Is RX J1856.5–3754 a Quark Star?

By J. Drake, H. Marshall, S. Dreizler, P. Freeman, A. Fruscione, M. Juda, V. Kashyap, F. Nicastro, D. Pease, B. Wargelin and 1 more. 2002

174 citations recorded by the source corpus.

Deep Chandra Low Energy Transmission Grating and High Resolution Camera spectroscopic observations of the isolated neutron star candidate RX J1856.5-3754 have been analyzed to search for metallic and resonance cyclotron spectral features and for pulsation behavior. As found from earlier observations, the X-ray spectrum is well represented by an ~60 eV (7 × 105 K) blackbody. No unequivocal evidence of spectral line or edge features has been found, arguing against metal-dominated models. The data contain no evidence for pulsation, and we place a 99% confidence upper limit of 2.7% on the unaccelerated pulse fraction over a wide frequency range from 10-4 to 100 Hz. We argue that the derived interstellar medium neutral hydrogen column density of 8 × 1019 cm-2 ≤ NH ≤ 1.1 × 1020 cm-2 favors the larger distance from two recent Hubble Space Telescope parallax analyses, placing RX J1856.5-3754 at ~140 pc instead of ~60 pc and in the outskirts of the R CrA dark molecular cloud. That such a comparatively rare region of high interstellar matter (ISM) density is precisely where an isolated neutron star reheated by accretion of ISM would be expected is either entirely coincidental or current theoretical arguments excluding this scenario for RX J1856.5-3754 are premature. Taken at face value, the combined observational evidence—a lack of spectral and temporal features and an implied radius of R∞ = 3.8-8.2 km that is too small for current neutron star models—points to a more compact object, such as allowed for quark matter equations of state.

Subfields: Astronomy and Astrophysics, Geophysics

View Paper: https://www.semanticscholar.org/paper/0c3a93b13714b2cbeddd3dae353fe4074c225c6c

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In Astronomy and Astrophysics

1. J. Lattimer
2. A. Steiner
3. A. Harding
4. M. Prakash
5. D. Lai
6. D. Page
7. V. Zavlin
8. Isaac Vidaña

In Geophysics

1. J. Lattimer
2. A. Steiner
3. V. Zavlin
4. G. Pavlov
5. M. Prakash
6. D. Page
7. A. Harding
8. Y. Lim

Citations in the corpus

• Quark Deconfinement and Implications for the Radius and the Limiting Mass of Compact Stars (2004, background): “…proof of the existence of strange stars; however, a sizable amount of observational data collected by the new generation of X-ray satellites is providing a growing body of evidence for their possible existence (Bombaci 1997; Cheng et al. 1998; Li et al. 1999a, 1999b; Xu 2002; Drake et al. 2002).”
• Physics of strongly magnetized neutron stars (2006, background): “5-3754, has a featureless spectrum remarkably well described by a blackbody (Drake et al (2002), Burwitz et al (2003)), absorption lines/features at E 0.2–2 keV have recently been detected from at least four sources, including 1E 1207.4-5209 (0.7 and 1.4 keV, possibly also 2.1, 2.8 keV; Sanwal et…”
• Gamma-Ray Bursts from Delayed Collapse of Neutron Stars to Quark Matter Stars (2002, background): “…but rather different radii should exist: a) pure (metastable) HS, with radii in the range 12–20 km, as is the case of the compact star 1E 1207.4-5209, assuming M = 1.4M⊙ (Sanwal et al. 2002), and b) HyS or QS with radii in the range 6–8 km (Bombaci 1997; Li et al. 1999a,b; Drake et al. 2002).”
• 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).”
• Discovery of Absorption Features in the X-Ray Spectrum of an Isolated Neutron Star (2002, background): “…lines have been found in the spectra of the Vela pulsar (Pavlov et al. 2001), the anomalous X-ray pulsar 4U 0142 61 (Juett et al. 2002), and the nearby radio-quiet NS RX J1865 3754 (Burwitz et al. 2001; Drake et al. 2002), despite sensitive observations with theChandra grating spectrometers.”
• The Thermal radiation of the isolated neutron star RX J1856.5-3754 observed with Chandra and XMM-Newton (2002, methodology): “Details on results from the timing analysis of the Chandra data can be found in B01, Ransom, Gaensler, & Slane (2002) and Drake et al. (2002).”