http://www.stsci.edu/hst/observatory/cdbs/calspec.html CALSPEC: CALSPEC contains the composite stellar spectra that are the fundamental flux standards for HST calibrations. All files are in machine independent binary FITS table format. Information about the pedigree of a given spectrum is in the header of the FITS table file, which can be read with the IRAF hedit task or by mrdfits.pro in IDL. The Table below summarizes the set of recommended standard star spectra. Columns 2-4 give the spectral type, V, and B magnitudes of the stars. More documentation on some of these stars, eg. coordinates, finding charts and spectral types can be found in Turnshek et al. (1990), Bohlin, Colina & Finley (1995), and Colina & Bohlin (1997). Column 5 is the computer compatible file name with the plus and minus signs converted to underscores. Thus, the actual CALSPEC file name is the prefix in column 5, plus one of the suffixes in columns 6-9, plus ".fits". For example, a standard that has STIS data is "bd_28d4211_stis_001.fits". The pure hydrogen WD model LTE spectra of Bohlin (2000) are now Hubeny NLTE models calculated with his Tlusty code (Bohlin 2003). These fundamental primary standards GD71, GD153, and G191B2B are listed by Calibration Data Base System (CDBS) suffix in column 6 of the Table and provide the basis for the secondary flux standards. The observational spectra from columns 7-9 can be compared with the models; and in the case of G191B2B, there is ultraviolet line blanketing at the ~1 percent level. The model calculations extend to 30 microns and cover the long wavelength limits of 2.7 microns for NICMOS, 1.1 microns for STIS and ACS, and 27 microns for JWST. Vega was observed by STIS (Bohlin & Gilliland 2004a) and revised by Bohlin(2007). The new composite flux standard alpha_lyr_stis_003.fits consists of IUE data from 1256-1675A, STIS CCD fluxes from 1675-5300A, and a specially tailored Kurucz 9400K model longward of 5300A (Kurucz 2005). From 900-1256A, the hotter Kurucz (2003) 9550K model is more continuous with the IUE flux. The STIS and ACS observations of the SDSS standard BD+17d4708 are documented in Bohlin & Gilliland (2004b) and are now extended to 2.5microns with NICMOS data. Column 7 lists the CDBS suffix names for the second choice standard stars with STIS data from Bohlin, Dickinson, & Calzetti (2001) and NICMOS fluxes per Bohlin (2007). The naming convention in column 7 is _STIS_ for STIS only, _NIC_ for NICMOS only, and _STISNIC_ for stars with both types of spectrophotometry. Tabulated in column 8 are the next best standard star flux distributions, which are composed of FOS spectra in the UV and Oke spectra at the longer wavelengths. Also appearing in column 8 are the three solar analogs that are comprised of FOS observation but do not have "_FOS" in the CALSPEC file name. The names for the last set of standard stars appear in column 9 of the Table. The application of corrections to the original IUE and optical fluxes produces a consistent set of spectrophotometric standards from 1150 to 9200A (Bohlin 1996 and references therein). This set of standards is composed of IUE+Oke data only. CALSPEC also contains the ultraviolet to near-infrared absolute flux distribution of the Sun (filename: sun_reference_stis_001.fits) to 2.7 microns. The solar reference spectrum combines absolute flux measurements from satellites and from the ground with a model spectrum for the near-infrared (Colina, Bohlin, & Castelli 1996). The newer absolute solar flux measurements of Thuillier (2003) may be a better choice for a solar reference spectrum from 1990-23975A. The order of preference for the choice of a standard flux distribution is from left to right in the Table, i.e. from the best in column 6 to the last choice with the lowest quality in column 9. CDBS Files of the Flux Standards with Columns in Order of Preference(1) ---------------------------------------------------------------------------------------- Star name Sp. T. V B-V CDBS name Model STIS FOS+Oke IUE+Oke (1) (2) (3) (4) (5) (6) (7) (8) (9) 1740346 A5V 12.36 ... 1740346 _NIC_001 1743045 A5V 13.13 ... 1743045 _NIC_001 1805292 A1V 12.06 ... 1805292 _NIC_001 1812095 A3V 11.8 ... 1812095 _NIC_001 2M0036+18 L3.5 21.34 ... 2M003618 _STISNIC_001 2M0559-14 T5 I=19.14 2M0559-14 _STISNIC_001 AGK+81D266 sdO 11.94 -0.34 AGK_81D266 _STIS_001 _005 ALPHA-LYR A0V 0.03 0.00 ALPHA_LYR _STIS_003 _004 BD+17D4708 sdF8 9.47 0.44 BD_17D4708 _STISNIC_001 BD+25D4655 ? 9.69 -0.31 BD_25D4655 _002 BD+28D4211(2) Op 10.51 -0.34 BD_28D4211 _STIS_001 _FOS_003 _005 BD+33D2642 B2IV 10.83 -0.17 BD_33D2642 _FOS_003 _004 BD+75D325 O5p 9.55 -0.33 BD_75D325 _STIS_001 _FOS_003 _005 C26202 G 16.64 ... C26202 _STISNIC_001 FEIGE110 D0p 11.83 -0.30 FEIGE110 _STIS_001 _005 FEIGE34 DO 11.18 -0.34 FEIGE34 _STIS_001 _005 FEIGE66 sdO 10.51 -0.29 FEIGE66 _002 FEIGE67 sdO 11.82 -0.34 FEIGE67 _002 G191B2B DA0 11.781 -0.33 G191B2B _MOD_004 _STISNIC_001 _FOS_003 _005 G93-48 DA3 12.74 -0.01 G93_48 _004 GD108 sdB? 13.56 -0.22 GD108 _005 GD153 DA1 13.346 -0.29 GD153 _MOD_004 _STISNIC_001 _FOS_003 GD50 DA2 14.06 -0.28 GD50 _004 GD71 DA1 13.032 -0.25 GD71 _MOD_005 _STISNIC_001 _FOS_003 GRW+70D5824 DA3 12.77 -0.09 GRW_70D5824 _STIS_001 _005 HD93521 O9Vp 6.99 -0.27 HD93521 _STIS_001 _005 HZ2 DA3 13.88 -0.09 HZ2 _005 HZ21 DO2 14.69 -0.33 HZ21 _STIS_001 _005 HZ4 DA4 14.51 +0.09 HZ4 _STIS_001 _004 HZ43 (3) DA 12.91 -0.31 HZ43 _MOD_004 _STIS_001 _FOS_003 HZ43B (3) M 14.30 ... HZ43B _STIS_001 HZ44 sdO 11.67 -0.29 HZ44 _STIS_001 _FOS_003 _005 KF01T5 K1III 13.56 ... KF01T5 _NIC_001 KF06T1 K1.5III 13.52 ... KF06T1 _NIC_001 KF06T2 K1.5III 13.8 ... KF06T2 _NIC_001 KF08T3 K0.5III 13.5 ... KF08T3 _NIC_001 LB227 DA4 15.32 +0.06 LB227 _004 LDS749B DBQ4 14.674 -0.04 LDS749B _MOD_001 _STIS_001 _005 LTT9491 DC 14.10 +0.03 LTT9491 _002 NGC7293 ... 13.53 -0.37 NGC7293 _005 P041C GOV 12.00 0.62 P041C _STISNIC_001 _001 P177D G0V 13.47 0.66 P177D _STISNIC_001 _001 P330E G0V 13.00 0.64 P330E _STISNIC_001 _001 SF1615+001A G 16.753 +0.66 SF1615001A _STISNIC_001 SNAP-1 WD 15.6 ... SNAP-1 _STISNIC_001 SNAP-2 G 16.2 ... SNAP-2 _STISNIC_001 VB8 M7 16.81 ... VB8 _STISNIC_001 WD1057+719 DA1.2 14.8 ... WD1057_719 _STISNIC_001 WD1657+343 DA1 16.1 ... WD1657_343 _STISNIC_001 SUN G2V -26.75 0.63 SUN_REFERENCE _STIS_001 (1) The unit of flux in all files is erg s-1 cm-2 A-1. (2) BD+28 4211 has a companion at 2.8arcsec (Landolt & Uomoto, 2007). (3) HZ43 and HZ3B are separated by ~3arcsec (Bohlin, Dickinson, & Calzetti 2001). SUPPLEMENTAL CALSPEC contains previous CALSPEC versions and spectrophotometry that may be useful for special purposes. UPDATES: 96feb22, 99jul19, 01Jun5, 04Feb27, 06Sep1, 07Oct-LDS749B REFERENCES Bohlin, R.C. 1996, AJ, 111, 1743 Bohlin, R.C. 2000, AJ, 120, 437 Bohlin, R. 2003, 2002 HST Calibration Workshop, ed. S. Arribas, A. Koekemoer, & B. Whitmore, (Baltimore:STScI), p. 115 Bohlin, R. C. 2007, in The Future of Photometric, Spectrophotometric, and Polarimetric Standardization, ASP Conf. Series, Vol. 364, p. 315 ed. C. Sterken; also Astro-Ph 0608715 Bohlin, R. C., & Gilliland, R. L. 2004a, AJ, 127, 3508 Bohlin, R. C., & Gilliland, R. L. 2004b, AJ, 128, 3053 Bohlin, R.C., Colina, L., & Finley, D.S. 1995, AJ, 110, 1316 Bohlin, R. C., Dickinson, M. E., & Calzetti, D. 2001, AJ, 122, 2118 Bohlin, R. C., & Koester, D. 2008, AJ, submitted, The Absolute Flux Distribution of LDS749B Colina, L., & Bohlin, R. 1994, AJ, 108, 1931 Colina, L., & Bohlin, R. 1997, AJ, 113, 1138 Colina, L., Bohlin, R.C., & Castelli, F. 1996, AJ, 112, 307 Kurucz, R. 2003, http://kurucz.harvard.edu/ Kurucz, R. 2005, Vega spectrum at T=9400K, log g=3.90, [M/H]=-0.5, and zero microturbulent velocity, personal communication Landolt, A., & Uomoto, A. 2007, AJ, 133, 768 Oke, J.B. 1990, AJ, 99, 1621 Thuillier, G., Herse, M., Labs, D., Foujols, T., Peetermans, W., Gillotay, D., Simon, P., & Mandel, H. 2003, Sol. Phys., 214, 1 Turnshek, D.A., Bohlin, R.C., Williamson, R., Lupie, O., Koornneef, J., & Morgan D. 1990, AJ, 99, 1243 --------------------------- Last modified, October 2007