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孙国佑 星明天文台帮助确认M51超新星 2011dh

SUPERNOVA 2011dh IN M51 = PSN J13303600+4706330
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. = 13h30m05s.119, Decl. = +47o10’11”.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).

NOTE: These ‘Central Bureau Electronic Telegrams’ are sometimes
superseded by text appearing later in the printed IAU Circulars.

(C) Copyright 2011 CBAT
2011 June 3                      (CBET 2736)              Daniel W. E. Green

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