Thermonuclear (Type I) X-Ray Bursts Observed by the Rossi X-Ray Timing Explorer

By D. Galloway, M. Muno, J. Hartman, Dimitrios Psaltis, D. Chakrabarty. 2006

543 citations recorded by the source corpus.

We have assembled a sample of 1187 thermonuclear (type I) X-ray bursts from observations of 48 accreting neutron stars by the Rossi X-ray Timing Explorer, spanning more than 10 years. The sample contains examples of two of the three theoretical ignition regimes (confirmed via comparisons with numerical models) and likely examples of the third. We present a detailed analysis of the variation of the burst profiles, energetics, recurrence times, presence of photospheric radius expansion, and presence of burst oscillations, as a function of accretion rate. We estimated the distance for 35 sources exhibiting radius-expansion bursts, and found that the peak flux of such bursts varies typically by 13%. We classified sources into two main groups based on the burst properties: (1) both long and short bursts (indicating mixed H/He accretion), and (2) consistently short bursts (primarily He accretion), and we calculated the mean burst rate as a function of accretion rate for the two groups. The decrease in burst rate observed at > 0.06ṀEdd (≳2 × 1037 ergs s−1) is associated with a transition in the persistent spectral state and (as has been suggested previously) may be related to the increasing role of steady He burning. We found many examples of bursts with recurrence times <30 minutes, including burst triplets and even quadruplets. We describe the oscillation amplitudes for 13 of the 16 burst oscillation sources, as well as the stages and properties of the bursts in which the oscillations are detected. The burst properties are correlated with the burst oscillation frequency; sources spinning at <400 Hz generally have consistently short bursts, while the more rapidly spinning systems have both long and short bursts. This correlation suggests either that shear-mediated mixing dominates the burst properties, or alternatively that the nature of the mass donor (and hence the evolutionary history) has an influence on the long-term spin evolution.

Subfields: Astronomy and Astrophysics, Biomedical Engineering

View Paper: https://www.semanticscholar.org/paper/3dfb71e24bedd693303d59a1e30fe15a734db308

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In Astronomy and Astrophysics

1. J. Lattimer
2. A. Steiner
3. S. Guillot
4. F. Özel
5. T. Güver
6. C. Heinke
7. E. Brown
8. J. Fuller

In Biomedical Engineering

1. F. Özel
2. T. Güver
3. A. Watts
4. M. Miller
5. J. Lattimer
6. Jonathan M. Miller
7. N. Langer
8. Dimitrios Psaltis

Citations in the corpus

• Constraining the mass and radius of neutron stars in globular clusters (2017, background): “…spallate nuclei on impact, releasing protons(Bildsten et al. 1993), though spallation might require infalling protons (in’t Zand et al. 2005), and there is no evidence of spallation-produced H in observed thermonuclear bursts in extremely short-period LMXBs (Cumming 2003; Galloway et al. 2008).”
• THE EQUATION OF STATE FROM OBSERVED MASSES AND RADII OF NEUTRON STARS (2010, background): “Hydrogen mass fraction:Galloway et al. (2008) noted that EXO 1745–248 has exhibitedlong Type I bursts with estimated values of ∫ dt Fpersistent/ ∫ dt Fburst ≈ GM/R/Enuc ≈ 20–46.”
• Neutron star mass and radius measurements from atmospheric model fits to X-ray burst cooling tail spectra (2017, methodology): “There have been detections of burst oscillations from 4U 1702−429 that imply a non-uniform surface temperature (Markwardt et al. 1999; Galloway et al. 2008; Ootes et al. 2017).”
• MODULES FOR EXPERIMENTS IN STELLAR ASTROPHYSICS (MESA): BINARIES, PULSATIONS, AND EXPLOSIONS (2015, methodology): “Time resolved spectra were binned during the bursts’ rise time and decay (Galloway et al. 2008; Zamfir et al. 2012).”
• The Masses and Spins of Neutron Stars and Stellar-Mass Black Holes (2014, background): “The observation of nearly coherent millisecond oscillations in thermonuclear X-ray bursts [122] was taken by most researchers to show that the stars hosting those bursts, which are in LMXBs, are the progenitors of the non-accreting millisecond pulsars.”
• THE MASS AND RADIUS OF THE NEUTRON STAR IN 4U 1820−30 (2010, methodology): “Five type-I X-ray bursts, all showing evidence of photospheric radius expansion, have been reported from an analysis of Rossi X-ray Timing Explorer data (Galloway et al. 2008).”
• Thermonuclear Burst Oscillations (2012, background): “This occurs most often, but not exclusively, during periods of photospheric radius expansion (Galloway et al. 2008) and is seen in both pulsars and nonpulsars.”
• THE DENSE MATTER EQUATION OF STATE FROM NEUTRON STAR RADIUS AND MASS MEASUREMENTS (2015, methodology): “All of these improvements in the analysis methods lead 2 This is the same argument used in Galloway et al. (2008b) to reject bursts from high inclination sources.”
• THE DISTANCE, MASS, AND RADIUS OF THE NEUTRON STAR IN 4U 1608−52 (2008, methodology): “We used the PRE burst sample shown in Table 3 to measure the touchdown fluxes.”
• THE MASS AND RADIUS OF THE NEUTRON STAR IN EXO 1745−248 (2008, methodology): “EXO 1745−248 was observed with RXTE for 148 ks, during which two Type-I X-ray bursts were discovered, with clear evidence for photospheric radius expansion (Galloway et al. 2008a).”