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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - A flash of polarized optical light points to an aspherical ‘cow’
AU - Maund, Justyn R
AU - Höflich, Peter A
AU - Steele, Iain A
AU - Yang, Yi
AU - Wiersema, Klaas
AU - Kobayashi, Shiho
AU - Jordana-Mitjans, Nuria
AU - Mundell, Carole
AU - Gomboc, Andreja
AU - Guidorzi, Cristiano
AU - Smith, Robert J
PY - 2023/5/31
Y1 - 2023/5/31
N2 - The astronomical transient AT2018cow is the closest example of the new class of luminous, fast blue optical transients (FBOTs). Liverpool Telescope RINGO3 observations of AT 2018cow are reported here, which constitute the earliest polarimetric observations of an FBOT. At 5.7 days post-explosion, the optical emission of AT2018cow exhibited a chromatic polarization spike that reached $\sim 7{{\%}}$ at red wavelengths. This is the highest intrinsic polarization recorded for a non-relativistic explosive transient, and is observed in multiple bands and at multiple epochs over the first night of observations, before rapidly declining. The apparent wavelength dependence of the polarization may arise through depolarization or dilution of the polarized flux, due to conditions in AT 2018cow at early times. A second ‘bump’ in the polarization is observed at blue wavelengths at ∼12 days. Such a high polarization requires an extremely aspherical geometry that is only apparent for a brief period (<1 day), such as shock breakout through an optically thick disk. For a disk-like configuration, the ratio of the thickness to radial extent must be $\sim 10{{\%}}$.
AB - The astronomical transient AT2018cow is the closest example of the new class of luminous, fast blue optical transients (FBOTs). Liverpool Telescope RINGO3 observations of AT 2018cow are reported here, which constitute the earliest polarimetric observations of an FBOT. At 5.7 days post-explosion, the optical emission of AT2018cow exhibited a chromatic polarization spike that reached $\sim 7{{\%}}$ at red wavelengths. This is the highest intrinsic polarization recorded for a non-relativistic explosive transient, and is observed in multiple bands and at multiple epochs over the first night of observations, before rapidly declining. The apparent wavelength dependence of the polarization may arise through depolarization or dilution of the polarized flux, due to conditions in AT 2018cow at early times. A second ‘bump’ in the polarization is observed at blue wavelengths at ∼12 days. Such a high polarization requires an extremely aspherical geometry that is only apparent for a brief period (<1 day), such as shock breakout through an optically thick disk. For a disk-like configuration, the ratio of the thickness to radial extent must be $\sim 10{{\%}}$.
KW - Space and Planetary Science
KW - Astronomy and Astrophysics
KW - Technique:polarimetric
KW - Stars
KW - Supernovae:individual:AT 2018cow
U2 - 10.1093/mnras/stad539
DO - 10.1093/mnras/stad539
M3 - Journal article
VL - 521
SP - 3323
EP - 3332
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 3
ER -