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
FLAME: Fitting Lyα absorption lines using machine learning
VIVEK, M | Aug 01, 2024
We introduce FLAME, a machine-learning algorithm designed to fit Voigt profiles to H I Lyman-alpha (Lyα) absorption lines using deep convolutional neural networks. FLAME integrates two algorithms: the first determines the number of components required to fit Lyα absorption lines, and the second calculates the Doppler parameter b, the H I column density NHI, and the velocity separation of individual components. For the current version of FLAME, we trained it on low-redshift Lyα forests observed with the far-ultraviolet gratings of the Cosmic Origin Spectrograph (COS) on board the Hubble Space Telescope (HST). Using these data, we trained FLAME on ∼106 simulated Voigt profiles – which we forward-modeled to mimic Lyα absorption lines observed with HST-COS – in order to classify lines as either single or double components and then determine Voigt profile-fitting parameters. FLAME shows impressive accuracy on the simulated data, identifying more than 98% (90%) of single (double) component lines. It determines b values within ≈ ± 8 (15) km s−1 and log NHI/cm2 values within ≈ ± 0.3 (0.8) for 90% of the single (double) component lines. However, when applied to real data, FLAME’s component classification accuracy drops by ∼10%. Nevertheless, there is reasonable agreement between the b and NHI distributions obtained from traditional Voigt profile-fitting methods and FLAME’s predictions. Our mock HST-COS data analysis, designed to emulate real data parameters, demonstrates that FLAME is able to achieve consistent accuracy comparable to its performance with simulated data. This finding suggests that the drop in FLAME’s accuracy when used on real data primarily arises from the difficulty in replicating the full complexity of real data in the training sample. In any case, FLAME’s performance validates the use of machine learning for Voigt profile fitting, underscoring the significant potential of machine learning for detailed analysis of absorption lines.
RESEARCH HIGHLIGHTS | IIA
Ultraviolet Background Radiation from Not-So-Dark Matter in the Galactic Halo
JAYANT MURTHY | May 03, 2025
Murthy et al. (2025) (hereafter Paper I) have recently reported the discovery of unexpectedly bright diffuse extreme-ultraviolet radiation at high latitudes in both the Northern and Southern Galactic Hemispheres. After correction for extinction by the total interstellar dust in the direction of each observation, the spectra are nearly identical, suggesting that the radiation has a unique source and likely originates in the halo of our galaxy. The observed spectrum extends down to 912 Å, the interstellar hydrogen absorption edge. Radiation even slightly short of that edge would, if ubiquitous, be sufficient to explain the high degree of ionization in our galaxy and throughout the universe. We hypothesize that this newly discovered radiation originates in the slow decay of dark matter. The intensity of the radiation implies that the decay cannot be via the weak interaction, suggesting the existence of a new, even weaker fundamental interaction, consistent with the exceedingly long decay lifetime required.
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.
Press Releases
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.
PRESS RELEASES | SCOPE
Indian Institute of Astrophysics Training Workshop at Kodaikanal and Kavalur for Total Lunar Eclipse
SCOPE | Aug 05, 2025
A total lunar eclipse is to occur on the night of 7-8 September 2025, which will be visible from all over India. IIA therefore organised two “Train the Trainers” Workshops during 2-3 August 2025, one at the Vainu Bappu Observatory in Kavalur, and the other at the Kodaikanal Solar Observatory in Kodaikanal. These workshops were to train science and astronomy communicators and teachers in Tamil Nadu and Puducherry so that they can in turn organise preparatory workshops and eclipse viewing camps in their neighbourhoods.
Link to PIB article here.
PRESS RELEASES | SCOPE
A new window into the stars by modeling stellar atmosphere
SCOPE | Aug 22, 2025
In a major advance in computational astrophysics, IIA astronomers and collaborators have developed a method to compute more realistic properties of stellar atmospheres. The method opens the door to more realistic simulations of stellar spectra — the primary tool astronomers use to decode the physical conditions in stars, circumstellar disks, and interstellar clouds.
This is based on the paper titled "Full non-LTE multi-level radiative transfer: I. An atom with three bound infinitely sharp levels", by Lagache T., Paletou, F., and Sampoorna, M., Astronomy and Astrophysics, 2025, 699, A198.
Press release by DST published here.
Press release by PIB published here.
Download the paper 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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