Gamma-ray astronomy

Abstract:

Over the past decade, observations of relativistic outflows from outbursting X-ray binaries in the Galactic field have grown significantly. In this work, we present the first detection of moving and decelerating radio-emitting outflows from an X-ray binary in a globular cluster. MAXI J1848−015 is a recently discovered transient X-ray binary in the direction of the globular cluster GLIMPSE-C01. Using observations from the Karl G. Jansky Very Large Array, and a monitoring campaign with the MeerKAT observatory for 500 days, we model the motion of the outflows. This represents some of the most intensive, long-term coverage of relativistically moving X-ray binary outflows to date. We use the proper motions of the outflows from MAXI J1848−015 to constrain the component of the intrinsic jet speed along the line of sight, β int cos θ ejection , to be =0.19 ± 0.02. Assuming it is located in GLIMPSE-C01, at 3.4 kpc, we determine the intrinsic jet speed, β int = 0.79 ± 0.07, and the inclination angle to the line of sight, θ ejection = 76° ± 2°. This makes the outflows from MAXI J1848−015 somewhat slower than those seen from many other known X-ray binaries. We also constrain the maximum distance to MAXI J1848−015 to be 4.3 kpc. Finally, we discuss the implications of our findings for the nature of the compact object in this system, finding that a black hole primary is a viable (but as-of-yet unconfirmed) explanation for the observed properties of MAXI J1848−015. If future data and/or analysis provide more conclusive evidence that MAXI J1848−015 indeed hosts a black hole, it would be the first black hole X-ray binary in outburst identified in a Galactic globular cluster.

Abstract:

Many theories beyond the Standard Model of particle physics predict the existence of axionlike particles (ALPs) that mix with photons in the presence of a magnetic field. Searching for the effects of ALP-photon mixing in gamma-ray observations of blazars has provided some of the strongest constraints on ALP parameter space so far. Previously, only individual sources have been analyzed. We perform a combined analysis on Fermi Large Area Telescope data of three bright flaring flat-spectrum radio quasars, with the blazar jets themselves as the dominant mixing region. For the first time, we include a full treatment of photon-photon dispersion within the jet and account for the uncertainty in our B-field model by leaving the field strength free in the fitting. Overall, we find no evidence for ALPs but are able to exclude the ALP parameters 5 neV≲ma≲200 neV and gaγ≳5×10-12 GeV-1 with 95% confidence.