Infrared spectropolarimetric detection of intrinsic polarization from a core-collapse supernova
Infrared spectropolarimetric detection of intrinsic polarization from a core-collapse supernova
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DOI：
10.1038/s41550-021-01320-4
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发表时间：
2021-02
期刊：
影响因子：
14.1
通讯作者：
S. Tinyanont;M. Millar-Blanchaer;M. Kasliwal;D. Mawet;D. Leonard;M. Bulla;K. De;N. Jovanovic;M. Hankins;G. Vasisht;E. Serabyn
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作者：
S. Tinyanont;M. Millar-Blanchaer;M. Kasliwal;D. Mawet;D. Leonard;M. Bulla;K. De;N. Jovanovic;M. Hankins;G. Vasisht;E. Serabyn
大质量恒星以核心坍缩超新星（CCSN）的形式爆炸死亡。导致坍缩恒星反弹成爆炸的确切物理过程尚不清楚，解决这一问题的关键可能在于测量CCSNe喷射物的形状。光谱偏振法是对银河系和麦哲伦星云之外的CCSNe进行测量的唯一方法。我们提出了利用帕洛玛天文台的新型高灵敏度WIRC+Pol仪器对CCSN进行红外光谱偏振检测，该仪器可以以~0.1%的偏振精度观测到20 Mpc的CCSN（震级dem = - 17 mag）。红外光谱偏振法比光学光谱偏振法受星周和星际介质中尘埃散射的影响更小，因此对超新星喷射物的内在几何形状提供了更小的偏差探测。与SN 1987a类似的超新星SN 2018hna，在爆炸182天后的天空中，呈现出2.0±0.3%的连续极化，J波段方向为~160°。假设SN 1987A的几何形状像SN 1987A一样长，我们推断出喷射轴比<0.48，对称轴指向70°的位置角。轴向比值与SN 1987A相似，表明两个CCSNe可能具有相同的几何形状和倾角。我们的数据不排除扁圆抛射的可能。我们还在J波段观测到另外一颗CCSN和两颗热核超新星。超新星2020oi是一颗位于梅西耶100中的剥离包膜型Ic SN，其峰值光带宽为0.37±0.09%，表明其不对称性为10%或宿主星际极化。Ia型sne2019ein和2020ue的近峰光偏振度分别<0.33%和<1.08%，表明不对称度分别小于10%和20%。
Massive stars die an explosive death as a core-collapse supernova (CCSN). The exact physical processes that cause the collapsing star to rebound into an explosion are not well understood, –, and the key to resolving this issue may lie in the measurement of the shape of CCSNe ejecta. Spectropolarimetry is the only way to perform this measurement for CCSNe outside the Milky Way and Magellanic Clouds. We present the infrared spectropolarimetric detection of a CCSN enabled by the new highly sensitive WIRC+Pol instrument at Palomar Observatory, which can observe CCSNe (magnitudeM= −17 mag) out to 20 Mpc at ~0.1% polarimetric precision. Infrared spectropolarimetry is less affected than optical spectropolarimetry by dust scattering in the circumstellar and interstellar media, thereby providing a less biased probe of the intrinsic geometry of the supernova ejecta. SN 2018hna, a SN 1987A-like explosion, shows 2.0 ± 0.3% continuum polarization in the J band oriented at ~160° on sky 182 days after the explosion. Assuming a prolate geometry as in SN 1987A, we infer an ejecta axis ratio of <0.48 with the axis of symmetry pointing at a 70° position angle. The axis ratio is similar to that of SN 1987A, suggesting that the two CCSNe may share intrinsic geometry and inclination angles. Our data do not rule out oblate ejecta. We also observe one other CCSN and two thermonuclear supernovae in the J band. Supernova 2020oi, a stripped-envelope type Ic SN in Messier 100 has broadbandp= 0.37 ± 0.09% at peak light, indicative of either a 10% asymmetry or host interstellar polarization. The type Ia SNe 2019ein and 2020ue have <0.33% and <1.08% polarization near peak light, indicative of asymmetries of less than 10% and 20%, respectively.