First multicolour polarimetry of TeV γ-ray binary HESS J0632+057 close to periastron passage

Yudin, R. V.; Potter, S.; Townsend, L. J.

doi:10.1093/mnras/stw2676

Cited by 4 publications

(3 citation statements)

References 28 publications

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“…The polarization angle did not change clearly. Yudin et al (2017) have reported multicolor polarimetry in the optical band at different orbital phases [18]. This work shows a result consistent with theirs: the polarization degree and angle in the R-band were 3.83 ± 0.15%, 171.3 ± 3 degree (JD 2,457,369) and 3.74 ± 0.15%, 167.9 ± 3 degree (JD 2,457,369).…”

Section: Hess J0632+057supporting

confidence: 89%

“…The X-ray and gamma-ray flux decrease to a minimum ("dip") between the two outbursts: φ ∼ 0.5. There have been few reports regarding orbital modulation in the optical and near-infrared bands to date, but polarization variation around the periastron has been reported [18]. Line-profile variabilities have been shown in the Balmer lines, suggesting Be disk perturbation at φ ∼ 0.5-1, with the timescale of ∼60 and ∼150 days [19,20].…”

Section: Introductionmentioning

confidence: 99%

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Optical and Near-Infrared Monitoring of Gamma-ray Binaries Hosting Be Stars

Moritani

Kawachi

2021

Universe

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Optical and near-infrared observations are compiled for the three gamma-ray binaries hosting Be stars: PSR B1259−63, LSI+61 303, and HESS J0632+057. The emissions from the Be disk are considered to vary according to the changes in its structure, some of which are caused by interactions with the compact object (e.g., tidal forces). Due to the high eccentricity and large orbit of these systems, the interactions—and, hence the resultant observables—depend on the orbital phase. To explore such variations, multi-band photometry and linear polarization were monitored for the three considered systems, using two 1.5 m-class telescopes: IRSF at the South African Astronomical Observatory and Kanata at the Higashi–Hiroshima Observatory.

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Section: Hess J0632+057supporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Optical and Near-Infrared Monitoring of Gamma-ray Binaries Hosting Be Stars

Moritani

Kawachi

2021

Universe

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“…Recently, Yudin et al (2017) reported multi-wavelength polarization at two phases in one orbital cycle, which showed variation in both polarization degree and polarization angle. They discussed that the variability is possibly related with additional source or disk perturbation which occurs at periastron.…”

Section: The New Orbit Of Hess J0632 + 057 and Interpretations Of Phe...mentioning

confidence: 99%

Orbital solution leading to an acceptable interpretation for the enigmatic gamma-ray binary HESS J0632+057

Moritani,

Kawano,

Chimasu

et al. 2018

Preprint

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High-dispersion spectroscopic monitoring of HESS J0632 + 057 has been carried out over four orbital cycles in order to search for orbital modulation, covering the entire orbital phase. We have measured radial velocity of Hα emission line with the method introduced by Shafter et al. (1986), which has been successfully applied to some Be stars. The velocity is seen to increase much earlier than expected for the orbital period of 315 days, and much more steeply than expected at around "apastron". The period of the Hα modulation is found to be as 308 +26 −23 days. We have also analyzed Swift/XRT data from 2009 to 2015 to study the orbital modulation, selecting the data with good statistics (≥ 30 counts). With additional two-year data to the 1 previous works, the orbital period has been updated to 313 +11 −8 days, which is consistent with the previous X-ray periods and the spectroscopic one. The past XMM-Newton and Chandra observations prefer the period of 313 days. With the new period, assuming that Hα velocities accurately trace the motion of the Be star, we have derived a new set of the orbital parameters.In the new orbit, which is less eccentric (e ∼ 0.6), two outbursts occur after apastron, and just after periastron. Besides, the column density in bright phase (4.7 +0.9 −08 × 10 21 cm −2 ) is higher than in faint phase (2.2 ± 0.5 × 10 21 cm −2 ). These facts suggest that outbursts occur when the compact object passes nearby/through the Be disk. The mass function implies that mass of the compact object is less than 2.5 M sun assuming that the mass of the Be star is 13.2-18.2 M sun (Aragona et al. 2010) unless the inclination is extremely small. The photon index indicates that the spectra becomes softer when the system is bright. These suggest that the compact object is a pulsar.

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Orbital solution leading to an acceptable interpretation for the enigmatic gamma-ray binary HESS J0632+057

Moritani

Kawano

Chimasu

et al. 2018

Publications of the Astronomical Society of Japan

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High-dispersion spectroscopic monitoring of HESS J0632+057 has been carried out over four orbital cycles in order to search for orbital modulation, covering the entire orbital phase. We have measured the radial velocity of the Hα emission line with the method introduced by Shafter, Szkody, and Thorstensen (1986, ApJ, 308, 765), which has been successfully applied to some Be stars. The velocity is seen to increase much earlier than expected for the orbital period of 315 d, and much more steeply than expected at around “apastron.” The period of the Hα modulation is found to be $308^{+26}_{-23}$ d. We have also analyzed Swift/XRT data from 2009 to 2015 to study the orbital modulation, selecting the data with good statistics (≥30 counts). With additional two-year data to the previous works, the orbital period has been updated to $313^{+11}_{-8}$ d, which is consistent with the previous X-ray periods and the spectroscopic one. Previous XMM-Newton and Chandra observations prefer a period of 313 d. With the new period, assuming that Hα velocities accurately trace the motion of the Be star, we have derived a new set of orbital parameters. In the new orbit, which is less eccentric (e ≃ 0.6), two outbursts occur: after apastron and just after periastron. Also, the column density in bright phase ($4.7^{+0.9}_{-08}\times 10^{21} \, \mathrm{cm}^{-2}$) is higher than in faint phase (2.2 ± 0.5 × 1021 cm−2). These facts suggest that outbursts occur when the compact object passes nearby/through the Be disk. The mass function implies that the mass of the compact object is less than 2.5 M⊙, assuming that the mass of the Be star is 13.2–18.2 M⊙ (Aragona et al. 2010, ApJ, 724, 306), unless the inclination is extremely small. The photon index indicates that the spectra become softer when the system is bright. These suggest that the compact object is a pulsar.

show abstract

First multicolour polarimetry of TeV γ-ray binary HESS J0632+057 close to periastron passage

Cited by 4 publications

References 28 publications

Optical and Near-Infrared Monitoring of Gamma-ray Binaries Hosting Be Stars

Optical and Near-Infrared Monitoring of Gamma-ray Binaries Hosting Be Stars

Orbital solution leading to an acceptable interpretation for the enigmatic gamma-ray binary HESS J0632+057

Orbital solution leading to an acceptable interpretation for the enigmatic gamma-ray binary HESS J0632+057

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