SN 2014J in M82 is the closest detected Type Ia supernova ( SN Ia ) in at least 28 years and perhaps in 410 years .
Despite its small distance of 3.3 Mpc , SN 2014J is surprisingly faint , peaking at V = 10.6 mag , and assuming a typical SN Ia luminosity , we infer an observed visual extinction of A _ { V } = 2.0 \pm 0.1 mag .
But this picture , with R _ { V } = 1.6 \pm 0.2 , is too simple to account for all observations .
We combine 10 epochs ( spanning a month ) of HST /STIS ultraviolet through near-infrared spectroscopy with HST /WFC3 , KAIT , and FanCam photometry from the optical to the infrared and 9 epochs of high-resolution TRES spectroscopy to investigate the sources of extinction and reddening for SN 2014J .
We argue that the wide range of observed properties for SN 2014J is caused by a combination of dust reddening , likely originating in the interstellar medium of M82 , and scattering off circumstellar material .
For this model , roughly half of the extinction is caused by reddening from typical dust ( E ( B - V ) = 0.45 mag and R _ { V } = 2.6 ) and roughly half by scattering off LMC-like dust in the circumstellar environment of SN 2014J .