[vsnet-chat 943] Re: Expected SN Ia maximum in M96

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

Steve Lucas wrote:

>My source for most SNe data utilizes data from other "camp" 
>(Ho=3D50km/sec/Mpc) mainly because I have more reference material
>involving same <g>. 

If we use the observed SNeIa maximum in Virgo cluster and compare the
recession velocity of Virgo with that of the host of SN, the
uncertainty of H_0 is not concerned.  It is the way of SNMax (and in
its revised version) offered by Taichi. 

On the other hand, the distance estimate using recession velocity is
very dangerous and will give a mis-leading results when we adopt it to
nearby galaxies.  Instead, we should use the distance estimated by
other method (T-F relation, Cepheid, and so on) and compare it with
the Virgo distance derived by HST (16 - 17 Mpc).  For M96 case, the
catalogued distance was 8.1 Mpc (Turry, Nearby Galaxy Catalog), which
implies that a object in M96 will be seen brighter about 1.6 mag than
it were in Virgo.  It gives my predicted maximum of SN 1998bu (12.3 -
1.7 = 10.6).  I know that Turry distance depends on H_0, so we have to
seek another source for distance which does not depend the H_0 value.

Taichi Kato wrote: 

>   Regarding this subject, infrared observations of SN 1998bu in IAUC
>6907 seem to provide additional clue.  The brightest reported K
>magnitude on May 14 is 11.4.   This value is ~0.5 mag brighter than
>the mean visual magnitude on the same night.  Assuming this difference
>is mainly due to Av (close to the estimated Av of 0.6 mag by Yamaoka),
>hence K magnitude representing "unreddened" magnitude, it looks still
>underluminous than predicted by Yamaoka.

It seems not a good assumption; first, the difference in magnitude
between the different band, i.e., the color of SN is changing day by
day. Second, the light curves of SN will show different shapes in
different color bands. It is commonly said that the maximum in the
redder band is the later. And, the magnitude at maximum is scarcely
observed by the infrared bands, so it has not been determined
accurately. 

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

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