DATABASE OF GALACTIC CLASSICAL CEPHEIDS

The following links will guide you through the documentation of the database.

• Introduction
  
• Choice of stars and data
  
• Description of individual files
  
• References
  

The data can be accessed by using your browser find function to search the following tables:

• Positional Data
• Mean Values and Amplitudes
• Colour Excess
• Physical Data

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.

(Return to top)

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 different kind.

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 homogeneity. 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.

(Return to top)

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.

1. HD: The Henry Draper catalogue number of the Cepheid where it exists
.
2. SAO: The Smithsonian Astrophysical Observatory catalogue number
.
3. RAH, RAM, RAS: 1950 values of right ascension hours, minutes, and seconds taken from the GCVS.
4. DECD, DECM: 1950 values of declination degrees and arcminutes taken from the GCVS.
5. L, B: Galactic longitude and latitude taken from the GCVS. This is the , b system.

1. V_AMPL: The amplitude of the V light curve determined from an intensity analysis.
2. B_AMPL: The amplitude of the B light curve determined from an intensity analysis.
3. BV_AMPL: The amplitude of the B-V colour curve determined from a magnitude analysis.
4. RV_AMPL: The pulsational amplitude of the radial velocity curve in km.s. This is not known for every star for which a radial velocity mean is given, since some sources quote the latter only.
5. V_MAGMEAN: The mean V magnitude determined from a Fourier fit without first converting the magnitudes to intensities.
6. 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.)
7. B_MAGMEAN: The mean B magnitude determined from a Fourier fit without first converting the magnitudes to intensities.
8. B_INTMEAN: The mean B magnitude determined from a Fourier fit after first converting the magnitudes to intensities.
9. BV_MAGMEAN: The mean B-V obtained by a Fourier fit to the observed values expressed in magnitudes.
10. BV_INTMEAN: The value of B_INTMEAN - V_INTMEAN.

1. FE1: The colour excess taken from Fernie (1990).
2. 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.
3. LS: Values from Laney and Stobie (1993).
4. JP: Values from Janot-Pacheco (1976).
5. KR: Values from Kron and Roach (1979).
6. 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.
7. PB: Values from Parsons and Bell (1975).
8. TLE: Values from Turner, Leonard, and English (1987).
9. DE: Values from Dean (1981).
10. PE: Values from Pel (1978).
11. FM: Values from Feltz and McNamara (1980).
12. EG: Values from Eggen (1985).
13. HA: Values from Harris (1981).
14. YT: Values from Yakimova, Nikolov, and Ivanov (1975).
15. SACK: Values from Schecter, Auruch, Caldwell, and Keane (1992) transformed from E(H-K) by E(B-V) = 5.03 E(H-K).
16. EG2: Values from Eggen (1996), transformed from E(b-y) by E(B-V) = E(b-y)/0.78.
17. BERS: Values from Bersier (1996).

1. 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.
2. V_INTMEAN: The intensity-mean V magnitude, <V>, obtained by converting the observed magnitudes to intensities, finding the mean value from a Fourier fit, and converting that mean intensity back to a magnitude.
3. BV_INTMEAN: The colour index derived from the intensity-mean values <B> - <V>. Magnitude-mean values of V and B-V are in the Mean Values and Amplitudes file.
4. EBV: The FE1 value of E(B-V) or, if that was unavailable, the FE2 value. See the discussion above.
5. 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 different value.
6. MV: The (intensity) mean absolute V magnitude calculated from Fernie's (1992) relation: <Mv> = -2.902 log P - 1.203. See the discussion above.
7. 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.
8. Z: The distance in parsecs from the Galactic plane, derived by multiplying the distance by sin b.
9. RV_MEAN: The systemic radial velocity in km.s determined from a Fourier fit to the radial velocity curve of a Cepheid.
10. RADIUS: The radius of the star in solar radii derived from a Baade-Wesselink type analysis. We have used only the extensive determinations 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).
11. 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 been attempted.
12. 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 /P ) = 0.717 - 0.030 log P (Christensen-Dalsgaard and Petersen 1995) and used to calculate the distance and z values.
13. 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).