{ "abstract": "We present the first X-ray detection of the supernova (SN) impostor AT 2016blu in NGC 4559. AT 2016blu exhibited 27 detected quasiperiodic (∼113 day) outbursts between 2012 and 2026 June, presumably triggered by periastron passages in an eccentric binary system in which the primary is a ≳33 M ⊙ luminous blue variable (LBV). AT 2016blu was serendipitously observed by Chandra in 2001–2002, prior to its first documented outburst in 2012, but the stacked archival data show no X-ray detection. We monitored the source’s visual-wavelength variability around its predicted outburst time and triggered a Chandra Target of Opportunity (ToO) program in 2026 March, obtaining observations with detections over five closely spaced epochs. These data indicate an X-ray luminosity of log L X ≈ 38.64 ± 0.11 erg s ⁻¹ and an accretion rate of M ̇ ≳ 8 × 1 0 − 8 M ⊙ yr − 1 , consistent with the presence of a compact companion. We therefore conclude that AT 2016blu is the first known case of an LBV SN impostor where X-ray observations clearly favor intermittent accretion onto a compact object as the cause of the outbursts. Given that the system consists of a massive star and a compact companion, AT 2016blu is a high-mass X-ray binary (HMXB), similar to SN 2010da, although the donor star in SN 2010da is a red supergiant (RSG).", "abstract_shown": true, "affiliations": [ "University of Virginia", "University of Arizona", "South African Astronomical Observatory", "University of Cape Town", "NITheCS National Institute for Theoretical and Computational Sciences", "University of California", "Las Cumbres Observatory", "HUN-REN Research Center for Astronomy and Earth Sciences", "MTA Center of Excellence", "Observatorio Tros-Alt", "Polaris Observatory", "Vereniging Voor Sterrenkunde (VVS)", "Supra Solem Observatory", "Groupe Européen d’Observations Stellaires (GEOS)", "Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne (BAV)", "American Association of Variable Star Observers", "East Tennessee State University", "King University", "Montarrenti Observatory", "UAI", "Amateur observatory “Adonis” Poelkapellestraat 57", "MarSEC", "College View Observatory", "University of Florence", "Strada Provinciale 101 Castellina in Chianti", "Southwater Observatory", "Institute for Advanced Physical Studies", "Sofia University" ], "article_type": null, "arxiv": null, "author_total": 36, "authors": [ { "affs": [ 0 ], "name": "Mojgan Aghakhanloo", "orcid": "0000-0001-8341-3940" }, { "affs": [ 0 ], "name": "Núria Torres-Albà", "orcid": "0000-0003-3638-8943" }, { "affs": [ 1 ], "name": "Nathan Smith", "orcid": "0000-0001-5510-2424" }, { "affs": [ 0 ], "name": "Raphael Baer-Way", "orcid": "0009-0004-7268-7283" }, { "affs": [ 0, 2, 3, 4 ], "name": "Shazrene Mohamed", "orcid": "0000-0002-1856-9225" }, { "affs": [ 5 ], "name": "Alexei V. Filippenko", "orcid": "0000-0003-3460-0103" }, { "affs": [ 5 ], "name": "WeiKang Zheng", "orcid": "0000-0002-2636-6508" }, { "affs": [ 5 ], "name": "Thomas G. Brink", "orcid": "0000-0001-5955-2502" }, { "affs": [ 6, 5 ], "name": "D. Andrew Howell", "orcid": "0000-0003-4253-656X" }, { "affs": [ 1 ], "name": "Brian Hsu", "orcid": "0000-0002-9454-1742" }, { "affs": [ 6, 5 ], "name": "Moira Andrews", "orcid": "0000-0002-1895-6639" }, { "affs": [ 6, 5 ], "name": "Joseph R. Farah", "orcid": "0000-0003-4914-5625" }, { "affs": [ 6 ], "name": "Curtis McCully", "orcid": "0000-0001-5807-7893" }, { "affs": [ 6, 5 ], "name": "Kathryn Wynn" }, { "affs": [ 7, 8 ], "name": "Réka Könyves-Tóth", "orcid": "0000-0002-8770-6764" }, { "affs": [ 1 ], "name": "Conor L. Ransome", "orcid": "0000-0003-4175-4960" }, { "affs": [ 9 ], "name": "Enrique Rathmann" }, { "affs": [ 10 ], "name": "Tamás Tordai" }, { "affs": [ 11 ], "name": "Sjoerd Dufoer" }, { "affs": [ 12 ], "name": "Charles Cynamon" }, { "affs": [ 11, 13, 14 ], "name": "Franz-Josef Hambsch", "orcid": "0000-0003-0125-8700" }, { "affs": [ 15, 16, 17 ], "name": "Thomas Rutherford", "orcid": "0009-0002-4296-2200" }, { "affs": [ 15, 18, 19 ], "name": "Simone Leonini", "orcid": "0009-0005-0424-1842" }, { "affs": [ 11, 20 ], "name": "Franky Dubois" }, { "affs": [ 15, 19, 21 ], "name": "Ivo Peretto", "orcid": "0000-0003-3833-2695" }, { "affs": [ 22 ], "name": "Donald F. Collins" }, { "affs": [ 23, 24 ], "name": "Lorenzo Betti", "orcid": "0009-0008-2210-8924" }, { "affs": [ 23, 24 ], "name": "Lara Fossi", "orcid": "0009-0002-7967-6830" }, { "affs": [ 23, 24 ], "name": "Irene Parenti", "orcid": "0009-0005-4783-0049" }, { "affs": [ 23, 24 ], "name": "Vincenzo Pettina" }, { "affs": [ 23, 24 ], "name": "Giulio Giordano Chiti" }, { "affs": [ 23, 24 ], "name": "Maria Hofheinz" }, { "affs": [ 25 ], "name": "André Steenkamp" }, { "affs": [ 15 ], "name": "Sauro Gaudenzi" }, { "affs": [ 26, 27 ], "name": "Nikola Antonov", "orcid": "0009-0002-1484-7029" }, { "affs": [ 15 ], "name": "Giuseppe Pappa" } ], "bibtex": "https://research.draconitic.com/paper/ac8v09bm933da.bib", "cited_by": 0, "doi": "10.3847/1538-4357/ae9a86", "fulltext_url": null, "id": "ac8v09bm933da", "issns": [ "1538-4357", "0004-637X" ], "landing_url": "https://iopscience.iop.org/article/10.3847/1538-4357/ae9a86", "language": null, "licence": "CC-BY-4.0", "licence_label": "CC BY 4.0", "licence_source": "article", "licence_url": "https://creativecommons.org/licenses/by/4.0/", "metadata_licence": null, "native_subjects": [ [ "feed-journal", "astronomy/general" ] ], "openalex": null, "pdf_url": "https://iopscience.iop.org/article/10.3847/1538-4357/ae9a86/pdf", "pmcid": null, "pmid": null, "published": "2026-11-09", "publisher": "American Astronomical Society", "ris": "https://research.draconitic.com/paper/ac8v09bm933da.ris", "sources": [ { "first_seen": "2026-11-09T12:20:28Z", "native_id": "10.3847/1538-4357/ae9a86", "source": "feed-iop", "url": "https://iopscience.iop.org/article/10.3847/1538-4357/ae9a86" }, { "first_seen": "2026-11-09T12:21:31Z", "native_id": "10.3847/1538-4357/ae9a86", "source": "crossref", "url": "https://iopscience.iop.org/article/10.3847/1538-4357/ae9a86" } ], "subjects": [ { "field": "astronomy", "origin": "journal-openalex:3103|Stellar, planetary, and galactic studies", "subfield": "stellar" } ], "title": "AT 2016blu: Accretion-powered Outbursts in a Luminous Blue Variable and Compact Object Binary", "title_text": "AT 2016blu: Accretion-powered Outbursts in a Luminous Blue Variable and Compact Object Binary", "type": "peer-reviewed", "updated_at": "2026-11-09T12:21:31Z", "url": "https://research.draconitic.com/paper/ac8v09bm933da", "venue": "The Astrophysical Journal", "versions": [] }