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TESS Input Catalog Version 6 (TIC-6) Release Notes 2018-01-22

This delivery contains the sixth version of the TESS Input Catalog (TIC) produced entirely by the Target Selection Working Group (TSWG), and was finalized and prepared for delivery to the TESS Science Office (TSO) on 2017 December 22. The second version of the candidates target list (CTL-6.2) was prepared for delivery on 2018 March 12.

The delivery has a number of minor issues (see below) which have not been fixed in this version due to time constraints during preparation. Specific details of the method of production and the contents of this TIC will be described in the full TIC-6 Documentation expected to be on the arXiv in April 2018. The TIC-5 Documentation can currently be found on the arXiv at (https://arxiv.org/abs/1706.00495), and should be used as a reference until the full documentation is updated, as much of the schema in TIC-5 and TIC-6 remains unchanged.

The design is the same as TIC-5, in that the columns and their format are the same, but there have been significant changes compared to TIC deliveries prior to TIC-6. TIC IDs have not been changed and all future deliveries of the TIC will use the same IDs for specific objects. New objects added to the TIC will always receive new IDs. Objects may be removed from the TIC, if they are found to be spurious, but TIC IDs will always be unique and a new TIC object will never receive the ID of an old TIC object.

Changes compared to TIC-5

This delivery contains major changes in computed quantities compared to TIC-5. It should be noted that the methods used to estimate a variety of stellar parameters are still under active development and can be affected by poor catalog photometry when there is no acceptable alternative photometry for a given star. The major changes compared to previous versions are:

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1. The radius now scales as R^1.5, rather than R (column 71).
2. For both CTL6.1 and CTL6.2, the given star’s priority is now boosted based on the star’s ecliptic latitude (column 28) and the number of sectors the star is likely to appear in, rather than a factor of sqrt(13) if the star was in the continuous viewing zone. Generally, this boosts the priority of stars closer to a continuous viewing zone. For CTL-6.2, the gaps in priority from the expected positions of camera gaps have been removed
3. For CTL-6.1, the priority function scaled with (sqrt(cratio+1)*phot_err) rather than sqrt(sqrt(cratio+1)*phot_err), where cratio is the contamination ratio (column 85) and phot_err is the photometric error provided by Sullivan et al. 2015 based on the TESS magnitude of the star (column 61). For CTL-6.2,the expected photometric error is now directly calculated using the same formalism from Sullivan et al. 2015, where the total noise (N) is defined as: N= sqrt(Nstar^2+Nsky^2+Ncont^2+Nread^2+Nsys^2). Nstar represents the photon error from the star; Nsky represents the photon error from the sky background; Ncont is the expected photon error from contaminants in the aperture (this replaces the contamination ratio); Nread is the readout error of the detector; and N sys is the unrecoverable 60ppm systematic error that is expected. Pepper et al. 2018 explains this new formalism in greater detail.

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