13 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
Multi-color Optical Variability of the TeV Blazar Mrk 501 in the Low-State
We report results based on the monitoring of the BL Lac object Mrk 501 in the
optical (B, V and R) passbands from March to May 2000. Observations spread over
12 nights were carried out using 1.2 meter Mount Abu Telescope, India and 61 cm
Telescope at Sobaeksan Astronomy Observatory, South Korea. The aim is to study
the intra-day variability (IDV), short term variability and color variability
in the low state of the source. We have detected flux variation of 0.05 mag in
the R-band in time scale of 15 min in one night. In the B and V passbands, we
have less data points and it is difficult to infer any IDVs. Short term flux
variations are also observed in the V and R bands during the observing run. No
significant variation in color (BR) has been detected but (VR) shows
variation during the present observing run.
Assuming the shortest observed time scale of variability (15 min) to
represent the disk instability or pulsation at a distance of 5 Schwarschild
radii from the black hole (BH), mass of the central BH is estimated 1.20
10.Comment: 4 figures, 4 tables, Accepted for publication in New Astronom