Stars as Laboratories for Fundamental Physics - MPP Theory Group

Supernova Neutrinos 415
time) on 23 February 1987 while the first evidence for optical brightening
was found at 10:38 UT on plates taken by McNaught (1987)—see
Fig. 11.9.
The main neutrino observations come from the Irvine-Michigan-
Brookhaven (IMB) and the Kamiokande II water Cherenkov detectors,
facilities originally built to search for proton decay, while a less significant
measurement is from the Baksan Scintillator Telescope (BST).
A likely spurious observation is from the Mont Blanc Liquid Scintillator
Detector (LSD). It preceded the other observations by about 5 h,
with no contemporaneous signal at Mont Blanc with the other signals,
and no contemporaneous signal at the other detectors with the Mont
Blanc event. The Mont Blanc detector was built to search for neutrinos
from core collapse supernovae, except that it was optimized for galactic
events within a distance of about 10 kpc. The neutrino output of
a normal SN in the LMC could not have caused an observable signal
at Mont Blanc; the reported events probably represent a background
fluctuation.
Koshiba (1992) has given a lively account of the exciting and initially
somewhat confusing story of the neutrino measurements and their
interpretation. Early summaries of the implications for astrophysics
and particle physics of the neutrino and electromagnetic observations
were written, for example, by Schramm (1987), Arnett et al. (1989),
and Schramm and Truran (1990). A more recent review of SN 1987A
is McCray (1993). A nontechnical overview was provided in a book by
Murdin (1990).
For the present purposes the bottom line is that SN 1987A broadly
confirmed our understanding of SN physics as outlined in Sect. 11.1.
A remaining sore point is the lack of a pulsar observation in the SN
remnant so that one may continue to speculate that a black hole has
formed in the collapse.
11.3.2 Neutrino Observations
In the IMB and Kamiokande water Cherenkov detectors neutrinos are
measured by the Cherenkov light emitted by secondary charged particles,
e ± for the relatively low-energy (anti)neutrinos emitted from a
stellar collapse. The IMB detector is now defunct while Kamiokande
continues to measure, for example, solar neutrinos until the much larger
Superkamiokande detector will take up operation in 1996. In the Baksan
Scintillator Telescope (BST) one measures the scintillation light
produced by charged secondary particles.