X-Ray Pulsar XTE J1858+034: Discovery of the Cyclotron Line and the Revised Optical Identification

Tsygankov, Sergey S.; Lutovinov, A.; Molkov, S.; Djupvik, Anlaug A.; Karasev, D. I.; Doroshenko, V.; Mushtukov, Alexander A.; Malacaria, C.; Kretschmar, P.; Poutanen, Juri

doi:10.3847/1538-4357/abddbd

Cited by 14 publications

(10 citation statements)

References 34 publications

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“…Using the XSPEC tool recorn, it was found that the absorption line parameters do not change significantly if the normalization of the background spectrum is increased by up to 50%, thus strengthening the interpretation of the absorption feature as real and not due to artifacts. The feature was also observed in phase-resolved spectra presented in the accompanying paper by Tsygankov et al (2021). Interpreting the feature at 48 keV as a CRSF and assuming a gravitational redshift of z g = 0.3 (for an NS mass and radius of 1.4 M e and 10 km, respectively), a magnetic field strength of B = (5.4 ± 0.1) × 10 12 G is obtained.…”

Section: Spectral Analysissupporting

confidence: 52%

“…In addition, the Gaia counterpart is at an angular offset of 103″ from, and thus clearly not associated with, the optical counterpart proposed by Reig et al (2005). This question is discussed in more detail in the accompanying paper by Tsygankov et al (2021), who identified a counterpart based on Chandra and ground telescope observations with a probable distance of 7-14 kpc.…”

Section: Introductionmentioning

confidence: 95%

“…Here we study its spectral and timing characteristics and finally form a consistent general overview for the X-ray behavior of XTE J1858+034, including a distance estimate based on accretiontorque theory. The analysis presented here is complemented by the work in the accompanying paper by Tsygankov et al (2021).…”

Section: Introductionmentioning

confidence: 99%

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The X-Ray Pulsar XTE J1858+034 Observed with NuSTAR and Fermi/GBM: Spectral and Timing Characterization plus a Cyclotron Line

Malacaria

Kretschmar

Madsen

et al. 2021

ApJ

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Accreting X-ray pulsars (XRPs) undergo luminous X-ray outbursts during which the spectral and timing behavior of the neutron star can be studied in detail. We analyze a NuSTAR observation of the XRP XTE J1858+034 during its outburst in 2019. The spectrum is fit with a phenomenological, a semiempirical, and a physical spectral model. A candidate cyclotron line is found at 48 keV, implying a magnetic field of 5.4 × 1012 G at the site of emission. This is also supported by the physical best-fit model. We propose an orbital period of about 81 days based on the visual inspection of the X-ray outburst recurrence time. Based on Fermi/GBM data, the standard disk accretion-torque theory allowed us to infer a distance of 10.9 ± 1.0 kpc. Pulse profiles are single-peaked and show a pulsed fraction that is strongly energy-dependent at least up to 40 keV.

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Section: Spectral Analysissupporting

confidence: 52%

Section: Introductionmentioning

confidence: 95%

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The X-Ray Pulsar XTE J1858+034 Observed with NuSTAR and Fermi/GBM: Spectral and Timing Characterization plus a Cyclotron Line

Malacaria

Kretschmar

Madsen

et al. 2021

ApJ

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“…To estimate the extinction value in the direction to the IR-star and its distance, we used the method successively applied previously by Karasev et al (2015); Nabizadeh et al (2019); Tsygankov et al (2021); Salganik et al (2022) for different sources. By comparing the measured color of the source (𝐻 − 𝐾) 0.945 with intrinsic colors (𝐻 − 𝐾) 0 of various star classes Wegner (2000Wegner ( , 2006Wegner ( , 2007Wegner ( , 2014Wegner ( , 2015, we can estimate the corresponding reddening 𝐸 (𝐻 −𝐾) = (𝐻 −𝐾) − (𝐻 −𝐾) 0 and extinction 𝐴 𝐾 using a standard extinction law (Cardelli et al 1989), as Swift J1808.4−1754 is located far away from the Galactic bulge direction.…”

Section: Distance Estimationmentioning

confidence: 99%

Discovery of a pulse-phase-transient cyclotron line in the X-ray pulsar Swift J1808.4-1754 and identification of an optical companion

Salganik,

Tsygankov,

Lutovinov

et al. 2022

Preprint

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In this work, the temporal and spectral properties of the poorly studied X-ray pulsar Swift J1808.4−1754 were investigated in the 0.8-79 keV energy range based on the data from the NuSTAR and Swift observatories collected during the 2014 outburst. Strong pulsations with a period of 909.73 ± 0.03 s were detected in the source light curve, with the pulsed fraction demonstrating a nonmonotonic dependence on the energy with a local minimum around 17-22 keV. Phase lags in one of the pulse profile components, reaching the maximal value approximately at the same energy, were discovered. The pulse phase-averaged spectrum of the source has a power-law shape with an exponential cutoff at high energies, which is typical of X-ray pulsars. Pulse phase-resolved spectroscopy revealed the presence of a pulse phase-transient cyclotron absorption line at ∼21 keV, allowing us to estimate the neutron star magnetic field of 2.4 × 10 12 G. This makes Swift J1808.4−1754 a member of very small family of X-ray pulsars with a pulse-phase-transient cyclotron line in a narrow phase range. The data from the Nordic Optical Telescope allowed us to study the properties of the IR companion in the system and to conclude that most probably it is a Be-type star located at a distance of 5-8 kpc.

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“…The photogeometric distance (recommended by the authors as more accurate) to star #1 is 6.1 +2.0 −1.0 kpc and to star #2 is 8.7 +3.6 −5.1 kpc. To check how these values compare with the estimated star classes we investigated both stars using the method described and successively applied by Karasev et al (2015), Nabizadeh et al (2019), andTsygankov et al (2021). Taking the absolute values of stars of various classes in the and photometric filters from Wegner (2000Wegner ( , 2006Wegner ( , 2007Wegner ( , 2014Wegner ( , 2015 and applying corrections for the extinction and the distance, we determined at what distance they should be located and how strongly they should be extincted to match the observed magnitudes of the investigated companion in the and filters.…”

Section: Distance Estimationmentioning

confidence: 99%

On the nature of the X-ray pulsar XTE J1859+083 and its broadband properties

Salganik,

Tsygankov,

Djupvik

et al. 2021

Preprint

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This work is devoted to the study of the broadband 0.8-79 keV spectral and timing properties of the poorly studied X-ray pulsar XTE J1859+083 during its 2015 outburst based on the data from the NuSTAR and Swift observatories. We show that the source pulse profile has complex shape that depends on the energy band. Pulse fraction of XTE J1859+083 has constant value around 35% in the broad energy band, this behaviour is atypical for X-ray pulsars. At the same time its energy spectrum is typical of this class of objects and has a power-law shape with an exponential cutoff at high energies. No cyclotron absorption line was discovered in the source spectrum. On the basis of indirect method and the absence of a cyclotron line, an estimation was made for the magnetic field strength as less than 5 × 10 11 G or belonging to the interval from 5 × 10 12 to 2.0 +0.9 −1.2 × 10 13 G. Data from the NOT and SALT telescopes as well as optical and IR sky surveys allowed us also to study the nature of its optical companion. We have proposed and studied new possible candidates for the optical companion of XTE J1859+083 and the most likely candidate was identified. The results of the optical and IR photometry and spectroscopy of these possible companions showed that the system is a Be X-ray binary, showing Br , He and strong H spectral lines.

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X-Ray Pulsar XTE J1858+034: Discovery of the Cyclotron Line and the Revised Optical Identification

Cited by 14 publications

References 34 publications

The X-Ray Pulsar XTE J1858+034 Observed with NuSTAR and Fermi/GBM: Spectral and Timing Characterization plus a Cyclotron Line

The X-Ray Pulsar XTE J1858+034 Observed with NuSTAR and Fermi/GBM: Spectral and Timing Characterization plus a Cyclotron Line

Discovery of a pulse-phase-transient cyclotron line in the X-ray pulsar Swift J1808.4-1754 and identification of an optical companion

On the nature of the X-ray pulsar XTE J1859+083 and its broadband properties

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