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CALSPEC Calibration Database

Please reference Bohlin, Gordon, & Tremblay (2014) for research that makes use of this database.

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 6-9, plus ".fits". For example, a standard that has STIS data is "bd_28d4211_stis_004.fits". 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).

Using the BOSZ model grid for main-sequence stars, a set of 32 stars for JWST calibration is developed by Bohlin et al. (2017). A BOSZ model at R=300,000 (col. 6) is provided for each of these JWST standards, while a separate file includes the STIS and NICMOS fluxes concatenated with an R=500 BOSZ model for the extrapolation to 32 microns (col. 7). 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=300,000 are available for a few of the WD stars, as listed in column 6 of Table 1. The modeled IR fluxes for 13 stars are compared to Spitzer IRAC photometry in Bohlin et al. (2011). Models for the three fundamental primary WD standards GD71, GD153, and G191B2B (Bohlin et al. 2014) are calculated with the NLTE code of Rauch et al. (2013), which includes metal line blanketing for G191B2B. Previous to November 2013, all three stars had pure hydrogen models calculated with the Hubeny NLTE code. This change results in a wavelength dependent shift of the HST/STIS flux scale, but by <~1% below 2 microns.

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 or 40 microns and cover the long wavelength limits of 2.7 microns for NICMOS, 1.7 microns for WFC3, 1.1 microns for STIS and ACS, and >30 microns for some JWST or Spitzer filters. Vega was observed with STIS (Bohlin & Gilliland 2004a) and revised by Bohlin (2007). The composite flux standard alpha_lyr_stis consists of IUE data from 1152-1675A, STIS CCD fluxes from 1675-5350A, and a specially tailored Kurucz 9400K model longward of 5350A (Kurucz 2005). From 900-1152A, the hotter Kurucz (2003) 9550K model is more continuous with the IUE flux. 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.

Column 7 lists the suffix names for the gold standard stars with STIS, NICMOS (Bohlin, Dickinson, & Calzetti 2001, hereafter BDC; Bohlin 2007), or WFC3 data (Bohlin & Deustua 2019). The naming convention in column 7 includes STIS, NIC, and WFC to indicate some contribution from any of the three HST spectrophotometers.

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. The order of preference for the choice of a standard flux distribution is from left to right in the Tables 1a and 1b, i.e. from the best in column 7 to the least preferred option with the lowest quality in column 9.

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 space and the ground with a model spectrum for the near-infrared (Colina, Bohlin, & Castelli 1996). The newer 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, 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_001.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).

Cautions

Even though the column-7, gold-flux distributions are the best observational SEDs, caution is still required, because some SEDs flagged with an asterisk are not entirely from the gold-standard STIS, NICMOS, or WFC3 data. Additional IUE, FOS, or Oke observations have lower signal-to-noise, wavelength precision, and photometric accuracy, as discussed in BDC. Thus, the FITS headers of any SED used for precision science applications should be checked to be sure that the wavelength region of interest is identified as STIS, NICMOS, or WFC3. To aid in selecting the best SEDs, Table 1 is divided into 1a and 1b, where the 1a stars in column 7 have all the possible STIS coverage and 1b tabulates stars that are missing some STIS coverage. In case the UV is too bright for the STIS MAMA detectors, IUE or FOS data may be used for 1a stars, but the asterisk flag is retained to remind users of this deficiency. Stars cooler than A type are considered complete, if the only missing coverage is in regions where the UV continuum flux is tiny and undetectable. For the coolest M, L, and T stars, G750L provides complete STIS coverage. STIS observations of several Table 1b stars are in progress in Cycle 26 in order to promote those SEDs to Table 1a.

Table 1a: Files of the Flux(1) Standards with Complete STIS Coverage

Star name     Sp. T.     V      B-V      Name 	   Model 	   STIS**       FOS+Oke   IUE+Oke
  [1]           [2]     [3]     [4]       [5] 	    [6] 	    [7]           [8]       [9]

10 Lac         O9V     4.88    -0.21   10lac	    _mod_002   _stis_004                   
1732526        A4V     12.53    0.12   1732526      _mod_002   _stisnic_004	 	   
1740346(2)     A6V     12.48    0.20   1740346      	       _stisnic_003	 	   
1743045        A8III   13.52    0.28   1743045      _mod_002   _stisnic_004	 	   
1757132        A3V     12.01   -0.10   1757132      _mod_003   _stiswfc_001	 	   
1802271        A2V     11.98    0.02   1802271      _mod_003   _stiswfcnic_001	 	   
1805292        A4V     12.28    0.14   1805292      _mod_002   _stisnic_004	 	   
1808347        A3V     11.69    0.49   1808347      _mod_003   _stiswfc_001	 	   
1812095        A5V     11.74    0.20   1812095      _mod_002   _stisnic_004	 	   
2M0036+18      L3.5   J=12.47     ...  2m003618     	       _stiswfcnic_001	 	   
2M0559-14      T4.5   J=13.80     ...  2m055914     	       _stiswfcnic_001	 	   
AGK+81 266     sdO     11.95   -0.36   agk_81d266   	       _stisnic_006*	 	   _005
ALPHA LYR      A0V      0.031   0.00   alpha_lyr    _mod_002   _stis_008*	 	   _004
BD+02 3375     A5       9.93    0.45   bd02d3375    	       _stis_003	 	   
BD-11 3759     M3.5V   11.32    1.60   bd11d3759    	       _stis_001	 	   
BD+17 4708(3)  sdF8     9.47    0.44   bd_17d4708   	       _stisnic_006	 	   
BD+21 0607     F2       9.22    0.44   bd21d0607    	       _stis_003	 	   
BD+26 2606     A5       9.73    0.39   bd26d2606    	       _stis_003	 	   
BD+29 2091     F5      10.22    0.50   bd29d2091    	       _stis_003	 	   
BD+54 1216     sdF6     9.71    0.48   bd54d1216    	       _stis_003	 	   
BD+60 1753     A1V      9.65    0.07   bd60d1753    _mod_003   _stiswfc_001	 	   
BD+75 325      O5p      9.55   -0.33   bd_75d325    	       _stis_004*	 _fos_003  _005
C26202         F8IV    16.64    0.26   c26202	    _mod_003   _stiswfcnic_001	 	   
G191B2B        DA.8   11.781   -0.33   g191b2b      _mod_010   _stiswfcnic_001*  _fos_003  _005
GD153          DA1.2  13.346   -0.29   gd153	    _mod_010   _stiswfcnic_001   _fos_003  
GD71           DA1.5  13.032   -0.25   gd71	    _mod_010   _stiswfcnic_001   _fos_003  
GJ754.1A       DBQA5   12.29    0.05   gj7541a      	       _stis_003	 	   
GRW+70 5824    DA2.4   12.60   -0.06   grw_70d5824  	       _stiswfcnic_001   	   _005
HD009051       G7III    8.92    0.81   hd009051     	       _stis_003	 	   
HD031128       F4V      9.14    0.41   hd031128     	       _stis_003	 	   
HD074000       sdF6     9.66    0.45   hd074000     	       _stis_003	 	   
HD106252       G0       7.36    0.64   hd106252     _mod_002   _stis_004	 	   
HD111980       F7V      8.38    0.53   hd111980     	       _stis_003	 	   
HD116405       A0V      8.34   -0.07   hd116405     _mod_002   _stis_004	 	   
HD14943        A5V      5.91    0.19   hd14943      _mod_002   _stis_004	 	   
HD158485       A4V      6.50    0.13   hd158485     _mod_002   _stis_004	 	   
HD159222       G1V      6.56    0.65   hd159222     _mod_002   _stis_004	 	   
HD160617       F        8.73    0.45   hd160617     	       _stis_003	 	   
HD163466       A6V      6.85    0.19   hd163466     _mod_002   _stis_004	 	   
HD165459(5)    A4V      6.86    0.13   hd165459     _mod_002   _stisnic_004	 	   
HD180609       A0V      9.42    0.15   hd180609     _mod_002   _stis_004	 	   
HD185975       G3V      8.10    0.68   hd185975     	       _stis_003	 	   
HD200654       G        9.11    0.63   hd200654     	       _stis_003	 	   
HD205905       G2V      6.74    0.62   hd205905     _mod_002   _stis_004	 	   
HD209458(6)    G0V      7.65    0.59   hd209458     _mod_002   _stisnic_007	 	   
HD37725        A3V      8.31   -0.19   hd37725      _mod_003   _stiswfc_001	 	   
HD37962        G2V      7.85    0.65   hd37962      _mod_002   _stis_004	 	   
HD38949        G1V      7.80    0.57   hd38949      _mod_002   _stis_004	 	   
HD60753(7)     B3IV     6.68   -0.09   hd60753      	       _stis_003	 	   
HS2027+0651    DO      16.9     ...    hs2027	    	       _stis_004	 	   
HZ43(8)        DA      12.91   -0.31   hz43	    _mod_010   _stis_004*	 _fos_003  
HZ43B(8)       M3Ve    14.30    ...    hz43b	    	       _stis_004	 	   
KF06T2        K1.5III  13.80    1.30   kf06t2	    _mod_003   _stiswfcnic_001	 	   
KF08T3        K0.5III  13.18    1.21   kf08t3	    _mod_002   _stisnic_001	 	   
ksi2 Ceti      B9III    4.28   -0.04   ksi2ceti     _mod_002   _stis_004	 	   
LAM LEP        B0.5IV   4.27   -0.23   lamlep	    _mod_002   _stis_004	 	   
LDS749B        DBQ4   14.674   -0.04   lds749b      _mod_005   _stisnic_006	 	   _005
MU COL         O9.5V    5.15   -0.26   mucol	    _mod_002   _stis_004	 	   
P041C(9)       GOV     12.16    0.68   p041c	    _mod_002   _stisnic_007*	 _001	   
P177D          G0V     13.49    0.60   p177d	    _mod_002   _stisnic_007*	 _001	   
P330E          G2V     12.92    0.64   p330e	    _mod_003   _stiswfcnic_001*  _001	   
SDSS132811     DA     g=17.01          sdss132811   	       _stis_001	 	   
SF1615+001A    G       16.75    0.49   sf1615_001a  _mod_002   _stisnic_007	 	   
SIRIUS         A1V     -1.46    0.00   sirius	    _mod_002   _stis_002*	 	   
SNAP-1         sd:B    15.40    0.20   snap1	    	       _stisnic_006	 	   
SNAP-2         G0-5    16.23    0.86   snap2	    _mod_003   _stiswfcnic_001	 	   
VB8            M7V     16.92    1.8    vb8	    	       _stiswfcnic_001	 	   
WD0308-565     sdB     14.07   -0.11   wd0308_565   _mod_003   _stis_004	 	   
WD0320-539     DA      14.9     ...    wd0320_539   	       _stis_004	 	   
WD0947+857     DA      16.4     ...    wd0947_857   	       _stis_004	 	   
WD1026+453     DA      16.13   -0.04   wd1026_453   	       _stis_004	 	   
WD1057+719     DA1.2   14.68    ...    wd1057_719   _mod_005   _stisnic_006	 	   
WD1327-083     DA3.5   12.34    0.06   wd1327_083   	       _stiswfc_001	 	   
WD1657+343     DA.9     16.1     ...   wd1657_343   _mod_005   _stiswfcnic_001	 	   
WD2341+322     DA3.8   12.94    0.12   wd2341_322   	       _stiswfc_001	 	   

Table 1b: Files of the Flux(1) Standards with Incomplete STIS Coverage

Star name     Sp. T.     V      B-V      Name 	   Model 	   STIS**       FOS+Oke   IUE+Oke
  [1]           [2]     [3]     [4]       [5] 	    [6] 	    [7]           [8]       [9]

1812524        A4V     12.27 	0.18   1812524  	     _nic_004                    
BD+25 4655     B0       9.69   -0.31   bd_25d4655	     	 	         	 _002
BD+28 4211(4)  sdO     10.51   -0.34   bd_28d4211	     _stis_004*        _fos_003  _005
BD+33 2642     B2IV    10.83   -0.17   bd_33d2642	     	 	       _fos_003  _004
ETA UMA        B3V      1.85   -0.10   etauma		     _stis_003*         	 
FEIGE110       sdO     11.83   -0.30   feige110 	     _stisnic_006*       	 _005
FEIGE34        sdO     11.14   -0.23   feige34  	     _stis_004*          	 _005
FEIGE66        sdO     10.51   -0.29   feige66  	     	 	         	 _002
FEIGE67        sdO     11.82   -0.34   feige67  	     	 	         	 _002
G93-48         DA3     12.74   -0.01   g93_48		     	 	         	 _004
GD108          sdB     13.56   -0.22   gd108		     	 	         	 _005
GD50           DA1.2   14.06   -0.28   gd50		     	 	         	 _004
HD93521        O9Vp     6.99   -0.27   hd93521  	     _stis_004*          	 _005
HZ2            DA2.3   13.88   -0.09   hz2		     	 	         	 _005
HZ21           DO2     14.69   -0.33   hz21		     _stis_004*          	 _005
HZ4            DA3.4   14.51 	0.09   hz4		     _stis_005*          	 _004
HZ44           sdO     11.67   -0.29   hz44		     _stis_004*        _fos_003  _005
KF01T5         K1III   13.56 	...    kf01t5		     _nic_003	        	 
KF06T1        K1.5III  13.52 	0.98   kf06t1		     _nic_003	        	 
LB227          DA3.2   15.32 	0.06   lb227		     	 	         	 _004
LTT9491        DB3     14.10 	0.03   ltt9491  	     	 	         	 _002
NGC7293        DAO.5   13.52   -0.36   ngc7293  	     	 	         	 _005
SUN            G2V    -26.75 	0.63   sun_reference	     _stis_002*         	 
SUN            G2V    -26.75 	0.63   sun	   _mod_001  		        	 
* WARNING. Some wavelength coverage from sources of lower precision, such as IUE, FOS, or Oke.
** Column 7 is preferred for the best absolute fluxes, where 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)

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

              R.A.  (2000)     Decl.       Vr      PM (mas/yr)        Simbad Name        Alternate Simbad Name
10 Lac       22 39 15.679  +39 03 00.97   -10    -0.32    -5.46   
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 27.17   +60 43 35.7        	                  2MASS J18022716+6043356 
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   			  
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+25 4655   21 59 41.975  +26 25 57.40         -37.46   -41.67   			  
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+33 2642   15 51 59.886  +32 56 54.33   -95   -14.56     0.92   			  
BD+54 1216   08 19 22.572  +54 05 09.63   +66   -34.20  -628.56   HD233511		  
BD+60 1753   17 24 52.277  +60 25 50.78       	  3.98     1.81   			  
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
ETA UMA      13 47 32.438  +49 18 47.76   -13  -121.17   -14.91   HD120315		  
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		  
FEIGE66      12 37 23.516  +25 03 59.87    +1     1.83   -27.42   BD+25 2534		  
FEIGE67      12 41 51.790  +17 31 19.75       	 -7.33   -37.28   BD+18 2647		  
G191B2B       5 05 30.618  +52 49 51.92  +22.1  12.59    -93.52   BD+52 913                  EGGR 247 WD0501+527
G93-48       21 52 25.379  +02 23 19.58   +32    15.43  -300.55   EGGR150  WD2149+021	  
GD108        10 00 47.246  -07 33 30.78   +90   -42.37    -1.88      			  
GD153        12 57 02.322  +22 01 52.63  +25.8  -38.41  -202.95   WD1254+223		  
GD50         03 48 50.186  -00 58 32.29   +87    84.43  -162.96   WD0346-011 		  
GD71          5 52 27.620  +15 53 13.23  +23.4   76.84  -172.94   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  -402.09   -24.61   LAWD52  WD1337+705	  
HD009051     01 28 46.503  -24 20 25.44   -72    53.56   -17.03   			  
HD031128     04 52 09.910  -27 03 50.94  +112   164.76   -26.52   			  
HD074000     08 40 50.804  -16 20 42.51  +206   350.82  -484.16   			  
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   			  
HD116405     13 22 45.124  +44 42 53.91   -19     8.01   -10.29   			  
HD14943      02 22 54.675  -51 05 31.66    +5    22.33    66.38   			  
HD158485     17 26 04.837  +58 39 06.83   -30    -9.10    14.67   			  
HD159222     17 32 00.992  +34 16 16.13   -52  -240.70    63.71   			  
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   			  
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   			  
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   			  
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   			  
HD60753      07 33 27.319  -50 35 03.31   +20    -3.12     5.31   			  
HD93521      10 48 23.512  +37 34 13.09   -14     0.22     1.72   			  
HS2027+0651  20 29 32.506  +07 01 07.70       	  9.24     1.53   WD2027+0651		  
HZ2          04 12 43.555  +11 51 48.97   +64    59.18   -90.67   WD0410+117		  
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   			  
LAM LEP      05 19 34.524  -13 10 36.44   +20    -3.30    -4.91   			  
LB227        04 09 28.904  +17 07 54.39         111.45   -22.02   EGGR29  WD0406+169	  
LDS749B      21 32 16.233  +00 15 14.40   -81   413.23    27.27   LAWD87  WD2129+000      
LTT9491      23 19 35.388  -17 05 28.47         242.14    10.40   EGGR264                    WD2316-173 WD2317-173
MU COL       05 45 59.895  -32 18 23.16  +109     2.99   -22.03    			  
NGC7293      22 29 38.545  -20 50 13.75   -15    38.87    -3.42      			  
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
SF1615+001A  16 18 14.240  +00 00 08.61       	  2.40   -10.94   2MASS J16181422+0000086    [B2010] SF1615+001A
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    			  
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

History

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

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

REFERENCES

Bohlin, R.C. 1996, AJ, 111, 1743
Bohlin, R.C. 2000, AJ, 120, 437
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. 2010, AJ, 139, 1515
Bohlin, R. C. 2014, AJ, 147, 127
Bohlin. R. C., & Cohen, M. 2008, AJ, 136, 1171
Bohlin, R.C., Colina, L., & Finley, D.S. 1995, AJ, 110, 1316
Bohlin. R. C., & Deustua, S. E. 2019, AJ, submitted.
Bohlin, R. C., Dickinson, M. E., & Calzetti, D. 2001, AJ, 122, 2118 (BDC)
Bohlin, R. C., & Gilliland, R. L. 2004a, AJ, 127, 3508
Bohlin, R. C., & Gilliland, R. L. 2004b, AJ, 128, 3053
Bohlin, R. C., Gordon, K. D., & Tremblay, P.-E. 2014, PASP, 126, 711
Bohlin, R. C., & Koester, D. 2008, AJ, 135, 1092
Bohlin, R. C., et al. 2011, AJ, 141, 173
Bohlin, R. C., & Landolt, A. U. 2015, AJ, 149, 122
Bohlin, R. C., Meszaros, Sz., Fleming, S., Gordon, K. D., Koekemoer, A. M., &
	Kovacs, J. 2017, AJ, 153, 234
Bohlin, R., C. & Proffitt, C. R. 2015, Instrument Science Report, STIS 2015-01,
	(Baltimore:STScI)
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
Colina, L., & Bohlin, R. 1997, AJ, 113, 1138
Colina, L., Bohlin, R.C., & Castelli, F. 1996, AJ, 112, 307
Gilliland, R., & Rajan, A. 2011, Instrument Science Report, WFC3 2011-03, (Baltimore:STScI)
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/
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
Maíz Apellániz, J., & Weiler, M. 2018, A&A, 619, 180
Megessier, C. 1995, A&A, 296, 771
Oke, J.B. 1990, AJ, 99, 1621
Pancino, E., et al. 2012, MNRAS, 426, 1767
Pirzkal, N., Bohlin, R.,  & Thatte D. 2009, Instrument Science Report, NICMOS
	2009-006, (Baltimore:STScI)
Rauch, T., Werner, K., Bohlin, R., & Kruk, J. 2013, A&A, 560, A106
Reach, W. T., et al. 2005, PASP, 117, 978
Rieke, G. H., et al. 2008, AJ, 135, 2245 
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

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Last modified, January 2019