• Jayant Murthy

      Articles written in Journal of Astrophysics and Astronomy

    • Upper limits on O VI emission fromVoyager observations

      Jayant Murthy

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      We have examined 426Voyager fields distributed across the sky for O VI (γγ 1032/1038 å) emission from the Galactic diffuse interstellar medium. No such emission was detected in any of our observed fields. Our most constraining limit was a 90% confidence upper limit of 2600 photons cm−2 sr−1 s−1 on the doublet emission in the direction (l, b) = (117.3, 50.6). Combining this with an absorption line measurement in nearly the same direction allows us to place an upper limit of 0.01 cm−3 on the electron density of the hot gas in this direction. We have placed 90% confidence upper limits of less than or equal to 10,000 photons cm−2 sr−1 s−1 on the O VI emission in 16 of our 426 observations.

    • Template-based classification of SDSS-GALEX point sources


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      We have classified a sample of 37,492 objects from SDSS into QSOs, galaxies and stars using photometric data over five wave bands ($u, g, r , i$ and $z$) and UV GALEX data over two wave bands (near-UV and far-UV) based on a template fitting method. The advantage of this method of classification is that it does not require any spectroscopic data and hence the objects for which spectroscopic data is not available can also be studied using this technique. In this study, we have found that our method is consistent by spectroscopic methods given that their UV information is available. Our study shows that the UV colours are especially important for separating quasars and stars, as well as spiral and starburst galaxies. Thus it is evident that the UVbands play a crucial role in the classification and characterization of astronomical objects that emit over a wide range of wavelengths, but especially for those that are bright at UV. We have achieved the efficiency of 89% for the QSOs, 63% for the galaxies and 84% for the stars. This classification is also found to be in agreement with the emission line diagnostic diagrams.

    • JUDE (Jayant’s UVIT Data Explorer) pipeline user manual


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      We have written a reference manual to use JUDE (Jayant’s UVIT Data Explorer) data pipeline software for processing and reducing the Ultraviolet Imaging Telescope (UVIT) Level 1 data into event listsand images—Level 2 data. The JUDE pipeline is written in the GNU Data Language (GDL) and released as an open-source which may be freely used and modified. GDL was chosen because it is an interpreted language allowing interactive analysis of data; thus in the pipeline, each step can be checked and run interactively. This manual is intended as a guide to data reduction and calibration for the users of the UVIT data.

    • UVIT study of UV bright stars in the globular cluster NGC 4147


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      We present far ultraviolet (FUV) observations of globular cluster NGC 4147 using three FUV filters, BaF2 (F154W), sapphire (F169M), and silica (F172M) of Ultra-Violet Imaging Telescope (UVIT) onboard the AstroSat satellite. We confirmed the cluster membership of the UVIT observed sources usingproper motions from Gaia data release 2 (GAIA DR2). We identified 37 blue horizontal branch stars (BHBs), one blue straggler star (BSS) and 15 variable stars using UV-optical color magnitude diagrams (CMDs). We find that all the FUV bright BHBs are second generation population stars. Using UV-optical CMDs, weidentify two sub-populations, BHB1 and BHB2, among the UV-bright BHBs in the cluster with stars count ratio of 24:13 for BHB1 and BHB2. The effective temperatures ($T_{\rm eff}$) of BHB1 and BHB2 were derived using color-temperature relation of BaSTI-IAC zero-age horizontal branch (ZAHB). We found that BHB1 stars are more centrally concentrated than BHB2 stars. We also derive physical parameters of the detected FUV bright BSS by fitting younger age BaSTI-IAC isochrones on optical and UV-optical CMDs.

  • Journal of Astrophysics and Astronomy | News

    • Continuous Article Publication

      Posted on January 27, 2016

      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.

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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