Connection between orbital modulation of H<i>α</i>and gamma-rays in the Be/X-ray binary LS I+61°303

Zamanov, R.; Martı́, Josep; Stoyanov, K. A.; Borissova, A.; Tomov, N. A.

doi:10.1051/0004-6361/201322936

Cited by 8 publications

(12 citation statements)

References 36 publications

(36 reference statements)

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“…1. As can be seen, the data cover two different seasons (centered in autumn) and show the already known orbital variability (see, e.g., Zamanov et al 2014). The folded lightcurves for the first and second season and their sinusoidal fits are shown in Fig.…”

Section: Resultsmentioning

confidence: 63%

“…The optical photometric observations show a lag of ∼0.1 in orbital phase with respect to the radio outburst, and ∼0.3 with respect to the X-ray outbursts for equivalent superorbital phases one cycle apart. The EW Hα maxima occur at orbital phases similar to the radio outbursts for similar superorbital phases one cycle apart, while in the averaged data of Zamanov et al (2013Zamanov et al ( , 2014 the maxima occur during the rising of the radio flux density. The different slopes in Fig.…”

Section: Data Set Mjd Opticalmentioning

confidence: 76%

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Evidence of coupling between the thermal and nonthermal emission in the gamma-ray binary LS I +61 303

Paredes-Fortuny

Ribó

Bosch‐Ramon

et al. 2015

A&A

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The gamma-ray binary LS I +61 303 is composed of a Be star and a compact companion orbiting in an eccentric orbit. Variable flux modulated with the orbital period of ∼26.5 d has been detected from radio to very high-energy gamma rays. In addition, the system presents a superorbital variability of the phase and amplitude of the radio outbursts with a period of ∼4.6 yr. We present optical photometric observations of LS I +61 303 spanning ∼1.5 yr and contemporaneous Hα equivalent width (EW Hα ) data. The optical photometry shows, for the first time, that the known orbital modulation suffers a positive orbital phase shift and an increase in flux for data obtained 1-yr apart. This behavior is similar to that already known at radio wavelengths, indicating that the optical flux follows the superorbital variability as well. The orbital modulation of the EW Hα presents the already known superorbital flux variability but shows, also for the first time, a positive orbital phase shift. In addition, the optical photometry exhibits a lag of ∼0.1-0.2 in orbital phase with respect to the EW Hα measurements at similar superorbital phases, and presents a lag of ∼0.1 and ∼0.3 orbital phases with respect noncontemperaneous radio and X-ray outbursts, respectively. The phase shifts detected in the orbital modulation of thermal indicators, such as the optical flux and the EW Hα , are in line with the observed behavior for nonthermal indicators, such as X-ray or radio emission. This shows that there is a strong coupling between the thermal and nonthermal emission processes in the gamma-ray binary LS I +61 303. The orbital phase lag between the optical flux and the EW Hα is naturally explained considering different emitting regions in the circumstellar disk, whereas the secular evolution might be caused by the presence of a moving one-armed spiral density wave in the disk.

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Section: Resultsmentioning

confidence: 63%

Section: Data Set Mjd Opticalmentioning

confidence: 76%

Evidence of coupling between the thermal and nonthermal emission in the gamma-ray binary LS I +61 303

Paredes-Fortuny

Ribó

Bosch‐Ramon

et al. 2015

A&A

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“…The orbit of LS I +61°303 is elliptical with a period P o of 26.496 days (Gregory 2002) and an eccetricity of e ≃ 0.54 (Aragona et al 2009). Orbital flux or emission line variations have been detected at all wavelengths, from radio (e.g., Paredes et al 1990;Marcote et al 2016), optical (e.g., Grundstrom et al 2007;Zamanov et al 2014), X-ray (e.g., Paredes et al 1997), to γ-ray GeV and TeV (e.g., Abdo et al 2009;Albert et al 2009). Very interestingly, a long-term 1667±8 days periodic signal (Gregory 2002) is also seen at nearly all the wavelengths (radio: Ahnen et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Superorbital Modulation at GeV Energies in the γ-Ray Binary LS I + 61°303

Xing

Wang

Takata

2017

ApJ

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We report the results from our analysis of 8 years of the data for the γ-ray binary LS I +61°303, obtained with the Large Area Telescope onboard the Fermi Gamma-Ray Space Telescope. We find a significant dip around the binary's periastron in the superorbital light curves, and by fitting the light curves with a sinusoidal function, clear phase shifts are obtained. The superorbital modulation seen in the binary has been long known and different scenarios have been proposed. Based on our results, we suggest that the circumstellar disk around the Be companion of this binary may have a non-axisymmetric structure, which rotates at the superorbital period of 1667 days. As a result, the density of the ambient material around the compact star of the binary changes along the binary orbit over the superorbital period, causing the phase shifts in the modulation, and around periastron, the compact star probably enters the Be disk or switches the mode of its emission due to the intereaction with the disk, causing the appearance of the dip. We discuss the implications of this possible scenario to the observed superorbital properties at multiple frequencies.

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“…The system is well known with both orbital modulation and super-orbital modulation (∼1700 days) from radio to gamma-rays. Zamanov et al (2014) studied the correlation between Hα line-profile parameters, V-magnitude, and Fermi-LAT flux. They found anticorrelation between V-magnitude and Fermi-LAT flux, and correlation between Equivalent Width (EW) and Fermi-LAT flux [12].…”

Section: Introductionmentioning

confidence: 99%

“…Zamanov et al (2014) studied the correlation between Hα line-profile parameters, V-magnitude, and Fermi-LAT flux. They found anticorrelation between V-magnitude and Fermi-LAT flux, and correlation between Equivalent Width (EW) and Fermi-LAT flux [12]. Line-profile variability in Hα indicates perturbations in the Be disk within one orbit, and a bright, high-speed (300-443 km s −1 ) component in the red side of the double-peaked profile before the apastron [13].…”

Section: Introductionmentioning

confidence: 99%

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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Connection between orbital modulation of Hαand gamma-rays in the Be/X-ray binary LS I+61°303

Cited by 8 publications

References 36 publications

Evidence of coupling between the thermal and nonthermal emission in the gamma-ray binary LS I +61 303

Evidence of coupling between the thermal and nonthermal emission in the gamma-ray binary LS I +61 303

Superorbital Modulation at GeV Energies in the γ-Ray Binary LS I + 61°303

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

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