Urca nuclide production in Type-I X-ray bursts and implications for nuclear physics studies

ABSTRACT The thermal structure of accreting neutron stars is affected by the presence of urca nuclei in the neutron star crust. Nuclear isobars harbouring urca nuclides can be produced in the ashes of Type I X-ray bursts, but the details of their production have not yet been explored. Using the code MESA, we investigate urca nuclide production in a one-dimensional model of Type I X-ray bursts using astrophysical conditions thought to resemble the source GS 1826-24. We find that high-mass (A ≥ 55) urca nuclei are primarily produced late in the X-ray burst, during hydrogen-burning freeze-out that corresponds to the tail of the burst light curve. The ∼0.4–0.6 GK temperature relevant for the nucleosynthesis of these urca nuclides is much lower than the ∼1 GK temperature most relevant for X-ray burst light curve impacts by nuclear reaction rates involving high-mass nuclides. The latter temperature is often assumed for nuclear physics studies. Therefore, our findings alter the excitation energy range of interest in compound nuclei for nuclear physics studies of urca nuclide production. We demonstrate that for some cases this will need to be considered in planning for nuclear physics experiments. Additionally, we show that the lower temperature range for urca nuclide production explains why variations of some nuclear reaction rates in model calculations impacts the burst light curve but not local features of the burst ashes.

Download Full-text

The Nuclear Reaction Waiting Points: 22 Mg, 26 Si, 30 S, and 34 Ar and Bolometrically Double-peaked Type I X-Ray Bursts

The Astrophysical Journal ◽

10.1086/422215 ◽

2004 ◽

Vol 608 (1) ◽

pp. L61-L64 ◽

Cited By ~ 78

Author(s):

Jacob Lund Fisker ◽

Friedrich-Karl Thielemann ◽

Michael Wiescher

Keyword(s):

Nuclear Reaction ◽

Type I ◽

X Ray

Download Full-text

New Reaction Rates Of 64Ge(p,γ)65As(p,γ)66Se And The Impact On Type I X-ray Bursts

10.22323/1.281.0144 ◽

2017 ◽

Author(s):

Yi Hua Lam ◽

Jianjun He ◽

Hendrik Schatz ◽

B. Alex Brown ◽

Anuj Parikh

Keyword(s):

Reaction Rates ◽

Type I ◽

X Ray ◽

The Impact

Download Full-text

Phase connected X-ray light curve and He II radial velocity measurements of NGC 300 X-1

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318007615 ◽

2018 ◽

Vol 14 (S346) ◽

pp. 187-192

Author(s):

S. Carpano ◽

F. Haberl ◽

P. Crowther ◽

A. Pollock

Keyword(s):

Black Hole ◽

Light Curve ◽

Radial Velocity ◽

Orbital Period ◽

High Mass ◽

Velocity Measurements ◽

X Ray ◽

Black Hole Radiation ◽

Ic 10 ◽

Binary Evolution

Abstract. NGC 300 X-1 and IC 10 X-1 are currently the only two robust extragalactic candidates for being Wolf-Rayet/black hole X-ray binaries, the Galactic analogue being Cyg X-3. These systems are believed to be a late product of high-mass X-ray binary evolution and direct progenitors of black hole mergers. From the analysis of Swift data, the orbital period of NGC 300 X-1 was found to be 32.8 h. We here merge the full set of existing data of NGC 300 X-1, using XMM-Newton, Chandra and Swift observations to derive a more precise value of the orbital period of 32.7932 ± 0.0029 h above a confidence level of 99.99%. This allows us to phase connect the X-ray light curve of the source with radial velocity measurements of He II lines performed in 2010. We show that, as for IC 10 X-1 and Cyg X-3, the X-ray eclipse corresponds to maximum of the blueshift of the He II lines, instead of the expected zero velocity. This indicates that for NGC 300 X-1 as well, the wind of the WR star is completely ionised by the black hole radiation and that the emission lines come from the region of the WR star that is in the shadow. We also present for the first time the light curve of two recent very long XMM-Newton observations of the source, performed on the 16th to 20th of December 2016.

Download Full-text

Thermonuclear Reaction Rates for Reactions Leading to N = 28 Nuclei

Australian Journal of Physics ◽

10.1071/ph950125 ◽

1995 ◽

Vol 48 (1) ◽

pp. 125

Author(s):

A.J Morton ◽

DG Sargood

Keyword(s):

Statistical Model ◽

Nuclear Reaction ◽

Cross Sections ◽

Optical Model ◽

Reaction Rates ◽

Reaction Cross ◽

Model Parameters ◽

Thermonuclear Reaction ◽

Model Calculations ◽

Reaction Cross Sections

Nuclear reaction cross sections derived from statistical-model calculations have been used in the calculation of thermonuclear reaction rates for 36 nuclei at temperatures that are representative of the interiors of evolving stars and supernovae as nucleosynthesis approaches the production of nuclei with N = 28. The statistical-model calculations used optical-model parameters in the particle channels which had been selected to give the best overall agreement between theoretical and experimental cross sections for reactions on stable target nuclei in the mass and energy ranges of importance for the stellar conditions of interest. The optical-model parameters used, and the stellar reaction rates obtained, are tabulated. Comparisons are made between these stellar rates and those from other statistical-model calculations in the literature.

Download Full-text

A systematic study of proton capture reactions in the Se-Sn region relevant to p-process nucleosynthesis

HNPS Proceedings ◽

10.12681/hnps.2210 ◽

2019 ◽

Vol 11 ◽

Author(s):

S. Harissopulos ◽

P. Demetriou ◽

S. Galanopoulos ◽

G. Kriembardis ◽

M. Kokkoris ◽

...

Keyword(s):

Cross Section ◽

Cross Sections ◽

Nuclear Physics ◽

Nuclear Reactions ◽

Reaction Network ◽

Reaction Rates ◽

Compton Suppression ◽

Experimental Information ◽

Systematic Investigation ◽

Model Calculations

The synthesis of the so-called ρ nuclei, i.e. a certain class of proton rich nuclei that are heavier than iron, requires a special mechanism known as ρ process. This process consists of various nucleosynthetic scenaria. In some of them proton and alpha-capture reactions are strongly involved, p-process nucleosynthesis is assumed to occur in the Oxygen/Neon rich layers of type II supernovae during their explosion, ρ nuclei are typically 10-100 times less abundant than the corresponding more neutron-rich isotopes. The prediction of their abundances is one of the major puzzles of all models of p-process nucleosynthesis. Until now all these models are capable of reproducing these abundances within a factor of 3. However, they all fail in the case of the light ρ nuclei with A<100. The observed discrepancies could be attributed to uncertainties in the pure "astrophysical" part of the p-process modelling. However, they could also be the result of uncertainties in the nuclear physics data entering the corresponding abundance calculations. In order to perform these calculations the cross sections of typically 10000 nuclear reactions of an extended reaction network involving almost 1000 nuclei from A=12 to 210 are used as input data. Such a huge amount of experimental cross section data are not available. Hence, all extended network calculations rely almost completely on cross sections predicted by the Hauser-Feshbach (HF) theory. It is therefore of paramount importance, on top of any astrophysical model improvements, to test also the reliability of the HF calculations, i.e. to investigate the uncertainties associated with the evaluation of the nuclear properties, like nuclear level densities and nucleon-nucleus potentials, entering the calculations. Until now, this check has been hindered significantly by the fact that in the Se-Sn region there has been scarce experimental information on cross sections at astrophysically relevant energies. In the present work, a systematic investigation of (p,7) cross sections of nuclei from Se to Sb is presented for the first time. The in-beam cross section measurements reported were carried out at energies relevant to p-process nucleosynthesis, i.e. from 1.4 to 5 MeV. The experiments were performed by using either an array of 4 HPGe detectors of 100% relative efficiency shielded with BGO crustals for Compton suppression, or a 4π Nal summing detector. The resulting cross sections, astrophysical S-factors and reaction rates of more than 10 nuclear reactions are compared with the predictions of various statistical model calculations.

Download Full-text

Effects of Rare Isotope Reaction Rates on the Light Curve of an X-ray Burst

New Physics Sae Mulli ◽

10.3938/npsm.66.1524 ◽

2016 ◽

Vol 66 (12) ◽

pp. 1524-1529

Author(s):

Byeongchan PARK* ◽

Kyujin KWAK† ◽

Kyung Yuk CHAE ◽

Aram KIM

Keyword(s):

Light Curve ◽

Reaction Rates ◽

Rare Isotope ◽

X Ray

Download Full-text

An approach to constrain models of accreting neutron stars with the use of an equation of state

Progress of Theoretical and Experimental Physics ◽

10.1093/ptep/ptaa010 ◽

2020 ◽

Vol 2020 (3) ◽

Author(s):

Akira Dohi ◽

Masa-aki Hashimoto ◽

Rio Yamada ◽

Yasuhide Matsuo ◽

Masayuki Y Fujimoto

Keyword(s):

Neutron Star ◽

Equation Of State ◽

Light Curve ◽

Nuclear Energy ◽

Evolution Equations ◽

Energy Generation ◽

Reaction Rates ◽

Computational Time ◽

Recurrence Time ◽

X Ray

Abstract We investigate X-ray bursts during the thermal evolution of an accreting neutron star that corresponds to the X-ray burster GS 1826$-$24. Physical quantities of the neutron star are included using an equation of state below and above the nuclear matter density. We adopt an equation of state and construct an approximate network that saves computational time and calculates nuclear energy generation rates accompanying the abundance evolutions. The mass and radius of the neutron star are found by solving the stellar evolution equations from the center to the surface; this involves necessary information such as the nuclear energy generation in accreting layers, heating from the crust, and neutrino emissions inside the stellar core. We reproduce the light curve and recurrence time of the X-ray burst from GS 1826$-$24 within the standard deviation of 1$\sigma$ for the assumed accretion rate, metallicity, and equation of state. It is concluded that the observed recurrence time is consistent with the theoretical model with metallicity of the initial CNO elements $Z_{\rm CNO} = 0.01$. We suggest that the nuclear reaction rates responsible for the $rp$-process should be examined in detail, because the rates may change the shape of the light curve and our conclusion.

Download Full-text

Multi-wavelength variability of the young solar analog ι Horologii

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935703 ◽

2019 ◽

Vol 631 ◽

pp. A45 ◽

Cited By ~ 3

Author(s):

J. Sanz-Forcada ◽

B. Stelzer ◽

M. Coffaro ◽

S. Raetz ◽

J. D. Alvarado-Gómez

Keyword(s):

Light Curve ◽

Thermal Structure ◽

Rotation Period ◽

Activity Cycle ◽

X Rays ◽

X Ray ◽

Multi Wavelength ◽

Activity Cycles ◽

Irregular Behavior

Context. Chromospheric activity cycles are common in late-type stars; however, only a handful of coronal activity cycles have been discovered. ι Hor is the most active and youngest star with known coronal cycles. It is also a young solar analog, and we are likely facing the earliest cycles in the evolution of solar-like stars, at an age (~600 Myr) when life appeared on Earth. Aims. Our aim is to confirm the ~1.6 yr coronal cycle and characterize its stability over time. We use X-ray observations of ι Hor to study the corona of a star representing the solar past through variability, thermal structure, and coronal abundances. Methods. We analyzed multi-wavelength observations of ι Hor using XMM-Newton, TESS, and HST data. We monitored ι Hor throughout almost seven years in X-rays and in two UV bands. The summed RGS and STIS spectra were used for a detailed thermal structure model, and the determination of coronal abundances. We studied rotation and flares in the TESS light curve. Results. We find a stable coronal cycle along four complete periods, more than covered in the Sun. There is no evidence for a second longer X-ray cycle. Coronal abundances are consistent with photospheric values, discarding any effects related to the first ionization potential. From the TESS light curve we derived the first photometric measurement of the rotation period (8.2 d). No flares were detected in the TESS light curve of ι Hor. We estimate the probability of having detected zero flares with TESS to be ~2%. Conclusions. We corroborate the presence of an activity cycle of ~1.6 yr in ι Hor in X-rays, more regular than its Ca II H&K counterpart. A decoupling of the activity between the northern and southern hemispheres of the star might explain the disagreement. The inclination of the system would result in an irregular behavior in the chromospheric indicators. The more extended coronal material would be less sensitive to this effect.

Download Full-text