• SAURABH SHARMA

      Articles written in Journal of Astrophysics and Astronomy

    • Detection of PAH and nbL features in planetary nebulae NGC 7027 and BD $+$30$^{\circ}$ 3639 with TIRCAM2 instrument on 3.6 m DOT

      RAHUL KUMAR ANAND SHANTANU RASTOGI BRIJESH KUMAR ARPAN GHOSH SAURABH SHARMA D. K. OJHA S. K. GHOSH

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      High resolution infrared imaging observations of the young planetary nebulae (PNe) NGC 7027 and BD $+$30$^{\circ}$ 3639, taken with the newly installed TIFR near infrared camera-II (TIRCAM2) on 3.6 m Devasthal optical telescope (DOT), ARIES, Nainital, are being reported. The images are acquired in J, H, K,polycyclic aromatic hydrocarbon (PAH) and narrow-band L (nbL) filters. The observations show emission from warm dust and PAHs in the circumstellar shells. The imaging of the two objects are among the first observations in PAH and nbL bands using TIRCAM2 on DOT. The NGC 7027 images in all bands showsimilar elliptical morphology with $\sim$6$^{\prime\prime}$.7 and $\sim$4$^{\prime\prime}$.5 semi-major and semi-minor axes. Considering size up to 10% of peak value the nebula extends upto 800 from the central star revealing a multipolar evolution. The relatively cooler BD $+$30$^{\circ}$ 3639 shows a rectangular-ring shaped nebula. In J and H bands it shows an angular diameter of $\sim$8$^{\prime\prime}$, while a smaller $\sim$6$^{\prime\prime}$.9 size is observed in K, PAH and nbL bands. The 3.28 $\mu$m emission indicates presence of PAHs at about 6000 and 5000 AU from the central stars in NGC 7027 and BD $+$30$^{\circ}$ 3639 respectively. Analysis suggests domination of neutral PAHs in BD $+$30$^{\circ}$ 3639, while in NGC 7027 there is higher ionization and more processed PAH population.

    • Observations with the 3.6-meter Devasthal optical telescope

      RAM SAGAR BRIJESH KUMAR SAURABH SHARMA

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      The 3.6-meter Indo–Belgian Devasthal optical telescope (DOT) has been used for optical and nearinfrared (NIR) observations of celestial objects. The telescope has detected stars of $B=24.5 \pm 0.2$, $R = 24.6 \pm 0.12$ and $g= 25.2 \pm 0.2$ mag in exposure times of 1200, 4320 and 3600 s respectively. In one hour of exposure time, a distant galaxy of $24.3 \pm 0.2$ mag and point sources of $\sim$25 mag have been detected in the SDSS $i$ band. The NIR observations show that stars up to $J = 20\pm 0.1$, $H = 18.8 \pm 0.1$ and $K = 18.2 \pm 0.1$ mag can be detected in effective exposure times of 500, 550 and 1000 s respectively. The $nbL$ band sources brighter than $\sim$9.2 mag and strong ($\geq$0.4 Jy) $PAH$ emitting sources like Sh 2-61 can also be observed with the 3.6-meter DOT. A binary star with angular separation of 0:$''$4 has been resolved by the telescope. Sky images with sub-arcsec angular resolutions are observed with the telescope at wavelengths ranging from optical to NIR for a good fraction of observing time. The on-site performance of the telescope is found to be at par with the performance of other, similar telescopes located elsewhere in the world. Owing to the advantage of its geographicallocation, the 3.6-meter DOT can provide optical and NIR observations for a number of frontline galactic and extra-galactic astrophysical research problems, including optical follow-up of GMRT and AstroSat sources and optical transient objects.

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      Posted on January 27, 2016

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      Posted on July 25, 2019

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