AstroSat Discovers Ultraviolet Nova Eruptions in Andromeda Galaxy | Bengaluru News

Novae detected in the Andromeda in UVIT’s FUV/NUV filter. (credit: DST)

BENGALURU: In a first, astronomers from the Indian Institute of Astrophysics (IIA) captured unprecedented ultraviolet images of nova eruptions in the Andromeda galaxy, revealing the dramatic life cycles of interacting binary star systems. Novae are a special class of transient astronomical event that causes the sudden appearance of a bright, apparently new star that slowly fades over weeks or months during their outburst.
Using the Ultraviolet Imaging Telescope (UVIT) onboard the AstroSat satellite, the research team detected UV emissions from 42 novae, with four of these stellar explosions caught in the act of outburst. This marks the first time that far UV emissions from novae were observed in our neighbouring galaxy, located 2.5 million light-years away.

Novae occur in binary star systems where a white dwarf—an Earth-sized but incredibly hot star—pulls matter from a companion star. As material accumulates on the white dwarf’s surface, extreme temperatures and pressures build up, eventually triggering a massive thermonuclear explosion that can brighten the system by several orders of magnitude.
The team, whose research is published in the Astrophysical Journal, consists of Judhajeet Basu (IIA and Pondicherry University), Krishnendu S (IIA and Amrita University), Sudhanshu Barway (IIA), Shatakshi Chamoli (IIA and Pondicherry University), and GC Anupama (IIA). IIA is an autonomous institution under the department of science and technology (DST).

As per DST, this could allow scientists to study these interacting binary star systems in our nearest neighbour galaxy at different phases of their life, some piling up matter from their companion, while others spewing it into space.
Basu, a PhD student at IIA who led the project, said tracing these novae was possible only because of the Andromeda survey proposals taken up by AstroSat UVIT operated by Isro. He added that more such future missions, especially in UV and X-ray, can discover and follow up these systems and could answer some of the missing puzzles of novae.
UVIT’s fine spatial resolution and unique capability to observe simultaneously in far UV and near UV helped the team investigate the fluxes in different UV bands, which led to the detection. “The brighter the disk, the more rapidly it is consuming its companion’s matter. We also studied how the flux from these discs changes with time, and as per our expectations, the accretion process was found to be stable in these systems,” Basu said.
Barway, a faculty member at IIA, said the UV outburst in novae is much like what happens in a fusion bomb, but on an “astronomical” scale. “This explosion naturally leads to the brightening of the system by several orders of magnitude, hurling large quantities of material into the interstellar medium. We serendipitously found four systems caught in this act,” Barway said.