J/A+A/619/A180 Gaia DR2 photometric sensitivity curves (Maiz Apellaniz+, 2018)
Reanalysis of the Gaia Data Release 2 photometric sensitivity curves using
HST/STIS spectrophotometry.
Maiz Apellaniz J., Weiler M.
<Astron. Astrophys. 619, A180 (2018)>
=2018A&A...619A.180M 2018A&A...619A.180M (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Photometry, G band ; Photometry, sensitivity functions
Keywords: surveys - methods: data analysis - techniques: photometric
Abstract:
The second data release (DR2) from the European Space Agency mission
Gaia took place on April 2018. DR2 included photometry for more than
1.3x109 sources in the three bands G, GBP, and GRP. Even though
the Gaia DR2 photometry is very precise, there are currently three
alternative definitions of the sensitivity curves that show
significative differences.
The aim of this paper is to improve the quality of the input
calibration data to produce new compatible definitions of the G,
GBP, and GRP bands and to identify the reasons for the
discrepancies between previous definitions.
We have searched the Hubble Space Telescope (HST) archive for Space
Telescope Imaging Spectrograph (STIS) spectra with G430L+G750L data
obtained with wide apertures and combined them with the CALSPEC
library to produce a high quality spectral energy distribution (SED)
library of 122 stars with a broad range of colors, including three
very red stars. This library defines new sensitivity curves for G,
GBP, and GRP using a functional analytical formalism.
The new sensitivity curves are significantly better than the two
previous attempts we use as a reference, REV (Evans et al.,
2018A&A...616A...4E 2018A&A...616A...4E, Cat. I/345) and WEI (Weiler,
2018A&A...617A.138W 2018A&A...617A.138W, Cat. J/A+A/617/A138). For G we confirm the
existence of a systematic bias in magnitude and correct a color term
present in REV. For GBP we confirm the need to define two magnitude
ranges with different sensitivity curves and measure the cut between
them at Gphot=10.87mag with a significant increase in precision. The
new curves also fit the data better than either REV or WEI. For GRP,
our new sensitivity curve fits the STIS spectra better and the
differences with previous attempts reside in a systematic effect
between ground-based and HST spectral libraries. Additional evidence
from color-color diagrams indicate that the new sensitivity curve is
more accurate. Nevertheless, there is still room for improvement in
the accuracy of the sensitivity curves because of the current dearth
of good-quality red calibrators: adding more to the sample should be a
priority before Gaia data release 3 takes place.
Description:
File table2 contains the parallel and orthogonal sensitivity curves
for the Gaia DR2 bands G, GBP (bright, G<10.87), GBP (faint,
G>10.87), and GRP. The total sensitivity curve is the sum of the
parallel and orthogonal components for each band.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 79 3201 Parallel and orthogonal sensitivity curves
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/617/A138 : Revised Gaia Data Release 2 passbands (Weiler, 2018)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 F7.1 0.1nm lambda Wavelength
9- 16 F8.5 --- Gpar G band parallel component
18- 25 F8.5 --- Gort G band orthogonal component
27- 34 F8.5 --- GBPbpar GBP band bright parallel component
36- 43 F8.5 --- GBPbort GBP band bright orthogonal component
45- 52 F8.5 --- GBPfpar GBP band faint parallel component
54- 61 F8.5 --- GBPfort GBP band faint orthogonal component
63- 70 F8.5 --- GRPpar GRP band parallel component
72- 79 F8.5 --- GRPort GRP band orthogonal component
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Acknowledgements:
Jesus Maiz Apellaniz, jmaiz(at)cab.inta-csic.es
(End) Patricia Vannier [CDS] 06-Sep-2018