Measuring a Truncated Disk in Aquila X-1

King, A. L.; Tomsick, John A.; Miller, J. M.; Chenevez, J.; Barret, D.; Boggs, Steven E.; Chakrabarty, Deepto; Christensen, Finn Erland; Craig, William W.; Fürst, Felix; Hailey, Charles J.; Harrison, Fiona A.; Parker, M. L.; Stern, Daniel; Romano, P.; Walton, D. J.; Zhang, William W.

doi:10.3847/2041-8205/819/2/l29

Cited by 38 publications

(50 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For a highly ionized disk, the fluorescent FeKα line from reflection is challenging to detect during a burst with NICER, whereas the soft excess is highly significant . For an inclination angle of 20° ( King et al 2016) the expected reflection fraction is f refl =0.52 for a thin disk that extends to the neutron star (He & Keek 2016). The disk has, however, been observed to truncate at R in ;15 R g (Sakurai et al 2012;King et al 2016).…”

Section: Disk Reflectionmentioning

confidence: 99%

“…For an inclination angle of 20° ( King et al 2016) the expected reflection fraction is f refl =0.52 for a thin disk that extends to the neutron star (He & Keek 2016). The disk has, however, been observed to truncate at R in ;15 R g (Sakurai et al 2012;King et al 2016). From Figure 5 in He & Keek (2016) we estimate that for a 1.4 M e and 10 km radius neutron star this gap reduces the reflection fraction to f refl ;0.15.…”

Section: Disk Reflectionmentioning

confidence: 99%

“…This model includes more parameters, which are hard to constrain within short time intervals. Because R in was weakly constrained in Section 3.2, we fix its value to R in =15 R g , inferred from reflection spectroscopy of the persistent emission in the soft state of AqlX-1 (King et al 2016). An updated analysis of the soft state (Ludlam et al 2017) and a study of the hard state (Sakurai et al 2012) reveal similar R in , and our burst results are insensitive to the differences.…”

Section: Time-resolved Spectroscopymentioning

confidence: 99%

“…In this Letter, we investigate one of NICER's first X-ray burst observations: a bright burst from AqlX-1. This source exhibits frequent accretion outbursts during which X-ray bursts have been observed (Koyama et al 1981), and disk reflection has been detected in the persistent emission (King et al 2016;Ludlam et al 2017). After describing the NICER observations of AqlX-1 (Section 2), we perform a detailed analysis of the soft excess in the burst spectrum (Section 3).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

NICER Observes the Effects of an X-Ray Burst on the Accretion Environment in Aql X-1

Keek

Arzoumanian

Bult

et al. 2018

ApJL

View full text Add to dashboard Cite

Accretion disks around neutron stars regularly undergo sudden strong irradiation by Type-I X-ray bursts powered by unstable thermonuclear burning on the stellar surface. We investigate the impact on the disk during one of the first X-ray burst observations with the Neutron Star Interior Composition Explorer (NICER) on the International Space Station. The burst is seen from AqlX-1 during the hard spectral state. In addition to thermal emission from the neutron star, the burst spectrum exhibits an excess of soft X-ray photons below 1 keV, where NICER's sensitivity peaks. We interpret the excess as a combination of reprocessing by the strongly photoionized disk and enhancement of the pre-burst persistent flux, possibly due to Poynting-Robertson drag or coronal reprocessing. This is the first such detection for a short sub-Eddington burst. As these bursts are observed frequently, NICER will be able to study how X-ray bursts affect the disk and corona for a range of accreting neutron star systems and disk states.

show abstract

Section: Disk Reflectionmentioning

confidence: 99%

Section: Disk Reflectionmentioning

confidence: 99%

Section: Time-resolved Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

NICER Observes the Effects of an X-Ray Burst on the Accretion Environment in Aql X-1

Keek

Arzoumanian

Bult

et al. 2018

ApJL

View full text Add to dashboard Cite

show abstract

“…Even in the case of accreting millisecond pulsars (AMSPs), which are usually found in a hard state and for which we expect that the inner disk is truncated by the magnetic field, inner disk radii in the range 6 − 40 R g were usually found (see, e.g. Papitto et al 2009;Cackett et al 2009;Papitto et al 2010Papitto et al , 2013aKing et al 2016). Also, the reflection fraction inferred from the rfxconv model, Ω/2π ∼ 0.22, although somewhat smaller than what is expected for a geometry with a spherical corona surrounded by the accretion disk (Ω/2π ∼ 0.3), is in agreement with typical values for these sources.…”

Section: The Combined Xmm-newton and Integral Spectrummentioning

confidence: 99%

XMM-Newtonand INTEGRAL view of the hard state of EXO 1745−248 during its 2015 outburst

Matranga

Papitto

Salvo

et al. 2017

A&A

View full text Add to dashboard Cite

Context. Transient low-mass X-ray binaries (LMXBs) often show outbursts lasting typically a few-weeks and characterized by a high X-ray luminosity (L x ≈ 10 36 − 10 38 erg s −1 ), while for most of the time they are found in X-ray quiescence (L X ≈ 10 31 − 10 33 erg s −1 ). EXO 1745-248 is one of them. Aims. The broad-band coverage, and the sensitivity of instrumet on board of XMM-Newton and INTEGRAL, offers the opportunity to characterize the hard X-ray spectrum during EXO 1745-248 outburst. Methods. In this paper we report on quasi-simultaneous XMM-Newton and INTEGRAL observations of the X-ray transient EXO 1745-248 located in the globular cluster Terzan 5, performed ten days after the beginning of the outburst (on 2015 March 16th) shown by the source between March and June 2015. The source was caught in a hard state, emitting a 0.8-100 keV luminosity of ≃ 10 37 erg s −1 . Results. The spectral continuum was dominated by thermal Comptonization of seed photons with temperature kT in ≃ 1.3 keV, by a cloud with moderate optical depth τ ≃ 2 and electron temperature kT e ≃ 40 keV. A weaker soft thermal component at temperature kT th ≃ 0.6-0.7 keV and compatible with a fraction of the neutron star radius was also detected. A rich emission line spectrum was observed by the EPIC-pn on-board XMM-Newton; features at energies compatible with K-α transitions of ionized sulfur, argon, calcium and iron were detected, with a broadness compatible with either thermal Compton broadening or Doppler broadening in the inner parts of an accretion disk truncated at 20 ± 6 gravitational radii from the neutron star. Strikingly, at least one narrow emission line ascribed to neutral or mildly ionized iron is needed to model the prominent emission complex detected between 5.5 and 7.5 keV. The different ionization state and broadness suggest an origin in a region located farther from the neutron star than where the other emission lines are produced. Seven consecutive type-I bursts were detected during the XMM-Newton observation, none of which showed hints of photospheric radius expansion. A thorough search for coherent pulsations from the EPIC-pn light curve did not result in any significant detection. Upper limits ranging from a few to 15% on the signal amplitude were set, depending on the unknown spin and orbital parameters of the system.

show abstract

Reflecting on accretion in neutron star low-mass X-ray binaries

Ludlam

2024

Astrophys Space Sci

View full text Add to dashboard Cite

Measuring a Truncated Disk in Aquila X-1

Cited by 38 publications

References 47 publications

NICER Observes the Effects of an X-Ray Burst on the Accretion Environment in Aql X-1

NICER Observes the Effects of an X-Ray Burst on the Accretion Environment in Aql X-1

XMM-Newtonand INTEGRAL view of the hard state of EXO 1745−248 during its 2015 outburst

Reflecting on accretion in neutron star low-mass X-ray binaries

Contact Info

Product

Resources

About