AT 2016blu: Accretion-powered Outbursts in a Luminous Blue Variable and Compact Object Binary

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).

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Publication Details

Journal
The Astrophysical Journal
Published
2026-11-09
DOI
https://doi.org/10.3847/1538-4357/ae9a86
Citations
1
Primary Topic
Astrophysical Phenomena and Observations
Type
article
Field-Weighted Citation Impact
0.75

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article

AT 2016blu: Accretion-powered Outbursts in a Luminous Blue Variable and Compact Object Binary

C. L. Ransome, Moira Andrews, Donald F. Collins, Nathan Smith et al.
1 citations
The Astrophysical Journal
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AT 2016blu: Accretion-powered Outbursts in a Luminous Blue Variable and Compact Object Binary

C. L. Ransome, Moira Andrews, Donald F. Collins, Nathan Smith, Giuseppe Pappa, Mojgan Aghakhanloo, Lorenzo Betti, Irene Parenti, Sjoerd Dufoer, A. V. Filippenko, Charles H. Cynamon, Franz-Josef Hambsch, Réka Könyves-Tóth, Thomas Rutherford, Franky Dubois, Joseph Farah, Tamás Tordai, Sauro Gaudenzi, C. McCully, Simone Leonini, Brian Hsu, Ivo Peretto, Núria Torres-Albà, Lara Fossi, Raphael Baer-Way, André Steenkamp, Kathryn Wynn, Thomas G. Brink, WeiKang Zheng, D. Andrew Howell, Nikola Antonov, Shazrene Mohamed, Enrique Rathmann, Giulio Giordano Chiti, Maria Hofheinz, Vincenzo Pettina
article en
1 citations

Abstract

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).

The Astrophysical JournalVol. 1011(2)
King University (US), East Tennessee State University (US), Las Cumbres Observatory Global Telescope Network (US), University of Arizona (US), University of Cape Town (ZA), American Association of Variable Star Observers (US), Adolfo Ibáñez University (CL), University of California System (US), Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne (DE), Materials Research Science and Engineering Centers (US), HUN-REN Research Centre for Astronomy and Earth Sciences (HU), South African Astronomical Observatory (ZA), University of Florence (IT), University of Virginia (US), Sofia University "St. Kliment Ohridski" (BG)
National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, University of Virginia, Space Telescope Science Institute, Queen's University Belfast, Queen's University, Centers for Disease Control and Prevention, College and Graduate School of Arts and Sciences, University of California Observatories
Openalex Percentile: Top 27%
Astrophysical Phenomena and Observations
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