SDSS1335+0728: The awakening of a ~10⁶ M⊙ black hole

Creators: Sánchez-Sáez, P.; Hernandez-Garcia, L.; Bernal, S.; Bayo, A.; Calistro Rivera, G.; Bauer, F. E.; Ricci, C.; Merloni, A.; Graham, M. J.¹; Cartier, R.; Arévalo, P.; Assef, R. J.; Concas, A.; Homan, D.; Krumpe, M.; Lira, P.; Malyali, A.; Martínez-Aldama, M. L.; Muñoz Arancibia, A. M.; Rau, A.; Bruni, G.; Förster, F.; Pavez-Herrera, M.; Tubín-Arenas, D.; Brightman, M.

1. California Institute of Technology

Abstract

Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ~10⁶ M⊙ black hole (BH) that is currently in the process of ‘turning on’.

Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728.

Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra.

Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region.

Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ~10⁶ M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGN observed in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour.

Copyright and License

© The Authors 2024. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication.

Acknowledgement

The authors acknowledge support from the National Agency for Research and Development (ANID) grants: Millennium Science Initiative Program ICN12_12009 (PSS,LHG,FEB,FF,MPH,AMMA), Millenium Nucleus NCN19_058 (SB,PA,PL,MLMA), CATA-BASAL - FB210003 (FEB,CR,RJA), BASAL FB210005 (AMMA), FONDECYT Regular - 1241005 (FEB), 1230345 (CR), 1201748 (PL), 1200710 (FF), 1231718 (RJA). SB acknowledges financial support from ANID Becas 21212344, and the hospitality of ESO under the SSDF Project 28/23D. AB acknowledges financial support from Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – EXC 2094 – 39078331. DH acknowledges support from DLR grant FKZ 50 OR 2003. MK acknowledges support from DLR grant FKZ 50 OR 2307. DT acknowledges support by DLR grant FKZ 50 OR 2203. AM acknowledges support by DLR under the grant 50 QR 2110 (XMM_NuTra). PA and SB acknowledge support from the Max-Planck Society through a Partner Group grant. MJA acknowledges support from the NSF Grant #2108402. This work has been possible thanks to the use of AWSU. Chile-NLHPC credits. Powered@NLHPC: This research was partially supported by the supercomputing infrastructure of the NLHPC (ECM-02). Based on observations obtained with the Samuel Oschin 48-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grants No. AST-1440341 and AST-2034437 and a collaboration including current partners Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, IN2P3, University of Warwick, Ruhr University Bochum, Northwestern University and former partners the University of Washington, Los Alamos National Laboratories, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. We acknowledge the use of public data from the Swift data archive (Obs IDs 00014350003, 00014350004, 00014350005, 00014350007). The scientific results reported in this article are based in part on observations made by the Chandra X-ray Observatory, observation ID: 29355. Based on observations collected at the European Southern Observatory under ESO programme 109.24F5.001. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Minist.rio da Ci.ncia, Tecnologia e Inova..es (MCTI/LNA) do Brasil, the US National Science Foundation’s NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU), through CNTAC proposal CN2021A-17. Some of he data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is funded by the National Aeronautics and Space Administration and operated by the California Institute of Technology. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.

Files

aa47957-23.pdf

Files (13.3 MB)

Name	Size	Download all
aa47957-23.pdf md5:6d76470a48239ac23af1d6fc0323ceea	13.3 MB	Preview Download

	All versions	This version
Views	0	0
Downloads	0	0
Data volume	0 Bytes	0 Bytes

SDSS1335+0728: The awakening of a ~10⁶ M⊙ black hole

Abstract

Copyright and License

Acknowledgement

Files

Additional details