SN 1999by in NGC 2841

(CCD image by Y. Sano)

(CCD image by Stapper)

Dear SN watchers,

Following SNe 1999bw and 1999bx, the remarkable SN has discovered by British amateur R. Arbour and LOSS KAIT team independently. This new object, named as Supernova 1999by, is in brightening phase, and will potentially reach the brightness which can be easily caught by small (say, 5') telescopes.

IAUC 7156 tells that the position of SN 1999by is: R.A. = 9h21m52s.18, Decl. = +51o00'07".2 (by KAIT team), which is about 100" west and 91" north from the core of the host Sb galaxy NGC 2841. The foreground stars near SN are there:

                 R.A.      Decl.    offset from SN  mag(about)
GSC3431_625  9h21m50s.8 +51o00'36".5  12"W,29"N     11
GSC3431_053  9h21m47s.4 +50o58'50".3  45"W,78"S     13
GSC3431_495  9h21m58s.3 +51o00'15".8  58"E,8"N      14
unnamed(*)   9h21m54s.6 +51o00'16".9  23"E,10"N     17

(*) is potentially a condensation in NGC 2841.

There seems some systematic errors in USNO magnitudes, and also in GSC magnitudes. The photometric (magnitude estimating) observer should use the sequence kindly provided by Prof. Skiff (vsnet-alert 2917, 2919) for the comparison.

NGC 2841 has produced (at least) three supernovae in this century. Among these three, only one, 1957A, was observed around its maximum at B = 14. It has been classified as a peculiar type I supernova. Other two had been missed their maximum.

NGC 2841 is about 0.7 mag nearer than Virgo center (M 87). Thus the typical SNeIa in this distance will have about 11.5 mag at their maximum without absorption. Now 1999by is in a rapidly brightening phase, so the followup observations (includeing spectroscopy) are extremely urged.

Best wishes, 
Hitoshi Yamaoka, Kyushu Univ., Japan
yamaoka@rc.kyushu-u.ac.jp

Skiff's compilation of BVRI comparisons

(vsnet-alert 2917)
(vsnet-alert 2937)

Observers of the new supernova in NGC 2841 will find the following BVRI sequence stars useful. These are the same stars marked on the Thompson and Bryan search chart for the galaxy. The data are extracted from my large photometric reference file: ftp://ftp.lowell.edu/pub/bas/starcats/loneos.phot Congrats to Ron Arbour and the LOSS team for picking up this one!

\Brian

Bob Modic, attentive as usual, has noticed that I have identified in error the mag. 12.6 star observed by Tsvetkov near NGC 2841. Using his information, I have made the correct ID, confirmed by offsets for another star in Tsvetkov's list that is farther afield. The complete revised sequence list is given again below. Below the main table is a list of explicit R magnitudes for each star that might be suitable for ordinary unfiltered CCD systems. The last line shows magnitudes for the "new" Tsvetkov star in the GSC and USNO-A2.0 catalogues.

I got a note today from Harold Corwin, who observed the BVRI sequence with Marian Frueh. (If I previously gave the impression that the stars were observed by me, that was not my intention---the material is merely unpublished.) Harold noted that he thought the stars in this field were adequately measured except perhaps the faintest stars in the U (not given here) and I filters.

\Brian

Name                  RA  (2000)  Dec    s     GSC       V    B-V   V-R   V-I
NGC 2841 1          9 22 28.4  +51 00 51 G  3431-0219   8.48  1.29  0.67  1.23
NGC 2841 2          9 21 50.8  +51 00 36 G  3431-0625  11.07  0.59  0.33  0.65
NGC 2841 3Ts        9 22 53.3  +51 01 28 G  3431-1249  12.62  0.64 (0.37)
NGC 2841 3          9 21 47.3  +50 58 50 G  3431-0053  13.51  0.75  0.43  0.83
NGC 2841 4          9 21 58.2  +51 00 16 G  3431-0495  13.77  0.60  0.40  0.74
NGC 2841 5          9 22 02.3  +51 01 23 G  3431-0159  14.19  0.83  0.42  0.91
NGC 2841 147        9 22 06.8  +50 53 37 G  3431-0802  14.72  0.88 (0.49)

Note:  V-R colors in parens were derived from B-V.


Name    R
1      7.81
2     10.74
3Ts   12.25
3     13.08
4     13.37
5     13.77
147   14.23