भारतीय खगोलभौतिकी संस्थान
Indian Institute of Astrophysics
Exploring the Universe since 1786
An Autonomous Institute under the
Department of Science & Technology
Government of India
Research Highlights
RESEARCH HIGHLIGHTS | IIA
High-resolution spectral analysis of three high-latitude carbon stars
ARUNA GOSWAMI | Apr 28, 2025
We present the results of a detailed high-resolution spectroscopic analysis (SUBARU/HDS spectra, R ∼50,000) of three faint high-latitude carbon stars HE 1104 − 0957, HE 1205 − 0521, and HE 1244 − 3036. Our estimated metallicity for these objects is − 2.96, − 2.63, and − 2.49, respectively. The surface chemical compositions of the objects are found to be characterised by enhanced carbon and heavy elements, such as Y, Ba, La, and Ce. Using the classification criteria for carbon-enhanced metal-poor (CEMP) stars the objects HE 1104 − 0957 and HE 1205 − 0521 could not be classified into any known CEMP sub-classes, whereas the object HE 1244 − 3036 is found to be likely a CEMP-s star. The observed abundance patterns in HE 1244 − 3036 are also found to match well with the yields of a 2 M ⊙ AGB star with [Fe/H] = − 2.50. Although our kinematic analysis indicates that the objects belong to the halo population, the elemental abundance ratios of HE 1104 − 0957 and HE 1205 − 0521 do not match well with those of typical halo objects. Estimated elemental abundances are presented, and kinematic properties of the stars are discussed.
RESEARCH HIGHLIGHTS | IIA
A compilation of optical starlight polarization catalogs
ARCHANA SOAM | Jan 01, 2025
Polarimetry of stars at optical and near-infrared wavelengths is an invaluable tool for tracing interstellar dust and magnetic fields. Recent studies have demonstrated the power of combining stellar polarimetry with distances from the Gaia mission, in order to gain accurate, 3D information on the properties of the interstellar magnetic field and the dust distribution. However, access to optical polarization data is limited, as observations are conducted by different investigators, with different instruments, and are made available in many separate publications. To enable a more widespread accessibility of optical polarimetry for studies of the interstellar medium, we compile a new catalog of stellar polarization measurements. The data are gathered from 81 separate publications spanning two decades since the previous, widely used agglomeration of catalogs by C. Heiles. The compilation contains a total of 55,742 measurements of stellar polarization. We combine this database with stellar distances based on the Gaia Early Data Release 3, thereby providing polarization and distance data for 42,482 unique stars. We provide two separate data products: an extended catalog (containing all polarization measurements) and a unique source catalog (containing a subset of sources excluding duplicate measurements). We propose the use of a common tabular format for the publication of stellar polarization catalogs to facilitate accessibility and increase discoverability in the future
RESEARCH HIGHLIGHTS | IIA
Mining the GALAH Data. I. Study of Five Super Lithium-rich Metal-poor Giants
SUSMITHA, A | May 01, 2024
The presence of a large amount of Li in giants is still a mystery. Most of the super Li-rich (SLR) giants reported in recent studies are in the solar metallicity regime. Here, we study the five metal-poor SLRs from the Galactic Archeology with HERMES Data Release 3, with their [Fe/H] ranging from −1.35 to −2.38 with lithium abundance of A(Li) 3.4 dex. The asteroseismic analysis reveals that none are on the red giant branch. The average period spacing (ΔP ) values indicate giants are in the core He-burning phase. All of them are low-mass giants (M < 1.5 Me). Their location in the Hertzsprung–Russell diagram suggests one of them is in the red clump (RC) phase, and interestingly, the other four are much brighter and coincide with the early asymptotic giant branch phase. The analysis of the abundance reveals that C, O, Na, Ba, and Eu are normal in giants of respective metallicities and evolutionary phases. Further, we did not find any strong evidence of the presence of dust in the form of infrared excess or binarity from the available radial velocity data. We discuss a few scenarios for the existence of SLRs at higher luminosity, including past merger events. Our findings will help in understanding the production and evolution of Li among giants, in particular, during the RC phase and the post-RC phase.
Press Releases
PRESS RELEASES | SCOPE
IIA Bengaluru scientists discover a new kind of Stellar Chemistry
SCOPE | Jun 19, 2025
Far away in the Ophiuchus Constellation, a peculiar star named A980, 25800 light years away, is rewriting what we know about stellar chemistry. Researchers have uncovered a cosmic twist -- this mysterious star that belongs to a rare class called Extreme Helium (EHe) stars, carries surprisingly high amount of germanium—a metallic element never before observed in this type of star.
This is based on the paper titled "Detection of Enhanced Germanium in a New Cool Extreme Helium Star A980: Insights and Implications", by Ajay Kumar Saini and Gajendra Pandey, 2025, The Astrophysical Journal, 979, 239.
Press release by PIB published here.
Press release issued by DST here.
PRESS RELEASES | SCOPE
Solar blasts that lit up Ladakh Skies May last year uncoded
SCOPE | Jul 16, 2025
A new study by IIA astronomers has revealed crucial insights into how multiple successive solar blasts known as Coronal Mass Ejections (CMEs) have interacted with each other and evolved thermally en route from the Sun to Earth. This occurrence triggered the most intense space weather event in the last two decades, which was observed on 10th May 2024. These findings offer a major step forward for improving space weather forecasting models, particularly in predicting the impact of complex CME events on Earth's magnetosphere.
This is based on the paper titled "Evolution of the interacting coronal mass ejections that drove the great geomagnetic storm of 10 May 2024", by Soumyaranjan Khuntia, Wageesh Mishra, and Anjali Agarwal, 2025, Astronomy and Astrophysics, 698, A79.
Press release by PIB published here.
Press release issued by DST here.
Download the paper from here.
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IIA offers a vigorous programme of graduate studies that forms a vital component of research & training. The programme is overseen by the board of graduate studies. The Institute is also a major partner in the Joint Astronomy Programme (JAP), organized by the Indian Institute of Science.
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PhD applications may be submitted through the IIA PhD online applications portal in May. After the initial screening, shortlisted candidates will be interviewed in June. The final list of selected candidates will be announced in July, followed by the commencement of the programme in August. .
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Studies of the Sun and solar system have been the longest pursued discipline at IIA. Members of the group conduct theoretical, numerical modeling, and observational studies in solar physics.
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Research interests of the group members range from exoplanets, star formation, stellar evolution, end states of stars, Interstellar medium, the milky way Galaxy, nearby galaxies, active galaxies and time domain astronomy.
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Members of the theoretical Astrophysics group work on a broad range of topics such as black hole astrophysics, pulsars, exoplanets, astrophysical turbulence & magnetic fields, MHD, cosmology and early universe.
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