Polarimetric and spectroscopic optical observations of the ultra-compact X-ray binary 4U 0614+091

M. C. Baglio, D. Mainetti, P. D'Avanzo, S. Campana, S. Covino, Dave Russell, T. Shahbaz

Research output: Contribution to journalArticle

Abstract

Aims. We present a polarimetric and spectroscopic study of the persistent ultra-compact X-ray binary 4U 0614+091 aimed at searching for the emission of a relativistic particle jet and at unveiling the orbital period Porb of the system. Methods. We obtained r-band polarimetric observations with the Telescopio Nazionale Galileo (TNG) equipped with the PAOLO polarimeter and with the Nordic Optical Telescope (NOT) equipped with the ALFOSC instrument, covering ~2 h and ~0.5 h observations, respectively. We carried out low resolution spectroscopy of the system using the ESO Very Large Telescope equipped with FORS1 for ~1.5 h (16 spectra covering the range 4300-8000 Å). Results. The polarimetric analysis performed starting from the TNG dataset revealed a polarisation degree in the r-band of 3% ± 1%. From the NOT dataset, due to the lower signal-to-noise ratio, we could obtain only a 3σ upper limit of 3.4%. From the joining of a spectroscopic and photometric analysis, through the study of the equivalent width variations of the CII 7240 Å line and the r-band light curve, we could find a hint of a ~45 min periodicity. Conclusions. A polarisation degree P of ~3% in the r-band is consistent with the emission of a relativistic particle jet, which is supposed to emit intrinsically linearly polarised synchrotron radiation. Since no variations of P with time have been detected, and the accretion disc of the system does not contain ionised hydrogen, scattering by free electrons in the accretion disc has been rejected. The period of ~45 min obtained through the analysis of the system light curve and of the equivalent width variations of the selected spectral line is probably linked to the presence of a hot spot or a superhump in the accretion disc, and lead to an orbital period ? 1 h for the binary system.

Original languageEnglish (US)
Article numberA99
JournalAstronomy and Astrophysics
Volume572
DOIs
StatePublished - Dec 1 2014

Fingerprint

accretion
accretion disks
relativistic particles
telescopes
polarization
light curve
coverings
x rays
orbitals
signal-to-noise ratio
periodicity
hot spot
spectroscopic analysis
polarimeters
European Southern Observatory
spectroscopy
scattering
hydrogen
free electrons
line spectra

Keywords

  • Polarisation
  • Stars: jets
  • Stars: neutron
  • X-rays: binaries

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Polarimetric and spectroscopic optical observations of the ultra-compact X-ray binary 4U 0614+091. / Baglio, M. C.; Mainetti, D.; D'Avanzo, P.; Campana, S.; Covino, S.; Russell, Dave; Shahbaz, T.

In: Astronomy and Astrophysics, Vol. 572, A99, 01.12.2014.

Research output: Contribution to journalArticle

Baglio, M. C. ; Mainetti, D. ; D'Avanzo, P. ; Campana, S. ; Covino, S. ; Russell, Dave ; Shahbaz, T. / Polarimetric and spectroscopic optical observations of the ultra-compact X-ray binary 4U 0614+091. In: Astronomy and Astrophysics. 2014 ; Vol. 572.
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abstract = "Aims. We present a polarimetric and spectroscopic study of the persistent ultra-compact X-ray binary 4U 0614+091 aimed at searching for the emission of a relativistic particle jet and at unveiling the orbital period Porb of the system. Methods. We obtained r-band polarimetric observations with the Telescopio Nazionale Galileo (TNG) equipped with the PAOLO polarimeter and with the Nordic Optical Telescope (NOT) equipped with the ALFOSC instrument, covering ~2 h and ~0.5 h observations, respectively. We carried out low resolution spectroscopy of the system using the ESO Very Large Telescope equipped with FORS1 for ~1.5 h (16 spectra covering the range 4300-8000 {\AA}). Results. The polarimetric analysis performed starting from the TNG dataset revealed a polarisation degree in the r-band of 3{\%} ± 1{\%}. From the NOT dataset, due to the lower signal-to-noise ratio, we could obtain only a 3σ upper limit of 3.4{\%}. From the joining of a spectroscopic and photometric analysis, through the study of the equivalent width variations of the CII 7240 {\AA} line and the r-band light curve, we could find a hint of a ~45 min periodicity. Conclusions. A polarisation degree P of ~3{\%} in the r-band is consistent with the emission of a relativistic particle jet, which is supposed to emit intrinsically linearly polarised synchrotron radiation. Since no variations of P with time have been detected, and the accretion disc of the system does not contain ionised hydrogen, scattering by free electrons in the accretion disc has been rejected. The period of ~45 min obtained through the analysis of the system light curve and of the equivalent width variations of the selected spectral line is probably linked to the presence of a hot spot or a superhump in the accretion disc, and lead to an orbital period ? 1 h for the binary system.",
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AU - D'Avanzo, P.

AU - Campana, S.

AU - Covino, S.

AU - Russell, Dave

AU - Shahbaz, T.

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KW - Polarisation

KW - Stars: jets

KW - Stars: neutron

KW - X-rays: binaries

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