[vsolj-alert 352] Re: SN1999cl in M88

[Hitoshi YAMAOKA <yamaoka@rc.kyushu-u.ac.jp>]

山岡＠九大理 です。続報です。

>  AL Comを見ていると超新星がみつかるかも？との噂通り、Ｍ８８に超新星らしき
>　天体が発見され、１日で１６等から１５等に増光中とのこと。

スペクトル観測でIa型と判明しています。7日現在で14等級ほどの明るさになっ
ています。おとめ座銀河団のIa型なのにかなり吸収を受けているため暗めです
が、吸収量の見積もりよりは明るいかな? という感じで、注目です。

Subject: Re: SN 1999cl in NGC 4501

Dear SN watchers,

>Bright SN has been discovered by LOSS KAIT team.  See IAUC 7185 for
>details.  The host galaxy NGC 4501 is fairly nearby one (v_r is about
>2500 km/s), so the expected SNeIa maximum would be order of 14 mag.

  This SN is still rising.  According to IAUC 7190, the spectrum of SN
1999cl on June 4.2 UT shows that it is of type Ia, probably before
maximum.  It is noted that SN is heavily extinguished by the
interstellar dust.  Then the CCD magnitude would be normally brighter
than visual or V-band estimates. 

  The host galaxy NGC 4501 = Messier 88 is a Sb/c galaxy with multiple
arms.  The SN is on the northwestern inner arm, just outside of the
bulge.  G. Masi provided the precise position of SN 1999cl as: R.A. =
12h31m56s.01, Decl. = +14 25'35".3 (2000.0), which is about 45" west
and 25" north from the core of the host (IAUC 7191).  The DSS2 image
shows the bright HII region just 5" south from the SN, which would
affect the photometry or the astrometry.  

  Though the recession velocity is somewhat large (2030 km/s by
Garnavich et al., IAUC 7190), NGC 4501 is thought to be a firm member
of the Virgo cluster.  Typical SNeIa in the Virgo cluster will be
about 12 mag at their maximum if they aren't affected by the
absorption.  The color excess of SN 1999cl is reported as E(B-V) = 1.0,
from which the extinction in V-band is estimated as A_V = 3.3.  This
value seems, however, to be somewhat overestimated, because SN 1999cl
is observed as mv = 14.2 - 14.4 around June 5.0 (IAUC 7191) and V =
14.45 at June 4.94 (D. Morata, vsnet-obs 21029).  The other
possibility is that SN 1999cl is intrinsically brighter than the
normal one.  Further magnitude estimates are extremely encouraged.

Sincerely Yours,
Hitoshi Yamaoka, Kyushu Univ., Japan
yamaoka@rc.kyushu-u.ac.jp

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