%0 Generic %1 somalwar2021nascent %A Somalwar, Jean J. %A Ravi, Vikram %A Dong, Dillon %A Graham, Matthew %A Hallinan, Gregg %A Law, Casey %A Lu, Wenbin %A Myers, Steven T. %D 2021 %K library %T The nascent milliquasar VT J154843.06+220812.6: tidal disruption event or extreme accretion-state change? %U http://arxiv.org/abs/2108.12431 %X 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 $\sim1$ mJy radio flare in 3 GHz observations from the VLA Sky Survey (VLASS). It is located in the nucleus of a low mass ($M_BH/M_\sim6$) 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 $\sim10\%L_edd.$. No associated optical transient is detected, although we cannot rule out a short, early optical flare given the limited data available. Constant late time ($\sim3$ years post-flare) X-ray emission is detected at $\sim10^42$ 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 ($Fe\,X\,6375,Fe\,XI\,7894,\rm S\,XII\,7612$). Transient broad H$\alpha$ is also detected but without corresponding broad H$\beta$ 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.

@misc{somalwar2021nascent, abstract = {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 ($[{\rm Fe\,X}]\,\lambda 6375,[{\rm Fe\,XI}]\,\lambda 7894,[{\rm S\,XII}]\,\lambda 7612$). Transient broad H$\alpha$ is also detected but without corresponding broad H$\beta$ 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.}, added-at = {2021-08-31T06:44:02.000+0200}, author = {Somalwar, Jean J. and Ravi, Vikram and Dong, Dillon and Graham, Matthew and Hallinan, Gregg and Law, Casey and Lu, Wenbin and Myers, Steven T.}, biburl = {https://www.bibsonomy.org/bibtex/2770d55d67a808285c49a10089c15ca03/gpkulkarni}, description = {The nascent milliquasar VT J154843.06 220812.6: tidal disruption event or extreme accretion-state change?}, interhash = {0b22b7f820a12e5fd7d6950ae645fd32}, intrahash = {770d55d67a808285c49a10089c15ca03}, keywords = {library}, note = {cite arxiv:2108.12431Comment: 30 pages, 11 figures, 5 tables. Submitted to ApJ}, timestamp = {2021-08-31T06:44:02.000+0200}, title = {The nascent milliquasar VT J154843.06+220812.6: tidal disruption event or extreme accretion-state change?}, url = {http://arxiv.org/abs/2108.12431}, year = 2021 }