IBIS preliminary results on Cygnus X-1 spectral and temporal characteristics

We report preliminary results of a broadband spectral and temporal study of the black-hole binary Cyg X-1 performed with the IBIS telescope. Cyg X-1 was the first pointed celestial target of IBIS during the INTEGRAL Performance and Verification Phase, 2002 Nov.-Dec., for a total observing time of 2 Ms in both staring and dithering mode. Here, we report on only the staring, on-axis, observation performed in a stable instrument configuration. During the observing period the source was in its characteristic low/hard state, in which a few flares and dips have been detected. The IBIS/ISGRI results demonstrate that the INTEGRAL observatory offers a unique capability for studying correlations between hardness and/or flux in different bands over a wide photon energy range. One of our new results is finding that the hardness-flux correlation changes the sign twice over the 20-220 keV; first from positive to negative at 50 keV, and then back to positive at 120 keV. The former change appears to be due to the spectral curvature introduced by variable Compton reflection. The latter may be due spectral pivoting.Comment: 7 pages, 8 figures (4 in color), accepted for publication in A&A, INTEGRAL special issu

Bacterial virulence factor inhibits caspase-4/11 activation in intestinal epithelial cells

The human pathogen enteropathogenic Escherichia coli (EPEC), as well as the mouse pathogen Citrobacter rodentium, colonize the gut mucosa via attaching and effacing lesion formation and cause diarrheal diseases. EPEC and C. rodentium type III secretion system (T3SS) effectors repress innate immune responses and infiltration of immune cells. Inflammatory caspases such as caspase-1 and caspase-4/11 are crucial mediators of host defense and inflammation in the gut via their ability to process cytokines such as interleukin (IL)-1β and IL-18. Here we report that the effector NleF binds the catalytic domain of caspase-4 and inhibits its proteolytic activity. Following infection of intestinal epithelial cells (IECs) EPEC inhibited caspase-4 and IL-18 processing in an NleF-dependent manner. Depletion of caspase-4 in IECs prevented the secretion of mature IL-18 in response to infection with EPECΔnleF. NleF-dependent inhibition of caspase-11 in colons of mice prevented IL-18 secretion and neutrophil influx at early stages of C. rodentium infection. Neither wild-type C. rodentium nor C. rodentiumΔnleF triggered neutrophil infiltration or IL-18 secretion in Cas11 or Casp1/11-deficient mice. Thus, IECs have a key role in modulating early innate immune responses in the gut via a caspase-4/11—IL-18 axis, which is targeted by virulence factors encoded by enteric pathogens

First Results from the IBIS/ISGRI Data Obtained During the Galactic Plane Scan. II. The Vela Region

We report on INTEGRAL/IBIS observations of the Vela region during a Galactic Plane Scan (hereafter GPS) presenting the IBIS in-flight performances during these operations. Among all the known sources in the field of view we clearly detect 4U 0836-429, Vela X-1, Cen X-3, GX 301-2, 1E 1145.1-6141, and H0918-549 in the 20-40 keV energy range. Only Vela X-1 and GX 301-2 are detected in the 40-80 keV energy range, and no sources are visible above. We present the results of each individual observation (~2200 s exposure), as well as those from the mosaic of these scans.Comment: 4 pages, 3 color figures, accepted for publication in the INTEGRAL special edition of A&A Letter

Myogenic cell proliferation and generation of a reversible tumorigenic phenotype are triggered by preirradiation of the recipient site

Environmental influences have profound yet reversible effects on the behavior of resident cells. Earlier data have indicated that the amount of muscle formed from implanted myogenic cells is greatly augmented by prior irradiation (18 Gy) of the host mouse muscle. Here we confirm this phenomenon, showing that it varies between host mouse strains. However, it is unclear whether it is due to secretion of proliferative factors or reduction of antiproliferative agents. To investigate this further, we have exploited the observation that the immortal myogenic C2 C12 cell line forms tumors far more rapidly in irradiated than in nonirradiated host muscle. We show that the effect of preirradiation on tumor formation is persistent and dose dependent. However, C2 C12 cells are not irreversibly compelled to form undifferentiated tumor cells by the irradiated muscle environment and are still capable of forming large amounts of muscle when reimplanted into a nonirradiated muscle. In a clonal analysis of this effect, we discovered that C2 C12 cells have a bimodal propensity to form tumors; some clones form no tumors even after extensive periods in irradiated graft sites, whereas others rapidly form extensive tumors. This illustrates the subtle interplay between the phenotype of implanted cells and the factors in the muscle environment

Unveiling the disc structure in ultraluminous X-ray source NGC 55 ULX-1

© 2022 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is the accepted manuscript version of an article which has been published in final form athttps://doi.org/10.1093/mnras/stac2453Despite two decades of studies, it is still not clear whether ULX spectral transitions are due to stochastic variability in the wind or variations in the accretion rate or in the source geometry. The compact object is also unknown for most ULXs. In order to place constraints onto such scenarios and on the structure of the accretion disc, we studied the temporal evolution of the spectral components of the variable source NGC 55 ULX-1. Using recent and archival data obtained with the XMM-Newton satellite, we modelled the spectra with two blackbody components which we interpret as thermal emission from the inner accretion flow and the regions around or beyond the spherization radius. The luminosity-temperature (L-T) relation of each spectral component agrees with the L proportional T^4 relationship expected from a thin disc model, which suggests that the accretion rate is close to the Eddington limit. However, there are some small deviations at the highest luminosities, possibly due to an expansion of the disc and a contribution from the wind at higher accretion rates. Assuming that such deviations are due to the crossing of the Eddington or supercritical accretion rate, we estimate a compact object mass of 6-14 Msun, favouring a stellar-mass black hole as the accretor.Peer reviewe

Central Nervous System Parasitosis and Neuroinflammation Ameliorated by Systemic IL-10 Administration in Trypanosoma brucei-Infected Mice

Peer reviewedPublisher PD

GRB021125: the first GRB imaged by INTEGRAL

In the late afternoon of November 25, 2002 a gamma-ray burst (GRB) was detected in the partially coded field of view (about 7.3 deg from the centre) of the imager IBIS on board the INTEGRAL satellite. The instruments on-board INTEGRAL allowed, for the first time, the observation of the prompt gamma-ray emission over a broad energy band from 15 to 500 keV. GRB021125 lasted ~24 s with a mean flux of ~5.0 photons/cm^2/s in the 20-500 keV energy band, and a fluence of 4.8x10^-5 erg/cm^2 in the same energy band. Here we report the analysis of the data from the imager IBIS and the spectrometer SPI.Comment: 4 pages, 5 figures. Accepted for publication on A&A: Special Issue on First Science with INTEGRA