Measurement of Mass and Spin of Black Holes with QPOs

There are now four low mass X-ray binaries with black holes which show twin resonant-like HFQPOs. Similar QPOs might have been found in Sgr A*. I review the power spectral density distributions of the three X-ray flares and the six NIR flares published for Sgr A* so far, in order to look for more similarities than just the frequencies between the microquasar black holes and Sgr A*. The three X-ray flares of Sgr A* are re-analysed in an identical way and white noise probabilities from their power density distributions are given for the periods reported around 1100 s. Progress of the resonant theory using the anomalous orbital velocity effect is summarized.Comment: 7 pages, talk given at the 2007 Frascati workshop, acc. for publication in the Chin. J. Astron. Astrophy

X-rays from Supernova Remnants

A summary of X-ray observations of supernova remnants is presented including the explosion fragment A of the Vela SNR, Tycho, N132D, RX J0852-4622, the Crab Nebula and the 'bulls eye', and SN 1987A, high-lighting the progress made with Chandra and XMM-Newton and touching upon the questions which arise from these observations and which might inspire future research.Comment: 13 pages, 18 figures. To appear in the Proceedings of the 270. WE-Heraeus Seminar on Neutron Stars, Pulsars and Supernova Remnants, Jan. 21-25, 2002, Physikzentrum Bad Honnef, eds W. Becker, H. Lesch & J. Truemper. Proceedings are available as MPE-Report 27

Temporal Variability of the X-ray Emission of the Crab Nebula Torus

We have analyzed five ROSAT HRI images of the Crab Nebula spanning the years 1991 to 1997 and have found significant changes in the emission structure of the X-ray torus surrounding the pulsar. Certain regions increase in brightness by about 20% over the six years, while others show decreases in surface brightness. The origin of these changes is unclear, but a possible explanation is that the bulk velocity of the synchrotron radiating electrons has decreased on the order of 20% as well.Comment: 15 pages plus 6 figures, figure 1 and figure 6 are in color, to appear in The Astrophysical Journal, Jan 1, 1999, Vol. 510, #

XMM-Newton observation of SN1993J in M81

In April 2001 SN1993J was observed with both the PN and MOS cameras of the XMM-Newton observatory, resulting in about 7. x 10^4 s of acceptable observation time. Fit results with both the PN and MOS2 camera spectra studying different spectral models are presented. The spectra are best fitted in the energy range between 0.3 and 11 keV by a 2-component thermal model with temperatures of kT_1 = 0.34+-0.04 keV and kT_2 = 6.54+-4 keV, adopting ionization equilibrium. A fit with a shock model also provides acceptable results. Combining the XMM-Newton data with former X-ray observations of the supernova, we discuss the general trend of L_x propto t^{-0.30} and the bump of the X-ray light curve as well as former and recent spectral results in the light of the standard SN model as first proposed by Chevalier in 1982.Comment: 7 pages, 3 figure

Spectroscopic Study of the Vela-Shrapnel

Several shrapnels have been detected in the vicinity of Vela SNR by the ROSAT all-sky survey. We present here the spectral properties of shrapnel `A' observed with the ASCA satellite. A prominent Si-K emission line with relatively weak emission lines from other elements have been detected, revealing that the relative abundance of Si is a few ten-times higher than those of other elements. Combining with the ROSAT PSPC results, we obtained the electron temperature, $kT_{\rm e}$, to be $0.33 \pm 0.01$ keV. The total mass of shrapnel `A' is estimated to be $\sim 0.01 M_\odot$. If it is an ejecta of a supernova explosion, the interstellar matter (ISM) would be swept up in the leading edge while the ejecta material would be peeled off in the trailing edge, which should be confirmed by future observations.Comment: 19pages, 5 figures, 1 table; Accepted for Publications of the Astronomical Society of Japa

In-orbit performance of the XMM-Newton X-ray telescopes: images and spectra

The performance of the three X-ray telescopes on-board of XMM-Newton is evaluated addressing imaging characteristics and effective collecting area. The agreement with ground calibration data is excellent. The analysis of images and spectra of cosmic X-ray sources, emphazising supernova and supernova remnants, prooves that the telescopes are even better than originally required.Comment: 13 pages, 20 jpg figures, for SPIE Proc. 4496, paper 0

Mass and Angular Momentum of Black Holes: An Overlooked Effect of General Relativity Applied to the Galactic Center Black Hole Sgr A*

I report the discovery of a new effect of General Relativity which is important to understand very rapidly rotating (Kerr) black holes. The orbital velocity of a test particle is no longer a monotonic function of the orbit radius when the spin of the black hole is >0.9953, but displays a local minimum-maximum structure for radii smaller than 1.8 gravitational radii. There the rate of change of the orbital velocity per radius unit equals the radial epicyclic frequency and is exactly one third of the polar epicyclic frequency, suggesting a 3:1 resonant oscillatory motion of the particle. If associated with the observed quasi-periods - including the most recent 2005/2006 data - the mass of the supermassive black hole Sgr A* in the centre of the our Galaxy is determined to 3.3 million solar masses and the spin is 0.99616.Comment: 11 pages, 5 figures, updated version of a talk given at the 2005 Frascati Workshop, Vulcano, Italy, May 23 - 2

X-ray Observations of Neutron Stars and Pulsars: First Results from XMM-Newton

The X-ray Multi-Mirror Mission XMM-Newton is ESA's largest observatory so far; it is dedicated to explore the Universe in the 0.2 - 15 keV X-ray band of the electromagnetic spectrum. Because of its large collecting area very faint sources not accessible before can be observed and it is therefore the long awaited instrument to study young pulsars and neutron stars in supernova remnants, cooling neutron stars and millisecond pulsars at X-ray energies. The high throughput of the instruments, which all are operated simultaneously, provide high resolution spectral, spatial and temporal information from a source during a single observation and make XMM-Newton unique and best suited for pulsar studies. In this article we briefly describe the instrument capabilities useful for pulsar observations and provide information on the timing accuracy on the relative and absolute scale. We further provide scientific results from observations of the Crab-pulsar, PSR J1617-5055 near RCW 103, of young neutron stars in the supernova remnants RX J0852-4622, Puppis-A and RCW 103 including 1E161348-5055.1 which is identified to be the second binary in a supernova remnant. In addition we report on observations of the cooling neutron star PSR B1055-52 and on the millisecond pulsar PSR J0030+0451 which all were observed by XMM-Newton during the first two years of scientific operation.Comment: 23 pages, 22 figures, 4 tables. To appear in the Proceedings of the 270.WE-Heraeus Seminar on Neutron Stars, Pulsars and Supernova Remnants, Jan 21-25, Physikzentrum Bad Honnef, eds W. Becker, H. Lesch & J. Truemper. Proceedings available as MPE-Report 278. The paper with high resolution images can be obtained from ftp://ftp.xray.mpe.mpg.de/people/web/Becker_Aschenbach.pd

Intestinal epithelial responses to Salmonella enterica serovar Enteritidis: Effects on intestinal permeability and ion transport

Salmonella infection of chickens that leads to potential human foodborne salmonellosis continues to be a major concern. Chickens serve as carriers but, in contrast to humans, rarely show any clinical signs including diarrhea. The present investigations aimed to elucidate whether the absence of diarrhea during acute Salmonella enterica serovar Enteritidis (Salmonella Enteritidis) infection may be linked to specific changes in the electrophysiological properties of the chicken gut. Immediately after slaughter, intestinal pieces of the mid-jejunum and cecum of either commercial broiler or specific pathogen-free (SPF) chickens were mounted in Ussing chambers in 2 separate experimental series. Living Salmonella Enteritidis (3 × 109) or Salmonella Enteritidis endotoxin (20 mg/L), or both, were added to the mucosal side for 1 h. In both experimental series, the Salmonella infection decreased the trans-epithelial ion conductance Gt (P < 0.05). In the jejunum of SPF chickens, there was also a marked decrease in net charge transfer across the epithelium, evidenced by decreased short-circuit current (Isc, P < 0.05). Interestingly, the mucosal application of Salmonella endotoxin to the epithelial preparations from jejunum and cecum of SPF chicken had an effect similar to living bacteria. However, the endotoxin had no additional effect on the intestinal function in the presence of bacteria. The decreasing effect of Salmonella and or its endotoxin on Gt could be partly reversed by serosal addition of histamine. To our knowledge, this is the first study to address the functional response of native intestinal epithelium of chicken to an in vitro Salmonella infection. For the first time, it can be reported that intestinal ion permeability of chicken decreases acutely by the presence of Salmonella. This type of response could counteract ion and fluid secretion and may thus, at least in part, explain why chickens do not develop overt diarrhea after Salmonella infection