The Photometric and Spectroscopic Evolution of Rapidly Evolving Extragalactic Transients in ZTF

Abstract

We present 42 rapidly evolving (time spent above half-maximum brightness t 1/2 12 d) extragalactic transients from Phase I of the Zwicky Transient Facility (ZTF), of which 22 have spectroscopic classifications. This is one of the largest systematically selected samples of day-timescale transients todate, and the first with spectroscopic classifications. Most can be classified as core-collapse supernovae (SNe), and we identify several predominant subtypes: (1) subluminous Type IIb or Type Ib SNe; (2) luminous Type Ibn or hybrid IIn/Ibn SNe; and (3) radio-loud, short-duration luminous events similar

A common envelope jets supernova (CEJSN) impostor scenario for fast blue optical transients

“…4.10. The rate of AT2018cow-like FBOTs Ho et al (2022) estimate the rate of AT2018cow-like events to be 0.01 − 0.1% of the rate of CCSNe (see also Ho et al 2021). In Soker, Grichener, & Gilkis (2019) we estimate the rate of all polar-CEJSN and impostor events to be 0.2 − 0.5% of all CCSNe.…”

Cosmological Fast Optical Transients with the Zwicky Transient Facility: A Search for Dirty Fireballs

“…The afterglows in Table 1 constitute the shortest-lived optical extragalactic transients that have been discovered in optical survey data and followed up in real time. To illustrate this, Figure 1 shows the duration above half-maximum and the peak absolute magnitude for optical transients, primarily with light curves observed by ZTF (Fremling et al 2020;Ho et al 2021c). Most supernovae (SNe) evolve on timescales from 10-100 d, powered by radioactive decay, with their characteristic duration set by diffusion through optically thick ejecta (Villar et al 2017a).…”

“…Due to the cadence of ZTF, our measurements typically represent upper limits on the duration and lower limits on the peak luminosity. Measurements are in rest-frame g-band when possible, with a crude k-correction applied (Equation 1 for afterglows; see Ho et al (2021c) for other sources). There were five detections the first night, all in r-band, which showed significant fading of 0.35 mag over 0.48 hr; we provide the full set of ZTF photometry in Table 5, and plot the r-band light curve in Figure 2.…”

“…Measurements of superluminous supernovae (SLSNe), Type Ia supernovae (SN Ia), and most core-collapse supernovae (SNe) are from the ZTF Bright Transient Survey(Fremling et al 2020;. Measurements of short-duration core-collapse SNe and AT 2018cow-like transients are from dedicated searches for fast-evolving transients(Prentice et al 2018;Perley et al 2019bPerley et al , 2021cHo et al 2020cHo et al , 2021cYao et al 2021e). For reference we also show the timescale and luminosity of the optical emission from GW170817/AT 2017gfo(Coulter et al 2017;Cowperthwaite et al 2017;Kasliwal et al 2017;Drout et al 2017;Villar et al 2017b) and of iPTF14yb (the only optically discovered afterglow prior to ZTF with a redshift measurement;Cenko et al 2015).…”

“…Due to the cadence of ZTF, our measurements typically represent upper limits on the duration and lower limits on the peak luminosity. Measurements are in rest-frame g-band when possible, with a crude k-correction applied (Equation 1 for afterglows; seeHo et al (2021c) for other sources).…”