Optical and ultraviolet monitoring of the black hole X-ray binary MAXI J1820+070/ASASSN-18ey for 18 months
| Autor: | Lingzhi Wang, Liming Rui, Danfeng Xiang, Hua Feng, Hanna Sai, Jicheng Zhang, Weili Lin, Wenxiong Li, Yong Zhao, D. O. Mirzaqulov, Shuhrat A. Ehgamberdiev, Tianrui Sun, Jujia Zhang, Han Lin, Xulin Zhao, Jie Lin, Xinghan Zhang, Xue Li, Tianmeng Zhang, Chengyuan Wu, Jun Mo, Jianfeng Wu, Xiaofeng Wang |
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| Rok vydání: | 2021 |
| Předmět: |
High Energy Astrophysical Phenomena (astro-ph.HE)
Physics 010308 nuclear & particles physics Astrophysics::High Energy Astrophysical Phenomena X-ray binary FOS: Physical sciences Balmer series Astronomy and Astrophysics Astrophysics 01 natural sciences Spectral line Luminosity Photometry (astronomy) symbols.namesake Space and Planetary Science 0103 physical sciences symbols Astrophysics::Solar and Stellar Astrophysics Continuum (set theory) Emission spectrum Astrophysics - High Energy Astrophysical Phenomena 010303 astronomy & astrophysics Equivalent width |
| Zdroj: | Monthly Notices of the Royal Astronomical Society. 504:4226-4241 |
| ISSN: | 1365-2966 0035-8711 |
| Popis: | MAXI J1820+070 is a low-mass black hole X-ray binary system with high luminosity in both optical and X-ray bands during the outburst periods. We present extensive photometry in X-ray, ultraviolet, and optical bands, as well as densely-cadenced optical spectra, covering the phase from the beginning of optical outburst to $\sim$550 days. During the rebrightening process, the optical emission preceded the X-ray by 20.80 $\pm$ 2.85 days. The spectra are characterized by blue continua and emission features of Balmer series, He I, He II lines and broad Bowen blend. The pseudo equivalent width (pEW) of emission lines are found to show anticorrelations with the X-ray flux measured at comparable phases, which is due to the increased suppression by the optical continuum. At around the X-ray peak, the full width at half maximums (FWHMs) of H$_{\beta}$ and He II $\lambda$4686 tend to stabilize at 19.4 Angstrom and 21.8 Angstrom, which corresponds to the line forming region at a radius of 1.7 and 1.3 R_sun within the disk. We further analyzed the absolute fluxes of the lines and found that the fluxes of H$_{\beta}$ and He II $\lambda$4686 show positive correlations with the X-ray flux, favoring that the irradiation model is responsible for the optical emission. However, the fact that X-ray emission experiences a dramatic flux drop at t$\sim$200 days after the outburst, while the optical flux only shows little variations suggests that additional energy such as viscous energy may contribute to the optical radiation in addition to the X-ray irradiation. Comment: Accepted for publication in MNRAS |
| Databáze: | OpenAIRE |
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