SN 1998es in NGC 632

Image of SN 1998es

J. Porto's image


Nov. 16

cf. vsnet-obs 18034

Dear SN watchers,

A bright supernova has been discovered after about 1 month absence. IAUC 7050 tells that KAIT team has discovered SN 1998es, which position is R.A. = 1h37m17s.50, Decl. = +5o52'50".3 (2000.0), which is about 11" north of the nucleus of NGC 632. M. Aoki, R. and Y. Kushida have confirmed it.

Estimated from its recession velocity, NGC 632 is a some near-by galaxy which is about 3 times further than Virgo. The expected maximum magnitude of typical SNeIa on this distance would be about 14.5 mag. Its morphorogy type is uncertain, but some catalogs take it as face-on S0 galaxy. There is a foreground star (about 15 mag) at about 10" east and 17" north from the core of NGC 632.

The reported magnitudes tells that SN 1998es is around 14.5 mag now. Further magnitude estimates and spectroscopic confirmations are encouraged.

Nov. 20

Dear SN watchers,

It has been revealed that SN 1998es is of type Ia, but it shows some peculiarity. CfA group obtained its spectrum at Nov. 14.2 UT, which is reported on IAUC 7054 and can be seen at CfA recent supernova page. It resembles that of SN 1991T before seven days before maximum, which was intrinsically brighter among SNeIa.

Also, Bisei Astronomical Observatory obtained its spectrum at Nov. 19.7 UT. It shows that the spectral evolution is also similar to that of 1991T. The existance of the narrow Na D lines indicates that 1998es is somewhat reddened. Now this SN would be arount maximum.

The nature of the intrinsically bright SNeIa has not been understood perfectly. It is very important for the SN cosmology or distance estimation to make a good photometry and spectroscopy of such objects. Followup observations are strongly encouraged.

Sincerely Yours,
Hitoshi Yamaoka, Kyushu Univ., Japan

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