Dust in the line of sight to stars and supernovae dims the light, thereby making it more difficult to use the brightness of the object to determine its distance from us. However, as the effect is wavelength dependent, as shown in the figure, we can account for it, at least as long as we understand the properties of the dust which attenuates the light.
Follow this link to read our publications on this subject
Follow this link to read our publications on this subject
Diversity in Extinction Laws of Type Ia SN (Amanullah et al 2015)
We present ultraviolet (UV) observations of six nearby Type~Ia supernovae (SNe~Ia) obtained with the Hubble Space Telescope, three of which were also observed in the near-IR (NIR) with Wide-Field Camera~3. UV observations with the Swift satellite, as well as ground-based optical and near-infrared data provide complementary information. The combined data-set covers the wavelength range 0.2--2 μm. By also including archival data of SN 2014J, we analyse a sample spanning observed colour excesses up to E(B−V)=1.4 mag. We study the wavelength dependent extinction of each individual SN and find a diversity of reddening laws when characterised by the total-to-selective extinction RV. In particular, we note that for the two SNe with E(B−V)≳1 mag, for which the colour excess is dominated by dust extinction, we find RV=1.4±0.1 and RV=2.8±0.1. Adding UV photometry reduces the uncertainty of fitted RV by ∼50% allowing us to also measure RV of individual low-extinction objects which point to a similar diversity, currently not accounted for in the analyses when SNe~Ia are used for studying the expansion history of the universe.
The paper is available here: Diversity in extinction laws of Type Ia supernovae measured between 0.2 and 2μm
The paper is available here: Diversity in extinction laws of Type Ia supernovae measured between 0.2 and 2μm
Extinction of SN2014J (Amanullah et al 2014)
The wavelength-dependence of the extinction of Type Ia SN2014J in the nearby galaxy M82 has been measured using UV to near-IR photometry obtained with the Hubble Space Telescope, the Nordic Optical Telescope, and the Mount Abu Infrared Telescope. This is the first time that the reddening of a SN Ia is characterized over the full wavelength range of 0.2-2 μm. A total-to-selective extinction, RV≥3.1, is ruled out with high significance. The best fit at maximum using a Galactic type extinction law yields RV=1.4±0.1. The observed reddening of SN2014J is also compatible with the empirical law with c=1.06±0.04, and a power-law extinction, Aλ/AV = (λ/λV)p as expected from multiple scattering of light, with p=-2.1±0.1. After correction for differences in reddening, SN2014J appears to be very similar to SN2011fe over the 14 broad-band filter lightcurves used in our study.
The paper is available here: The peculiar extinction law of SN2014J measured with the Hubble Space Telescope
The paper is available here: The peculiar extinction law of SN2014J measured with the Hubble Space Telescope
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