SN 1998T in NGC 3690

(V and B images taken at Ouda Station, observer Daisaku Nogami)

(vsnet-alert 1520)

Dear VSNET-alert subscribers,

Next to SN 1998S, there appeared another SN in IC 694 in UMa (IAUC 6830). The host galaxy is a part of Arp 299 = Markarian 171, and NGC 3690. SN's location is :

        R.A.  = 11h28m32s
        Decl. = +58o33'.7 (2000.0).
The host galaxy is irregular one, so the nucleus of the host galaxy is uncertain. SN 1998T is close to a nebular in the host.

The spectroscopy shows that SN 1998T is of type Ib, probably near the maximum. Its magnitudes are: 15.4 on Mar. 3 UT (discovery image), 14.5 on Mar. 4.3 UT. They are unfiltered CCD magnitudes. Followup observation are encourged, same as SN 1998S.

On the same IAUC, a new specrtoscopy of SN 1998S is also reported by UCB group. It tells that SN 1998S is peculiar; it shows not only the H emission but also the He emission line. They comment that it resembles to the type II-n event SN 1997eg, and SN 1998S may have a dence circumstellar gas. It is probable that this SN will be brighten in radio or X-ray. To connect with the observations in these wave length, the optical photometries are very important and urged.

Clear Skies,
Hitoshi Yamaoka, Kyushu Univ., Japan.

Correct location of SN 1998T

Yamaoka's message

Ayabe Observatory's image

Accurate coordinates and galaxy identification

(vsnet-chat 797)

Dear all,

We have long discussed about the location of SN 1998T and the identification of the host galaxy (and surroundings). I will show the temporal conclusion now.

NGC 3690 is a colliding pair of galaxies. SN 1998T appears on the eastern galaxy of this colliding pair; more precisely, the southern part (south of the dust lane) of the eastern one. The measured position from GSC stars is R.A. = 11h28m33s.16, Decl. = +58o33'43".7 (J2000.0). Note that this position differs about 15" from the reported one in IAUC 6844. The accuracy of above position is estimated as 0".5, mainly due to the uncertainties of GSC positions. Ambiguity arose from the contamination of the host galaxy is also non-negligible.

IC 694 is E/S0 galaxy 1' northwest from NGC 3690. Many references show that IC 694 is a part of the interacting pair, but historically it is wrong, which was pointed out by Drs. Skiff and Cowrin. IC 694 is identical to MCG+10-17-2A.

Markarian 171 is identical to NGC 3690.

It is widely accepted that Arp 299 is composed by NGC 3690 and IC 694, and possibly other companions. Arp 296 (original Arp catalog shows that Arp 296 = NGC 3690 + IC 694) are considered as the other peculiar galaxy.

Thank those who share the discussions!

Sincerely Yours,
Hitoshi Yamaoka, Kyushu Univ., Japan

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