Articles written in Journal of Astrophysics and Astronomy

    • Supernova neutrinos: Flavor conversion independent of their mass


      More Details Abstract Fulltext PDF

      In extremely dense neutrino environments like in supernova core, the neutrino-neutrino refraction may give rise to self-induced flavor conversion. These neutrino flavor oscillations are well understood from the idea of the exponentially growing modes of the interacting oscillators in the flavor space. Until recently, the growth rates of these modes were found to be of the order of the vacuum oscillation frequency $\Delta m^2/2E$ $[O(1 {\rm km}^{−1})]$ and were considered slow growing. However, in the last couple of years it was found that if the system was allowed to have different zenith-angle distributions for the emitted $\nu_e$ and $\bar{\nu}_e$ beams then the fastest growing modes of the interacting oscillators grew at the order of $\mu =\sqrt{2G_{\rm F}n_ν}$ , a typical $\nu–\nu$ interaction energy $[O(10^5 {\rm km}^{−1})]$. Thus the growth rates are very large in comparison to the so-called ‘slow oscillations’ and canresult in neutrino flavor conversion on a much faster scale. In fact, the point that the growth rates are no longer dependent on the vacuum oscillation frequency $\Delta m^2/2E$, makes these ‘fast flavor conversions’ independentof $\Delta m^2$ (thus mass) and energy. This is a surprising result as neutrino flavor conversions are considered to be the ultimate proof of massive neutrinos. However, the importance of this effect in the realistic astrophysical scenarios still remains to be understood.

    • A multiresolution approach to enhance small telescope data under non-ideal conditions


      More Details Abstract Fulltext PDF

      Astronomical imaging of a star cluster is one of the paramount ways to learn about stellar evolution, stellar dynamics. A large telescope is not generally accessible to all observers. In that context, small telescope observations with a proper denoising scheme can be an excellent alternative. This paperproposes a technique to denoise star cluster data using an undecimated wavelet transform, with a modified thresholding process. Our work aims to prove the effectiveness of such a wavelet-based technique on realtime data. We present drastically noise-infested observational data of the NGC 2301 star cluster, captured over five nights from Fr. Eugene Lafont Observatory, Kolkata. We observe that for highly noise-polluted data, the conventional methods of dark frame subtraction and flat frame division are inadequate to producethe desired quality of images due to functioning exclusively in the spatial domain. Thus, we take the wavelet-based multiresolution approach to ameliorate those raw images. We also introduce a modified thresholding function to modulate the image at different resolution levels. A standard star detecting software Daophot II quantifies the increment in the number of detected stars from raw images to theimages processed by our proposed method as: for red filter 397–903, for green filter 663–945, for blue filter 362–896. On the contrary, Daophot II can’t detect any star in the highly noise-polluted images processed by the conventional methods. Therefore, we hope our proposed processing methodology willmotivate others to initiate small telescope observations from any site restrained by its geographical location.

  • 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

© 2022-2023 Indian Academy of Sciences, Bengaluru.