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 10081 spectroscopically-confirmed transients (9949 supernovae and 132 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 6196 4124 2107 1127 558 All SNe 6126 4068 2069 1102 541 Ia 4623 3087 1552 826 413 Ia-CSM 9 8 4 3 3 Iax 12 8 5 5 3 Ib/c 342 225 121 57 26 Ibn 27 19 14 5 1 Ic-BL 56 42 20 10 5 SLSN-I 48 26 14 11 3 II 1113 730 382 208 99 IIb 91 56 31 17 8 IIn 152 105 56 29 14 SLSN-II 24 12 6 2 1 TDE 30 20 12 7 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 10081 6946 3694 2002 1014 All SNe 9949 6841 3624 1959 989 Ia 7283 5042 2654 1437 743 Ia-CSM 20 15 8 5 5 Iax 22 18 13 9 6 Ib/c 523 370 214 104 46 Ibn 35 26 18 8 3 Ic-BL 77 61 33 16 7 SLSN-I 80 46 24 16 5 II 2063 1383 732 402 195 IIb 138 88 54 29 15 IIn 263 181 97 50 21 SLSN-II 46 26 9 3 2 TDE 62 44 25 13 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 49 43 35 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