The ZTF Bright Transient Survey


Sample SummaryLatest TransientsUnclassified SN CandidatesCompleteness StatisticsPapersTeamSample Explorer


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 4032 spectroscopically-confirmed transients (3980 supernovae and 52 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 ≤19.018.518.017.517.0
All typed24731610849443228
All SNe24421584832434222
Ia18211184611330171
Ia-CSM22111
Iax64222
Ib/c14493522313
Ibn108631
Ic-BL26191253
SLSN-I1912541
II4582951647737
IIb33201375
IIn593922105
SLSN-II139410
TDE107522
Gap54321
Ca-rich10000
LRN11000
ILRT22221
LBV11100
Novae1413842
Other22111
All events:
mag ≤19.018.518.017.517.0
All typed403227191444769403
All SNe398026751417758396
Ia288419541026558299
Ia-CSM53211
Iax86322
Ib/c218147874221
Ibn1210741
Ic-BL32241474
SLSN-I3319962
II84555529515274
IIb513123127
IIn11077392011
SLSN-II2516620
TDE2117922
Gap129631
Ca-rich31000
LRN22100
ILRT43321
LBV33210
Novae17161153
Other22111
Note: the classes above are not all independent (e.g. the total for Ib/c includes Ibn and Ic-BL; the total for II includes IIb, IIn, and SLSN-II) so the sum of the individual SN counts is greater than the "All SNe" count. BTS classifications are based on low-resolution 2m-class spectra and while basic type classifications are reliable, we are not complete in assigning subtypes (II vs. IIb, Ib vs. Ic, etc.). The table on the left is restricted to events with P48 coverage before and after peak, good visibility, and "SN-like" behavior (a light curve slower than typical CV's or a host association, and faster evolution than AGNs). See completeness for classification completeness statistics. Magnitudes are at the observed peak (in either filter) - for poorly sampled light curves this may underestimate the flux of the true peak.

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.

IDTNSIDsavedRAdecΔtlastmlasttypez
ZTF21aadsoerNone2021-01-19352.09521242425.49923052589.40g = 18.97--
ZTF21aadebssNone2021-01-1997.507009560630.25005783819.29r = 18.96--
ZTF21aadudgyNone2021-01-1979.87795667394.985278021079.28r = 19.05--
ZTF21aaecjfcNone2021-01-19117.36839911550.7994367629.24r = 18.97--
ZTF21aaffrxdNone2021-01-19100.09008174338.40662032079.20g = 18.98--
ZTF21aaehinnNone2021-01-20156.92914741415.46351279788.09g = 18.79--
ZTF21aafkktuNone2021-01-20174.99584743614.52798262618.08g = 18.40SN II0.031

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.

IDTNSIDsavedRAdecΔtlastmlast
ZTF20achpcvtAT2020vwl2020-10-14232.65754410626.98245140419.99g = 18.06
ZTF20acmgsfoAT2020xsy2020-11-23163.766680802-1.5398965017610.05r = 18.91
ZTF20acrjjseAT2020aaru2020-11-23168.320175786-6.1524071428810.05r = 19.12
ZTF20acsebtwAT2020aazc2020-11-26128.52392095322.45511474439.24r = 20.20
ZTF20actogylAT2020aavt2020-12-01213.49097757931.55575073111.00r = 19.67
ZTF20acwytxnAT2020acka2020-12-12238.75811090816.30452547589.98g = 18.29
ZTF20acwqlpqAT2020acez2020-12-15215.038413458.944805987111.05r = 19.68
ZTF20acxkfohNone2020-12-16164.319596126-23.404248745512.09r = 19.46
ZTF19aabyxheNone2020-12-23192.982995766-12.410576289311.09g = 19.11
ZTF20acziblzNone2020-12-28341.2211464115.8612424924213.42r = 16.69
ZTF21aaabzapNone2021-01-05218.9534124875.8210596048910.98g = 19.19
ZTF20acywbdiNone2021-01-06195.72210073273.444111478614.10g = 20.10
ZTF21aaahuoxNone2021-01-07182.90818134712.163071581711.05r = 18.92
ZTF21aaabzdrNone2021-01-07230.13601421111.989685887610.97g = 19.74
ZTF21aaaouydNone2021-01-07218.83249571212.472334662110.98g = 19.34
ZTF21aaaiaklNone2021-01-07180.737237881-20.934139776410.99g = 18.75
ZTF20aczhaeuNone2021-01-07237.93204032427.79533155589.98g = 18.59
ZTF20adafawdNone2021-01-08127.611139204-11.251858478710.17g = 19.20
ZTF21aaawwdtNone2021-01-08144.507695798-20.362973755212.17g = 19.96
ZTF21aaavghgNone2021-01-08155.61372975527.503794872910.10g = 18.76
ZTF21aaagypxNone2021-01-08168.2830202175.072038602110.05r = 18.21
ZTF21aaaytnyNone2021-01-08240.4395100918.01929083799.98g = 18.47
ZTF21aaabxbdNone2021-01-08252.88735967238.01102417969.99g = 18.29
ZTF21aaaziebNone2021-01-09350.6652541120.65939501139.40g = 18.67
ZTF21aaaqtwdNone2021-01-09344.08584679325.88875039659.40g = 17.17
ZTF21aaazjiaNone2021-01-09340.33696329827.023751819411.37r = 17.93
ZTF21aaadhjnNone2021-01-0931.7478635882-13.442955569810.37r = 18.80
ZTF21aaahtlnNone2021-01-09157.61119529540.250626097211.10g = 18.50
ZTF18aajjhkqNone2021-01-09176.59426473751.118732022311.05r = 18.51
ZTF21aaabzsjNone2021-01-09225.12176766422.384805073310.01r = 19.01
ZTF21aaaosmnNone2021-01-09221.76088291956.314888696511.04r = 18.37
ZTF20acyroekNone2021-01-09239.75833046759.4038549289.03r = 19.21
ZTF20aczguyyNone2021-01-09248.7411394265.747894325910.04r = 19.36
ZTF18abwitkfNone2021-01-1015.7053465299-21.836463596713.42r = 17.93
ZTF21aabfwwlNone2021-01-10169.632004417-6.277920067610.05r = 18.46
ZTF20aazbbqoNone2021-01-10150.5293712743.0577371087810.11g = 18.40
ZTF21aacufipNone2021-01-10230.36189650136.76778899169.98g = 18.19
ZTF21aabpnlmNone2021-01-11359.02129283353.729585969810.39r = 18.44
ZTF21aadrljiNone2021-01-12195.524804288-22.70878962039.04r = 18.86
ZTF21aacxungNone2021-01-13128.54735295855.811762143210.14g = 18.01
ZTF21aadezmhNone2021-01-14124.48807477633.766058783910.14g = 18.41
ZTF21aaetrdbNone2021-01-15207.40490253711.09617255679.04r = 18.52
ZTF21aaeczqrNone2021-01-1677.7538167374-16.34506393039.29r = 18.49
ZTF21aaekkbvNone2021-01-16264.6477633942.21554709419.98g = 18.27
ZTF19absxwowNone2021-01-17359.21609615919.2516354039.38g = 18.48
ZTF21aaepqnbNone2021-01-17357.73253291712.77003372539.38g = 18.46
ZTF21aadrtqzNone2021-01-17208.703588273-13.608561655111.09g = 18.40
ZTF21aafdnjeNone2021-01-18241.50891935618.67046958899.98g = 18.38

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 93%. (The remaining 7% are mostly concentrated in periods of bad weather that affected our spectroscopic follow-up programs.)

The table 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. 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.

mag≤19.0≤18.5≤18.0≤17.5≤17.0
2018 May18/22 (81.8%)18/20 (90.0%)7/7 (100%)4/4 (100%)3/3 (100%)
2018 Jun40/42 (95.2%)22/22 (100%)12/12 (100%)7/7 (100%)6/6 (100%)
2018 Jul53/55 (96.4%)30/31 (96.8%)13/13 (100%)4/4 (100%)3/3 (100%)
2018 Aug47/48 (97.9%)26/26 (100%)14/14 (100%)6/6 (100%)2/2 (100%)
2018 Sep28/33 (84.8%)18/20 (90.0%)9/10 (90.0%)4/4 (100%)3/3 (100%)
2018 Oct1/1 (100%)0/00/00/00/0
2018 Nov46/58 (79.3%)26/29 (89.7%)16/17 (94.1%)10/10 (100%)4/4 (100%)
2018 Dec60/79 (75.9%)44/47 (93.6%)24/24 (100%)14/14 (100%)9/9 (100%)
2019 Jan51/114 (44.7%)41/67 (61.2%)31/38 (81.6%)24/25 (96.0%)16/16 (100%)
2019 Feb54/90 (60.0%)40/53 (75.5%)22/23 (95.7%)11/11 (100%)7/7 (100%)
2019 Mar58/76 (76.3%)34/36 (94.4%)23/23 (100%)17/17 (100%)11/11 (100%)
2019 Apr99/133 (74.4%)69/74 (93.2%)35/36 (97.2%)13/13 (100%)2/2 (100%)
2019 May76/106 (71.7%)55/59 (93.2%)37/38 (97.4%)17/17 (100%)8/8 (100%)
2019 Jun92/111 (82.9%)57/57 (100%)29/29 (100%)15/15 (100%)6/6 (100%)
2019 Jul98/111 (88.3%)54/54 (100%)30/30 (100%)12/12 (100%)6/6 (100%)
2019 Aug112/131 (85.5%)58/58 (100%)25/25 (100%)13/13 (100%)6/6 (100%)
2019 Sep121/142 (85.2%)80/81 (98.8%)46/47 (97.9%)22/23 (95.7%)14/14 (100%)
2019 Oct122/158 (77.2%)68/71 (95.8%)31/31 (100%)15/15 (100%)10/10 (100%)
2019 Nov112/160 (70.0%)76/84 (90.5%)40/40 (100%)16/16 (100%)7/7 (100%)
2019 Dec60/84 (71.4%)45/47 (95.7%)25/25 (100%)14/14 (100%)6/6 (100%)
2020 Jan113/153 (73.9%)79/82 (96.3%)35/37 (94.6%)15/16 (93.8%)8/8 (100%)
2020 Feb130/171 (76.0%)82/87 (94.3%)49/50 (98.0%)22/22 (100%)8/8 (100%)
2020 Mar13/14 (92.9%)12/12 (100%)6/6 (100%)2/2 (100%)1/1 (100%)
2020 Apr49/71 (69.0%)37/37 (100%)22/22 (100%)10/10 (100%)6/6 (100%)
2020 May111/155 (71.6%)75/75 (100%)42/42 (100%)22/22 (100%)12/12 (100%)
2020 Jun102/127 (80.3%)60/60 (100%)30/30 (100%)20/20 (100%)8/8 (100%)
2020 Jul76/104 (73.1%)42/44 (95.5%)26/27 (96.3%)12/12 (100%)6/6 (100%)
2020 Aug76/87 (87.4%)43/45 (95.6%)18/19 (94.7%)10/11 (90.9%)5/5 (100%)
2020 Sep97/119 (81.5%)58/59 (98.3%)28/28 (100%)18/18 (100%)9/9 (100%)
2020 Oct135/170 (79.4%)82/84 (97.6%)42/42 (100%)24/24 (100%)11/11 (100%)
2020 Nov122/161 (75.8%)81/82 (98.8%)35/35 (100%)21/21 (100%)11/11 (100%)
2020 Dec124/192 (64.6%)94/95 (98.9%)40/40 (100%)24/24 (100%)11/11 (100%)
2021 Jan42/69 (60.9%)37/40 (92.5%)27/27 (100%)17/17 (100%)6/6 (100%)
all2538/3347
(75.8%)
1643/1738
(94.5%)
869/887
(98.0%)
455/459
(99.1%)
231/231
(100%)
Note: Months correspond to equal divisions of the calendar year into 12 segments rather than standard calendar months. Sky-area coverage during summer 2018 was much reduced due to reference-building. P48 was closed for maintenance for almost all of October 2018. Most of March 2020 was lost due to weather (3 consecutive weeks of rain/cloud) and few events met the sample criteria. The most recent 1-2 months are generally undercounts, since classifications of declining objects are still being performed. These statistics include some events for which classifications have not yet been publicly released.

BTS Papers


Team Members and Contributors

Christoffer Fremling (Caltech)
Daniel Perley (LJMU)
Adam Miller (Northwestern)
Shri Kulkarni (Caltech)
Aishwarya Dahiwale (Caltech)
Yashvi Sharma (Caltech)
Don Neill (Caltech)
Jesper Sollerman (Stockholm)
Suhail Dhawan (Stockholm)
Ariel Goobar (Stockholm)
Rahul Biswas (Stockholm)
Kirsty Taggart (LJMU)
Melissa Graham (Washington)
Jakob Nordin (Humboldt)
Alison Dugas (Hawaii)
Rachel Bruch (Weizmann)
Steve Schulze (Weizmann)
Ido Irani (Weizmann)
Erez Zimmerman (Weizmann)
Alex Filippenko (UCB)
Kishore Patra (UCB)
Shaunak Modak (UCB)
Andrew Hoffman (UCB)
Jannis Necker (DESY)
Ludwig Rauch (DESY)
Samantha Goldwasser (DESY)