AstroNote 2019-10

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DRAFT
2019-05-09 06:15:15
Type: Announcement-General
Six months of automatic TNS submission of ZTF transients using AMPEL
Authors: J. Nordin, V. Brinnel, M. Giomi, J. van Santen (HU Berlin), A. Gal-Yam, O. Yaron, S. Schulze (Weizmann)
Source Group: ZTF

Dear TNS users,

The automatic submission of candidate extragalactic transients from the ZTF public extragalactic survey to the TNS has now been active for 6 months. Between 5 and 30 transients are submitted on an average night. The goal of this project has been to provide the community immediate access to high quality supernovae (and galaxy core variables), without requiring knowledge of the more technical aspects of the ZTF alert stream.

We would like to make a few comments based on questions we often receive:

- Two ZTF "senders" are currently active: ZTF_AMPEL_NEW submits only transients less than five days old at the time of submission. This is thus suitable for observers looking for e.g. young supernovae, but will by design omit slowly rising objects and be biased against regions with previous variability (e.g. central regions of galaxies). The ZTF_AMPEL_COMPLETE sender uses more relaxed age criteria and will thus encompass also such candidates.

- We work hard at keeping the contamination from variable stars low. This is currently estimated at below 5% for transients brighter than 19.5 mag. We thus use this as an upper mag limit for all submissions. This will only be increased once we can guarantee a low contamination also for fainter transients.

- If a bright ZTF candidate has not been submitted to the TNS there is usually a good reason for this. Selections are made using the AMPEL framework (or broker) and relies on a combination of cuts based on alert properties as well as catalog matches. Catalog information is currently drawn from Gaia, SDSS, PanSTARRS, NED, Milliquas, AAVSOVSX and LAMOST. Please contact us if you have questions regarding a particular transient or have requests for what other transients we should look for!

More details regarding the selection methodology can be found in the AMPEL introduction: https://arxiv.org/abs/1904.05922. Instructions for how to create a channel to directly process the alert stream can be found at https://github.com/AmpelProject/Ampel-contrib-sample.