A wide-field X-ray search for the Geminga pulsar halo with SRG/ART-XC

¹ Space Research Institute (IKI) 84/32 Profsouznaya str. Moscow 117997, Russian Federation
² Laboratoire d’Annecy-le-Vieux de Physique Théorique (LAPTh), CNRS, USMB F-74940 Annecy, France
³ Sorbonne Université & Laboratoire de Physique Théorique et Hautes Énergies (LPTHE), CNRS 4 Place Jussieu Paris, France
⁴ Ioffe Institute, Saint-Peterburg Politechnicheskaya 26 194021, Russian Federation
⁵ Department of Physics, University of Torino, Via P. Giuria 1 10125 Torino, Italy
⁶ Istituto Nazionale di Fisica Nucleare, Via P. Giuria 1 10125 Torino, Italy
⁷ European Organization for Nuclear Research (CERN) Geneva, Switzerland
⁸ Columbia Astrophysics Laboratory 550 West 120th Street New York NY 10027, USA

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 23 May 2025
Accepted: 28 September 2025

Abstract

Searches for the putative large-scale X-ray halo around the Geminga pulsar have been extensively performed using various narrow field-of-view X-ray telescopes. In this paper, we present wide-field scanning observation of Geminga with SRG/ART-XC. Our X-ray analysis provides, for the first time, direct imaging of a 3.5° ×3.5° region in the 4−12 keV energy band, comparable in extent to the expected Geminga emission. The ART-XC observation provides a highly uniform sky coverage without strong vignetting effects. The synchrotron X-ray halo flux was predicted using a physical model based on particle injection, diffusion, and cooling over the pulsar’s lifetime, as well as the spectral and spatial properties of the synchrotron X-ray and inverse-Compton gamma-ray emissions. The model is tuned to reproduce existing multiwavelength data from X-ray upper limits and GeV to TeV gamma-ray observations. After accounting for the high particle background and its uncertainties, no significant emission is found in the assumed source region, and X-ray flux upper limits are derived. These limits are less constraining by up to a factor of three with respect to existing results obtained with narrow field-of-view telescopes and longer exposure times. Nonetheless, we place direct and independent constraints on Geminga’s ambient magnetic field strength, which are compatible with other studies. Our methodology, including simulation for longer observation times, is applied for the first time to the wide field-of-view search for pulsar halos. Using extensive simulations, we also show that a 68% probability of detecting the Geminga pulsar halo can be achieved with a 20-day SRG/ART-XC exposure for a 3 μG magnetic field.