Browsing by Author "Guillot, S."

Now showing 1 - 7 of 7
  • Thumbnail Image
    Item
    Hubble Space Telescope Detection of the Millisecond Pulsar J2124-3358 and its Far-ultraviolet Bow Shock Nebula
    (2017) Reisenegger, Andreas; Rangelov, B.; Pavlov, G. G.; Kargaltsev, O.; Guillot, S.; Van Kerkwijk, M. H.
  • Thumbnail Image
    Item
    Hubble Space Telescope Nondetection of PSR J2144-3933 : The Coldest Known Neutron Star
    (2019) Guillot, S.; Pavlov, G.G.; Reyes, C.; Reisenegger, Andreas; Rodríguez Pemjean, Luis Enrique; Rangelov, B.; Kargaltsev, O.
  • Thumbnail Image
    Item
    Neutron star radius measurement from the ultraviolet and soft X-ray thermal emission of PSR J0437-4715
    (2019) González Caniulef, Denis; Guillot, S.; Reisenegger, Andreas
  • Thumbnail Image
    Item
    New Constraints on the Nuclear Equation of State from the Thermal Emission of Neutron Stars in Quiescent Low-mass X-Ray Binaries
    (2019) D'Etivaux, N.B.; Guillot, S.; Margueron, J.; Webb, N.; Catelan, Márcio; Reisenegger, Andreas
  • Thumbnail Image
    Item
    Old but Still Warm: Far-UV Detection of PSR B0950+08
    (2017) Pavlov, G.; Rangelov, B.; Kargaltsev, O.; Reisenegger, Andreas; Guillot, S.; Reyes, C.
  • No Thumbnail Available
    Item
    Spectral analysis of the quiescent low-mass X-ray binary in the globular cluster M30
    (2020) Echiburú, C. S.; Guillot, S.; Zhao, Y.; Heinke, C. O.; Ozel, F.; Web, N. A.
    We present a recent Chandra observation of the quiescent low-mass X-ray binary containing a neutron star (NS), located in the globular cluster M30. We fit the thermal emission from the NS to extract its mass and radius. We find no evidence of flux variability between the two observations taken in 2001 and 2017, nor between individual 2017 observations, so we analyse them together to increase the signal-to-noise ratio. We perform simultaneous spectral fits using standard light-element composition atmosphere models (hydrogen or helium), including absorption by the interstellar medium, correction for pile-up of X-ray photons on the detector, and a power law for count excesses at high photon energy. Using a Markov chain Monte Carlo approach, we extract mass and radius credible intervals for both chemical compositions of the atmosphere: $\mbox{$R_{\rm NS}$}=7.94\mbox{{$\scriptstyle ^{ + 0.76}_{- 1.21}$}}$ km and $\mbox{$M_{\rm NS}$}\lt 1.19$ M⊙ assuming pure hydrogen, and $\mbox{$R_{\rm NS}$}=10.50\mbox{{$\scriptstyle ^{ + 2.88}_{- 2.03}$}}$ km and $\mbox{$M_{\rm NS}$}\lt 1.78$ M⊙ for helium, where the uncertainties represent the 90 per cent credible regions. For H, the small radius is difficult to reconcile with most current nuclear physics models (especially for nucleonic equations of state) and with other measurements of NS radii, with recent preferred values generally in the 11–14 km range. Whereas for He, the measured radius is consistent with this range. We discuss possible sources of systematic uncertainty that may result in an underestimation of the radius, identifying the presence of surface temperature inhomogeneities as the most relevant bias. According to this, we conclude that either the atmosphere is composed of He or it is anH atmosphere with a significant contribution of hotspots to the observed radiation.
  • Thumbnail Image
    Item
    The NuSTAR view of the non-thermal emission from PSR J0437-4715
    (OXFORD UNIV PRESS, 2016) Guillot, S.; Kaspi, V. M.; Archibald, R. F.; Bachetti, M.; Flynn, C.; Jankowski, F.; Bailes, M.; Boggs, S.; Christensen, F. E.; Craig, W. W.; Hailey, C. A.; Harrison, F. A.; Stern, D.; Zhang, W. W.
    We present a hard X-ray Nuclear Spectroscopic Telescope Array (NuSTAR) observation of PSR J0437-4715, the nearest millisecond pulsar. The known pulsations at the apparent pulse period similar to 5.76 ms are observed with a significance of 3.7 sigma, at energies up to 20 keV above which the NuSTAR background dominates. We measure a photon index Gamma = 1.50 +/- 0.25 (90 per cent confidence) for the power-law fit to the non-thermal emission. It had been shown that spectral models with two or three thermal components fit the XMM-Newton spectrum of PSR J0437-4715, depending on the slope of the power-law component, and the amount of absorption of soft X-rays. The new constraint on the high-energy emission provided by NuSTAR removes ambiguities regarding the thermal components of the emission below 3 keV. We performed a simultaneous spectral analysis of the XMM-Newton and NuSTAR data to confirm that three thermal components and a power law are required to fit the 0.3-20 keV emission of PSR J0437-4715. Adding a ROSAT-PSPC spectrum further confirmed this result and allowed us to better constrain the temperatures of the three thermal components. A phase-resolved analysis of the NuSTAR data revealed no significant change in the photon index of the high-energy emission. This NuSTAR observation provides further impetus for future observations with the NICER mission (Neutron Star Interior Composition Explorer) whose sensitivity will provide much stricter constraints on the equation of state of nuclear matter by combining model fits to the pulsar's phase-folded light curve with the pulsar's well-defined mass and distance from radio timing observations.