• N. M. Ashok

      Articles written in Journal of Astrophysics and Astronomy

    • XX Cam—The Inactive R CrB star

      I. Kameswara Rao N. M. Ashok P. V. Kulkarni

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      Infrared observations obtained six years apart of the R CrB type star XX Cam do not show any infrared excess, unlike all the other members of the class. The observed colours match a 7000 K black body energy distribution quite well. From the year 1898 till todate, apparently XX Cam has undergone only one visual light minimum in 1940. The lack of infrared excess, the abundance peculiarities and further lack of small amplitude light variations with periods of few tens of days, which are characteristic of R CrB type stars, are discussed in terms of theoretical pulsation models of helium stars.

    • Optical interferometric observations of a transient event of 1986 March 13 in the coma of Comet Halley

      C. Debi Prasad T. Chandrasekhar J. N. Desai N. M. Ashok Vinod Krishan

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      During the recent apparition of Comet Halley in 1985-86 a transient ionic event in the form of a blob of H2 O+ emission was recorded in thecoma at ∼ 0h UT on 1986 March 13. Observations were carried out using a special IHW filter for H2 O+ emission at 7000 å/175 å, a 35 cm telescope, a Fabry-Perot interferometer and an image intensifier camera from Gurushikhar, Mt Abu. (24‡39’N,72‡ 47’E). A Fabry-Perot inter-ferogram in Ha taken a few minutes later at the same location reveals strong hydrogen emission (Hα) associated with the blob. The velocity field in the blob is structured with relative velocities upto ∼ 35km s−1. The event is interpreted as arising due to the sector boundary crossing of the interplanetary magnetic field by the comet

    • The excitation mechanism of [Fe XIV] 5303 å line in the inner regions of solar corona

      K. P .Raju J. N. Desai T. Chandrasekhar N. M. Ashok

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      The line intensity of the green coronal line and the continuum intensity are derived from the filter and white light photographs of the solar corona obtained during the 1980 total solar eclipse. Ratio of the line to continuum intensity is plotted against the radial distancer(=R/R0,R0 is the solar radius), in various position angles. A simple model assuming an electron density dependence of the line and continuum intensities suggests a dominant collisional mechanism for the excitation of the line in the innermost regions (∼ 1.4R0). The measured line to continuum ratio tends to a constant value at different radial distances in different position angles. The constancy of the measured line to continuum ratio indicates significant radiative excitation beyond 1.4 R0, in some of the position angles.

    • A high speed photometer in the optical region for lunar occultation studies

      T. Chandrasekhar N. M. Ashok Sam Ragland

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      High speed photometry during the lunar occultation of a stellar system provides an effective means of achieving high angular resolution in one dimension at the sub arc second level which is well suited for resolving close binary projected separations in the range of 10–100 milliarc seconds. An optical fast photometer designed for such a purpose is described and some results from the initial observations taken with the system including the resolution of a projected separation of 55 milli arcsecond in one binary system are detailed.

    • Near infrared coronal line emission in Nova Herculis 1991

      T. Chandrasekhar N. M. Ashok Sam Ragland

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      Near infrared coronal line emission at 1.98 ± 0.02Μm due to [Si VI] detected in the spectrum of Nova Herculis 1991 about 17 days after optical maximum is reported. The early appearance of coronal emission is yet another unusual feature of this fast nova in which early onset of dust formation processes and X-ray detection five days after outburst have already been reported. The coronal line observations reported here are consistent with X-ray detection and support a hot shocked circumstellar envelope at the periphery of the dust formation zone in the nova.

  • 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.

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