October 1997 arXiv papers — page 20

M. Catelan, A. V. Sweigart, J. Borissova, N. Spassova

Paper I: "RR Lyrae Variables in Globular Clusters and the Second-Parameter Phenomenon" Authors: M. Catelan, A. V. Sweigart, J. Borissova Abstract: We propose to use RR Lyrae variables in globular clusters to probe the origin of the second-parameter phenomenon. Paper II: "New Possible Variables in the Outer-Halo Globular Cluster Palomar 3" Aut

M. van der Klis

This paper provides a review of the kilohertz quasi-periodic oscillations in low-mass X-ray binaries recently discovered with NASA's Rossi X-ray Timing Explorer. It contains two tables that are up to date up to October 1st, 1997 with information about all kHz QPO phenomena so far reported. In the most straightforward interpretations, kHz QPO provide dire

Julianne J. Dalcanton

Both the detection of galaxies and the derivation of the luminosity function depend upon isophotal magnitudes, implicitly in the first case, and explicitly in the latter. However, unlike perfect point sources, the fraction of a galaxy's light contained within the limiting isophote is a function of redshift, due to the combined effects of the point spread

José A. Muñoz, Emilio E. Falco, Christopher S. Kochanek, Joseph Lehár

We report the discovery of a binary quasar, MGC2214+3550 A,B, whose components have similar optical spectra at a redshift z=0.88. The quasars are separated on the sky by 3.0", and have a magnitude difference of Delta(m_I)=0.5 mag. The VLA radio map at 3.6 cm shows a single 47mJy radio source with a core-jet morphology that is coincident with the brighter

Rudy Wijnands, Jeroen Homan, Michiel van der Klis, Mariano Mendez

We observed the low-mass X-ray binary and Z source GX 17+2 with the Rossi X-ray Timing Explorer during 6-8 Feb 1997, 1-4 Apr 1997, and 26-27 Jul 1997. The X-ray color-color diagram shows a clear Z track. Two simultaneous kHz quasi-periodic oscillations (QPOs) are present in each observation, whose frequencies are well correlated with the position of the sour

A. D'Ercole, L. Ciotti

A recent analysis of the "Einstein" sample of early-type galaxies has revealed that at any fixed optical luminosity Lb S0 galaxies have lower mean X-ray luminosity Lx per unit Lb than ellipticals. Following a previous analytical investigation of this problem (Ciotti & Pellegrini 1996), we have performed 2D numerical simulations of the gas flows insid

Romain Teyssier, Jean-Pierre CHIEZE, Jean-Michel Alimi

We investigate the role of radiative cooling within the core of large X-ray clusters using multi-phase hydrodynamics. We developed for that purpose a spherically symmetric hydrodynamical code, coupled to a "fluid model" that describes accurately the dark matter component. Cooling is included using a self-consistent multi-phase approach, leading to &#

G. Dubus, P. A. Charles, K. S. Long, P. J. Hakala

With an X-ray luminosity of about 10^39 erg/s, the source X-8 coincident with the optical center of M33 is the most luminous X-ray source in the Local Group. However, its nature remains a mystery. We present here new and archival ROSAT observations of X-8 spread over 6 years which show variability and a ~ 106-d periodicity. This implies that (most of) the em

Claude Chevalier, Sergio A. Ilovaisky

We present results on parallaxes, magnitudes and proper motions for 17 optically identified massive X-ray binaries (MXRB) which were observed during the Hipparcos astrometry mission. This sample includes the sources detected in the medium-energy range (2-10 keV) having optical counterparts brighter than V=12. We compare the Hipparcos results with ground-base

Kathryn V. Johnston

We develop a semi-analytic method for determining the phase-space population of tidal debris along the orbit of a disrupting satellite galaxy and illustrate its use with a number of applications. We use this method to analyze Zhao's proposal that the microlensing events towards the Large Magellanic Cloud (LMC) might be explained by an appropriately place

V. Kolokotronis, M. Plionis, P. Coles, S. Borgani

We investigate the sampling and dipole convergence properties of flux-limited samples of mock X-ray clusters in relation to their underlying ``parent'' cluster distribution. To this purpose, we resort to numerical simulations of the cluster distribution and extract samples resembling the main observational features of X-ray selected cluster samples.

M. Gabriel

We show that, if solar 5 min. oscillations are excited by convection in the upper layers of the convective envelope, it is impossible to explain the opposite line asymmetries observed in the velocity and intensity spectra with assumptions on the dissipations which reduce the problem to a second order one. The interpretation of that observation requires to so

D. Thomas, L. Greggio, R. Bender

We analyse two recent computations of type II supernova nucleosynthesis by Woosley & Weaver (1995, WW95) and Thielemann, Nomoto, & Hashimoto (1996, TNH96), focusing on the ability to reproduce the observed [Mg/Fe]-ratios in various galaxy types. We show that the yields of oxygen and total metallicity are in good agreement. However, TNH96-models produce more

David A. Buote, Claude R. Canizares

We review the theory of how the shapes of the X-ray isophotes probe both the shape and radial distribution of gravitating matter in elliptical galaxies in a way that is more robust than the traditional spherical approach. We summarize and update the previous analyses of X-ray observations of NGC 720 and NGC 1332 and describe preliminary results for NGC 3923.

Mart'in Sombra

We present bounds for the sparseness and for the degrees of the polynomials in the Nullstellensatz. Our bounds depend mainly on the unmixed volume of the input polynomial system. The degree bounds can substantially improve the known ones when this polynomial system is sparse, and they are, in the worst case, simply exponential in terms of the number of varia

Jonathan Fine

This paper defines, for each convex polytope $Δ$, a family $H_wΔ$ of vector spaces. The definition uses a combination of linear algebra and combinatorics. When what is called exact calculation holds, the dimension $h_wΔ$ of $H_wΔ$ is a linear function of the flag vector $fΔ$. It is expected that the $H_wΔ$ are examples, for toric varieties, of the new topolo

Wentian Li

This commentary discusses a recently proposed measure of heterogeneity of DNA sequences and compares with the measures of complexity.