Discovery of a 2008S-like transient in NGC 5775

ATel #4004; S. Howerton (Arkansas City, KS), J. Prieto (Princeton); A. J. Drake, S. G. Djorgovski, A. A. Mahabal, M. J. Graham, R. Williams (Caltech); M. Catelan (PUC Chile); E. Christensen (Gemini Obs); E. C. Beshore, S. M. Larson (LPL/UA).
on 28 Mar 2012; 07:23 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Andrew J. Drake (ajd@cacr.caltech.edu)

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We report the discovery of a 2008S-like transient in Catalina Sky Survey (CSS) data taken on Mar. 27.49 UT and analyzed by the CRTS Supernova Hunt project. The new object, identified as PSN J14535395+0334049 (SNhunt120), is located in the nearby (d=26.9 Mpc; NED) galaxy NGC 5775, at RA: 14:53:53.95, Dec: +03:34:04.9. The objects was detected at V =18.7 and was not seen in CSS data taken on Mar. 17.39 UT to V > 19.5. We obtained unfiltered follow-up observations on Mar. 28.07 and the object was observed at mag 18.5. The current absolute magnitude when corrected for Av=0.2 is Mv=-13.9.

An optical spectrum was taken using WFCCD mounted on the du Pont 2.5m telescope at Las Campanas Observatory on Mar 28.16 UT. The spectrum is dominated by relatively narrow and strong Balmer lines in emission. The H-alpha line can be well-fit by a Lorentzian profile with FWHM ~ 650 km/s. Other emission lines present in the spectrum are [Ca II] doublet and Ca II IR triplet. The spectrum also shows strong Ca II H&K doublet and Na I D in absorption. The EW of the Na I D feature is 2.6 Angstroms. All these features resemble the early-time spectra of the intermediate luminosity optical transients SN 2008S (e.g., Botticella et al. 2009) and NGC300 2008-OT (e.g., Bond et al. 2009). The observed absolute magnitude of the transient is consistent with the transient being similar to these events.

The host galaxy is covered by deep archival HST data (PI Rossa; prop 10416). We encourage follow-up high precision astrometry to enable searches for a possible progenitor.

Follow-up observations are encouraged.