Studies by the Nearby Supernova Factory of its colours and spectrum as they evolved over time have produced a benchmark atlas of data by which to measure all future Type Ia's.
Credit: B. J. Fulton, Las Cumbres Observatory Global Telescope Network
August, 2011, saw the dazzling appearance of the closest and brightest Type Ia supernova since Type Ia's were established as "standard candles" for measuring the expansion of the universe.
The brilliant visitor, labeled SN 2011fe, was caught by the Palomar Transient Factory less than 12 hours after it exploded in the Pinwheel Galaxy in the Big Dipper.
Easy to see through binoculars, 2011fe was soon dubbed the Backyard Supernova. Major astronomical studies from the ground and from space followed close on its heels, recording its luminosity and colors as it rapidly brightened and then slowly faded away.
The international Nearby Supernova Factory (SNfactory), led by Greg Aldering of the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), has now released a unique dataset based on 32 nights of repeated observations of 2011fe with the SuperNova Integral Field Spectrograph (SNIFS), built by the SNfactory's partners in Lyon and Paris, France, and mounted on the University of Hawaii's 2.2-meter telescope on Mauna Kea.
The observations began two weeks before the supernova reached its peak brightness and continued for over three months after maximum light had passed.
"We'd never before seen a Type Ia supernova this early," says Aldering, a cosmologist in Berkeley Lab's Physics Division. "Our measurements showed how remarkably normal 2011fe is."
SNfactory member Rui Pereira of the Institut de Physique Nucléaire de Lyon says that the collected data "will be benchmark atlas for all future studies of Type Ia's."
Pereira is the lead author of the article presenting the observations in the journal Astronomy & Astrophysics.
Type Ia supernovae aren't so much standard candles as "standardisable" ones. Graphs of how their brightness and spectral features change over time – their light curves – vary, but because timing and brightness are related, the light curves can be stretched (or squeezed) to match the standard. SN 2011fe's light curve falls right in the peak of the distribution – as astrophysicists say, it has "stretch 1."
Rollin Thomas, of Berkeley Lab's Computational Research Division, was deeply involved in the 2011fe analysis.
As new data arrived from the telescope each night he recalls thinking "please don't be peculiar, please don't be peculiar," and was pleased to find that the supernova was so normal.
More information: "Spectrophotometric time series of SN 2011fe from the Nearby Supernova Factory," www.aanda.org/articles/aa/abs/2013/06/aa21008-12/aa21008-12.html
Posts
No comments:
Post a Comment