Thread by @Chethan_Dash

#Thread #Astronomy #Stars #UPDATE

An international team of scientists led by #Indian #astronomers has spotted a new member belonging to the extremely rare group of young stars that exhibit what's called episodic accretion. 1/n

Episodic accretion is a process where stars accrete via a disk from a more spherically distributed envelope which adds mass to the disk & makes it unstable on an irregular basis. Such instability dumps extra material onto the star & accretion rate & luminosity increase. 2/n

Indian astronomers from the @ARIESNainital as part of an international team, including from @TIFRScience and @IIABengaluru have discovered “Gaia 20eae”, the latest member of episodically accreting young stars, according to @IndiaDST . 3/n

Such rare stars — young, low-mass stars — have gained significant interest in the star-formation community lately and this study could help probe into this group of stars and their formation mechanism in greater detail. 4/n

The new research is published in ‘The Astrophysical Journal’ and provides an important test-bed to probe the various physical aspects of episodic accretion and their comparison with previously discovered sources. 5/n

On Aug 28, 2020, the Gaia Photometric Alert system — a sky survey which actively searches for the transient objects and publishes a daily report on the number of transients it detects — published a report stating Gaia 20eae has brightened by 4.5 magnitudes. 6/n

As per @IndiaDST, this “indicated a likely case of enhanced episodic accretion”. 7/n

Arpan Ghosh, PhD student with Saurabh Sharma (ARIES), Joe Ninan (@penn_state), DK Ojha (TIFR), BC Bhatt (IIA), others from @Princeton, @UofOklahoma, @JohnsHopkins, @UCBerkeley, @stsci; Nat’l Astronomical Research Institute-Thailand, Macquarie Univ began monitoring Gaia 20eae. 8/n

The team carried out simultaneous photometric (measurement of light in terms of its perceived brightness to the human eye) and spectroscopic (electromagnetic measurements) observations. 9/n

It did this using Indian facilities like the 1.3m Devasthal Fast Optical Telescope, 3.6m Devasthal Optical Telescope, 2m Himalayan Chandra Telescope, and international facilities like 10m HET telescope and 0.5m ARC Small Aperture Telescope. 10/n

The light curve of Gaia 20eae, it added, showed a transition stage when it exhibited most of its brightness at a short timescale of 34 days with a very rapid rising rate (3 mag/month); the star has now started to decay: @IndiaDST. 11/n

“The team detected strong signatures of outflowing winds generated due to accretion & presence of turbulence around Gaia 20eae. In a first-time discovery, it detected the signature of magnetospheric accretion (red-shifted absorption) component from high-resolution spectra… 12/n

…This was consistent with the signature of low-velocity in-fall of matter from the inner part of the surrounding disc onto the central pre-main sequence star as viewed from a hotter background,” the DST said. n/n