Spectroscopic classification of AT 2026aabo as a bright nova in M31
ATel #18029; Shatakshi Chamoli (IIA), Judhajeet Basu (IITB), Sudhanshu Barway (IIA), G. C. Anupama (IIA), Tanishk Mohan (IITB), Aditya Pawan Saikia (IITB), Vishwajeet Swain (IITB), Sameer Patil (IITB), Varun Bhalerao (IITB), Srikanth Bandari (IIA)
on 3 Sep 2026; 07:45 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Judhajeet Basu (judhajeet.basu@iiap.res.in)
Subjects: Optical, Nova, Transient
We report the spectroscopic classification of AT 2026aabo as a very bright and slowly evolving nova in M31.
This transient was first discovered on 2026-08-29T09:28:57 by ZTF Collaboration and reported on TNS at 18.57 mags in the ZTF-g band. ATLAS observations of this object were reported in ATel #18027. Our subsequent monitoring with the 70cm GROWTH-India Telescope (GIT) showed that the object brightened to 15.3 +/- 0.01 in g band on 2026-08-31T23:21:19, an increase of more than 3.5 mags in less than 3 days. Latest GIT photometry shows a g-band mag of 15.05 +/- 0.01 on 2026-09-02T16:46:30. The luminosity and rising light curve of AT2026aabo resemble the luminous M31 nova 2007-11d.
We obtained two spectra with HFOSC instrument on the 2-m Himalayan Chandra Telescope (HCT). We obtained two exposures each with grism-7 and -8 on 2026-09-01 and 2026-09-02 with exposure time of 1800s and 2700s on each day. The spectra show a systematic shift of around 300 km/s consistent with the velocity of M31, confirming the host of this transient. Both spectra show prominent FeII multiplet and P-Cygni Balmer features indicative of nova at its photometric maximum. Based on these observations, we conclude that AT2026aabo is a nova in M31 in its FeII phase.
Photometric and spectroscopic follow-up of the object is encouraged. We will continue monitoring this transient using facilities at IAO.
We thank the HCT observers for taking the time to carry out the ToO observation.
GIT 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/.
