The connection between the UV/optical and X-ray emission in the neutron star low-mass X-ray binary Aql X-1

López-Navas, E; Degenaar, N.; Parikh, A. S.; Santisteban, J. V. Hernández; Eijnden, J. van den

doi:10.1093/mnras/staa275

Cited by 10 publications

(4 citation statements)

References 84 publications

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“…About one-third of low-mass X-ray binaries (LMXBs) hosting neutron stars (NSs) are transient sources and characterized by a luminosity that varies over ∼10 32 -10 38 erg −2 s −1 , which is likely caused by an instability of the accretion induced by a variable accretion rate,  M. In this picture, the accretion flow drained from the companion star propagates toward the NS from the outer regions of the accretion disk (for a review see, e.g., Done et al 2007), which is confirmed by multiwavelength observations (e.g., López-Navas et al 2020). Except for the accretion rate, the NS's parameters, e.g., magnetic field and spin period, could also affect the accretion process.…”

Section: Introductionmentioning

confidence: 83%

Return of 4U 1730–22 after 49 yr Silence: The Outburst Properties Observed by NICER and Insight-HXMT

Chen

Zhang

et al. 2022

ApJL

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After 49 yr of quiescence, 4U 1730–22 became active and had two outbursts in 2021 and 2022; the onset and tail of the outbursts were observed by NICER, which give us a peerless opportunity to study the state transition and its underlying mechanism. In this work, we take both the neutron star (NS) surface and accretion disk emission as the seed photons of the Comptonization and derive their spectral evolution in a bolometric luminosity range of 1%–15% L Edd. In the high/soft state, the inferred inner disk radius and the NS radius are well consistent, which implies that the accretion disk is close to the NS surface. For the decay stage, we report a steep change of the accretion disk emission within 1 day, i.e., the soft-to-hard transition, which could be due to the propeller effect, and the corresponding NS surface magnetic field is 1.8–2.2 × 108 G. Moreover, the inner disk radius is truncated at the corotation radius, which is similar to the propeller effect detected from 4U 1608–52. The absence of the propeller effect in the hard-to-soft state transition implies that the transition between the magnetospheric accretion and the disk accretion is not the sole cause of the state transitions.

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Section: Introductionmentioning

confidence: 83%

Return of 4U 1730–22 after 49 yr Silence: The Outburst Properties Observed by NICER and Insight-HXMT

Chen

Zhang

et al. 2022

ApJL

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“…In previous correlation studies, the X-ray flux between 2 and 10 keV bands was usually calculated (e.g. Russell et al 2006 ;Armas Padilla et al 2013 ;Shahbaz et al 2015 ;L ópez-Navas et al 2020 ;Yao et al 2020 ). In order to compare with previous work, we carry out the same procedure using the 2-10 keV X-ray flux.…”

Section: The X-ray and Uv/optical Flux Correlationsmentioning

confidence: 99%

The origin of UV/optical emission in the black hole low-mass X-ray binary Swift J1753.5–0127

Yang¹,

Zhang²,

Russell³

et al. 2022

Monthly Notices of the Royal Astronomical Society

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The emission from the accreting black holes (BHs) in low-mass X-ray binaries (LMXBs) covers a broad energy band from radio to X-rays. Studying the correlations between emission in different energy bands during outbursts can provide valuable information about the accretion process. We analyse the simultaneous optical, ultraviolet (UV), and X-ray data of the BH-LMXB Swift J1753.5–0127 during its ∼12-yr long outburst with the Neil Gehrels Swift Observatory. We find that the UV/optical and X-ray emission are strongly correlated during the hard states of the outburst. We fit the relation with a power-law function $F_{\rm {UV/optical}} \propto F_{X}^{\beta }$ and find that the power-law index β increases from ∼0.24 to ∼0.33 as the UV/optical wavelength decreases from ∼5402 Å (V) to ∼2030 Å (UVW2). We explore the possible reasons for this and suggest that in Swift J1753.5–0127 the UV/optical emission is dominated by a viscously heated accretion disc at large radii. We find that the data that deviate from the correlation correspond to the low-intensity peaks appeared in the X-ray band during the outburst, and suggest that these deviations are driven by the emission from the inner part of the accretion disc.

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“…Flux calibration of the R1000B data was performed against ESO 2 and ING 3 Spectophotometric Standards (Oke 1974(Oke , 1990 depending on the epoch (Feige 66, Feige 110, G191-B2B, Ross 640 and G158-100) and using astrophy-photutils-based routines (Bradley et al 2019). We also applied a reddening correction of E B−V = 0.65 mag (López-Navas et al 2020). The main aim of this task is not to report absolute flux measurements but to compute line intensity ratios.…”

Section: Data Reductionmentioning

confidence: 99%

Optical nebular emission following the most luminous outburst of Aquila X-1

Panizo-Espinar

Muñoz-Darias

Padilla

et al. 2021

A&A

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Aquila X-1 is a prototypical neutron star low mass X-ray binary and one of the most studied X-ray transients. We present optical spectroscopy obtained with the Gran Telescopio Canarias (10.4 m) during the 2016 outburst, the brightest recorded in recent times and which showed a standard evolution with hard and soft accretion states. Our dataset includes a dense coverage of the brightest phases of the event, as well as the decay towards quiescence. We searched for optical winds by studying the profiles and evolution of the main emission lines and found no indisputable wind signatures, such as P-Cyg profiles. Nonetheless, our detailed analysis of the particularly strong and broad Hα emission line, detected at the end of the outburst, is consistent with the presence of a nebular phase produced by optically thin ejecta at ∼800 km s−1 or, alternatively, an extended disc atmosphere. We discuss these possibilities as well as the similarities with the phenomenology observed in other black hole and neutron star systems. Our study suggests that optical nebular phases might be a relatively common observational feature during the late stages of low mass X-ray binaries’ outbursts, enabling us to probe the presence of outflows at low-to-intermediate orbital inclinations.

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The connection between the UV/optical and X-ray emission in the neutron star low-mass X-ray binary Aql X-1

Cited by 10 publications

References 84 publications

Return of 4U 1730–22 after 49 yr Silence: The Outburst Properties Observed by NICER and Insight-HXMT

Return of 4U 1730–22 after 49 yr Silence: The Outburst Properties Observed by NICER and Insight-HXMT

The origin of UV/optical emission in the black hole low-mass X-ray binary Swift J1753.5–0127

Optical nebular emission following the most luminous outburst of Aquila X-1

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