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2 article(s) in total. 8 co-authors. Median position in authors list is 4,0.

[1]  oai:arXiv.org:astro-ph/0005236  [pdf] - 36008
The All Sky Automated Survey. A Catalog of almost 3900 variable stars
Comments: 14 pages, 6 figures, 4 tables
Submitted: 2000-05-11
Results of the first two years of observations using the All Sky Automated Survey prototype camera are presented. More than 140 000 stars in 50 Selected Fields covering 300 sq. degrees were monitored each clear night in the I-band resulting in the ASAS Photometric I-band Catalog containing over 50 x 10^6 individual measurements. Nightly monitoring over 100 standard stars confirms that most of our data remains within sigma_I=0.03 of the standard I system. Search for the stars varying on the time scales longer than a few days revealed almost 4000 variables (mostly irregular, pulsating and binaries) brighter than 13 mag. Only 155 of them are known variables included in GCVS, 56 were observed by Hipparcos satellite (46 were marked as variable). Among the stars brighter than I ~ 7.5 (which are saturated on our frames) we have found about 50 variables (12 are in GCVS, 6 other in Hipparcos (Perryman etal 1997) catalog). Because of the large volume of the data we present here only selected tables and light-curves, but the complete ASAS Catalog of Variable Stars (currently divided into Periodic and Miscellaneous sections) and all photometric data are available on the Internet http://www.astrouw.edu.pl/~gp/asas/asas.html or http://archive.princeton.edu/~asas/
[2]  oai:arXiv.org:astro-ph/9910400  [pdf] - 108954
Properties of Dust Grains in Planetary Nebulae - I. The Ionized Region of NGC 6445
Comments: 36 pages, 8 tables, 7 figures, accepted for publication in ApJ
Submitted: 1999-10-21
In this paper we study new infrared spectra of the evolved planetary nebula NGC 6445 obtained with ISO. These data show that the thermal emission from the grains is very cool and has a low flux compared to H beta. A model of the ionized region is constructed, using the photo-ionization code CLOUDY 90.05. Based on this model, we show from depletions in the gas phase elements that little grain destruction can have occurred in the ionized region of NGC 6445. We also argue that dust-gas separation in the nebula is not plausible. The most likely conclusion is that grains are residing inside the ionized region of NGC 6445 and that the low temperature and flux of the grain emission are caused by the low luminosity of the central star and the low optical depth of the grains. This implies that the bulk of the silicon-bearing grains in this nebula were able to survive exposure to hard UV photons for at least several thousands of years, contradicting previously published results. A comparison between optical and infrared diagnostic line ratios gives a marginal indication for the presence of a t^2-effect in the nebula. However, the evidence is not convincing and other explanations for the discrepancy are also plausible. The off-source spectrum taken with ISO-LWS clearly shows the presence of a warm cirrus component with a temperature of 24 K as well as a very cold component with a temperature of 7 K. Since our observation encompasses only a small region of the sky, it is not clear how extended the 7 K component is and whether it contributed significantly to the FIRAS spectrum taken by COBE. Because our line of sight is in the galactic plane, the very cold component could be a starless core.