Population of the Galactic X-ray binaries and eRosita

The population of the Galactic X-ray binaries has been mostly probed with moderately sensitive hard X-ray surveys so far. The eRosita mission will provide, for the first time a sensitive all-sky X-ray survey in the 2-10 keV energy range, where the X-ray binaries emit most of the flux and discover the still unobserved low-luminosity population of these objects. In this paper, we briefly review the current constraints for the X-ray luminosity functions of high- and low-mass X-ray binaries and present our own analysis based the INTEGRAL 9-year Galactic survey, which yields improved constraints. Based on these results, we estimate the number of new XRBs to be detected in the eRosita all-sky surveyComment: accepted for publication in A&

XMM-Newton observation of the interacting galaxies NGC1512 and NGC1510

The galaxy NGC1512 is interacting with the smaller galaxy NGC1510 and shows a peculiar morphology, characterised by two extended arms immersed in an HI disc whose size is about four times larger than the optical diameter of NGC1512. For the first time we performed a deep X-ray observation of the galaxies NGC1512 and NGC1510 with XMM-Newton to gain information on the population of X-ray sources and diffuse emission in a system of interacting galaxies. We identified and classified the sources detected in the XMM-Newton field of view by means of spectral analysis, hardness-ratios calculated with a Bayesian method, X-ray variability, and cross-correlations with catalogues in optical, infrared, and radio wavelengths. We also made use of archival Swift (X-ray) and Australia Telescope Compact Array (radio) data to better constrain the nature of the sources detected with XMM-Newton. We detected 106 sources in the energy range of 0.2-12 keV, out of which 15 are located within the D_25 regions of NGC1512 and NGC1510 and at least six sources coincide with the extended arms. We identified and classified six background objects and six foreground stars. We discussed the nature of a source within the D_25 ellipse of NGC1512, whose properties indicate a quasi-stellar object or an intermediate ultra-luminous X-ray source. Taking into account the contribution of low-mass X-ray binaries and active galactic nuclei, the number of high-mass X-ray binaries detected within the D_25 region of NGC1512 is consistent with the star formation rate obtained in previous works based on radio, infrared optical, and UV wavelengths. We detected diffuse X-ray emission from the interior region of NGC1512 with a plasma temperature of kT=0.68(0.31-0.87) keV and a 0.3-10 keV X-ray luminosity of 1.3E38 erg/s, after correcting for unresolved discrete sources.Comment: Accepted for publication in Astronomy and Astrophysics. 20 pages. Appendix B will be published electronically onl

Optical and near-infrared photometric monitoring of the transient X-ray binary A0538-66 with REM

The transient Be/X-ray binary A0538-66 shows peculiar X-ray and optical variability. Despite numerous studies, the intrinsic properties underlying its anomalous behaviour remain poorly understood. Since 2014 September we are conducting the first quasi-simultaneous optical and near-infrared photometric monitoring of A0538-66 in seven filters with the Rapid Eye Mount (REM) telescope, aiming to understand the properties of this binary system. We found that the REM lightcurves show fast flares lasting one or two days that repeat almost regularly every ~16.6 days, the orbital period of the neutron star. If the optical flares are powered by X-ray outbursts through photon reprocessing, the REM lightcurves indicate that A0538-66 is still active in X-rays: bright X-ray flares (L_x > 1E37 erg/s) could be observable during the periastron passages. The REM lightcurves show a long-term variability that is especially pronounced in the g band and decreases with increasing wavelength, until it no longer appears in the near-infrared lightcurves. In addition, A0538-66 is fainter with respect to previous optical observations most likely due to the higher absorption of the stellar radiation of a denser circumstellar disc. On the basis of the current models, we interpret these observational results with a circumstellar disc around the Be star observed nearly edge-on during a partial depletion phase. The REM lightcurves also show short-term variability on timescales of ~1 day possibly indicative of perturbations in the density distribution of the circumstellar disc caused by the tidal interaction with the neutron star.Comment: Accepted for publication in Astronomy & Astrophysic

Properties and observability of glitches and anti-glitches in accreting pulsars

Several glitches have been observed in young, isolated radio pulsars, while a clear detection in accretion-powered X-ray pulsars is still lacking. We use the Pizzochero snowplow model for pulsar glitches as well as starquake models to determine for the first time the expected properties of glitches in accreting pulsars and their observability. Since some accreting pulsars show accretion-induced long-term spin-up, we also investigate the possibility that anti-glitches occur in these stars. We find that glitches caused by quakes in a slow accreting neutron star are very rare and their detection extremely unlikely. On the contrary, glitches and anti-glitches caused by a transfer of angular momentum between the superfluid neutron vortices and the non-superfluid component may take place in accreting pulsars more often. We calculate the maximum jump in angular velocity of an anti-glitch and we find that it is expected to be about 1E-5 - 1E-4 rad/s. We also note that since accreting pulsars usually have rotational angular velocities lower than those of isolated glitching pulsars, both glitches and anti-glitches are expected to have long rise and recovery timescales compared to isolated glitching pulsars, with glitches and anti-glitches appearing as a simple step in angular velocity. Among accreting pulsars, we find that GX 1+4 is the best candidate for the detection of glitches with currently operating X-ray instruments and future missions such as the proposed Large Observatory for X-ray Timing (LOFT).Comment: Accepted for publication in Astronomy & Astrophysics. 6 pages. Minor changes to match the final A&A versio

Spectral and temporal properties of the supergiant fast X-ray transient IGR J18483-0311 observed by INTEGRAL

IGR J18483-0311 is a supergiant fast X-ray transient whose compact object is located in a wide (18.5 d) and eccentric (e~0.4) orbit, which shows sporadic outbursts that reach X-ray luminosities of ~1e36 erg/s. We investigated the timing properties of IGR J18483-0311 and studied the spectra during bright outbursts by fitting physical models based on thermal and bulk Comptonization processes for accreting compact objects. We analysed archival INTEGRAL data collected in the period 2003-2010, focusing on the observations with IGR J18483-0311 in outburst. We searched for pulsations in the INTEGRAL light curves of each outburst. We took advantage of the broadband observing capability of INTEGRAL for the spectral analysis. We observed 15 outbursts, seven of which we report here for the first time. This data analysis almost doubles the statistics of flares of this binary system detected by INTEGRAL. A refined timing analysis did not reveal a significant periodicity in the INTEGRAL observation where a ~21s pulsation was previously detected. Neither did we find evidence for pulsations in the X-ray light curve of an archival XMM-Newton observation of IGR J18483-0311. In the light of these results the nature of the compact object in IGR J18483-0311 is unclear. The broadband X-ray spectrum of IGR J18483-0311 in outburst is well fitted by a thermal and bulk Comptonization model of blackbody seed photons by the infalling material in the accretion column of a neutron star. We also obtained a new measurement of the orbital period using the Swift/BAT light curve.Comment: Accepted for publication in Astronomy and Astrophysics. 8 page

Spatial distribution of unidentified infrared bands and extended red emission in the compact galactic HII region Sh 152

We present visible and near IR images of the compact HII region Sh 152. Some of these images reveal the presence of Extended Red Emission (ERE) around 698 nm and emission from Unidentified Infra Red Bands (UIRBs) at 3.3 and 6.2 micron. Other images show the near infrared (7-12 micron) continuous emission of the nebula. The ERE emission is found to coincide with the ionized region and significantly differ from the UIRBs location. Also some evidence is found in favor of grains as carriers for ERE.Comment: 3 pages, 4 figures, to be published in the proceedings of the colloquium "The universe as seen by ISO" help in Paris, October 20-23, 1998 ; available in html format at http://www.obs-hp.fr/preprints.htm

Flow, suspension, and mixing dynamics in DASGIP bioreactors: Part 1

The bioreactor flow environment has a significant impact on process performance, especially in stem cell cultures. The work of Correia et al found intermittent agitation modes to improve induced pluripotent stem cell (iPSC)‐cardiomyocyte differentiation yields; however, to date, the impact within the flow has not been fully characterized. This work aims to characterize the flow dynamics occurring within a commercially available DASGIP bioreactor, equipped with a two‐blade paddle impeller, operating under different agitation modes and for two bottom geometries. The paddle impeller configuration generated an axial flow profile due to a large impeller D/T and blade confinement with the bioreactor wall. The application of intermittent agitation was shown to induce two transient spikes in flow velocity and shear stress, the amplification of which increased with dwell duration. Marginally increasing the dwell duration was shown previously to increase differentiation yields, therefore it can be stipulated that introduction of these spikes was favorable toward cardiogenic differentiation