The X-ray emissivity ( i.e. , luminosity per unit stellar mass ) of globular clusters are an important indicator of their dynamical evolution history .
Based on deep archival Chandra observations , we report a stacking analysis of 44 globular clusters ( GCs ) with 0.5-8 keV luminosities L _ { X } \lesssim 10 ^ { 35 } { ~ { } erg~ { } s ^ { -1 } } in the M 31 bulge , which are supposed to be dominated by cataclysmic variables ( CVs ) and coronally active binaries ( ABs ) .
We obtain a significant detection at 5 \sigma level in 0.5-8 keV band .
The average X-ray luminosity per GC and the average X-ray emissivity are determined to be 5.3 \pm 1.6 \times 10 ^ { 33 } ~ { } erg~ { } s ^ { -1 } and 13.2 \pm 4.3 \times 10 ^ { 27 } ~ { } erg~ { } { s ^ { -1 } ~ { } M ^ { -1 } _ { \odot } } , respectively .
Both of these values are consistent with those of MW GCs .
What ’ s more , the measured emissivity of M31 GCs is also consistent with that of the MW field stars .
Massive GCs have X-ray luminosities which are marginally higher with less massive ones .
Massive GCs also show a lower emissivity ( 4.5 \pm 2.4 \times 10 ^ { 27 } { ~ { } erg~ { } s ^ { -1 } ~ { } M ^ { -1 } _ { \odot } } ) than less massive ones ( 15.0 \pm 7.8 \times 10 ^ { 27 } { ~ { } erg~ { } s ^ { -1 } ~ { } M ^ { -1 } _ { \odot } } ) , which is consistent with the scenario that the ( progenitors of ) CVs and ABs were more efficiently destructed via stellar encounters in the more massive GCs .
No dependence of the X-ray emissivity on GC color or on the projected galactocentric distance of GCs were found .