## Mission Overview

### TESS Data For Asteroseismology Lightcurves ("TASOC")

Primary Investigator: Rasmus Handberg

HLSP Authors: Rasmus Handberg, Mikkel Lund, Daniel Huber, Derek Buzasi

Released: 2019-06-10

Updated: 2022-10-26

Primary Reference(s): Handberg et al. 2021, Lund et al. 2021

## Overview

The TESS Asteroseismic Science Operations Center (TASOC) provides pipeline-reduced and systematics-corrected TESS light curves for sources up to TESS magnitude 15. TASOC data are optimized for asteroseismology, but can also be used for other applications, including exoplanet science, eclipsing binaries, and stellar activity.

#### Current Releases

##### Data Release 5 and Data Release 6

MAST currently provides light curves from TASOC Data Release 5 (Sectors 1-6) and Data Release 6 (Sectors 14, 15, with Sector 26 to be released soon), as described in Handberg et al. 2021, Lund et al. 2021, and the TASOC DR5 and DR6 release notes.  Before using TASOC data, the team recommends you consult these documents, along with the TESS data release notes for the Sectors you are interested in and the TESS Instrument Handbook.  The TASOC pipeline used to generate the data is open source and available on GitHub.  As in previous releases, DR5 and DR6 include light curves built from 120-second cadence TESS Target Pixel Files (TPFs) and from 1800-second cadence TESS Full Frame Images (FFIs).

From DR5 onward, TASOC releases contain systematics-corrected light curves.  For most 1800-second cadence light curves, users will have a choice between two light curve correction methods.  Light curves corrected by co-trending basis vectors (CBV) are available for both cadences.  Alternatively, light curves corrected by ensemble photometry are additionally available for 1800-second cadence data only, when sufficient nearby comparison stars are available.  The CBV and Ensemble correction methods are described in detail in Sections 3.1 and 3.2 of Lund et al. 2021, with guidance on use cases presented in their Section 4.5.

When both options are available, users are strongly encouraged to examine both the CBV and Ensemble results for a light curve to see if there are significant differences, and read Section 4.5 of Lund et al. 2021.

• Due to a pipeline bug in DR5 ONLY (Sectors 1-6), the following keywords in the FITS headers are underestimated by a factor of exactly 4: DEADC, EXPOSURE, XPOSURE. If these values are needed, please multiply them by 4 before use.
• In Sector 6, the 1800-s light curve for target TIC 53682170 is missing its CBV-corrected variant due to file corruption (but is available as an Ensemble-corrected light curve).
##### Data Release 4

DR4 data have been removed from MAST services, but will remain publicly available on request by emailing the MAST help desk. Please include "Attn: HLSP Team" in your message. If you are a TASC member, you can also access both current and previous releases on the TASOC website.

#### TASC

The TESS Asteroseismic Investigation is organized within the TESS Asteroseismic Science Consortium (TASC). The data platform for TASC is provided via the TESS Asteroseismic Science Operations Center (TASOC), hosted at the Stellar Astrophysics Centre (SAC) at Aarhus University, Denmark. TASOC provides long-term storage of all data products. TASC membership is open to the entire TESS community and any member of TASC can apply to become a member of a given working group within TASC. The TASC Coordinated Activity “TESS Data for Asteroseismology” (T’DA) is responsible for maintaining the TASOC portal and for providing data products for TASC.

All users are welcome to contact the T'DA team if they require custom treatment for a specific target or group of targets. For such cases, the team requests that the T’DA members involved in this treatment should be offered co-authorship on any paper that results.

This work has been supported by TESS Guest Investigator programs G011160, G011155, and G011188, the Stellar Astrophysics Centre, the ESA PRODEX programme, and The Ohio State University "Distinguished University Scientist" program. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (grant agreement no.: DNRF106).

## Data Products

The light curves have the following file naming convention:

hlsp_tasoc_tess_<tessproduct>_tic<id>-s<sector>-<camera>-<ccd>-c<cadence>_tess_<version>_<method>-lc.fits

where:

• <tessproduct> = "ffi" or "tpf", referring to the TESS products from which the light curve is derived (Full Frame Images for 1800-second cadence, Target Pixel Files for 120-second cadence). For users accustomed to the deprecated DR4 release, note that this field was erroneously always "ffi" in DR4, even for TPF products.
• <id> = 11-digit, zero-padded TIC ID, e.g. "00008195883" for TIC 8195883
• <sector> = 4-digit zero-paded TESS sector number, e.g. "0001" for TESS Sector 1
• <camera> = TESS camera, e.g. "cam1" for TESS Camera 1
• <ccd> = TESS CCD, e.g. "ccd1" for TESS CCD 1
• <version> = data release number, e.g. "v05" for DR5
• <method> = "cbv" or "ens", referring to the systematics correction method applied (Cotrending Basis Vectors or Ensemble photometry). See Section 4.5 of Lund et al. 2021 for guidance on which method to use.

The CBVs that were used to derive CBV-corrected light curves have the following file naming convention:

hlsp_tasoc_tess_<tessproduct>_s<sector>-c<cadence>-a<area>_tess_<version>_cbv.fits

where:

• <area> = 3-digit CBV area introduced in Section 3.1.1 of Lund et al. 2021. See that section for the correspondence between CBV files and CBV-corrected light curve files.
• Other fields are the same as described above.

Data product types:

 _cbv-lc.fits T'DA extracted lightcurve with Cotrending Basis Vectors correction method applied _ens-lc.fits T'DA extracted lightcurve with Ensemble correction method applied _cbv.fits File containing CBVs that were used to create _cbv-lc.fits files in a given , provided to ensure reproducability

#### Light curve FITS extensions:

The format of the information provided in the light curve FITS files is intended as much as possible to mimic that provided in TESS mission-provided products.

Each _cbv-lc.fits light curve FITS file has four extensions:

• a “PRIMARY” header (HDU-0) with general information on the star and the observations
• a “LIGHTCURVE” table (HDU-1) with time, raw flux, corrected flux, etc.
• a “SUMIMAGE” (HDU-2) with an image given by the time-averaged pixel data
• an “APERTURE” image (HDU-3) showing the aperture mask used by the pipeline.

Each _ens-lc.fits light curve FITS file has five extensions:

• the four extensions listed above
• an “ENSEMBLE” table (HDU-4) containing information about the specific Ensemble used to detrend that target

#### Light curve data columns

The "LIGHTCURVE" table in HDU-1 is the same for both _cbv-lc.fits and _ens-lc.fits light curve files:

Keyword Units Description
TIME d BJD-245700
TIMECORR d Light arrival time correction applied
CADENCENO (integer) Timestamp count from start of mission
FLUX_RAW e/s Output flux from TASOC photometry module, before systematics-correction
FLUX_RAW_ERR e/s Uncertainty of FLUX_RAW
FLUX_BKG e/s Estimate of background flux
FLUX_CORR ppm CBV-corrected or Ensemble-corrected flux
FLUX_CORR_ERR ppm Uncertainty of FLUX_CORR
QUALITY (integer) TASOC quality flags (see Table 1 in Handberg et al. 2021)
PIXEL_QUALITY (integer) TESS quality flag
MOM_CENTR1 pixels CCD column position of flux-weighted centroid
MOM_CENTR2 pixels CCD row position of flux-weighted centroid
POS_CORR1 pixels Column position correction
POS_CORR2 pixels Row position correction

The "ENSEMBLE" table in HDU-4 of _ens-lc.fits light curve files contains the following:

Keywords Units Description
TIC (integer) TIC IDs of ensemble members used for detrending
BZETA (float) Background offset value; see equation (5) in Lund et al. 2021

## Data Access

TASOC light curves are discoverable throughout MAST cross-mission services, including the MAST Portal web search, the Astroquery python package, and other cross-mission APIs. Set "Provenance Name" to "TASOC" in the Portal's Advanced Search if you wish to restrict results to TASOC. 120-second and 1800-second cadence light curves for the same object are listed as separate Observations in MAST search results. For those 1800-second cadence light curves with both CBV and Ensemble corrected light curves available, both versions of that light curve are bundled together in the same Observation.

For bulk downloads of TASOC _cbv-lc.fits and _ens-lc.fits light curves, we recommend utilizing the following scripts for each Sector via the table below.  The scripts use curl, which is likely already installed on many machines, and if not, is freely available as open source software. The bulk download scripts for the TESS mission-produced products also make use of curl.  You can run each shell script directly in a terminal to retrieve the full set of files, or use a selected subset of the script: each line in the script downloads one TASOC file. CBV and Ensemble files for a given light curve are on separate lines in the script, although both versions of that light curve will be downloaded into the same subfolder dedicated to that light curve. Finally, the full set of _cbv.fits files for each sector can be downloaded as tar bundles, linked in the rightmost column below.

TESS Sector Data Release Total Data Volume

Light Curve

CBV Tar Bundles (Calibration Files)
S1 DR5 1.1 TB Sector 1 Light Curves Sector 1 CBVs
S2 DR5 0.9 TB Sector 2 Light Curves Sector 2 CBVs
S3 DR5 0.8 TB Sector 3 Light Curves Sector 3 CBVs
S4 DR5 1.0 TB Sector 4 Light Curves

Sector 4 CBVs

S5 DR5 1.3 TB Sector 5 Light Curves

Sector 5 CBVs

S6 DR5 1.6 TB Sector 6 Light Curves

Sector 6 CBVs

S14 DR6 2.2 TB

Sector 14 Light Curves

Sector 14 CBVs

S15 DR6 2.0 TB Sector 15 Light Curves

Sector 15 CBVs

Upon execution of the bulk download scripts, the light curves for that sector will download into a directory tree that mirrors the way the files are stored on-disk at MAST. The top level directory will be the Sector (e.g., "s0001/"). 120-second cadence light curves are stored in a sub-directory called "c0120," and 1800-second cadence light curves are stored in a sub-directory called "c1800/". Then, files for a given TIC object are stored at the base of four further sub-directories formed by splitting the zero-padded, 16-digit TIC identifier into four equal pieces (matching the way TESS mission data are stored on-disk at MAST).

For example, s0001/c1800/0000/0000/0819/5883/ contains both the _cbv-lc.fits and _ens-lc.fits versions of the 1800-second cadence light curve for the object TIC 8195883 observed in Sector 1, while s0001/c0120/0000/0000/0819/5883/ contains the 120-second cadence light curve (only _cbv-lc.fits is available) for the same object and sector.

Note: a small number of targets fall on more than one camera-CCD combination within a given sector and cadence. For example, s0001/c1800/0000/0001/4724/8762 contains four files that make up two Observation entries in MAST Portal results with the same target, sector, and cadence. In this example, the two files that look like *cam1-ccd1*_cbv-lc.fits and *cam1-ccd1*_ens-lc.fits comprise the cam1-ccd1 light curve's Observation, and the two files that look like *cam2-ccd4*cbv-lc.fits and *cam2-ccd4*ens-lc.fits comprise the cam2-ccd4 light curve's Observation.

MAST Portal

A web-based interface for cross-mission searches of data at MAST or the Virtual Observatory. Download TASOC light curves for a few targets.

MAST Astroquery

Search for, and retrieve, TASOC data products programmatically in python based on a list of coordinates or target names.

## Citations

Please remember to cite the appropriate paper(s) below and the DOI if you use these data in a published work.

Note: These HLSP data products are licensed for use under CC BY 4.0.