The Accretion History of EX Lup: A Century of Bursts, Outbursts, and Quiescence

IF 4.8 2区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS
Mu-Tian 牧天 Wang 王, Gregory J. 雷歌 Herczeg 沈, Hui-Gen 慧根 Liu 刘, Min 敏 Fang 房, Doug Johnstone, Ho-Gyu Lee, Frederick M. Walter, Franz-Josef Hambsch, Carlos Contreras Peña, Jeong-Eun Lee, Mervyn Millward, Andrew Pearce, Berto Monard, Lihang 立杭 Zhou 周
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Abstract

Abstract EX Lup is the archetype for the class of young stars that undergoes repeated accretion outbursts of ∼5 mag at optical wavelengths that last for months. Despite extensive monitoring that dates back 130 yr, the accretion history of EX Lup remains mostly qualitative and has large uncertainties. We assess historical accretion rates of EX Lup by applying correlations between optical brightness and accretion, developed on multi-band magnitude photometry of the ∼2 mag optical burst in 2022. Two distinct classes of bursts occur: major outbursts (Δ V ∼ 5 mag) have year-long durations, are rare, reach accretion rates of M ̇ acc 10 7 M ⊙ yr −1 at peak, and have a total accreted mass of around 0.1 Earth mass. The characteristic bursts (Δ V ∼ 2 mag) have durations of ∼2–3 months, are more common, reach accretion rates of M ̇ acc 10 8 M ⊙ yr −1 at peak, and have a total accreted mass of around 10 −3 Earth masses. The distribution of total accreted mass in the full set of bursts is poorly described by a power law, which suggests different driving causes behind the major outburst and characteristic bursts. The total mass accreted during two classes of bursts is around 2 times the masses accreted during quiescence. Our analysis of the light curves reveals a color-dependent time lag in the 2022 post-burst light curve, attributed to the presence of both hot and cool spots on the stellar surface.
exlup的吸积史:一个世纪的爆发、爆发和静止
exlup是一类年轻恒星的原型,它们经历了持续数月的光学波长的~ 5等重复吸积爆发。尽管进行了130年的广泛监测,但EX - Lup的吸积历史仍然主要是定性的,存在很大的不确定性。我们通过应用光学亮度和吸积之间的相关性来评估EX - Lup的历史吸积速率,这是在2022年的~ 2磁光爆发的多波段光度法上发展起来的。爆发有两种不同的类型:大爆发(Δ V ~ 5等)持续时间长达一年,非常罕见,吸积率峰值达到M³acc ~ 10−7 M⊙yr−1,总吸积质量约为0.1地球质量。特征性爆发(Δ V ~ 2等)持续时间为~ 2 - 3个月,较为常见,吸积速率峰值可达M³acc ~ 10−8 M⊙yr−1,总吸积质量约为10−3个地球质量。幂律不能很好地描述所有爆发中总吸积质量的分布,这表明主要爆发和特征爆发背后的驱动原因不同。在两类爆发期间增加的总质量大约是在静止期间增加的质量的2倍。我们对光曲线的分析揭示了2022年爆发后光曲线中与颜色相关的时间滞后,这归因于恒星表面存在热点和冷点。
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来源期刊
Astrophysical Journal
Astrophysical Journal 地学天文-天文与天体物理
CiteScore
8.40
自引率
30.60%
发文量
2854
审稿时长
1 months
期刊介绍: The Astrophysical Journal is the foremost research journal in the world devoted to recent developments, discoveries, and theories in astronomy and astrophysics.
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