Chandra Observations of the Field Containing HESS J1616–508

Abstract

We report the results of three Chandra observations covering most of the extent of the TeV γ -ray source HESS J1616–508 and a search for a lower-energy counterpart to this source. We detect 56 X-ray sources, 37 of which have counterparts at lower frequencies, including a young massive star cluster, but none of them appear to be a particularly promising counterpart to the TeV source. The brightest X-ray source, CXOU J161423.4–505738, with a flux  F 0.5–7 keV  ≈ 5 × 10 −13 erg cm −2 s −1 , has a hard spectrum that is well fit by a power-law model with a photon index Γ = 0.2 ± 0.3 and is a likely intermediate polar CV candidate. No counterparts of this source were detected at other wavelengths. CVs are not known to produce extended TeV emission, and the source is also largely offset (19′) from HESS J1616–508, making them unlikely to be associated. We have also set an upper limit on the X-ray flux of PSR J1614–5048 in the 0.5–8 keV band ( F 0.5–8 keV  < 5 × 10 −15 erg cm −2 s −1 at a 90% confidence level). This makes PSR J1614–5048 one of the least X-ray-efficient pulsars known, with an X-ray efficiency . We find no evidence supporting the association between the pulsar and the TeV source. We rule out a number of X-ray sources as possible counterparts to the TeV emission and do not find a plausible counterpart among the other sources. Lastly, we discuss the possible relation of PSR J1617–5055 to HESS J1616–508 in light of the new observations.