ASASSN-18sk: Discovery of A Bright Transient in the TESS Field
ATel #11964; J. Brimacombe (Coral Towers Observatory), P. Vallely, K. Z. Stanek, C. S. Kochanek, J. S. Brown, J. Shields, T. A. Thompson (Ohio State), B. J. Shappee (IfA-Hawaii), T. W.-S. Holoien (Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, S. Bose, Ping Chen (KIAA-PKU), M. Stritzinger, S. Holmbo (Aarhus), G. Bock (Runaway Bay Observatory, Australia)
on 17 Aug 2018; 17:51 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Patrick Vallely (vallely.7@osu.edu)
Subjects: Optical, Cataclysmic Variable, Supernovae
During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014), using data from the quadruple 14-cm "Payne-Gaposchkin" telescope in Sutherland, South Africa, we discovered a new transient source, most likely a supernova or CV, in the field currently being observed by TESS.
ASASSN-18sk (AT 2018fdx) was discovered in images obtained on UT 2018-08-15.93 at g~16.1 mag. We also detect the object in images obtained on 2018-08-14.97 (g~17.8). We do not detect (g>18.7) the object in images taken on UT 2018-08-14.32 and before. A follow-up image obtained on 2018-08-16 confirms the discovery of the transient. This figure shows the archival DSS image of the host (left) and the confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the confirmation image.
The position of ASASSN-18sk is consistent with a faint blue source in archival DSS images. Spectroscopic follow-up observations are needed to determine whether the new source is a CV or SN. The transient lies within the Camera 2 field of the ongoing TESS Sector 1 observations. Properties of the new source and photometry are summarized in the tables below:
Object RA (J2000) DEC (J2000) Disc. UT Date Disc. g mag Offset from Host (")
ASASSN-18sk 23:17:29.990 -49:48:00.94 2018-08-15.28 16.2 ---
Obs. UT Date g mag
2018-08-14.32 >18.7
2018-08-14.97 17.8
2018-08-15.93 16.1
Follow-up observations are encouraged.
While we are participating in the TNS system to minimize potential confusion, ASAS-SN will continue using ASASSN-18xx transient names as our primary nomenclature (including supernovae, but also other classes of transients), and we encourage others to do the same. We prefer merging the names as ASASSN-18xx (AT 2018xyz) to preserve, rather than anonymize, the origin of the transient.
We thank Las Cumbres Observatory and its staff for their continued support of ASAS-SN. ASAS-SN is funded in part by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University, NSF grant AST-1515927, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, the Chinese Academy of Sciences South America Center for Astronomy (CASSACA), and the Villum Fonden (Denmark). For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.
