论文标题
M33郊区的一颗狼射线之星的新的且异常的LBV爆发
A new and unusual LBV-like outburst from a Wolf-Rayet star in the outskirts of M33
论文作者
论文摘要
MCA-1B（也称为UIT003）是M33西部郊区的发光热星，在20年前被分类为OFPE/WN9的光谱类型，然后确定为候选发光蓝色变量（LBV）。 Palomar瞬态工厂数据显示，这颗星在2010年变亮，其光曲线类似于M31中经典的LBV恒星。其他OFPE/WN9恒星爆发为LBV，但MCA-1B是不寻常的，因为它仍然很热。它在整个喷发过程中显示出WN型光谱，而LBV通常会变得凉爽。 MCA-1B显示辐射光度的亮度差不多四倍，半径增加了一倍，但其温度保持在29kk左右。随着它的褪色，它转移到更高的温度，表现出WN7/WN8型频谱，并使风速加倍。 MCA-1B让人想起一些超新星冒名顶替者，其位置类似于SN 2009IP的孤立环境。它与HD5980（在SMC中）和GR 290（也在M33中）最相似。尽管这两个LBV在喷发中表现出B型光谱，但MCA-1B是第一个清晰的案例，始终持续存在狼射线（WR）光谱。 MCA-1B，HD 5980和GR 290一起构成了一类WN型LBV，与S Doradus LBV不同。在低金属性的LBV，可能是二进制的LBV/WR过渡的情况下，它们最有趣的是，它们可能是〜IBN Supernova祖细胞的可能性。
MCA-1B (also called UIT003) is a luminous hot star in the western outskirts of M33, classified over 20yr ago with a spectral type of Ofpe/WN9 and identified then as a candidate luminous blue variable (LBV). Palomar Transient Factory data reveal that this star brightened in 2010, with a light curve resembling that of the classic LBV star AFAnd in M31. Other Ofpe/WN9 stars have erupted as LBVs, but MCA-1B was unusual because it remained hot. It showed a WN-type spectrum throughout its eruption, whereas LBVs usually get much cooler. MCA-1B showed an almost four-fold increase in bolometric luminosity and a doubling of its radius, but its temperature stayed around 29kK. As it faded, it shifted to even hotter temperatures, exhibiting a WN7/WN8-type spectrum, and doubling its wind speed. MCA-1B is reminiscent of some supernova impostors, and its location resembles the isolated environment of SN 2009ip. It is most similar to HD5980 (in the SMC) and GR 290 (also in M33). Whereas these two LBVs exhibited B-type spectra in eruption, MCA-1B is the first clear case where a Wolf-Rayet (WR) spectrum persisted at all times. Together, MCA-1B, HD 5980, and GR 290 constitute a class of WN-type LBVs, distinct from S Doradus LBVs. They are most interesting in the context of LBVs at low metallicity, a possible post-LBV/WR transition in binaries, and as likely Type~Ibn supernova progenitors.
