A Search for Extragalactic Fast Blue Optical Transients in ZTF and the Rate of AT2018cow-like Transients

Ho, Anna Y. Q.; Perley, D. A.; Gal‐Yam, A.; Lunnan, R.; Sollerman, J.; Schulze, S.; Das, Kaustav K.; Dobie, Dougal; Yao, Yuhan; Fremling, C.; Adams, S. M.; Anand, S.; Andreoni, Igor; Bellm, Eric C.; Bruch, R.; Burdge, Kevin B.; Castro-Tirado, A. J.; Dahiwale, A.; De, Kishalay; Dekany, Richard; Drake, A. J.; Duev, Dmitry A.; Graham, M. J.; Hélou, G.; Kaplan, David L.; Karambelkar, Viraj; Kasliwal, M. M.; Kool, Erik C.; Kulkarni, S. R.; Mahabal, A.; Medford, Michael S.; Miller, A. A.; Nordin, J.; Ofek, E. O.; Petitpas, G.; Riddle, Reed; Sharma, Y.; Smith, Roger M.; Stewart, A.; Taggart, K.; Tartaglia, L.; Tzanidakis, Anastasios; Winters, J. M.

doi:10.3847/1538-4357/acc533

Cited by 34 publications

(35 citation statements)

References 166 publications

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“…These timescales are well within the distributions measured for RETs discovered in the DES (Pursiainen et al 2018). Although the measured t 1/2 for AT 2022aedm is longer than the t 1/2 < 12 days defining RETS in PS1 (Drout et al 2014) and ZTF (Ho et al 2023), this is attributable to using different photometric filters; we measured t 1/2 in o, where the rate of fading in AT 2022aedm is ≈55% slower than in the g band. Correcting by this factor gives an estimated g-band t 1/2 of ≈12 days.…”

Section: Light Curvesupporting

confidence: 82%

“…Two unclassified fast transients show a comparable color evolution in combination with a peak absolute magnitude brighter than −20 mag. One is AT 2020bot, the only RET in the ZTF sample that did not fit into any of the strippedenvelope, interacting, or Cow-like subpopulations (Ho et al 2023). It is fainter than AT 2022aedm, with a faster rise and redder average color.…”

Section: Light Curvementioning

confidence: 95%

“…It outshines all but one event (DES 16E1bir) in the combined PS1+DES+ZTF sample. The closest spectroscopically classified RETs in terms of luminosity are the Cow-like RETs, typically reaching ≈−21 mag (Ho et al 2023). To highlight the exceptional luminosity of AT 2022aedm, we show a combined g-and c-band rest-frame light curve in Figure 2 Figure 2 also shows the g − r (or B − V ) color evolution of AT 2022aedm compared to the same sample of objects (where multiple bands are available).…”

Section: Light Curvementioning

confidence: 96%

“…Improvements in survey cadence allow us to probe populations of transients that rise and fade on timescales of days, compared to the weeks-months of typical supernovae (SNe). The majority of fast transients seem to arise from stripped massive stars (Ho et al 2023). These include the initial cooling peaks of Type IIb SNe, as well as events strongly interacting with a dense circumstellar medium (CSM) deficient in hydrogen (SNe Ibn; Pastorello et al 2007;Hosseinzadeh et al 2017) and sometimes helium (SNe Icn; Fraser et al 2021;Gal-Yam et al 2022;Perley et al 2022).…”

Section: Introductionmentioning

confidence: 99%

“…A more mysterious population of fast transients has also been uncovered, with blue colors and a wide range of peak luminosities up to M < −20 mag, approaching superluminous SNe (SLSNe; Quimby et al 2011;Gal-Yam 2019). Since their identification in Pan-STARRS1 (PS1) by Drout et al (2014), such objects have been discovered in data from the Palomar Transient Factory and the Supernova Legacy Survey (Arcavi et al 2016), the Dark Energy Survey (DES; Pursiainen et al 2018), ATLAS (Prentice et al 2018), Kepler (Rest et al 2018), Hyper Suprime Cam (HSC; Tampo et al 2020;Jiang et al 2022) and ZTF (Ho et al 2023). They have been termed fast blue optical transients or rapidly evolving transients (RETs).…”

Section: Introductionmentioning

confidence: 99%

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AT 2022aedm and a New Class of Luminous, Fast-cooling Transients in Elliptical Galaxies

Nicholl,

Srivastav,

Fulton

et al. 2023

ApJL

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We present the discovery and extensive follow-up of a remarkable fast-evolving optical transient, AT 2022aedm, detected by the Asteroid Terrestrial impact Last Alert Survey (ATLAS). In the ATLAS o band, AT 2022aedm exhibited a rise time of 9 ± 1 days, reaching a luminous peak with M g ≈ −22 mag. It faded by 2 mag in the g band during the next 15 days. These timescales are consistent with other rapidly evolving transients, though the luminosity is extreme. Most surprisingly, the host galaxy is a massive elliptical with negligible current star formation. Radio and X-ray observations rule out a relativistic AT 2018cow–like explosion. A spectrum in the first few days after explosion showed short-lived He ii emission resembling young core-collapse supernovae, but obvious broad supernova features never developed; later spectra showed only a fast-cooling continuum and narrow, blueshifted absorption lines, possibly arising in a wind with v ≈ 2700 km s−1. We identify two further transients in the literature (Dougie in particular, as well as AT 2020bot) that share similarities in their luminosities, timescales, color evolution, and largely featureless spectra and propose that these may constitute a new class of transients: luminous fast coolers. All three events occurred in passive galaxies at offsets of ∼4–10 kpc from the nucleus, posing a challenge for progenitor models involving massive stars or black holes. The light curves and spectra appear to be consistent with shock breakout emission, though this mechanism is usually associated with core-collapse supernovae. The encounter of a star with a stellar-mass black hole may provide a promising alternative explanation.

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Section: Light Curvesupporting

confidence: 82%

Section: Light Curvementioning

confidence: 95%

Section: Light Curvementioning

confidence: 96%