Toward a Mass and Radius Determination of the Nearby Isolated Neutron Star RX J185635–3754

By José A. Pons, F. Walter, J. Lattimer, M. Prakash, R. Neuhaeuser, Penghui An. 2001

183 citations recorded by the source corpus.

We discuss efforts to determine the mass, radius, and surface composition of the nearby compact object RX J185635-3754 from its multiwavelength spectral energy distribution. We compute nonmagnetized model atmospheres and emergent spectra for selected compositions and gravities and discuss efforts to fit existing and new observational data from ROSAT, the Extreme Ultraviolet Explorer, and the Hubble Space Telescope. The spectral energy distribution matches that expected from a heavy-element-dominated atmosphere, but not from a uniform-temperature blackbody. Nonmagnetic light-element atmospheres cannot be simultaneously reconciled with the optical and X-ray data. We extend previous studies, which were limited to one fixed neutron star mass and radius. For uniform-temperature models dominated by heavy elements, the redshift z is constrained to be 0.3 ≲ z ≲ 0.4 and the best-fit mass and radius are M ≈ 0.9 M☉ and R ≈ 6 km (for a 61 pc distance). These values for M and R together are not permitted for any plausible equation of state, including that of a self-bound strange quark star. A simplified two-temperature model allows masses and radii up to about 50% larger, or a factor of 2 in the case of a blackbody. The observed luminosity is consistent with the thermal emission of an isolated neutron star no older than about 106 yr, the age inferred from available proper motion and parallax information.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/47fb21fb6a94988a979c8e0da717e540f91149f9

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Citations in the corpus

A COMPACT DEGENERATE PRIMARY-STAR PROGENITOR OF SN 2011fe (2011, background): “We also depict isolated neutron star RX J185635−3754 (M ≈M ), which has strong observed constraints on temperature and density (Pons et al. 2002).”
THE EQUATION OF STATE FROM OBSERVED MASSES AND RADII OF NEUTRON STARS (2010, methodology): “The spectra of isolated cooling neutron stars with well-determined distances, such as RX J1856–3754 discovered by Walter et al. (1996), have a much larger signal-to-noise than those of neutron star transients.”
Minimal Cooling of Neutron Stars: A New Paradigm (2004, methodology): “We take the blackbody spectral fitting from Drake et al. (2002) and Burwitz et al. (2003) for the warm component and fits for the colder component from Pons et al. (2002).”
A class of relativistic stars with a linear equation of state (2007, unknown): “4-3658, RX J185635-3754, 4U 1820-30, 4U 1728-34, PSR 0943+10, strongly favour the possibility that they could actually be strange stars (Bombaci 1997; Li et al 1995, 1999a,b; Dey et al 1998; Xu et al 1999, 2001; Pons et al 2002).”
A Hydrogen Atmosphere Spectral Model Applied to the Neutron Star X7 in the Globular Cluster 47 Tucanae (2005, background): “It is possible thatis error in assumptions may affect the results of Pons et al. (2002) and Walter & Lattimer (2002) as well.”
Magnetic field dissipation in neutron star crusts: From magnetars to isolated neutron stars (2007, background): “…as old as about 1 Myr is also necessary to create the non–uniform surface temperature distribution observed e.g. in the " Magnificent Seven " (see Pons et al. 2002, Schwope et al. 2005; Haberl et al. 2006 for the observational evidence and Geppert et al. 2004, 2006; Pérez–Azorín et al. 2006a,…”
MEASUREMENT OF THE RADIUS OF NEUTRON STARS WITH HIGH SIGNAL-TO-NOISE QUIESCENT LOW-MASS X-RAY BINARIES IN GLOBULAR CLUSTERS (2012, methodology): “Finally, the multiwavelength spectral energy distribution of the isolated neutron star RX J185635-3754 was analyzed to produce small values of RNS and MNS with no plausible dEoS consistent with these values: RNS ∼ 6 km and MNS ∼ 0.9M⊙ for d = 61 pc (Pons et al. 2002).”
Physics of strongly magnetized neutron stars (2006, methodology): “Further works used improved opacity and equation of state data from the OPAL project for pure hydrogen, helium and iron compositions (Rajagopal and Romani 1996, Zavlin et al 1996, Gänsicke et al 2002, Pons et al 2002).”
The Thermal radiation of the isolated neutron star RX J1856.5-3754 observed with Chandra and XMM-Newton (2002, methodology): “Pavlov et al. (1996) and Pons et al. (2002) showed that the light element (hydrogen and helium) nonmagnetic NS atmosphere models can be firmly ruled out because they, applied to the X-ray data on RXJ1856, yield (i) too small distance estimates (d < 10 pc) and (ii) overpredict the optical flux…”
2D Cooling of Magnetized Neutron Stars (2007, unknown): “5−3754 (Pons et al. 2002; Trümper et al. 2004), RBS 1223 (Schwope et al. 2005, 2007), and RX J0720.”