Paper

AT2024wpp: An Extremely Luminous Fast Ultraviolet Transient Powered by Accretion onto a Black Hole

Bellm, Eric C, Magnier, Eugene, Dimitriadis, Georgios, Mahabal, Ashish A, Ryan Hinds, K, Singh, Avinash, de Boer, Thomas, Inserra, Cosimo, Chien-Cheng, Lin, Lowe, Thomas B, Perley, Daniel A, Gromadzki, Mariusz, Amar Aryan, Galbany, Lluís, Coughlin, Michael, Anderson, Joseph P, Pessi, Priscila J, Coughlin, Eric R, Graham, Matthew J, Pignata, Giuliano, Yu-Jing, Qin, Ting-Wan, Chen, Schroeder, Genevieve, Liu, Chang, Bochenek, Aleksandra, Kaiser, Benjamin C, Wainscoat, Richard, Young, David R, Schulze, Steve, Sevilla, Cassie, Purdum, Josiah, Carney, Jonathan, Chen, Ping, Kasliwal, Mansi M, Gal-Yam, Avishay, Stein, Robert D, Gillanders, James H, Amend, Benjamin, Koivisto, Niilo E, Andreoni, Igor, Caiazzo, Ilaria, Srivastav, Shubham, Groom, Steven L, Tweddle, Jack W, Ho, Anna Y Q, Fremling, Christoffer, Sollerman, Jesper, Bloom, Joshua S, Chen, Tracy X, Mo, Geoffrey, Nicholl, Matt, Wise, Jacob L, Govreen-Segal, Taya, Gangopadhyay, Anjashay, Minguez, Paloma, Smartt, Stephen J, Dennefeld, Michel, Gutiérrez, Claudia P, Ghendrih, Melzie, McGrath, Zoë, Charalampopoulos, Panos, Srinivasaragavan, Gokul, Sahu, Anwesha, Lin

2026

Overview

We present the discovery of AT 2024wpp (\"Whippet\"), a fast and luminous 18cow-like transient. At a redshift of z=0.0868, revealed by Keck Cosmic Web Imager spectroscopy of its faint and diffuse 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 (2x10^45 erg/s), maximum photospheric radius (10^15 cm), and total radiated energy (10^51 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 powerful rapidly-accreting central engine blows a fast (~0.15c) wind into the surrounding medium and irradiates it with X-rays. The high Doppler velocities and intense ionization within this wind prevent any identifiable features from appearing in the ejecta or in the surrounding circumstellar material, even in the far-ultraviolet. 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 ~3000 km/s) but the two components are separated by ~6600 km/s, indicating stable structures of denser material, possibly representing streams of tidal ejecta or an ablated companion star.

• Publisher: Cornell University Library, arXiv.org
• Subject: Arrays / Black holes / Companion stars / Data transmission / Ejecta / Hubble Space Telescope / Luminosity / Photosphere / Red shift / Space telescopes / Spectrum analysis / Star formation / Transients (astronomy) / Ultraviolet astronomy / Ultraviolet spectra / Very Large Telescope