarfs obtained from fitting the observed X-ray spectrum of intermediate polars. Methods. We construct the model of the post-shock region taking Compton scattering into account. The radiation transfer equation is solved in the plane-parallel approximation. The feedback of Compton scattering on the structure of the post-shock region is also accounted for. A set of the post-shock region model spectra for various white dwarf masses is calculated.Results. We find that Compton scattering does not change the emergent spectra significantly for low accretion rates or low white dwarf masses. However, it becomes important at high accretion rates and high white dwarf masses. The time-averaged, broad-band X-ray spectrum of intermediate polar V709 Cas obtained by the RXTE and and INTEGRAL observatories is fitted using the set of computed spectral models. We obtained the white dwarf mass of 0.90 ± 0.02 M⊙ and 0.88 ± 0.02 M⊙ using models with Compton scattering taken into account and without it, respectively. © 2008 ESO
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