An Autonomous Institute under the
Department of Science & Technology
Government of India
27th of June, 2026
SARANG SHAH | Oct 01, 2024
This study investigates orbital parallax in gravitational microlensing events, focusing on OGLE-2017-BLG-0103 and OGLE-2017-BLG-0192. For events with timescales ≤60 days, a Jerk-Parallax degeneracy arises due to high Jerk velocity (v˜j), causing a fourfold continuous parallax degeneracy. OGLE-2017-BLG-0103, after incorporating orbital parallax, reveals four discrete degenerate parallax solutions, while OGLE-2017-BLG-0192 exhibits four discrete solutions without degeneracy. The asymmetric lightcurve of OGLE-2017-BLG-0103 suggests a more probable model where Xallarap is added to the parallax model, introducing tension. The galactic model analysis predicts a very low-mass stellar lens for OGLE-2017-BLG-0192. For OGLE-2017-BLG-0103, degenerate solutions suggest a low-mass star or a darker lens in the disk, while the Xallarap+Parallax model also predicts a stellar lens in the bulge, with the source being a solar-type star orbited by a dwarf star. This study presents five degenerate solutions for OGLE-2017-BLG-0103, emphasizing the potential for confirmation through high-resolution Adaptive Optics observations with Extremely Large Telescopes in the future. The complexities of degenerate scenarios in these microlensing events underscore the need to analyze special single-lens events in the Roman Telescope Era.
LABANYA K. GUHA | Dec 01, 2025
A systematic search for H I 21 cm absorption in quasar─galaxy pairs (QGPs) provides a powerful means to map the distribution of cold gas around high-redshift star-forming galaxies. Fiber spectroscopy of high-redshift quasars enables the serendipitous detection of foreground star-forming galaxies at extremely small impact parameters, forming a unique subset of QGPs known as galaxies on top of quasars (GOTOQs). In this study, we present results from a pilot upgraded Giant Metrewave Radio Telescope survey of three GOTOQs, where we achieved a remarkable 100% detection rate of H I 21 cm absorption. By combining our findings with the existing literature, we establish that GOTOQs constitute a distinct population in terms of H I 21 cm absorption, with significantly higher detection rates than those observed in damped Lyα-based or metal absorption-based searches. For the GOTOQs, we find a strong correlation between the line-of-sight reddening and the H I 21 cm optical depth, characterized by ∫τdv(kms−1)=13.58−2.35+2.75E(B−V)+0.68−1.27+1.06 , consistent with the Milky Way sightlines. We also show that the H I 21 cm optical depth declines with the impact parameter, and find a tentative trend for the H I 21 cm detection rates to also decline with the impact parameter. With upcoming wide-field spectroscopic surveys expected to substantially expand the catalog of known GOTOQs, the success of this pilot survey lays the foundation for constructing a statistically significant sample of intervening H I 21 cm absorbers.
PIYALI CHATTERJEE | Aug 10, 2025
Spicules are thin, elongated, jet-like features seen in observations of the solar atmosphere, at the interface between the solar photosphere and the corona. These features exhibit highly complex dynamics and are a necessary connecting link between the cooler, denser solar chromosphere and the extremely hot, tenuous corona. In this work, we explore the spatial and temporal relation between solar spicules and magnetohydrodynamic (MHD) shocks using data from a 2D radiative MHD simulation of the solar atmosphere driven by solar convection. Here, we demonstrate, through direct identification, that slow MHD shocks, which propagate along magnetic field lines, are regions of strong positive vertical acceleration of the plasma that forms the tip of the spicule material during its rise phase. We quantify the effect of pressure and Lorentz forces on the acceleration of the plasma inside the shocks during the rise of spicules. The causality between spicule and shock propagation in the atmosphere of the model is also investigated. It is further shown that the strength of these shocks may play a vital role in determining the height of the spicules, supporting the idea that shocks act as drivers of some spicules. In addition, we also find the presence of structures similar to propagating coronal disturbances (PCDs) in the simulation, linked with the spicules. Here, PCDs appear to be associated with the shock waves driving the spicules that subsequently propagate into the corona and have similar speeds to those reported in observations.
SCOPE | Apr 17, 2026
A new study has probed the possibility of some of the smallest galaxies in the universe, particularly dwarf spheroidal galaxies orbiting the Milky Way, hosting black holes. This can help advancing our understanding of black hole formation and galaxy evolution across cosmic time.
This study was published in the Astrophysical Journal in a paper titled "Can Dwarf Spheroidal Galaxies Host a Central Black Hole?", and is authored by K. Aditya and Arun Mangalam of the Indian Institute of Astrophysics.
The PIB press release is here.
The DST press release is here.
The paper is here.
SCOPE | Jun 05, 2026
The Kodaikanal solar observatory, known for the oldest continuous series of solar data collected in India, have helped uncover how giant convection patterns on the Sun respond to solar activity, providing insights for future solar cycle prediction.
This study was published in the Astrophysical Journal Letters in a paper titled "Which Solar Latitude Follows the Sunspot Cycle Exactly?", and is authored by K.P. Raju of the Indian Institute of Astrophysics.
The PIB press release is here.
The DST press release is here.
The paper is here.
SCOPE | Jun 19, 2026
Astronomers have traced the mechanism behind a mysterious celestial non-repeating flash of X-ray called Fast X-ray Transients (FXTs) that was detected on November 7 last year. The study of the X-ray flash which they linked to collapse of a massive star or the merger of two neutron stars could help us better understand the physics of these extreme events.
This study was published in the Monthly Notices of the Royal Astronomical Society in a paper titled "Characterizing EP241107a: multiwavelength observations of an Einstein Probe-detected fast X-ray transient", and is authored by Deepak Eappachen, Arvind Balasubramanian, G. C. Anupama, D. K. Sahu and Sudhanshu Barway of the Indian Institute of Astrophysics, and Vishwajeet Swain, V. Bhalerao, Tanishk Mohan and G. Waratkar of the Indian Institute of Technology Bombay.
The PIB press release is here.
The DST press release is here.
The paper is here.
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.
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. .
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.
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.
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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