ASASSN-17ff and ASASSN-17fg: Discovery of Two Probable Supernovae in NGC 3506 and 2MASX J05003418-6204211

ATel #10301; J. Brimacombe (Coral Towers Observatory), B. Nicholls (Mt. Vernon Obs., New Zealand), G. Stone (Sierra Remote Observatories), I. Cruz (Cruz Observatory), T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, J. S. Brown, 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), G. Masi (Virtual Telescope Project, Ceccano, Italy), R. S. Post (Post Astronomy)
on 21 Apr 2017; 17:44 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@astronomy.ohio-state.edu)

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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 NGC 3506 and 2MASX J05003418-6204211.

ASASSN-17ff (AT 2017dfq) was discovered in images obtained on UT 2017-04-20.25 at V~16.4 mag. We also detect the object in images obtained on UT 2017-04-15.010 (V~16.9). We do not detect (V>17.0) the object in images taken on UT 2017-04-12.26 and before. An image obtained on 2017-04-21 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 4" and is centered on the position of the transient in the J. Brimacombe image.

The position of ASASSN-17ff is approximately 4.5" North and 0.9" West from the center of the galaxy NGC 3506 (z=0.021358, d=94.2 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.5 (m-M=34.87, A_V=0.057).

ASASSN-17fg (AT 2017dfv) was discovered in images obtained on UT 2017-04-19.910 at V~16.6 mag. We also detect the object in images obtained on UT 2017-04-13.03 (V~17.2). We do not detect (V>17.1) the object in images taken on UT 2017-04-11.02 and before. An image obtained on 2017-04-21 by J. Brimacombe confirms the discovery of the transient. This figure shows the archival DSS 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-17fg is approximately 6.6" North and 11.5" East from the center of the galaxy 2MASX J05003418-6204211, which has no redshift available in NED. Properties of the new source and photometry are summarized in the tables below: Properties of the new source 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-17ff  11:03:12.91   +11:04:40.53     2017-04-20.25      16.4          -18.5               4.59 
ASASSN-17fg  05:00:35.82   -62:04:14.36     2017-04-19.91      16.6           N/A               13.26 

ASASSN-17ff:

 
Obs. UT Date         V mag 
2017-04-12.26        >17.0 
2017-04-15.01         16.9 
2017-04-20.25         16.4 

ASASSN-17fg:

 
Obs. UT Date         V mag 
2017-04-11.02        >17.1 
2017-04-13.03         17.2 
2017-04-19.91         16.6 

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.