J/AJ/157/229 CALSPEC: WFC3 infrared grism spectrophotometry (Bohlin+, 2019)
CALSPEC: Wide Field Camera 3 infrared grism spectrophotometry.
Bohlin R.C., Deustua S.E.
<Astron. J., 157, 229 (2019)>
=2019AJ....157..229B 2019AJ....157..229B (SIMBAD/NED BibCode)
ADC_Keywords: Infrared sources ; Stars, white dwarf ; Spectrophotometry ;
Spectra, infrared
Keywords: infrared: stars - stars: atmospheres - stars: fundamental parameters -
techniques: spectroscopic
Abstract:
The collections of spectral energy distributions (SEDs) in the Hubble
Space Telescope (HST) CALSPEC database are augmented by 19 infrared (IR)
SEDs from Wide Field Camera 3 (WFC3) IR grism spectra. Together, the two
IR grisms, G102 and G141, cover the 0.8-1.7 µm range with resolutions
of R=200 and 150, respectively. These new WFC3 SEDs overlap existing
CALSPEC Space Telescope Imaging Spectrograph (STIS) standard star flux
distributions at 0.8-1 µm with agreement to ~<1%. Some CALSPEC
standards already have near-IR camera and multi-object spectrogragh
(NICMOS) SEDs; but in their overlap region at 0.8-1.7 µm, the WFC3
data have better wavelength accuracy, better spectral resolution, better
repeatability, and, consequently, better flux distributions of ∼1%
accuracy in our CALSPEC absolute flux SEDs versus ∼2% for NICMOS. With
the improved SEDs in the WFC3 range, the modeled extrapolations to 32 µm
for the James Webb Space Telescope flux standards begin to lose precision
longward of the 1.7 µm WFC3 limit, instead of at the 1.0-µm-long
wavelength limit for STIS. For example, the extrapolated IR flux longward
of 1.7 µm for 1808347 increases by ∼1% for the model fit to the data
with WFC3, instead of just to the STIS SED alone.
Description:
The publicly available WFC3 IR grism observations of CALSPEC stars in
the nominal stare mode include the white dwarf standard stars G191B2B,
GD153, and GD71, plus 16 other CALSPEC stars. These spectra were
acquired at multiple locations on the IR detector. Grism scanned mode
observations of CALSPEC stars will be discussed in a subsequent
publication (S. Deustua & R. Bohlin 2019, in preparation). All the
separate G102 and G141 observations of a source are co-added and
merged. The default merge point where the co-add switches from G102 to
G141 is at 11250 Å. The fluxes of the two independent measurements
agree within the accuracy goal of 1% at the merge point.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 60 19 WFC3 IR observations of CALSPEC stars
table2.dat 31 301 WFC3 IR grism flux calibration sensitivities S
table3.dat 79 8524 WFC3 IR SEDs for 19 stars
table3a.dat 3165 19 Additional meta-data for each standard
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See also:
J/AJ/155/162 : Comparison of IUE and CALSPEC SEDs for 6 WDs (Bohlin+, 2018)
http://www.stsci.edu/hst/observatory/crds/calspec.html : CALSPEC database
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- Star Star name
25- 35 A11 --- ID CALSPEC identifier
37- 41 F5.2 mag Jmag [7.95/15.4]? J band magnitude from Simbad
43- 49 A7 --- SpType Spectral type from Simbad
51- 52 I2 --- G102 [0/77] Number of available WFC3 G102 observations
that are included in our average SEDs
54- 56 I3 --- G141 [0/233] Number of available WFC3 G141 observation
that are included in our average SEDs
58- 60 A3 --- NICMOS [Yes/No] NICMOS observations are also available?
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 0.1nm W-G102 [7608/11800]? The G102 grism wavelength (Å)
7- 15 E9.3 --- S-G102 [999999.0/2.303e+17]? The G102 grism sensitivity
at W-G102 (1)
17- 21 I5 0.1nm W-G141 [10000/17500] The G141 grism wavelength (Å)
23- 31 E9.3 --- S-G141 [8.59e+14/6.604e+17] The G141 grism sensitivity
at W-G141 (1)
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Note (1): In units of electrons/s per (erg/s/cm2/Å).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- ID CALSPEC identifier
13- 19 F7.1 0.1nm Wave [7608/17200] Wavelength (Å)
21- 31 E11.4 ct/s Net [-0.14892/72264] Net electrons per second
at Wave
33- 43 E11.4 cW/m2/nm Flux [-6.8284e-17/7.4841e-13] Flux at Wave
(in erg/s/cm2/Å)
45- 54 E10.4 cW/m2/nm Stat-err [1.5506e-19/0.055355] Statistical uncertainty
in Flux
56- 65 E10.4 cW/m2/nm Sys-err [0/7.4841e-15] The 1% systematic uncertainty
in Flux
67- 69 I3 --- Nobs [0/233] Number of observations
71- 77 F7.1 s Exp [2.9/13084.9] Exposure time
79 I1 --- Qual [0/1] Quality code (1=Good, 0=Bad)
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Byte-by-byte Description of file: table3a.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- ID CALSPEC identifier
13- 21 A9 --- Grism Name of grism(s)
23- 791 A769 --- G102 Co-add list for the G102 grism
793-3121 A2329 --- G141 Co-add list for the G141 grism
3123-3130 F8.3 yr Year1 [2009.21/2016.15] First year of observation
3132-3139 A8 "h:m:s" Time1 First time of observation
3141-3148 F8.3 yr Year2 [2012.08/2017.32] Second year of observation
3150-3157 A8 "h:m:s" Time2 Second time of observation
3159-3165 F7.1 0.1nm Merge [11100/11250]? Merge point (Å)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 14-Aug-2019