{
  "id": "2108.12431",
  "version": "v1",
  "published": "2021-08-27T18:00:00.000Z",
  "updated": "2021-08-27T18:00:00.000Z",
  "title": "The nascent milliquasar VT J154843.06+220812.6: tidal disruption event or extreme accretion-state change?",
  "authors": [
    "Jean J. Somalwar",
    "Vikram Ravi",
    "Dillon Dong",
    "Matthew Graham",
    "Gregg Hallinan",
    "Casey Law",
    "Wenbin Lu",
    "Steven T. Myers"
  ],
  "comment": "30 pages, 11 figures, 5 tables. Submitted to ApJ",
  "categories": [
    "astro-ph.HE",
    "astro-ph.GA"
  ],
  "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.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2021-08-27T18:00:00.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "tidal disruption event",
      "extreme accretion-state change",
      "nascent milliquasar vt",
      "vt j1548",
      "radio flare"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 30,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}