Gajendra Pandey

Photospheric Helium Abundance in Cool Giants: A Comprehensive Study

B. P. Hema, Gajendra Pandey

Abstract High-resolution optical spectra of 16 red giants, two early asymptotic giant branch (AGB) stars, and two supergiants, having no/minimal - to super-lithium (Li)-rich abundances, are analyzed to investigate the helium (He)-enhancement. The spectra of eight giants were obtained from the Himalayan …

Photospheric Helium Abundance in Cool Giants -- A Comprehensive Study

B. P. Hema, Gajendra Pandey

High-resolution optical spectra of sixteen red giants, two early asymptotic giant branch (AGB) stars, and two supergiants, having no/minimal to super lithium (Li)-rich abundances, are analyzed to investigate the helium (He)-enhancement. The spectra of eight giants were obtained from the Himalayan Chandra …

in (code pays fourni par la source)

Stars and stellar populations in Milky Way and the nearby galaxies

T. Sivarani, Smitha Subramanian, Avrajit Bandyopadhyay, Projjwal Banerjee et autres

in, us, au, de, cl (code pays fourni par la source)

Detection of Enhanced Germanium in a New Cool Extreme Helium Star A980: Insights and Implications

Ajay Kumar Saini, Gajendra Pandey

Abstract A fine abundance analysis of a recently discovered hydrogen-deficient carbon (HdC) star, A980, is presented. Based on the observed high-resolution optical spectrum, we ascertain that A980 is a cool extreme helium (EHe) star and not an HdC star. Singly ionized germanium …

Detection of Enhanced Germanium in a New Cool Extreme Helium Star A 980: Insights and Implications

Ajay Kumar Saini, Gajendra Pandey

A fine abundance analysis of a recently discovered hydrogen-deficient carbon (HdC) star, A 980, is presented. Based on the observed high-resolution optical spectrum, we ascertain that A 980 is a cool extreme helium (EHe) star and not an HdC. Singly-ionized germanium Ge …

Helium Abundance of the Sun: A Spectroscopic Analysis

Satyajeet Moharana, B. P. Hema, Gajendra Pandey

Abstract Determining the He/H ratio in cool stars presents a fundamental astrophysical challenge. While this ratio is established for hot O and B stars, its extrapolation to cool stars remains uncertain due to the absence of helium lines in their observed spectra. …

Helium Abundance of the Sun: A Spectroscopic Analysis

Satyajeet Moharana, B. P. Hema, Gajendra Pandey

Determining the He/H ratio in cool stars presents a fundamental astrophysical challenge. While this ratio is established for hot O and B stars, its extrapolation to cool stars remains uncertain due to the absence of helium lines in their observed spectra. We …

in (code pays fourni par la source)

Measuring Hydrogen-to-Helium Ratio in Cool Stars

B. P. Hema, Gajendra Pandey

Conventionally, the helium-to-hydrogen ratio for the stars are adopted to be 0.1, as standard, unless, the stars are severely deficient in hydrogen like in RCB-class, or the stars' helium abundance is accurately measured using He I transitions in warm/hotter stars. In our …

Measuring Hydrogen-to-Helium Ratio in Cool Stars

B. P. Hema, Gajendra Pandey

Conventionally, the helium-to-hydrogen ratio for the stars are adopted to be 0.1, as standard, unless, the stars are severely deficient in hydrogen like in RCB-class, or the stars’ helium abundance is accurately measured using He I transitions in warm/hotter stars. In our …

in (code pays fourni par la source)

The development of HISPEC for Keck and MODHIS for TMT: science cases and predicted sensitivities

Quinn Konopacky, Ashley Baker, Dimitri Mawet, Michael P. Fitzgerald et autres

HISPEC is a new, high-resolution near-infrared spectrograph being designed for the W.M. Keck II telescope. By offering single-shot, R 100,000 spectroscopy between 0.98 – 2.5 μm, HISPEC will enable spectroscopy of transiting and non-transiting exoplanets in close orbits, direct high-contrast detection and …

us, jp, ca (code pays fourni par la source)

The development of HISPEC for Keck and MODHIS for TMT: science cases and predicted sensitivities

Quinn Konopacky, Ashley Baker, Dimitri Mawet, Michael P. Fitzgerald et autres

HISPEC is a new, high-resolution near-infrared spectrograph being designed for the W.M. Keck II telescope. By offering single-shot, R=100,000 between 0.98 - 2.5 um, HISPEC will enable spectroscopy of transiting and non-transiting exoplanets in close orbits, direct high-contrast detection and spectroscopy of …

UOCS-IX. AstroSat/UVIT Study of the Open Cluster NGC 2818: Blue Stragglers, Yellow Stragglers, Planetary Nebula, and their Membership

Sharmila Rani, Gajendra Pandey, Annapurni Subramaniam, N. Kameswara Rao

Abstract We present the first far-UV (FUV) imaging results of the intermediate-age Galactic open cluster NGC 2818 that has a planetary nebula (PN) within the field using images taken from the Ultra Violet Imaging Telescope (UVIT) aboard AstroSat. We identify cluster members …

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