Search Publications
Stellar population gradient in lenticular galaxies: NGC 1023, NGC 3115 and NGC 4203
Bassin, M.; Bonatto, Ch.
We investigate the stellar population content in the lenticular galaxies NGC 1023, NGC 3115 and NGC 4203 applying a population synthesis method based on a seven component spectral basis with different ages - 2.5*E6, 10*E6, 25*E6, 75*E6, 200*E6, 1.2*E9 and older than 1010 …
Simultaneous observations of radio wave frequency and intensity fluctuations for estimates of solar wind speed
Bird, M. K.; Efimov, A. I.; Chashei, I. V. +1 more
A new method is developed for solar wind speed measurements based on simultaneous observations of radio wave temporal intensity and frequency fluctuations. An estimate of the solar wind convection velocity is obtained from a combination of the frequency (Doppler) fluctuation spectral power at low fluctuating frequency and the power in the flat par…
Tests and constraints on theories of galaxy formation and evolution
Thompson, Rodger I.
Tests and constraints on current theories of galaxy formation and evolution are presented. They are derived from observations of the Northern Hubble Deep Field with WFPC2 and NICMOS. Photometric redshifts, extinctions and spectral energy distributions are calculated for all objects in the field. The tests and constraints are derived from the outpu…
XMM-Newton observations of absorption features towards PKS 2155-304
Maraschi, L.; Tavecchio, F.; Treves, A. +2 more
We present XMM-Newton grating spectra of the bright BL Lac object PKS 2155-304 taken in November 2000. Various absorption features are detected in the range 5-38 Å. The results are compared with those recently obtained with Chandra gratings [ApJ 573 (2002) 157; Nature, 421 (2003) 719]. We discuss whether the absorption occurs at the source (in the…
JEM-X background models
Oxborrow, C. A.; Huovelin, J.; Maisala, S. +4 more
Background and determination of its components for the JEM-X X-ray telescope on INTEGRAL are discussed. A part of the first background observations by JEM-X are analysed and results are compared to predictions. The observations are based on extensive imaging of background near the Crab Nebula on revolution 41 of INTEGRAL. Total observing time used…
Spectroscopy of early-type star candidates in M 33 and NGC 6822. II
Bianchi, L.; Scuderi, S.; Catanzaro, G. +1 more
We present ground-based spectra of early-type star candidates in the Local Group galaxies M 33 and NGC 6822 taken at the 4.2 m William Herschel Telescope (La Palma, Spain). Photospheric parameters Teff and log g were derived by LTE modeling of the Balmer lines. When possible, mass-loss rates were calculated from the Halpha p…
Temperature Measurements in the Solar Transition Region Using N III Line Intensity Ratios
Bhatia, A. K.; Doschek, G. A.; Feldman, U. +2 more
UV emission from B-like N and O ions offers a rather rare opportunity for recording spectral lines in a narrow wavelength range that can potentially be used to derive temperatures relevant to the solar transition region. In these ions, the line intensity ratios of the type (2s2p2-2p3)/(2s22p-2s2p2) are v…
Latitudinal extent of large-scale structures in the solar wind
McComas, D. J.; Riley, P.; Elliott, H. A.
Comparison of solar wind observations from the ACE spacecraft, in the ecliptic plane at ~ 1 AU, and the Ulysses spacecraft as it orbits over the Sun's poles, provides valuable information about the latitudinal extent and variation of solar wind structures in the heliosphere. While qualitative comparisons can be made using average properties observ…
XESS: An XMM Extended Source Survey
Saxton, R. D.; Neumann, D. M.; Denby, M. +1 more
The XMM-Newton SSC serendipitous cluster survey
Elvis, M.; Watson, M. G.; Schwope, A. +2 more