Hints of gamma-ray orbital variability from gamma^2 Velorum

Abstract

Context. Colliding wind binaries are massive systems featuring strong, interacting stellar winds which may act as particle accelerators. Therefore, such binaries are good candidates for detection at high energies. However, only the massive binary Eta Carinae has been firmly associated with a gamma-ray signal. A second system, gamma^2 Velorum, is positionally coincident with a gamma-ray source, but unambiguous identification remains lacking. Aims. Observing orbital modulation of the flux would establish an unambiguous identification of the binary gamma^2 Velorum as the gamma-ray source detected by the Fermi Large Area Telescope (Fermi-LAT). Methods. We have used more than 10 years of observations with Fermi-LAT. Events are folded with the orbital period of the binary to search for variability. Systematic errors that might arise from the strong emission of the nearby Vela pulsar are studied by comparing with a more conservative pulse-gated analysis. Results. Hints of orbital variability are found, indicating maximum flux from the binary during apastron passage. Conclusions. Our analysis strengthens the possibility that gamma-rays are produced in gamma^2 Velorum, most likely as a result of particle acceleration in the wind collision region. The observed orbital variability is consistent with predictions from recent MHD simulations, but contrasts with the orbital variability from Eta Carinae, where the peak of the light curve is found at periastron.

7 pages, 6 figures. Accepted by A&A

References in corpus (12)

• TEMPO2, a new pulsar timing package. I: Overview
• Physical Properties of Wolf-Rayet Stars
• Tempo2, a new pulsar timing package. II: The timing model and precision estimates
• Precise Gamma-Ray Timing and Radio Observations of 17 Fermi Gamma-Ray Pulsars
• Non-thermal emission processes in massive binaries
• γ^2 Velorum: Orbital Solution and Fundamental Parameter Determination with SUSI
• The first full orbit of Eta Carinae seen by Fermi
• Simulating three-dimensional nonthermal high-energy photon emission in colliding-wind binaries
• Overview of non-transient gamma-ray binaries and prospects for the Cherenkov Telescope Array
• 3D magneto-hydrodynamic models of non-thermal photon emission in the binary system ${\gamma }^2$ Velorum
• A lepto-hadronic model of gamma rays from the Eta Carinae and prospects for neutrino telescopes
• Investigation of the WR 11 field at decimeter wavelengths

Cited by in corpus (14)

• Incremental Fermi Large Area Telescope Fourth Source Catalog
• An update on Fermi-LAT transients in the Galactic plane, including strong activity of Cygnus X-3 in mid-2020
• Eta Carinae with Fermi-LAT: Two full orbits and the third periastron
• And then they were two: detection of non-thermal radio emission from the bow shocks of two runaway stars
• The Galactic high mass X-ray binary population with Fermi -LAT
• Evidence for non-thermal X-ray emission from the double WR colliding-wind binary Apep
• The high-energy emission from HD~93129A near periastron
• Inverse Compton cooling of thermal plasma in colliding-wind binaries
• Probing cosmic ray escape from η Carinae
• Exploring non-thermal emission from the star-forming region NGC 3603 through a realistic modelling of its environment
• Radio study of the colliding wind binary HD93129A near periastron and its surroundings
• Limits on the non-thermal emission of the WR-WR system Apep
• On the orbital variability of gamma-ray emission in ${\gamma }^2$ Velorum
• Diffuse Hot Plasma in the Interstellar Medium and Galactic Outflows