[vsnet-chat 954] Re: Expected SN Ia maximum in M96 (Pavlyuk)

[Taichi Kato <tkato>]

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Date: Wed, 20 May 1998 17:58:56 +0400 (MSK DST)
From: "N.Pavlyuk" <pavlyuk@sai.msu.su>
To: Yamaoka Hitoshi <yamaoka@rc.kyushu-u.ac.jp>
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Subject: [vsnet-chat 0] Re: Expected SN Ia maximum in M96
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 Dear Supernova Hunters,

 We here in Sternberg Astronomical Institute use distances
 from  Tully's "Nearby Galaxy Catalog" (1988) FOR NEARBY GALAXIES. In
 this catalog
 H_0=75 km/s/Mpc was adopted. If you use another value of
 Hubble constant - H, you should add 5*log(H/75) to obtain apparent
 magnitude of a SN.

 Virgo Cluster has not ideal spherical shape. Rather it extends along
 the line of view. There could be some galaxies behind the cluster and
 some galaxies which lie closer to us than the center of Virgo.
 Hence one should calculate the distance to each galaxy in Virgo 
 SEPARETELY.

 The distances from recession velocity through Hubble law 
 V=H*R, where V=C*Z ( C - velocity of light, z - redshift,
 R - distance, H - Hubble constant, V - recession velocity)
 one could use distances from Hubble law up to  Z = 0.1

 If a supernova is located on higher redshift Z, one should
 take into account decelleration parameter q_0, and
 the distance to a supernovae on redshifts Z > 0.1 will
 also depends on q_0 as well as H_0 and Z.

 Also one should not forget to take into account K-correction
 for supernovae which are far from us.


 I write all this to show how many tricks exist in even 
 simple calculation of absolute magnitude of a SNe or
 in prediction of its brightness.

 Of course, you should not use K-correction, corrections
 for q_0 etc for calculation of 
 absolute or prediction of visual magnitude of a SN in Virgo cluster,
 but the method of of calibration of those magnitude from 
 Cepheids, Novae, Tully-Fisher, other objects and methods IS
 TOO SUBJECTIVE THAT IS DIFFERENT AUTHORS sometimes obtain
 different results using THE SAME METHOD of calibration.

 I want to illustrate all this just on 2 papers:
 
 1. Branch D., Miller D.L. 
    Astroph. J. 1993. V.405. P.5.
    (H_0=50 km/s/Mpc)

 2. Pierce M.
    1994, ApJ, 430, 53   
    ( H_0=85 km/s/Mpc )

 It is also  useful to see the paper of
  
  Jacoby G. et al.
  Publ. Astron. Soc. Pacific. 1992. V.104. P.599.
 
 
 There are just FACTS but it is YOU TO DECIDE.

 

 Best wishes,

 N.Pavlyuk

 Sternberg Astronomical Institute,
 Moscow State University
 
 
 
  




On Sun, 17 May 1998, Yamaoka Hitoshi wrote:

> 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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