Compact X-ray Sources in Nearby Galaxy Nuclei

We have found compact, near-nuclear X-ray sources in 21 (54\%) of a complete sample of 39 nearby face-on spiral and elliptical galaxies with available ROSAT HRI data. ROSAT X-ray luminosities (0.2 $-$ 2.4 keV) of these compact X-ray sources are $\sim$10$^{37}$$-$10$^{40}$ erg~s$^{-1}$. The mean displacement between the location of the compact X-ray source and the optical photometric center of the galaxy is $\sim$390 pc. ASCA spectra of six of the 21 galaxies show the presence of a hard component with relatively steep ($\Gamma \approx$ 2.5) spectral slope. A multicolor disk blackbody plus power-law model fits the data from the spiral galaxies well, suggesting that the X-ray objects in these galaxies may be similar to a black hole candidate (BHC) in its soft (high) state. ASCA data from the elliptical galaxies indicate that hot (kT $\approx$ 0.7 keV) gas dominates the emission. The fact that the spectral slope of the spiral galaxy sources is steeper than in normal type 1 active galactic nuclei (AGNs) and that relatively low absorbing columns (N$_H \approx$ 10$^{21}$ cm$^{-2}$) were found to the power-law component indicates that these objects are somehow geometrically and/or physically different from AGNs in normal active galaxies. The X-ray sources in the spiral galaxies may be BHCs, low-luminosity AGNs, or possibly X-ray luminous supernovae. We estimate the black hole masses of the X-ray sources in the spiral galaxies (if they are BHCs or AGNs) to be $\sim$10$^2$$-$10$^3$ M$_\odot$. The X-ray sources in the elliptical galaxies may be BHCs, AGNs or young X-ray supernova also.Comment: 4 pages, TeX, two postscript figures, to be published in proceedings of 32nd COSPAR Session E1.2 (1998 July 15-17 Nagoya) "The AGN-Normal Galaxy Connection

Supersoft X-Ray Sources in M31

The nearby Andromeda galaxy (M31) has been observed with the ROSAT PSPC in a mosaic of 6 pointings with 25 ksec each. In the paper describing the results on the total sample of detected sources, Supper et al. (1996) also report the positions for 15 supersoft X-ray sources and the blackbody fit results for the brightest of these sources. We report here in more detail on the X-ray spectral characteristics of all these 15 supersoft X-ray sources. Optical multi-colour photometric data obtained in 1990 at the Michigan- Dartmouth-MIT Observatory at Kitt Peak were used originally in the selection process of the supersoft sources, and are the basis for the finding charts given here for most selected X-ray sources.Comment: 8 pages postscript incl. figures, Proc. of Workshop on Supersoft X-Ray Sources, to appear in Lecture Notes in Physics vol. 472 (1996

Vertical distribution of stars and gas in a galactic disk

We study the vertical density distribution of stars and gas (HI and H_2) in a galactic disk which is embedded in a dark matter halo. The new feature of this work is the inclusion of gas, and the gravitational coupling between stars and gas, which has led to a more realistic treatment of a multi-component galactic disk. The gas gravity is shown to be crucially important despite the low gas mass fraction. This approach physically explains the observed scaleheight distribution of all the three disk components, including the long-standing puzzle (Oort 1962) of a constant HI scaleheight observed in the inner Galaxy. The above model is applied to two external galaxies: NGC 891 and NGC 4565, and the stellar disk is shown to be not strictly flat as was long believed but rather it shows a moderate flaring of a factor of about 2 within the optical radius.Comment: 4 pages, 2 figures; to appear in the Proceedings of "Island Universes: Structure and evolution of disk galaxies" (Terschelling, The Netherlands, July 2005), ed. R. de Jon

Graded Parafermions

A graded generalization of the Z_k parafermionic current osp(1|2)/U(1) coset conformal field theory. The structure of the parafermionic highest-weight modules is analyzed and the dimensions of the fields of the theory are determined. A free field realization of the graded parafermionic system is obtained and the structure constants of the current algebra are found. Although the theory is not unitary, it presents good reducibility properties.Comment: 27 pages, LaTeX, 1 eps file. Typos correcte

A One-Parameter Family of Hamiltonian Structures for the KP Hierarchy and a Continuous Deformation of the Nonlinear \W_{\rm KP} Algebra

The KP hierarchy is hamiltonian relative to a one-parameter family of Poisson structures obtained from a generalized Adler map in the space of formal pseudodifferential symbols with noninteger powers. The resulting \W-algebra is a one-parameter deformation of \W_{\rm KP} admitting a central extension for generic values of the parameter, reducing naturally to \W_n for special values of the parameter, and contracting to the centrally extended \W_{1+\infty}, \W_\infty and further truncations. In the classical limit, all algebras in the one-parameter family are equivalent and isomorphic to \w_{\rm KP}. The reduction induced by setting the spin-one field to zero yields a one-parameter deformation of \widehat{\W}_\infty which contracts to a new nonlinear algebra of the \W_\infty-type.Comment: 31 pages, compressed uuencoded .dvi file, BONN-HE-92/20, US-FT-7/92, KUL-TF-92/20. [version just replaced was truncated by some mailer

Catalog of Luminous Supersoft X-ray Sources

This catalog comprises an up-to-date list of luminous (>10^36 erg/s) supersoft X-ray sources. We include in this catalog accreting binary sources of high luminosity which are thought to be in a state of (steady or recurrent) hydrogen burning. Since CAL 83, the prototype, is known to have an ionisation nebula, and further supersoft binaries are expected to also have one, we include also sources associated with very luminous planetary nebulae. Not included are PG 1159 stars which reach similar magnitudes but form a rather distinct class. Excluded are also supersoft active galactic nuclei which reach luminosities up to 10^45 erg/s.Comment: 39 pages postscript, Proc. of Workshop on Supersoft X-Ray Sources, to appear in Lecture Notes in Physics vol. 472 (1996

Autophagy of mucin granules contributes to resolution of airway mucous metaplasia

Abstract Exacerbations of muco-obstructive airway diseases such as COPD and asthma are associated with epithelial changes termed mucous metaplasia (MM). Many molecular pathways triggering MM have been identified; however, the factors that regulate resolution are less well understood. We hypothesized that the autophagy pathway is required for resolution of MM by eliminating excess non-secreted intracellular mucin granules. We found increased intracellular levels of mucins Muc5ac and Muc5b in mice deficient in autophagy regulatory protein, Atg16L1, and that this difference was not due to defects in the known baseline or stimulated mucin secretion pathways. Instead, we found that, in mucous secretory cells, Lc3/Lamp1 vesicles colocalized with mucin granules particularly adjacent to the nucleus, suggesting that some granules were being eliminated in the autophagy pathway rather than secreted. Using a mouse model of MM resolution, we found increased lysosomal proteolytic activity that peaked in the days after mucin production began to decline. In purified lysosomal fractions, Atg16L1-deficient mice had reduced proteolytic degradation of Lc3 and Sqstm1 and persistent accumulation of mucin granules associated with impaired resolution of mucous metaplasia. In normal and COPD derived human airway epithelial cells (AECs), activation of autophagy by mTOR inhibition led to a reduction of intracellular mucin granules in AECs. Our findings indicate that during peak and resolution phases of MM, autophagy activity rather than secretion is required for elimination of some remaining mucin granules. Manipulation of autophagy activation offers a therapeutic target to speed resolution of MM in airway disease exacerbations

UV and X-Ray Monitoring of AG Draconis During the 1994/1995 Outbursts

The recent 1994-1995 active phase of AG Draconis has given us for the first time the opportunity to follow the full X-ray behaviour of a symbiotic star during two successive outbursts and to compare with its quiescence X-ray emission. With \ros observations we have discovered a remarkable decrease of the X-ray flux during both optical maxima, followed by a gradual recovering to the pre-outburst flux. In the UV the events were characterized by a large increase of the emission line and continuum fluxes, comparable to the behaviour of AG Dra during the 1980-81 active phase. The anticorrelation of X-ray/UV flux and optical brightness evolution is shown to very likely be due to a temperature decrease of the hot component. Such a temperature decrease could be produced by an increased mass transfer to the burning compact object, causing it to slowly expand to about twice its original size.Comment: 12 pages postscript incl. figures, Proc. of Workshop on Supersoft X-Ray Sources, to appear in Lecture Notes in Physics vol. 472 (1996

Research of Gravitation in Flat Minkowski Space

In this paper it is introduced and studied an alternative theory of gravitation in flat Minkowski space. Using an antisymmetric tensor, which is analogous to the tensor of electromagnetic field, a non-linear connection is introduced. It is very convenient for studying the perihelion/periastron shift, deflection of the light rays near the Sun and the frame dragging together with geodetic precession, i.e. effects where angles are involved. Although the corresponding results are obtained in rather different way, they are the same as in the General Relativity. The results about the barycenter of two bodies are also the same as in the General Relativity. Comparing the derived equations of motion for the $n$-body problem with the Einstein-Infeld-Hoffmann equations, it is found that they differ from the EIH equations by Lorentz invariant terms of order $c^{-2}$.Comment: 28 page

Arecibo-green bank-LOFAR carbon radio recombination line observations toward cold H I clouds

Interstellar matter and star formatio