2 Sample selection

From the HIPPARCOS "resolved variable'' catalog all stars were selected classified as "DCEP'' (219 stars), "DCEPS'' (31 stars), and "CEP'' (23 stars). This number is consistent with the quoted number of 270 Cepheids in the HIPPARCOS Input Catalog (ESA 1989), and the discovery of 3 new Cepheids (CK Cam, V898 Cen and V411 Lac). These 273 stars were correlated with the electronic database of [21, Fernie et al. (1995).] An error was detected in the HIPPARCOS catalog as HIC 45949 is associated there with W Car, whereas the correct association is V Vel. Ten stars were not found in that catalog. Comparison with the electronic database of [41, Welch (1997),] six of them (EN Tra, KL Aql, V733 Aql, BB Her, T Ant, BB Gem) are classified as Type II Cepheids, and KZ Pup is in fact a RR Lyrae variable (see the General Catalog of Variable Stars, [28, Kholopov et al. 1985).] These are excluded.

For CK Cam the intensity-mean magnitudes are calculated (in the way described below) from data in [12, Berdnikov et al. (1996),] resulting in <B> = 6.560, <V> = 7.541 and <B-V> = 0.990. As no intensity-mean values for V and B-V exist in the literature the values listed in the HIPPARCOS catalog have been adopted for the other objects (V411 Lac, V898 Cen). Periods also come from HIPPARCOS. At this point the carbon-rich CH-like Cepheid V553 Cen is discarded.

The electronic database of [21, Fernie et al. (1995)] was also cross-correlated with the SIMBAD catalog, to search for Cepheids in HIPPARCOS which are not in the "resolved variable'' catalog. Seven were found, of which one (BD Cas = HIC 796 = Fernie et al. nr. 130.3) is classified as a Type II Cepheid by Fernie et al.. Of the remaining six, two (AU Peg, $\kappa$ Pav) are not listed in Fernie et al. and are classified as Type II in the database of Welch, and hence excluded.

This leaves 270 stars that may be considered Type I Cepheids. As a next step, 10 stars are removed that are classified as Double-Mode Cepheids in Fernie et al. (GZ Car, TU Cas, VX Pup, AP Vel, Y Car, UZ Cen, BK Cen, U Tra, BQ Ser, EW Sct).

  

Table 1: Intensity-mean I-band data

 

Table 1: continued

 

Table 1: continued

 

Table 1: continued

 

Table 1: continued

Next, stars with an unreliable solution in the HIPPARCOS catalog are removed. Criteria are a large fraction of "Data-Points-Rejected'' (DPR, field H29), and/or a large value for the "Goodness-of-Fit (GOF, field H30). The introduction to the HIPPARCOS and Tycho catalogues (ESA 1997) only mentions that a "large'' value of DPR indicates a model mismatch without quoting a specific value, and that values of GOF larger than 3 usually indicate a bad fit to the data. Often these stars are also flagged as having a "Number-of-Components (nc, field H58) of 2, indicating a binary system. Stars removed on the basis of their DPR and/or GOF flags are: UX Per (DPR=36, GOF=5.30, nc=2), RW Cam (DPR=12, GOF=2.27, nc=2), BM Pup (DPR=6, GOF=5.75, nc=2), HK Car (DPR=8, GOF= 2.37, nc=2), SU Cru (DPR=20, GOF=2.09, nc=2), SY Nor (DPR=8, GOF=3.23, nc=1), TW Nor (DPR=8, GOF = 2.83, nc=1). In the remaining sample all objects have DPR $\le 7$; the two stars with DPR=7 have GOF < 1.32. There are 2 stars with GOF >3.0, however with DPR of only 0 and 2%, that were therefore kept.

Y Lac (DPR=8, GOF=4.44, nc=1) and RY Sco (DPR =13, GOF=1.94, nc=1) are special as their DPR and/or GOF values in the HIPPARCOS catalog indicate an unreliable solution, and would have been discarded for this reason. However, both are among the stars re-analysed by [19, Falin & Mignard (1999)] using software from the HIPPARCOS FAST consortium but adding additional data, in particular related to multiplicity. The solution they obtain is remarkably better, with for Y Lac values of DPR = 0 and GOF = -0.13 and for RY Sco they derive DPR = 0, GOF = 1.06. This is solely due to the fact that duplicity was allowed for. For Y Lac the binary component is at 2.6$^{\prime\prime}$ distance and has a magnitude difference of 3.0, for RY Sco these numbers are 14.4$^{\prime\prime}$ and 2.4 mag, respectively. None of the other Cepheids in the sample are in Falin & Mignard (1999).

There remain seven stars for which Fernie et al. do not list the intensity-mean V and B-V. DP Vel is discarded (as was done by FC) because the photometric data are too sparse, LL Pup, LR Pup and VV CMa because no B-V is listed in the HIPPARCOS catalog (the Welch database does not list references to any photometry either). For HL Pup, FN Vel and LX Pup, V and B-V are taken from HIPPARCOS.

There remain 248 stars of which 22 are classified as overtone pulsators in the Fernie et al. database. Recently, [34, Sachkov (1997)] identified some new overtone pulsators; FN Aql, V1162 Aql, SU Cas, X Lac, SZ Tau are in our list and not identified as overtone pulsators by Fernie et al. Furthermore, V473 Lyr is a second overtone pulsator based on the analysis of [40, Van Hoolst & Waelkens (1995)] and [1, Andrievsky et al. (1998)] and we have added four more overtone pulsators (IR Cep, BP Cir, AV Cir, DX Gem) from [2, Antonello et al. (1990).] In total there are therefore 32 overtone pulsators and 216 fundamental mode pulsators in the sample.