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Now showing items 1161-1180 of 1333

Intranight optical variability of radio-quiet and radio lobe dominated quasars

Stalin, C. S.; Gopal-Krishna; Sagar, R.; Wiita, P. J. (2004)

We present results of a programme of multi-epoch, intranight optical monitoring of a sample of non-blazar-type active galactic nuclei (AGN), which includes seven radio-quiet quasars (RQQs) and an equal number of radio-loud, ...
Surface photometry of three Wolf-Rayet galaxies

Singh, M.; Sanwal, B. B.; Stalin, C. S. (2001)

CCD photometric observations of the Wolf-Rayet galaxies NGC 1741, IIZw40 and IRAS 01003-2238 were taken with 104 cm telescopes of the U. P. State Observatry BainiTal using 1024 х 1024 CCD camera in B V R I and Hα filters. ...
Early optical and millimeter observations of GRB 030226 afterglow

Pandey, S. B.; Sagar, R.; Anupama, G. C.; Bhattacharya, D.; Sahu, D. K.; Castro-Tirado, A. J.; Bremer, M. (2004)

The CCD magnitudes in Johnson UBV and Cousins RI photometric passbands for the afterglow of the long duration GRB 030226 are presented. Upper limits of a few mJy to millimeter wave emission at the location of optical are ...
Non-uniform extinction in young open star clusters

Yadav, R. K. S.; Sagar, R. (2001)

The extinction law and the variation of colour excess with position, luminosity and spectral class in young open star clusters NGC 663, NGC 869, NGC 884, NGC 1502, NGC 1893, NGC 2244, NGC 2264, NGC 6611, Tr 14, Tr ...
Wolf-Rayet galaxies and their CCD photometry

Sanwal, B. B. (2001)

Galaxies with Wolf-Rayet star features in their spectra have long been konwn. They are characterised by a broad emission features at λ 4686 Å. This is attributed to stellar HeII emission from a large population of WR stars. ...
Intranight optical variability of blazers

Sagar, R.; Stalin, C. S.; Gopal-Krishna; Wiita, P. J. (2004)

We present results of a multi-epoch intranight optical monitoring of 11 blazars consisting of six BL Lac objects and five radio core-dominated quasars (CDQs). These densely sampled and sensitive R-band CCD observations, ...
On the determination of age and mass functions of stars in young openstar clusters from the analysis of their luminosity functions

Piskunov, A. E.; Belikov, A. N.; Kharchenko, N. V.; Sagar, R.; Subramaniam, A. (2004)

We construct the observed luminosity functions of the remote young open clusters NGC 2383, 2384, 4103, 4755, 7510 and Hogg 15 from CCD observations of them. The observed LFs are corrected for field star contamination ...
The north–south asymmetry of soft x-ray flare index during solar cycles 21, 22 and 23

Joshi, B.; Joshi, A. (2004)

In this paper the N–S asymmetry of the soft X-ray flare index (FI sxr) during solar cycles 21, 22 and 23 has been analyzed. The results show the existence of a real N–S asymmetry which is strengthened during solar minimum. ...
Dynamical properties of flare Loops of 27 November 1996

Uddin, W.; Prasad, L. (2001)

We observed a post-flare loop system in Hα on the west limb on 27 November 1996 which started earlier than 05:07:20 UT in NOAA active region 7997 (N04, W89). The post-flare loops were associated with long duration x-ray ...
Emissions from GRBs and their afterglows: Indian observations

Sagar, R. (2001)

The study of Gamma-ray bursts, electromagnetically the most luminous events in the Universe though only for a few seconds, was revolutionized in 1997 when the Italian-Dutch X-ray satellite BeppoSAX started providing the ...
A comprehensive CCD photometric study of the open cluster NGC 2421

Yadav, R. K. S.; Sagar, R. (2004)

We present the UBVRI CCD photometry in the region of the open cluster NGC 2421. The radius of the cluster is determined as ~3.0 arcmin using a stellar density profile. Our study indicates that the metallicity of the cluster ...
A multicolour CCD photometric and mass function study of the distant southern open star clusters NGC 3105, NGC 3603, Melotte 105, Hogg 15, NGC 4815, Pismis 20 and NGC 6253

Sagar, R.; Munari, U.; de Boer, K. S. (2001)

We derive cluster parameters and mass functions from new UBVRI CCD photometric observations of ~3500 stars reaching down to V~ 20 mag for the distant southern open star clusters NGC 3105, NGC 3603, Melotte 105, Hogg ...
Characteristics of aerosol spectral optical depths over Manora Peak: A high-altitude station in the central Himalayas

Sagar, R.; Kumar, B.; Dumka, U. C.; Moorthy, K. K.; Pant, P. (2004)

We present, for the first time, spectral behavior of aerosol optical depths (AODs) over Manora Peak, Nainital, located at an altitude of ~2 km in the Shivalik ranges of the central Himalayas. The observations were carried ...
NGC 7654: An interesting cluster to study star formation history

Pandey, A. K.; Nilakshi; Ogura, K.; Sagar, R.; Tarusawa, K. (2001)

CCD UBVIc photometry in a wide field around the open cluster NGC 7654 has been carried out for ∼17 860 stars, down to V ∼ 20. The reddening across the cluster region is found to be variable with E(B −V )min = 0.46 to E(B ...
Structure and mass function of five intermediate/old open clusters

Durgapal, A. K.; Pandey, A. K. (2001)

The UBVRI data of five northern open star clusters are used to study the mass function (MF), structure and dynamical state of these clusters. The clusters under discussion have ages ranging from ∼0.6 to 5 Gyr. A ...
HD 12098 – A new northern hemisphere roAp star

Girish, V.; Seetha, S.; Martinez, P.; Joshi, S.; Ashoka, B. N.; Kurtz, D. W.; Chaubey, U. S.; Gupta, S. K.; Sagar, R. (2001)

We present the analysis of 65 hours of high speed photometric observations of HD 12098 taken from State Observatory, Naini Tal and Gurushikhar Observatory, Mt. Abu on sixteen nights spanning from November 1999 to November ...
A comprehensive study of the rich open star cluster NGC 2099 based on deep BV I CCD observations

Nilakshi; Sagar, R. (2002)

The CCD observations of the rich open star cluster NGC 2099 and its surrounding field region have been carried out up to a limiting magnitude of V ∼ 22 mag in B, V and I passbands for the first time. A total of ∼12 000 ...
A deep VI CCD photometric study of the neglected galactic star cluster NGC 6631

Sagar, R.; Naidu, B. N.; Mohan, V. (2001)

We present the VI CCD photometric observations of about 5500 stars up to a limiting magnitude of V~ 20 in an area of ~16'⨯16' around the cluster NGC 6631. The cluster parameters determined for the first time by fitting the ...
Dust in an extragalactic environment: The case of NGC 2907

Patil, M. K.; Pandey, S. K.; Kembhavi, A. K.; Singh, M. (2001)

We have carried out a detailed CCD surface photometric analysis of the lenticular galaxy NGC 2907, containing multiple dust lanes, with the objective of studying properties of dust in an extragalactic environment. Measurements ...
Search for microlensing events towards M31 galaxy

Joshi, Y. C.; Pandey, A. K.; Narasimha, D.; Sagar, R. (2001)

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 massive astrophysical compact ...

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