46 research outputs found
TAUVEX: status in 2011
We present a short history of the TAUVEX instrument, conceived to provide
multi-band wide-field imaging in the ultraviolet, emphasizing the lack of
sufficient and aggressive support on the part of the different space agencies
that dealt with this basic science mission. First conceived in 1985 and
selected by the Israel Space Agency in 1989 as its first priority payload,
TAUVEX is fast becoming one of the longest-living space project of space
astronomy. After being denied a launch on a national Israeli satellite, and
then not flying on the Spectrum X-Gamma (SRG) international observatory, it was
manifested since 2003 as part of ISRO's GSAT-4 Indian satellite to be launched
in the late 2000s. However, two months before the launch, in February 2010, it
was dismounted from its agreed-upon platform. This proved to be beneficial,
since GSAT-4 and its launcher were lost on April 15 2010 due to the failure of
the carrier rocket's 3rd stage. TAUVEX is now stored in ISRO's clean room in
Bangalore with no firm indications when or on what platform it might be
launched.Comment: Invited contribution presented at the "UV Universe 2010". Accepted
for publication in Astrophysics & Space Scienc
X-Ray Polarization of Solar Flares Measured with Rhessi
The degree of linear polarization in solar flares has not yet been precisely
determined despite multiple attempts to measure it with different missions. The
high energy range in particular has very rarely been explored, due to its
greater instrumental difficulties. We approached the subject using the Reuven
Ramaty High Energy Spectroscopic Imager (RHESSI) satellite to study 6 X-class
and 1 M-class flares in the energy range between 100 keV and 350 keV. Using
RHESSI as a polarimeter requires the application of strict cuts to the event
list in order to extract those photons that are Compton scattered between two
detectors. Our measurements show polarization values between 2% and 54%, with
errors ranging from 10% to 26% in 1 sigma level. In view of the large
uncertainties in both the magnitude and direction of the polarization vector,
the results can only reject source models with extreme properties.Comment: 26 pages, 11 figures, accepted for publication by Solar Physic
Observing broad-absorption line quasars with Spectrum-Rontgen-Gamma
Broad-absorption line quasars are found to have extremely weak soft X-ray emission when compared with other optically selected quasars. In the only example of PHL 5200 for which a detailed X-ray spectrum has been obtained with ASCA, strong absorption in the source appears to be responsible for the lack of soft X-ray emission. Broad-band X-ray observations of a sample of BAL QSOs are proposed with a high throughput mission Spectrum-Röntgen-Gamma (SRG), to find out whether these sources are intrinsically weak over the entire bandwidth of X-rays or only in the soft X-rays due to absorption resulting from the line of sight passing through large column density clouds. Simultaneous UV observations will help to constrain the ionization state of the absorbers, and also improve the overall UV to X-ray continuum measurements in them