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
Exploring the disc-jet scenario in 3C 273 using simultaneous XMM-Newton and NuSTAR observations
SANTANU MONDAL | Mar 12, 2025
The well-studied active galactic nucleus (AGN) 3C 273 displays characteristics of both jetted-AGNs and Seyfert galaxies, which makes it an excellent source to study the disc-jet connection in AGNs.
Aims. We aim to investigate the disc-jet scenario in 3C 273 using broad-band (0.3–78 keV) X-ray spectra from XMM-Newton and NuSTAR.
Methods. We used simultaneous XMM-Newton and NuSTAR observations of 3C 273 carried out between 2012 and 2024. The 0.3–78 keV X-ray spectra were first fitted with a simple power law (PL) and then with the accretion-ejection-based JeTCAF model. The JeTCAF model accounts for emission from the jet, which extends up to the sonic surface. In this framework, a reflection hump above 10 keV can also arise due to the bulk motion Comptonization of coronal photons by the jet.
Results. We find that the simple PL did not provide a good fit, leaving significant residuals at energies below 1.5 keV. All the spectra were fitted well by the JeTCAF model. The weighted-averaged black hole mass of (7.77 ± 0.30) × 108 M⊙ obtained from the JeTCAF model is comparable with the previous estimates based on reverberation mapping observations and accretion disc models.
Conclusions. The 0.3–78 keV X-ray emission of 3C 273 can be fit by the accretion-ejection-based model in which the corona and the jet on top of it make significant contributions to the X-ray flux. The Doppler boosting factor estimated from the jet flux ranges from 1.6 to 2.2, consistent with the lower limit from the literature.
RESEARCH HIGHLIGHTS | IIA
Quiet Sun Ellerman bombs as a possible proxy for reconnection-driven spicules
JAYANT JOSHI | May 20, 2025
Context. Spicules are elongated, jet-like structures that populate the solar chromosphere and are rooted in the lower solar atmosphere. In recent years, high-resolution observations and advanced numerical simulations have provided insights into their properties, structures, and dynamics. However, the formation mechanism of spicules, particularly the more dynamic type II spicules, which are primarily found in the quiet Sun and coronal holes, remains elusive. Aims. This study explores whether quiet Sun Ellerman bombs (QSEBs), which are ubiquitous small-scale magnetic reconnection events in the lower atmosphere, are linked to the formation of type II spicules. Methods. We analysed a high-quality 40-minute time sequence acquired with the Swedish 1-m Solar Telescope. Hβ data were used to observe QSEBs and spicules, while spectropolarimetric measurements in the photospheric Fe I 6173 Å line provided line-of-sight magnetic field information. We employed k-means clustering to automatically detect QSEBs and explored their potential association with spicules. Results. We identified 80 clear cases in which spicules occurred soon after the QSEB onset and not later than 30 s after the ending of the QSEBs. In all these instances, the events involved type II spicules, rapidly fading from the images. The footpoints of the spicules seemed to be rooted in QSEBs, where the onset of QSEBs often preceded the formation of the associated spicules. In addition to these clear cases, we found around 500 other events that hinted at a connection but with some ambiguities. The combined clear and ambiguous cases constitute 34% of the total detected QSEBs and a smaller percentage of the spicules in our dataset. Conclusions. Our findings suggest that a fraction of the type II spicules originate from QSEBs, supporting magnetic reconnection as a potential driving mechanism. In this context, QSEBs and spicules represent the conversion of magnetic energy into thermal and kinetic energy, respectively. We suggest that an observational programme including multiple Balmer lines would likely detect more unambiguous connections between QSEBs and spicules.
RESEARCH HIGHLIGHTS | IIA
A Multiwavelength Autopsy of the Interacting Type IIn Supernova 2020ywx: Tracing Its Progenitor Mass-loss History for 100 Yr Before Death
ARKAPRABHA SARANGI | Apr 20, 2025
While the subclass of interacting supernovae (SNe) with narrow hydrogen emission lines (Type IIn supernovae (SNe IIn)) consists of some of the longest-lasting and brightest supernovae (SNe) ever discovered, their progenitors are still not well understood. Investigating SNe IIn as they emit across the electromagnetic spectrum is the most robust way to understand the progenitor evolution before the explosion. This work presents X-ray, optical, infrared, and radio observations of the strongly interacting Type IIn supernova, SN 2020ywx, covering a period >1200 days after discovery. Through multiwavelength modeling, we find that the progenitor of 2020ywx was losing mass at ∼10−2–10−3 M⊙ yr−1 for at least 100 yr pre-explosion using the circumstellar medium (CSM) speed of 120 km s−1 measured from optical and near-infrared (NIR) spectra. Despite the similar magnitude of mass loss measured in different wavelength ranges, we find discrepancies between the X-ray and optical/radio-derived mass-loss evolution, which suggest asymmetries in the CSM. Furthermore, we find evidence for dust formation due to the combination of a growing blueshift in optical emission lines and NIR continuum emission which we fit with blackbodies at ∼1000 K. Based on the observed elevated mass loss over more than 100 yr and the configuration of the CSM inferred from the multiwavelength observations, we invoke binary interaction as the most plausible mechanism to explain the overall mass-loss evolution. SN 2020ywx is thus a case that may support the growing observational consensus that SNe IIn mass loss is explained by binary interaction.
Press Releases
PRESS RELEASES | SCOPE
A new method to reliably estimate Helium abundance in the Sun
SCOPE | Apr 24, 2025
Since Helium does not produce any observable spectral lines from the visible surface, or the photosphere, of the Sun, its abundance has usually been estimated through indirect means. In a recent study, the abundance of Helium in our Sun has been estimated accurately using the Magnesium and Carbon features in the observed high-resolution spectrum of the Sun.
This is based on the paper titled "Helium Abundance of the Sun: A Spectroscopic Analysis", by Satyajeet Moharana, B. P. Hema, and Gajendra Pandey, 2024, Astrophysical Journal, 974, 2.
Press release by PIB published here.
Press release issued by DST here.
Download the paper from here.
PRESS RELEASES | SCOPE
Scientists Chart the Sun's Subsurface Weather Patterns Tied to Its 11-Year Activity Cycle
SCOPE | Apr 29, 2025
An international team of solar physicists has unveiled new insights into the dynamic "inner weather" of the Sun—plasma currents just beneath its surface that pulse in step with its 11-year sunspot cycle. In a study published on the 22nd of April 2025, in the The Astrophysical Journal Letters, researchers from the Indian Institute of Astrophysics (IIA), Stanford University (USA), and the National Solar Observatory (NSO, USA) have traced how these hidden flows shift over time, potentially reshaping our understanding of how the Sun's interior connects to its outer magnetic behavior, which has far-reaching influence on space weather and Earth.
This is based on the paper titled "Solar Cycle Variations in Meridional Flows and Rotational Shear within the Sun's Near-surface Shear Layer", by Anisha Sen, S. P. Rajaguru, Abhinav Govindan Iyer, Ruizhu Chen, Junwei Zhao, and Shukur Kholikov, 2025, Astrophysical Journal Letters, 984, 1.
Press release by PIB published here.
Press release issued by DST here.
Download the paper from here.
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.
Upcoming Events
Study at IIA
PhD Programme
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.
Admissions
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.
Notice Board
Tenders, Technically Qualified Vendors & e-Auction Notices | GSTIN: 29AABTI0567R1ZZ
Job Opportunities
Galleries
INTERNATIONAL DAY OF YOGA | 2025
IAO HANLE
INTERNATIONAL DAY OF YOGA | 2025
IAO HANLE
INTERNATIONAL DAY OF YOGA | 2025
IAO HANLE
INTERNATIONAL DAY OF YOGA | 2025
IAO HANLE
INTERNATIONAL DAY OF YOGA | 2025
IAO HANLE
INTERNATIONAL DAY OF YOGA | 2025
IAO HANLE
INTERNATIONAL DAY OF YOGA | 2025
IAO HANLE
INTERNATIONAL DAY OF YOGA | 2025
IAO HANLE
INTERNATIONAL DAY OF YOGA | 2025
CREST Hoskote
INTERNATIONAL DAY OF YOGA | 2025
CREST Hoskote
INTERNATIONAL DAY OF YOGA | 2025
CREST Hoskote
INTERNATIONAL DAY OF YOGA | 2025
CREST Hoskote
INTERNATIONAL DAY OF YOGA | 2025
CREST Hoskote
INTERNATIONAL DAY OF YOGA | 2025
CREST Hoskote
INTERNATIONAL DAY OF YOGA | 2025
CREST Hoskote
INTERNATIONAL DAY OF YOGA | 2025
CREST Hoskote
INTERNATIONAL DAY OF YOGA | 2025
CREST Hoskote
INTERNATIONAL DAY OF YOGA | 2025
CREST Hoskote
INTERNATIONAL DAY OF YOGA | 2025
CREST Hoskote
INTERNATIONAL DAY OF YOGA | 2025
VBO Kavalur
INTERNATIONAL DAY OF YOGA | 2025
VBO Kavalur
INTERNATIONAL DAY OF YOGA | 2025
VBO Kavalur
INTERNATIONAL DAY OF YOGA | 2025
VBO Kavalur
INTERNATIONAL DAY OF YOGA | 2025
VBO Kavalur
INTERNATIONAL DAY OF YOGA | 2025
VBO Kavalur
INTERNATIONAL DAY OF YOGA | 2025
IIA Koramangala, Bengaluru
INTERNATIONAL DAY OF YOGA | 2025
IIA Koramangala, Bengaluru
INTERNATIONAL DAY OF YOGA | 2025
IIA Koramangala, Bengaluru
INTERNATIONAL DAY OF YOGA | 2025
IIA Koramangala, Bengaluru
INTERNATIONAL DAY OF YOGA | 2025
IIA Koramangala, Bengaluru
INTERNATIONAL DAY OF YOGA | 2025
IIA Koramangala, Bengaluru
INTERNATIONAL DAY OF YOGA | 2025
IIA Koramangala, Bengaluru
INTERNATIONAL DAY OF YOGA | 2025
IIA Koramangala, Bengaluru
INTERNATIONAL DAY OF YOGA | 2025
KSO, Kodaikanal.
INTERNATIONAL DAY OF YOGA | 2025
KSO, Kodaikanal.
INTERNATIONAL DAY OF YOGA | 2025
KSO, Kodaikanal.
INTERNATIONAL DAY OF YOGA | 2025
KSO, Kodaikanal.
INTERNATIONAL DAY OF YOGA | 2025
KSO, Kodaikanal.
View All »