2008A&A...490..113G -
Astronomy and Astrophysics, volume 490, 113-123 (2008/10-4)
The X-ray luminosity of solar-mass stars in the intermediate age open cluster NGC 752.
GIARDINO G., PILLITTERI I., FAVATA F. and MICELA G.
Abstract (from CDS):
While observational evidence shows that most of the decline in a star's X-ray activity occurs between the age of the Hyades (∼ 8x108yr) and that of the Sun, very little is known about the evolution of stellar activity between these ages. To gain information on the typical level of coronal activity at a star's intermediate age, we studied the X-ray emission from stars in the 1.9Gyr old open cluster NGC 752. We analysed a ∼140ks Chandra observation of NGC 752 and a ∼50ks XMM-Newton observation of the same cluster. We detected 262 X-ray sources in the Chandra data and 145 sources in the XMM-Newton observation. Around 90% of the catalogued cluster members within Chandra's field-of-view are detected in the X-ray. The X-ray luminosity of all observed cluster members (28 stars) and of 11 cluster member candidates was derived. Our data indicate that, at an age of 1.9Gyr, the typical X-ray luminosity of the cluster members with M=0.8-1.2M☉ is LX=1.3x1028erg/s, so approximately a factor of 6 less intense than that observed in the younger Hyades. Given that LX is proportional to the square of a star's rotational rate, the median LX of NGC 752 is consistent, for t>1Gyr, to a decaying rate in rotational velocities vrot∝t–α with α∼ 0.75, steeper than the Skumanich relation (α≃0.5) and significantly steeper than observed between the Pleiades and the Hyades (where α<0.3), suggesting that a change in the rotational regimes of the stellar interiors is taking place at t∼1Gyr.
Abstract Copyright:
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Journal keyword(s):
Galaxy: open clusters and associations: individual: NGC 752 - stars: coronae - stars: rotation - X-rays: stars
VizieR on-line data:
<Available at CDS (J/A+A/490/113): table6.dat table7.dat>
Nomenclature:
Table 6: [GPF2008] Chandra NNN (Nos 1-262). Table 7: [GPF2008] XMM NNN (Nos 1-145).
Status at CDS
:
All or part of tables of objects could be ingested in SIMBAD with priority 2.
Simbad objects:
32
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