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An infrared study of Be stars based on ISO SWS01 spectra
Zhang, Pin; Fu, Zai-Qi
The Infrared Space Observatory (ISO) Short-Wavelength Spectrometer (SWS) spectra of 10 Be stars are presented. It can be seen that the Be stars show a diversity in their ISO SWS01 spectral classifications by Kraemer et al., from naked stars, stars associated with dust, stars with warm dust shells, stars with cool dust shells to very red sources. I…
Evolution of dwarf galaxies in the Centaurus A group
Crnojević, D.; Grebel, E. K.; Koch, A.
The study of (dwarf) galaxies in nearby groups is one among the most powerful tools that can be used to investigate galaxy evolution, chemical enrichment and environmental effects on these objects. The Centaurus A group (at a distance of ∼ 4 Mpc) is dynamically evolved and contains about 30 dwarf companions of different morphologies and stellar co…
INTEGRAL and Swift/XRT observations of IGR J19405-3016
Torres, D. F.; Zhang, S.; Chen, Y. P. +3 more
Aims: IGR J19405-3016 is reported in the 3rd IBIS catalog as one of its lowest significance sources (~4.6σ under an exposure of about 371 ks). This leads to a caveat in multi-wavelength studies, although the source was identified in the optical as a Seyfert 1. The currently available INTEGRAL data on the source have increased to an exposure time o…
Two computer programs for studying stellar evolution
Kosmas, T. S.; Liolios, T. E.; Karathanou, G. I. +1 more
Two FORTRAN programs are presented which plot the Hertzsprung-Russell diagram and the temporal evolution of such stellar quantities as: central and photospheric isotopic abundances, central densities and temperatures, luminocities, effective temperatures and photospheric radii for a wide range of stellar masses. The programs, which are modificatio…
Accurate Analytical and Statistical Approaches to Reduce O-C Discrepancies in the Precessional Parameters
Marco, F. J.; Martínez, M. J.; López, J. A.
The Hipparcos catalog provides a reference frame at optical wavelengths for the new International Celestial Reference System (ICRS). This new reference system was adopted following the resolution agreed at the 23rd IAU General Assembly held in Kyoto in 1997. Differences in the Hipparcos system of proper motions and the previous materialization of …
XMM Observations of Two Quadrupolar Outflows
Simon, Theodore
X-ray images of two small dark clouds, L1455 and L723, have been obtained with the EPIC cameras on board the XMM-Newton telescope. Both regions contain multiple independent but overlapping bipolar flows in high-velocity CO, a collection of Herbig-Haro objects, and a number of filaments and knots of H2 emission. The field of view in each…
Cluster spacecraft observations of a ULF wave enhanced by Space Plasma Exploration by Active Radar (SPEAR)
Yeoman, T. K.; Fear, R. C.; Badman, S. V. +3 more
Space Plasma Exploration by Active Radar (SPEAR) is a high-latitude ionospheric heating facility capable of exciting ULF waves on local magnetic field lines. We examine an interval from 1 February 2006 when SPEAR was transmitting a 1 Hz modulation signal with a 10 min on-off cycle. Ground magnetometer data indicated that SPEAR modulated currents i…
Peculiarities of long-wave radio bursts from solar flares preceding strong geomagnetic storms
Yermolaev, Yu. I.; Kudela, K.; Prokudina, V. S. +2 more
Radio bursts in the frequency range of 100-1500 kHz, recorded in 1997-2000 on the INTERBALL-1 satellite during the solar flares preceding the strong geomagnetic storms with D st < -100 nT, are analyzed in this paper. The observed long-wave III-type radio bursts of solar origin at frequencies of 1460 and 780 kHz were characterized b…
Observational Study of a Peculiar Solar Limb Event Occurred on 11 January 2002
Li, Hui; You, Jianqi
On 11 January 2002, using the Multi-channel Infrared Solar Spectrograph (MISS) at the Purple Mountain Observatory (PMO), we obtained Hα, Ca II 8542 Å and He I 10 830 Å spectra and slit-jaw Hα images of a peculiar solar limb event. A close resemblance of its intensity to that of a small flare and the GOES X-ray flux indicates that it was an active …
Dwarf spheroidal galaxies in the M81 group of galaxies
Grebel, E. K.; Koch, A.; Lianou, S.
We study the properties of the dwarf galaxy population in the nearby interacting M81 group of galaxies. In particular, we are deriving the metallicity distribution functions, the ages and the star formation histories of these dwarf galaxies based on data from the Hubble Space Telescope's Advanced Camera for Surveys and the Sloan Digital Sky Survey…