HESS J1640-465 and HESS J1641-463: two intriguing TeV sources in the light of new Fermi LAT observations

TL;DR

This study analyzes gamma-ray data from Fermi LAT to distinguish and characterize two nearby TeV sources, HESS J1640-465 and HESS J1641-463, revealing their spectral properties and spatial separation.

Contribution

It provides the first detailed spectral and morphological analysis of both sources using 64 months of Fermi LAT data, clarifying their gamma-ray characteristics.

Findings

HESS J1641-463 has a soft spectrum with no significant emission above 10 GeV.

HESS J1640-465's spectrum connects smoothly with H.E.S.S. data, indicating a consistent power-law shape.

Two distinct gamma-ray sources are confirmed in the region, with different spectral behaviors.

Abstract

We report on gamma-ray analysis of the region containing the bright TeV source HESS J1640-465 and the close-by TeV source HESS J1641-463 using 64 months of observations with the Fermi Large Area Telescope (LAT). Previously only one GeV source was reported in this region and was associated with HESS J1640-465. With an increased dataset and the improved sensitivity afforded by the reprocessed data (P7REP) of the LAT, we now report the detection, morphological study and spectral analysis of two distinct sources above 100 MeV. The softest emission in this region comes from the TeV source HESS J1641-463 which is well fitted with a power law of index Gamma = 2.47 +/- 0.05 +/- 0.06 and presents no significant gamma-ray signal above 10 GeV, which contrasts with its hard spectrum at TeV energies. The Fermi-LAT spectrum of the second TeV source, HESS J1640-465 is well described by a power-law shape of index Gamma = 1.99 +/- 0.04 +/- 0.07 that links up naturally with the spectral data points obtained by the High Energy Stereoscopic System (H.E.S.S.). These new results provide new constraints concerning the identification of these two puzzling gamma-ray sources.