Content

 

Access to the latest CALSPEC files

CALSPEC contains the composite stellar spectra that are flux standards on the HST system. 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 file, which can be read with the IRAF hedit task, by mrdfits.pro in IDL, or with the Python astropy.io.fits package. Table 1 below summarizes this set of standard star spectra. Columns 2-4 give the spectral type, V, and B-V magnitudes of the stars. Column 5 is the computer compatible file name with the plus and minus signs converted to underscores or omitted. Thus, the actual CALSPEC file name is the prefix in column 5, plus one of the suffixes in columns 6 or 7, plus ".fits". For example, a standard that has STIS data is "bd_28d4211_stis_005.fits". The naming convention in column 7 includes STIS, NIC, and WFC to indicate some contribution from any of the three HST spectrophotometers. Column 8 has the amount of variability found by Mullally et al. (2022), including upper limits. More documentation on some of these stars, including coordinates, finding charts and spectral types are in Turnshek et al. (1990), Bohlin, Colina & Finley (1995), and Colina & Bohlin (1997). 

The BOSZ grid for main-sequence (MS) stars (Bohlin et al. 2017) provides models for each G-A type MS standard, while a separate file includes the STIS and NICMOS fluxes concatenated with a BOSZ R=500 model for the extrapolation to 32 microns (col. 7). In 2023, Szabolcs Meszaros updated his BOSZ models because of important improvements of the model atmosphere spectral synthesis codes and linelists. The original models are now replaced by updated calculations with the old R=300,000 model (col. 6) now replaced with R=200,000 resolution models that extend to a shorter wavelength limit of 500A. Starting in 2022 April, the BOSZ LTE models are replaced with R=5000 Hubeny NLTE models for stars hotter than 15,000K (Bohlin et al. 2022). Beginning in 2019, WFC3 IR grism fluxes (Bohlin & Deustua 2019) supplement the NICMOS spectral energy distributions (SEDs). Coordinates are in Table 2. The final two columns of Table 2 provide the complete long names needed for a successful Simbad search.

High-fidelity, non-BOSZ models at resolutions of less than R=200,000 are available for a few of the WD stars. The modeled IR fluxes for 13 stars are compared to Spitzer IRAC photometry in Bohlin et al. (2011). NLTE models for the three fundamental primary WD standards GD71, GD153, and G191B2B are updated by Bohlin, et al. (2020), where the pure H I models of Rauch (TMAP) are used for GD71 and GD153, while G191B2B has a Hubeny (TLUSTY) metal line-blanketed model. Wavelength dependent changes are <1% from 0.167-10 microns, and there is also a wavelength independent increase of 0.87% for all SEDs. A driving force for the 2020 update is greatly improved agreement to <1% at 0.15-30 microns between the TMAP and TLUSTY models. As a result of the changes to the primary standards, the flux calibration is revised, and all stars with STIS spectra and their models are updated as of 2020 March.

The observational spectra from column 7 can be compared with the column 6 models. The model calculations cover the long wavelength limits of 2.5 microns for NICMOS, 1.7 microns for WFC3, one micron for STIS and ACS, and ~30 microns for some JWST or Spitzer filters. The composite flux standard alpha_lyr_stis consists of a special Kurucz 9550K model from 900-1152A (Kurucz 2003), IUE data from 1152-1675A, STIS CCD fluxes from 1675-10200A (Bohlin & Gilliland 2004a), and the 9550K model longward of 10200A. The STIS and ACS observations of the SDSS standard BD+17 4708 are documented in Bohlin & Gilliland (2004b) and are extended to 2.5 microns with NICMOS data, while Bohlin & Landolt (2015) present the evidence for variability of BD+17 4708. All observed wavelengths are corrected to the heliocentric vacuum reference frame. Model wavelengths are corrected to the same vacuum heliocentric standard, if the radial velocity appears in Simbad. In summary, the files of choice for calibration of photometry and low resolution spectra are the *stis* files. For calibration of high resolution spectrometers, the R=200,000 *mod* files may be helpful.

CALSPEC also contains the ultraviolet to near-infrared absolute flux distribution of the Sun to 2.7 microns (filename: sun_reference_stis_001.fits). The solar reference spectrum combines absolute flux measurements from space and the ground with a model spectrum for the near-infrared (Colina, Bohlin, & Castelli 1996). The absolute solar flux measurements of Thuillier (2003) from 1990-23975A, the composite of Rieke et al. (2009), and the solar model from the website of R. Kurucz are additional choices for a solar reference spectrum. The Kurucz model for the Sun (sun_mod_001.fits) at a spectral resolution of R=5000 is in column 6 of Table 1b, where the model has been normalized to the SED of Thuillier (2003) at 6800-7700A.

Also in the CALSPEC data directory are a combined FUSE and STIS high resolution spectrum of G191B2B (Rauch et al. 2013) g191b2b_stisfuse_001.fits and the covariance matrix WDcovar_002.fits for the uncertainty of the HST flux system as a function of wavelength. As explained in more detail by Bohlin et al. (2014), the uncertainty is relative to the reference wavelength of 5556A (5557.5 in vacuum), where this relative uncertainty is zero and the absolute uncertainty is 0.5% (Bohlin 2014, Bohlin et al. 2020).

Table 1a: Files of the Flux1 Standards with Complete STIS Coverage

 

Star name Sp. T. V B-V Name Model STIS** Var (%)
[1] [2] [3] [4] [5] [6] [7] [8]
109 VIR A0III 3.73 -0.01 109vir _mod_003 _stis_003  
10 LAC O9V 4.88 -0.21 10lac _mod_005 _stis_007 <0.23
16 CYG B G3V 6.20 0.66 16cygb _mod_004 _stis_004 <0.21
18 SCO G2V 5.50 0.65 18sco _mod_005 _stis_005  
1732526 A4V 12.53 0.12 1732526 _mod_005 _stisnic_007 1.40
17403462 A6V 12.48 0.20 1740346   _stisnic_005  
1743045 A8III 13.52 0.28 1743045 _mod_005 _stisnic_007 <1.32
1757132 A3V 12.01 -0.10 1757132 _mod_005 _stiswfc_004 <0.37
1802271 A2V 11.53 0.02 1802271 _mod_005 _stiswfcnic_004 <0.82
1805292 A4V 12.28 0.14 1805292 _mod_004 _stisnic_006 <0.49
1808347 A3V 11.69 0.49 1808347 _mod_005 _stiswfc_004 1.65
1812095 A3V 12.01 -0.07 1812095 _mod_004 _stisnic_006 1.57
2M0036+18 L3.5 J=12.47 ... 2m003618   _stiswfcnic_006  
2M0559-14 T4.5 J=13.80 ... 2m055914   _stiswfcnic_005  
AGK+81 266 sdO 11.95 -0.36 agk_81d266   _stisnic_007*  
ALPHA LYR A0V 0.031 0.00 alpha_lyr _mod_004 _stis_011*  
BD+02 3375 A5 9.93 0.45 bd02d3375 _mod_003 _stis_006  
BD-11 3759 M3.5V 11.32 1.60 bd11d3759   _stis_003  
BD+21 0607 F2 9.22 0.44 bd21d0607 _mod_003 _stis_006  
BD+26 2606 A5 9.73 0.39 bd26d2606 _mod_003 _stis_006  
BD+29 2091 F5 10.22 0.50 bd29d2091 _mod_003 _stis_006  
BD+54 1216 sdF6 9.71 0.48 bd54d1216 _mod_002 _stis_005  
BD+60 1753 A1V 9.65 0.07 bd60d1753 _mod_005 _stiswfc_004 <0.17
BD+17 47083 sdF8 9.47 0.44 bd_17d4708   _stisnic_007  
BD+75 325 sdO5 9.55 -0.33 bd_75d325   _stis_006*  
C26202 F8IV 16.64 0.26 c26202 _mod_006 _stiswfcnic_005  
DELTA UMI A1V 4.34 0.03 delumi _mod_004 _stis_004 0.04
ETA1 DOR A0V 5.69 -0.01 eta1dor _mod_004 _stis_004 0.18
ETA UMA B3V 1.85 -0.10 etauma _mod_004 _stis_007  
FEIGE110 sdO 11.83 -0.30 feige110   _stisnic_008*  
FEIGE34 sdO 11.14 -0.23 feige34   _stis_006*  
G191B2B DA.8 11.781 -0.33 g191b2b _mod_012 _stiswfcnic_004* <0.74
GD153 DA1.2 13.349 -0.29 gd153 _mod_012 _stiswfcnic_004 <2.44
GD71 DA1.5 13.032 -0.25 gd71 _mod_012 _stiswfcnic_004 <1.90
GJ754.1A DBQA5 12.29 0.05 gj7541a _mod_001 _stis_004  
GRW+70 5824 DA2.4 12.60 -0.06 grw_70d5824 _mod_001 _stiswfcnic_003  
HD009051 G7III 8.92 0.81 hd009051 _mod_004 _stis_007  
HD031128 F4V 9.14 0.41 hd031128 _mod_003 _stis_006  
HD074000 sdF6 9.66 0.45 hd074000 _mod_003 _stis_006  
HD101452 A2/3 8.20 -0.36 hd101452 _mod_003 _stis_003 <0.09
HD106252 G0 7.36 0.64 hd106252 _mod_006 _stis_008  
HD111980 F7V 8.38 0.53 hd111980 _mod_003 _stis_006  
HD115169 G3V 9.20 0.69 hd115169 _mod_003 _stis_003 <0.11
HD116405 A0V 8.34 -0.07 hd116405 _mod_004 _stis_006 <0.10
HD128998 A1V 5.83 0.00 hd128998 _mod_003 _stis_003 0.05
HD142331 G5V 8.75 0.64 hd142331 _mod_005 _stis_005  
HD14943 A5V 5.91 0.19 hd14943 _mod_003 _stis_005 0.05
HD158485 A4V 6.50 0.13 hd158485 _mod_003 _stis_005 0.42
HD159222 G1V 6.56 0.65 hd159222 _mod_006 _stis_008  
HD160617 F 8.73 0.45 hd160617 _mod_002 _stis_005  
HD163466 A6V 6.85 0.19 hd163466 _mod_003 _stis_005 0.17
HD1654595 A4V 6.86 0.13 hd165459 _mod_004 _stisnic_006  
HD167060 G3V 8.92 0.64 hd167060 _mod_005 _stis_005 <0.09
HD172728 A0V 5.74 -0.05 hd172728 ._mod_002 _stis_002    
HD180609 A0V 9.42 0.15 hd180609 _mod_004 _stis_006 <0.13
HD185975 G3V 8.10 0.68 hd185975 _mod_004 _stis_007  
HD200654 G 9.11 0.63 hd200654 _mod_004 _stis_007  
HD200775 B2Ve 7.43 0.33 hd200775 ._stis_001    
HD205905 G2V 6.74 0.62 hd205905 _mod_007 _stis_009 0.26
HD2094586 G0V 7.65 0.59 hd209458 _mod_003 _stisnic_008  
HD2811 A3V 7.50 0.17 hd2811 _mod_004 _stis_004  
HD37725 A3V 8.31 -0.19 hd37725 _mod_005 _stiswfc_004 0.13
HD37962 G2V 7.85 0.65 hd37962 _mod_008 _stis_010 <0.09
HD38949 G1V 7.80 0.57 hd38949 _mod_005 _stis_007 1.17
HD55677 A4V 9.41 0.06 hd55677 _mod_004 _stis_004 0.24
HD607537 B3IV 6.68 -0.09 hd60753   _stis_004  
HD93521 O9Vp 6.99 -0.27 hd93521 _mod_003 _stis_007*  
HS2027+0651 DO 16.9 ... hs2027   _stis_006  
HZ21 DO2 14.69 -0.33 hz21   _stis_007  
HZ438 DA 12.91 -0.31 hz43   _stis_005*  
HZ43B8 M3Ve 14.30 ... hz43b   _stis_005  
HZ44 sdB 11.65 -0.23 hz44   _stis_006*  
HZ4 DA3.4 14.51 0.09 hz4   _stis_008  
KF06T2 K1.5III 13.80 1.30 kf06t2 _mod_006 _stiswfcnic_005  
KF08T3 K0.5III 13.18 1.21 kf08t3 _mod_005 _stisnic_004  
KSI2 CETI B9III 4.28 -0.04 ksi2ceti _mod_004 _stis_006  
LAMBDA LEP B0.5V 4.29 -0.25 lamlep _mod_005 _stis_007 0.35
LDS749B DBQ4 14.674 -0.04 lds749b _mod_007 _stisnic_008  
MU COL O9.5V 5.18 -0.28 mucol _mod_005 _stis_007 0.12
NGC2506-G31 G1V 17.9 0.7 ngc2506g31 _mod_003 _stis_003  
NGC6681-1 ... 15.77 0.18 NGC6681_1   _stis_002  
NGC6681-2 ... 16.20 0.05 NGC6681_2   _stis_002  
NGC6681-3 ... 16.90 0.03 NGC6681_3   _stis_002  
NGC6681-4 ... 16.14 0.04 NGC6681_4   _stis_002  
NGC6681-5 ... 16.37 0.03 NGC6681_5   _stis_002  
NGC6681-6 ... 16.20 0.04 NGC6681_6   _stis_002  
NGC6681-7 ... 16.05 1.24 NGC6681_7   _stis_002  
NGC6681-8 ... 17.01 -0.01 NGC6681_8   _stis_002  
NGC6681-9 ... 15.80 0.18 NGC6681_9   _stis_002  
NGC6681-10 ... 19.14 -0.14 NGC6681_10   _stis_002  
NGC6681-11 ... 15.65 0.22 NGC6681_11   _stis_002  
NGC6681-12 ... 17.62 -0.08 NGC6681_12   _stis_002  
P041C9 GOV 12.16 0.68 p041c _mod_004 _stisnic_009* <0.44
P177D G0V 13.49 0.60 p177d _mod_005 _stisnic_010* <1.00
P330E G2V 12.92 0.64 p330e _mod_007 _stiswfcnic_006* <0.76
SDSS132811 DA g=17.01 ... sdss132811   _stis_004  
SDSSJ151421 DA1.8 16.5 0.89 sdss151421 _mod_004 _stis_005  
SF1615+001A G 16.75 0.49 sf1615_001a _mod_005 _stisnic_010  
SIGMA ORI O9.5V+B0.2V 3.79 -0.21 sigori   _stis_001  
SIRIUS A1V -1.46 0.00 sirius _mod_005 _stis_005*  
SNAP-2 G0-5 16.23 0.86 snap2 _mod_006 _stiswfcnic_005  
VB8 M7V 16.92 1.8 vb8   _stiswfcnic_004  
WD0148+467 DA3.6 12.46 0.06 wd0148_467   _stiswfc_001  
WD0227+050 DA2.5 12.80 -0.05 wd0227_050   _stiswfc_002  
WD0308-565 sdB 14.07 -0.11 wd0308_565 _mod_007 _stis_009  
WD0809+177 DA 13.46   wd0809_177   _stiswfc_002  
WD1057+719 DA1.2 14.68 ... wd1057_719 _mod_009 _stisnic_011 <6.05
WD1105-048 DA3 13.06 0.04 wd1105_048   _stiswfc_002  
WD1105-340 DA3.6 13.63 0.16 wd1105_340   _stiswfc_002  
WD1202-232 DA5.7 12.90 0.14 wd1202_232   _stiswfc_002  
WD1327-083 DA3.5 12.34 0.06 wd1327_083   _stiswfc_004  
WD1544-377 DA4.8 12.80 0.30 wd1544_377   _stiswfc_002  
WD1657+343 DA.9 16.1 ... wd1657_343 _mod_009 _stiswfcnic_006 <37.88
WD1713+695 DA3.2 13.20 ~0.2 wd1713_695   _stiswfc_002  
WD1911+536 DA 13.26 ~-0.1 wd1911_536   _stiswfc_001  
WD1919+145 DA3.3 13.01 0.06 wd1919_145   _stiswfc_001  
WD2039-682 DA3.0 13.30 0.05 wd2039_682   _stiswfc_001  
WD2117+539 DA3.4 12.81   wd2117_539   _stiswfc_002  
WD2126+734 DA3.1 12.83 -0.03 wd2126_734   _stiswfc_002  
WD2149+021 DA2.8 12.74 -0.01 wd2149_021   _stiswfc_001  
WD2341+322 DA3.8 12.94 0.12 wd2341_322   _stiswfc_004  

 

Access to the latest CALSPEC files

Table 1b: Files of the Flux1 Standards with Incomplete STIS Coverage

Star name Sp. T. V B-V Name Model STIS**
[1] [2] [3] [4] [5] [6] [7]
1812524 A4V 12.27 0.18 1812524   _nic_005
BD+28 42114 sdO 10.51 -0.34 bd_28d4211   _stis_005*
KF01T5 K1III 13.56 ... kf01t5   _nic_004
KF06T1 K1.5III 13.52 0.98 kf06t1   _nic_004
SNAP-1 sdB 15.40 0.20 snap1   _stisnic_008
SUN G2V -26.75 0.63 sun_reference   _stis_002*
SUN G2V -26.75 0.63 sun _mod_001  
WD0320-539 DA 14.9 ... wd0320_539 _mod_001 _stis_005
WD0947+857 DA 16.4 ... wd0947_857 _mod_003 _stis_006
WD1026+453 DA 16.13 -0.04 wd1026_453 _mod_003 _stis_006
* WARNING. Some wavelength coverage from sources of lower precision, such as IUE, FOS, or Oke.
** The STIS low resolution modes cover the 1140-10200A range, the NICMOS grism coverage is 0.8-2.5 micron, 
and the two WFC3 grisms cover 0.8-1.7 micron. See the *.fits headers for the exact source ranges.

(1)  The unit of flux in all files is erg s-1 cm-2 A-1.
(2)  Dust ring (Bohlin et al, 2011). Variable at +/- 0.01 mag (Pancino et al. 2012).
(3)  BD+17 4708 is variable (Bohlin & Landolt 2015).
(4)  BD+28 4211 has a companion at 2.8arcsec (Landolt & Uomoto (2007).
(5)  Dust ring (Bohlin et al, 2011).
(6)  Transiting Planet.
(7)  No single model fits well in the sense that an unresolved cool companion would explain the problem.
(8)  HZ43 and HZ3B are separated by ~3arcsec (BDC).
(9)  P041C has an M companion 0.57arcsec away (Gilliland & Rajan 2011)

Access to the latest CALSPEC files

 

Table 2:  Coordinates, Radial Velocity (km/s), Proper Motion (PM), and Alternate Star Names

Star Name R.A. Decl. Vr PM (mas/yr) Simbad Name Alt. Simbad Name
  (2000) (2000)   R.A. Decl.    
10 LAC 22 39 15.679 +39 03 00.97 -10 -0.32 -5.46    
109 VIR 14 46 14.925 +01 53 34.38 -6.1 -114.03 -22.13 HD130109  
16 CYG B 19 41 51.973 +50 31 03.09 -27.7 -134.79 -162.49 HD186427  
18 SCO 16 15 37.270 -08 22 09.98 +11.9 232.16 -495.37 HD146233  
1732526 17 32 52.630 +71 04 43.12   0.22 -2.71 2MASS J17325264+7104431 TYC 4424-1286-1
1740346 17 40 34.679 +65 27 14.77   -5.72 -3.44 2MASS J17403468+6527148 TYC 4207-219-1
1743045 17 43 04.486 +66 55 01.66   1.10 -2.79 2MASS J17430448+6655015  
1757132 17 57 13.233 +67 03 40.77   0.41 -14.03 2MASS J17571324+6703409 TYC 4212-455-1
1802271 18 02 27.163 +60 43 35.54   5.40 2.17 2MASS J18022716+6043356 TYC 4201-1542-12
1805292 18 05 29.275 +64 27 52.13   -1.64 10.06 2MASS J18052927+6427520 TYC 4209-1396-1
1808347 18 08 34.736 +69 27 28.72   4.43 8.52 2MASS J18083474+6927286 TYC 4433-1800-1
1812095 18 12 09.567 +63 29 42.26   4.07 1.31 2MASS J18120957+6329423 TYC 4205-1677-1
1812524 18 12 52.381 +60 02 31.95   -3.03 -8.02 2MASS J18125240+6002319 TYC 4201-1717-1
2M0036+18 00 36 16.112 +18 21 10.29 +19 901.56 124.02 2MASS J00361617+1821104  
2M0559-14 05 59 19.188 -14 04 49.22   570.20 -337.59 2MASS J05591914-1404488  
AGK+81 266 09 21 19.177 +81 43 27.63   -11.26 -51.26    
ALPHA LYR 18 36 56.336 +38 47 01.28 -21 200.94 286.23 Vega HD172167
BD+02 3375 17 39 45.595 +02 24 59.61 -398 -366.01 75.12    
BD-11 3759 14 34 16.812 -12 31 10.42 -1 -355.04 593.22    
BD+17 4708 22 11 31.375 +18 05 34.16 -291 506.37 60.49    
BD+21 0607 04 14 35.516 +22 21 04.25 +340 425.99 -301.87 HD284248  
BD+26 2606 14 49 02.355 +25 42 09.14 +33 -5.88 -347.60    
BD+28 4211 21 51 11.022 +28 51 50.37   -34.73 -56.85 WD2148+286  
BD+29 2091 10 47 23.163 +28 23 55.93 +83 177.50 -824.83    
BD+54 1216 08 19 22.572 +54 05 09.63 +66 -34.20 -628.56 HD233511  
BD+60 1753 17 24 52.275 +60 25 50.75 -27.3 4.89 3.76    
BD+75 325 08 10 49.490 +74 57 57.94 -50 7.17 10.30    
C26202 03 32 32.843 -27 51 48.58       2MASS J03323287-2751483 [B2010] C26202
DELTA UMI 17 32 12.997 +86 35 11.26 -7.6 10.17 53.97 HD166205  
ETA UMA 13 47 32.438 +49 18 47.76 -13 -121.17 -14.91 HD120315  
ETA1 DOR 06 06 09.382 -66 02 22.63 +17.6 13.66 27.82 HD42525  
FEIGE110 23 19 58.400 -05 09 56.17   -10.68 0.31    
FEIGE34 10 39 36.738 +43 06 09.21 +1 12.54 -25.41 WD1036+433  
G191B2B 05 05 30.618 +52 49 51.92 +22.1 12.70 -93.42 BD+52 913 EGGR 247 WD0501+527
GD153 12 57 02.322 +22 01 52.63 +8.3 -38.40 -202.99 WD1254+223  
GD71 05 52 27.620 +15 53 13.23 +30 76.73 -172.96 WD0549+158  
GJ754.1A 19 20 34.923 -07 40 00.07   -61.28 -161.77 LAWD74 WD1917-077
GRW+70 5824 13 38 50.478 +70 17 07.64 +26 -402.08 -24.56 LAWD52 WD1337+705
HD2811 00 31 18.490 -43 36 23.00   -6.02 -4.18    
HD009051 01 28 46.503 -24 20 25.44 -72 53.56 -17.03    
HD14943 02 22 54.675 -51 05 31.66 +5 22.33 66.38 HR 701  
HD031128 04 52 09.910 -27 03 50.94 +112 164.76 -26.52    
HD37725 05 41 54.370 +29 17 50.96   15.05 -26.93    
HD37962 05 40 51.966 -31 21 03.99 +3 -59.65 -365.23    
HD38949 05 48 20.059 -24 27 49.85 +3 -30.44 -35.42    
HD55677 07 14 31.290 +13 51 36.79 -2 -2.66 -6.81    
HD60753 07 33 27.319 -50 35 03.31 +20 -3.12 5.31    
HD074000 08 40 50.804 -16 20 42.51 +206 350.82 -484.16    
HD93521 10 48 23.512 +37 34 13.09 -14 0.22 1.72    
HD101452 11 40 13.651 -39 08 47.67   -34.17 -20.98    
HD106252 12 13 29.510 +10 02 29.89 +16 22.86 -280.01    
HD111980 12 53 15.053 -18 31 20.01 +155 299.49 -796.09    
HD115169 13 15 47.388 -29 30 21.18 +21.2 -110.57 -82.09    
HD116405 13 22 45.124 +44 42 53.91 -19 8.01 -10.29    
HD128998 14 38 15.222 +54 01 24.02 -3 17.28 -18.99 HR 5467  
HD142331 15 54 19.788 -08 34 49.37 -70.8 -105.98 -23.73    
HD158485 17 26 04.837 +58 39 06.83 -30 -9.10 14.67 HR 6514  
HD159222 17 32 00.992 +34 16 16.13 -52 -240.70 63.71 HR 6538  
HD160617 17 42 49.324 -40 19 15.51 +100 -62.39 -393.23    
HD163466 17 52 25.376 +60 23 46.94 -16 -2.73 42.67    
HD165459 18 02 30.741 +58 37 38.16 -19.2 -13.06 24.61    
HD167060 18 17 44.143 -61 42 31.62 +15.2 88.52 -145.15    
HD172728 18 37 33.517 +62 31 35.67 -10.5 -8.98 49.58    
HD180609 19 12 47.200 +64 10 37.17   -3.06 -7.79    
HD185975 20 28 18.740 -87 28 19.94 -19 169.76 -56.99    
HD200654 21 06 34.751 -49 57 50.28 -45 193.94 -273.89    
HD200775 21 01 36.921 +68 09 47.79 -3.4 7.60 -2.82    
HD205905 21 39 10.151 -27 18 23.67 -17 384.10 -83.96    
HD209458 22 03 10.773 +18 53 03.55 -15 29.58 -17.89    
HS2027+0651 20 29 32.506 +07 01 07.70   9.24 1.53 WD2027+0651  
HZ21 12 13 56.264 +32 56 31.36   -100.88 30.13 WD1211+332  
HZ4 03 55 21.988 +09 47 18.13 +46 173.27 -5.51 WD0352+096  
HZ43 13 16 21.853 +29 05 55.38 +54 -157.96 -110.23 WD1314+293  
HZ43B 13 16 21.495 +29 05 53.07          
HZ44 13 23 35.263 +36 07 59.55   -66.27 -4.52 WD1321+364  
KF01T5 18 04 03.894 +66 55 43.81 -22 -0.40 0.47 2MASS J18040388+6655437 [RMC2005] KF01T5
KF06T1 17 57 58.486 +66 52 29.41 -41 -2.13 -8.70 2MASS J17575849+6652293 [RMC2005] KF06T1
KF06T2 17 58 37.995 +66 46 52.11   0.62 -4.42 2MASS J17583798+6646522 [RMC2005] KF06T2
KF08T3 17 55 16.216 +66 10 11.61 -50 2.09 -6.39 2MASS J17551622+6610116 [RMC2005] KF08T3
KSI2 CETI 02 28 09.557 +08 27 36.22 +12 23.71 -4.79    
LAMBDA LEP 05 19 34.524 -13 10 36.44 +20 -3.30 -4.91    
LDS749B 21 32 16.233 +00 15 14.40 -81 413.23 27.27 LAWD87 WD2129+000
MU COL 05 45 59.895 -32 18 23.16 +109 2.99 -22.03    
NGC2506G31 08 00 14.212 -10 47 29.47          
NGC6681-1 18 43 13.319 -32 17 25.36 +218.7        
NGC6681-2 18 43 13.165 -32 17 25.82 +218.7        
NGC6681-3 18 43 13.041 -32 17 25.41 +218.7        
NGC6681-4 18 43 12.893 -32 17 26.43 +218.7        
NGC6681-5 18 43 12.872 -32 17 26.56 +218.7        
NGC6681-6 18 43 12.755 -32 17 25.69 +218.7        
NGC6681-7 18 43 12.639 -32 17 27.09 +218.7        
NGC6681-8 18 43 12.278 -32 17 27.51 +218.7        
NGC6681-9 18 43 12.199 -32 17 27.11 +218.7        
NGC6681-10 18 43 12.146 -32 17 26.58 +218.7        
NGC6681-11 18 43 12.049 -32 17 27.52 +218.7        
NGC6681-12 18 43 11.902 -32 17 27.91 +218.7        
P041C 14 51 57.980 +71 43 17.39 -22 -49.32 19.58 2MASS J14515797+7143173 GSPC P 41-C
P177D 15 59 13.579 +47 36 41.91   -7.90 1.57 2MASS J15591357+4736419 GSPC P177-D
P330E 16 31 33.813 +30 08 46.40 -53 -8.99 -38.77 2MASS J16313382+3008465 GSPC P330-E
SDSS132811 13 28 11.498 +46 30 50.94   -130.86 -30.80 SDSS J132811.45+463050.8 WD1326+467
SDSSJ151421 15 14 21.273 +00 47 52.81 +12 4.4 -27.04 SDSS J151421.27+004752.8 LB769 WD1511+009
SF1615+001A 16 18 14.240 +00 00 08.61   2.40 -10.94 2MASS J16181422+0000086 [B2010] SF1615+001A
SIGMA ORI 05 38 44.765 -02 36 00.28 +29.9 4.6 -0.4    
SIRIUS 06 45 08.917 -16 42 58.02 -6 -546.01 -1223.1    
SNAP-1 16 29 35.747 +52 55 53.61   -3.16 -20.80 2MASS J16293576+5255532  
SNAP-2 16 19 46.103 +55 34 17.86   -2.91 -10.95 2MASS J16194609+5534178  
VB8 16 55 35.256 -08 23 40.75 +15 -813.42 -870.61    
WD0148+467 01 52 02.962 +47 00 06.65 +64 4.64 122.02    
WD0227+050 02 30 16.628 +05 15 50.70 +16.5 76.96 -24.50    
WD0809+177 08 12 37.809 +17 37 01.43   73.48 -87.17    
WD1105-048 11 07 59.950 -05 09 26.03 +47.9 -55.55 -442.63    
WD1105-340 11 07 47.897 -34 20 51.49   39.89 -263.43    
WD1202-232 12 05 26.674 -23 33 12.14 +23.3 41.82 226.56    
WD1544-377 15 47 30.021 -37 55 08.46 +21.1 -423.69 -209.11    
WD1713+695 17 13 06.091 +69 31 25.51   -55.51 -343.04    
WD1911+536 19 12 48.566 +53 43 13.45   144.45 136.06    
WD1919+145 19 21 40.418 +14 40 41.40 +49.5 -33.02 -75.93    
WD2039-682 20 44 21.459 -68 05 21.36 +57 182.10 -228.17    
WD2117+539 21 18 56.264 +54 12 41.24   -85.45 193.19    
WD2126+734 21 26 57.656 +73 38 44.67 +8 55.34 -314.20    
WD2149+021 21 52 25.379 +02 23 19.58 +28.2 15.32 -300.53    
WD0308-565 03 09 47.918 -56 23 49.41 -68 149.24 66.92    
WD0320-539 03 22 14.820 -53 45 16.47 +57.8 6.56 -59.93    
WD0947+857 09 57 54.296 +85 29 40.88   -28.13 -27.27    
WD1026+453 10 29 45.295 +45 07 04.93   -90.46 1.68    
WD1057+719 11 00 34.243 +71 38 02.92 +76 -43.64 -21.75    
WD1327-083 13 30 13.637 -08 34 29.47 +36 -1111.1 -472.38 Gaia DR2 3630035787972473600  
WD1657+343 16 58 51.113 +34 18 53.32   8.77 -31.23 Gaia DR2 1337946019956816256  
WD2341+322 23 43 50.721 +32 32 46.73 -16 -215.82 -59.74 Gaia DR2 2871730307948650368 LAWD93

Access to the latest CALSPEC files

History  

 
2023 September Update
In addition to Ks photometry for nine G-stars from a G. Rieke draft (Absolute Calibration IV: Use of G-Type Stars as Primary Calibrators), the available Spitzer IRAC photometry of Bohlin et al. (2022) is now a constraint to the model fits for nine G-stars: 16cygb, 18sco, hd106252, hd142331, hd159222, hd167060, hd205905, hd37962, and p330e. HD142331 is not included in Bohlin et al. (2022). The E(B-V)=0.02 prior on 18 Sco is removed, even though the best fit of E(B-V)=0.06 seems a bit high.
2023 April Update

George Rieke provided precision Ks photometry that improved the constraints on fitting BOSZ LTE models for seven stars (18sco, hd106252, hd205905, hd37962, ngc2506g31, p177d, and snap2.) Because of instabilities of the fits due to partial degeneracy of effective temperature and reddening, two stars required priors of E(B-V)=0.02 for 18sco and E(B-V)=0.08 for ngc2506g31. The Rieke Ks values for 16CygB, HD159222, and P330E are consistent to better than 1% with existing fits to their HST spectrophotometry.

2023 February Update
Karl Gordon provided a new extinction curve for 912A to 32 microns and R(V)=A(V)/E(B-V)=3.1 (Gordon et al. 2023). Szabolcs Meszaros updated his BOSZ models for the G-A type stars; and those *mod* files that were originally at R=300,000 are now R=200,000. GD153 and GD71 have revised radial velocities. Of the total of 126 *stis* SEDs, there are now 71 revised stellar spectra files. There are revised *mod* files for 59 of the 76 stars with models. Only those SEDs with substantial change of >0.3% are updated.
 
2022 October Update

The CTE correction for the STIS CCD data is updated (Bohlin & Lockwood 2022); and there are 18 new stars of which only two have models. There are a total of 69 new and revised stellar spectra files (*stis*), plus new or revised model files (*mod*) for 30 of the 69 stars. An existing SED is revised if there are substantial changes of >0.5% in the stellar flux. With the new formulation for the STIS CTE correction the STIS, ACS, and WFC3 flux measures are in accord at the 1% level, not only for the primary standards and other stars in the neighborhood of V=13 and brighter, but also now for fainter stars in the V=16 range. 

2022 April Update
A column 8 is added to Table 1a for the amount of variability found by Mullally et al. (2022). Eleven revised observational and 10 revised model SEDs are in CALSPEC. Three of these have improved model fits with a change that exceeds 0.5% (1732526, 1743045, HD37962); four faint WDs have significant additional STIS observations (SDSSJ151421, WD0308-565, WD1057+719, WD1657+343); and four hot stars are now modeled with a new NLTE grid to replace the previous LTE models (10LAC, ETAUMA, LAMLEP, MUCOL). The model for the He star WD0308-565 is unchanged. Compare the Narayan et al. (2019) model to the CALSPEC model for SDSSJ151421.
 
2021 March Update

There are new pure helium Koester models for LDS749B and WD0308-565; both the model and the observational SEDs are new for these two stars. The 19 SEDs with WFC3 IR grism data are updated. The columns for FOS+Oke and IUE+Oke are deleted, and those SEDs are removed from current_calspec, because of lower precision than the robust set of modern HST data. Those demoted SEDs remain in the full CALSPEC directory.

2020 April Update

Three stars with more STIS observations and 12 new stars in the NGC6681 globular cluster are delivered. WD1057+719 now has full STIS coverage and is promoted from Table 1b to 1a. A preferred faint standard, WD1657+343 has a robust set of STIS observations along with WFC3 and NICMOS spectra, while WD1057+719 is deficient in G750L with only one exposure. The faint WD0308-565 has only two repeat verification observations, except for G230L with the desired minimum of three observations. The 12 faint NGC6681 stars are in a crowded field, and some have a few percent long-wavelength contamination from neighbors. These 12 stars appear in the finding chart of Proffitt, et al, (2003), Avila et al. (2019) and correspond to those labels a-m with the omission of star d. The Table 1a B and V values are actually HST/WFC3 F438W and F606W photometry from here.

2020 March Update

The most recent SEDs calculated by the TLUSTY and TMAP NLTE model atmosphere codes for the primary WDs G191B2B, GD153, and GD71 show improved agreement to 1% from 0.15 to 30 microns, in comparison to the previous 1% consistency only from 0.2 to 5 microns. These new NLTE models of hot WDs now provide the flux standards from the FUV to the mid-IR (Bohlin, Hubeny, and Rauch 2020, AJ, in press). The wavelength dependent change in the HST flux scale exceeds 1% only shortward of 0.167 and longward of 10 microns but does reach 2% at the short wavelength limit of STIS at 0.115 micron. In addition, there is a gray increase of 0.87% in all fluxes due to the increase of the 5556A (air) flux of Vega from 3.44 to 3.47 e-9 erg s-1 cm-2 A-1.

2019 September Update

To improve the photometric precision, the standard extraction height is increased for the STIS G230LB and G430L gratings, making the default height 11 pixels for all five CCD modes. New STIS observations of Table 1b stars in Cycle 26 have promoted eta UMa, Feige 110, Feige 34, HD93521, HZ21, HZ4, and HZ44 from Table 1b to Table 1a. New stars for JWST calibration are 109 Vir, 16 CygB, 18 Sco, delta UMi, eta1 Dor, HD101452, HD115169, HD128998, HD142331, HD167060, HD2811, and HD55677. Models for 12 low-metallicity, Southern stars from program 12813 now have R=300,000 BOSZ models. There is one new WD, while Vega and Sirius change by 1-2%, because the correction for these highly saturated data is found to change with time (Bohlin, et al. 2019).

2019 January Update

New WFC3 IR grism SEDs are incorporated in revised SEDs for 17 stars and in two new WDs WD1327_083 and WD2341_322 (Bohlin & Deustua 2019 subm.) Two new stars with only STIS data are added: BD_11D3759 (Maíz Apellániz & Weiler 2018) and a faint WD SDSS132811 for ACS/SBC calibration.

2017 November Update

The R=5000 resolution solar model from the Kurucz website is added as sun_mod_001.fits.

2017 August Update

The STIS G430L region of GRW+70 5824 is upgraded from the poor single observation to an average of multiple visits. Because of the multitude of UV observation for monitoring the changing STIS sensitivity, GRW+70 5824 is now among the best choices of standard stars. The sparse sample of cool stars in CALSPEC motivated new STIS observations of KF08T3 (K1.5III) for combining with the existing NICMOS SED to make the new kf08t3_stisnic_001. The models for the JWST calibration are updated to include the computed model continuum.

2017 February Update

Thirty-two main sequence stars for JWST calibration are re-delivered after fitting BOSZ models to the STIS & NICMOS SEDs (Bohlin et al. 2017). The R=500 model provides the extrapolation of the data to 32 microns, while the pure R=300,000 model is also available here; both models are normalized to the STIS flux distribution at 6000-9000A.

2015 April Update

The wavelength coverage of P330E is extended to 2000A, and Table 2 is updated.

2015 January Update

The G750L STIS spectra require a wider extraction width of 11 pixels, resulting in flux changes of up to ~2% (Bohlin & Proffitt 2015).

2014 March Update

A STIS flux distribution for the primary IR standard Sirius (Bohlin 2014) is added to CALSPEC with an IUE extension to shorter wavelengths and with a special Kurucz model beyond 1 micron. The specially tailored Kurucz models for both Sirius and Vega, as normalized to STIS, are also now included. Bohlin (2014) reconciled the absolute visible and IR flux measures, resulting in a 5556A flux reduction from 3.46 to 3.44 e-9 erg s-1 cm-2 A-1. Thus, all of the STIS and NICMOS SEDs are reduced by 0.6% at all wavelengths.

2013 December Update

Added coordinates for Reach et al. (2005) stars to Table 2.

2013 November Update

The low dispersion (R~500) CALSPEC database is expanded from 60 to 93 members with 19 new SEDs for JWST flux calibration (programs 12428 and 12682), 13 new southern standards (12813), and one partial flux distribution from the MAST HST archive. The new stars are measured with STIS and have preliminary extensions to 40 microns from model atmosphere fits. The basis for the wavelength dependence of the fluxes is switched from Hubeny pure hydrogen to Rauch model atmosphere calculations, and all dependence on ground based V magnitudes is removed (Bohlin, Gordon, & Tremblay 2014). This delivery encompasses an update for 48 stars with STIS or NICMOS spectrophotometry, the 32 new standards with complete STIS coverage, and eta UMa with archival STIS G230LB data. In addition, 8 high fidelity stellar models are new or updated. For the first time, high dispersion observations of G191B2B and an uncertainty covariance matrix are included.

2011 December Update

Calibration standard WD0308-565 derived from STIS data was added to the list of CALSPEC data.

2010 February Update

The 2010 February CALSPEC delivery included six revised models, 22 revised standard star flux distributions, and four new SEDs from STIS observations. HZ43 was demoted from its primary standard category some years ago because of its bright cool companion. The revisions to the flux distributions are all generally less than 1%. The main change was driven by the discovery of a small error of ~0.57% in the gain 4 to gain 1 ratio for the STIS CCD (Goudfroiij, et al. 2009). The weighting for the STIS sensitivity is changed from the total counts for each observation to equal weight for each of the three primary standard WDs, regardless of the number of observations. A few stars have additional STIS observations included in their observed average SED. The NICMOS dispersion relations have been updated (Pirzkal, Bohlin, & Thatte 2009). For seven G stars (Bohlin 2010), the observed flux distributions have been extended from the NICMOS long wavelength limit of ~2.5 microns to 40 microns, using the best fitting Castelli & Kurucz (2004) model SED.

2009 January Update

The 2009 January CALSPEC delivery encompassed six new models and 22 standard star flux distributions. The switch to TLUSTY203 caused a small change in the continuum fluxes with a 0.3% increase in the 1300A/10000A flux ratio. In a narrow region around 4000A between H-delta and H-epsilon, the new models are up to ~0.9% fainter. The correction of a V bandpass error made all stars fainter by a constant 0.35%, independent of wavelength. Pure hydrogen NLTE models are provided for the first time for the faint stars WD1057+719 and WD1657+343; and these models include a small amount of interstellar reddening (Bohlin 2007). There is one new standard, HD209458, delivered to CALSPEC for the first time. The G230LB STIS spectra of G191B2B have replaced the FOS fluxes at 1700-3850A, and new NICMOS observations are included for many stars.

UPDATES: 1996Feb22, 1999Jul19, 2001Jun5, 2004Feb27, 2006Sep1, 2007Oct LDS749B (Bohlin & Koester 2008), 2008Jul Bohlin & Cohen (2008), 2009Jan, 2010Feb, 2011Dec WD0308-565, 2013Nov, 2013Dec, 2014Mar, 2015Jan, 2015Apr, 2017Feb, 2017Aug, 2017Nov, 2019Jan, 2019Sep, 2020Mar, 2020Apr, 2021Mar, 2022Apr, 2022Oct, 2023Feb, 2023Apr, 2023Sep..

PLEASE report errors or send comments to bohlin@stsci.edu

Thanks to Pierre Maxted for a set of corrections.

This page made use of the SIMBAD database, operated at CDS, Strasbourg, France.

References

Avila, R. J., et al. 2019, Instrument Science Report, ACS 2019-05, (Baltimore:STScI)
Bohlin, R. C., & Lockwood, S. 2022, Instrument Science Report, STIS 2022-07, (Baltimore:STScI)
Bohlin, R. C., Krick, J. E., Gordon, K. D., and Hubeny, I. 2022, AJ, 164, 10
Bohlin, R. C., Hubeny, I., & Rauch, T. 2020, AJ, 160, 21
Bohlin. R. C., & Deustua, S. E. 2019, AJ, 157, 229.
Bohlin, R. C., Deustua, S. E., and de Rosa 2019, AJ, 158, 211
Bohlin, R. C., Meszaros, Sz., Fleming, S., Gordon, K. D., Koekemoer, A. M., & Kovacs, J. 2017, AJ, 153, 234
Bohlin, R. C., & Landolt, A. U. 2015, AJ, 149, 122
Bohlin, R. C., & Proffitt, C. R. 2015, Instrument Science Report, STIS 2015-01, (Baltimore:STScI)
Bohlin, R. C. 2014, AJ, 147, 127
Bohlin, R. C., Gordon, K. D., & Tremblay, P.-E. 2014, PASP, 126, 711
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    Vol. 364, p. 315 ed. C. Sterken
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Castelli, F., & Kurucz, R. 2004, IAU Symp. No. 210, Modeling of Stellar Atmospheres, eds. N. Piskunov, W. Weiss, 
    & D. Gray 2003, poster A20; also arXiv:0405.087 [astro-ph]
Cohen, M., Megeath, S.~T., Hammersley, P.~L., Martin-Luis, F., & Stauffer, J. 2003, AJ, 125, 2645
Colina, L., & Bohlin, R. 1994, AJ, 108, 1931
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Colina, L., Bohlin, R.C., & Castelli, F. 1996, AJ, 112, 307
Gilliland, R., & Rajan, A. 2011, Instrument Science Report, WFC3 2011-03, (Baltimore:STScI)
Gordon, K. D., et al. 2023, ApJ, 950, 86
Goudfrooij, P., Wolfe, M. A., Bohlin, R. C., Proffitt, C. R., & Lennon, D. J. 2009, Instrument Science Report, 
    STIS 2009-02, (Baltimore:STScI)
Kurucz, R. 2003, and all references to Kurucz website, http://kurucz.harvard.edu/
Landolt, A., & Uomoto, A. 2007, AJ, 133, 768
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Mullally, S. E., et al. 2022, AJ, 163, 136
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Pirzkal, N., Bohlin, R.,  & Thatte D. 2009, Instrument Science Report, NICMOS 2009-006, (Baltimore:STScI)
Proffitt, C. R., Brown, T. M., Mobasher, B., & Davies, J. 2003, Instrument Science Report, STIS 2003-01, 
    (Baltimore:STScI)
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