To access the full text documents, please follow this link: http://hdl.handle.net/2445/44243

On the binary nature of the γ-ray sources AGL J2241+4454 (= MWC 656) and HESS J0632+057 (= MWC 148)
Casares, J.; Ribó Gomis, Marc; Ribas Canudas, Ignasi; Paredes i Poy, Josep Maria; Vilardell, F.; Negueruela, I.
Universitat de Barcelona
We present optical spectroscopy of MWC 656 and MWC 148, the proposed optical counterparts of the gamma-ray sources AGL J2241+4454 and HESS J0632+0 57, respectively. The main parameters of the Halpha emission line (EW, FWHM and centroid velocity) in these stars are modulated on the proposed orbital periods of 60.37 and 321 days, respectively. These modulations are likely produced by the resonant interaction of the Be discs with compact stars in eccentric orbits. We also present radial velocity curves of the optical stars folded on the above periods and obtain the first orbital elements of the two gamma-ray sources thus confirming their binary nature. Our orbital solution support eccentricities e~0.4 and 0.83+-0.08 for MWC 656 and MWC 148, respectively. Further, our orbital elements imply that the X-ray outbursts in HESS J0632+057/MWC 148 are delayed ~0.3 orbital phases after periastron passage, similarly to the case of LS I +61 303. In addition, the optical photometric light curve maxima in AGL J2241+4454/MWC 656 occur ~0.25 phases passed periastron, similar to what is seen in LS I +61 303. We also find that the orbital eccentricity is correlated with orbital period for the known gamma-ray binaries. This is explained by the fact that small stellar separations are required for the efficient triggering of VHE radiation. Another correlation between the EW of Halpha and orbital period is also observed, similarly to the case of Be/X-ray binaries. These correlations are useful to provide estimates of the key orbital parameters Porb and e from the Halpha line in future Be gamma-ray binary candidates.
Astrofísica
Estels
Raigs gamma
Raigs X
Espectroscòpia
Astrophysics
Stars
Gamma rays
X-rays
Spectrum analysis
(c) Casares, J. et al., 2012
Article
info:eu-repo/semantics/publishedVersion
Royal Astronomical Society
         

Show full item record

Related documents

Other documents of the same author

Casares, J.; Negueruela, I.; Ribó Gomis, Marc; Ribas Canudas, Ignasi; Paredes i Poy, Josep Maria; Herrero, A.; Simón-Díaz, S.
Bosch i Ramon, Valentí; Motch, C.; Ribó Gomis, Marc; Lopes de Oliveira, R.; Janot-Pacheco, E.; Negueruela, I.; Paredes i Poy, Josep Maria; Martocchia, A.
Martí Ribas, Josep; Paredes i Poy, Josep Maria; Bloom, J. S.; Casares, J.; Ribó Gomis, Marc; Falco, E. E.
Ribó Gomis, Marc; Ros, Eduardo; Paredes i Poy, Josep Maria; Massi, M.; Martí Ribas, Josep
Massi, M.; Ribó Gomis, Marc; Paredes i Poy, Josep Maria; Garrington, S. T.; Peracaula i Bosch, Marta; Martí Ribas, Josep
 

Coordination

 

Supporters