R
Ram Sagar
Researcher at Aryabhatta Research Institute of Observational Sciences
Publications - 73
Citations - 3472
Ram Sagar is an academic researcher from Aryabhatta Research Institute of Observational Sciences. The author has contributed to research in topics: Open cluster & Stars. The author has an hindex of 32, co-authored 65 publications receiving 3288 citations. Previous affiliations of Ram Sagar include Ariès & University of Bonn.
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Journal ArticleDOI
Aerosol characteristics at a high‐altitude location in central Himalayas: Optical properties and radiative forcing
P. Pant,P. Hegde,Umesh Chandra Dumka,Ram Sagar,Sathianeson Satheesh,K. Krishna Moorthy,Auromeet Saha,Manoj K. Srivastava +7 more
TL;DR: In this article, the mass concentrations of aerosol black carbon (BC) and composite aerosols near the surface were carried out along with spectral aerosol optical depths (AODs) from a high-altitude station, Manora Peak in central Himalayas, during a comprehensive aerosol field campaign in December 2004.
Journal ArticleDOI
Characteristics of aerosol black carbon mass concentration over a high altitude location in the Central Himalayas from multi-year measurements
Umesh Chandra Dumka,Umesh Chandra Dumka,K. Krishna Moorthy,Rajesh Kumar,Prashant Hegde,Ram Sagar,P. Pant,Narendra Singh,S. Suresh Babu +8 more
TL;DR: In this paper, multi-year measurements of near surface aerosol black carbon (BC) mass concentration, made from a high altitude station at Manora Peak (29.4° N, 79.5° E, 1958 mmsl) in the Central Himalayas, using a 7-channel Aethalometer for 38 months from November 2004 to December 2007, are examined.
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The effect of magnetic fields on γ-ray bursts inferred from multi-wavelength observations of the burst of 23 January 1999
Titus Galama,Michael S. Briggs,Ralph A. M. J. Wijers,P. M. Vreeswijk,E. Rol,J. van Paradijs,J. van Paradijs,Chryssa Kouveliotou,Robert D. Preece,M. N. Bremer,Ian Smith,Remo P. J. Tilanus,A. G. de Bruyn,A. G. de Bruyn,Richard G. Strom,Richard G. Strom,Guy G. Pooley,A. J. Castro-Tirado,A. J. Castro-Tirado,Nial R. Tanvir,Nial R. Tanvir,Colin Robinson,Kevin Hurley,J. Heise,J. Telting,R. G. M. Rutten,Chris Packham,R.A. Swaters,John K. Davies,A. Fassia,Simon F. Green,Michael J. Foster,Ram Sagar,Ashwani Pandey,Nilakshi,R. K. S. Yadav,Eran O. Ofek,Elia M. Leibowitz,P. Ibbetson,James E. Rhoads,E. E. Falco,C. E. Petry,Chris Impey,Thomas R. Geballe,Dipankar Bhattacharya +44 more
Abstract: Gamma-ray bursts (GRBs) are thought to arise when an extremely relativistic outflow of particles from a massive explosion (the nature of which is still unclear) interacts with material surrounding the site of the explosion. Observations of the evolving changes in emission at many wavelengths allow us to investigate the origin of the photons, and so potentially determine the nature of the explosion. Here we report the results of γ-ray, optical, infrared, submillimetre, millimetre and radio observations of the burst GRB990123 and its afterglow. Our interpretation of the data indicates that the initial and afterglow emissions are associated with three distinct regions in the fireball. The peak flux of the afterglow, one day after the burst, has a lower frequency than observed for other bursts; this explains the short-lived radio emission. We suggest that the differences between bursts reflect variations in the magnetic-field strength in the afterglow-emitting regions.
Journal ArticleDOI
Aerosol Characteristics at a High Altitude Location in Central Himalayas: Optical Properties and Radiative Forcing
P. Pant,Prashant Hegde,Umesh Chandra Dumka,Ram Sagar,Sathianeson Satheesh,K. Krishna Moorthy +5 more
TL;DR: In this article, the mass concentrations of aerosol black carbon (BC) and composite aerosols near the surface were carried out along with spectral aerosol optical depths (AODs) from a high altitude station, Manora Peak in Central Himalayas, during a comprehensive aerosol field campaign in December 2004.
Journal ArticleDOI
Ground-based CCD astrometry with wide-field imagers - II. A star catalog for M 67: WFI@2.2 m MPG/ESO astrometry, FLAMES@VLT radial velocities
Rks Yadav,Luigi R. Bedin,Giampaolo Piotto,Jonathan Anderson,Santi Cassisi,Sandro Villanova,Imants Platais,Luca Pasquini,Yazan Momany,Ram Sagar +9 more
TL;DR: In this article, the relative proper motions and membership probabilities of stars in the open cluster M 67 (C0847+120, NGC 2682) were determined using the Wide Field Imager (WFIM) at the 2.2 m MPG/ESO telescope.