A survey of stellar X-ray flares from the XMM-Newton serendipitous source catalogue: HIPPARCOS-Tycho cool stars

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Table 1

Summary of the 2XMM-Tycho survey characteristics.

Quantity	2XMM-Tycho
	All	Cool stars

No. of Tycho stars in 2XMM fields	~26 000	~19 000
No. of 2XMM sources matched with Tycho stars	3042	2357
No. of 2XMM detections matched with Tycho stars	4772	3499
No. of 2XMM sources with light-curves	808	611
No. of detections with light-curves	1393	933
No. of X-ray variable sources/stars	123/120	91/89
No. of variable light-curves	157	118
No. of variable light-curves after quality checking	128	96^a
No. of X-ray variable stars after quality checking	85	76^a

2XMM summed viewing time (Ms) on Tycho stars:
for all detected stars^b	119	87 (82)
for all cool stars with X-ray light-curves		29 (24)
for all stars with X-ray variability^a		3.9 (1.8)
for all stars with flares^a		3.0 (1.4)
for all stars with fully-observed flares^a		2.6 (1.2)
for all stars with flares, S:N> 10^a		2.1 (0.62)
for all stars with fully-observed flares, S:N> 10^a		1.9 (0.58)

Notes. Values in parentheses (...) relate to serendipitous observations, i.e. the star was not the target of the XMM observation.

^(a)

CVS sample;

^(b)

includes all relevant 2XMM detections not only those with light-curves. The terms “source” and “detection” are as defined in the 2XMM catalogue (Watson et al. 2009, Sect. 8.1).

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