SIMBAD references

A new apparent supernova in the galaxy M51 was discovered apparently independently and reported to the Central Bureau yesterday by several observers; when posted at the Central Bureau's TOCP webpage it was designated PSN J13303600+4706330 (based on the inferior position sent by T. Griga) and is here designated SN 2011dh based on the spectroscopic reports below. The order in which the apparent discovery reports were received (with the observation time given parenthetically) is as follows, all made via CCD images unless noted otherwise: (1) Tom Reiland, Glenshaw, PA, U.S.A. (June 2.189 UT, visual; 53-cm f/4.5 Manka reflector at Wagman Observatory in Deer Lakes Park, Frazer Township, PA; offset given as 2'.5 east, 1'.5 south of the nucleus of M51); (2) Thomas Griga, Schwerte, Germany (June 1.967; 30.5-cm reflector); (3) Amedee Riou, Becon les Granits, France (June 1.893; 25.4-cm f/4.7 reflector; object also visible on May 31 in an inferior, trailed photo, but was not visible on May 10; images supplied but no positions given); (4) Stephane Lamotte Bailey, France (June 2.036; 20-cm Celestron-8 telescope; nothing visible at the position of 2011dh on his image from May 30.105; communicated by Marc Deldem).

Reported measurements of the position and magnitude of 2011dh (from unfiltered CCD images unless noted otherwise):

---------------------------------------------------------------------------— 2011 UT R.A. (2000.0) Decl. Mag. Observers ---------------------------------------------------------------------------— May 31.954 13 30 34.6 +47 06 48 14.1 Marulla, Grenier June 1.967 13 30 36 +47 06 33 Griga 2.036 13 30 04.76 +47 10 05.3 13.7 Lamotte Bailey 2.721 13 30 05.14 +47 10 11.0 14.4 Sun, Gao 2.9286 13 30 05.12 +47 10 10.8 14.6 Dupouy 3.085 13 30 05.13 +47 10 11.1 14.6 Broens 3.18 13 30 05.56 +47 10 10.3 14.8 Koff ---------------------------------------------------------------------------—

Notes to astrometric observers: Mathew A. Marulla and Tavi A. Grenier (0.5-m f/6.8 corrected Dall-Kirkham telescope + FLI PL09000 CCD camera + Luminance/R/G/B filters, SLOOH Canary Islands Observatory, Mt. Teide; 2011dh not present on images from May 31.062; offset from nucleus of M51 2'49" at p.a. 130.3 deg; claim to independent discovery uncertain, but their report was sent on June 2.9 UT and, based on their position, it seems likely that they learned about it from the TOCP; confirming image from June 3.035). T. Griga (equinox 2000.0 assumed). G. Sun and X. Gao (Xingming Observatory, Mt. Nanshan, China; offset about 138" east and 92" north of the center of NGC 5194 = M51; limiting mag 19). S. Lamotte Bailey (measured by Deldem; USNO-A2 catalogue reference stars; pixel size 1".5). Ph. Dupouy (Dax, France; 0.32-m f/6 reflector; UCAC-3-catalogue reference stars; apparently R-band image). Eric Broens (Mol, Belgium; 20-cm Schmidt-Cassegrain reflector + ST-7XME CCD camera). R. A. Koff (Bennett, CO, U.S.A.; 0.25-m f/10 Schmidt-Cassegrain reflector; magnitude difficult due to glow from background galaxy; nothing at this position visible on Digitized Sky Survey).

Additional magnitude estimates for 2011dh: May 30.90, [19.5 (H. Mikuz and B. Dintinjana, University of Ljubljana, 0.25-m f/5 reflector; four stacked red, unfiltered 60-s images); June 1.893, 14 (Riou); 2.189, 14 (Reiland; visual); 3.219, 14.4 (Reiland; visual); 3.4695, 14.5 (Toru Yusa, Osaki, Japan; CCD).

Lamotte Bailey's discovery image is posted at the following website URL: http://i25.servimg.com/u/f25/14/65/52/82/possib10.jpg. An image from Marulla and Grenier, presumably from May 31, is posted at the following website URL: http://www.slooh.com/files/m51_position.png. Dupouy's image is posted at URL http://astrosurf.com/obsdax/sn-m51/SN-M51-anot.jpg. Griga has posted his discovery image at https://picasaweb.google.com/102525688909138782861/M51#. Yusa's image is at http://space.geocities.jp/yusastar77/PSN-M51_110603.htm. Koff's image is posted at the following website URL: http://antelopehillsobservatory.org/SNpictures/PSNJ13303600+4706330final.jpg.

J. M. Silverman, S. B. Cenko, and A. V. Filippenko, University of California, Berkeley, report that inspection of a CCD spectrum (range 320-1000 nm), obtained on June 3 UT with the 10-m Keck I telescope (+ LRIS), shows that PSN J13303600+4706330 = SN 2011dh is a type-II supernova with well-developed P-Cyg line profiles. The spectrum shows a relatively blue continuum, with the broad H-alpha emission component dominating over the absorption component. After removal of the host-galaxy recession velocity of 600 km/s (Rush et al. 1996, Ap.J. 473, 130), the minimum of the H-alpha absorption is blueshifted by about 17600 km/s.

W. Li and A. V. Filippenko, University of California, Berkeley, report that they have isolated a possible progenitor for SN 2011dh in Hubble Space Telescope images of M51 (GO/DD program 10452) taken with the Advanced Camera for Surveys (ACS). A geometrical transformation between a stacked KAIT (Lick Observatory) image of 2011dh taken on June 3.26 UT and the ACS images has yielded the identification of an object in the ACS images that is within the 0".09 uncertainty of the supernova position; this object was detected in the F435W (B-band), F555W (V-band), F658N (H-alpha), and F814W (I-band) images. The position of the candidate progenitor is measured to be R.A. = 13:30:05.119, Decl. = +47:10:11.55 (equinox 2000.0). Further analysis of the astrometry and photometry of the candidate progenitor is in progress. A finder chart with stamps of the supernova site from the ACS images in different filters can be found at the following website URL: http://astro.berkeley.edu/~weidong/m51sn.prog.gif.

M. Yamanaka, R. Itoh, and T, Ui, Hiroshima University; and A. Arai, M. Nagashima, and K. Kajiawa, Kyoto Sangyo University, report that they obtained low-resolution optical spectra of 2011dh on June 3.6 UT at Higashi-Hiroshima Observatory, Hiroshima University (R = 400) and at Koyama Astronomical Observatory, Kyoto Sangyo University (R = 600). The spectra show the absorption line of H-alpha at 620 nm, He I at 560 nm, and the Ca II infrared triplet at 820 nm, whose line velocities reach 17000, 16000, and 16000 km/s, respectively. It also exhibits Fe II and H-beta absorption lines around 500 and 470 nm. These profiles are similar to those of the type-IIP supernova 2006bp at 10 days after the shock breakout (Quimby et al. 2007, Ap.J. 666, 1093).