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Дата изменения: Tue Jan 25 19:42:17 1994
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taken from STScI Newsletter 1992, 9, No. 2, p. 19.


UPDATES TO HST STANDARD STAR FLUXES


Ralph Bohlin and Don Lindler
Space Telescope Science Institute

Instrument Science Report on Standard Calibration Sources 001
July 1992


As part of an ongoing effort to develope a thoroughly checked and consistent
set of reference spectrophotometry from 1050 to 10000A, the composite stellar
spectra that are used for the fundamental flux standards for HST calibrations
have been updated. See Appendix B of the HST Cycle 1 Calibration Plan, version
1.0 of 1990 May for additional documentation. These data are in an STScI data
base named CRCALSPEC and have been divided into two categories to help the user
understand the origin and accuracy of these flux distributions.

The Category 1 HST standard star flux tables listed below were redelivered on
June 24, 1992. Standard stars are classified as Category 1, if both IUE (Bohlin
et al. 1990, ApJ Suppl, 73, 413) and Oke (1990, AJ, 99, 1621) spectra are
available. Oke (1990) used the Double Spectrograph on the 5 m Hale Telescope to
obtain these spectra for HST calibration; and these data are identified in the
HST data bases by the keyword OBSMODE=OKE DBSP. Also listed are the Category 2
flux tables, some of which were last updated in August, 1991. Category 2
standard stars do not have Oke DBSP data and should not be used for HST
calibrations longward of the IUE cutoff.

Three additional flux tables, installed into the ST ScI CRCALSPEC data base in
August 1989, are 10-LAC_001.TAB, ETA-AUR_001.TAB, and LAM-LEP_001.TAB. These
three stars are not HST flux standards and their pedigree is unknown.


-----------------------------------
| Category 1 Standard Star Tables |
-----------------------------------

Summary of changes for the June 24, 1992 delivery:

1) Replace any Oke Literature, Stone, or Model data with the available Oke DBSP
data between 3200 and 8800 Angstroms.

2) Oke DBSP flux values are decreased by 0.04 magnitude units.
(note: HZ44 already had the adjustment since 1990 Mar 7.)

3) The long wavelength cutoff for Oke has been increased to 8800 Angstroms
in all cases. We chose 8800 Angstroms to retain the the data for the
Paschen jump at 8200 Angstroms and to avoid the second order contamination
reported by Oke above 8800 Angstroms.

4) Statistical errors less than 0.0005 magnitude units were rounded to
0.0 on the tape delivered by Oke and were propagated as NULL into CRCALSPEC.
These 0.0 values are changed to 0.0005 magnitudes, while interpolated
data are distinguished as NULL statistical errors.




5) In the following wavelength regions, Oke (1990) has supplied interpolated
data.

5150 - 5210 Angstroms
6846 - 6950
7550 - 7690

The statistical errors for the interpolated regions are set to NULL:
The interpolated regions can be distinquished from model data, which
have both the statistical error and the FWHM set to NULL.

6) All wavelengths above 2000 Angstroms are converted from air to
vacuum.

7) All model data are extracted from the previous CALSPEC data set for
each star. Scale factors are applied to the model data above 8800A
to make the average flux in the model equal to the average
flux observed by Oke in the 8500-8800A wavelength region.

8) Scale factors applied to the VOYAGER data are the same as
in the previous delivery of Aug 1, 1991 and match the VOYAGER
to the IUE flux levels.

9) The new CALSPEC data sets have flux units of FLAM in erg s^-1 cm^-2 A^-1
instead of STMAG.

The following table gives the source of the data for each wavelength region of
the new CALSPEC data sets. The wavelength ranges are for the source data set
and are given in air above 2000 A. MODEL data were computed by the model
atmosphere program XCAL by Keith Horne.

---------------- ----- ------- ------
Wavelength Range SCALE OBSMODE SOURCE
---------------- ----- ------- ------

AGK+81D266_003.TAB
970.0 1155.0 0.9200 VOYAGER2 CALOBS:AGK_81D266_003.TAB
1155.0 3200.0 1.0 IUE CALOBS:AGK_81D266_005.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:AGK_81D266_006.TAB
8800.0 12000.0 0.9386 MODEL CALSPEC:AGK_81D266_002.TAB

BD+28D4211_003.TAB
970.0 1155.0 0.9600 VOYAGER2 CALOBS:BD_28D4211_007.TAB
1155.0 3200.0 1.0 IUE CALOBS:BD_28D4211_012.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:BD_28D4211_017.TAB
8800.0 12000.0 0.9879 MODEL CALSPEC:BD_28D4211_002.TAB

BD+33D2642_002.TAB
970.0 1155.0 1.0 MODEL CALSPEC:BD_33D2642_001.TAB
1155.0 3200.0 1.0 IUE CALOBS:BD_33D2642_008.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:BD_33D2642_012.TAB
8800.0 12000.0 0.9769 MODEL CALSPEC:BD_33D2642_001.TAB



BD+75D325_003.TAB
970.0 1155.0 0.8000 VOYAGER2 CALOBS:BD_75D325_004.TAB
1155.0 3200.0 1.0 IUE CALOBS:BD_75D325_006.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:BD_75D325_007.TAB
8800.0 12000.0 0.9497 MODEL CALSPEC:BD_75D325_002.TAB

FEIGE110_003.TAB
970.0 1155.0 1.0 VOYAGER2 CALOBS:FEIGE110_016.TAB
1155.0 3200.0 1.0 IUE CALOBS:FEIGE110_012.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:FEIGE110_015.TAB
8800.0 12000.0 0.9535 MODEL CALSPEC:FEIGE110_002.TAB

FEIGE34_003.TAB
970.0 1155.0 1.0 VOYAGER2 CALOBS:FEIGE34_016.TAB
1155.0 3200.0 1.0 IUE CALOBS:FEIGE34_013.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:FEIGE34_015.TAB
8800.0 12000.0 1.0224 MODEL CALSPEC:FEIGE34_002.TAB

G191B2B_003.TAB
970.0 1155.0 0.8900 VOYAGER2 CALOBS:G191B2B_011.TAB
1155.0 3200.0 1.0 IUE CALOBS:G191B2B_014.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:G191B2B_015.TAB
8800.0 12000.0 0.9761 MODEL CALSPEC:G191B2B_002.TAB

G93-48_002.TAB
970.0 1155.0 1.0 MODEL CALSPEC:G93-48_001.TAB
1155.0 1190.0 1.0 IUE CALOBS:G93-48_003.TAB
1190.0 1230.0 1.0 MODEL CALSPEC:G93-48_001.TAB
1230.0 3200.0 1.0 IUE CALOBS:G93-48_003.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:G93-48_005.TAB
8800.0 12000.0 1.0377 MODEL CALSPEC:G93-48_001.TAB

GD108_003.TAB
970.0 1155.0 1.0 MODEL CALSPEC:GD108_002.TAB
1155.0 3200.0 1.0 IUE CALOBS:GD108_007.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:GD108_008.TAB
8800.0 12000.0 0.9777 MODEL CALSPEC:GD108_002.TAB

GD50_002.TAB
970.0 1155.0 1.0 MODEL CALSPEC:GD50_001.TAB
1155.0 3200.0 1.0 IUE CALOBS:GD50_008.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:GD50_009.TAB
8800.0 12000.0 1.0176 MODEL CALSPEC:GD50_001.TAB

GRW+70D5824_003.TAB
970.0 1175.0 1.0 MODEL CALSPEC:GRW_70D5824_002.TAB
1175.0 1190.0 1.0 IUE CALOBS:GRW_70D5824_006.TAB
1190.0 1230.0 1.0 MODEL CALSPEC:GRW_70D5824_002.TAB
1230.0 3200.0 1.0 IUE CALOBS:GRW_70D5824_006.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:GRW_70D5824_008.TAB
8800.0 12000.0 1.1015 MODEL CALSPEC:GRW_70D5824_002.TAB

HD93521_003.TAB
970.0 1135.0 1.0 VOYAGER2 CALOBS:HD93521_006.TAB
1155.0 3200.0 1.0 IUE CALOBS:HD93521_008.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:HD93521_010.TAB
8800.0 12000.0 1.0023 MODEL CALSPEC:HD93521_002.TAB

HZ21_003.TAB
970.0 1155.0 1.0 MODEL CALSPEC:HZ21_002.TAB
1155.0 3200.0 1.0 IUE CALOBS:HZ21_009.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:HZ21_011.TAB
8800.0 12000.0 0.9859 MODEL CALSPEC:HZ21_002.TAB




HZ2_003.TAB
970.0 1155.0 1.0 MODEL CALSPEC:HZ2_002.TAB
1155.0 1200.0 1.0 IUE CALOBS:HZ2_009.TAB
1200.0 1225.0 1.0 MODEL CALSPEC:HZ2_002.TAB
1225.0 3200.0 1.0 IUE CALOBS:HZ2_009.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:HZ2_010.TAB
8800.0 12000.0 1.2787 MODEL CALSPEC:HZ2_002.TAB

HZ44_003.TAB
970.0 1155.0 1.0 VOYAGER2 CALOBS:HZ44_010.TAB
1155.0 3200.0 1.0 IUE CALOBS:HZ44_012.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:HZ44_014.TAB
8800.0 12000.0 0.9724 MODEL CALSPEC:HZ44_002.TAB

HZ4_002.TAB
970.0 1300.0 1.0 MODEL CALSPEC:HZ4_001.TAB
1300.0 3200.0 1.0 IUE CALOBS:HZ4_013.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:HZ4_015.TAB
8800.0 12000.0 1.0054 MODEL CALSPEC:HZ4_001.TAB

LB227_002.TAB
970.0 1250.0 1.0 MODEL CALSPEC:LB227_001.TAB
1250.0 3200.0 1.0 IUE CALOBS:LB227_003.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:LB227_004.TAB
8800.0 12000.0 1.0478 MODEL CALSPEC:LB227_001.TAB

LDS749B_003.TAB
970.0 1249.0 1.0 MODEL CALSPEC:LDS749B_002.TAB
1250.0 3200.0 1.0 IUE CALOBS:LDS749B_003.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:LDS749B_007.TAB
8800.0 12000.0 1.1061 MODEL CALSPEC:LDS749B_002.TAB

NGC7293_003.TAB
970.0 1155.0 1.0 VOYAGER2 CALOBS:NGC7293_002.TAB
1155.0 3200.0 1.0 IUE CALOBS:NGC7293_004.TAB
3200.0 8800.0 1.0 Oke DBSP CALOBS:NGC7293_006.TAB
8800.0 12000.0 0.9446 MODEL CALSPEC:NGC7293_002.TAB

The CALSPEC and CALOBS data sets are located in the following directories on
the STScI science cluster:

CALSPEC: DISK$REFERENCE:[CDBSDATA.REFER.CALSPEC]
CALOBS: DISK$REFERENCE:[CDBSDATA.REFER.CALOBS]


-----------------------------------
| Category 2 Standard Star Tables |
-----------------------------------

Category 2 flux tables are not recommended for HST calibration longward of the
IUE limit. Some of these tables were redelivered on Aug 1, 1991 to:

1) Replace model data with VOYAGER2 data shortward of 1155 Angstroms.

2) Scale the VOYAGER2 or Model data to improve the match with IUE.

3) Adjust the short wavelength IUE wavelength cutoff.

4) Replace OAO-2 data in ZETA-CAS with IUE data.




Category 2 flux tables are listed below along with their installation dates.

---------------- ----- ------- ------
Wavelength Range SCALE OBSMODE SOURCE
---------------- ----- ------- ------

ALPHA-LYR_001.TAB 4-Oct-1989
500.0 1170.0 1.0 MODEL
1170.0 3100.0 1.0 IUE CALOBS:ALPHA-LYR_010.TAB
3100.0 12000.0 1.0 MODEL

BPM16274_001.TAB 2-Aug-1989
500.0 1160.0 1.0 MODEL
1160.0 1200.0 1.0 IUE CALOBS:BPM16274_002.TAB
1200.0 1225.0 1.0 MODEL
1225.0 3150.0 1.0 IUE CALOBS:BPM16274_002.TAB
3150.0 12000.0 1.0 MODEL

ETA_UMA_002.TAB 1-Aug-1991
925.0 1155.0 0.9000 VOYAGER2 CALOBS:ETA-UMA_011.TAB
1155.0 3200.0 1.0 IUE CALOBS:ETA-UMA_012.TAB
3200.0 12000.0 1.0 MODEL

GAMMA-UMA_001.TAB 2-Aug-1989
500.0 1200.0 1.0 MODEL
1200.0 3200.0 1.0 IUE CALOBS:GAMMA-UMA_003.TAB
3200.0 12000.0 1.0 MODEL

HD49798_002.TAB 1-Aug-1991
900.0 1155.0 1.0 VOYAGER2 CALOBS:HD49798_004.TAB
1155.0 3200.0 1.0 IUE CALOBS:HD49798_003.TAB
3200.0 12000.0 1.0 MODEL

HD60753_002.TAB 1-Aug-1991
500.0 1155.0 1.3400 MODEL CALSPEC:HD60753_001.TAB
1155.0 3200.0 1.0 IUE CALOBS:HD60753_002.TAB
3200.0 12000.0 1.0 MODEL

MU-COL_002.TAB 1-Aug-1991
900.0 1155.0 1.0 VOYAGER2 CALOBS:MU-COL_003.TAB
1155.0 3100.0 1.0 IUE CALOBS:MU-COL_004.TAB
3100.0 12000.0 1.0 MODEL

ZETA_CAS_002.TAB 1-Aug-1991
925.0 1155.0 1.0 VOYAGER2 CALOBS:ZETA-CAS_005.TAB
1155.0 3200.0 1.0 IUE CALOBS:ZETA-CAS_001.TAB
3200.0 4000.0 1.0 MODEL
4000.0 6500.0 1.0 STONE CALOBS:ZETA-CAS_006.TAB
6500.0 12000.0 1.0 MODEL


FUTURE WORK

Without the complications of an intervening atmosphere, more accurate relative
spectrophotometry should be possible with FOS than has been previously achieved
over the wavelength range 1150-8500A. Therefore, a possible Category 3 of
reference spectrophotometry could be created from HST observations of standard
stars after the absolute calibration of FOS is fully characterized.
Furthermore, the time may be ripe to include the adjustment of the IUE absolute
scale to the white dwarf flux standard, as proposed by D. Finley and others.