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
Deciphering the evolution of thermodynamic properties and their connection to the global kinematics of high-speed coronal mass ejections using FRIS model
SOUMYARANJAN KHUNTIA | Dec 01, 2024
Most earlier studies have been limited to estimating the kinematic evolution of coronal mass ejections (CMEs), and only limited efforts have been made to investigate their thermodynamic evolution. We focus on the interplay of the thermal properties of CMEs with their observed global kinematics. We implement the Flux rope Internal State model to estimate variations in the polytropic index, heating rate per unit mass, temperature, pressure, and various internal forces. The model incorporates inputs of 3D kinematics obtained from the Graduated Cylindrical Shell (GCS) model. In our study, we chose nine fast-speed CMEs from 2010 to 2012. Our investigation elucidates that the selected fast-speed CMEs show a heat-release phase at the beginning, followed by a heat-absorption phase with a near-isothermal state in their later propagation phase. The thermal state transition, from heat release to heat absorption, occurs at around 3( ± 0.3) to 7(± 0.7) R ⊙ for different CMEs. We found that the CMEs with higher expansion speeds experience a less pronounced sharp temperature decrease before gaining a near-isothermal state. The differential emission measurement (DEM) analysis findings, using multiwavelength observation from Solar Dynamics Observatory/Atmospheric Imaging Assembly, also show a heat release state of CMEs at lower coronal heights. We also find the dominant internal forces influencing CME radial expansion at varying distances from the Sun. Our study shows the need to characterize the internal thermodynamic properties of CMEs better in both observational and modeling studies, offering insights for refining assumptions of a constant value of the polytropic index during the evolution of CMEs
RESEARCH HIGHLIGHTS | IIA
Data processing of visible emission line coronagraph onboard ADITYA-L1
MUTHU PRIYAL | Jul 01, 2024
ADITYA-L1 is India's first dedicated mission to observe the Sun and its atmosphere from a halo orbit around L1 point. Visible emission line coronagraph (VELC) is the primary payload on board Aditya-L1 to observe the Sun’s corona. VELC is designed as an internally occulted reflective coronagraph to meet the observational requirements of wide wavelength band and the field of view close to the solar limb (1.05 R Sun ). Images of the solar corona in continuum and spectra in three emission lines 5303 Å [Fe xiv], 7892 Å [Fe xi] and 10747 Å [Fe xiii] obtained with high cadence are to be analyzed using software algorithms automatically. A reasonable part of these observations will be made in a synoptic mode in which the data are processed through a standard pipeline and the resulting products will be made available for public use. The procedure involves the calibration of instrument and detectors, converting the images into the FITS format, correcting the images and spectra for the instrumental effects, and aligning the images (in terms of position angles and image scales) etc. Then, develop image processing algorithms to detect the occurrence of energetic events using continuum images. Also derive physical parameters, such as temperature and velocity structure of solar corona using emission line observations. Here, we describe the calibration of detectors and the development of software algorithms to detect the occurrence of CMEs and analyze the spectroscopic data.
RESEARCH HIGHLIGHTS | IIA
SN 2019nyk: A rapidly declining Type II supernova with early interaction signatures
MRIDWEEKA SINGH | May 01, 2024
We present an optical photometric and spectroscopic analysis of the fast-declining hydrogen-rich Type II supernova (SN) 2019nyk. The light curve properties of SN 2019nyk align well with those of other fast-declining Type II SNe, such as SNe 2013by and 2014G. SN 2019nyk exhibits a peak absolute magnitude of −18.09 ± 0.17 mag in the V band, followed by a rapid decline at 2.84 ± 0.03 mag (100 d)−1 during the recombination phase. The early spectra of SN 2019nyk exhibit high-ionisation emission features as well as narrow H Balmer lines, persisting until 4.1 d since explosion, indicating the presence of circumstellar material (CSM) in close proximity. A comparison of these features with other Type II SNe displaying an early interaction reveals similarities between these features and those observed in SNe 2014G and 2023ixf. We also compared the early spectra to literature models, estimating a mass-loss rate of the order of 10−3 M⊙ yr−1. Radiation hydrodynamical modelling of the light curve also suggests the mass loss from the progenitor within a short period prior to explosion, totalling 0.16 M⊙ of material within 2900 R⊙ of the progenitor. Furthermore, light curve modelling infers a zero-age main sequence mass of 15 M⊙ for the progenitor, a progenitor radius of 1031 R⊙, and an explosion energy of 1.1 × 1051 erg.
Press Releases
PRESS RELEASES | SCOPE
Hanle Dark Sky Reserve star party brings together astronomy enthusiasts for the third year
SCOPE | Sep 26, 2025
Astronomy enthusiasts from across the country participated in amateur astronomy and astrophotography related activities at the third edition of the HDSR Star Party that was jointly organised by the Indian Institute of Astrophysics (IIA), Department of Wildlife Protection of UT Ladakh, and Bhabha Atomic Research Centre (BARC) between 18 and 23 September.
The PIB press release is here.
The DST press release is here.
PRESS RELEASES | SCOPE
Black holes and cosmic jets join forces to shape galaxies
SCOPE | Oct 21, 2025
Black hole activities suppress the birth of new stars around it, shows a new study that can help in a deeper understanding of how galaxies evolve and may provide answers to why some have very low star-formation rates.
This study was published in the Astrophysical Journal, titled “Warm Ionized Gas Outflows in Active Galactic Nuclei: What Causes Them?”, and is authored by Payel Nandi and C.S. Stalin from IIA and D.J. Saikia from IUCAA.
The PIB press release is here.
The DST press release is here.
The paper can be downloaded from here.
PRESS RELEASES | SCOPE
Astronomers unearth unexpected chemical link during stellar evolution
SCOPE | Nov 14, 2025
A new study has traced a link between Lithium-rich red giant stars and their enhanced Helium abundance, using data from the Himalayan Chandra Telescope and other archival data. The study gives a new lead to the evolution of cool giant stars along the red giant phase.
This study was published in The Astrophysics Journal as a paper titled "Photospheric Helium Abundance in Cool Giants: A Comprehensive Study", by B. P. Hema and Gajendra Pandey of IIA.
The PIB press release is here.
The DST press release is here.
The paper can be accessed 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. .
Research Fields
Solar Studies
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.
Stars & Galaxies
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.
Theory
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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