Chandra and Multiwavelength Study of Pevatron Candiate HESS J1702-420A

Abstract

Aims: HESS J1702-420A is a promising Galactic PeVatron candidate whose physical nature remains unknown. Previous XMM-Newton observations revealed hard, apparently extended X-ray emission from XMMU J170147.3-421407, offset from the center of the TeV source, suggesting a possible pulsar wind nebula (PWN) association. We aim to resolve its X-ray morphology, investigate compact-object candidates in the field, and assess their possible association with HESS J1702-420A. Methods: We obtained three new ACIS-I observations from the Chandra X-ray observatory (CXO) with a total exposure of 50.4 ks. We performed imaging, source detection, spectral and variability analyses, and multiwavelength (MW) machine-learning (ML) source classification. Neutron star (NS) candidates were further investigated using deep near-infrared and radio imaging. Results: The Chandra observations resolve XMMU J170147.3-421407 into a faint point-like source, Src11 (CXO J170144.5-421415), and asymmetric diffuse emission comprising eastern and western lobes. The X-ray spectral, variability, and MW properties of Src11 and the diffuse emission are consistent with those commonly observed in pulsar/PWN systems, further supported by the ML classifications. However, the asymmetric diffuse morphology is unlike a typical bow-shock/tail or jet/torus PWN, and the $\sim7'$ offset from HESS J1702-420A makes a firm physical association difficult to establish. A possible shell-like radio structure north-west of Src11 may indicate a more complex PWN/SNR environment. Other NS candidates are less consistent with a pulsar/PWN interpretation, making Src11 the most compelling candidate in the field.