The young Be-star binary Circinus X-1

AbstractCir X-1 is a young X-ray binary exhibiting X-ray flux changes of four orders of magnitude over several decades. It has been observed many times since the launch of the Chandra X-ray Observatory with high energy transmission grating spectrometer and each time the source gave us a vastly different look. At its very lowest X-ray flux we found a single 1.7 keV blackbody spectrum with an emission radius of 0.5 km. Since the neutron star in Cir X-1 is only few thousand years old we identify this as emission from an accretion column since at this youth the neutron star is assumed to be highly magnetized. At an X-ray flux of 1.8×10−11 erg cm−2 s−1 this implies a moderate magnetic field of a few times of 1011 G. The photoionized X-ray emission line properties at this low flux are consistent with B5-type companion wind. We suggest that Cir X-1 is a very young Be-star binary.

Download Full-text

The thermal-radiative wind in the neutron star low-mass X-ray binary GX 13 + 1

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2254 ◽

2020 ◽

Vol 497 (4) ◽

pp. 4970-4980

Author(s):

Ryota Tomaru ◽

Chris Done ◽

Ken Ohsuga ◽

Hirokazu Odaka ◽

Tadayuki Takahashi

Keyword(s):

Neutron Star ◽

Velocity Structure ◽

Isotropic Turbulence ◽

Azimuthal Velocity ◽

High Energy ◽

Absorption Lines ◽

X Ray ◽

Transmission Grating ◽

Star Binary ◽

Spectrometer Data

ABSTRACT We fit the observed high-ionization X-ray absorption lines in the neutron star binary GX13 + 1 with a full simulation of a thermal-radiative wind. This uses a radiation hydrodynamic code coupled to Monte Carlo radiation transfer to compute the observed line profiles from hydrogen and helium-like iron and nickel, including all strong K α and K β transitions. The wind is very strong as this object has a very large disc and is very luminous. The absorption lines from Fe K α are strongly saturated as the ion columns are large, so the line equivalent widths depend sensitively on the velocity structure. We additionally simulate the lines including isotropic turbulence at the level of the azimuthal and radial velocities. We fit these models to the Fe xxv and xxvi absorption lines seen in the highest resolution Chandra third-order high-energy transmission grating spectrometer data. These data already rule out the addition of turbulence at the level of the radial velocity of ∼500 km s−1. The velocity structure predicted by the thermal-radiative wind alone is a fairly good match to the observed profile, with an upper limit to additional turbulence at the level of the azimuthal velocity of ∼100 km s−1. This gives stringent constraints on any remaining contribution from magnetic acceleration.

Download Full-text

A soft X-ray study of type I active galactic nuclei observed with Chandra high-energy transmission grating spectrometer

Monthly Notices of the Royal Astronomical Society ◽

10.1111/j.1365-2966.2007.11993.x ◽

2007 ◽

Vol 379 (4) ◽

pp. 1359-1372 ◽

Cited By ~ 131

Author(s):

B. McKernan ◽

T. Yaqoob ◽

C. S. Reynolds

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

High Energy ◽

Type I ◽

Energy Transmission ◽

X Ray ◽

Transmission Grating ◽

Grating Spectrometer

Download Full-text

SALT observations of the supernova remnant MCSNR J0127−7332 and its associated Be X-ray binary SXP 1062 in the SMC

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab679 ◽

2021 ◽

Vol 503 (3) ◽

pp. 3856-3866

Author(s):

V V Gvaramadze ◽

A Y Kniazev ◽

J S Gallagher ◽

L M Oskinova ◽

Y-H Chu ◽

...

Keyword(s):

Neutron Star ◽

Emission Line ◽

Supernova Remnant ◽

Supernova Explosion ◽

High Mass ◽

Expansion Velocity ◽

X Ray ◽

Orbital Phase ◽

Be Star ◽

The Moment

ABSTRACT We report the results of optical spectroscopy of the Small Magellanic Cloud supernova remnant (SNR) MCSNR J0127−7332 and the mass donor Be star, 2dFS 3831, in its associated high-mass X-ray binary SXP 1062 carried out with the Southern African Large Telescope. Using high-resolution long-slit spectra, we measured the expansion velocity of the SNR shell of ${\approx} 140 \, {\rm \, km\, s^{-1}}$, indicating that MCSNR J0127−7332 is in the radiative phase. We found that the observed line ratios in the SNR spectrum can be understood if the local interstellar medium is ionized by 2dFS 3831 and/or OB stars around the SNR. We propose that MCSNR J0127−7332 is the result of supernova explosion within a bubble produced by the stellar wind of the supernova progenitor and that the bubble was surrounded by a massive shell at the moment of supernova explosion. We estimated the age of MCSNR J0127−7332 to be ${\lesssim} 10\, 000$ yr. We found that the spectrum of 2dFS 3831 changes with orbital phase. Namely, the equivalent width of the H α emission line decreased by ≈40 per cent in ≈130 d after periastron passage of the neutron star and then almost returned to its original value in the next ≈100 d. Also, the spectrum of 2dFS 3831 obtained closest to the periastron epoch (about 3 weeks after the periastron) shows a noticeable emission line of He ii λ4686, which disappeared in the next 2 weeks. We interpret these changes as a result of the temporary perturbation and heating of the disc as the neutron star passes through it.

Download Full-text

The Discovery of Broad P Cygni X-Ray Lines from Circinus X-1 with the [ITAL]Chandra[/ITAL] High-Energy Transmission Grating Spectrometer

The Astrophysical Journal ◽

10.1086/317313 ◽

2000 ◽

Vol 544 (2) ◽

pp. L123-L127 ◽

Cited By ~ 74

Author(s):

W. N. Brandt ◽

N. S. Schulz

Keyword(s):

High Energy ◽

Energy Transmission ◽

X Ray ◽

Transmission Grating ◽

Grating Spectrometer

Download Full-text

X-Ray Transients Observed with MAXI

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318002429 ◽

2017 ◽

Vol 14 (S339) ◽

pp. 144-144

Author(s):

N. Kawai

Keyword(s):

Neutron Star ◽

Space Station ◽

X Rays ◽

International Space ◽

X Ray ◽

Black Hole Binaries ◽

Stellar Flares ◽

Orbital Revolution ◽

Be Star ◽

Star Binary

AbstractMAXI (Monitor of All-sky X-ray Image) is an astronomical mission onboard the International Space Station. It started observations in August 2009. The Gas Slit Camera of MAXI is sensitive to X-rays in the energy range 2–30 keV. Most of the sky is scanned every 90 min with the orbital revolution of the ISS. With this unbiased monitoring, MAXI has detected numerous outbursts from known and unknown X-ray sources. MAXI discovered 18 X-ray novæ in seven years, including seven neutron star binaries, six black hole binaries (+candidates) and four unidentified sources. Other results include detections of superluminous stellar flares, a super-Eddington luminous flare from a white dwarf+Be Star binary near the SMC, and monitoring of recurrent outbursts from Be neutron-star binaries. Variations in X-ray-bright AGNs such as Cen A and Mrk 421 have been also monitored. This talk presented the highlights of the MAXI observations of variable sources, including the search for X-ray counterparts of gravitational-wave events.

Download Full-text

Discovery of X-ray pulsations in the Be/X-ray binary IGR J06074+2205

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732533 ◽

2018 ◽

Vol 613 ◽

pp. A52 ◽

Cited By ~ 1

Author(s):

P. Reig ◽

A. Zezas

Keyword(s):

Neutron Star ◽

Model Fitting ◽

High Energy ◽

X Rays ◽

Energy Bands ◽

X Ray ◽

Be Star ◽

Best Fitting ◽

Open Question ◽

Star Surface

Context. IGR J06074+2205 is a poorly studied X-ray source with a Be star companion. It has been proposed to belong to the group of Be/X-ray binaries (BeXBs). In BeXBs, accretion onto the neutron star occurs via the transfer of material from the Be star’s circumstellar disk. Thus, in the absence of the disk, no X-ray should be detected. Aims. The main goal of this work is to study the quiescent X-ray emission of IGR J06074+2205 during a disk-loss episode. Methods. We obtained light curves at different energy bands and a spectrum covering the energy range 0.4–12 keV. We used Fourier analysis to study the aperiodic variability and epoch folding methods to study the periodic variability. Model fitting to the energy spectrum allowed us to identify the possible physical processes that generated the X-rays. Results. We show that at the time of the XMM-Newton observation, the decretion disk around the Be star had vanished. Still, accretion appears as the source of energy that powers the high-energy radiation in IGR J06074+2205. We report the discovery of X-ray pulsations with a pulse period of 373.2 s and a pulse fraction of ~50%. The 0.4–12 keV spectrum is well described by an absorbed power law and blackbody components with the best fitting parameters: NH = (6.2 ± 0.5) × 1021 cm−2, kTbb = 1.16 ± 0.03 keV, and Γ = 1.5 ± 0.1. The absorbed X-ray luminosity is LX = 1.4 × 1034 erg s−1 assuming a distance of 4.5 kpc. Conclusions. The detection of X-ray pulsations confirms the nature of IGR J06074+2205 as a BeXB. We discuss various scenarios to explain the quiescent X-ray emission of this pulsar. We rule out cooling of the neutron star surface and magnetospheric emission and conclude that accretion is the most likely scenario. The origin of the accreted material remains an open question.

Download Full-text