Discovery of supernova candidate AT 2018cux in NGC 3256 by ePESSTO
E. Kankare (QUB), S. Taubenberger (ESO), C. Vogl (MPA), A. Floers (ESO), D. Malesani (DAWN, DARK), A. Rubin (WIS), C. Inserra (Southampton), K. Maguire (QUB), S. J. Smartt (QUB), O. Yaron (Weizmann), D. R. Young (QUB), E. Kool (Macquarie University/AAO), R. Kotak (Turku), J. Kotilainen (Turku), H. Kuncarayakti (Turku), S. Mattila (Turku), M. Perez-Torres (IAA-CSIC, Granada), Z. Randriamanakoto (University of Cape Town), T. Reynolds (Turku), C. Romero-Canizales (UDP), S. Ryder (AAO), P. Vaisanen (SAAO)
ePESSTO, the Public ESO Spectroscopic Survey for Transient Objects (see Smartt et al., arXiv:1411.0299 http://www.pessto.org ) reports the discovery of a supernova candidate in the galaxy NGC 3256 on 2018 March 24.2 UT, and confirmation imaging on 2018 April 7.2 UT. All observations were performed on the ESO New Technology Telescope at La Silla using EFOSC2. The transient was detected in images obtained during the follow-up of SN 2018ec (Kankare et al. 2018, ATel #11156; Berton et al. 2018, ATel #11160) via comparison with images obtained with EFOSC2 on 2018 January 17.2 UT. AT 2018cux is located at RA = 10:27:51.41 and Dec = -43:54:18.00 (J2000.0), which is 1.8" east and 4.0" south of the i-band nucleus of the host galaxy. Subtraction with the reference images yielded on 2018 March 24.2, m_g = 22.1 +/- 0.4, m_r = 20.9 +/- 0.2, m_i = 20.6 +/- 0.1, and m_z = 20.1 +/- 0.1 mag; and on 2018 April 7.2, m_g = 22.2 +/- 0.2, m_r = 20.8 +/- 0.3, m_i = 20.3 +/- 0.2, and m_z = 19.8 +/- 0.4 mag. Our most constraining non-detections are from NTT/EFOSC2 on 2018 March 9.3 UT, m_r > 21.8 mag; and on 2018 March 10.2 UT, m_z > 20.9 mag. The host is a luminous infrared galaxy at a Tully-Fisher distance of 37.4 Mpc (Tully 1988), with a high star formation rate and an estimated core-collapse supernova rate of ~1 SN/yr. Based on the optical colours, assuming a core-collapse supernova origin, the transient is likely obscured by a few magnitudes of extinction in optical bands.
optical,star,supernovae,transient