DAVID DUNLAP OBSERVATORY
DATABASE OF GALACTIC CLASSICAL CEPHEIDS
The following links will guide you through the documentation
of the database.
The data can be accessed by using your browser find function
to search the following tables:
Last update of this page: December 4 2003; Last update of data:
February 18 1997
The announcement of this database appeared in the International
Bulletin of Variable Stars. When referring to this work in published papers please
include the following citation:
Fernie, J.D., Beattie, B., Evans, N.R., and Seager, S. 1995, IBVS No. 4148
Original authors of this work were J.D. Fernie, Brian Beattie, Nancy
Remage Evans, and S. Seager. Please direct comments and enquiries to
Fernie (see http://www.astro.utoronto.ca/staff.html )
We present a database of over 500 classical Cepheids in the Galaxy contained
in four files. The first, Positional Data, contains
the equatorial and galactic coordinates of each star, and cross-references to
HD and SAO numbers where they exist. The second, Mean Values and
Amplitudes, provides mean values of Johnson B and V magnitudes,
both as magnitude- and as intensity-means, the corresponding B-V values, the
amplitudes in B, V, and B-V, and the radial velocity pulsational amplitudes.
The third file, Colour Excess, lists major determinations
of E(B-V) and the average for each Cepheid where possible. The fourth file,
Physical Data, brings together some material from
the other files, as well as listing period, absolute magnitude, distance, height
above the galactic plane, mean radius, mean radial velocity, and notes regarding
binarity, cluster membership, etc.
No individual observations are given. For these see the
McMaster Cepheid Photometry and Radial Velocity Data Archive, an extensive
compilation of observational data maintained by Doug Welch.
A database of galactic Cepheids
belonging to binary and multiple systems is maintained by Laszlo Szabados.
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Choice of stars and data:
Our list of classical Cepheids initially comprised stars labelled
DCEP, DECPS, CEP, or CEP(B) in the 4th edition of the General Catalogue
of Variable Stars. A SIMBAD search was conducted on each of these stars
principally to find data sources, but this also led to the weeding of stars that
in our judgement are not classical Cepheids, either through being faint and
at high galactic latitude, or for which recent studies have suggested an
alternative designation as being more likely. We were further guided in this
by Harris' listing of Population II Cepheids (Harris 1985). Also eliminated
were stars for which no data other than coordinates could be found. Our list
is therefore far from definitive, although we believe the bulk of known
Galactic classical Cepheids are in it, as are-no doubt-a few stars of a
We decided to restrict the photometric information in the
database to Johnson B and V since there is much more BV information
available than in any other photoelectric system. (No photographic data
have been used.) Limited labour resources also dictated a restricted range
of bands. However, although direct BV measurements were preferred,
where they were lacking we did use measurements in other systems,
notably the Stromgren and Walraven systems, where transformations to BV
could be done with reasonable reliability.
Our limited labour resources also prevented us from combining all
the data available for each star into the 'best' light-, colour-, and
velocity-curves for Fourier analysis. Instead, our policy has been to
favour the most
extensive publications (e.g. Berdnikov, Caldwell and Coulson, Eggen,
Moffett and Barnes, and Pel) as our prime sources in order to maximize
Neither were we in a position to enter into investigations of
zero-point and other
differences between observers; data have been taken at their face value
unless differences were glaringly obvious.
We adopted the same principle of maximizing homogeneity by
favouring the most extensive publications regarding E(B-V). The catalogue of
Fernie (1990) and values derived from the method given in Fernie (1994),
which are tied to the 1990 catalogue system, were adopted where a single
value of E(B-V) was needed to calculate distance. The
Colour Excess file, however,
gives values from all major compilations published since 1975, and workers
can easily repeat distance calculations using whichever field in the
Colour Excess file they prefer.
The period-luminosity law adopted for calculating distance was that
of Fernie (1992). This produces Mv values that agree to within 0.03 mag
for 3 P 50
with those from
the Madore and Freedman (1991) and Walker
(1988) P-L relations; agreement with the P-L relation of Gieren et al (1993)
is not quite as good. No correction for metallicity was made.
In the case of s-Cepheids (first harmonic pulsators), noted as such in
the Physical Data file, the period has been
adjusted to the fundamental period before calculating absolute
magnitude, distance, etc.
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Description of individual files:
The first field in each file is an identification number.
Use of decimal fractions here, with sorting on this field, allows
the interpolation of newly added stars to keep the
traditional order of variable star nomenclature.
The second field is always the variable star name.
Mean Values and Amplitudes
- HD: The Henry Draper catalogue number of the Cepheid where it
- SAO: The Smithsonian Astrophysical Observatory catalogue number.
- RAH, RAM, RAS: 1950 values of right ascension hours, minutes,
and seconds taken from the GCVS.
- DECD, DECM: 1950 values of declination degrees and arcminutes
taken from the GCVS.
- L, B: Galactic longitude and latitude taken from the GCVS. This is
- V_AMPL: The amplitude of the V light curve determined from an
- B_AMPL: The amplitude of the B light curve determined from an
- BV_AMPL: The amplitude of the B-V colour curve determined from a
- RV_AMPL: The pulsational amplitude of the radial velocity curve in
This is not known for every star for which a radial velocity mean is
given, since some sources quote the latter only.
- V_MAGMEAN: The mean V magnitude determined from a Fourier
fit without first converting the magnitudes to intensities.
- V_INTMEAN: The mean V magnitude determined from a Fourier fit
after first converting the magnitudes to intensities. (See below in
the descriptions of Physical Data fields.)
- B_MAGMEAN: The mean B magnitude determined from a Fourier
fit without first converting the magnitudes to intensities.
- B_INTMEAN: The mean B magnitude determined from a Fourier fit
after first converting the magnitudes to intensities.
- BV_MAGMEAN: The mean B-V obtained by a Fourier fit to the
observed values expressed in magnitudes.
- BV_INTMEAN: The value of B_INTMEAN - V_INTMEAN.
- FE1: The colour excess taken from Fernie (1990).
- FE2: The colour excess derived from B-V at maximum light, the
period, and V-amplitude as described in Fernie (1994). This is
generally given only where FE1 is lacking, since FE2 is calibrated
against FE1, and the labour involved precluded finding FE2 for every
star. However, there is an overlap for about 40 randomly selected
stars to check that the two systems are indeed the same.
- LS: Values from Laney and Stobie (1993).
- JP: Values from Janot-Pacheco (1976).
- KR: Values from Kron and Roach (1979).
- DWC: Values from Dean, Warren, and Cousins (1987). These are
the excesses determined by the authors themselves and do not
include results from other authors quoted in the paper.
- PB: Values from Parsons and Bell (1975).
- TLE: Values from Turner, Leonard, and English (1987).
- DE: Values from Dean (1981).
- PE: Values from Pel (1978).
- FM: Values from Feltz and McNamara (1980).
- EG: Values from Eggen (1985).
- HA: Values from Harris (1981).
- YT: Values from Yakimova, Nikolov, and Ivanov (1975).
- SACK: Values from Schecter, Auruch, Caldwell, and Keane (1992)
transformed from E(H-K) by E(B-V) = 5.03 E(H-K).
- EG2: Values from Eggen (1996), transformed from
E(b-y) by E(B-V) = E(b-y)/0.78.
- BERS: Values from Bersier (1996).
- PERIOD: This is the value given in the GCVS except for a few
cases where observers have reported significant corrections. It
must also be remembered that for some (usually long period)
Cepheids there can be important secular changes in the period.
Users may wish to consult Szabados (1991) and references therein
regarding individual cases. The period (and other data) given for
double-mode Cepheids refers to the fundamental mode.
- V_INTMEAN: The intensity-mean V magnitude,
converting the observed magnitudes to intensities, finding the mean
value from a Fourier fit, and converting that mean intensity back to
- BV_INTMEAN: The colour index derived from the intensity-mean
Magnitude-mean values of V and B-V are in the
Mean Values and Amplitudes file.
- EBV: The FE1 value of E(B-V) or, if that was unavailable, the FE2
value. See the discussion above.
- V_AMP: The amplitude of the V light curve in magnitudes, derived
from the intensity analysis when finding V_INTMEAN. This is only
approximate in the case of double-mode Cepheids, where in most cases
the amplitude is simply from a fit to the data folded on the
fundamental period; rigorous analysis would likely yield a somewhat
- MV: The (intensity) mean absolute V magnitude calculated from
Fernie's (1992) relation: <Mv> = -2.902 log P - 1.203. See the
- DIST: The distance of the Cepheid from the sun in parsecs
computed from the V_INTMEAN, EBV, and MV fields. The ratio of total
to selective extinction was held fixed at 3.1. Some entries appear
as having 4 or even 5 significant figures, which of course is not the
case, but this format is more convenient in a table than is scientific
format. We have simply had the distances rounded to the nearest
parsec to preserve precision for the very nearest Cepheids.
- Z: The distance in parsecs from the Galactic plane, derived by
multiplying the distance by sin b.
- RV_MEAN: The systemic radial velocity in
determined from a Fourier fit to the radial velocity curve of a Cepheid.
- RADIUS: The radius of the star in solar radii derived from a
Baade-Wesselink type analysis. We have used only the extensive
by Gieren, Barnes and Moffet (1993) and Laney and Stobie
(1995). Radii for classical Cepheids generally can be found from
period-radius relations given in those papers or in Fernie (1992).
- BIN: An O in this column indicates that the star shows confirmed
orbital binary motion. Evans (1995) gives details. This naturally implies
that the mean radial velocity is variable. A C indicates that the star has
a blue companion detected by IUE. Evans (1992a) has systematically searched
all classical Cepheids brighter than <V> = 8.0 (except V737 Cen and
EW Sct) with IUE for such companions, so that lack of a C for such
stars can be
taken to mean that no companion bright enough to be detected by IUE is
present. An entry of C may imply that the photometric data for the Cepheid
have been contaminated by the companion, but no correction for this has
- 1H?: An s in this field indicates a star generally accepted as
pulsating in the first harmonic. The list is based on Poretti (1994)
and references therein. Fundamental periods for these
stars have been calculated from (P
) = 0.717 - 0.030 log P
and Petersen 1995) and used to calculate the distance and z values.
- NOTES: This column indicates known double-mode Cepheids,
members of open clusters or associations, and post-GCVS cases of
recently found Cepheids. An entry of IUE indicates that an estimate
of <Mv> derived from a binary companion is available in the
literature (Evans 1991, 1992b,c,d).
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Bersier, D., 1996, A&A, 308, 514
Christensen-Dalsgaard, J., and Petersen, J.O. 1995, 299, L17
Dean, J.F., Warren, P.R., and Cousins, A.W.J. 1987, MNRAS, 183, 569
Dean, J.F. 1981, MNRAS, 197, 779
Eggen, O.J. 1985, AJ, 90, 1260
_________. 1996, AJ, 111, 1313
Evans, N.R. 1991, ApJ, 372, 597
_________. 1992a, ApJ, 384, 220
_________. 1992b, ApJ, 389, 657
_________. 1992c, ApJ, 385, 680
_________. 1992d, AJ, 104, 216
_________. 1995, ApJ, 445, 393
Feltz, K.A., and McNamara, D.H. 1980, PASP, 92, 609
Fernie, J.D. 1990, ApJS, 72, 153
_________. 1992, AJ, 103, 1647
_________. 1994, ApJ, 429, 844
Gieren, W.P., Barnes III, T.G., and Moffett, T.J., 1989, ApJ, 342, 467
________________________________________________. 1993, ApJ, 418, 135
Harris, H.C. 1981, AJ, 86, 707
_________. 1985, AJ, 90, 756
Janot-Pacheco, E. 1976, A&AS, 25, 159
Kron, G.E., and Roach, F.E., 1979, in IAU Colloquium 46, Changing Trends
in Variable Star Research, ed. F.M. Bateson, J. Smak, & I.H. Urch
(Univ. of Waikato, Hamilton, NZ), p292
Laney, C.D., and Stobie, R.S. 1993, MNRAS, 263, 921
________________________. 1995, MNRAS, 274, 337
Madore, B.F., and Freedman, W.L. 1991, PASP, 103, 933
Parsons, S.B., and Bell, R.A. 1975, Dudley Obs Reports 9, 73
Pel, J.W. 1978, A&A, 62, 75
Poretti, E. 1994, A&A, 285, 524
Schecter, P.L., Auruch, I.M., Caldwell, J.A.R., and Kean, M.J.
1992, AJ, 104, 193
Szabados, L. 1991, Konkoly Obs Communications, No. 96
Turner, D.G., Leonard, P.J.T., and English, D.A. 1987, AJ, 93, 368
Walker, A.R. 1988, in The Extragalactic Distance Scale, ed. S. van den
Bergh & C.J. Pritchet, (ASP Conference Series 4), p89
Yakimova, N.N., Nikolov, N.S., and Ivanov, G.R. 1975, in
IAU Symposium 67, Variable Stars and Stellar Evolution,
ed. V.E. Sherwood & L. Plaut, p201
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THE DDO DATABASE OF GALACTIC CLASSICAL CEPHEIDS
© David Dunlap Observatory, University of Toronto, 1995