[vsnet-chat 791] Supernova 1998S: Some Tidbits

["Steve H. Lucas" <76620.1721@compuserve.com>]

Supernovae Fans:

The event in NGC 3877 is an unexpected and plesant surprise to us all here
is some info/tidbits:

*NGC 3877 an SCII.2 type galaxy has a BT magnitude of 11.78 (Harvard
magnitude reduced into the BT system [RC2]) from Sandage&Tammann {1981} "A
Revised Shapley-Ames Catalog of Bright Galaxies".

*The distance modulus is ~31.37 (Ho=50km/sec per Mpc) yielding an
approximate distance of 25MLY (24,600,081)(same source as above).

*The weighted mean observed velocity for NGC 3877 is ~887 which places this
entity a bit closer to us than Cluster B of the Virgo Cluster (M49) which
has a velocity of ~963+/-81. (same source as above, and STUDIES OF THE
VIRGO CLUSTER, by Binggeli, Sandage and Tammann; The Astronomical Journal,
Vol. 90, No.9, Jan., 1984-1985,)

*At this distance and inferring a general SN maximum absolute magnitude
gauge of -20.0 for type I's and -18.0 for type II's, (Ho=50) this event's
luminosity would indicate a type I event. (11.37 for a type I, and 13.37
for a type II) 

*Being that it is a type IIn event there are several considerations that
come to light. One being that by indications of the early light curve we
might have a very bright linear type II event on our hands ~1.7 magnitudes
brighter than expected. Accessing the paper "Model Light Curves of Linear
Type II SNe" by Swartz and Wheeler, Preprint #129, Dept. of Astronomy and
McDonald Observatory, Jan 10, 1991all indications point to some
similarities of this event to the bright linear type SN's 1979C or SN1980K,
of course late analysis of the light curve will determine if similarities
do indeed exist.

*What is interesting from the above paper is that SN 1979C was ~3
magnitudes brighter than the average, and 1980K was ~2 magnitudes brighter.
Another item of interest is that models for the aforementioned two events
were theorized to have involved two totally different explosive mechanisms.

*Still another event, SN 1983K from Patat et. al (A&A_282_,731-741 (1994)
displays an uncanny rise to maximum light that is very similiar to 1998S,
with data existing around maximum light that is characteristic of what
observers are reporting for this event.....interesting stuff!

Cheers,

Steve H. Lucas
International Supernovae Network

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