AT 2024wpp: An Extremely Luminous Fast Ultraviolet Transient Powered by Accretion onto a Black Hole

Perley, DA ORCID: 0000-0001-8472-1996, Ho, AYQ, McGrath, Z, Camilo, M, Sevilla, C, Chen, P, Schroeder, G, Govreen-Segal, T, Bochenek, A ORCID: 0009-0008-2714-2507, Qin, Y-J, Gillanders, JH, Amend, B, Anderson, JP, Andreoni, I, Aryan, A, Bellm, EC, Bloom, JS, de Boer, T, Carney, J, Caiazzo, I et al (2026) AT 2024wpp: An Extremely Luminous Fast Ultraviolet Transient Powered by Accretion onto a Black Hole. Monthly Notices of the Royal Astronomical Society. ISSN 0035-8711 (Accepted)

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Abstract

We present the discovery of AT 2024wpp (“Whippet”), a fast and luminous 18cow-like transient. At a redshift of ʐ = 0.0868, revealed by Keck Cosmic Web Imager spectroscopy of its faint star-forming host, it is the fourth-nearest example of its class to date. Rapid identification of the source in the Zwicky Transient Facility data stream permitted ultraviolet-through-optical observations to be obtained prior to peak, allowing the first determination of the peak bolometric luminosity (2 × 1045 erg s−1), maximum photospheric radius (1015 cm), and total radiated energy (1051 erg) of an 18cow-like object. We present results from a comprehensive multiwavelength observing campaign, including a far-UV spectrum from the Cosmic Origins Spectrograph on the Hubble Space Telescope and deep imaging extending >100 days post-explosion from the Very Large Telescope, Hubble Space Telescope, Very Large Array, and Atacama Large Millimetre Array. We interpret the observations under a model in which a rapidly-accreting central engine blows a fast (∼0.2 ϲ) wind into the surrounding medium and irradiates it with X-rays. The high Doppler velocities and intense ionization within this wind prevent identifiable spectroscopic features from appearing in the ejecta or in the surrounding circumstellar material. Weak H and He signatures do emerge in the spectra after 35 days in the form of double-peaked narrow lines. Each peak is individually narrow (full width ɖ ⩗∼ 3000 km s−1) but the two components are separated by Δ⩗ ∼ 6600 km s−1 , indicating stable structures of denser material, possibly representing streams of tidal ejecta or an ablated companion star.

Item Type:	Article
Uncontrolled Keywords:	5109 Space Sciences; 5101 Astronomical Sciences; 51 Physical Sciences; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press (OUP)
Date of acceptance:	7 April 2026
Date of first compliant Open Access:	23 April 2026
Date Deposited:	23 Apr 2026 13:36
Last Modified:	23 Apr 2026 13:36
DOI or ID number:	10.1093/mnras/stag678
URI:	https://researchonline.ljmu.ac.uk/id/eprint/28440

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