SUPERNOVA 2011hj = PSN J18322232+6653466
Guoyou Sun (Wenzhou, Zhejiang, China) and Xing Gao (Urumqi, Xinjiang,
China) report the discovery of a possible supernova (mag approximately 17.9)
on several unfiltered CCD 40-s survey images (limiting mag about 19.0) taken
by Xing Gao in the course of the Xingming Observatory Sky Survey at Mt.
Nanshan around Oct. 26.650 UT using a 35.6-cm Celestron C14 Schmidt-Cassegrain
telescope. The new object is approximately located at R.A. = 18h32m22s.32,
Decl. = +66d53’46”.6 (equinox 2000.0; reference catalogue USNO-A2.0), which
is about 19″.2 west and 3″.6 north of the center of PGC 2692384. The
discovery image is posted at URL http://www.xjltp.com/XOSS/XM03GS/XM03GS.htm.
The variable was designated as PSN J18322232+6653466 when it was posted on the
Central Bureau’s TOCP webpage and is here designated SN 2011hj based on the
spectroscopic confirmation reported below.
Additional magnitudes for 2011hj (via unfiltered CCD unless noted
otherwise): 1991 May 19, [19.8 (Digitized Sky Survey, red plate; via Gao);
1991 May 20, [21 (Palomar Sky Survey red image, via the Digitized Sky Survey;
reported by Vitali Nevski, Vitebsk, Belarus); 2011 Oct. 15, [19.0 (Gao);
Oct. 27.704 UT, R = 17.2 (Nevski; position end figures 22s.26, 46″.2;
reference stars from UCAC-3 catalogue); Oct. 29.946, R = 17.7 (Federica Luppi,
Varese, Italy, 0.36-m f/7.9 reflector + Bessell R filter; position end figures
22s.22, 46″.0; reference stars from PPMXL catalogue; image posted at website
URL http://www.astrogeo.va.it/pub/TOCP/PSN_P2692384.jpg).
L. Tomasella, S. Benetti, S. Valenti, A. Pastorello, and M. Fiaschi,
Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Padova, on
behalf of a larger collaboration, report that a spectrogram of PSN
J18322232+6653466 = SN 2011hj was obtained on Oct. 30.80 UT with the Ekar-
Copernico 1.82-m telescope (+ AFOSC; range 380-820 nm; resolution 2.2 nm).
Cross-correlation with a library of supernova spectra using the “Supernova
Identification” code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) suggests
that 2011hj is a young type-II supernova at z = 0.019. The spectrum shows a
blue continuum with prominent H and He I 587.6-nm lines. The expansion
velocity, as deduced from the position of the minimum of H_beta, is about
9600 km/s.
D. Kasen and A. V. Filippenko, University of California, Berkeley; and
R. J. Foley, Harvard-Smithsonian Center for Astrophysics, report that a CCD
spectrum (range 310-1020 nm), obtained on Oct. 31 UT with the Keck I 10-m
telescope (+ LRIS), shows that PSN J18322232+6653466 = SN 2011hj is a young
type-II supernova. Cross-correlation with a library of supernova spectra
using the “SuperNova IDentification” code (SNID; Blondin and Tonry 2007,
Ap.J. 666, 1024) indicates that the supernova’s redshift is approximately
0.02. Removing the corresponding recession velocity, the minimum of the weak
H_alpha absorption (which is greatly dominated by H_alpha emission) is found
to be blueshifted by 13000 km/s. The line features and blue continuum suggest
that the supernova is young, with the spectrum resembling that of the type-
II-plateau supernova 1993W around 5 days after explosion (Baron et al. 2003,
Ap.J. 586, 1199)
