The ZTF Bright Transient Survey

The Zwicky Transient Facility (ZTF) Bright Transient Survey is by far the largest spectroscopic supernova survey ever conducted. Since June of 2018 we have been surveying the entire nighttime Northern sky every 2-3 nights in two filters and acquiring spectra of (almost) every time-varying, nonmoving object brighter than 18.5 mag that is not a Galactic source or an AGN, providing a complete and unbiased view of the dynamic optical sky. Transients down to 19.0 mag are also targeted when possible (given available spectroscopic resources). Between 2017 and 2020 we catalogued almost 4000 supernovae. Between 2021 and 2024 we expect to increase this total to almost 10000, including hundreds of "exotic" transients: tidal disruption events, superluminous supernovae, and the like. So far we have detected 8200 spectroscopically-confirmed transients (8092 supernovae and 108 transients of other types). The large majority of these classifications were provided by our programs. Alert data (including preliminary photometry) is released in real time via ZTF Alert Brokers (1,2,3,4) and spectra and classifications are announced nightly via TNS. Cumulative properties of the sample are compiled here and in our papers. Some properties of the current sample can be explored in detail using the BTS Sample Explorer.

Sample Summary

The statistics below (by class and limiting peak magnitude) are updated daily: numbers in each cell provide the total of publicly-available TNS classifications of each type. Classifications come mostly from our own programs, but also use reports from other groups via TNS. Not all classifications are final and statistics do not include transients with non-public classifications. The table on the right includes every ZTF Northern Sky Survey transient above 19.0 magnitude; the table on the left is specific to events passing a variety of cuts to establish a high-quality statistical sample: see below for details. Plots show a skymap of all confirmed extragalactic transients, and a preliminary luminosity-duration plot for sample transients.

SN-like events passing sample cuts: mag ≤ 19.0 18.5 18.0 17.5 17.0 All typed 5037 3327 1702 921 460 All SNe 4982 3282 1673 902 447 Ia 3783 2495 1261 684 341 Ia-CSM 5 5 3 2 2 Iax 8 5 2 2 2 Ib/c 275 181 91 45 24 Ibn 21 15 10 4 1 Ic-BL 48 37 18 9 6 SLSN-I 39 18 8 7 1 II 885 588 313 166 81 IIb 71 44 24 13 7 IIn 127 90 48 25 12 SLSN-II 20 11 6 2 1 TDE 20 14 7 4 4 Gap 7 6 4 3 2 Ca-rich 1 0 0 0 0 LRN 1 1 0 0 0 ILRT 2 2 2 2 1 LBV 3 3 2 1 1 Novae 26 23 17 11 6 Other 2 2 1 1 1

All events: mag ≤ 19.0 18.5 18.0 17.5 17.0 All typed 8200 5578 2961 1620 821 All SNe 8092 5492 2904 1584 801 Ia 5969 4068 2135 1168 603 Ia-CSM 16 12 7 4 4 Iax 14 11 7 5 4 Ib/c 412 289 160 81 40 Ibn 26 20 12 6 2 Ic-BL 62 49 27 14 8 SLSN-I 62 30 15 11 2 II 1649 1105 594 324 156 IIb 107 68 42 24 13 IIn 220 152 83 44 18 SLSN-II 37 22 8 2 1 TDE 47 34 18 9 5 Gap 15 12 8 4 3 Ca-rich 3 1 0 0 0 LRN 2 2 1 0 0 ILRT 4 3 3 2 1 LBV 6 6 4 2 2 Novae 44 38 30 22 11 Other 2 2 1 1 1

Latest Transients

The following list shows the most recent candidates saved to the program. No light curve or host-galaxy filtering has been applied, so this may include some false positives such as cataclysmic variables or AGNs.

Supernova Candidates Needing Classification

The following list shows older SN candidates still needing classification, and may be useful to observers with classification programs in need of targets (the most recent ZTF magnitude is provided below). A looser version of the sample cuts has been applied to this list to remove some false positives and poorly-observed SNe. Because the whole light curve is not available yet there may still be a few false positives in this list.

Completeness

Our goal is to be close to 100% spectroscopically complete for all genuine extragalactic transients brighter than 18.5 magnitude that are detected in more than one imaging epoch in the survey footprint, for which the epoch of maximum light is clearly observed, and which do not set within about a month after maximum light. (Transients that do not meet these cuts are also observed when possible.) Our actual completeness for events meeting all these criteria is about 95%. (The remaining 5% are mostly concentrated in periods of bad weather that affected our spectroscopic follow-up programs.)

The table at left below presents classification success statistics (by limiting magnitude) for events meeting these criteria (at left) and exhibiting "SN-like behavior" (slow rise and/or fade time, or coincident with a galaxy). The month and peak magnitude are as observed (in either filter). These totals do include unreleased classifications, so they are slightly higher than the totals given in the type-specific table above. The table at right includes all events, including those with poor visibility which could not be classified (many of these are stars).

A visualization of this is also given in the figure at right: large points indicate classification successes (green circle) or failures (red X) for sample transients; small dots show other potential transients that fail our cuts.

BTS Papers

• Paper I: Spectroscopic Classification and the Redshift Completeness of Local Galaxy Catalogs (Fremling et al. 2020, ApJ 895:32)
• Paper II: A Public Statistical Sample for Exploring Supernova Demographics (Perley et al. 2020, ApJ 904:35 )

Team Members and Current Contributors