Spectroscopic classification of AT 2023tkw (GIT230919aa) as a nova in Fe II phase
ATel #16311; Judhajeet Basu (IIA), Ravi Kumar (IITB), G. C. Anupama (IIA), Sudhanshu Barway (IIA), Varun Bhalerao (IITB), Vishwajeet Swain (IITB), Avinash Singh (Hiroshima U), Rishabh Singh Teja (IIA), Mulchand Kurre (IIA), Yogita Patel (IIA), Srikanth Bandari (IIA)
on 28 Oct 2023; 07:24 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Sudhanshu Barway (sudhanshu.barway@iiap.res.in)
AT 2023tkw (GIT230919aa) was discovered at a magnitude of 20.03 (AB) in the r' band during the daily monitoring of M31 by the GROWTH-India Telescope (GIT) on 19 September 2023 (Kumar R., 2023, TNSTR, 2023-2354; Kumar R. et al., 2023, TNSAN 2023-255). The object is located about 17 arcmins southwest of the nucleus of M31. Since its discovery, it has also been detected by other survey telescopes like Pan_STARRS (PS23iqu), ZTF (ZTF23aayatam), and ATLAS (ATLAS23twy).
We have been monitoring the object photometrically with the GIT and spectroscopically with the Himalayan Chandra Telescope (HCT). Low-resolution optical spectra were obtained on the 18th and 26th of October 2023, using the HFOSC instrument on HCT. The first epoch spectrum showed faint H Balmer features with a blue continuum. During the second epoch, the H Balmer lines had strengthened considerably, and lines due to He I (6678, 5876, 5016) and multiple Fe II lines between 5000-5500 A and 6000-6500 A were also present. The velocity width of the H alpha profile increased from ~ 780 km/s to ~ 1200 km/s in 8 days. Overall, the spectral features suggest that the object is most likely to be a nova in its Fe II phase. The optical light curve from GIT images suggests it to be a slowly evolving nova.
We will continue photometric and spectroscopic monitoring of this nova in M31.
The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. We thank the HCT observers for sparing time for the ToO observations. The 2m HCT is located at IAO.
