Photometric and spectroscopic observations, and abundance tomography modelling of the Type Ia supernova SN 2014J located in M82

Abstract

Spectroscopic and photometric observations of the nearby Type Ia Supernova (SN Ia) SN 2014J are presented. Spectroscopic observations were taken -8 to +10 d relative to B-band maximum, using FRODOSpec, a multi-purpose integral-field unit spectrograph. The observations range from 3900Å to 9000Å. SN 2014J is located in M82 which makes it the closest SN Ia studied in at least the last 28 years. It is a spectrosopically normal SN Ia with high velocity features. We model the spectra of SN 2014J with a Monte Carlo (MC) radiative transfer code, using the abundance tomography technique. SN 2014J is highly reddened, with a host galaxy extinction of E(B − V )=1.2 (R V =1.38). It has a ∆m 15 (B) of 1.08±0.03 when corrected for extinction. As SN 2014J is a normal SN Ia, the density structure of the classical W7 model was selected. The model and photometric luminosities are both consistent with B-band maximum occurring on JD 2456690.4±0.12. The abundance of the SN 2014J behaves like other normal SN Ia, with significant amounts of silicon (12% by mass) and sulphur (9% by mass) at high velocities (12300 km s −1 ) and the low-velocity ejecta (v< 6500 km s −1 ) consists almost entirely of 56 Ni.

Supernova 2014J at M82 – II. Direct analysis of a middle-class Type Ia supernova

“…The Na I line is likely, but the large τ found for the February 6 (Day +4.2) spectrum is due to the dichroic break in the observed spectrum. Comparing with Ashall et al (2014), our results are somewhat different, by this time they find a significant amount of Fe II, which they take as evidence for 56 Ni above the photosphere, we do not find strong evidence for this. Na D are typically identified on core normal (or close to core normal) SNe Ia about one week post-maximum light (Branch et al 2008).…”

“…We do not find strong spectroscopic evidence for O I λ7774, as O I is not used in the SYNOW model, whereas abundance tomography finds that the high-velocity ejecta is dominated by oxygen (Ashall et al 2014). We will discuss this discrepancy in more detail in Section 8.…”

“…The SYNOW spectrum includes lines of six ions: Na I, Mg I, Mg II, Ca II, Fe II, Co II, and Ni II. (Ashall et al 2014). To a large extent the photospheric velocity and the density slope are degenerate so a shallow density slope can be traded off for a lower photospheric velocity.…”

“…modern SN Ia, SN 2014J has been extremely well observed: in γ -rays (Churazov et al 2014;Diehl et al 2014), X-rays (Margutti et al 2014), by Hubble Space Telescope Kelly et al 2014), optical (Amanullah et al 2014;Ashall et al 2014;Goobar et al 2014;Nielsen et al 2014) at high resolution (Welty et al 2014;Graham et al 2015;Jack, Baron & Hauschildt 2015;Ritchey et al 2015), near-infrared (near-IR; Friesen et al 2014;Marion et al 2015), mid-IR (Johansson et al 2014;Telesco et al 2015), polarimetry (Kawabata et al 2014), with rapid photometry (Siverd et al 2015), and in radio (Pérez-Torres et al 2014).…”

Time series of high-resolution spectra of SN 2014J observed with the TIGRE telescope

“…By mid-march, SN 2014J had faded below 12.0 mag, but it was still well placed in the sky for good-quality observations. It has been observed by many telescopes and in different wavelength regions (Telesco, C. M. et al, 2015;Foley, R. J. et al, 2014;Ashall et al 2014;Margutti et al 2014;Pérez-Torres, M. A. et al, 2014), however, none of them have obtained observations with a very detailed time series of optical spectra with higher resolution.…”