ASASSN-17ej and ASASSN-17em: Discovery of Two Probable Supernovae
ATel #10241; G. Stone (Sierra Remote Observatories), W. Wiethoff (University of Minnesota, Duluth), R. S. Post (Post Astronomy), S. Kiyota (Variable Star Observers League in Japan), J. Brimacombe (Coral Towers Observatory), 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), J. M. Fernandez (Observatory Inmaculada del Molino), G. Krannich (Roof Observatory Kaufering)
on 3 Apr 2017; 19:56 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Jonathan Brown (brown@astronomy.ohio-state.edu)
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 "Brutus" telescope in Haleakala, Hawaii, we discovered two new transient sources, most likely supernovae, in the galaxies 2MASX J14075270+0938281 and CGCG 299-048 NED01.
ASASSN-17ej (AT 2017cpu) was discovered in images obtained on UT 2017-04-01.47 at V~18.1 mag. We do not detect (V>18.1) the object in images taken on UT 2017-03-24.49 and before. Follow-up images obtained on 2017-04-02 confirm the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the R. Post confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the R. Post image.
The position of ASASSN-17ej is approximately 2.8" North and 2.8" West from the center of the galaxy 2MASX J14075270+0938281 (z=0.054411, d=237 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.7 (m-M=36.75, A_V=0.076).
ASASSN-17em (AT 2017cts) was discovered in images obtained on UT 2017-04-02.46 at V~17.0 mag. We do not detect (V>17.8) the object in images taken on UT 2017-03-26.53 and before. Follow-up images obtained on 2017-04-03 confirm the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the R. Post confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the R. Post image.
The position of ASASSN-17em is approximately 11.4" South and 15.0" East from the center of the galaxy CGCG 299-048 NED01 (z=0.019760, d=82 Mpc, via NED), giving an absolute V-band magnitude of approximately -17.6 (m-M=34.53, A_V=0.085). 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-17ej 14:07:52.526 +09:38:31.37 2017-04-01.47 18.1 -18.7 3.96
ASASSN-17em 17:03:11.757 +61:27:26.07 2017-04-02.46 17.0 -17.6 18.84
ASASSN-17ej photometry:
Obs. UT Date V mag
2017-03-24.49 >18.1
2017-03-27.52 18.0
2017-04-01.47 18.1
ASASSN-17em photometry:
Obs. UT Date V mag
2017-03-26.53 >17.8
2017-04-02.46 17.0
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 Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, the Chinese Academy of Sciences South America Center for Astronomy (CASSACA), and the Mt. Cuba Astronomical Foundation. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.
