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SALT Spectroscopic classification of nuclear transients ASASSN-17fy and ASASSN-17dv/Gaia17bgr

ATel #10424; A. Hamanowicz, M. Gromadzki, L. Wyrzykowski (Warsaw University Astronomical Observatory, Poland), David Buckley (South African Astronomical Observatory)
on 25 May 2017; 13:17 UT
Credential Certification: Lukasz Wyrzykowski (wyrzykow@astrouw.edu.pl)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 10500

We report the spectroscopic classification of two nuclear transients: ASASSN-17fy and ASASSN-17dv/Gaia17bgr. The spectrum was obtained using the Robert Stobie Spectrograph (RSS) on the South African Large Telescope (SALT).
Both transients share similar spectral features which we find to resemble SN Type Ib/c SN2016ejf. Note that ASASSN-17fy was previously classified as SN Type IIn in ATel #10391. ASASSN-17fy exhibits narrow emission lines ([OII],Hbeta, HeI, SII) and Halpha with both narrow and broad components. ASASSN-17dv/Gaia17bgr has a narrow emission of [OII], Hbeta, [OIII] and SII and Halpha also has both narrow and broad emission. Additionally, ASASSN-17fy shows absorption lines of NaI at host and Milky Way redshifts, an indication of a significant extinction both in the host and from the Galaxy (low Galactic latitude).

Name | IAU name | RA (J2000) | Dec (J2000) | Disc. Date | Disc. Mag | Obs. Date | z | host | Notes
ASASSN-17fy | AT2017dwq | 09:03:32.20 | -21:20:07.48 | 2017-05-04 | 16.90 | 2017-05-19 | 0.018 | 2MASX J09033237-2120017 | ATEL #10358
ASSASN-17dv/Gaia17bgr | AT2017civ | 09:52:31.22 | -21:57:54.29 | 2017-03-22 | 17.81 | 2017-05-23 | 0.029 | GALEXASC J095231.21-215754.7 | ATEL #10226

ASASSN-17fy is located in one of the bright spots (possibly related to the nucleus of the galaxy) seen on archival PS1. The host is also clearly bright in UV in GALEX archive, indicating increased star formation. The host of the ASASSN-17dv/Gai16bgr is also UV bright. We conclude that the narrow emission lines, in both cases, originate from the host star formation, which also agrees with a detection of core-collapse supernovae in such environment.

We acknowledge ESA Gaia, DPAC and the Photometric Science Alerts Team (http://gsaweb.ast.cam.ac.uk/alerts).