Proposal Details - 1020005
Hard X-ray study of the ultra-compact X-ray binary 4U 0614+091 (Chenevez)

Proposal Abstract

We propose a dedicated INTEGRAL monitoring program of the ultra-compact X-ray binary and micro-quasar 4U0614+091 to study its emission properties in hard X-rays. This source is situated in a region of the sky well outside theGalactic bulge and is thus one of the low-mass X-ray binaries being least observed by INTEGRAL. However, 4U0614+091 is an interesting target for several reasons: not only it harbours the closest active X-ray burster, it exhibitsvariations at very different time scales and over the whole electromagnetic spectrum, such as synchrotron jet emission,X-ray flaring states, and thermonuclear X-ray bursts. Moreover, the high energy persistent emission from the source ischaracterised by a particularly hard (non thermal) X-ray tail. Therefore, we want to exploit the INTEGRAL instrumentationto survey the dynamical behaviour of the source, and better describe its spectrum in hard X-rays. The monitoringcampaign we propose (for a total of 500 ks exposure) has been approved for AO-9, but have not yet been performed. Itwill indeed make it possible to follow the evolution of the long term persistent emission variability, as well as toinvestigate the activity of shorter time scale processes. In fact, 4U 0614+091 is also known for having exhibited usualshort X-ray bursts, an hours-long superburst, and several intermediately long bursts with superexpansion of the neutronstars photosphere. The proposed observing strategy will for instance allow us to relate the bursting behaviour of thesource to its broadband emission, and especially to its flaring activity on time scales of days to weeks.The present proposal does also request joint XMM and INTEGRAL observations.

Observation Strategy (Recommended by TAC)

Total of 500 ks using a random hexagonal pattern, centered on RA, Dec (J12000.0 in degrees) = 94.280, 9.137 (l, b = 200.877, -3.364 degrees). The time will be split into ten 50.4 ks observations (4 hexagonal patterns each with exposure time of 1800 s per pointing) approximately regularly distributed along the visibility periods in 2012 (February - April and August - October). Two of these observations will be accompanied by contemporaneous 10 ks XMM-Newton observations (i.e., a total of 20 ks approved XMM-Newton time).

Proposal grade: B

Data Rights (Recommended by TAC)

Data rights were granted for 4U 0614+091.

Exposure Map

The exposure maps are in galactic coordinates using the Aitoff projection and units of seconds, and the colour scale is indicated at the bottom. The green lines provide the 50, 200, 350, 500 and 650 ksec contour.