10 papers
Predictions for the X-ray polarisation modulation in Cygnus X-1 from reflection off the stellar companion and its wind
Bert Vander Meulen, Kun Hu, Victoria Grinberg +1
Context. Cyg X-1 is one of the brightest X-ray binaries and has been observed multiple times with the Imaging X-ray Polarimetry Explorer (IXPE). Recent studies report tentative evi…
X-ray Polarization Signatures from Comptonization by Magnetic Reconnection Plasmoids
John Groger, Kun Hu, Henric Krawczynski
Emission from X-ray binaries in the hard spectral state is dominated by high-energy radiation attributed to the Compton scattering of seed photons. The prevalent model of the Compt…
Magnetar Fireballs and Short Bursts: Curved Spacetime Lensing, QED Effects, Spectra, Polarization, and Impulse Responses
Zorawar Wadiasingh, Hoa Dinh Thi, Constantinos Kalapotharakos +13
Magnetar short bursts (SBs) are hard X-ray transients of durations s peaking at keV, and are prime targets for new high-energy missions and polarimeters. The…
Resonant Inverse Compton Scattering and Hard X-ray Emission in Magnetar Magnetospheres
Kun Hu, Nicholas Rackers, Alexander Y. Chen
Magnetars are a subclass of neutron stars with ultra-strong surface magnetic fields. Some magnetars exhibit persistent hard X-ray emission, characterized by power-law tails with ph…
A New Approach for Testing Einstein's Theory of Gravity Close to Rapidly Spinning Black Holes
Shravan Vengalil Menon, Kun Hu, Henric Krawczynski
The Penrose process and the collisional Penrose process involve particles decaying or interacting very close to a spinning black hole, respectively, during which some particles are…
Pulsed, Polarized X-ray Emission from Neutron Star Surfaces: the Effects of Vacuum Birefringence in the Magnetosphere
Hoa Dinh Thi, Matthew G. Baring, Kun Hu +4
Intense magnetic fields in the atmospheres of neutron stars render non-trivial angular dependence of intensity and polarization of soft X-ray emission originating from their surfac…