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 9586 spectroscopically-confirmed transients (9459 supernovae and 127 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 5872 3899 1998 1072 535 All SNe 5805 3846 1962 1048 518 Ia 4375 2909 1471 782 392 Ia-CSM 8 7 4 3 3 Iax 12 8 5 5 3 Ib/c 325 215 115 55 26 Ibn 26 18 13 5 1 Ic-BL 53 40 20 10 5 SLSN-I 47 25 13 10 2 II 1058 697 363 201 98 IIb 89 56 31 17 8 IIn 148 103 54 28 14 SLSN-II 22 11 6 2 1 TDE 27 17 10 6 6 Gap 9 8 5 4 2 Ca-rich 1 0 0 0 0 LRN 3 3 1 1 0 ILRT 2 2 2 2 1 LBV 3 3 2 1 1 Novae 29 26 20 13 8 Other 2 2 1 1 1

All events: mag ≤ 19.0 18.5 18.0 17.5 17.0 All typed 9586 6588 3512 1909 975 All SNe 9459 6488 3445 1867 950 Ia 6930 4782 2533 1373 714 Ia-CSM 19 14 8 5 5 Iax 21 17 12 9 6 Ib/c 493 347 198 96 45 Ibn 34 25 17 8 3 Ic-BL 72 57 31 14 7 SLSN-I 79 45 24 15 4 II 1957 1314 690 383 187 IIb 132 85 52 29 15 IIn 253 176 93 50 21 SLSN-II 44 25 9 3 2 TDE 58 40 23 12 8 Gap 19 16 9 5 3 Ca-rich 5 3 0 0 0 LRN 4 4 2 1 0 ILRT 4 3 3 2 1 LBV 6 6 4 2 2 Novae 48 42 34 24 13 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