• K. T. PAUL

      Articles written in Journal of Astrophysics and Astronomy

    • Short-Term H$\alpha$ Line Variations in Classical Be Stars: 59 Cyg and OT Gem

      K. T. Paul S. B. Shruthi Annapurni Subramaniam

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      We present the optical spectroscopic study of two classical Be stars, 59 Cyg and OT Gem obtained over a period of few months in 2009. We detected a rare triple-peak H$\alpha$ emission phase in 59 Cyg and a rapid decrease in the emission strength of H$\alpha$ in OT Gem, which are used to understand their circumstellar disks. We find that 59 Cyg is likely to be rapid rotator, rotating at a fractional critical rotation of $\sim$ 0.80. The radius of the H$\alpha$ emission region for 59 Cyg is estimated to be \( R_d/R_*\) $\sim$, assuming a Keplerian disk, suggesting that it has a large disk. We classify stars which have shown triple-peaks into two groups and find that the triple-peak emission in 59 Cyg is similar to $\zeta$ Tau. OT Gem is found to have a fractional critical rotation of $\sim$0.30, suggesting that it is either a slow rotator or viewed in low inclination. In OT Gem, we observed a large reduction in the radius of the H$\alpha$ emission region from $\sim$6.9 to $\sim$1.7 in a period of three months, along with the reduction in the emission strength. Our observations suggest that the disk is lost from outside to inside during this disk loss phase in OT Gem.

    • Study of classical Be stars in open clusters older than 100 Myr

      MADHU KASHYAP JAGADEESH BLESSON MATHEW K. T. PAUL GOURAV BANERJEE ANNAPURNI SUBRAMANIAM R. ARUN

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      We performed the slitless spectroscopic survey to identify classical Be (CBe) stars in openclusters older than 100 Myr. Observing a sample of 71 open clusters, we identified 13 CBe stars in 11 open clusters, one of, which (TYC 2679-432-1) is a new detection. The 13 CBe stars show both H$\alpha$ in emission and IR excess, which confirm that they possess gaseous circumstellar discs. Two more CBe stars are found toexhibit H$\alpha$ in absorption for the first time, indicating that might be passing through disc-less episode presently. The spectral-type estimation is done for all these 15 stars and it is noticed that they belong to B0.5–B8 type. Moreover, we found that the distribution of our sample is peaking near late B-types as expected.

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    • 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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      Posted on July 25, 2019

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