ASASSN-19acc: Discovery of A Bright Type IIn Supernova in the TESS Field

ATel #13326; P. Cacella (DogsHeaven Observatory), I. Cruz (Cruz Observatory), J. Brimacombe (Coral Towers Observatory, Australia), P. Vallely, K. Z. Stanek, C. S. Kochanek, C. M. Basinger, Z. Way, 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)
on 2 Dec 2019; 23:59 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Patrick Vallely (

Subjects: Optical, Supernovae, Transient

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014), using data from the quadruple 14-cm "Leavitt" telescope in Fort Davis, Texas, and the quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a bright supernova in the galaxy SDSS J195828.83+620824.3.

ASASSN-19acc (SN 2019vxm) was discovered in images obtained on UT 2019-12-01.04 at g~15.4 mag, and is recovered in several images obtained earlier. We do not detect (g>17.6) the object in images taken on UT 2019-11-19.14 and before. An image obtained on 2019-12-01 confirms the discovery of the transient. This figure shows the archival SDSS g-band image of the field (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-19acc is approximately 8.5" South and 2.1" West from the center of the galaxy SDSS J195828.83+620824.3. A classification spectrum obtained by Robin Leadbeater indicates that this is a Type IIn supernova at z~0.019. The transient lies within the Camera 4 field of the recently completed TESS Sector 18 observations per the Web TESS Viewing Tool. Sector 18 observations concluded on 2019-11-27, capturing the early rise of ASASSN-19acc, and the supernova will be further observed by TESS during Sectors 21 and 24. Properties of the new source and photometry are summarized in the tables below:

Object        RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. g mag  Approx. Abs. Mag   Offset from Host (") 
ASASSN-19acc  19:58:28.527   +62:08:15.80     2019-12-01.04      15.4            -19.4               8.8 
Obs. UT Date         g mag 
2019-11-19.14        >17.6 
2019-11-20.25         17.7 
2019-11-25.19         16.0 
2019-11-27.11         15.7 
2019-12-01.04         15.4 

Follow-up observations are strongly encouraged.

While we are participating in the TNS system to minimize potential confusion, ASAS-SN will continue using ASASSN-19xx 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-19xx (AT 2019xyz) 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.