English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

AIMS. While observational evidence shows that most of the decline in a star'sX-ray activity occurs between the age of the Hyades (~8 x 10^8 yrs) and that ofthe Sun, very little is known about the evolution of stellar activity betweenthese ages. To gain information on the typical level of coronal activity at astar's intermediate age, we studied the X-ray emission from stars in the 1.9Gyr old open cluster NGC 752. METHODS. We analysed a ~140 ks Chandraobservation of NGC 752 and a ~50 ks XMM-Newton observation of the same cluster.We detected 262 X-ray sources in the Chandra data and 145 sources in theXMM-Newton observation. Around 90% of the catalogued cluster members withinChandra's field-of-view are detected in the X-ray. The X-ray luminosity of allobserved cluster members (28 stars) and of 11 cluster member candidates wasderived. RESULTS. Our data indicate that, at an age of 1.9 Gyr, the typicalX-ray luminosity of the cluster members with M=0.8-1.2 Msun is Lx = 1.3 x 10^28erg s^-1, so approximately a factor of 6 less intense than that observed in theyounger Hyades. Given that Lx is proportional to the square of a star'srotational rate, the median Lx of NGC 752 is consistent, for t > 1 Gyr, to adecaying rate in rotational velocities v_rot ~ t^-alpha with alpha ~ 0.75,steeper than the Skumanich relation (alpha ~ 0.5) and significantly steeperthan observed between the Pleiades and the Hyades (where alpha < 0.3),suggesting that a change in the rotational regimes of the stellar interiors istaking place at t ~ 1 Gyr.

The X-ray luminosity of solar-mass stars in the intermediate age open cluster NGC 752