4 Comparison with results from the MACHO survey

We searched the MACHO Variable Star Catalogue (http://wwwmacho.mcmaster.ca/Data/MachoData.html) for variables within the fields covered by our sample and classified as LPV.WoodA, LPV.WoodB, LPV.WoodC and LPV.WoodD, respectively. The catalogue released on the web includes only a subsample of all variables found in the MACHO survey. It was therefore not surprising that we did not find all stars of our sample in the released MACHO catalogue, which is probably not complete in the area we are concerned with. In total, we found 36 MACHO LPVs that are within the fields we investigated. 25 of them had counterparts in our sample. We assume that the remaining 11 stars are located on defects or borders of the CCD chips, but we did not investigate these objects further.

We applied the same analysis to the red MACHO light curves of these 25 stars. Results are listed in Table 2. The same classification was reached for 21 stars in our comparison, in two further cases either the MACHO or the AGAPEROS light curve was not of sufficient quality for the analysis. Interestingly, the two remaining objects with different classifications both show a higher degree of regularity in the MACHO data. In these cases our dataset was obviously not covering enough light cycles to reveal the regularity. We can estimate from this result that for less than 10% of the AGAPEROS light curves the regularity was not detected correctly.

22 of the LPVs in common with the MACHO catalogue agree in the main period within a few percent. The values we derived for the MACHO light curves are in good agreement with the results listed in the MACHO catalogue. However, the catalogue gives only one period for each object, so in cases we found multiple periods in our sample stars only one of them could be compared. Several of the secondary periods found in the AGAPEROS stars also agree quite well with values from the MACHO data. Very long periods could not be detected with the shorter time series of AGAPEROS data. The differences in some secondary periods illustrates the difficulty to derive a unique fit of these light curves with more than one period (see also Kerschbaum et al. 2001).

 

 

Table 2: Comparison of MACHO and EROS data.

MACHO				AGAPEROS
F.T.S. number	Period 1	Period 2	Classif.	Period 1	Period 2	Classif.
77.7549.37	(74 d)		bad data*	77 d		semireg.
77.7550.65	593 d	77 d	regular			irreg.
77.7671.284	343 d		semireg.	346 d	39 d	semireg.
78.5616.19	68 d	73 d	semireg.	67 d	82 d	semireg.
78.5737.16	120 d		regular	119 d		regular
78.5737.19	346 d	3884 d	regular	340 d		regular
78.5739.75	96 d		regular	98 d		regular
78.5861.76	287 d	160 d	semireg.			bad data
78.5981.182	193 d		regular	189 d		regular
78.5978.71			irreg.			irreg.
78.6099.145	128 d		regular	129 d		regular
78.6223.71	352 d		semireg.	338 d	52 d	semireg.
78.6343.57	128 d		regular	128 d		regular
78.6345.14	239 d	126 d	semireg.	225 d	120 d	semireg.
78.6345.30	130 d		regular	129 d	236 d	regular
78.6461.2171	437 d	58 d	semireg.	454 d	51 d	semireg.
78.6466.18	338 d		regular	327 d		regular
78.6583.23	338 d		semireg.	345 d	56 d	semireg.
78.6586.61	121 d		regular	125 d	67 d	semireg.
78.6707.35	89 d		regular	88 d		regular
78.6824.2327	150 d		semireg.	150 d	315 d	semireg.
78.6826.70	86 d		regular	86 d		regular
79.5863.25	91 d	1143 d	semireg.	92 d	274 d	semireg.

^* The blue MACHO data give a period of 74 days.

The good agreement in the classification between the AGAPEROS and the MACHO data, computed over independent data sets (1991-1994 for AGAPEROS, 1992-2000 for MACHO), strengthens the validity of our approach.