Echelle spectra of SN2014J from the Apache Point Observatory 3.5m telescope, UT January 27 and January 30, 2014
ATel #5859; Adam M. Ritchey (UNiversity of Washington), Daniel E. Welty (University of Chicago), Julie A. Dahlstrom (Carthage College), Donald G. York (University of Chicago)
on 7 Feb 2014; 02:25 UT
Credential Certification: Donald York (firstname.lastname@example.org)
Subjects: Optical, Supernovae
Referred to by ATel #: 5965
Optical spectra of SN2014J were recorded with the ARC echelle spectrograph at Apache Point Observatory, at approximately UT Jan. 27.2 (7 spectra, 8400 s) and UT Jan. 30.4, (6 spectra, 7200s), through thin clouds in seeing averaging 1.0 arcsec. The resolving power is 31,500. Useful interstellar spectra were obtained from 3850A to 9000A; estimated S/N values (photon counts only) near 6563A are 500 on Jan 27 and 400 on Jan 30, and about 1/3 those values at Ca II 3933A.
Interstellar lines of K I, Na I, and Ca II are clearly seen; lines of CH, CH+, CN, and Ca I are also observed. As noted by Cox et al. (Atel #5797), many interstellar components are evident. The strongest blend of K I components, due to gas in M82, is centered at about v_LSR = 105 km/s, with FWHM = 50 km/s; there are weaker components to the red. The lines of Na I and Ca II, while much deeper, have similar structure but show additional components extending to 250 km/s. Preliminary column densities (dex) are 12.3 (K I), 14.3 (CH+), 13.7 (CH), 12.9 (CN), and 11.3 (Ca I). The equivalent width of CH+ 4232 is as large as the largest known in our Galaxy, and the ratio N(CH+)/N(CH) is similar to the highest Galactic values (excepting the very high ratios noted in the Pleiades). Estimates of N(H I), N(H2), and E(B-V) derived from the abundances of the observed species should account for the metalicity and ambient radiation field in the gas in M82.
Diffuse interstellar bands detected in the M82 gas include 4501.8, 4726.8, 4963.9, 5487.7, 5508.1, 5780.5*, 5797.1*, 5849.8, 6196.0*, 6204.5*, 6269.9, 6283.8, 6379.3*, 6613.6; a number of others are likely present. Asterisks confirm previous reported detections (Atel #5816). On Jan 27, equivalent widths were 351 +/- 15 mA (5780.5A), 229 +/- 8 mA (5797.1A), 46 +/- 4 mA (6196.0A), and 223 +/-8 mA (6613.6). Errors are one sigma errors including those from continuum drawing and photon noise, added in quadrature. The errors for DIBs 5780.5 and 5797.1 are dominated by continuum uncertainties due to the complex atomic profiles, blends of DIBs in the supernova spectrum and blends with Galactic DIBs. The widths and equivalent widths of 5780.5 and 5797.1 are smaller than those reported by Cox et al. (Atel #5797), however, possibly for reasons related to the choice of continuum. More analysis is needed. No changes were noted in the strengths or profiles of those four bands between Jan. 27 and Jan. 30, to integrated precisions of < 10mA, no matter how the continua were (consistently) drawn.
The M82 DIBs are typically broader than those seen for simple Galactic sight lines, due presumably to blending of contributions from the many narrow interstellar components; they are likely unsaturated (based on comparisons with Galactic values). Some differences in DIB behavior/ratios (M82 vs. typical Galactic) are apparent, however. The most obvious noted so far are: (a) 5780.5 is weak compared to 5797.1, 6196.0, and 6613.6; (b) the ratio of 6376.1 to DIB 6379.3 is at least 4x higher.
Further high resolution observations are encouraged -- to get high S/N by averaging over many nights (after determining whether variations from night-to-night do or do not occur).