Investigation of the Microquasar SS 433 with VERITAS

Abstract

Microquasars such as SS 433 are considered potential contributors to cosmic rays up to the knee of the cosmic ray energy spectrum ($\sim 4\mathrm{PeV}$), where a transition in the dominant acceleration processes is expected. The SS 433 system, located within the W50 supernova remnant, is a Galactic microquasar with relativistic jets interacting with the surrounding medium over parsec scales, providing an example for studying jet-driven particle acceleration. A deep morphological and spectral study of SS 433 is performed using more than 150 hours of observations with VERITAS, sensitive to $\gamma$-ray energies $>100\mathrm{GeV}$. With an angular resolution better than $0.1^{°}$, extended TeV $\gamma$-ray emission is resolved from both the eastern and western jet lobes, located tens of parsecs from the central binary. The emission appears elongated along the jet axis and coincides with regions where the jets interact with the surrounding supernova remnant. No TeV emission is detected from the central binary, nor is significant emission observed between the central binary and the jet lobes. Phase-resolved analyses show no evidence for variability with orbital or precessional phase, supporting a steady emission scenario. The observed morphology and spectra are consistent with scenarios where particles are accelerated in the lobes of the jets, possibly through shocks or alternative processes such as magnetic reconnection. The extended TeV emission from the jet lobes of SS 433 favors a leptonic origin in the VERITAS energy range, suggesting any hadronic acceleration is subdominant. The results offer valuable constraints on how microquasar jets may contribute to the Galactic cosmic-ray population toward the knee.

arXiv comment18 pages, 12 figures, Accepted for publication in the Astrophysical Journal (ApJ)

References in corpus (29)

• An Introduction to PYTHIA 8.2
• The CO-to-H2 Conversion Factor
• HI4PI: A full-sky HI survey based on EBHIS and GASS
• Background Modelling in Very-High-Energy gamma-ray Astronomy
• VERITAS: the Very Energetic Radiation Imaging Telescope Array System
• Parametrization of gamma-ray production cross-sections for pp interactions in a broad proton energy range from the kinematic threshold to PeV energies
• The 2HWC HAWC Observatory Gamma Ray Catalog
• The First LHAASO Catalog of Gamma-Ray Sources
• The Milky Way Imaging Scroll Painting (MWISP): Project Details and Initial Results from the Galactic Longitude of 25.8deg to 49.7deg
• The High Resolution X-ray Spectrum of SS 433 using the Chandra HETGS
• Very high energy particle acceleration powered by the jets of the microquasar SS 433
• Rotation Curve of the Milky Way out to $\sim$ 200 kpc
• Iron Emission Lines from Extended X-ray Jets in SS 433: Reheating of Atomic Nuclei
• Absorption of Very High Energy Gamma Rays in the Milky Way
• Fermi-LAT Search for Pulsar Wind Nebulae around gamma-ray Pulsars
• Improved $\gamma$/hadron separation for the detection of faint gamma-ray sources using boosted decision trees
• Acceleration and transport of relativistic electrons in the jets of the microquasar SS 433
• XMM-Newton observations of the eastern jet of SS433
• The Jets and and Supercritical Accretion Disk in SS433
• On masses of the components in SS433
• INTEGRAL observations of SS433: system's parameters and nutation of supercritical accretion disk
• The Large-scale ISM of SS433/W50 Revisited
• Gamma-ray heartbeat powered by the microquasar SS 433
• The throughput calibration of the VERITAS telescopes
• Radio study of the extended TeV source VER J1907+062
• Probing the history of SS433's jet kinematics via Decade-resolution radio observations of W50
• GeV-TeV Counterparts of SS 433/W50 from Fermi-LAT and HAWC Observations
• Spectral study of very high energy gamma rays from SS 433 with HAWC
• Multiwavelength Investigation of $\gamma$-ray Source MGRO J1908+06 Emission Using Fermi-LAT, VERITAS, and HAWC