Articles written in Journal of Astrophysics and Astronomy
Volume 21 Issue 1-2 June 2000 pp 29-38
The outburst of X-ray transient source XTE J2012+381 was detected by the RXTE All-Sky Monitor on 1998 May 24th. Following the outburst, X-ray observations of the source were made in the 2–18 keV energy band with the Pointed Proportional Counters of the Indian X-ray Astronomy Experiment (IXAE) on-board the Indian satellite IRS-P3 during 1998 June 2nd–10th. The X-ray flux of the source in the main outburst decreased exponentially during the period of observation. No large amplitude short-term variability in the intensity is detected from the source. The power density spectrum obtained from the timing analysis of the data shows no indication of any quasi-periodic oscillations in 0.002–0.5 Hz band. The hardness ratio i.e. the ratio of counts in 6–18 keV to 2–6 keV band, indicates that the X-ray spectrum is soft with spectral index >2. From the similarities of the X-ray properties with those of other black hole transients, we conclude that the X-ray transient XTE J2012+381 is likely to be a black hole.
Volume 22 Issue 1 March 2001 pp 131-144
The design and performance of a portable three channel photometer installed at the Uttar Pradesh State Observatory (UPSO), Naini Tal is described. The photometer is modular and the whole unit can be disassembled as individual channels such that the system can also be used as a single channel or two channel photometer. The system also has provision to monitor a guide star. The instrument was put into operation since November 1999 on the 1m Sampurnanand telescope at UPSO, Naini Tal. Since then, it is used extensively for the ‘Survey of rapidly oscillating Ap (roAp) stars in the northern sky’ from UPSO. Observational results using this new photometer in its initial phase of operation are discussed. The advantage of having continuous sky measurement is demonstrated.
Volume 26 Issue 2-3 June 2005 pp 117-118
Volume 26 Issue 2-3 June 2005 pp 301-309
The Indian team at ISRO has been part of the Whole Earth Telescope (WET) team since 1988 when we first participated in the campaign on V471 Tau. We have been part of many other observing campaigns over the last decade. This presentation traces the circumstances leading to our joining the WET team and how useful the coverage from the Indian longitude has been. The results of several pulsators from the WET runs during which we participated are also described. These include PG1159-035 the prototype of the GW Vir type of stars, RE J 0751+14 a cataclysmic variable, PG 1336-018 a binary with an sdB pulsator and finally HR 1217 a roAp star. The paper concludes with what the limitations are in our observations and how we can overcome them in the future.
Volume 38 Issue 2 June 2017 Article ID 0026 Editorial
Volume 38 Issue 2 June 2017 Article ID 0031 Review Article
V. Bhalerao D. Bhattacharya A. Vibhute P. Pawar A. R. Rao M. K. Hingar Rakesh Khanna A. P. K. Kutty J. P. Malkar M. H. Patil Y. K. Arora S. Sinha P. Priya Essy Samuel S. Sreekumar P. Vinod N. P. S. Mithun S. V. Vadawale N. Vagshette K. H. Navalgund K. S. Sarma R. Pandiyan S. Seetha K. Subbarao
The Cadmium Zinc Telluride Imager (CZTI) is a high energy, wide-field imaging instrument on AstroSat. CZTI’s namesake Cadmium Zinc Telluride detectors cover an energy range from 20 keV to >200 keV, with 11% energy resolution at 60 keV. The coded aperture mask attains an angular resolution of 17′ over a 4.6∘× 4.6∘ (FWHM) field-of-view. CZTI functions as an open detector above 100 keV, continuously sensitive to GRBs and other transients in about 30% of the sky. The pixellated detectors are sensitive to polarization above ∼100 keV, with exciting possibilities for polarization studies of transients and bright persistent sources. In this paper, we provide details of the complete CZTI instrument, detectors, coded aperture mask, mechanical and electronic configuration, as well as data and products.
Volume 38 Issue 2 June 2017 Article ID 0032 Review Article
M. C. Ramadevi B. T. Ravishankar N. Sitaramamurthy G. Meena Brajpal Singh Anand Jain Reena Yadav Anil Agarwal V. Chandra Babu Kumar Ankur Kushwaha S. Vaishali Nirmal Kumar Iyer Anuj Nandi Girish V. Vivek Kumar Agarwal S. Seetha Dipankar Bhattacharya K. Balaji Manoj Kumar Prashanth Kulshresta
We report the in-orbit performance of Scanning Sky Monitor (SSM) onboard AstroSat. The SSM operates in the energy range 2.5 to 10 keV and scans the sky to detect and locate transient X-ray sources. This information of any interesting phenomenon in the X-ray sky as observed by SSM is provided to the astronomical community for follow-up observations. Following the launch of AstroSat on 28th September, 2015, SSM was commissioned on October 12th, 2015. The first power ON of the instrument was with the standard X-ray source, Crab in the field-of-view. The first orbit data revealed the basic expected performance of one of the detectors of SSM, SSM1. Following this in the subsequent orbits, the other detectors were also powered ON to find them perform in good health. Quick checks of the data from the first few orbits revealed that the instrument performed with the expected angular resolution of 12’ × 2.5∘ and effective area in the energy range of interest. This paper discusses the instrument aspects along with few on-board results immediately after power ON.
Volume 38 Issue 2 June 2017 Article ID 0033 Review Article
A. R. Rao M. H. Patil Yash Bhargava Rakesh Khanna M. K. Hingar A. P. K. Kutty J. P. Malkar Rupal Basak S. Sreekumar Essy Samuel P. Priya P. Vinod D. Bhattacharya V. Bhalerao S. V. Vadawale N. P. S. Mithun R. Pandiyan K. Subbarao S. Seetha K. Suryanarayana Sarma
Charged Particle Monitor (CPM) on-board the Astrosat satellite is an instrument designed to detect the flux of charged particles at the satellite location. A Cesium Iodide Thallium (CsI(Tl)) crystal is used with a Kapton window to detect protons with energies greater than 1 MeV. The ground calibration of CPM was done using gamma-rays from radioactive sources and protons from particle accelerators. Based on the ground calibration results, energy deposition above 1 MeV are accepted and particle counts are recorded. It is found that CPM counts are steady and the signal for the onset and exit of South Atlantic Anomaly (SAA) region are generated in a very reliable and stable manner.
Volume 39 Issue 1 February 2018 Article ID 0011 Review
Scanning Sky Monitor (SSM) onboard AstroSat is an X-ray sky monitor in the energy range 2.5–10 keV. SSM scans the sky for X-ray transient sources in this energy range of interest. If an X-ray transient source is detected in outburst by SSM, the information will be provided to the astronomical community for follow-up observations to do a detailed study of the source in various other bands. SSM instrument, since its power-ON in orbit, has observed a number of X-ray sources. This paper discusses observations of few X-ray transients by SSM. The flux reported by SSM for few sources during its Performance Verification phase (PV phase) is studied and the results are discussed.
Volume 40 | Issue 4
Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.
Click here for Editorial Note on CAP Mode