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arXiv 1002.0635astro-ph.SRastro-ph.CO
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大质量恒星爆发的多样性I:SN 2009 ip、UGC 2773 OT2009-1及其祖先的观测

The Diversity of Massive Star Outbursts I: Observations of SN 2009ip, UGC 2773 OT2009-1, and Their Progenitors

Ryan J. Foley, Edo Berger, Ori Fox, Emily M. Levesque, Peter J. Challis, Inese I. Ivans, James E. Rhoads, Alicia M. Soderberg

摘要:

尽管SN 2009 ip和UGC 2773 OT 2009 -1都是亮蓝变星(LBV)的爆发,但它们的前身星、光谱、星周环境和可能产生爆发的物理机制都非常不同。根据喷发前的HST图像,我们确定SN 2009 ip和UGC 2773 OT 2009 -1的初始质量分别为>60和>25 M_sun。光谱学显示SN 2009 ip在峰值时有10,000 K的光球层,其光谱主要是窄的H巴耳末辐射,类似于经典的LBV巨爆发,也被称为“超新星冒名顶替者”。“UGC 2773 OT 2009 -1的光谱也有窄的H α发射,由吸收线森林主导,类似于F型超巨星。在SN 2009 ip的后期光谱中出现了蓝移吸收线,对应于速度为2000 - 7000公里/秒的喷出物-这是对LBV爆发的前所未有的观察,表明该事件是超音速爆炸的结果,而不是亚音速爆发。吸收线的速度在两个时期之间增加,这表明有两次快速连续的爆炸。与高速吸收线的出现同时发生的快速衰减和再增亮事件与双爆炸模型一致。UGC 2773 OT 2009 -1的光谱和光度学中存在近红外过量,这与~2100 K尘埃排放一致。我们比较了这两个事件的性质,并将它们放在其他已知的大质量恒星爆发的背景下,如eta Car,NGC 300 OT 2008 -1和SN 2008 S。这种定性分析表明,大质量恒星爆发有许多物理差异,这些差异可以表现为这两个有趣物体中的不同观测值。

英文摘要:

Despite both being outbursts of luminous blue variables (LBVs), SN 2009ip and UGC 2773 OT2009-1 have very different progenitors, spectra, circumstellar environments, and possibly physical mechanisms that generated the outbursts. From pre-eruption HST images, we determine that SN 2009ip and UGC 2773 OT2009-1 have initial masses of >60 and >25 M_sun, respectively. Optical spectroscopy shows that at peak SN 2009ip had a 10,000 K photosphere and its spectrum was dominated by narrow H Balmer emission, similar to classical LBV giant outbursts, also known as "supernova impostors." The spectra of UGC 2773 OT2009-1, which also have narrow H alpha emission, are dominated by a forest of absorption lines, similar to an F-type supergiant. Blueshifted absorption lines corresponding to ejecta at a velocity of 2000 - 7000 km/s are present in later spectra of SN 2009ip -- an unprecedented observation for LBV outbursts, indicating that the event was the result of a supersonic explosion, rather than a subsonic outburst. The velocity of the absorption lines increases between two epochs, suggesting that there were two explosions in rapid succession. A rapid fading and rebrightening event concurrent with the onset of the high-velocity absorption lines is consistent with the double-explosion model. A near-infrared excess is present in the spectra and photometry of UGC 2773 OT2009-1 that is consistent with ~2100 K dust emission. We compare the properties of these two events and place them in the context of other known massive star outbursts such as eta Car, NGC 300 OT2008-1, and SN 2008S. This qualitative analysis suggests that massive star outbursts have many physical differences which can manifest as the different observables seen in these two interesting objects.

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