uvby photometry of open clusters

Abstract

Fur insgesamt 40 Stern im Gebiet des verfarbten offenen Haufens NGC 6871 erhielten wir eine uubv Photometric. 21 dieser Sterne klassifizierten definitely as members. From the photometric results we derived 1.2 x IO' years as the cluster age. 2440 pc as its distance. and (E(h --y ) ) = 0.348 mag as mean reddening of the cluster. From the scatter around this mean colour excess and the deviation of a subgroup of stars by more than twice the standard deviation a varible intracluster reddening in order of 0.1 mag is indicated. The value of the colour excess ratio E(h -J , )~E ( E 1 ) = 0.705 for the cluster stars leads us to the conclusion that the very broadband structure (VHS) in the spectra of the cluster stars must be very weak. Fur insgesamt 40 Stern im Gebiet des verfarbten offenen Haufens NGC 6871 erhielten wir eine urhy Photometrie. 21 dieser Sterne klassifizieren wir definitiv als Haufenmitglieder. Aus den photonietrischen Ergebnissen leiteten wir ein I laufenalter von 1.2 x 10' Jahren, eine Entfernung von 2440 pc und eine Verfiirbung ( E ( h -!,I) = 0.348 mag ab. Aus der Streuung um diesen mittleren F a r b e x A und der Tatsache. da13 eine Gruppe von Sterncn um mehr als die doppelte Standardabweichung von dieseni Wert differiert. l l D t sich eine Verfarbung innerhalb des Haufens in der Gr6Benordnung von 0.1 mag vermuten. Aus der G r 8 k des FarbexzeBverhiltnisses E(h --I.)/E(E -1 ' ) = 0.705 schliekn wir. dab die Breitbandstruktur (VHS) in den Spektren der Haufensterne nur sehr schwach ausgepragt sein kann. k'czi. ii~)n/.t: photometryopen clusters: NGC 6871 -age distance reddening .AA,4 subject cltrssjficcrtion: 153; I131.

Spectroscopy of B and Be stars in the diffuse stellar clusters NGC 6871 and NGC 6913

“…In the color-magnitude diagram this star lies in the cold giant region ( T eff = 5800 K [12]), or is a strongly reddened object of still greater luminosity embedded in a dense gas-dust cloud. It was found to be of spectral type of G2 in [12], where it was suggested that the star is not a member of the cluster. Our observations also indicate that HD 277630 is most likely not a member of the cluster.…”

“…Later [12], a study of 21 stars in the cluster yielded an average of DM = 11 m .94 ± 0 m .08, which corresponds to a distance of 2440±100 pc. Finally, the distance modulus has been estimated [13] to be 11 m .65 ± 0 m .07.…”

“…8), the rotation velocity is Vsini = 150 ± 50km/s, and a significant variability, km/s, is observed in the radial velocity. Absorption profiles of the lines have been obtained elsewhere [13,20] and the star has been assigned to the class of normal B stars [12,18,23]. The intensities of the Hβ, HeI, and other metal lines are similar to the spectrum obtained in [15] and correspond to spectral type B0.2III.…”

“…A distance module has been determined for this star (V 0 -M = 3.73) [12] which differs substantially from the average value for the cluster. Given this, we can say that this star is not a member of the cluster.…”

“…Several photometric studies of the cluster NGC 6871 have been published [7][8][9][10][11][12][13]. Spectroscopic surveys of these stars have been reported [5,6,14,15] and they have been classified spectrally [10,13,15,16].…”