Chen, T.-W., Nicholl, M., Smartt, S.J., Mazzali, P.A., Yates, R.M., Moriya, T.J., Inserra, C., Langer, N., Krühler, T., Pan, Y.-C., Kotak, R., Galbany, L., Schady, P., Wiseman, P., Greiner, J., Schulze, S., Man, A.W.S., Jerkstrand, A., Dennefeld, M., Baltay, C., Bolmer, J., Kankare, E., Knust, F., Maguire, K., Rabinowitz, D., Rostami, S. and Sullivan, M. (2017) The evolution of superluminous supernova LSQ14mo and its interacting host galaxy system. Astronomy & Astrophysics, 602, 1-22, [A9]. (doi:10.1051/0004-6361/201630163).
Abstract
We present and analyse an extensive dataset of the superluminous supernova (SLSN) LSQ14mo (z = 0.256), consisting of a multi-colour light curve from −30 d to +70 d in the rest-frame (relative to maximum light) and a series of six spectra from PESSTO covering −7 d to +50 d. This is among the densest spectroscopic coverage, and best-constrained rising light curve, for a fast-declining hydrogen-poor SLSN. The bolometric light curve can be reproduced with a millisecond magnetar model with ~ 4 M⊙ ejecta mass, and the temperature and velocity evolution is also suggestive of a magnetar as the power source. Spectral modelling indicates that the SN ejected ~ 6 M⊙ of CO-rich material with a kinetic energy of ~7 × 1051 erg, and suggests a partially thermalised additional source of luminosity between −2 d and +22 d. This may be due to interaction with a shell of material originating from pre-explosion mass loss. We further present a detailed analysis of the host galaxy system of LSQ14mo. PESSTO and GROND imaging show three spatially resolved bright regions, and we used the VLT and FORS2 to obtain a deep (five-hour exposure) spectra of the SN position and the three star-forming regions, which are at a similar redshift. The FORS2 spectrum at + 300 days shows no trace of SN emission lines and we place limits on the strength of [O i] from comparisons with other Ic supernovae. The deep spectra provides a unique chance to investigate spatial variations in the host star-formation activity and metallicity. The specific star-formation rate is similar in all three components,as is the presence of a young stellar population. However, the position of LSQ14mo exhibits a lower metallicity, with 12 + log (O/H) = 8.2 in both the R23 and N2 scales (corresponding to ~0.3 Z⊙ ). We propose that the three bright regions in the host system are interacting, which could induce gas flows triggering star formation in low-metallicity regions.
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