Welcome to The Virtual SNIa Gamma Ray Instrument

Clemson Astronomy ACT Contact Us

The idea of these pages: A major objective of NASA's Advanced Compton Telescope (ACT) is the study of the physics of supernovae via their gamma-ray spectra. The requirements for achieving this objective are currently being developed. To aid this effort, we are developing these online tools for the calculation and display of gamma-ray spectra of supernova models. The user can choose among a menu of models, input time(s), distance(s), and instrument characteristics (such as sensitivity and energy resolution) and plot or output simulated spectra.
Selection Name Selection Value On Off
Supernova Parameters
Select Model - -
Time Since Explosion (days) - -
Supernova Distance Mpc - -
Instrument Parameters
Energy Resolution % - -
Narrow Line Sensitivity * 1e-7 - -
Plotting Options
Specific Energy Range
min:keV max:keV - -
logarithmic x-axis
logarithmic y-axis
Error Bars
Overplot Supernova Model
Select Model - -
Time Since Explosion (days) - -
Supernova Distance Mpc - -


Supernova Gamma-Rays

Type Ia supernovae are now routinely used as empirically calibrated standard candles to measure distances at redshifts of order unity. Despite this our understanding of the explosions themselves has not progressed as rapidly. It has long been discussed (e.g., Clayton et al.) that gamma-ray line observations offer a unique direct view of the location and kinematics of the newly synthesized radioactivity, and therefore, a diagnostic of the explosions. However, previous gamma-ray spectrometers have not been sensitive enough to study SN Ia at typical distances. Thus it is essential that the ACT sensitivity be sufficient to detect many SN Ia with high significance.

We provide a simple way to visualize ACT observations of SN Ia using basic instrument capabilities and current SN Ia models. We presently use models of a Chandrasekhar mass deflagration (W7, Nomoto, Thielemann, Yokoi 1984), a delayed detonation (DD202C, Hoflich et al. 1998), and sub-Chandrasekhar mass explosions (HED8, Hoflich & Khokhlov 1996). For each model we calculate the gamma-ray spectra at times from 5--200 days post-explosion using a modified version of the Monte Carlo transport code of The et al. (c.f., Milne et al.)

The instrument capabilities are simply specified in terms of narrow line sensitivity (3s) and energy resolution (FWHM). We assume a continuum background only, so these two parameters define the background count rate under an instrument-resolution line, and therefore under the broadened supernova lines. Random fluctuations appropriate to the binning chosen are added to the spectrum. Any model at any distance can be over-plotted as a smooth curve, to see how well the data could discriminate among models.


Welcome to the Virtual SNIa Gamma Ray Instrument

The purpose of this website is to create a way to view data from an instrument with some stated energy resolution without actually using it. By using IDL a certain amount of noise is created acording to the options that the user inputs above and uses this value for noise to modify the spectrum of the selected model. The intention is to give individuals in the astrophysics community a way to see what these spectrum will look like through their proposed instruments, and to give these individuals a standard candle, if you will, to compare notes by. Should there be terminology that is not completely understood the help link may be useful.
This website was created by Doug Chappell in the summer of 2004 using SHP, IDL, and a sprinkle of Perl. Copyright information, if needed, to come soon