On the incidence of episodic accretion in Class I YSOs from VVV
On the incidence of episodic accretion in Class I YSOs from VVV
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DOI：
10.1093/mnras/stad3780
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发表时间：
2024-01
影响因子：
4.8
通讯作者：
C. Contreras Peña-C.-Contreras Peña-2124046337;P. W. Lucas;Zhen Guo;L. Smith
中科院分区：
文献类型：
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作者：
C. Contreras Peña-C.-Contreras Peña-2124046337;P. W. Lucas;Zhen Guo;L. Smith
偶发性吸积是解释在年轻星团中观测到的光度扩散的竞争性模型之一。这些短暂的高吸积事件也可能对行星形成产生强烈影响。由于吸积速率的巨大变化，对年轻恒星天体（YSOs）的高振幅变异性的观测为偶发性吸积提供了直接的观测证据。然而，这些事件发生的频率以及在yso中是否普遍存在间歇性吸积仍然存在不确定性。为了确定I类yso爆发的频率，我们在这一进化阶段建立了一个庞大而强大的对象样本，并在Via Lactea调查的Vista变量的VIRAC2数据库中搜索高振幅近红外（ΔKS >2等）变化率。通过补充近红外（2MASS和DENIS）和中红外（WISE/Neo-WISE）数据，我们发现从约7000个I类YSOs中，有97个物体可以被归类为爆发变量YSOs。爆发的持续时间从几个月到超过9年不等，并且覆盖了相似的振幅范围。然而，ΔKS bbb50等值仅在持续时间超过9年的爆发中观察到。考虑到完整性和污染的不同影响，我们估计I类YSOs的偶发性吸积发生率在2%至3%之间。最后，我们确定了长期爆发（又称FUors）的复发时间尺度为$\tau =1.75^{+1.12}_{-0.87}$ kyr。后一个值与先前的估计一致，并符合在较年轻的进化阶段爆发更高频率的预期。
Episodic accretion is one of the competing models to explain the observed luminosity spread in young stellar clusters. These short-lived high accretion events could also have a strong impact on planet formation. Observations of high-amplitude variability in young stellar objects (YSOs) due to large changes in the accretion rate provide direct observational evidence for episodic accretion. However, there are still uncertainties in the frequency of these events and if episodic accretion is universal among YSOs. To determine the frequency of outbursts in Class I YSOs, we built a large and robust sample of objects at this evolutionary stage, and searched for high-amplitude near-infrared (ΔKS > 2 mag) variability in the VIRAC2 database of the Vista Variables in the Via Lactea survey. By complementing with near-IR (2MASS and DENIS) and mid-IR (WISE/Neo-WISE) data, we find that from ∼7000 Class I YSOs, 97 objects can be classified as eruptive variable YSOs. The duration of the outbursts vary from a few months to longer than 9 yr, and cover a similar range of amplitudes. Values of ΔKS > 5 mag, however, are only observed in outbursts with duration longer than 9 yr. When considering different effects of completeness and contamination, we estimate that the incidence of episodic accretion in Class I YSOs is between 2 and 3 per cent. Finally, we determine a recurrence time-scale of long-term outbursts (a.k.a FUors) of $\tau =1.75^{+1.12}_{-0.87}$ kyr. The latter value agrees with previous estimates and is in line with the expectations of higher frequency of FUor outbursts during younger stages of evolution.