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Potential Progenitor Detection For PSN J1453+0334 In Archival HST Data

02/04/2012

ATel #4009: On 29 Mar 2012; 18:09 UT, E. Berger, G. H. Marion (Harvard/CfA), E. Hsiao (LCO), R. Foley, R. Chornock (Harvard/CfA) observed the location of the Catalina Sky Survey transient PSN J14535395+0334049, which spectroscopically resembles SN2008S (Howerton et al. ATEL #4004), with the MMT & Magellan Infrared Spectrograph (MMIRS) on 2012 March 29.33 UT. Observations were obtained in J-band in ~0.5″ seeing.

Using 17 sources in common between their MMIRS image and an archival HST ACS/F625W image of NGC 5775 (program 10416; PI: Rossa), Berger et al. located the position of the transient to a relative astrometric accuracy of about 60 mas in RA and Dec. Within the 1-sigma region around the transient position Berger et al. detected a faint source in the HST image with an F625W AB mag of 25.5-26 mag (uncertainty dominated by the non-uniform background). At the distance of NGC 5775, this corresponds to an absolute magnitude of -6.1 to -6.6 mag. An image of the field with the position of the source is available from:

PSN J1453+0334 HST Archive – https://www.cfa.harvard.edu/~eberger/PSN1453+0334_HST.ps.

ATel #4004: On 28 Mar 2012; 07:23 UT,  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)  reported 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. Howerton et al. obtained unfiltered follow-up observations on March. 28.07 and the object was observed at mag 18.5.

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).

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