Oke (1990) Spectrophotometric Standards

Oke (AJ, 99, 1621, 1990) has provided absolute spectral energy distributions covering the wavelength range 3200 to 9200A in AB magnitudes for 25 stars. The measurements were made with the Double Beam Spectrogrpph of the Hale 5m telescope. The reduced magnitudes are tabulated at 1A intervals from 3300 to 4700A and at 2A intervals from 4700 to 9200A. Comparison of the fluxes with those determined elsewhere showed that Oke's absolute magnitudes are systematically brighter by 0.04 mag. The magnitudes and fluxes plotted have been corrected for this effect. Colina & Bohlin (AJ, 1931, 1994) tabulate the differences between the original Oke fluxes, in terms of synthesized B and V magnitudes, and Landolt photometry for each star individually. The AB magnitudes were converted to flux (ergs/cm/cm/s/A) using the formula
ABMAG = -2.5 alog10(Fnu) - 48.59
(Hamuy et al., PASP, 104, 533, 1992), where Fnu is in ergs/cm/cm/s/Hz.

 No.   Name         alpha (2000) delta     Sp.     V     AB
                                           Type        (5460A)
---------------------------------------------------------------
  1   G158-100     00 33 54.3  -12 07 57   sdG   14.89  14.82
  2   HZ 4         03 55 21.7  +09 47 19   DA4   14.52  14.47
  3   G191B2B      05 05 30.6  +52 49 54   DAO   11.78  11.72
  4   G193-74      07 53 27.4  +52 29 36   DC    15.70  15.58
  5   BD+75d325    08 10 49.3  +74 57 57   O5p    9.54   9.52
  6   Feige 34     10 39 36.7  +43 06 10   DO    11.18  11.13
  7   HD 93521     10 48 23.5  +37 34 13   09Vp   7.04   6.96
  8   HZ 21        12 13 56.4  +32 56 31   DO2   14.68  14 67
  9   Feige 66     12 37 23.6  +25 04 00   sdO   10.50  10.43
 10   Feige 67     12 41 51.8  +17 31 20   sdO   11.81  11.78
 11   G60-54       13 00 09.5  +03 28 56   DC    15.81  15.73
 12   HZ 44        13 23 35.4  +36 08 00   sdO   11.66  11.65
 13   GRW+70d5824  13 38 51.8  +70 17 08   DA3   12.77  12.72
 14   BD+33d2642   15 51 59.9  +32 56 55   B2IV  10.81  10.74
 15   G138-31      16 27 53.6  +09 12 24   DA7   16.14  16.07
 16   G24-9        20 13 56.0  +06 42 55   DC    15.72  15.77
 17   BD+28D4211   21 51 11.1  +28 51 52   Op    10.51  10.47
 18   B0+25d4655   21 59 39.3  +26 25 42          9.76   9.65
 19   LTT 9491     23 19 35.0  -17 05 30   DC    14.04  14.06
 20   Feige 110    23 19 58.4  -05 09 56   DOp   11.82  11.81
 21   GD 248       23 26 06.7  +16 00 21   DC    15.09  15.08
 22   GD 50        03 48 50.1  -00 58 30   DA2   14.06  14.06
 23   SA95-42      03 53 43.7  -00 04 33         15.61  15.60
 24   GD 108       10 00 47.3  -07 33 31   sdB?  13.56  13.57
 25   NGC 7293     22 29 38.5  -20 50 13         13.51  13.48

Note: The ABMAG listed for HZ 4 in Table 1 of Oke (1990) is in error. The value should be 14.47.

jwalsh@eso.org