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arXiv 2108.12431astro-ph.HEastro-ph.GA
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新生的毫米波VT J154843 .06+220812.6:潮汐破裂事件还是极端的吸积状态变化?

The nascent milliquasar VT J154843.06+220812.6: tidal disruption event or extreme accretion-state change?

Jean J. Somalwar, Vikram Ravi, Dillon Dong, Matthew Graham, Gregg Hallinan, Casey Law, Wenbin Lu, Steven T. Myers

摘要:

我们提出了详细的多波长跟踪的核射电耀斑,VT J154843.06+220812.6,以下VT J1548。VT J1548被选为VLA巡天(VLASS)在3 GHz观测中的${\sim}1$ mJy射电耀斑。它位于一个低质量($\log M_{\rm BH}/M_\odot \sim6$)宿主星系的核心,过去活动星系核活动很弱或没有活动星系核活动。VT J1548与WISE巡天中缓慢上升(多年)的明亮中红外耀斑有关,峰值在${\sim}10\%L_{\rm edd.}$。没有检测到相关的光学瞬态,虽然我们不能排除一个短期的,早期的光学耀斑有限的数据。在${\sim}10^{42}$ erg s $^{-1}$探测到恒定的晚期(耀斑后数年的${\sim}3$)X射线发射。无线电SED是一致的同步辐射从流出事件上的非对称介质。后续的光谱显示了短暂的、明亮的、高电离日冕线发射($[{\rm Fe\,X}]\,λ6375,[{\rm Fe\,XI}]\,λ7894,[{\rm S\,XII}]\,λ7612$)。还检测到瞬时宽H $α$,但没有相应的宽H $β$发射,表明高核消光。我们解释这一事件,无论是潮汐破坏事件或极端耀斑的活动星系核,在这两种情况下,掩盖了尘埃环面。虽然这些单独的属性已经在以前的瞬态中观察到,但这种组合是前所未有的。这一事件突出了在所有波段进行搜索的重要性,以收集跨越可观测特性和可能触发因素范围的核耀斑样本。

英文摘要:

We present detailed multiwavelength follow up of a nuclear radio flare, VT J154843.06+220812.6, hereafter VT J1548. VT J1548 was selected as a ${\sim}1$ mJy radio flare in 3 GHz observations from the VLA Sky Survey (VLASS). It is located in the nucleus of a low mass ($\log M_{\rm BH}/M_\odot \sim6$) host galaxy with weak or no past AGN activity. VT J1548 is associated with a slow rising (multiple year), bright mid IR flare in the WISE survey, peaking at ${\sim}10\%L_{\rm edd.}$. No associated optical transient is detected, although we cannot rule out a short, early optical flare given the limited data available. Constant late time (${\sim}3$ years post-flare) X-ray emission is detected at ${\sim}10^{42}$ erg s$^{-1}$. The radio SED is consistent with synchrotron emission from an outflow incident on an asymmetric medium. A follow-up, optical spectrum shows transient, bright, high-ionization coronal line emission ($[{\rm Fe\,X}]\,λ6375,[{\rm Fe\,XI}]\,λ7894,[{\rm S\,XII}]\,λ7612$). Transient broad H$α$ is also detected but without corresponding broad H$β$ emission, suggesting high nuclear extinction. We interpret this event as either a tidal disruption event or an extreme flare of an active galactic nucleus, in both cases obscured by a dusty torus. Although these individual properties have been observed in previous transients, the combination is unprecedented. This event highlights the importance of searches across all wave bands for assembling a sample of nuclear flares that spans the range of observable properties and possible triggers.

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