Astronomy and Astrophysics, volume 372, 477-494 (2001/6-3)
Photometric study of the double cluster h & χ Persei.
MARCO A. and BERNABEU G.
Abstract (from CDS):
We present uvbyβ CCD photometry of the central region of the double cluster h & χ Persei. We identify ≃350 stars, of which 214 were not included in Oosterhof's catalogue. Our magnitude limit V=16.5 allows us to reach early F spectral type and obtain very accurate fits to the ZAMS. We derive reddening values of E(b-y)=0.44±0.02 for h Persei and E(b-y)=0.39±0.05 for χ Persei. From the ZAMS fitting, we derive distance moduli V0-MV=11.66±0.20 and V0-MV=11.56±0.20 for h and χ Persei respectively. These values are perfectly compatible with both clusters being placed at the same distance and having identical reddenings. The shift in the main-sequence turnoff and isochrone fitting, however, show that there is a significant age difference between both clusters, with the bulk of stars in h Persei being older than χ Persei. There is, however, a significant population of stars in h Persei which are younger than χ Persei. All this argues for at least three different epochs of star formation, corresponding approximately to logt=7.0, 7.15 and 7.3.
techniques: photometric - Galaxy: open clusters and associations: individual: h Persei, χ Persei - stars: evolution - emission-line, Be - formation
VizieR on-line data:
<Available at CDS (J/A+A/372/477): table2.dat table8.dat table9.dat table14.dat>
Table 2: NGC 869 NNNN (Nos 4000-4090), NGC 884 NNNN (Nos 7001-7125) added.
Table 7: Objects 1899 et 1781 are in chi Persei, not in h Persei (NGC 884 1899 and NGC 884 1781 in SIMBAD).
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