TY - JOUR
T1 - Flux-resolved Spectropolarimetric Evolution of the X-Ray Pulsar Hercules X-1 Using IXPE
AU - Garg, Akash
AU - Rawat, Divya
AU - Bhargava, Yash
AU - Méndez, Mariano
AU - Bhattacharyya, Sudip
N1 - Funding Information:
The authors thank the anonymous reviewer for constructive comments to improve the manuscript. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN). It was distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC) at NASA Goddard Space Flight Center (GSFC). M.M. acknowledges support from the research program Athena with project number 184.034.002, which is (partly) financed by the Dutch Research Council (NWO). M.M. has benefited from discussions during Team Meetings of the International Space Science Institute (Bern), whose support he acknowledges.
Publisher Copyright:
© 2023. The Author(s). Published by the American Astronomical Society.
PY - 2023/5/5
Y1 - 2023/5/5
N2 - We conduct a spectropolarimetric study of the accreting X-ray pulsar Hercules X-1 using observations with the Imaging X-ray Polarimetry Explorer (IXPE). IXPE monitored the source in three different epochs, sampling two “Main-on” and one “Short-on” state of the well-known super-orbital period of the source. We find that the 2-7 keV polarization fraction increases significantly from ∼7% to 9% in the Main-on state to ∼15%-19% in the Short-on state, while the polarization angle remains more or less constant or changes slightly, ∼47°-59°, in all three epochs. The polarization degree and polarization angle are consistent with being energy independent for all three epochs. We propose that in the Short-on state, when the neutron star is partially blocked by the disk warp, the increase in the polarization fraction can be explained as a result of the preferential obstruction of one of the magnetic poles of the neutron star.
AB - We conduct a spectropolarimetric study of the accreting X-ray pulsar Hercules X-1 using observations with the Imaging X-ray Polarimetry Explorer (IXPE). IXPE monitored the source in three different epochs, sampling two “Main-on” and one “Short-on” state of the well-known super-orbital period of the source. We find that the 2-7 keV polarization fraction increases significantly from ∼7% to 9% in the Main-on state to ∼15%-19% in the Short-on state, while the polarization angle remains more or less constant or changes slightly, ∼47°-59°, in all three epochs. The polarization degree and polarization angle are consistent with being energy independent for all three epochs. We propose that in the Short-on state, when the neutron star is partially blocked by the disk warp, the increase in the polarization fraction can be explained as a result of the preferential obstruction of one of the magnetic poles of the neutron star.
UR - http://www.scopus.com/inward/record.url?scp=85158896842&partnerID=8YFLogxK
U2 - 10.3847/2041-8213/acccfa
DO - 10.3847/2041-8213/acccfa
M3 - Article
AN - SCOPUS:85158896842
SN - 2041-8205
VL - 948
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 1
M1 - L10
ER -