Broad-band observations of the Be/X-ray binary pulsar RX J0440.9+4431: discovery of a cyclotron absorption line

ABSTRACT We report the results obtained from a detailed timing and spectral studies of Be/X-ray binary pulsar 2S 1417−624 using data from Swift and NuSTAR observatories. The observations were carried out at the peak of a giant outburst of the pulsar in 2018. X-ray pulsations at ∼17.475 s were detected in the source light curves up to 79 keV. The evolution of the pulse profiles with energy was found to be complex. A four-peaked profile at lower energies gradually evolved into a double-peak structure at higher energies. The pulsed fraction of the pulsar, calculated from the NuSTAR observation was found to follow an anticorrelation trend with luminosity as observed during previous giant X-ray outburst studies in 2009. The broad-band spectrum of the pulsar is well described by a composite model consisting of a cut-off power-law model modified with the interstellar absorption, a thermal blackbody component with a temperature of ≈1 keV, and a Gaussian function for the 6.4 keV iron emission line. Though the pulsar was observed at the peak of the giant outburst, there was no signature of presence of any cyclotron line feature in the spectrum. The radius of the blackbody emitting region was estimated to be ≈2 km, suggesting that the most probable site of its origin is the stellar surface of the neutron star. Physical models were also explored to understand the emission geometry of the pulsar and are discussed in the paper.

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Discovery of a cyclotron absorption line in the spectrum of the binary X-ray pulsar 4U 1538 - 52 observed by GINGA

The Astrophysical Journal ◽

10.1086/168614 ◽

1990 ◽

Vol 353 ◽

pp. 274 ◽

Cited By ~ 52

Author(s):

George W. Clark ◽

Jonathan W. Woo ◽

Fumiaki Nagase ◽

Kazuo Makishima ◽

Taro Sakao

Keyword(s):

Absorption Line ◽

X Ray ◽

Cyclotron Absorption

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New measurements of the cyclotron line energy in Cen X-3

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3477 ◽

2020 ◽

Vol 500 (3) ◽

pp. 3454-3461

Author(s):

Gunjan Tomar ◽

Pragati Pradhan ◽

Biswajit Paul

Keyword(s):

Broad Band ◽

Resonant Scattering ◽

High Energy ◽

Emission Lines ◽

Power Law Model ◽

Pulse Profile ◽

Line Energy ◽

X Ray ◽

Cyclotron Absorption ◽

Cyclotron Line

ABSTRACT We report results from the analysis of data from two observations of the accreting binary X-ray pulsar Cen X-3 carried out with the broad-band X-ray observatories Suzaku and NuSTAR. The pulse profile is dominated by a broad single peak and show some energy dependence with two additional weak pulse peaks at energies below 15 and 25 keV, respectively. The broad-band X-ray spectrum for 0.8–60.0 keV for Suzaku and 3.0–60.0 keV for NuSTAR is fitted well with high-energy cut-off power-law model along with soft-excess, multiple iron emission lines and a cyclotron absorption. The cyclotron line energy is found to be $30.29^{+0.68}_{-0.61}$ and $29.22^{+0.28}_{-0.27}$ keV, respectively, in the Suzaku and NuSTAR spectra. We make a comparison of these two measurements with four previous measurements of Cyclotron Resonant Scattering Feature (CRSF) in Cen X-3 obtained with Ginga, BeppoSAX, and RXTE. We find no evidence for a dependence of the CRSF on luminosity. Except for one CRSF measurement with BeppoSAX , the remaining measurements are consistent with a CRSF energy in the range of 29.5–30.0 keV over a luminosity range of 1.1–5.4 × 1037 erg s−1 different from several other sources that show considerable CRSF variation in the same luminosity range.

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Revisiting the spectral and timing properties of 4U 1909+07 with NuSTAR and Astrosat

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2604 ◽

2020 ◽

Vol 498 (4) ◽

pp. 4830-4838 ◽

Cited By ~ 1

Author(s):

Gaurava K Jaisawal ◽

Sachindra Naik ◽

Wynn C G Ho ◽

Neeraj Kumari ◽

Prahlad Epili ◽

...

Keyword(s):

Broad Band ◽

High Energy ◽

High Mass ◽

X Rays ◽

Pulse Profile ◽

X Ray ◽

Beam Geometry ◽

Cyclotron Absorption ◽

Using Data ◽

Wind Distribution

ABSTRACT We present the results obtained from the analysis of high-mass X-ray binary pulsar 4U 1909+07 using NuSTAR and Astrosat observations in July 2015 and 2017, respectively. X-ray pulsations at ≈604 s are clearly detected in our study. Based on the long-term spin-frequency evolution, the source is found to spun-up in the last 17 yr. We observed a strongly energy-dependent pulse profile that evolved from a complex broad structure in soft X-rays into a profile with a narrow emission peak followed by a plateau in energy ranges above 20 keV. This behaviour ensured a positive correlation between the energy and pulse fraction. The pulse profile morphology and its energy evolution are almost similar during both the observations, suggesting a persistent emission geometry of the pulsar over time. The broad-band energy spectrum of the pulsar is approximated by an absorbed high-energy exponential cut-off power-law model with iron emission lines. In contrast to the previous report, we found no statistical evidence for the presence of cyclotron absorption features in the X-ray spectra. We performed phase-resolved spectroscopy using data from the NuSTAR observation. Our results showed a clear signature of absorbing material at certain pulse phases of the pulsar. These findings are discussed in terms of stellar wind distribution and its effect on the beam geometry of this wind-fed accreting neutron star. We also reviewed the subsonic quasi-spherical accretion theory and its implication on the magnetic field of 4U 1909+07 depending on the global spin-up rate.

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NuSTARdiscovery of a cyclotron absorption line in the transient X-ray pulsar 2S 1553−542

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stv2849 ◽

2016 ◽

Vol 457 (1) ◽

pp. 258-266 ◽

Cited By ~ 12

Author(s):

Sergey S. Tsygankov ◽

Alexander A. Lutovinov ◽

Roman A. Krivonos ◽

Sergey V. Molkov ◽

Peter J. Jenke ◽

...

Keyword(s):

Absorption Line ◽

X Ray ◽

Cyclotron Absorption

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Properties of the transient X-ray pulsar Swift J1816.7–1613 and its optical companion

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834635 ◽

2019 ◽

Vol 622 ◽

pp. A198 ◽

Cited By ~ 1

Author(s):

Armin Nabizadeh ◽

Sergey S. Tsygankov ◽

Dmitrij I. Karasev ◽

Juhani Mönkkönen ◽

Alexander A. Lutovinov ◽

...

Keyword(s):

Magnetic Field ◽

Neutron Star ◽

Energy Spectrum ◽

Timing Analysis ◽

Broad Band ◽

Type I ◽

Quiescent State ◽

Band Energy ◽

X Ray ◽

Cyclotron Absorption

We present results of investigation of the poorly studied X-ray pulsar Swift J1816.7–1613 during its transition from the type I outburst to the quiescent state. Our studies are based on the data obtained from X-ray observatories Swift, NuSTAR, and Chandra alongside with the latest IR data from UKIDSS/GPS and Spitzer/GLIMPSE surveys. The aim of the work is to determine the parameters of the system, namely the strength of the neutron star magnetic field and the distance to the source, which are required for the interpretation of the source behaviour in the framework of physically motivated models. No cyclotron absorption line was detected in the broad-band energy spectrum. However, the timing analysis hints at the typical for the X-ray pulsars magnetic field from a few ×1011 to a few ×1012 G. We also estimated the type of the IR-companion as a B0-2e star located at a distance of 7–13 kpc.

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Study of the X-ray pulsar IGR J19294+1816 with NuSTAR: Detection of cyclotron line and transition to accretion from the cold disk

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833786 ◽

2019 ◽

Vol 621 ◽

pp. A134 ◽

Cited By ~ 3

Author(s):

Sergey S. Tsygankov ◽

Victor Doroshenko ◽

Alexander A. Mushtukov ◽

Alexander A. Lutovinov ◽

Juri Poutanen

Keyword(s):

Energy Spectrum ◽

Absorption Line ◽

Orbital Period ◽

Timing Analysis ◽

Type I ◽

Quiescent State ◽

X Ray ◽

Cyclotron Absorption ◽

Cyclotron Line

In the work we present the results of two deep broadband observations of the poorly studied X-ray pulsar IGR J19294+1816 obtained with the NuSTAR observatory. The source was observed during Type I outburst and in the quiescent state. In the bright state a cyclotron absorption line in the energy spectrum was discovered at Ecyc = 42.8 ± 0.7 keV. Spectral and timing analysis prove the ongoing accretion also during the quiescent state of the source. Based on the long-term flux evolution, particularly on the transition of the source to the bright quiescent state with luminosity around 1035 erg s−1, we conclude that IGR J19294+1816 switched to the accretion from the “cold” accretion disk between Type I outbursts. We also report the updated orbital period of the system.

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