Alok Chandra Gupta


Research Summary:
Most of my research interest for the last few years have been Multi- wavelengths variability of different classes of Active Galactic Nuclei and Photometric studies of Star Clusters in the Milky Way.

1. Optical Variability of Gamma-Ray Loud Blazars
Blazars display flux variability on diverse timescales ranging from minutes to months. On our blazar monitoring project carried out on the 1.2 meter telescope at Gurushikhar, Mount Abu, India, we selected some $\gamma-$ray loud blazars to study the variability over both the short and the long time scales. In this paper we have reported results based on photometric monitoring on 8 nights for 5 blazars: S5 0716$+$714, OJ 287, S4 0954$+$658, Mrk 421 and PKS 2155$-$304 in B and R passbands. Micro variability and rapid variability has been observed in these sources suggesting that variability is a common property in these objects.

2. Comparison of Intra-night Optical variability of all classes of the powerful AGN
We have observed about 30 nights for searching intra-night optical variability of different classes of powerful AGNs using 3 optical telescopes in India:
(i) 2.34 meter IIA Telescope, Vainu Bappu Telescope at Kavalur
(ii) 1.2 meter PRL Telescope at Mt. Abu
(iii) 1.02 meter State Observatory Telescope at Naini Tal
Using our data we have compared the intra-night variability properties of different classes of AGNs.

3. Discovery of Planetary Nebulae (PNe) in the Young Open Clusters
We have discovered 18 PNe in 3 young open clusters namely NGC 6834, NGC 6913 and NGC 7654. This is the first result of detection of PNe in Open Clusters.

4. Simultaneous Multi-Wavelengths Variability of Blazars
I am working on this project in one international group known as WEBT (Whole Earth Blazar Telescope) group and we have recently started this project using ground based Indian Telescopes.
A key goal for the observations of variability that will be carried out over the next few years will be to characterize its frequency and magnitude for blazars over wide range of wavelengths. Ground based observations provide most of the data in the $\gamma$-ray, optical, IR and radio wavelengths. Orbiting telescopes for investigating UV, X-ray and $\gamma$-ray wavelengths. The most telling results will almost certainly emerge from multi-frequency observations that simultaneously monitor a particular object for extended periods. When simultaneous observations at a wide range of wavelengths are compared with more fully developed theories, we will have a good chance to clarifying the relevant physics.

Publications:

1. Optical Variability of Gamma-Ray Loud Blazars,
A. C. Gupta, U. C. Joshi & J. H. Fan
(2002), Astrophysics $\&$ Space Science, 282, 655
2. Add Star Experiment: A New Approach,
A. C. Gupta, R. Sagar (2003), (submitted to New Astronomy)
3. Comparison of the Intra-night Optical Variability of All Classes of Powerful AGN,
C. S. Stalin, Gopal - Krishna, A. C. Gupta, R. Sagar, U. C. Joshi & P. J. Wiita
(2003) (submitted to MNRAS)
4. Discovery of Planetary Nebulae in the Young Open Clusters NGC 6834, NGC 6913 and NGC 7654,
A. C. Gupta, E. K. Grebel & G. J. Miller
(2003) (in preparation for Astronomy & Astrophysics Letters)


Conference/Workshops Attended:

1. School and Workshop on Distributed Parallel Computing for Physicists during April 11-19, 2002 at HRI, Allahabad.


Visits to other Institutes:

1. National Center for Radio Astronomy (NCRA) - TIFR, Pune during July 21, 2002 to August 01, 2002.
2. Physical Research Laboratory (PRL), Ahmedabad during February 21 to March 06, 2003.


Invited Lectures/Seminars:

1. Solar System and Eclipses, May 18, 2002 at Nehru Planterium, Allahabad, India.
2. Variability in Active Galactic Nuclei, October 27, 2002 at Harish-Chandra Research Institute, Allahabad, India.
3. Star Clusters in the Milky Way Galaxy, March 04, 2003 at Physical Research Laboratory, Ahmedabad, India.


Academic recognition/Awards:

1. I am the principal investigator in the project Simultaneous multi-wavelengths observations of blazars. Telescope time during January 4-6, 2003 were alloted to our project for observations on following telescopes:
(i) 2.34 meter Vainu Bappu IIA telescope at Vainu Bappu Observatory, Kavalur for optical observations
(ii) 2.0 meter IIA telescope at Hanle for optical observations
(iii) 1.2 meter PRL telescope at Mount Abu for IR observations
(iv) $\gamma-$ray TIFR telescope at Pachmarhi for $\gamma-$ray observations
2. I am the Co-PI in an international project Simultaneous multi-wavelengths observations of blazars. Telescope time during February 25 - March 05, 2003 was given at 1.2 meter PRL telescope at Mount Abu for IR observations of the project. Observing time were also alloted during above period on various ground based telescopes all around the globe in different wavelengths and also at RXTE (Rossi X-ray Telescope).

3. I am the Co-PI in a project Radio sources in the 2dF galaxy survey: observing star forming region. Dr. J. S. Bagla of HRI is PI of the project. 48 hours of observing time was alloted to us on GMRT in Dec. 2002.


3. Other Activities:
1. Teaching:
A complete course on Multi-wavelength Observations and Data Analysis Techniques at HRI in the year 2002$-$2003.
2. Project Supervised:
Mr. Ritaban Chatterjee from Indian Institute of Technology (IIT), Kanpur spent about 6 weeks at HRI and did a M. Sc Project on Astronomical Image Processing and Stellar Aperture Photometry.
3. Talks in Astrophysics Journal Club:
(i) The Canada-France Redshift Survey. I. Introduction to the Survey, Photometric Catalogs, and Surface Brightness Selection Effects
(ii) The Canada-France Redshift Survey. II. Spectroscopic Program: Data for the 0000-00 and 1000+25 Fields
(iii) The Canada-France Redshift Survey. III. "Single Emission-Line" Objects analysis of repeat Observations, and Spectroscopic Identifications
(iv) The Canada-France Redshift Survey. IV. Spectroscopic Selection Effects and 0300+00 Field Spectroscopic Data
(v) The Canada-France Redshift Survey. V. Global Properties of the Sample



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