2001/02/15 by A. Marco, Amparo Marco, G. Bernabeu +1 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1051/0004-6361:20010441
47 pages, 15 figures and 29 tables. Uses aa.cls. Accepted for publication in the Astronomy and Astrophysics
arxiv created 2001/02/15 · openalex publication_date 2001/06/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We present 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 allows us to reach early F spectral type and obtain very accurate fits to the ZAMS. We derive reddening values of for h Persei and for χ Persei. From the ZAMS fitting, we derive distance moduli and 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 and 7.3.