Abstract
We present the discovery of ASASSN-18jd (AT 2018bcb), a luminous optical/ ultraviolet(UV)/X-ray transient located in the nucleus of the galaxy 2MASX J22434289- 1659083 at z = 0.1192. Over the year after discovery, Swift UltraViolet and Optical Telescope (UVOT) photometry shows the UV spectral energy distribution of the transient to be well modelled by a slowly shrinking blackbody with temperature T ∼ 2.5 × 104 K, a maximum observed luminosity of Lmax = 4.5+0.6 -0.3 × 1044 erg s-1, and a radiated energy of E = 9.6+1.1 -0.6 × 1051 erg. X-ray data from Swift X-Ray Telescope (XRT) and XMM-Newton show a transient, variable X-ray flux with blackbody and power-law components that fade by nearly an order of magnitude over the following year. Optical spectra show strong, roughly constant broad Balmer emission and transient features attributable to He II, NIII-V, OIII, and coronal Fe. While ASASSN-18jd shares similarities with tidal disruption events (TDEs), it is also similar to the newly discovered nuclear transients seen in quiescent galaxies and faint active galactic nuclei (AGNs).
| Original language | English (US) |
|---|---|
| Pages (from-to) | 2538-2560 |
| Number of pages | 23 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 494 |
| Issue number | 2 |
| DOIs | |
| State | Published - 2020 |
Funding
Observations made with the NASA Galaxy Evolution Explorer (GALEX) were used in the analyses presented in this paper. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. ASAS-SN is supported by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University and NSF grant AST-1515927. Development of ASAS-SN has been supported by NSF grant AST-0908816, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics at the Ohio State University, the Chinese Academy of Sciences South America Center for Astronomy (CASSACA), the Villum Foundation, and George Skestos. This research has made use of the XRT Data Analysis Software (XRTDAS) developed under the responsibility of the ASI Science Data Center (ASDC), Italy. At Penn State the NASA Swift program is supported through contract NAS5-00136. CSK and KZS are supported by NSF grants AST-1515876, AST-1515927, and AST-1814440. CSK is also supported by a fellowship from the Radcliffe Institute for Advanced Study at Harvard University. KA is supported by the Danish National Research Foundation (DNRF132). BJS is supported by NSF grant AST-1908952. SD, SB, and PC acknowledge NSFC 11573003. We acknowledge Telescope Access Program (TAP) funded by the NAOC, CAS, and the Special Fund for Astronomy from the Ministry of Finance. MAT acknowledges support from the DOE CSGF through grant DE-SC0019323. CR acknowledges support from the CONICYT+PAI Convocatoria Nacional subvencion a instalacion en la academia convocatoria año 2017 PAI77170080 and from the Fondecyt Iniciacion grant 11190831. PJV is supported by the National Science Foundation Graduate Research Fellowship Program Under Grant No. DGE-1343012. Support for JLP is provided in part by FONDECYT through the grant 1191038 and by the Ministry of Economy, Development, and Tourism’s Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. MRS is supported by the National Science Foundation Graduate Research Fellowship Program Under Grant No. 1842400. MG is supported by the Polish NCN MAESTRO grant 2014/14/A/ST9/00121. The UCSC team is supported in part by NSF grant AST-1518052, the Gordon and Betty Moore Foundation, the Heising-Simons Foundation, and by a fellowship from the David and Lucile Packard Foundation to RJF. DAHB acknowledges research support through the National Research Foundation (NRF) of South Africa. Some of the observations reported in this paper were obtained with the Southern African Large Telescope (SALT) under the Large Science Programme on transients (2018-2-LSP-001). Polish participation in SALT is funded by grant no. MNiSW DIR/WK/2016/07. Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona University System; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University; and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia. This paper uses data obtained with the MODS spectrographs built with funding from NSF grant AST-9987045 and the NSF Telescope System Instrumentation Program (TSIP) with additional funds from the Ohio Board of Regents and the Ohio State University Office of Research.
Keywords
- Accretion, accretion discs
- Black hole physics
- Galaxies: nuclei
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science