Theoretical Black Hole Mass Distributions

We derive the theoretical distribution function of black hole masses by studying the formation processes of black holes. We use the results of recent 2D simulations of core-collapse to obtain the relation between remnant and progenitor masses and fold it with an initial mass function for the progenitors. We examine how the calculated black-hole mass distributions are modified by (i) strong wind mass loss at different evolutionary stages of the progenitors, and (ii) the presence of close binary companions to the black-hole progenitors. Thus, we are able to derive the binary black hole mass distribution. The compact remnant distribution is dominated by neutron stars in the mass range 1.2-1.6Msun and falls off exponentially at higher remnant masses. Our results are most sensitive to mass loss from winds which is even more important in close binaries. Wind mass-loss causes the black hole distribution to become flatter and limits the maximum possible black-hole mass (<10-15Msun). We also study the effects of the uncertainties in the explosion and unbinding energies for different progenitors. The distributions are continuous and extend over a broad range. We find no evidence for a gap at low values (3-5Msun) or for a peak at higher values (~7Msun) of black hole masses, but we argue that our black hole mass distribution for binaries is consistent with the current sample of measured black-hole masses in X-ray transients. We discuss possible biases against the detection or formation of X-ray transients with low-mass black holes. We also comment on the possibility of black-hole kicks and their effect on binaries.Comment: 22 pages, submitted to Ap

Intra-abdominal pressure alterations after large pancreatic pseudocyst transcutaneous drainage

<p>Abstract</p> <p>Background</p> <p>Acute pancreatitis leads to abdominal hypertension and compartment syndrome. Weeks after the episodes pancreatic fluids sometimes organize to pseudocysts, fluid collections by or in the gland.</p> <p>Aims of the present study were to evaluate the intra-abdominal pressure (IAP) induced by large pancreatic pseudocysts and to examine the effect of their transcutaneous drainage on IAP.</p> <p>Methods</p> <p>Twenty seven patients with a pancreatic pseudocyst were included. Nine patients with pseudocysts greater than 1l (group A) had CT drainage and eighteen (volume less than 1l) were the control group. The measurements of group A were taken 6 hours before and every morning after the drainage, while for group B, two measurements were performed, one at the day of the initial CT and one 7 days after. Abdominal compliance (Cabd) was calculated. Data were analyzed using student's <it>t</it>-test.</p> <p>Results</p> <p>Baseline IAP for group A was 9.3 mmHg (S.D. 1.7 mmHg), while the first post-drainage day (PDD) IAP was 5.1 mmHg (S.D. 0.7 mmHg). The second PDD IAP was 5.6 mmHg (S.D. 0.8 mmHg), the third 6.4 mmH (S.D. 1.2 mmHg)g, the fourth 6.9 mmHg (S.D. 1.6 mmHg), the fifth 7.9 mmHg (S.D. 1.5 mmHg), the sixth 8.2 mmHg (S.D. 1.4 mmHg), and the seventh 8.2 mmHg (S.D. 1.5 mmHg). Group B had baseline IAP 8.0 mmHg (S.D. 1.2 mmHg) and final 8.2 mmHg (S.D. 1.4 mmHg). Cabd after drainage was 185.6 ml/mmHg (SD 47.5 ml/mmHg).</p> <p>IAP values were reduced between the baseline and all the post-drainage measurements in group A. IAPs seem to stabilize after the 5^thpost-drainage day. Baseline IAP was higher in group A than in group B, while the two values, at day 7, were equivalent.</p> <p>Conclusion</p> <p>The drainage of large pancreatic pseudocyst reduces IAP. Moreover, the IAP seems to rise shortly after the drainage again, but in a way that it remains inferior to the initial value. More chronic changes to the IAP are related to abdominal cavity's properties and have to be further studied.</p

Implications of X-Ray Line Variations for 4U1822-371

4U 1822-371 is one of the proto-type accretion disk coronal sources with an orbital period of about 5.6 hours. The binary is viewed almost edge-on at a high inclination angle of 83 degrees, which makes it a unique candidate to study binary orbital and accretion disk dynamics in high powered X-ray sources. We observed the X-ray source in 4U 1822-371 with the Chandra High Energy Transmission Grating Spectrometer (HETGS) for almost nine binary orbits. X-ray eclipse times provide an update of the orbital ephemeris. We find that our result follows the quadratic function implied by previous observations; however, it suggests a flatter trend. Detailed line dynamics also confirm a previous suggestion that the observed photo-ionized line emission originates from a confined region in the outer edge of the accretion disk near the hot spot. Line properties allow us to impose limits on the size of accretion disk, the central corona, and the emission region. The photo-ionized plasma is consistent with ionization parameters of log(xi) > 2, and when combined with disk size and reasonable assumptions for the plasma density, this suggests illuminating disk luminosities which are over an order of magnitude higher than what is actually observed. That is, we do not directly observe the central emitting X-ray source. The spectral continua are best fit by a flat power law with a high energy cut-off and partial covering absorption (N_H ranging from 5.4-6.3x10^{22} cm^{-2}) with a covering fraction of about 50%. We discuss some implications of our findings with respect to the photo-ionized line emission for the basic properties of the X-ray source.Comment: Submitted to the Astrophysical Journa

Discovery of an X-ray pulsar in the low-mass X-ray binary 2A 1822-371

We report the discovery of 0.59 s X-ray pulsations from the low-mass X-ray binary, 5.57 hr dipping and eclipsing ADC source 2A 1822-371. Pulse arrival time analysis indicates a circular orbit with e < 0.03 (95% confidence) and an asini for the neutron star of 1.006(5) lightseconds, implying a mass function of (2.03+-0.03) x 10^-2 M_sun. The barycentric pulse period was 0.59325(2) s in 1996.270 and 0.59308615(5) s in 1998.205, indicating an average spin up with P_dot/P = (-1.52+-0.02) x 10^-4 yr^-1. For a magnetic field strength of ~1--5 x 10^12 G as derived from the X-ray spectrum the implied intrinsic X-ray luminosity is ~2-4 x 10^37 erg s^-1. The pulse amplitude is low, but increases steeply as a function of energy from a sinusoidal amplitude of 0.25% in 2-5.4 keV to ~3% above 20 keV. We discuss the constraints on the masses of the companion star and the fact that several aspects of the energy spectrum are in qualitative accordance with that of a strongly magnetised neutron star.Comment: 6 pages long, including 4 figures, uses emulateapj5, accepted for ApJL, Replaced figure

The "K-Correction" for Irradiated Emission Lines in LMXBs: Evidence for a Massive Neutron Star in X1822-371 (V691 CrA)

We study the K-correction for the case of emission lines formed in the X-ray illuminated atmosphere of a Roche lobe filling star. We compute the K-correction as function of the mass ratio 'q' and the disc flaring angle 'alpha' using a compact binary code where the companion's Roche lobe is divided into 10^5 resolution elements. We also study the effect of the inclination angle in the results. We apply our model to the case of the neutron star low-mass X-ray binary X1822-371 (V691 CrA), where a K-emission velocity K_em=300 +-8 km/s has been measured by Casares et al. (2003). Our numerical results, combined with previous determination of system parameters, yields 1.61Msun < M_NS < 2.32Msun and 0.44Msun < M_2 < 0.56Msun for the two binary components(i. e. 0.24 < q < 0.27), which provide a compelling evidence for a massive neutron star in this system. We also discuss the implications of these masses into the evolutionary history of the binary.Comment: 6 pages, 5 figures. Accepted for publication in Ap

XTE J1118+480: A Metal-Rich Black Hole Binary in the Galactic Halo

We present medium-resolution optical spectra of the secondary star in the high Galactic latitude black hole X-ray binary XTE J1118+480 and determine the abundance of Mg, Al, Ca, Fe, and Ni in its atmosphere. For all the elements investigated we find supersolar abundances; thus, we reject the hypothesis that the black hole came from the direct collapse of an ancient massive halo star. The compact primary most likely formed in a supernova event of a massive star whose nucleosynthetic products polluted the secondary star. The observed element abundances and their ratios can be explained using a variety of supernova models with a wide range of metallicities. While an explosive origin in the Galactic halo or thick disk cannot be discarded, a metal-rich progenitor is clearly favored by the observed abundance pattern. This suggests that the black hole was produced in the Galactic thin disk with a violent natal kick, propelling the X-ray binary to its current location and orbit.Comment: Accepted for publication as a letter in The Astrophysical Journa

Hydrodynamics of the stream-disk impact in interacting binaries

We use hydrodynamic simulations to provide quantitative estimates of the effects of the impact of the accretion stream on disks in interacting binaries. For low accretion rates, efficient radiative cooling of the hotspot region can occur, and the primary consequence of the stream impact is stream overflow toward smaller disk radii. The stream is well described by a ballistic trajectory, but larger masses of gas are swept up and overflow at smaller, but still highly supersonic, velocities. If cooling is inefficient, overflow still occurs, but there is no coherent stream inward of the disk rim. Qualitatively, the resulting structure appears as a bulge extending downstream along the disk rim. We calculate the mass fraction and velocity of the overflowing component as a function of the important system parameters, and discuss the implications of the results for X-ray observations and doppler tomography of cataclysmic variables, low-mass X-ray binaries and supersoft X-ray sources.Comment: 16 pages, including 8 figures. 1 color figure as a jpeg. ApJ, in pres

Gallstone Obstructive Ileus 3 Years Post-cholecystectomy to a Patient with an Old Ileoileal Anastomosis

The present case is one of gallstone obstructive ileus due to gallstones 3 yr after laparoscopic cholecystectomy. It is interesting because of the sex of the patient, the fact that ileus occurred 3 yr after cholecystectomy and that the localization of the obstruction was an old side-to-side ileoileal anastomosis due to a diverticulectomy following intussusception of Meckels' diverticulum at the age of 3

IP Pegasi: Investigation of the accretion disk structure. Searching evidences for spiral shocks in the quiescent accretion disk

We present the results of spectral investigations of the cataclysmic variable IP Peg in quiescence. Optical spectra obtained on the 6-m telescope at the Special Astrophysical Observatory (Russia), and on the 3.5-m telescope at the German-Spanish Astronomical Center (Calar Alto, Spain), have been analysed by means of Doppler tomography and Phase Modelling Technique. From this analysis we conclude that the quiescent accretion disk of IP Peg has a complex structure. There are also explicit indications of spiral shocks. The Doppler maps and the variations of the peak separation of the emission lines confirm this interpretation. We have detected that all the emission lines show a rather considerable asymmetry of their wings varying with time. The wing asymmetry shows quasi-periodic modulations with a period much shorter than the orbital one. This indicates the presence of an emission source in the binary rotating asynchronously with the binary system. We also have found that the brightness of the bright spot changes considerably during one orbital period. The spot becomes brightest at an inferior conjunction, whereas it is almost invisible when it is located on the distant half of the accretion disk. Probably, this phenomenon is due to an anisotropic radiation of the bright spot and an eclipse of the bright spot by the outer edge of the accretion disk.Comment: 13 pages, 11 figures (= 21 EPS files), accepted for publication in A&