Mission Overview

KBonus-Background ("KBONUS-BKG")

 

Primary Investigator: Jorge Martinez-Palomera

HLSP AuthorsJorge Martinez-Palomera, Christina Hedges, and Jessie Dotson

Released: 2023-11-01

Updated: 2023-11-01

Primary Reference(s): Martinez-Palomera et al. 2023

DOI: 10.17909/7jbr-w430

Citations: See ADS statistics

Read Me 

 

Slideshow

Kepler FOV density

Spatial distribution (2D histogram) of Kepler targets (top) and KBonus background sources (bottom) brighter than the magnitude 19th in the G-band across the Kepler field of view. KBonus Background sources are stars that are fully or partially contained within a Kepler TPF but are not primary targets, and therefore, the Kepler pipeline did not analyze them. The
overdensities on the top panel correspond to particular stellar clusters, while on the bottom panel, the overdensities closely follow the true underlying distribution of stars.

Estimated CDPP in ppm as a function of G-band magnitude

Six-hour estimated combined differential photometric precision (CDPP) in parts-per-million (PPM) as a function of G-band magnitude from the perturbed PSF (top) and aperture (middle) light curves. CDPP estimates the noise properties of Kepler data, where lower values indicate a more precise light curve. The bottom panel shows a direct comparison of PSF and aperture CDPP values. The black and orange lines follow the CDPP distribution maximum in a brightness bin (0.1 magnitude width). 

Color magnitude diagram

Color-magnitude diagrams of the KBonus catalog presented in this work. Only Kepler targets are in the top left panel, new background sources are in the top right panel, and the combination of both data sets is in the bottom left panel. The fraction of new sources over Kepler targets in the CMD is shown in the bottom right panel.

Overview

KBONUS-BKG uses the Linearized Field Deblending (LFD) method, a Point Spread Function (PSF) photometry algorithm, to create PSF light curves. Gaia DR3 data is used as an input catalog to extract 606,900 light curves, from which 406,548 correspond to background sources and 200,352 are Kepler targets. PSF models were fitted using Kepler's full-frame images and later evaluated in the Target Pixel Files (TPFs) of Kepler targets. The LFD method provides a mean PSF estimate and a perturbed PSF that corrects for systematics within an observing quarter. Additionally, aperture photometry is estimated directly from the PSF shape per source and optimized for flux completeness and contamination. The PSF light curves have comparable quality as those computed by the Kepler pipeline, with combined differential photometric precision (CDPP) values under 100 ppm for sources brighter than G = 16. The light curve files include PSF, aperture photometry, and relevant extraction metrics. A full description of this dataset can be found in Martinez-Palomera et al. (2023) and the Python library PSFMachine that was used to extract the light curves for this data set.  See Jupyter Notebook tutorials on how to load the light curves and what to expect in the FITS files.

 

Data Products

KBONUS-BKG provides 606,900 light curves, a catalog of extracted sources, a catalog of specific objects of interest, and bundle tarball files for specific types of sources of interest for quick download.  

Data file naming convention:

hlsp_kbonus-bkg_kepler_kepler_<target>_kepler_v1.0_<prodtype>.<ext>

where:

  • <target> represents the source ID, e.g., "kic-005732587" if the source exists in the Kepler Input Catalog or "gaia-dr3-2126999613236789376" if not, for lightcurves. For catalogs and bundles, it is the name of the interested specific sources, one of "source" for all lightcurve sources, "mstars" for M dwarfs, " wd" for white dwarfs, or "kois-nns" for all the KOIs and their neighbors within a 30'' radius.
  • <prodtype> represents the product type, for instance, "lc" for lightcurves, "cat" for catalogs", or "tar.gz" for compressed tarballs of interested sources.
  • <ext> is the extension of the file, one of "fits" or "tar.gz".

Data file types:

_lc.fits Lightcurves
_cat.fits Catalogs
_lcf.tar.gz Bundled lightcurves

Lightcurve Files

Lightcurve FITS files contain multiple extensions, which consist of LIGHTCURVE BinTables and APERTURE images for quarters where the sources were detected. Therefore, the number of extensions varies for sources. The LIGHTCURVE STITCHED is the main extension containing the fully stitched time series. The LIGHTCURVE_Q extensions contain the light curve for single quarters. This extension contains per-quarter metrics and other measurements such as centroid and PSF model chi-square values. The APERTURE_Q extension contains the pixel mask of the corresponding quarter used for the aperture photometry in the shape of the TPF of origin. The FITS files are structured to work seamlessly with the lightkurve package. In this way, users can easily load the stitched light curve into a LightCurve object.

Description of the columns available in the LIGHTCURVE STITCHED extension

Column Field Format Units Description
1 Time

float64

BJD - 2454833

Time value in BKJD

2

Cadenceno

int32 -

Cadence number

3 Quarter int32 - Quarter number
4

Flux

float64

e/s

PSF flux from stitched quarters

5

Flux_err

float64 e/s

PSF flux error from stitched quarters

6 SAP_flux float64 e/s

SAP flux from stitched quarters

7

SAP_flux_err

float64 e/s

SAP flux error from stitched quarters

8

PSF_flat_flux

float64 e/s PSF flux from stitched quarters after flattening
9

PSF_flat_flux_err

float64 e/s

PSF flux error from stitched quarters after flattening

10

SAP_quality

int32 -

Quality flag from the TPF

11

Flatten_mask

int32 -

Quality flag from the flattening process

Description of the columns available in the LIGHTCURVE_Q extension

Column Field Format Units Description
1

Cadenceno

int32 -

Cadence number

2 Time

float64

BJD - 2454833

Time value in BKJD

3

Flux

float64

e/s

Corrected PSF flux

4

Flux_err

float64 e/s

Corrected PSF flux error

5 SAP_flux float64 e/s

SAP flux 

6

SAP_flux_err

float64 e/s

SAP flux error

7

Centroid_Column

float64 pix

Centroid column value

8

Centroid_Row

float32 pix

Centroid row value

9

SAP_quality

int32 -

Quality flag from the TPF

10

SAP_BKG

float64 e/s

SAP background flux

11

Red_chi2

float32 -

Reduced chi-squared value between PSF model and data

12

PSF_flat_nova

float64 e/s Mean PSF flux
13

PSF_flat_nova_err

float64 e/s Mean PSF flux error

 

Source Catalogs 

The catalog (hlsp_kbonus-bkg_kepler_kepler_source-list_kepler_v1.0_cat.fits) released with this work contains the list of extracted sources resulting in a light curve FITS file. It also contains extraction metrics and availability flags that can be used to filter sources. The detailed column description is as follows.

Column Field Format Units Description
1

gaia designation

string

-

Gaia designation number

2

ra

float32 deg

Right Ascension

3

dec

float32

deg

Declination

4

sap_mean_flux

float32 e/s

Mean of SAP flux

5

sap_mean_flux_err

float32 e/s

Mean of SAP flux error

6

psf_mean_flux

float32 e/s

Mean of PSF flux

7

psf_mean_flux_err

float32 e/s

Mean of PSF flux error

8

flfrcsap

float32 -

Minimum detected SAP flux fraction

9

crowdsap

float32 -

Minimum detected SAP crowding

10

npixsap

float32 -

Minimum detected SAP number of pixels

11

psffrac

float32 -

Minimum detected PSF fraction

12

pertrati

float32 -

Mean detected perturbed/mean PSF ratio

13

pertstd

float32 -

Minimum detected perturbed PSF standard

14

psf_avail

string -

String encoding PSF flux availability per quarter

15 sap_avail string -

String encoding SAP flux availability per quarter

16

psf_fraction_flag

string -

String encoding PSF fraction quality per quarter

17

phot_g_mean_mag

float32 mag

Gaia G band mean magnitude

18

phot_bp_mean_mag

float32 mag

Gaia BP band mean magnitude

19

phot_rp_mean_mag

float32 mag

Gaia RP band mean magnitude

20

tpf_org

int32 -

TPF where sources were detected

21 kic int32 -

Kepler input catalog number

22 kic_sep float32 arcsec Distance to KIC source
23 kepmag float32 mag Kepler magnitude
24 file_name string -

FITS file name

 

The KOIs and neighbors catalog (hlsp_kbonus-bkg_kepler_kepler_kois-nns-catalog_kepler_v1.0_cat.fits) has the following columns.

Column Field Format Units Description
1 gaia_designation String - Gaia designation number
2 ra Float32 deg Right Ascension
3 dec Float32 deg Declination
4 kic Int32 - Kepler input catalog number
5 fname String - Light curve FITS file name
6 nn_koi Int32 - Nearest KOI
7 nn_dist Float32 arcsec Distance to nearest KOI

 

The M-stars catalog (hlsp_kbonus-bkg_kepler_kepler_mstars_kepler_v1.0_lcf.tar.gz) has the following columns.

Column Field Format Units Description
1 gaia_designation String - Gaia designation number
2 ra Float32 deg Right Ascension
3 dec Float32 deg Declination
4 kic Int32 - Kepler input catalog number
5 fname String - Light curve FITS file name

 

The white dwarfs catalog (hlsp_kbonus-bkg_kepler_kepler_wd_kepler_v1.0_lcf.tar.gz) has the following columns.

Column Field Format Units Description
1 gaia_designation String - Gaia designation number
2 ra Float32 deg Right Ascension
3 dec Float32 deg Declination
4 kic Int32 - Kepler input catalog number
5 fname String - Light curve FITS file name
6 Pwd Float32 - White dwarf probability

Data Access

Lightcurves are available in the MAST Portal (web-based, cross-mission search interface) and Astroquery (Python package to search for and download files from Python scripts you write). We also provide a bulk download cURL script for all lightcurves below. Catalogs and bundled lightcurves for specific targets can be accessed via the direct download table below.

Portal Advanced Search:

Set the Provenance Name filter to KBONUS-BKG and the target names or the RA/Dec filters to the interested field of view in the Portal Advanced Search to find individual lightcurves. Each observation in the Portal contains a single source's lightcurve. Note that since the total number of KBONUS-BKG is larger than the load limit (50,000) and the download limit (500,000), you can use the direct download bulk script below to download all lightcurves or narrow down your search for specific lightcurves using the RA/Dec filters.

Astroquery Access:

The lightcurves can also be retrieved programmatically by using the astroquery—mast module. See the code example below for counting the total number of observations and retrieving and downloading lightcurve files.  See more examples in Astroquery and API filter parameters.

from astroquery.mast import Observations

# Getting the total observation counts
print(Observations.query_criteria_count(provenance_name= "kbonus-bkg"))

# Filtering observations by Gaia DR3 target names and RA/Dec
gaia_obs = Observations.query_criteria(provenance_name= "kbonus-bkg", target_name ="*GAIA DR3*", s_ra=[293.2, 294.5], s_dec=[50.5, 51.5])

# Getting the product list
data_products = Observations.get_product_list(gaia_obs)
print(data_products)

# Download the observations
Observations.download_products(data_products)

 

  • A web-based interface for cross-mission searches of data at MAST or the Virtual Observatory
  • Search for and retrieve KBONUS-BKG data products programmatically.

 

Bulk download script File size Total data size after download Description

hlsp_kbonus-bkg_kepler_lightcurves_all_kepler_v1_lftp.sh

4.0 KB 4.8 TB lftp script to download all lightcurves

hlsp_kbonus-bkg_kepler_lightcurves_all_kepler_v1_bulkdl.sh

29 MB

4.8 TB cURL script to download all lightcurves

hlsp_kbonus-bkg_kepler_lightcurves_all_kepler_v1_chunkdl.zip

6.8 MB 4.8 TB Compressed cURL scripts. Each uncompressed script will download 50,000 lightcurves. 

The catalog released with this work contains the list of extracted sources resulting in a light curve FITS file. It also contains extraction metrics and availability flags that can be used to filter sources. The catalogs can be accessed via direct links below.

Files File Size Description
hlsp_kbonus-bkg_kepler_kepler_source-catalog_kepler_v1.0_cat.fits 140 MB Source catalog for all lightcurves
hlsp_kbonus-bkg_kepler_kepler_kois-nns-catalog_kepler_v1.0_cat.fits 2.6 MB

Lightcurves listed in the NASA Exoplanet Archive, including confirmed and false positive candidates. It also includes the light curves of neighbor sources around each KOI in a 30′′ radius. 

There are ∼ 32, 000 light curve files. This data bundle is helpful for users who desire to explore false-positives candidates and their neighbors.

hlsp_kbonus-bkg_kepler_kepler_mstars-catalog_kepler_v1.0_cat.fits 2.0 MB Source catalog for M dwarfs; 

It contains a total of ∼ 20, 000 sources. 

hlsp_kbonus-bkg_kepler_kepler_wd-catalog_kepler_v1.0_cat.fits 24 KB Source catalog for white dwarfs

 

To facilitate data access to specific source types, the team has created the following data bundles:

Files File Size Description

hlsp_kbonus-bkg_kepler_kepler_kois-nns_kepler_v1.0_lcf.tar.gz

204 GB

Lightcurve bundle for KOIs and neighbors

hlsp_kbonus-bkg_kepler_kepler_mstars_kepler_v1.0_lcf.tar.gz

134 GB

Lightcurve bundle for M Dwarfs

hlsp_kbonus-bkg_kepler_kepler_wd_kepler_v1.0_lcf.tar.gz

373 MB

Lightcurve bundle for White Dwarfs; It contains a total of ∼ 90 light curves.

 

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.

References