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J/AJ/112/2274 Spectral irradiance calibration. VII. (Cohen+ 1996)
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Spectral irradiance calibration in the infrared. VII.
New composite spectra, comparison with model atmospheres, and
far-infrared extrapolations
Cohen M., Witteborn F.C., Carbon D.F., Davies J.K., Wooden D.H.,
Bregman J.D.
<Astron. J. 112, 2274 (1996)>
=1996AJ....112.2274C
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ADC_Keywords: Spectra, infrared ; Stars, standard
Abstract:
We present five new absolutely calibrated continuous stellar spectra
constructed as far as possible from spectral fragments observed from
the ground, the Kuiper Airborne Observatory (KAO), and the IRAS Low
Resolution Spectrometer. These stars, alpha Boo, gamma Dra, alpha
Cet, gamma Cru, and mu UMa, augment our six, published, absolutely
calibrated spectra of K and early-M giants. All spectra have a common
calibration pedigree. A revised composite for alpha Boo has been
constructed from higher quality spectral fragments than our previously
published one. The spectrum of gamma Dra was created in direct
response to the needs of instruments aboard the Infrared Space
Observatory (ISO); this star's location near the north ecliptic pole
renders it highly visible throughout the mission. We compare all our
low-resolution composite spectra with Kurucz model atmospheres and
find good agreement in shape, with the obvious exception of the SiO
fundamental, still lacking in current grids of model atmospheres. The
CO fundamental seems slightly too deep in these models, but this could
reflect our use of generic models with solar metal abundances rather
than models specific to the metallicities of the individual stars.
Angular diameters derived from these spectra and models are in
excellent agreement with the best observed diameters. The ratio of our
adopted Sirius and Vega models is vindicated by spectral observations.
We compare IRAS fluxes predicted from our cool stellar spectra with
those observed and conclude that, as 12 and 25um, flux densities
measured by IRAS should be revised downwards by about 4.1% to 5.7%,
respectively, for consistency with our absolute calibration. We have
provided extrapolated continuum versions of these spectra to 300um,
in direct support of ISO (PHT and LWS instruments). These spectra are
consistent with IRAS flux densities at 60 and 100um.
Objects:
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RA (2000) DE Designation(s)
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14 15 43.5 +19 12 37 alpha Boo = HD 124897 = HR 5340
17 56 36.3 +51 29 21 gamma Dra = HD 164058 = HR 6705
03 02 16.7 +04 05 27 alpha Cet = HD 18884 = HR 911
12 31 09.7 -57 06 34 gamma Cru = HD 108903 = HR 4763
10 22 20.0 +41 29 57 mu UMa = HD 89758 = HR 4069
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4a.dat 55 646 alp Boo composite spectrum
table4b.dat 55 633 gam Dra composite spectrum
table4c.dat 55 710 alp Cet composite spectrum
table4d.dat 55 395 gam Cru composite spectrum
table4e.dat 55 614 mu UMa composite spectrum
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See also:
J/AJ/110/275 : IR spectra of standard stars (Cohen+ 1995)
J/AJ/112/241 : Spectral irradiance calibration. VI. (Cohen+ 1996)
Byte-by-byte Description of file: table4*.dat
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Bytes Format Units Label Explanations
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1-11 E11.4 um Lambda Wavelength
12-22 E11.4 W/cm2/um Irrad Irradiance
23-33 E11.4 W/cm2/um UTotal Total uncertainty
34-44 E11.4 % ULocal Local bias
45-55 E11.4 % UGlobal Global bias
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Photometry actually used to construct the spectrum:
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Star Name FWHM Mag.+/-Unc. Eff Wvl Eff Wvl Flambda Source
(Vega) (star) W/cm2/um
(um) (um) (um)
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alp Boo Kn 0.0488 -3.07 0.01 2.208 2.205 6.69E-13 Selby/Hammersley
alp Boo Ln 0.1443 -3.15 0.01 3.782 3.762 9.35E-14 Selby/Hammersley
alp Boo M 0.6677 -2.97 0.02 4.758 4.738 3.24E-14 Strecker et al. 1979
alp Boo UKIRT87 0.8611 -3.13 0.01 8.770 8.779 3.43E-15 UKIRT Service data
alp Boo UKIRT98 0.9455 -3.16 0.01 9.843 9.828 2.23E-15 UKIRT Service data
alp Boo UKIRT11 1.1198 -3.16 0.01 11.641 11.639 1.15E-15 UKIRT Service data
alp Boo UKIRT12 1.1782 -3.19 0.01 12.432 12.427 9.13E-16 UKIRT Service data
gam Dra Kn 0.0488 -1.37 0.01 2.208 2.205 1.40E-13 Selby/Hammersley
gam Dra Ln 0.1443 -1.49 0.02 3.782 3.765 2.06E-13 Selby/Hammersley
gam Dra TCS-H 0.2600 -1.15 0.01 1.636 1.645 3.27E-13 Alonso et al. 1994
gam Dra TCS-K 0.3941 -1.31 0.01 2.160 2.158 1.40E-13 Alonso et al. 1994
gam Dra TCS-L' 0.5725 -1.46 0.02 3.649 3.651 2.22E-14 Alonso et al. 1994
gam Dra UKIRT87 0.8611 -1.38 0.01 8.770 8.780 6.86E-16 UKIRT Service data
gam Dra UKIRT98 0.9455 -1.46 0.01 9.843 9.913 4.70E-16 UKIRT Service data
gam Dra UKIRT12 1.1782 -1.48 0.01 12.432 12.414 1.90E-16 UKIRT Service data
alp Cet TCS-H 0.2600 -1.50 0.015 1.636 1.646 4.53E-13 Alonso et al. 1994
alp Cet Kn 0.0488 -1.76 0.01 2.208 2.205 1.99E-13 Selby et al. 1988
alp Cet Ln 0.1443 -1.91 0.02 3.782 3.763 3.00E-14 Selby et al. 1988
alp Cet M 0.5418 -1.55 0.025 4.748 4.766 8.85E-15 Thomas et al. 1973
gam Cru M 0.5418 -3.08 0.03 4.748 4.749 3.61E-15 Thomas et al. 1973
gam Cru N 5.1318 -3.38 0.02 10.161 10.250 2.17E-16 Thomas et al. 1973
gam Cru 11.2 2.0209 -3.45 0.02 11.144 11.146 1.77E-15 Thomas et al. 1973
mu UMa Lp 0.1443 -0.99 0.03 3.761 3.744 1.31E-14 Sinton et al. 1984
mu UMa M 0.6677 -0.62 0.05 4.758 4.751 3.73E-15 Sinton et al. 1984
mu UMa M 0.6677 -0.69 0.03 4.758 4.751 3.97E-15 Hanner et al. 1984
mu UMa [8.7] 1.1576 -0.85 0.01 8.753 8.720 4.26E-16 UKIRT Service Obs.
mu UMa [11.7] 1.2008 -1.00 0.01 11.650 11.623 1.59E-16 UKIRT Service Obs.
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References:
Strecker et al., 1979ApJS...41..501S
Alonso et al., 1994A&A...282..684A
Selby et al., 1988A&AS...74..127S
Thomas et al., 1973MNRAS.165..201T
Sinton & Tittemore, 1984AJ.....89.1366S
Hanner et al. 1984 (not communicated)
Note: UKIRT filter set represents a series of narrowband 10um passbands
provided in common to UKIRT, Univ. Minnesota, and IRTF for "silicate" work.
The "11" filter is centered near 11.7um, the "12" filter is centered
near 12.5um.
Note for gam Dra data: The "TCS" passbands are used at the Telescopio Carlos
Sanchez of the Instituto de Astrofisica de Canarias: see Alonso et al.
(1994A&A...282..684A). Selby et al. (1988A&AS...74..127S) and independent
higher precision measurements by Hammersley (1997, Paper VIII, in prep) are
available. Likewise, these TCS mags represent an independent reduction by
Hammersley of all the Tenerife broadband data on this star, originally made
by Alonso et al. (1994A&A...282..684A).
Note for gam Cru: Photometry from Thomas et al. (1973MNRAS.165..201T) was used
after applying zero point corrections based on their observed and our
predicted magnitudes for Sirius (using our absolutely calibrated Sirius
from Paper I). Dr. H. Hyland kindly provided otherwise unavailable
passbands from Thomas et al. (1973MNRAS.165..201T).
Note for mu UMa: These uncertainties in the photometry by Sinton & Tittemore
(1984AJ.....89.1366S) and Hanner et al. (1984)
incorporate uncertainties in our redefinition of their zero points as well
as the quoted errors in photometry. UKIRT Service Observations were from
Jan. 14, 1995 and photometry is reduced with respect to alp CMa, bet Gem,
and alp Hya.
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Spectral fragments and portions of these actually used in observed spectrum
("used" may include combination with other data where overlaps occur)
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Star Fragment Reference Total range Start and stop Average
wavelengths resolving
(um) (um) power
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alp Boo NIR A1 1.22- 5.70 1.22- 5.58 50
alp Boo KAO A2 3.65- 9.39 4.44- 8.99 150
alp Boo 8-13 A3 7.65-13.43 7.65-13.43 55
alp Boo LRS A4 7.80-22.70 9.30-21.90 30
alp Boo LONG A5 15.73-23.85 15.73-23.85 73
alp Boo VLONG A6 1.25-35.00 21.80-35.00 --
gam Dra NIR A1 1.24- 5.50 1.24- 5.50 50
gam Dra NIR B1a 1.46- 2.43 1.46- 2.43 100
gam Dra KAO B1b 2.92- 5.38 2.92- 5.38 160
gam Dra KAO B2 4.74- 9.37 4.92- 8.99 180
gam Dra 8-13 B3a 7.34-13.18 7.83-13.18 55
gam Dra 8-13 B3b 7.87-13.14 7.83-13.14 55
gam Dra LRS B4 7.67-22.74 7.67-18.44 30
gam Dra LONG B5 1.22-35.00 18.50-35.00 --
alp Cet NIR A1 1.26- 5.46 1.26- 5.46 50
alp Cet KAO C2a 3.93- 5.26 3.93- 5.04 50
alp Cet KAO C2b 5.20- 7.90 5.20- 7.90 50
alp Cet KAO C2c 7.66-10.31 7.66-10.20 50
alp Cet KAO C3 5.31- 7.83 5.31- 7.83 150
alp Cet 813 C4 7.53-13.21 7.53-13.09 55
alp Cet LRS C5 7.67-22.74 7.67-13.49 30
alp Cet LONG C6 15.60-23.42 15.97-23.28 78
alp Cet LONG C7 1.25-35.00 11.18-35.00 --
gam Cru KAO-NIR D1 3.95- 5.36 3.95- 5.20 60
gam Cru KAO D2 5.22- 8.08 5.22- 8.08 60
gam Cru LRS D3 7.67-22.74 8.23-17.50 30
gam Cru LONG D4 16.27-35.02 16.27-35.02 30:
gam Cru VLONG D5 10.00-35.00 20.30-35.00 --
mu UMa NIR E1a 3.37- 5.30 3.37- 5.30 50
mu UMa NIR E1b 3.11- 5.40 3.11- 5.40 120
mu UMa KAO E2a 4.79 -8.75 4.79- 8.75 50
mu UMa KAO E2b 4.92 -9.38 4.92- 9.38 150
mu UMa KAO E2c 4.94 -9.35 4.94- 9.35 150
mu UMa 8-13 E3 7.59-13.37 7.59-13.37 55
mu UMA LRS E4 7.67-22.74 7.67-14.90 30
mu UMA VLONG E5 1.25-35.00 11.00-35.00 --
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Note for gam Dra: Because of the complete absence of, and the impossibility of
securing from the Kuiper Airborne Observatory, a complete 1.2-5.5um spectrum
of gam Dra, portions of the complete SEW shape of alp Tau's spectrum were
inserted between our newly measured short wave segments. Both alp Tau and
gam Dra have spectral type K5III, and the shapes of the new short wavelength
fragments of gam Dra closely match the shape of the SEW alp Tau spectrum
wherever they overlap. Portions substituted were confined to two regions
opaque from the ground and shortward of our new KAO observations, namely
from 1.76-2.02um and from 2.43-2.92um.
Note for alp Cet: The SEW data for alp Cet have an unobserved region from
2.42-2.90um. We substituted this portion from the SEW spectrum for bet And
which locally matches that of alp Cet very well.
References:
A1: Strecker, Erickson, and Witteborn 1979, Ap.J. Suppl., 41, 501.
For alp Tau, rescaled by 0.234 and inserted between fragments NIR-1a
and NIR-1b below.
For alp Cet, with 2.42-2.90um from bet And.
B1a: Measurements with a CVF on the 1.5m TCS by Hammersley Dec. 3, 1994,
from [gam Dra/alp Lyr].
B1b: HIFOGS data of May 5, 1995 KAO flight for [gam Dra/alp Boo].
D1: FOGS data from KAO flight of April 11, 1988 [gamma Cru/alpha Hya].
E1a: KAO flight of Jan. 18, 1991 [mu UMa/alp CMa] with the Ames SIRAS.
E1b: HIFOGS data of May 4, 1995 KAO flight [mu UMa/alpha Boo].
A2: FOGS data of May 11, 1992 KAO flight [alpha Boo/alpha Lyr], and
HIFOGS data of April 14, 1995 KAO flight [alpha Boo/alpha Lyr].
B2: HIFOGS data of April 14 and May 5, 1995 KAO flights [gam Dra/alp Boo]
and [gam Dra/alp Lyr].
C2a,b,c: FOGS data of October 24, 1988 KAO flight in New Zealand
[alp Cet/alp CMa].
D2: FOGS data from KAO flights of April 21, 1987 and April 11, 1988 in
New Zealand [gamma Cru/alpha Hya].
E2a: KAO flight of Jan. 18, 1991 [mu UMa/alp CMa] with the Ames FOGS.
E2b,c: HIFOGS data of May 4, 1995 KAO flight [mu UMa/alpha Boo].
A3: FOGS Mt Lemmon data of Feb. 24, 1992 [alpha Boo/alpha Lyr], CGS3 UKIRT
data of May 24 and 29, 1991 [alpha Boo/beta Peg], August 12, 1995
[alpha Boo/beta Peg] and [alpha Boo/beta And]. The CGS3 spectra have
the greatest weight on this combined data set.
B3a: CGS3 UKIRT Service data of August 26, 1994 [gam Dra/alp Lyr].
B3b: CGS3 UKIRT Service data of August 31, 1994 [gam Dra/alp Lyr].
C3: FOGS data of November 2, 1988 KAO flight in New Zealand
[alp Cet/alp CMa] taken in 5 overlapping fragments: 5.21-6.27,
6.17-7.15, 6.22-7.20, 6.24-7.21, and 6.94-7.83um. Fragments 2a,b,c,3
were combined into a single spectrum by successive splices and
combinations, augmenting the errors appropriately with each process.
D3: LRS raw data extracted from the old Groningen ``LRSVAX" database
maintained at NASA-Ames, and recalibrated correctly.
E3: UKIRT CGS3 data of Feb. 9, 1993 [mu UMa/alpha CMa]
(details in Paper V, 1995MNRAS.276..715C).
A4: LRS raw data extracted from the new Groningen IRAS database and
recalibrated with ``LRSCAL" routine in ``GIPSY" package.
B4: LRSVAX version of Groningen database at NASA-Ames; spliced and
recalibrated; also directly from the new complete Groningen LRS
archive, calibrated with LRSCAL in GIPSY.
C4: CGS3 10um UKIRT Archive data of November 3, 1993 [alp Cet/bet And].
D4: Glaccum (1990, Ph. D. dissertation, University of Chicago) data from
KAO flights of April 17, 186 and November 19, 1987, with calibration
traceable to Mars (with 24 channel Goddard He-3 bolometer spectrometer)
E4: LRS raw data extracted from the NASA-Ames ``LRSVAX" database and
recalibrated correctly (cf. Paper II, 1992AJ....104.2030C).
A5: 20um UKIRT CGS3 data of May 24/25, 1991 for [alpha Boo/beta Peg].
B5: Engelke Fn. used for T=3986K and an angular diameter of 9.997mas
(Blackwell, Lynas-Gray & Petford 1991A&A...245..567B); we found the
best fitting ang. diam. to be 10.17mas. This Engelke Function was
locked to the photometrically scaled combination of 8-13 and the LRS,
by "splicing" longward of the SiO fundamental and used to replace
the observations beyond 18.65um, with an estimated uncertainty
in EFn. of 2.6%, allowing for the change in shape of the EFn. for
a temperature uncertainty of 100K.
C5: LRSVAX version of Groningen database at NASA-Ames; spliced and
recalibrated.
D5: Engelke Fn. used for T=3626K (Judge & Stencel 1991ApJ...371..357J).
Their estimated angular diameter of 41.1 mas was used as an initial
value but we rescaled this to 26.06mas. This Engelke Function was
locked to the photometrically scaled combination of 8-13 and LONG KAO
spectra by splicing and used to replace the observations beyond
20.30um. We applied an estimated uncertainty in EFn. of 3.0%, allowing
for the change in shape of the EFn. for a temperature uncertainty of
100K at this effective temperature.
E5: Engelke Fn. used for T=3735K (no value specific to this star could be
found so we adopted the generic M0III from the temperature scale by
Di Benedetto & Rabbia 1987A&A...188..114D), and our initial guess
of 8.57mas; we rescaled this to 8.32mas. This Engelke Function was
locked to the photometrically scaled combination of 8-13 and LRS
spectra by splicing and used to replace the observations beyond
14.90um. We applied an estimated uncertainty in EFn. of 2.9%, allowing
for the change in shape of the EFn. for a temperature uncertainty
of 100K at this effective temperature.
A6: Engelke Fn. used for T=4362K (see Blackwell, Lynas-Gray, and Petford
1991A&A...245..567B) and angular diameter=20.430mas; we rescaled this
to 21.12mas. This Engelke Function was locked to the photometrically
scaled combination of 8-13 and LRS spectra by splicing and used to
replace the observations beyond 21.80mum. We applied an estimated
uncertainty in EFn. of 2.4%, allowing for the change in shape of the
EFn. for a temperature uncertainty of 100K at this effective
temperature.
C6: CGS3 20um UKIRT Archive data of November 3, 1993 [alp Cet/alp CMa].
C7: Engelke Fn. used for T=3745K and an angular diameter of 12.643mas
(Blackwell, Lynas-Gray & Petford 1991A&A...245..567B); we found the
best fitting ang. diam. to be 12.655mas. This Engelke Function was
locked to the spliced combination of 8-13 and the LRS between 11.18
and 13.42um, by splicing longward of the SiO fundamental. We used it
to replace very noisy LRS observations beyond 13.42um, and the CGS3
20um fragment in its entirety, with an estimated uncertainty in EFn.
of 2.8%, allowing for the change in shape of the EFn. for a
temperature uncertainty of +/-100K. Note that although we replaced the
CGS3 LONG fragment by the EFn., this observed 20-um spectrum matches
the EFn. very well, in both level and mean shape (see below, and text).
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Information on splices and biases incurred
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Star Process Factor Bias
determined %
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alp Boo NIR cf. photometry 1.003 0.87
alp Boo 813 cf. photometry 1.031 0.45
alp Boo LRS blue/red bias -- 0.03
alp Boo LRS splice to 813 0.950 0.02
alp Boo KAO joint splice to NIR and merged 813/LRS 0.862 0.41
alp Boo LONG splice to merged 813/LRS 1.124 0.66
alp Boo Engelke Fn. splice to combined 813/LRS/LONG 1.017 0.40
gam Dra NIR cf. photometry 0.999 0.59
gam Dra 813 cf. photometry 1.100 0.56
gam Dra LRS blue/red bias ..... 0.06
gam Dra LRS splice to 813 1.010 0.05
gam Dra KAO joint splice to NIR and merged 813/LRS 0.940 0.19
gam Dra Engelke Fn. splice to combined 813/LRS 1.035 0.54
alp Cet NIR cf. photometry 0.985 0.85
alp Cet KAO splice to NIR 0.983 0.20
alp Cet 813 splice to KAO 0.995 0.20
alp Cet LRS blue/red bias ..... 0.11
alp Cet LRS splice to 813 0.958 0.13
alp Cet Engelke Fn. splice to combined 813/LRS 1.020 0.27
alp Cet LONG CGS3 20um fragment comp. with scaled EFn. 1.005 0.60
gam Cru KAO-NIR cf. photometry 0.994 3.11
gam Cru LRS blue/red bias -- 0.05
gam Cru LRS cf. photometry 1.084 1.33
gam Cru KAO joint splice to NIR and LRS 0.994 1.52
gam Cru LONG splice to LRS 0.970 0.61
gam Cru Engelke Fn. splice to combined LRS and LONG 0.405 1.38
mu UMa NIR cf. photometry 0.915 2.06
mu UMa 813 cf. photometry 1.068 0.71
mu UMa LRS blue/red bias -- 0.72
mu UMa LRS splice to 813 0.955 0.22
mu UMa KAO joint splice to NIR and merged 813/LRS 1.033 0.85
mu UMa Engelke Fn. splice to combined 813/LRS 0.943 0.34
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Notes:
1. Composite spectra are NOT tabulated at equal intervals of the
wavelength, but rather at the wavelengths of the original model.
2. In most cases "total uncertainty" is the error term most appropriate
to use. It is the standard deviation of the spectral irradiance and
includes the local and global biases. Local and global biases are
given as a percent of the irradiance. The global bias does not
contribute error to flux ratios or color measurements, and may, in
those cases, be removed (in the RSS sense) from the total error.
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Origin: AAS CD-ROM series, Volume 7, 1996 Lee Brotzman [ADS] 05-Nov-1996
References:
Cohen M. et al., Paper I, 1992AJ....104.1650C
Cohen M. et al., Paper II, 1992AJ....104.2030C
Cohen M., Paper III, 1992AJ....104.2045C
Cohen M. et al., Paper IV, 1995AJ....110..275C, Cat <J/AJ/110/275>
Cohen M. and Davies J.K., Paper V, 1995MNRAS.276..715C
Cohen M. et al., Paper VI, 1996AJ....112..241C, Cat <J/AJ/112/241>
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(End) [CDS] 31-Jan-1997