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arXiv 1106.3073astro-ph.HE
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Z=0.490时与GRB091127缔合的SN2009nz的光谱分类和爆炸性质

The Spectroscopic Classification and Explosion Properties of SN2009nz Associated with GRB091127 at z=0.490

E. Berger, R. Chornock, T. R. Holmes, R. J. Foley, A. Cucchiara, C. Wolf, Ph. Podsiadlowski, D. B. Fox, K. C. Roth

摘要:

我们目前的光谱观测GRB 091127(z=0.490)在假定的关联超新星SN 2009 nz的峰值。减去宿主星系的后期光谱,我们分离出SN 2009 nz的贡献,并揭示了附近GRB-SNe的典型特征。这明确地表明,GRB 091127伴随着一个宽线的Ic型SN,并将一个宇宙学上的长爆发与一个标准的能量释放(E_gamma,iso ~ 1.1e52 erg)联系起来。SN 2009 nz的光谱与SN 2006 aj非常相似,SN 2003 dh也提供了可接受的匹配,但具有比SNe 1998 bw和2010 bh明显更窄的特征,表明膨胀速度较低。由SiII 6355的吸收特征推断的光球速度v_ph ~ 17,000 km/s确实更接近SNe 2006 aj和2003 dh而不是GRB-SNe。结合测量的速度和光变曲线峰值亮度和宽度,我们估算了以下爆炸参数:MNi ~ 0.35Msun,EK ~ 2.3e51erg,Mej ~ 1.4Msun,与SN 2006 aj的结果相似。这些性质表明,对于具有较低E_K和M_ej的GRB-SNe,SN 2009 nz遵循较低M_Ni的趋势。同样重要的是,由于GRB 091127是一个典型的宇宙学爆发,SN 2009 nz与SN 2006 aj的相似性要么让人怀疑XRF 060218/SN 2006 aj是由中子星提供动力的说法,要么表明中央引擎的性质编码在SN属性中,而不是在瞬发发射中。未来的GRB-SNe在z > 0.3时的光谱,包括适当扣除宿主星系的贡献,将揭示标准长GRB的SN性质的完全分散,与次能量和标准GRB相关的SNe之间的关系,以及相关SN类型的潜在分散。

英文摘要:

We present spectroscopic observations of GRB091127 (z=0.490) at the peak of the putative associated supernova, SN2009nz. Subtracting a late-time spectrum of the host galaxy, we isolate the contribution of SN2009nz and uncover broad features typical of nearby GRB-SNe. This establishes unambiguously that GRB091127 was accompanied by a broad-lined Type Ic SN, and links a cosmological long burst with a standard energy release (E_gamma,iso ~ 1.1e52 erg) to a massive star progenitor. The spectrum of SN2009nz closely resembles that of SN2006aj, with SN2003dh also providing an acceptable match, but has significantly narrower features than SNe 1998bw and 2010bh, indicative of a lower expansion velocity. The photospheric velocity inferred from the SiII 6355 absorption feature, v_ph ~ 17,000 km/s, is indeed closer to that of SNe 2006aj and 2003dh than to the other GRB-SNe. Combining the measured velocity with the light curve peak brightness and width, we estimate the following explosion parameters: M_Ni ~ 0.35 M_sun, E_K ~ 2.3e51 erg, and M_ej ~ 1.4 M_sun, similar to those of SN2006aj. These properties indicate that SN2009nz follows a trend of lower M_Ni for GRB-SNe with lower E_K and M_ej. Equally important, since GRB091127 is a typical cosmological burst, the similarity of SN2009nz to SN2006aj either casts doubt on the claim that XRF060218/SN2006aj was powered by a neutron star, or indicates that the nature of the central engine is encoded in the SN properties but not in the prompt emission. Future spectra of GRB-SNe at z > 0.3, including proper subtraction of the host galaxy contribution, will shed light on the full dispersion of SN properties for standard long GRBs, on the relation between SNe associated with sub-energetic and standard GRBs, and on a potential dispersion in the associated SN types.

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