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外文期刊>The Astrophysical journal
>DISCOVERY OF PRECURSOR LUMINOUS BLUE VARIABLE OUTBURSTS IN TWO RECENT OPTICAL TRANSIENTS: THE FITFULLY VARIABLE MISSING LINKS UGC 2773-OT AND SN 2009ip
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DISCOVERY OF PRECURSOR LUMINOUS BLUE VARIABLE OUTBURSTS IN TWO RECENT OPTICAL TRANSIENTS: THE FITFULLY VARIABLE MISSING LINKS UGC 2773-OT AND SN 2009ip
We present progenitor-star detections, light curves, and optical spectra of supernova (SN) 2009ip and the 2009 optical transient in UGC 2773 (U2773-OT), which were not genuine SNe. Precursor variability in the decade before outburst indicates that both of the progenitor stars were luminous blue variables (LBVs). Their pre-outburst light curves resemble the S Doradus phases that preceded giant eruptions of the prototypical LBVs η Carinae and SN 1954J (V12 in NGC 2403), with intermediate progenitor luminosities. Hubble Space Telescope detections a decade before discovery indicate that the SN 2009ip and U2773-OT progenitors were supergiants with likely initial masses of 50-80 M ☉ and 20 M ☉, respectively. Both outbursts had spectra befitting known LBVs, although in different physical states. SN 2009ip exhibited a hot LBV spectrum with characteristic speeds of 550 km s–1, plus evidence for faster material up to 5000 km s–1, resembling the slow Homunculus and fast blast wave of η Carinae. In contrast, U2773-OT shows a forest of narrow absorption and emission lines comparable to that of S Dor in its cool state, plus [Ca II] emission and an infrared excess indicative of dust, similar to SN 2008S and the 2008 optical transient in NGC 300 (N300-OT). The [Ca II] emission is probably tied to a dusty pre-outburst environment, and is not a distinguishing property of the outburst mechanism. The LBV nature of SN 2009ip and U2773-OT may provide a critical link between historical LBV eruptions, while U2773-OT may provide a link between LBVs and the unusual dust-obscured transients SN 2008S and N300-OT. Future searches will uncover more examples of precursor LBV variability of this kind, providing key clues that may help unravel the instability driving LBV eruptions in massive stars.
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机译：我们介绍了不是真正的SNe的UGC 2773（U2773-OT）中的超新星（SN）2009ip和2009光学瞬变的祖星检测，光曲线和光谱。爆发前十年中的前兆变化表明，两个祖星都是发光的蓝色变量（LBV）。它们的爆发前光曲线类似于S Doradus阶段，该阶段在原型LBVηCarinae和SN 1954J（NGC 2403中为V12）的巨大爆发之前出现，并具有中等祖细胞发光度。哈勃太空望远镜在发现前十年的探测结果表明，SN 2009ip和U2773-OT祖细胞是超巨型细胞，初始质量可能分别为50-80 M☉和20 M☉。尽管处于不同的物理状态，两次爆发的光谱都符合已知的LBV。 SN 2009ip展示了一个热的LBV光谱，其特征速度为550 km s-1，并且有证据表明，高达5000 km s-1的材料更快，类似于慢的Homunculus和ηCarinae的快速爆炸波。相比之下，U2773-OT的森林处于狭窄的吸收和发射谱线，与处于寒冷状态的S Dor相当，加上[Ca II]发射和指示粉尘的红外过量，类似于SN 2008S和2008年的光学瞬变。 NGC 300（N300-OT）。 [Ca II]的排放可能与多尘的爆发前环境有关，而不是突出机制的区别。 SN 2009ip和U2773-OT的LBV性质可能提供了历史LBV爆发之间的关键链接，而U2773-OT可能提供了LBV与异常的尘埃瞬变SN 2008S和N300-OT之间的链接。未来的搜索将发现更多此类前兆LBV变异性的例子，提供关键线索，可能有助于揭开驱动大质量恒星LBV爆发的不稳定性。
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