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Currently known quirks and issues with TICv8

General Issues

There are a number of minor issues, and quirks, which have been identified by the TSWG. Users should read this section carefully, before accepting TIC quantities at face value.

Some stars may have reported stellar parameter errors that are larger than the parameter quantity. Users are cautioned against using these parameters in calculations for publications.
Users are reminded that stars that have ecliptic latitudes between -6 and 6 degrees have their priorities set to zero. This “gap” in priority is meant to mimic the expected gap in camera coverage for the two year primary TESS mission.
Some stars in the hot subdwarf list do not have errors for their stellar parameters. These were adopted ‘as-is’ for consistency.
The disposition column identifies objects that are included in the TIC, but are likely spurious, or related to other TIC objects in a non-trivial, non-astrophysical way. Currently, this column is populated as a NULL, DUPLICATE (6), ARTIFACT (7), or SPLIT (8). When a single star in a previous TIC is found to be two or more actual sources due to the enhanced resolution of Gaia DR-2, the original TICID gets the disposition SPLIT. New TICIDs are assigned to the objects and the original TICID is in column DUP_ID (column 87). The original star “SPLIT” star will have NULL in the dup_id. The DUPLICATE flag means the star is listed twice (or more) in the TIC due to prior cross-matching difficulties. In this case, DUP_ID contains the TICID of the real star.
Users should note the metallicity (column 69) has been adopted when available from a spectroscopic catalog, but it is not directly used in any calculation. This may result in physical parameters that are not strictly consistent with the reported metallicity.
The listed RA (column 14) and Dec (column 15) are not measured positions, but positions which have been propagated to EPOCH J2000.0. Users should not try to propagate forward the TIC coordinates using the proper motions listed. Instead, users should use the original catalog position (column 119 & 120), proper motions (columns 17 & 19), and corresponding errors for propagation.
If a star is identified as a subgiant, and a mass and log(g) are provided, users should not consider these parameters to be reliable, because the empirical relations designed to calculate the mass are valid for dwarf stars. However the luminosity and effective temperature should be accurate.
Asymmetric errors are computed using a Monte Carlo method and are only provided for CTL stars which are not in a specially curated list. There are borderline cases where the peak of the property-distribution was too close to the validity-limit of the property-relation in order to compute reliable errors. These stars will have no or asymmetric errors for just some properties.

Joins

All stars affected are stars originating from TIC7 which did not get matched up with a Gaia DR2 star in TIC8. In all these cases, it turned out that there is a valid match between the TIC7 star and a Gaia DR2 star, and thus it is possible to update the older TIC7 values that eneded up in TIC8 with improved, Gaia-derived values, unless it is a star from a specially curated list, in which case the parameters are taken from those curated lists.

The following table summarizies the known cases. These targets are identical and should have been matched together in TIC v8, but were not. Users should be aware that these are the same objects, and thus parameters from the TIC8 ID under the "Gaia DR2" column can be associated with the same TIC8 ID in the "from TIC7" column.

TOI	TIC8 ID (from TIC7)	TIC8 ID (from GaiaDR2)	Comments
454.01	153077621	651051509	153077621 is a cool dwarf
573.01	296780789	876200724	296780789 is a cool dwarf
722.01	38509907	684936227	38509907 has a spectroscopic Teff
1421.01	329277372	2019613336	Gaia photometry unreliable, RUWE = 41.2 (not ok)

Splits

In this case a star originating from TIC7 is an unresolved double-star in 2MASS and has at least two entries in Gaia DR2 that did not get matched up properly in TIC8. All magnitudes (Tessmag, Vmag, J, H, K, etc) and stellar properties of the TICID (Teff, radius, mass, etc) are most likely corrupted and should NOT be used. How strong they are affected depends on the ratio of fluxes (e.g., the values from the TIC IDs corresponding to the resolved Gaia DR2 sources). IMPORTANT: Please note that there is no way to tell if any TESS signal came from a given star in the unresolved binary system.

The following table contains the original TIC8 ID (from the unresolved source in TIC7) and the two TIC8 IDs for the source coming from the Gaia DR2 IDs.

TOI	TIC8 ID (from TIC7 source)	TIC8 ID (from Gaia-resolved source #1)	TIC8 ID (from Gaia-resolved source#2)	Comments
--	92359852	651667036	651667038	RUWE < 1.1 for 92359852 and 651667036 (ok)
1606.01	125735470	640763859	640763860	125735470 and 640763859 have similar properties
268.01	219253008	685340264	685340263	219253008 and 685340264 have similar properties
1014.01	96246348	772008799	772008800	772008799 is brighter, but too hot for stellar property estimation
1044.01	463402815	854828119	854828120	flags for 854828119 not ok, but ruwe = 0.93
--	385105618	642958052	642958048	flagged as multiple in TIC7, split now, spect teff

Artifacts

So far we have only one identified: TIC 269701145 (close to TOI 1339). This is an entry originating from 2MASS (20080397+6651023), sitting on an artifact around the bright star TIC 269701147. We know that this is not the only artifact in 2MASS and that they are prone to sit on diffraction spikes around bright stars. For TIC8 we had no time to find a safe way to sort them out without loosing bonafide stars.

TICv8 Column Schema - Executive Summary

Column Number	Column Name	Data Type	Description	Units
1	ID	long	TESS Input Catalog identifier
2	Version	string	Version Identifier for this entry	yyyymmdd
3	HIP	long	Hipparcos Identifier
4	TYC	string	Tycho2 Identifier
5	UCAC	string	UCAC4 Identifier
6	TWOMASS	string	2MASS Identifier
7	SDSS	string	SDSS DR9 Identifier
8	ALLWISE	string	ALLWISE Identifier
9	GAIA	string	GAIA Identifier
10	APASS	string	APASS Identifier
11	KIC	long	KIC Identifier
12	Objtype	string	Object Type
13	Typesrc	string	Source of the object
14	RA	double	Right Ascension epoch 2000	deg
15	Dec	double	Declination epoch 2000	deg
16	Posflag	string	Source of the position
17	pmRA	double	Proper Motion in Right Ascension	mas/yr
18	e_pmRA	double	Uncertainty in PM Right Ascension	mas/yr
19	pmDec	double	Proper Motion in Declination	mas/yr
20	e_pmDec	double	Uncertainty in PM Declination	mas/yr
21	PMFlag	string	Source of the Proper Motion
22	plx	double	Parallax	mas
23	e_plx	double	Error in the parallax	mas
24	PARFlag	string	Source of the parallax
25	GalLong	double	Galactic Longitude	deg
26	GalLat	double	Galactic Latitude	deg
27	EcLong	double	Ecliptic Longitude	deg
28	EcLat	double	Ecliptic Latitude	deg
29	Bmag	float	Johnson B	mag
30	e_Bmag	float	Uncertainty in Johnson B	mag
31	Vmag	float	Johnson V	mag
32	e_Vmag	float	Uncertainty in Johnson V	mag
33	umag	float	Sloan u	mag
34	e_umag	float	Uncertainty in Sloan u	mag
35	gmag	float	Sloan g	mag
36	e_gmag	float	Uncertainty in Sloan g	mag
37	rmag	float	Sloan r	mag
38	e_rmag	float	Uncertainty in Sloan r	mag
39	imag	float	Sloan I	mag
40	e_imag	float	Uncertainty in Sloan I	mag
41	zmag	float	Sloan z	mag
42	e_zmag	float	Uncertainty in Sloan z	mag
43	Jmag	float	2MASS J	mag
44	e_Jmag	float	Uncertainty in 2MASS J	mag
45	Hmag	float	2MASS H	mag
46	e_Hmag	float	Uncertainty in 2MASS H	mag
47	Kmag	float	2MASS K	mag
48	e_Kmag	float	Uncertainty in 2MASS K	mag
49	TWOMflag	string	Quality Flags for 2MASS
50	prox	float	Distance to 2MASS nearest neighbor	arcsec
51	W1Mag	float	WISE W1	mag
52	e_W1Mag	float	Uncertainty in WISE W1	mag
53	W2Mag	float	WISE W2	mag
54	e_W2Mag	float	Uncertainty in WISE W2	mag
55	W3Mag	float	WISE W3	mag
56	e_W3Mag	float	Uncertainty in WISE W3	mag
57	W4mag	float	WISE W4	mag
58	e_W4Mag	float	Uncertainty in WISE W4	mag
59	Gmag	float	GAIA G Mag	mag
60	e_Gmag	float	Uncertainty in GAIA G	mag
61	Tmag	float	TESS Magnitude	mag
62	e_Tmag	float	Uncertainty in TESS Magnitude	mag
63	TESSFlag	string	TESS Magnitude Flag
64	SPFlag	string	Stellar Properties Flag
65	Teff	float	Effective Temperature	K
66	e_Teff	float	Uncertainty in Effective Temperature	K
67	logg	float	log of the Surface Gravity	cgs
68	e_logg	float	Uncertainty in Surface Gravity	cgs
69	M/H	float	Metallicity	dex
70	e_M/H	float	Uncertainty in the Metallicity	dex
71	Rad	float	Radius	solar
72	e_Rad	float	Uncertainty in the Radius	solar
73	Mass	float	Mass	solar
74	e_Mass	float	Uncertainty in the Mass	solar
75	rho	float	Stellar Density	solar
76	e_rho	float	Uncertainty in the Stellar Density	solar
77	LumClass	string	Luminosity Class
78	Lum	float	Stellar Luminosity	solar
79	e_Lum	float	Uncertainty in Luminosity	solar
80	d	float	Distance	pc
81	e_d	float	Uncertainty in the distance	pc
82	e(b-v)	float	Applied Color Excess	mag
83	e_e(b-v)	float	Uncertainty in Applied Color Excess	mag
84	numcont	long	Number of Contamination Sources
85	contratio	float	Contamination Ratio
86	disposition	string	Disposition type
87	dup_id	long	Points to the duplicate object TIC ID
88	priority	double	CTL priority

The following columns have been added to the public release of TICv8 on MAST

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Some stars will have distinct priorities:

Stars with log(g) values that are greater than 5 have had their priorities set to 0 to avoid biases from poor quality effective temperature, extinction, or parallax measurements. Stars in the specially curated lists are excluded from this scenario.

Stars with ecliptic latitudes (column 28) less than ~6 degrees in absolute value are not expected to be observed as part of the main mission due to a gap in camera coverage between the Southern and Northern observations. Therefore, their Ns values are 0 and thus the priority is 0.

89 eneg_EBV The lower asymmetric error on the color excess. The asymmetric errors are calculated using a Monte-Carlo procedure for stars in CTLv8.01 (see section 3.2.2 of the full documentation).

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