A Significant Detection of X-ray Polarization in Sco X-1 with PolarLight and Constraints on the Corona Geometry
Date Issued
2022
Author(s)
Long, Xiangyun
•
Feng, Hua
•
Li, Hong
•
Zhu, Jiahuan
•
Wu, Qiong
•
Huang, Jiahui
•
Minuti, Massimo
•
Jiang, Weichun
•
Yang, Dongxin
•
Citraro, Saverio
•
Nasimi, Hikmat
•
Yu, Jiandong
•
Jin, Ge
•
Zeng, Ming
•
An, Peng
•
Jiang, Jiachen
•
•
Baldini, Luca
•
Bellazzini, Ronaldo
•
Brez, Alessandro
•
Latronico, Luca
•
Sgrò, Carmelo
•
Spandre, Gloria
•
Pinchera, Michele
•
•
Abstract
We report the detection of X-ray polarization in the neutron-star low-mass X-ray binary Scorpius (Sco) X-1 with PolarLight. The result is energy-dependent, with a nondetection in 3-4 keV but a 4σ detection in 4-8 keV; it is also flux-dependent in the 4-8 keV band, with a nondetection when the source displays low fluxes but a 5σ detection during high fluxes, in which case we obtain a polarization fraction of 0.043 ± 0.008 and a polarization angle of 52.°6 ± 5.°4. This confirms a previous marginal detection with OSO-8 in the 1970s and marks Sco X-1 as the second astrophysical source with a significant polarization measurement in the keV band. The measured polarization angle is in line with the jet orientation of the source on the sky plane (54°), which is supposedly the symmetry axis of the system. Combining previous spectral analysis, our measurements suggest that an optically thin corona is located in the transition layer under the highest accretion rates, and disfavor the extended accretion disk corona model.
Volume
924
Issue
1
Start page
L13
Issn Identifier
2041-8205
Ads BibCode
2022ApJ...924L..13L
Rights
open.access
File(s)![Thumbnail Image]()
Loading...
Name
2022_ApJL_Long.pdf
Description
pdf editoriale
Size
583.02 KB
Format
Adobe PDF
Checksum (MD5)
3300624098c92ecf103f342e5d42b8d5