A list of 59 Spectrophotometric Standards is presented. Positions accurate to 1 arcsecond have been newly determined for all stars in the list. Where the proper motions are known, the positions are given for epoch and equinox B1950.0; otherwise the epoch is that of the Palomar Observatory Sky Survey (POSS) plate on which the position was measured. A plot of flux distribution and an identification chart are given for each standard. Remarks on a number of minor errors and inconsistencies in previous papers are collected in the section headed `Notes'.
Introduction: This Technical Note has been compiled primarily for observers requiring a quick-reference list of stars which can be used for flux calibration purposes. It is based on Strom's (1977) list of spectrophotometric standards for use with the Kitt Peak telescopes and is intended both for use at the telescope and for reference when planning observations. The aim here has been to maintain essentially the same style of presentation as Strom, but enhance the usefulness for today's observers by: providing new, more accurate positions; checking the proper motions; adding a few extra standards; and by pointing out a number of minor errors and inconsistencies in Strom's and other related papers. Most of the 59 stars discussed come from the Kitt Peak list. Nine other standards have been included: 5 faint stars measured by Filippenko and Greenstein (1984), and 4 bright stars by Oke and Gunn (1983) who give flux magnitudes to 12,000Å.
Apart from the newly derived positions, all the data given are gathered
from other sources and the original references should be consulted for
detailed information regarding instruments used, observational
techniques, estimates of precision, etc.
Although this paper has been prepared for observers using the
telescopes at the Roque de los Muchachos Observatory on La Palma, we
hope that astronomers at other northern hemisphere sites will also find
its contents useful.
Contents: Summary data for all the stars in the list are gathered in Table 1, together with some notes on particular stars. In addition to the star name the table contains: the Eggen-Greenstein (EG) number; accurate equatorial coordinates and proper motions; a `visual' magnitude; a spectral type; and the local ING Name by which the star is known to the La Palma computers.
Table 2 provides a handy cross-reference between star
names and the names of the Figaro files containing the detailed
spectrophotometric data.
It also indicates, for each star, the range of wavelengths covered by
the data in the Figaro files.
Figaro is a software package for the reduction of spectral data:
it was written by Keith Shortridge of the Anglo-Australian Observatory
and is widely available via the Starlink network.
The main body of the Technical Note consists of data sheets for the
standards, set out in order of right ascension with one star per page.
Each page is identified, in the top right-hand corner, by the ING
Name of the standard star and consists of a finding chart, a data
block (values taken from Table 1) and a plot of the
flux distribution.
More detail on each of these aspects is given in the paragraphs which
follow.
Star names:
In the course of preparing this paper it soon became clear that many of
the stars in the list had several aliases.
All those discovered by the authors have been included for the sake of
completeness, but there may well be others.
The names of most interest to observers visiting the Roque de los
Muchachos Observatory will be those used in the system catalogues of
the control computers of the various La Palma telescopes.
The names are constructed using the letters SP (to indicate that
they refer to spectrophotometric standards) together with a designation
(based on its position) following the IAU convention for the naming of
astronomical sources.
Using this number at the telescope, or in a control file, ensures that
the telescope will set directly on the correct position at the date of
the observation, without the observer having to be concerned with the
proper motion or precession.
[Warning:
Observers who have used these standards in the past should note that
the the previous naming system--the letters SP followed by the
item number of the star in the list--has been discontinued:
cross-checks with the new names should be made using either the
coordinates or the star's name as given in column 1 of
Table 1.]
Positions:
Given the excellent setting capabilities of modern telescopes,
efficiency of acquisition is improved by having positions as accurate as
possible.
In order to provide coordinates for these standards which were
uniformly accurate to 1 arcsecond or better, the positions of all the
stars in the list were measured afresh from the POSS copy plates using
a Coradograph measuring machine.
Each standard was referred to 8-10 nearby reference stars (AGK3 stars
wherever possible, but SAO stars south of declination -2 degrees).
These new positions are published here for the first time.
Proper motions: Since a large proportion of the standards are nearby dwarfs, and would thus be expected to have a significant proper motion, particular care was taken to establish accurate values. All proper motion catalogues available at Herstmonceux were searched for relevant entries. A majority of the standards appear in lists published by Giclas in various Lowell Observatory Bulletins, and in the well-known proper motion catalogues of Luyten, published by the University of Minnesota. Their values have been adopted here.
For the remainder, distances were estimated using the apparent magnitude
and spectral type, and all but the most distant stars were observed
during 1987 with the 13-inch Astrographic telescope at Herstmonceux.
Again 8-10 reference stars were measured on each plate, and the
standard was referred to AGK3 stars or SAO stars as appropriate.
The positions derived from these plates were compared with the earlier
ones from the POSS plates to give proper motions over a base line of
about 35 years.
Stars treated in this way are noted in Table 1.
Magnitudes and spectral types: The magnitudes and spectral types given in Table 1 are all taken from the papers in which the relevant spectrophotometry first appeared. The magnitude column gives the brightness of the star at wavelength 5556Å (towards the middle of the V band) and is intended to give an approximate `visual' magnitude for identification and planning purposes. For all the stars in the Kitt Peak list m5556 is taken straight from the tables of flux distributions: for the new stars values for lambda 5556 were interpolated in the distributions given in the original papers.
The spectral types give a rough idea of the overall light distribution.
Two stars do not have a normal spectral type designation in this column
and require special mention.
Eggen and Greenstein (1965a) note that the spectrum of
Grw +70 8247 is ``unique in the presence of unidentified
lambda 4135 bands''.
They also comment (1967) that the blue star G47-18 ``has atomic
C I and broad molecular bands of C2; no other white dwarf is
known to have these features.
The
lambda 4670 stars have only C2.''
Charts:
A photocopy of a Polaroid print of each field from the Palomar
Observatory Sky Survey chart indicates the position of the object
at the epoch of the chart.
As an aid to locating the star's current position, each chart is
accompanied by a simple line drawing showing the magnitude and
direction of fifty years' proper motion to the same scale as the
Polaroid print.
It is important to remember that the mean epoch of the POSS plates
is approximately 1950 (the exact epoch of each chart is given with the
line drawing).
The charts are copied from the POSS prints:
copyright of the National Geographic Society--Palomar Observatory Sky
Survey. Reproduced by permission from the Hale Observatories.
Flux distributions: The plots of flux distribution were made using data from the Figaro database where possible, and otherwise from the original publications. For Starlink users, the directory containing the files is pointed to by the logical name FIGARO_ PROG_ S. Each file has file extension .TAB. The Figaro filenames are listed in Table 2 together with information on the wavelength range covered for each star. The plots presented on the data sheets were produced using Starlink's MONGO graphics package at the RGO node.
Eggen and Greenstein (1965a) note that the spectrum of
Grw +70 8247 is unique in the presence of unidentified
lambda 4135 bands.
They also comment (1965b) that the blue star G47-18 ``has atomic
C I and broad molecular bands of C2; no other white dwarf is
known to have these features.
The
lambda 4670 stars have only C2.''
Notes: For two of the stars in the original Kitt Peak list there was an regarding the identity of the star: in each case the star at the positions given on their data sheets did not correspond with the images marked on their finding charts. Charles Jenkins had previously observed HZ 7 and confirmed that the star identified on the chart was indeed the standard. For LDS 235B David King obtained INT spectra for both candidates and again found that the chart indicated the correct star. Two errors in the proper motions appear in both Eggen and Greenstein's (1965a) paper and the original Kitt Peak list (Strom 1977). The proper motion in declination of 40 Eri B was given the wrong sign: the correct value is -3.42 arcseconds per year. For L970-30 the proper motions in right ascension and declination were transposed.
L1512-34B started life as plain L1512-34 (Luyten 1944) and appeared
again as such in the `Luyten Two Tenths' catalogue (Luyten 1961), often
referred to as LTT.
In the latter compilation Luyten gave the star the additional
designation LTT16991 and noted that it has common proper motion with
LTT16990 (also known as L1512-35).
In a later paper Eggen and Greenstein (1965a) included both stars in
their discussion of wide binaries but labelled LTT16991 as L1512-34B
and LTT16990 as L1512-34A.
Ample evidence that they are in fact the same stars is provided by the
exact correspondence of other attributes, particularly position and
spectral type, and the excellent identification charts of Giclas
(1963).
The Eggen-Greenstein designations have found their way into some
subsequent publications, including Oke (1974) and Strom (1977).
The original designation, L1512-34, has been adopted here.
Following some initial doubts introduced by an anomalous value for the
proper motion of HD 19445 (in a computer held version of AGK3),
additional confirmation of its position was sought from Carlberg
Automatic Meridian Circle observations.
The star is not included in the printed version of AGK3 and the
position and proper motion derived from the POSS measurements and the
CAMC observations both confirm Luyten's original values.
Acknowledgements: Charles Jenkins and David King were most helpful in resolving inconsistencies of identification. Steve Unger's sensible suggestion of adopting the naming convention recommended by the IAU resulted in a lot of revision and made the authors peeved that they had not thought of the idea themselves! David King pointed out the usefulness of including the wavelength ranges in Table 2. Robert Laing has been tireless in encouraging us to produce `properly documented' collections of essential standards for use on La Palma.
References:
Eggen, O.J. and Greenstein, J.L., 1965a. Ap.J. 141, 83.
Eggen, O.J. and Greenstein, J.L., 1965b. Ap.J. 142, 925.
Eggen, O.J. and Greenstein, J.L., 1967. Ap.J. 150, 927.
Filippenko, A.V. and Greenstein, J.L., 1984. P.A.S.P. 96,
530.
Giclas, H.L., 1963. Lowell Obs. Bull. No. 120.
Luyten, W.J., 1944. Pub. Univ. Obs. Minnesota III No. 4.
Luyten, W.J., 1961. Catalogue of 7127 Stars in the Northern Hemisphere
with Proper Motions Exceeding 0.2 arcseconds
Annually, Lund Press, Minneapolis, Minn.
Oke, J.B., 1974. Ap.J.Suppl., 27, 21.
Oke, J.B. and Gunn, J.E., 1983. Ap.J. 266, 713. (Flux magnitudes
given to 12,000Å.)
Stone, R.P.S., 1977. Ap.J. 218, 767.
Strom, K.M., 1977. Kitt Peak National Observatory Memorandum,
``Standard Stars for Intensified Image Dissector Scanner
Observations''.
G158-100 00 31 22.2 -12 24 21 +0.011 -0.17 14.82 sdG SP0031-124 3,5
Hiltner 102 01 05 53.7 +62 31 31 10.35 B0III SP0105+625 2
L870-2 01 35 26.2 -05 14 42 +0.037 -0.34 12.82 DA SP0135-052 1,6
Feige 15 01 46 28.4 +13 18 18 +0.003 +0.03 10.41 A1V SP0146+133 2,35
Feige 24 02 32 31.0 +03 30 52 +0.003 -0.03 12.42 DA+M1V SP0232+035 1,35
Feige 25 02 36 00.0 +05 15 17 12.01 B6V SP0236+052 2
HD 19445 03 05 28.6 +26 09 06 -0.016 -0.83 7.98 sdF SP0305+261 4,7
HZ 4 03 52 37.9 +09 38 35 +0.012 0.00 14.57 DA SP0352+096 1,35
LB 1240 04 01 32.6 +25 00 53 +0.011 -0.23 13.94 DA SP0401+250 1,8
LB 227 04 06 36.7 +17 00 05 +0.008 -0.02 15.29 DA SP0406+170 1,9
HZ 2 04 09 57.2 +11 44 16 +0.003 -0.09 14.07 DA SP0409+117 1
40 Eri B 04 13 03.6 -07 44 06 -0.146 -3.44 9.55 DA SP0413-077 1,10
HZ 7 04 30 57.0 +12 36 27 +0.01 0.0 14.29 DA SP0430+126 1
HZ 15 04 37 56.0 +08 35 00 12.59 B5 SP0437+085 2
HZ 14 04 38 15.6 +10 53 56 +0.007 +0.01 13.94 DA SP0438+108 1
G191-B2B 05 01 31.5 +52 45 52 11.81 DAwk SP0501+527 1,11
G99-37 05 48 45.6 -00 11 16 +0.007 +0.20 14.51 DGp SP0548-001 1
Hiltner 600 06 42 37.2 +02 11 26 10.42 B1V SP0642+021 2
He 3 06 44 14.8 +37 35 03 -0.018 -0.91 12.05 DA SP0644+375 1,12
L745-46A 07 38 02.1 -17 17 22 +0.078 -0.57 12.91 DF SP0738-172 1,13
BD+08o 2015 08 13 01.1 +07 46 29 -0.012 -0.17 10.39 G2V SP0813+077 2
LDS 235 08 45 13.3 -18 48 46 -0.008 -0.05 15.66 DB SP0845-188 1
G47-18 08 56 11.2 +33 08 54 -0.027 0.0 15.18 SP0856+331 1
SA29 130 09 43 29.5 +44 08 31 0.000 +0.29 13.22 DA SP0943+441 1,14
HD 84937 09 46 12.0 +13 59 17 +0.027 -0.79 8.27 sdF SP0946+139 4,15
Feige 34 10 36 41.0 +43 21 49 11.24 sdO SP1036+433 2
L970-30 11 05 27.8 -04 52 51 -0.002 -0.43 12.97 DA SP1105-048 1,16
Ton 573 11 07 18.5 +26 35 12 +0.007 -0.11 15.83 DB SP1107+265 1,17
Ross 627 11 21 38.7 +21 38 05 -0.072 +0.02 14.12 DA,F SP1121+216 1,18
GD 140 11 34 27.8 +30 04 35 -0.01~ 0.0~ 12.41 DAn SP1134+300 1
Feige 56 12 04 13.8 +11 56 54 0.000 +0.03 11.11 B5p SP1204+119 2,35
HZ 29 12 32 28.5 +37 54 15 +0.002 +0.02 14.16 DBp SP1232+379 1,19
HZ 43 13 14 00.6 +29 21 49 -0.010 -0.08 13.03 DAwk SP1314+293 1,20
HZ 44 13 21 19.0 +36 23 37 -0.004 +0.03 11.67 sdO SP1321+363 1
Wolf 485A 13 27 39.8 -08 18 38 -0.074 -0.42 12.22 DA SP1327-083 1,21
Grw+70 5824 13 37 38.4 +70 32 20 -0.027 -0.02 12.87 DA SP1337+705 1
Feige 92 14 09 41.5 +50 21 07 -0.003 0.00 11.62 Bp SP1409+503 2,35
Feige 98 14 36 03.9 +27 42 30 +0.007 -0.03 11.84 B7 SP1436+277 2,35
BD+26 2606 14 46 50.2 +25 54 53 +0.000 -0.35 9.66 sdF SP1446+259 4,22
GD 190-193 15 42 03.8 +18 16 13 +0.003 -0.10 14.66 DB SP1542+182 1
BD+33 2642 15 50 02.9 +33 05 48 10.88 B2IVp SP1550+330 2
G138-31 16 25 30.0 +09 19 16 -0.007 -0.46 16.12 DA7 SP1625+093 3
Ross 640 16 26 39.3 +36 52 12 -0.042 +0.74 13.82 DFp SP1626+368 1,23
Kopff 27 17 41 28.4 +05 26 04 10.31 A3V SP1741+054 2
Grw+70 8247 19 00 39.0 +70 35 05 +0.019 +0.52 13.12 SP1900+705 1,24
BD+25 3941 19 42 21.9 +26 06 01 0.000 -0.03 10.36 B1.5V SP1942+261 2,35
BD+40 4032 20 06 40.0 +41 06 15 10.45 B2III SP2006+411 2
G24-9 20 11 29.3 +06 34 06 -0.017 -0.58 15.70 DQ7 SP2011+065 3,25
Wolf 1346 20 32 14.0 +24 53 57 -0.030 -0.55 11.54 DA SP2032+248 1,26
Grw+73 8031 21 26 43.4 +73 25 52 +0.010 -0.32 12.75 DA SP2126+734 1,27
LDS 749 B 21 29 41.2 +00 01 56 +0.022 +0.05 14.70 DB SP2129+000 1,28
L1363-3 21 40 22.5 +20 46 46 -0.019 -0.68 13.28 DC SP2140+207 1,29
L930-80 21 44 57.5 -07 58 02 +0.024 -0.16 14.88 DB SP2144-079 1,30
BD+28 4211 21 48 57.0 +28 37 48 10.56 sdOp SP2148+286 2
BD+17 4708 22 09 05.8 +17 50 42 +0.036 +0.05 9.41 sdF SP2209+178 4,31
G157-34 23 11 50.9 -06 49 02 -0.023 -0.16 15.35 DQ6 SP2311-068 3,32
Feige 110 23 17 23.5 -05 26 23 11.88 sdO SP2317-054 2,33
GD 248 23 23 35.8 +15 43 55 -0.003 -0.09 15.10 DQ5? SP2323+157 3
L1512-34 23 41 21.0 +32 16 10 -0.018 -0.06 12.92 DA SP2341+322 1,34
1: Oke,J.B.,1974, Ap.J.Suppl., 27, 21.
2: Stone,R.P.S., 1977, Ap.J. 218, 767.
3: Filippenko,A.V.and Greenstein,J.L., 1984, P.A.S.P. 96, 530.
4: Oke, J.B.& Gunn, J.E., 1983, Ap.J. 266, 713.
flux magnitudes given to 12,000Å.
5: Alias LTT 300, L795-44.
6: Alias LTT 888, LFT 142, ROA5 64. (= Roy. Obs. Ann. 5,
``Catalogue of Stars within twenty-five parsecs of the Sun'',
Star number 64).
7: Alias BD+25 495, LTT11021.
Position and proper motion from CAMC.
8: Alias G8-8
9: Alias LP414-101,GH7-112
10: Alias SAO131065, BD-7 781, G160-60, ADS 3093B,
LFT 339, ROA5 166B.
11: Red companion star 77 arcseconds separation.
12: Alias G87-7, LFT 487, ROA5 246.
13: Alias LTT 2915, LFT 543, ROA5 283A.
14: Alias LTT 12591.
15: Alias BD+14 2151, LTT 12605.
16: Alias G163-50, LTT 4099.
17: Alias L1403-49, LTT 13002, GD128.
18: Alias G120-45, LFT 800, LTT 13087, ROA5 427.
19: Alias AM CVn.
20: Alias L1409-4.
21: Alias BD-7 3632, G14-58, LFT 1014, ROA5 515.
22: Alias LTT 14382.
23: Alias G180-57, LFT 1280, ROA5 9564, Gl 626.2 (=Gliese, W., 1969.
Catalogue of Nearby Star, 1969 Edition)
24: Alias LTT~15585,~LFT~1446,~ROA5~742.
25: Alias LTT15921.
26: Alias G186N-31,~LFT~1554,~ROA5~794.
27: Alias LTT~18524,~Gl~828.5,~ROA5~9743.
28: Alias G26N-10,~LTT 16294.
29: Alias G126-27, G145-63, LFT 1655, LHS 3703, LTT 16348, LP 458-64.
30: Alias LTT 8702.
31: Alias LTT 16493.
32: Alias LTT 9427, L935N-50.
33: Alias Gl 894.3
34: Alias L1512-34B, G130N-5, Gl 905.2B, LTT 16991, ROA5 9838B.
35: Proper motion measured using POSS and Herstmonceux Astrographic plates.