ASASSN-17hb and ASASSN-17he: Discovery of Two Probable Supernovae
ATel #10463; J. Brimacombe (Coral Towers Observatory), G. Bock (Runaway Bay Observatory, Australia), J. M. Fernandez (Observatory Inmaculada del Molino), S. Kiyota (Variable Star Observers League in Japan), J. S. Brown, K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, J. Shields, T. A. Thompson (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, S. Bose, Ping Chen (KIAA-PKU), P. Cacella (DogsHeaven Observatory), B. Nicholls (Mt. Vernon Obs., New Zealand), R. S. Post (Post Astronomy), G. Stone (Sierra Remote Observatories)
on 5 Jun 2017; 16:24 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Jonathan Brown (firstname.lastname@example.org)
Subjects: Optical, Supernovae, Transient
Referred to by ATel #: 10517
During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014), using data from the quadruple 14-cm "Cassius" telescope in Cerro Tololo, Chile, we discovered two new transient sources, most likely supernovae, in the galaxies UGC 00757 and NGC 2993.
ASASSN-17hb (AT 2017ejw) was discovered in images obtained on UT 2017-05-31.42 at V~16.0 mag. An image obtained on 2017-05-31 by J. Brimacombe confirms the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the J. Brimacombe confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the J. Brimacombe image.
The position of ASASSN-17hb is approximately 7.0" South and 7.8" East from the center of the galaxy UGC 00757 (z=0.019117, d=75.2 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.4 (m-M=34.34, A_V=0.095). Follow-up observations reported in ATEL #10454 classify the object as a Type Ia SN approximately 1 day before max.
ASASSN-17he (AT 2017ejx) was discovered in images obtained on UT 2017-05-30.05 at V~16.6 mag. An image obtained on 2017-05-30 by J. Brimacombe confirms the discovery of the transient. This figure shows the archival Pan-STARRS (Chambers et al. 2016, arXiv:1612.05560) g-band image of the host (left) and the J. Brimacombe confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the J. Brimacombe image.
The position of ASASSN-17he is approximately 0.3" North and 0.5" East from the center of the galaxy NGC 2993 (z=0.008106, d=38.3 Mpc, via NED), giving an absolute V-band magnitude of approximately -16.5 (m-M=32.89, A_V=0.166). Properties of the new sources and photometry are summarized in the tables below:
Object RA (J2000) DEC (J2000) Disc. UT Date Disc. V mag Approx. Abs. Mag Offset from Host (")
ASASSN-17hb 01:12:34.197 +00:17:29.30 2017-05-31.42 16.0 -18.4 10.48
ASASSN-17he 09:45:48.363 -14:22:05.60 2017-05-30.05 16.6 -16.5 0.58
Obs. UT Date V mag
Obs. UT Date V mag
Follow-up observations are encouraged.
While we are participating in the TNS system to minimize potential confusion, ASAS-SN will continue using ASASSN-17xx 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-17xx (AT 2017xyz) 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, and the Chinese Academy of Sciences South America Center for Astronomy (CASSACA). For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.