Other
Scientific paper
Nov 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004phdt........19b&link_type=abstract
Thesis (PhD). HARVARD UNIVERSITY, Source DAI-B 65/05, p. 2450, Nov 2004, 140 pages.
Other
7
Scientific paper
We study h and χ Persei, a pair of young open clusters, using optical (UBV) and infrared (JHK) photometry, plus optical spectra of over 1600 stars. Our spectroscopic survey is complete to V = 15.2 within 12.5' of the cluster centers. Using an automated type-assignment routine, we derive spectral types from the spectra. The accuracy of this method is comparable to that obtained by visual typing. We identify 32 Be stars in our spectroscopic sample; some have low Hα emission strength. Seven of these are new identifications; seven others are confirmations of Be stars previously identified using photometry. Five of the observed Be stars show significant Hα profile variations from epoch to epoch. We show that spectral indices yield physical characteristics of the HII emission region. We infer Hα:Hβ flux ratios of 2 5 and observe a linear relationship between Hα emission and J-K color. We measure an extinction to the clusters of AV = 1.66 mag. We measure cluster centers α(2000) = 2h 18m 56.4s ± 3.0s, δ(2000) = 57°8' 25' ± 23' and α(2000) = 2h 22m 4.3s ± 2.9s, δ(2000) = 57°8' 35' ± 25', for h and χ Persei, respectively. We fit a modified Hubble law to the stellar positions and measure core radii of 1.9 pc and 2.4 pc. Integration of the Miller-Scalo IMF suggests cluster masses of 5500 M&sun; and 4300 M&sun; and central densities of 27 M&sun; pc-3 and 50 M&sun; pc-3. We find mass segregation in h Persei, but not in χ Persei. Examination of the dynamical timescales suggests that the mass segregation must be in part primordial. We determine the cluster ages, log t = 7.05 and log t = 7.1, for h + χ Persei using M supergiants. Using the HR Diagram, we measure IMF slopes of -2.47 ± 0.12 and -2.30 ± 0.15 for h and χ Persei. These slopes are consistent with the Salpeter IMF. The slope in h Persei is shallower towards the cluster center, consistent with mass segregation. Mysteriously, while h Persei is younger, it is also more dynamically evolved.
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