March 1999 arXiv papers — page 24

T. J. Galama, M. S. Briggs, R. A. M. J. Wijers, P. M. Vreeswijk

Gamma-ray bursts (GRBs) are thought to result from the interaction of an extremely relativistic outflow interacting with a small amount of material surrounding the site of the explosion. Multi-wavelength observations covering the gamma-ray to radio wavebands allow investigations of this `fireball' model. On 23 January 1999 optical emission was detected w

Christopher W. Mauche

Using ORFEUS-SPAS II FUV spectra, IUE UV spectra, and archival EUVE deep survey photometry, we present a detailed picture of the behavior of the magnetic cataclysmic variable EX Hydrae. Like HUT spectra of this source, the FUV and UV spectra reveal broad emission lines of He II, C II-IV, N III and V, O VI, Si III-IV, and Al III superposed on a continuum whic

Orsola De Marco, Paul A. Crowther

We present a detailed analysis of the planetary nebula M4-18 (G146.7+07.6) and its WC10-type Wolf-Rayet central star, based on high quality optical spectroscopy (WHT/UES, INT/IDS, WIYN/DensPak) and imaging (HST/WFPC2). From a non-LTE model atmosphere analysis of the stellar spectrum, we derive Teff=31kK, log(Mdot/(Msun yr))=-6.05, v_inf=160 km/s and abundanc

Enrico V. Held, Ivo Saviane, Yazan Momany

We have obtained deep BVI CCD photometry of Phoenix, a galaxy considered a transition case between dwarf spheroidal and dwarf irregular galaxies. A comparison of our data with the RGBs of Galactic globular clusters gives a mean metal abundance [Fe/H] = -1.81+/-0.10 dex. The presence of an intrinsic color dispersion in the upper red RGB suggests an abundance

A. Georgakakis, B. Mobasher, L. Cram, A. Hopkins

Using a deep Australia Telescope Compact Array (ATCA) radio survey covering an area of ~3deg^{2} to a 4σsensitivity of \ge 100 \muJy at 1.4GHz, we study the nature of faint radio galaxies. About 50% of the detected radio sources are identified with an optical counterpart revealed by CCD photometry to m_{R}=22.5 mag. Near-infrared (K-band) data are also avail

P. Jean, J. Gomez-Gomar, M. Hernanz, J. Jose

The shield of the INTEGRAL spectrometer provides a large detection area with a wide field-of-view. Calculations have been performed to check whether the temporal analysis of the counting rate of the SPI anticoincidence allows the detection of explosions of novae. The background rate of the shield as well as its response to gamma-ray have been modelled with m

P. Jean, M. Hernanz, J. Gomez-Gomar, J. Jose

Modelisations of galactic 1.275 MeV emission produced by the decay 22Na have been performed for several frequency-spatial distributions of ONe novae. Recent results of nova rates and their distributions in our Galaxy have been used. These modelisations allow to estimate the lower-limit of the 22Na mass ejected per ONe novae detectable with the future spectro

K. Bischoff, W. Kollatschny

We present results of a long-term variability campaign on the Seyfert 1 galaxy Markarian 110. Mkn 110 is a narrow-line Seyfert 1 object hosted in a morphological peculiar galaxy. We monitored the optical continuum and the line intensities as well as their profiles over a time interval of nearly ten years. The continuum and the Balmer lines varied by a factor

M. Revnivtsev, K. Borozdin, A. Emelyanov

An outburst of the X-ray transient source XTE J1806--246 (2S1803--245) has been observed by Rossi X-ray Timing Explorer in April-July 1998. Strong quasi-periodical oscillations (QPO) with a central peak frequency around 9 Hz was detected in one observation of the series performed by PCA/RXTE experiment. X-ray flux from the source during the observation with