Reflection component in the Bright Atoll Source GX 9+9

Context. GX 9+9 (4U 1728−16) is a low mass X-ray binary source harboring a neutron star. Although it belongs to the subclass of the bright Atoll sources together with GX 9+1, GX 3+1, and GX 13+1, its broadband spectrum is poorly studied and apparently does not show reflection features in the spectrum. Aims. To constrain the continuum well and verify whether a relativistic smeared reflection component is present, we analyze the broadband spectrum of GX 9+9 using BeppoSAX and XMM-Newton spectra covering the 0.3−40 keV energy band. Methods. We fit the spectrum adopting a model composed of a disk-blackbody plus a Comptonized component whose seed photons have a blackbody spectrum (Eastern Model). A statistically equivalent model is composed of a Comptonized component whose seed photons have a disk-blackbody distribution plus a blackbody that mimics a saturated Comptonization likely associated with a boundary layer (Western model). Other trials did not return a good fit. Results. The spectrum of GX 9+9 was observed in a soft state and its luminosity is 2.3 × 1037 erg s−1 assuming a distance to the source of 5 kpc. In the Eastern Model scenario, we find the seed-photon temperature and electron temperature of the Comptonized component to be 1.14−0.07+0.10 keV and 2.80−0.04+0.09 keV, respectively, while the optical depth of the Comptonizing corona is 8.9 ± 0.4. The color temperature of the inner accretion disk is 0.86−0.02+0.08 keV and 0.82 ± 0.02 keV for the BeppoSAX and XMM-Newton spectrum, respectively. In the Western Model scenario, instead, we find that the seed-photon temperature is 0.87 ± 0.07 keV and 1.01 ± 0.08 keV for the BeppoSAX and XMM-Newton spectrum, respectively. The electron temperature of the Comptonized component is 2.9 ± 0.2 keV, while the optical depth is 9.4−1.1+1.5. The blackbody temperature is 1.79−0.18+0.09 keV and 1.85−0.15+0.07 keV for the BeppoSAX and XMM-Newton spectrum, respectively. The addition of a relativistic smeared reflection component improved the fit in both the scenarios, giving compatible values of the parameters, even though a significant broad emission line in the Fe-K region is not observed. Conclusions. From the reflection component we estimated an inclination angle of about 43−4+6 deg and 51−2+9 deg for the Eastern and Western Model, respectively. The value of the reflection fraction Ω/2π is 0.18 ± 0.04 and 0.21 ± 0.03 for the Eastern and Western Model, respectively, suggesting that the Comptonized corona should be compact and close to the innermost region of the system.

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A broadband spectral analysis of 4U 1702-429 using XMM-Newton and BeppoSAX data

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732383 ◽

2019 ◽

Vol 621 ◽

pp. A89 ◽

Cited By ~ 6

Author(s):

S. M. Mazzola ◽

R. Iaria ◽

T. Di Salvo ◽

M. Del Santo ◽

A. Sanna ◽

...

Keyword(s):

Binary Systems ◽

Integral Spectrum ◽

X Ray ◽

Broadband Spectrum ◽

Soft State ◽

Hard State ◽

Low Mass ◽

Reflection Component ◽

Innermost Region ◽

Integral Observation

Context. Most of the X-ray binary systems containing neutron stars classified as Atoll sources show two different spectral states, referred to as soft and hard. Moreover, a large number of these systems show a reflection component relativistically smeared in their spectra, which provides information on the innermost region of the system. Aims. Our aim is to investigate the poorly studied broadband spectrum of the low-mass X-ray binary system 4U 1702-429, which was recently analysed combining XMM-Newton and INTEGRAL data. The peculiar value of the reflection fraction brought us to analyse further broadband spectra of 4U 1702-429. Methods. We re-analysed the spectrum of the XMM-Newton/INTEGRAL observation of 4U 1702-429 in the 0.3–60 keV energy range and we extracted three 0.1–100 keV spectra of the source analysing three observations collected with the BeppoSAX satellite. Results. We find that the XMM-Newton/INTEGRAL spectrum is well fitted using a model composed of a disc blackbody plus a Comptonised component and a smeared reflection component. We used the same spectral model for the BeppoSAX spectra, finding that the addition of a smeared reflection component is statistically significant. The best-fit values of the parameters are compatible to each other for the BeppoSAX spectra. We find that the reflection fraction is 0.05−0.01+0.3 for the XMM-Newton/INTEGRAL spectrum and between 0.15 and 0.4 for the BeppoSAX ones. Conclusions. The relative reflection fraction and the ionisation parameter are incompatible between the XMM-Newton/INTEGRAL and the BeppoSAX observations and the characteristics of the Comptonising corona suggest that the source was in a soft state in the former observation and in a hard state in the latter.

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Broadband spectral analysis of MXB 1659−298 in its soft and hard state

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833982 ◽

2019 ◽

Vol 630 ◽

pp. A138

Author(s):

R. Iaria ◽

S. M. Mazzola ◽

T. Bassi ◽

A. F. Gambino ◽

A. Marino ◽

...

Keyword(s):

Absorption Lines ◽

X Ray ◽

Direct Emission ◽

Broadband Spectrum ◽

Hydrogen Column Density ◽

Soft State ◽

Transient Sources ◽

Hard State ◽

Reflection Component ◽

Spectral State

Context. The X-ray transient eclipsing source MXB 1659−298 went into outburst in 1999 and 2015. During these two outbursts the source was observed by XMM-Newton, NuSTAR, and Swift/XRT. Aims. Using these observations, we studied the broadband spectrum of the source to constrain the continuum components and to verify whether it had a reflection component, as is observed in other X-ray eclipsing transient sources. Methods. We combined the available spectra to study the soft and hard state of the source in the 0.45–55 keV energy range. Results. We report a reflection component in the soft and hard state. The direct emission in the soft state can be modeled with a thermal component originating from the inner accretion disk plus a Comptonized component associated with an optically thick corona surrounding the neutron star. On the other hand, the direct emission in the hard state is described only by a Comptonized component with a temperature higher than 130 keV; this component is associated with an optically thin corona. We observed narrow absorption lines from highly ionized ions of oxygen, neon, and iron in the soft spectral state. We investigated where the narrow absorption lines form in the ionized absorber. The equivalent hydrogen column density associated with the absorber is close to 6 × 1023 cm−2 and 1.3 × 1023 cm−2 in the soft and hard state, respectively.

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4U 1608–52 as a quasi-persistent X-ray source

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psaa099 ◽

2020 ◽

Vol 72 (6) ◽

Author(s):

Vojtěch Šimon

Keyword(s):

Accretion Disk ◽

Time Segment ◽

X Ray ◽

Band Emission ◽

Heating And Cooling ◽

Soft State ◽

Cyclic Variations ◽

Low Mass ◽

X Ray Binaries ◽

Disk Region

Abstract 4U 1608–52 is a soft X-ray transient. The analysis presented here of a particular part of its X-ray activity uses observations of RXTE/ASM and Swift/BAT. We show a time segment (MJD 54262–MJD 55090) (828 d) in which 4U 1608–52 behaved as a quasi-persistent X-ray source with a series of bumps, with a complicated relation between the evolution of fluxes in the soft (1.5–12 keV) and the hard (15–50 keV) X-ray regions. We ascribe these bumps to a series of propagations of heating and cooling fronts over the inner disk region without any transitions to the true quiescence. 4U 1608–52 oscillated around the boundary between the dominance of the Comptonized component and the dominance of the multicolor accretion disk in its luminosity. Only some of the bumps in this series were accompanied by a transition from the hard to the soft state; if it occurred, it displayed a strong hysteresis effect. The hard-band emission with the dominant Comptonized component was present for most of this active state and showed a cycle of about 40 d. We argue that the cyclic variations of flux come from the inner disk region, not, e.g., from a jet. We also discuss the observed behavior of 4U 1608–52 in the context of other quasi-persistent low-mass X-ray binaries.

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The study of multipeaked type-I X-ray bursts in the neutron star low-mass X-ray binary 4U 1636 − 536 with RXTE

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3539 ◽

2020 ◽

Vol 501 (1) ◽

pp. 168-178

Author(s):

Chen Li ◽

Guobao Zhang ◽

Mariano Méndez ◽

Jiancheng Wang ◽

Ming Lyu

Keyword(s):

Neutron Star ◽

Flux Ratio ◽

Light Curves ◽

Type I ◽

X Ray ◽

Soft State ◽

Peak Flux ◽

Low Mass ◽

Two Peaks ◽

Second Peak

ABSTRACT We have found and analysed 16 multipeaked type-I bursts from the neutron-star low-mass X-ray binary 4U 1636 − 53 with the Rossi X-ray Timing Explorer (RXTE). One of the bursts is a rare quadruple-peaked burst that was not previously reported. All 16 bursts show a multipeaked structure not only in the X-ray light curves but also in the bolometric light curves. Most of the multipeaked bursts appear in observations during the transition from the hard to the soft state in the colour–colour diagram. We find an anticorrelation between the second peak flux and the separation time between two peaks. We also find that in the double-peaked bursts the peak-flux ratio and the temperature of the thermal component in the pre-burst spectra are correlated. This indicates that the double-peaked structure in the light curve of the bursts may be affected by enhanced accretion rate in the disc, or increased temperature of the neutron star.

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ATLASGAL – Ammonia observations towards the southern Galactic plane

Astronomy and Astrophysics ◽

10.1051/0004-6361/201526384 ◽

2018 ◽

Vol 609 ◽

pp. A125 ◽

Cited By ~ 8

Author(s):

M. Wienen ◽

F. Wyrowski ◽

K. M. Menten ◽

J. S. Urquhart ◽

C. M. Walmsley ◽

...

Keyword(s):

Standard Deviation ◽

Hyperfine Structure ◽

Optical Depth ◽

Line Width ◽

Rotational Temperature ◽

High Mass ◽

Mass Star ◽

Star Forming ◽

Star Forming Regions ◽

Low Mass

Context. The initial conditions of molecular clumps in which high-mass stars form are poorly understood. In particular, a more detailed study of the earliest evolutionary phases is needed. The APEX Telescope Large Area Survey of the whole inner Galactic disk at 870 μm, ATLASGAL, has therefore been conducted to discover high-mass star-forming regions at different evolutionary phases. Aims. We derive properties such as velocities, rotational temperatures, column densities, and abundances of a large sample of southern ATLASGAL clumps in the fourth quadrant. Methods. Using the Parkes telescope, we observed the NH3 (1, 1) to (3, 3) inversion transitions towards 354 dust clumps detected by ATLASGAL within a Galactic longitude range between 300° and 359° and a latitude within ± 1.5°. For a subsample of 289 sources, the N2H+ (1–0) line was measured with the Mopra telescope. Results. We measured a median NH3 (1, 1) line width of ~ 2 km s-1, rotational temperatures from 12 to 28 K with a mean of 18 K, and source-averaged NH3 abundances from 1.6 × 10-6 to 10-8. For a subsample with detected NH3 (2, 2) hyperfine components, we found that the commonly used method to compute the (2, 2) optical depth from the (1, 1) optical depth and the (2, 2) to (1, 1) main beam brightness temperature ratio leads to an underestimation of the rotational temperature and column density. A larger median virial parameter of ~ 1 is determined using the broader N2H+ line width than is estimated from the NH3 line width of ~ 0.5 with a general trend of a decreasing virial parameter with increasing gas mass. We obtain a rising NH3 (1, 1)/N2H+ line-width ratio with increasing rotational temperature. Conclusions. A comparison of NH3 line parameters of ATLASGAL clumps to cores in nearby molecular clouds reveals smaller velocity dispersions in low-mass than high-mass star-forming regions and a warmer surrounding of ATLASGAL clumps than the surrounding of low-mass cores. The NH3 (1, 1) inversion transition of 49% of the sources shows hyperfine structure anomalies. The intensity ratio of the outer hyperfine structure lines with a median of 1.27 ± 0.03 and a standard deviation of 0.45 is significantly higher than 1, while the intensity ratios of the inner satellites with a median of 0.9 ± 0.02 and standard deviation of 0.3 and the sum of the inner and outer hyperfine components with a median of 1.06 ± 0.02 and standard deviation of 0.37 are closer to 1.

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Self-consistent study of the reflection component in 4U1705-44 with XMM-Newton, BeppoSAX and RXTE in the hard and soft state

10.22323/1.147.0015 ◽

2012 ◽

Author(s):

Elise Egron

Keyword(s):

Soft State ◽

Self Consistent ◽

Reflection Component

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Spectral analysis of the low-mass X-ray pulsar 4U 1822-371: Reflection component in a high-inclination system

Astronomy and Astrophysics ◽

10.1051/0004-6361/202140557 ◽

2021 ◽

Author(s):

A. Anitra ◽

T. Di Salvo ◽

R. Iaria ◽

L. Burderi ◽

A.F. Gambino ◽

...

Keyword(s):

Spectral Analysis ◽

X Ray ◽

Low Mass ◽

Reflection Component

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Jets in the soft state in Cyg X-3 caused by advection of the donor magnetic field and unification with low-mass X-ray binaries

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3447 ◽

2019 ◽

Vol 492 (1) ◽

pp. 223-231 ◽

Cited By ~ 4

Author(s):

Xinwu Cao ◽

Andrzej A Zdziarski

Keyword(s):

Magnetic Field ◽

High Mass ◽

Vertical Magnetic Field ◽

Subsequent Formation ◽

X Ray ◽

Soft State ◽

Hard State ◽

Low Mass ◽

X Ray Binaries

ABSTRACT The high-mass accreting binary Cyg X-3 is distinctly different from low-mass X-ray binaries (LMXBs) in having powerful radio and γ-ray emitting jets in its soft spectral state. However, the transition from the hard state to the soft one is first associated with quenching of the hard-state radio emission, as in LMXBs. The powerful soft-state jets in Cyg X-3 form, on average, ∼50 d later. We interpret the initial jet quenching as due to the hard-state vertical magnetic field quickly diffusing away in the thin disc extending to the innermost stable circular orbit in the soft state, or, if that field is produced in situ, also cessation of its generation. The subsequent formation of the powerful jets occurs due to advection of the magnetic field from the donor. We find this happens only above certain threshold accretion rate associated with appearance of magnetically driven outflows. The ∼50 d lag is of the order of the viscous time-scale in the outer disc, while the field advection is much faster. This process does not happen in LMXBs due to the magnetic fluxes available from their donors being lower than that for the wind accretion from the Wolf–Rayet donor of Cyg X-3. In our model, the vertical magnetic field in the hard state, required to form the jets both in Cyg X-3 and LMXBs, is formed in situ rather than advected from the donor. Our results provide a unified scenario of the soft and hard states in both Cyg X-3 and LMXBs.

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Disc and wind in black hole X-ray binary MAXI J1820+070 observed through polarized light during its 2018 outburst

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa096 ◽

2020 ◽

Vol 496 (1) ◽

pp. L96-L100

Author(s):

Ilia A Kosenkov ◽

Alexandra Veledina ◽

Andrei V Berdyugin ◽

Vadim Kravtsov ◽

Vilppu Piirola ◽

...

Keyword(s):

Black Hole ◽

Polarized Light ◽

Position Angle ◽

Intrinsic Polarization ◽

Data Set ◽

X Ray ◽

Soft State ◽

Hard State ◽

Low Mass ◽

Optical Flux

ABSTRACT We describe the first complete polarimetric data set of the entire outburst of a low-mass black hole X-ray binary system and discuss the constraints for geometry and radiative mechanisms it imposes. During the decaying hard state, when the optical flux is dominated by the non-thermal component, the observed polarization is consistent with the interstellar values in all filters. During the soft state, the intrinsic polarization of the source is small, ∼0.15 per cent in B and V filters, and is likely produced in the irradiated disc. A much higher polarization, reaching ∼0.5 per cent in V and R filters, at a position angle of ∼25○ observed in the rising hard state coincides in time with the detection of winds in the system. This angle coincides with the position angle of the jet. The detected optical polarization is best explained by scattering of the non-thermal (hot flow or jet base) radiation in an equatorial wind.

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