D. K. OJHA
Articles written in Journal of Astrophysics and Astronomy
Volume 10 Issue 1 March 1989 pp 113-118
Spectrophotometry observations of HR 8107
S. C. Joshi D. K. Ojha J. B. SrivaStava
HR 8107, a reported new Be star, has been observed spectrophotometrically. The energy distribution curve of the star has been compared with those of other stars of similar spectral and luminosity types and model atmospheres. On the basis of comparison with model atmospheres an effective temperature has been assigned to the star
Volume 12 Issue 3 September 1991 pp 213-223
On the shell star pleione (BU Tauri)
BU Tauri (Pleione) an interesting star in the Pleiades cluster, has been observed spectrophotometrically. The energy distribution curves of the star have been discussed vis a vis model atmospheres for normal stars in the appropriate range of temperature and effective gravity. The changes in the energy distribution curve noticed during our observations and previous observations taken from the literature have been pointed out. On the basis of the measured Há emission equivalent width, a rough estimate of the dimensions of the extended envelope of the star has been made.
Volume 21 Issue 1-2 June 2000 pp 53-59
Scale length of the galactic thin disk
This paper presents an analysis of the first 2MASS (The Two Micron All Sky Survey) sampler data as observed at lower Galactic latitude in our Galaxy. These new near-infrared data provide insight into the structure of the thin disk of our Galaxy, The interpretation of star counts and color distributions of stars in the near-infrared with the synthetic stellar population model, gives strong evidence that the Galactic thin disk density scale length,
Volume 21 Issue 1-2 June 2000 pp 77-90
Stellar sources in the isogal inner galactic bulge field (
D. K. Ojha A. Omont S. Ganesh G. Simon M. Schultheis
ISOGAL is a survey at 7 and 15 μm with ISOCAM of the inner galactic disk and bulge of our Galaxy. The survey covers ∼ 22 deg2 in selected areas of the central
Volume 41 All articles Published: 6 November 2020 Article ID 0027
RAHUL KUMAR ANAND SHANTANU RASTOGI BRIJESH KUMAR ARPAN GHOSH SAURABH SHARMA D. K. OJHA S. K. GHOSH
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.
Volume 41 All articles Published: 18 December 2020 Article ID 0050
Oxygen abundances of carbon-enhanced stellar population in the halo
A. SUSMITHA T. SIVARANI D. K. OJHA JOE P. NINAN A. BANDYOPADHYAY A. SURYA U. ATHIRA
The large fraction of carbon-enhanced metal-poor (CEMP) stars at lower metallicities makes them an interesting class of objects to be probed further in greater detail. They show different abundance patterns of neutron-capture elements and based on that CEMP stars are further divided into four categories.Abundances of C, N and O, along with other elements, are required to understand the different nucleosynthetic origins of the subclasses and their progenitors. We studied nine bright carbon-enhanced stars from the Milky Way halo in a metallicity range from $-$0.8 to $-$2.5. They show enhancement in C, N, O and Ba and exhibit radial velocity variation. This indicates the presence of a binary companion which might have contributed to the enhanced carbon and s-process abundance through mass transfer during its asymptoticgiant-branch (AGB) phase of evolution. Their abundance pattern of C, N and O favors low-mass nature for their binary companion.
Volume 44, 2023
All articles
Continuous Article Publishing mode
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