Insight-HXMT Detections of Hard X-ray Tails in Scorpius X-1

Abstract

Using the observations of the high-energy (HE) detector of the Hard X-ray Modulation Telescope (Insight-HXMT) for Scorpius X-1 in 2018, we search for hard X-ray tails in the hard X-ray spectra in ~30-200 keV. The hard X-ray tails are found throughout the Z-track on the hardness-intensity diagram and they harden and fade away from the horizontal branch (HB), through the normal branch (NB), to the flaring branch (FB). Comparing the hard X-ray spectra between Cyg X-1 and Sco X-1, it is concluded that the hard X-ray spectrum of Cyg X-1 shows high-energy cutoff, implying a hot corona in it, but the high-energy cutoff does not reveal in the hard X-ray spectrum of Sco X-1. Jointly fitting the HE spectrum with the medium-energy and low-energy spectra of Sco X-1 in ~2-200 keV, it is suggested that the upscattering Comptonization of the neutron star (NS) emission photons by the energetic free-falling electrons onto the NS or by the hybrid electrons in the boundary layer between the NS and the accretion disk could be responsible for the hard X-ray tails of Sco X-1 on the HB and NB, but neither of the two mechanisms can be responsible for the hard X-ray tail on the FB. Some possible origins for the peculiar hard X-ray tail of FB are argued.

arXiv comment26 pages, 7 figures

References in corpus (57)

• X-ray Properties of Black-Hole Binaries
• Broad-band gamma-ray and X-ray spectra of NGC 4151 and their implications for physical processes and geometry
• The May 1989 outburst of the Soft X-ray Transient GS 2023+338 (V404 Cyg)
• Overview to the Hard X-ray Modulation Telescope (Insight-HXMT) Satellite
• X-ray Spectral Formation in a Converging Fluid Flow: Spherical Accretion into Black Holes
• The Discovery of a State Dependent Hard Tail in the X-ray Spectrum of the Luminous Z-source GX 17+2
• Testing Comptonization models using BeppoSAX observations of Seyfert 1 galaxies
• The converging inflow spectrum is an intrinsic signature for a black hole: Monte-Carlo simulations of Comptonization on free-falling electrons
• Discovery of oscillations above 200 keV in a black hole X-ray binary with Insight-HXMT
• A simple model for magnetic reconnection heated corona
• Detection of a Hard Tail in the X-ray Spectrum of the Z Source GX 349+2
• Insight-HXMT observations of the New Black Hole Candidate MAXI J1535-571: timing analysis
• A systematic analysis of the broad Fe Kalpha line in neutron star LMXBs with XMM-Newton
• On the Spectral Evolution of Cygnus X-2 along its Color-Color Diagram
• Insight-HXMT observations of jet-like corona in a black hole X-ray binary MAXI J1820+070
• Measurements of accretion disc corona size in LMXB: consequences for Comptonization and LMXB models
• Three-Layered Atmospheric Structure in Accretion Disks Around Stellar-Mass Black Holes
• Spectra from a magnetic reconnection-heated corona in AGN
• A new Comptonization model for low-magnetized accreting neutron stars in low mass X-ray binaries
• Spectral Investigations of the nature of the Sco X-1 like sources
• Discovery of photon index saturation in the black hole binary GRS 1915+105
• The Composite Broad Band Spectrum of Cir X-1 at the Periastron: a Peculiar Z-source
• The Burst and Transient Source Experiment (BATSE) Earth Occultation Catalog of Low-Energy Gamma-Ray Sources
• RXTE Observation of Cygnus X-1: Spectral Analysis
• An explanation of the Z-track sources
• Broad-band Spectral Evolution of Scorpius X-1 along its Color-Color Diagram
• A Hard X-ray View on Scorpius X-1 with INTEGRAL: non-Thermal Emission ?
• The effect of coronal radiation on a residual inner disk in the low/hard spectral state of black hole X-ray binary systems
• The Emission from Inner Disk and Corona in the Low and Intermediate Spectral States of Black Hole X-ray Binaries
• On the nature of the Cygnus X-2 like Z-track sources
• The transient hard X-ray tail of GX 17+2: new BeppoSAX results
• Insight-HXMT observations of 4U~1636-536: Corona cooling revealed with single short type-I X-ray burst
• The INTEGRAL view on Black Hole X-ray Binaries
• On the nature of the first transient Z-source XTE J1701-462: its accretion disk structure, neutron star magnetic field strength, and hard tail
• INTEGRAL spectral variability study of the atoll 4U 1820-30: first detection of hard X-ray emission
• A model for the Z-track phenomenon in GX 5-1 and observational evidence for the physical origins of the kHz QPO
• Transitions and Origin of the Type-B Quasi-Periodic Oscillation in the Black Hole X-ray Binary MAXI~ J1348--630
• New Evidence for a Black Hole in the Compact Binary Cygnus X-3
• Disc-Jet coupling in the LMXB 4U1636-53 from INTEGRAL
• The X-ray spectral evolution of Cyg X-2 in the framework of bulk Comptonization
• Coronal properties of black hole X-ray binaries in the hard state as seen by NuSTAR and Swift
• Resolving the Hard X-ray Emission of GX 5-1 with INTEGRAL
• Spectral states evolution of 4U 1728-34 observed by INTEGRAL and RXTE: non-thermal component detection
• BeppoSAX Observations of the Power and Energy Spectral Evolution in the Black Hole Candidate XTE J1650-500
• Insight-HXMT firm detection of the highest energy fundamental cyclotron resonance scattering feature in the spectrum of GRO J1008-57
• The hard X-ray tails in neutron star low mass X-ray binaries: BeppoSAX observations and possible theoretical explanation of the GX 17+2 case
• Study of the Cir X--1 Broad Band Spectrum at Orbital Phases Close to the Apoastron
• Hard X-ray emission of Sco X-1
• Studying the Properties of Accretion Disks and Coronae in Black Hole X-ray Binaries with Monte-Carlo Simulations
• Implication of the observable spectral cutoff energy evolution in XTE J1550-564
• Evolution of Hard X-Ray Spectra Along the Branches in Cir X-1
• In-orbit calibration status of the Insight-HXMT
• Broadband Spectral Analysis of Aql X-1
• A search for Very High Energy gamma-ray emission from Scorpius X-1 with the MAGIC telescopes
• Fe K$\alpha$ and Fe K$\beta$ line detection in the NuSTAR spectrum of the ultra-bright Z-source Scorpius X-1
• The hard X-ray emission along the "Z" track in GX 17+2
• Broadband variability study of MAXI J1631-479 in its Hard-Intermediate State observed with Insight-HXMT