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Discovery of supernova candidate AT 2018ec in NGC 3256 with HAWK-I/GRAAL

ATel #11156; E. Kankare (QUB), S. Mattila (Turku), S. Ryder (AAO), E. Kool (Macquarie University/AAO), R. Kotak (Turku), J. Kotilainen (Turku), H. Kuncarayakti (Turku), M. Perez-Torres (IAA-CSIC, Granada), Z. Randriamanakoto (University of Cape Town), T. Reynolds (Turku), C. Romero-Canizales (UDP), S. Smartt (QUB), P. Vaisanen (SAAO)
on 11 Jan 2018; 17:53 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Erkki Kankare (e.kankare@qub.ac.uk)

Subjects: Infra-Red, Supernovae

Referred to by ATel #: 11224, 11350

SUNBIRD, Supernovae UNmasked By Infra-Red Detection (see Kool et al. 2018, MNRAS, 473, 5641), reports the discovery of a supernova candidate AT 2018ec on Ks-band images of NGC 3256 as part of a near-infrared adaptive optics assisted search for highly obscured core-collapse supernovae in luminous infrared galaxies. The transient was detected in images obtained during the HAWK-I/GRAAL adaptive optics Science Verification run in the Tip-Tilt Star - free mode on the ESO Very Large Telescope on 2018 January 3.4 UT (FWHM ~ 0.4") and 2018 January 6.4 UT (FWHM ~ 0.3"), via comparison with archival SOFI Ks-band images obtained with the ESO New Technology Telescope on 2003 January 23.2 UT. AT 2018ec is located at RA = 10:27:50.77 and Dec = -43:54:06.3 (J2000.0), which is 5.2" west and 7.7" north from the Ks-band nucleus of the host galaxy. Subtraction with the reference imaging yielded 2018 January 3.4, m_K = 15.1 +/- 0.1 mag; 2018 January 6.4, m_K = 15.2 +/- 0.1 mag. Assuming a Tully-Fisher distance of 37.4 Mpc (Tully 1988) and Galactic line-of-sight extinction of A_K = 0.04 mag (Schlafly & Finkbeiner 2011, ApJ, 737, 103) this corresponds to an absolute magnitude of -17.8 mag, consistent with a fairly young supernova.