Nainital Microlensing Survey -- detection of short period Cepheids in the disk of M31 (2009)
Joshi, Y. C., Narasimha, D., Pandey, A. K., Sagar, R.
The discovery of large number of Cepheid variables in far-off galaxies offers a unique opportunity to determine the accurate distance of the host galaxy through their period-luminosity relation. The...
A QSO plus host system lensed into a 6" Einstein ring by a low redshift galaxy (2008)
We report the serendipitous discovery of an "Einstein Ring" in the optical band from the Sloan Digital Sky Survey (SDSS) data and associated four images of a background source. The lens galaxy...
Gravitational Lens Systems to probe Extragalactic Magnetic Fields (2008)
The Faraday rotation measurements of multiply-imaged gravitational lens systems can be effectively used to probe the existence of large-scale ordered magnetic fields in lensing galaxies and galaxy...
Photometric study of two Novae in M31 (2006)
Joshi, Y-C., Pandey, A-K., Narasimha, D., Giraud-Heraud, Y., Sagar, R., Kaplan, J.
We report $R_cI_c$ light curves of 2 novae in M31 galaxy which were detected in the four year long Nainital Microlensing Survey. One of these novae has been tracked from the initial increase in flux...
Photometric study of two Novae in M31 (2006)
Joshi, Y-C., Pandey, A-K., Narasimha, D., Giraud-Heraud, Y., Sagar, R., Kaplan, J.
We report $R_cI_c$ light curves of 2 novae in M31 galaxy which were detected in the four year long Nainital Microlensing Survey. One of these novae has been tracked from the initial increase in flux...
Photometric study of two Novae in M31 (2006)
Joshi, Y-C., Pandey, A-K., Narasimha, D., Giraud-Heraud, Y., Sagar, R., Kaplan, J.
We report $R_cI_c$ light curves of 2 novae in M31 galaxy which were detected in the four year long Nainital Microlensing Survey. One of these novae has been tracked from the initial increase in flux...
First microlensing candidate towards M31 from the Nainital Microlensing Survey (2004)
Joshi, Y. C., Pandey, A. K., Narasimha, D., Sagar, R.
We report our first microlensing candidate NMS-E1 towards M31 from the data accumulated during the four years of Nainital Microlensing Survey. Cousin R and I band observations of ~13'x13' field in...
PKS1830-211: The strongest lensed radio source (2004)
The Ooty lens PKS1830-211 is a bright, variable radio source at a redshift of 2.507 consisting of a compact flat spectrum core, associated knot and jet, which are lensed by an intervening spiral...
Photometric study of two Novae in M31 (2004)
Joshi, Y-C., Pandey, A-K., Narasimha, D., Giraud-Heraud, Y., Sagar, R., Kaplan, J.
We report $R_cI_c$ light curves of 2 novae in M31 galaxy which were detected in the four year long Nainital Microlensing Survey. One of these novae has been tracked from the initial increase in flux...
Photometric study of two Novae in M31 (2004)
Joshi, Y-C., Pandey, A-K., Narasimha, D., Giraud-Heraud, Y., Sagar, R., Kaplan, J.
We report $R_cI_c$ light curves of 2 novae in M31 galaxy which were detected in the four year long Nainital Microlensing Survey. One of these novae has been tracked from the initial increase in flux...
Detection of OH and wide HI absorption toward B0218+357 (2003)
Kanekar, N., Chengalur, J. N., De Bruyn, A. G., Narasimha, D.
We present deep GMRT OH and WSRT HI absorption spectra of the $z = 0.6846$ gravitational lens toward B0218+357. Both the 1665 MHz and 1667 MHz OH lines are clearly detected for the first time while a...
Photometric study of two novae in M31 (2003)
Joshi, Y. C., Pandey, A. K., Narasimha, D., Giraud-Héraud, Y., Sagar, R., Kaplan, J.
We report $R_cI_c$ light curves of 2 novae in the M31 galaxy which were detected in the four year Nainital Microlensing Survey. One of these novae has been tracked from the initial increase in flux...
Identification of 13 Cepheids and 333 Other Variables in M31 (2002)
Joshi, Y. C., Pandey, A. K., Narasimha, D., Sagar, R., Giraud-Hiraud, Y.
We present Cousins $R$ and $I$ band photometry of variable stars in a $\sim13'\times 13'$ region in the disk of M31 galaxy, obtained during 141 nights. Of the 26 Cepheid variables present in the...
Determination of time delay from the gravitational lens B1422+231 (2001)
We present the radio light curves of lensed images of the gravitational lens B1422+231. The observations have been carried out using the VLA at 8.4 and 15 GHz over a period of 197 days. We describe a...
Search for Microlensing Events Towards M31 Galaxy (2001)
Joshi, Y. C, Pandey, A. K, Narasimha, D, Sagar, R
M31, the prominent galaxy of the Local Group, is located at a distance of about 700 kpc. Due to its convenient orientation, it is an alluring target for gravitational microlensing to search for...
Probes of superclusters at moderate redshifts (2000)
Detection of superclusters at z = 0.2 - 1.0 and determination of their mass provide constraints on the theories of structure formation in the Universe. A combination of the study of hot gas observed...
HI and OH absorption at z=0.89 (1999)
Chengalur, Jayaram N., De Bruyn, A. G., Narasimha, D.
We report on WSRT observations of HI and OH absorption at z=0.885 towards the radio lens PKS 1830-21, mm wave transitions of several molecular species have already been observed at this redshift. At...
Some Characteristics of Galactic Cepheids Relevant to the Calibration of the Distance Scale (1998)
Mazumdar, Anwesh, Narasimha, D.
An analysis of the observed characteristics of the Galactic Cepheid variables is carried out in the framework of their period-luminosity relation being used as a standard candle for distance...
Cepheid Distance to M100 in Virgo Cluster (1998)
Narasimha, D., Mazumdar, Anwesh
A measurement of the distance to Virgo Cluster by a direct method along with a realistic error analysis is important for a reliable determination of the value of Hubble Constant. Cepheid variables in...
Role of the scalar field in gravitational lensing (1998)
Virbhadra, K. S., Narasimha, D., Chitre, S. M.
A static and circularly symmetric lens characterized by mass and scalar charge parameters is constructed. For the small values of the scalar charge to the mass ratio, the gravitational lensing is...
Surface effects on the solar oscillation frequencies (1996)
The solar p-mode frequencies and eigenfunctions are modified by four processes operative in the atmosphere and the subphotospheric layers which can be, to a good approximation, treated as surface...
Straight arcs in gravitational lens systems (1993)
Faint straight arcs extending over ten to twenty arcseconds have been observed behind rich clusters of galaxies elongated by the lensing action of the foreground cluster. When a cluster of galaxies...
Lenses of small angular scales from Jodrell Bank survey (1993)
The Jodrell Bank 5 GHz sky survey provides a complete flux-limited sample of radio sources at latitude greater than 2.5 deg which are brighter than 200 mJy and have a spectrum flatter than 0.5. From...
Helioseismic detections of overshoot below the solar convection zone (1993)
Basu, S, Antia, H. M, Narasimha, D
It is generally accepted that there is no adequate theory to describe astrophysical convection. In particular, there is no agreement among different theories about the extent of overshoot from...
Solar and Stellar Convection (1988)
The flow field in stellar convection zones, characterised by high Rayleigh number, low Prandtl number and large Reynolds number, is time dependent and turbulent, consisting of eddies having a range...