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Supernova SN2011fe in M101

The Scientific Importance of this Supernova

SN2011fe in M101

This close-up image of the nearby galaxy M101 was obtained 18 September, 2011 with the Mayall 4-meter telescope at Kitt Peak National Observatory. The supernova is clearly visible as the bright, bluish star in the upper, right portion of the image.

The newly discovered supernova (SN) in M101 is the closest Type Ia SN since SN 1972E and certainly the closest to be observed with modern tools. It was also caught soon after explosion and may well be the earliest detection of a Type Ia SN ever. As such, it provides a tremendous opportunity for detailed and thorough study. Type Ia SNe are intrinsically interesting objects whose importance touches on many aspects of astrophysics, from stellar evolution to nuclear astrophysics to galactic chemical enrichment.

Recently, though, their significance has come from their role as the best method for determining cosmological distances. From these distance determinations came the first evidence for dark energy (Riess et al. 1998, Perlmutter et al. 1999), a revolution that has changed cosmology in the last decade. Subsequent tests using Type Ia SNe have shown that the equation of state of the Universe is consistent with a cosmological constant (e.g., Astier et al. 2006, Wood-Vasey et al. 2007). At this stage, the limiting factors in the precision of the SN results are the systematics of the SNe themselves (e.g., Conley et al. 2011, Hicken et al. 2009). Thus, one of the best ways to improve the precision of the cosmological results is to improve our understanding of the properties of Type Ia SNe.

A supernova in M101 is extremely useful for this purpose. The proximity allows for detailed study of the object and the extensive prior work on M101 provides a precise measurement of exactly what that proximity is. This can provide a better calibration of the distances to Type Ia SNe themselves. Tied to the other distance measurements of M101, this can improve constraints on H0. In addition, as the nature of the progenitors of Type Ia SNe is still an open question, a nearby explosion means that the environment of the SN can be examined in exquisite detail. Deep HST imagery of M101 might even reveal a companion star, which would demonstrate that the single degenerate model is the correct explosion mechanism (for this SN—it wouldn’t eliminate other possibilities completely).

Observations in the near infra-red are critical for understanding Type Ia SNe. Evidence is accumulating that Type Ia SNe are standard candles in the near IR (Krisciunas et al. 2007, Meikle et al. 2000, Wood-Vasey et al. 2008), especially in the H band. Broad wavelength coverage of the SN can help to evaluate extinction, a particularly difficult problem for cosmological studies. The maximum of near IR light curves typically peaks before the optical bands for Type Ia SNe, so an object caught as early as this is especially useful for studying the entire light curve.

Preliminary Data Shows the Brightening of the Supernova

Top left: WIYN/WHIRC light curve, showing relative magnitudes in J, H and Ks bands. Initial observation taken on August 26, 2011.

Top right: Spectra obtained at the Mayall 4-m with the Richey-Chretien Spectrograph (RC spec).

Bottom: Mosaic of the H band images of SN2011fe from 27, 29, and 30 August, 2011. Even though the image quality was very different on the three nights, one can see a definite increase in brightness over the interval.

Images from the Visitor Center’s Roll-off-Roof Observatory

Flynn Haase and Steve Peterson captured the above images of Supernova PTF11kly in M101 on the evening of 29 August, 2011 at the Visitor Center’s Roll-off-Roof Observatory using the 16” f/8.4 RCOS telescope at cassegrain focus with a Santa Barbara Instrument Group STL6303XE CCD camera through “pretty picture” RGB filters. The 10-minute integration exposure times revealed galaxy detail, but were too long for the supernova, causing it to saturate in the images.

The supernova is indicated on each image. Click image to enlarge.