A5103073079- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Adaptive optics and wavefront sensing
- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Atmospheric aerosols and clouds
- Atmospheric Ozone and Climate
- History and Developments in Astronomy
- Radio Astronomy Observations and Technology
- Atmospheric chemistry and aerosols
- SAS software applications and methods
- Meteorological Phenomena and Simulations
- Pulsars and Gravitational Waves Research
- CCD and CMOS Imaging Sensors
- Solar and Space Plasma Dynamics
- Calibration and Measurement Techniques
- Impact of Light on Environment and Health
- High-pressure geophysics and materials
- Atmospheric and Environmental Gas Dynamics
- Infrared Target Detection Methodologies
ITM University
2025
Aryabhatta Research Institute of Observational Sciences
2013-2024
Indian Institute of Astrophysics
2014-2024
Udaipur Solar Observatory
1978-2004
European Space Research and Technology Centre
2003
University of Bonn
1991-2001
Indian Space Research Organisation
2001
National Centre for Radio Astrophysics
1995
Australian Astronomical Observatory
1990
Royal Observatory
1985-1988
Collocated measurements of the mass concentrations aerosol black carbon (BC) and composite aerosols near surface were carried out along with spectral optical depths (AODs) from a high‐altitude station, Manora Peak in central Himalayas, during comprehensive field campaign December 2004. Despite being pristine location Shivalik Ranges Himalayas having monthly mean AOD (at 500 nm) 0.059 ± 0.033 (typical to this site), total suspended particulate (TSP) concentration was range 15–40 μg m −3 (mean...
Abstract Simultaneous in situ measurements of ozone, CO, and NO y have been made for the first time at a high altitude site Nainital (29.37°N, 79.45°E, 1958 m above mean sea level) central Himalayas during 2009–2011. CO levels discern slight enhancements daytime, unlike ozone. The diurnal patterns are attributed mainly to dynamical processes including vertical winds boundary layer evolution. Springtime higher ozone (57.5 ± 12.6 ppbv), (215.2 147 (1918 1769.3 parts per trillion by volume...
Context. The solar-age open cluster M 67 (C0847+120, NGC 2682) is a touchstone in studies of the old Galactic disk. Despite its outstanding role, census membership for at fainter magnitudes and their properties are not well-established.
We present densely sampled UBVRI/griz photometric and low-resolution (6–10 Å) optical spectroscopic observations from 4 to 270 d after explosion of a newly discovered Type II SN 2012aw in nearby (∼9.9 Mpc) galaxy M95. The light-curve characteristics apparent magnitudes, colours, bolometric luminosity the presence evolution prominent spectral features are found have striking similarity with archetypal IIP SNe 1999em, 1999gi 2004et. early time clearly detect minima light curve V, R I bands...
We present, for the first time, spectral behavior of aerosol optical depths (AODs) over Manora Peak, Nainital, located at an altitude ∼2 km in Shivalik ranges central Himalayas. The observations were carried out using a multiwavelength solar radiometer during January to December 2002. main results study are extremely low AODs winter, remarkable increase high values summer, and distinct change dependencies from relatively steeper spectra winter shallower ones summer. A comparison total...
In this paper we study the evolution of core and corona nine open clusters using projected radial density profiles derived from homogeneous CCD photometric data obtained with 105 cm Kiso Schmidt telescope. The age galactocentric distance target vary 16 to 2000 Myr 9 10.8 kpc, respectively. Barring Be 62, which is a young cluster, other show uniform reddening across cluster region. in 62 varies E(B - V)min = 0.70 mag V)max 1.00 mag. coronae six present sample are found be elongated; however,...
Aims. The Whole Earth Blazar Telescope (WEBT) consortium has been monitoring the blazar 3C 454.3 from radio to optical bands since 2004 study its emission variability properties.
A dust storm blew through the Thar Desert on 12 June 2006, which has significantly influenced aerosol physical and optical properties over central Himalayas (Nainital, 29.4°N; 79.5°E, 1958 m amsl) 13 2006. Aerosol number concentrations in coarse giant modes 2006 are found to be five (26 × 10 6 −3 ) ten (17.2 3 times higher compared their respective monthly mean values. depth values also showed two four increase, particularly at longer wavelengths suggesting increase of particles. This is...
Abstract As part of TIGERZ campaign, latitudinal variation aerosol optical properties was analyzed over Indo‐Gangetic Plains (IGP) to central Himalayas during premonsoon 2008 and 2009. Measurements depth (AOD) were performed using Aerosol Robotic Network Sun photometer at four sites with different environments. The AOD increases from Nainital located in Kanpur IGP region. Further, size varies spatially dominance coarse‐mode aerosols compared fine‐mode dominated Nainital. Spectral...
Context. The international whole earth blazar telescope (WEBT) consortium planned and carried out three days of intensive micro-variability observations S5 0716+714 from February 22, 2009 to 25, 2009. This object was chosen due its bright apparent magnitude range, high declination, very large duty cycle for micro-variations. Aims. We report here on the long continuous optical light curve obtained during multi-site observing campaign which Blazar showed almost constant variability over a 0.5...
We present the low-resolution spectroscopic and UBVRI broad-band photometric investigations of Type IIb supernova 2011fu, discovered in UGC 01626.The follow-up this event has been initiated a few days after explosion covers period about 175 days.The early-phase light curve shows rise followed by steep decay all bands shares properties very similar to that seen case SN 1993J, with possible detection adiabatic cooling phase.Modelling quasi-bolometric suggests progenitor had an extended (∼ 1 ×...
Broad-band (ultraviolet to near-infrared) observations of the intense gamma ray burst GRB 990123 started ∼8.5 hours after event and continued until 18 February 1999. When combined with other data, in particular from Robotic Telescope Transient Source Experiment (ROTSE) Hubble Space (HST), evidence emerges for a smoothly declining light curve, suggesting some color dependence that could be related cooling break passing ultraviolet-optical band at about 1 day high-energy event. The steeper...
Observations of the extraordinarily bright optical afterglow (OA) GRB 991208 started 2.1 d after event. The flux decay constant OA in R-band is -2.30 +/- 0.07 up to 5 d, which very likely due jet effect, and that it followed by a much steeper with -3.2 0.2, fastest one ever seen OA. A negative detection several all-sky films taken simultaneously event implies either previous additional break prior 2 occurrence (as expected from effect). existence second might indicate steepening electron...
view Abstract Citations (103) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Steps toward Determination of the Size and Structure Broad-Line Region in Active Galactic Nuclei. VI. Variability NGC 3783 from Ground-based Data Stirpe, G. M. ; Winge, C. Altieri, B. Alloin, D. Aguero, E. L. Anupama, Ashley, R. Bertram, Calderon, J. H. Catchpole, Corradi, Covino, Dottori, A. Feast, W. Ghosh, K. Hutton, Gil Glass, I. S. Grebel, Jorda, Koen, Laney,...
We report the results of multiband optical photometric monitoring two well-known blazars, S5 0716+714 and BL Lacertae, carried out during 1996 2000–01 with an aim to study variations on time-scales ranging from minutes hours longer. The light curves were derived relative comparison stars present CCD frames. Night-to-night intensity ≥0.1 mag observed in a campaign about 2 weeks 1996. A good correlation between different bands was found for both inter-night intra-night observations. In all,...
We present X-ray, broad band optical and low frequency radio observations of the bright type IIP supernova SN 2004et. The \cxo observed at three epochs, coverage spans a period $\sim$ 470 days since explosion. X-ray emission softens with time, we characterise luminosity evolution as $\Lx \propto t^{-0.4}$. use to estimate mass-loss rate for progenitor star $\sim \ee{2}{-6} M_\odot \mathrm{yr}^{-1}$. light curve shows pronounced plateau lasting about 110 days. Temporal photospheric radius...
We present a comprehensive multiwavelength study of the star-forming region NGC 1893 to explore effects massive stars on low-mass star formation. Using near-infrared colours, slitless spectroscopy and narrow-band Hα photometry in cluster we have identified candidate young stellar objects (YSOs) distributed pattern from one nearby nebulae Sim 129. The V, (V−I) colour–magnitude diagram YSOs indicates that majority these ages between 1 5 Myr. spread may indicate non-coeval formation cluster....
<i>Context. <i/>BL Lacertae is the prototype of blazar subclass named after it. Yet, it has occasionally shown a peculiar behaviour that questioned simple interpretation its broad-band emission in terms synchrotron plus self-Compton (SSC) radiation.<i>Aims. <i/>In 2007–2008 observing season we carried out new multiwavelength campaign Whole Earth Blazar Telescope (WEBT) on BL Lacertae, involving three pointings by XMM-Newton satellite July and December 2007, January 2008, to study properties,...
We present optical photometric and low-resolution spectroscopic observations of the Type II plateau supernova (SN) 2008in, which occurred in outskirts nearly face-on spiral galaxy M 61. Photometric data X-rays, ultraviolet near-infrared bands have been used to characterize this event. The SN field was imaged with ROTSE-IIIb telescope about seven days before explosion. This allowed us constrain epoch shock breakout JD = 2454825.6. duration phase, as derived from monitoring, ~ 98 days. spectra...
Relative proper motions (PMs) and cluster membership probabilities (Pμ) were derived for ∼2500 stars in the field of open star NGC 3766. The was observed B V broad-band filters at two epochs separated by ∼6 yr using a wide-field imager mounted on WFI@ESO 2.2-m telescope. All CCD frames reduced astrometric techniques described Anderson et al. PM rms error brighter than ∼ 15 mag is 2.0 mas yr−1, but it gradually increases up to ∼4 yr−1 20 mag. Using data, region cluster. They indicate that one...