Astrophysics
In this paper we compute detailed evolutionary models providing chemical profiles for white dwarfs having progenitors in the mass range from 1.0 to $7 M_{\sun}$ and we examine the influence of such profiles in the cooling process. The…
We report measurements of the electron temperature at about a dozen locations in the extended emission-line regions of five active (Seyfert and radio) galaxies. Temperatures (T_{[OIII]} and T_{[NII]}) have been determined from both the…
We present an extensive study of lithium abundances in dwarf components of chromospherically active binary stars (CABS). Since most of these binaries have known radii, masses and ages, this kind of data is especially useful for comparisons…
We present a near-infrared cooled grating spectrometer that has been developed at the Arcetri Astrophysical Observatory for the 1.5 m Infrared Telescope at Gornergrat (TIRGO). The spectrometer is equipped with cooled reflective optics and a…
Galaxy cluster mass distribution are potentially useful probes of $\Omega_0$ and the nature of the dark matter. Large clusters will distort the observed shapes of background galaxies through gravitational lensing allowing the measurement of…
We present tests of comparison between our versions of the Fast Multipole Algorithm (FMA) and ``classic'' tree-code to evaluate gravitational forces in particle systems. We have optimized the Greengard's original version of FMA allowing for…
We present a semi-analytical model to test the hypothesis that Ly-alpha QSO absorption lines originate in gaseous halos produced by multiple supernova explosions occurring in Pop III objects in a CDM cosmological scenario hoping to assess…
EUVE satellite spectroscopic observations (SW, MW and LW bands covering 80 - 160, 170 - 350 and 450 A with resolutions 0.5, 1 and 2 A) and photometric observations (Deep Sky Survey, broad-band 70 - 140 A) have been obtained for two contact,…
The metallicities derived from spectroscopic observations of a sample of Starburst Nucleus Galaxies (SBNGs) are compared to those of several other types of galaxies (normal giant galaxies, Irregular and HII galaxies) drawn from the…
We report the discovery of four high-redshift objects (3.3 < z < 4) observed behind the rich cluster CL0939+4713 (Abell 851). One object (DG 433) has a redshift of z=3.3453; the other three objects have redshifts of z\approx 4: A0 at…
The quark surface of a strange star has a very low emissivity for X-ray photons. I find that a small amount of normal matter at the quark surface with temperature in the range $10^7\la T_{_S}} \ll mc^2/k\simeq 6\times 10^9$ K is enough to…
Cluster ellipticals are often thought to be among the oldest galaxies in the universe, with the bulk of their stellar mass formed at early cosmic epochs. I review recent observations of color evolution in early-type cluster galaxies at high…
The diameter - velocity dispersion relation in B, V, and K for three early-type galaxies in the Leo I (M96) group is derived from published photometry and kinematic data. The relations in all three colors have slopes which agree well with…
We report on a series of twenty ~10^5 c/s, 0.125 msec time-resolution RXTE observations of the Z source and low-mass X-ray binary Scorpius X-1. Twin kilohertz quasi-periodic oscillation (QPO) peaks are obvious in nearly all observations. We…
PKS1830-211 is an unusually radio-loud gravitationally lensed quasar. In the radio, the system appears as two compact, dominant features surrounded by relatively extended radio emission which forms an Einstein Ring. As the line of sight to…
The weak radio source LBDS 53W091 is associated with a very faint (R approx. 24.5) red (R-K approx. 5.8) galaxy. Long spectroscopic integrations with the W. M. Keck telescope have provided an absorption-line redshift, z=1.552 +/- 0.002. The…
We present the results of observations of the $\lambda 3130.4$ \AA interstellar absorption line of Be II in the direction of zeta Per. The data were obtained at the Canada-France-Hawaii 3.6m Telescope using the Coud\'e f/4 Gecko…
We report millimeter-wavelength observations of the Sunyaev-Zel'dovich (S-Z) effect in two distant galaxy clusters. A relativistically correct analysis of the S-Z data is combined with the results of X-ray observations to determine the…
We calculate the spectrum of large angle cosmic microwave background (CMB) anisotropies due to quantum fluctuations of the gravitational wave modes in one-bubble open inflation models. We find the bubble-wall fluctuation modes, which had…
We analyze the morphology and dynamics of the galaxies of the Hickson 96 compact group by means of deep CCD images in the B, V and R photometric bands and long-slit spectroscopy. The four galaxies of this spiral rich group show signs of…