The Experts below are selected from a list of 15495 Experts worldwide ranked by ideXlab platform
Izumi Hachisu - One of the best experts on this subject based on the ideXlab platform.
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Optical light curves of RS Oph (2006) and Hydrogen Burning turnoff
arXiv: Astrophysics, 2008Co-Authors: Izumi Hachisu, Mariko Kato, Seiichiro Kiyota, Katsuaki Kubotera, Hiroyuki Maehara, Kazuhiro Nakajima, Yuko Ishii, M. Kamada, Sahori Mizoguchi, Shinji NishiyamaAbstract:We report a coordinated multi-band photometry of the RS Oph 2006 outburst and highlight the emission line free y-band photometry that shows a mid-plateau phase at y ~ 10.2 mag from day 40 to day 75 after the discovery followed by a sharp drop of the final decline. Such mid-plateau phases are observed in other two recurrent novae, U Sco and CI Aql, and are interpreted as a bright disk irradiated by the white dwarf. We have calculated theoretical light curves based on the optically thick wind theory and have reproduced the early decline, mid-plateau phase, and final decline. The final decline is identified with the end of steady Hydrogen shell-Burning, which turned out at about day 80. This turnoff date is consistent with the end of a supersoft X-ray phase observed with Swift. Our model suggests a white dwarf mass of 1.35 \pm 0.01 M_\sun, which indicates that RS Oph is a progenitor of Type Ia supernovae. We strongly recommend the y-filter observation of novae to detect both the presence of a disk and the Hydrogen Burning turnoff. Observational data of y magnitudes are provided here together with other multi-wavelength light curve data.
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Thermal Stability of White Dwarfs Accreting Hydrogen-rich Matter and Progenitors of Type Ia Supernovae
The Astrophysical Journal, 2007Co-Authors: Ken'ichi Nomoto, Mariko Kato, Hideyuki Saio, Izumi HachisuAbstract:We revisit the properties of white dwarfs accreting Hydrogen-rich matter, by constructing steady state models in which Hydrogen shell Burning consumes Hydrogen at the same rate as the white dwarf accretes it. We obtain steady models for various accretion rates and white dwarf masses. We confirm that these are thermally stable only when the accretion rate is higher than ~10-7 M☉ yr-1. We show that recent models of quiescent "surface Hydrogen Burning" for a much wider range of accretion rates result from the use of too large a zone mass in the outer part of the models; Hydrogen Burning must occur in a much thinner layer. A comparison of the positions on the H-R diagram suggests that most of the luminous supersoft X-ray sources are white dwarfs accreting matter at rates high enough that the Hydrogen-Burning shell is thermally stable. Implications for the progenitors of Type Ia supernovae are discussed.
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The Hydrogen-Burning turnoff of RS Ophiuchi (2006)
The Astrophysical Journal, 2006Co-Authors: Izumi Hachisu, Mariko Kato, Seiichiro Kiyota, Katsuaki Kubotera, Hiroyuki Maehara, Kazuhiro Nakajima, Yuko Ishii, M. Kamada, Sahori Mizoguchi, Shinji NishiyamaAbstract:We report a coordinated multiband photometry of the RS Oph 2006 outburst and highlight the emission-line-free y-band photometry that shows a midplateau phase at y ~ 10.2 mag from day 40 to day 75 after the discovery, followed by a sharp drop of the final decline. Such midplateau phases are observed in other two recurrent novae, U Sco and CI Aql, and are interpreted as a bright disk irradiated by the white dwarf. We have calculated theoretical light curves based on the optically thick wind theory and have reproduced the observed light curves, including the midplateau phase and the final sharp decline. This final decline is identified with the end of steady Hydrogen shell Burning, which turned out at about day 80. This turnoff date is consistent with the end of a supersoft X-ray phase observed with Swift. Our model suggests a white dwarf mass of 1.35 ± 0.01 M☉, which indicates that RS Oph is a progenitor of Type Ia supernovae. We strongly recommend the y-filter observation of novae to detect both the presence of a disk and the Hydrogen Burning turnoff.
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the Hydrogen Burning turn off of rs ophiuchi 2006
arXiv: Astrophysics, 2006Co-Authors: Izumi Hachisu, Mariko Kato, Seiichiro Kiyota, Katsuaki Kubotera, Hiroyuki Maehara, Kazuhiro Nakajima, Yuko Ishii, M. Kamada, Sahori Mizoguchi, Shinji NishiyamaAbstract:We report a coordinated multi-band photometry of the RS Oph 2006 outburst and highlight the emission line free y-band photometry that shows a mid-plateau phase at y ~ 10.2 mag from day 40 to day 75 after the discovery followed by a sharp drop of the final decline. Such mid-plateau phases are observed in other two recurrent novae, U Sco and CI Aql, and are interpreted as a bright disk irradiated by the white dwarf. We have calculated theoretical light curves based on the optically thick wind theory and have reproduced the observed light curves including the mid-plateau phase and the final sharp decline. This final decline is identified with the end of steady Hydrogen shell-Burning, which turned out the day ~80. This turnoff date is consistent with the end of a supersoft X-ray phase observed with Swift. Our model suggests a white dwarf mass of 1.35 \pm 0.01 M_\sun, which indicates that RS Oph is a progenitor of Type Ia supernovae. We strongly recommend the y-filter observation of novae to detect both the presence of a disk and the Hydrogen Burning turn-off.
Christian G Iliadis - One of the best experts on this subject based on the ideXlab platform.
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Explosive Hydrogen Burning of 23Na in classical novae
Journal of Physics G: Nuclear and Particle Physics, 2005Co-Authors: Christian G Iliadis, Arthur E Champagne, Jordi JoséAbstract:It is frequently assumed that matter in the mass range A ≥ 20 is processed through the NeNa-cycle during Hydrogen-Burning nucleosynthesis. The existence of such a reaction cycle implies that the 23Na(p,α)20Ne reaction is more likely to occur than the competing 23Na(p,γ)24Mg reaction. Recently evaluated thermonuclear rates for both reactions carry large uncertainties and allow for both possibilities, a closed and an open NeNa-cycle. We measured the 23Na(p,γ)24Mg reaction at the Laboratory for Experimental Nuclear Astrophysics (LENA). The present experimental results reduce the 23Na+p reaction rate uncertainties significantly. We demonstrate that a closed NeNa-cycle does not exist at elevated stellar temperatures of T = 0.2–0.4 GK. The implications for the nucleosynthesis in classical novae are discussed.
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Does an NeNa Cycle Exist in Explosive Hydrogen Burning
The Astrophysical Journal, 2004Co-Authors: C. M. Rowland, Christian G Iliadis, Arthur E Champagne, Jordi José, C. Fox, R. C. RunkleAbstract:According to common assumptions, matter in the mass range A ≥ 20 is processed through the so-called NeNa cycle during Hydrogen-Burning nucleosynthesis. The existence of such a reaction cycle implies that the (p, α) reaction on 23Na is more likely to occur than the competing (p, γ) reaction. However, recently evaluated thermonuclear rates for both reactions carry relatively large uncertainties and allow for both possibilities, i.e., a "closed" and an "open" NeNa cycle. We measured the 23Na(p, γ)24Mg reaction at the Laboratory for Experimental Nuclear Astrophysics. The present experimental results, obtained with our sensitive γ-ray detection apparatus, reduce the 23Na + p reaction rate uncertainties significantly. We demonstrate that a closed NeNa cycle does not exist at stellar temperatures of T = 0.2-0.4 GK. The new results have important implications for the nucleosynthesis in classical novae, including the amount of 26Al ejected by the thermonuclear explosion, the elemental abundances of Mg and Al observed in nova shells, and observations of Mg and Al isotopic ratios in primitive meteorites.
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Indirect experimental approaches to reactions important for stellar Hydrogen Burning
AIP Conference Proceedings, 2000Co-Authors: Christian G IliadisAbstract:A large number of proton capture reactions cannot be measured directly at astrophysically important energies with current experimental techniques. Over the past decade, indirect methods have been used extensively for the study of nuclear structure and nuclear reaction mechanisms in order to infer the nuclear cross sections of astrophysical interest. Some of the experimental techniques will be discussed by using as an example a recent study of the 24Mg(p,γ)25Al reaction which is important for Hydrogen Burning in globular cluster red giant stars.
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Decay studies of importance to explosive Hydrogen Burning
Nuclear Physics A, 1997Co-Authors: Christian G Iliadis, R. E. Azuma, J. C. Chow, J.d. King, A. C. Morton, L. Buchmann, Marik Dombsky, K. P. Jackson, John M. D'auria, U. GiesenAbstract:Abstract The β-delayed α-particle decay of 36K has been measured in order to search for natural parity states near the proton threshold in 36Ar. Such states could correspond to resonances in the reaction 35Cl(p,α)32S and might influence mass flows in explosive Hydrogen Burning scenarios appreciably. We have found evidence for a new α-particle emitting state, corresponding to a resonance energy of ERlab=351 keV. Possible implications for the nucleosynthesis during neon nova outbursts are discussed. Properties of the proton drip line nuclei 65As, 69Br and 73Rb are important for the prediction of the nucleosynthesis in very high-temperature Hydrogen-Burning scenarios, such as x-ray bursts. We describe an experimental program at TRIUMF which is designed to measure the quantities of astrophysical interest.
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Reaction rate for 31S(p, gamma )32Cl and its influence on the SiP cycle in hot stellar Hydrogen Burning.
Physical review. C Nuclear physics, 1994Co-Authors: S. Vouzoukas, Christian G Iliadis, U. Giesen, L. O. Lamm, C.p. Browne, J. Görres, S. Graff, H. Herndl, J. Meissner, J. G. RossAbstract:The excitation energies of the proton unbound states in [sup 32]Cl have been measured in the [sup 32]S([sup 3]He,[ital t])[sup 32]Cl charge exchange reaction with high accuracy. The partial widths of the unbound levels have been calculated to derive the resonance strengths of these states in the [sup 31]S([ital p],[gamma])[sup 32]Cl reaction channel. The reaction rate for the [sup 31]S([ital p],[gamma])[sup 32]Cl reaction has been calculated and is compared with previous estimates. The role of this reaction for the closure of the SiP cycle is discussed in terms of the temperature and density conditions in hot stellar Hydrogen Burning.
Lars Bildsten - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen Burning on Accreting White Dwarfs: Stability, Recurrent Novae, and the Post-nova Supersoft Phase
The Astrophysical Journal, 2013Co-Authors: William M. Wolf, Lars Bildsten, J. Brooks, Bill PaxtonAbstract:We examine the properties of white dwarfs (WDs) accreting Hydrogen-rich matter in and near the stable Burning regime of accretion rates as modeled by time-dependent calculations done with Modules for Experiments in Stellar Astrophysics (MESA). We report the stability boundary for WDs of masses between 0.51 M ? and 1.34 M ? as found via time-dependent calculations. We also examine recurrent novae that are accreting at rates close to, but below, the stable Burning limit and report their recurrence times. Our dense grid in accretion rates finds the expected minimum possible recurrence times as a function of the WD mass. This enables inferences to be made about the minimum WD mass possible to reach a specific recurrence time. We compare our computational models of post-outburst novae to the stably Burning WDs and explicitly calculate the duration and effective temperature (T eff) of the post-nova WD in the supersoft phase. We agree with the measured turnoff time-T eff relation in M31 by Henze and collaborators, infer WD masses in the 1.0-1.3 M ? range, and predict ejection masses consistent with those observed. We close by commenting on the importance of the hot helium layer generated by stable or unstable Hydrogen Burning for the short- and long-term evolution of accreting WDs.
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Hydrogen Burning on accreting white dwarfs stability recurrent novae and the post novae supersoft source
arXiv: Solar and Stellar Astrophysics, 2013Co-Authors: William M. Wolf, Lars Bildsten, J. Brooks, Bill PaxtonAbstract:We examine the properties of white dwarfs (WDs) accreting Hydrogen-rich matter in and near the stable Burning regime of accretion rates as modeled by time-dependent calculations done with Modules for Experiments in Stellar Astrophysics (MESA). We report the stability boundary for WDs of masses between 0.51 solar masses and 1.34 solar masses as found via time-dependent calculations. We also examine recurrent novae that are accreting at rates close to, but below, the stable Burning limit and report their recurrence times and ignition masses. Our dense grid in accretion rates finds the expected minimum possible recurrence times as a function of the WD mass. This enables inferences to be made about the minimum WD mass possible to reach a specific recurrence time. We compare our computational models of post-outburst novae to the stably Burning WDs and explicitly calculate the duration and effective temperature (Teff) of the post-novae WD in the supersoft phase. We agree with the measured turnoff time - Teff relation in M31 by Henze and collaborators, infer WD masses in the 1.0-1.3 solar masses range, and predict ejection masses consistent with those observed. We close by commenting on the importance of the hot helium layer generated by stable or unstable Hydrogen Burning for the short- and long-term evolution of accreting white dwarfs.
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Pulsations in Hydrogen Burning Low Mass Helium White Dwarfs
The Astrophysical Journal, 2010Co-Authors: Justin D. R. Steinfadt, Lars Bildsten, Phil ArrasAbstract:Helium core white dwarfs (WDs) with mass M {approx}< 0.20 M {sub sun} undergo several Gyr of stable Hydrogen Burning as they evolve. We show that in a certain range of WD and Hydrogen envelope masses, these WDs may exhibit g-mode pulsations similar to their passively cooling, more massive carbon/oxygen core counterparts, the ZZ Cetis. Our models with stably Burning Hydrogen envelopes on helium cores yield g-mode periods and period spacings longer than the canonical ZZ Cetis by nearly a factor of 2. We show that core composition and structure can be probed using seismology since the g-mode eigenfunctions predominantly reside in the helium core. Though we have not carried out a fully nonadiabatic stability analysis, the scaling of the thermal time in the convective zone with surface gravity highlights several low-mass helium WDs that should be observed in search of pulsations: NLTT 11748, SDSS J0822+2753, and the companion to PSR J1012+5307. Seismological studies of these He core WDs may prove especially fruitful, as their luminosity is related (via stable Hydrogen Burning) to the Hydrogen envelope mass, which eliminates one model parameter.
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Hydrogen Burning on Magnetar Surfaces
The Astrophysical Journal, 2004Co-Authors: Philip Chang, Phil Arras, Lars BildstenAbstract:We compute the rate of diffusive nuclear Burning for Hydrogen on the surface of a "magnetar" (soft gamma-ray repeater [SGR] or anomalous X-ray pulsar [AXP]). We find that Hydrogen at the photosphere will be burned on an extremely rapid timescale of hours to years, depending on the composition of the underlying material. Improving on our previous studies, we explore the effect of a maximally thick "inert" helium layer, previously thought to slow down the Burning rate. Since Hydrogen diffuses faster in helium than through heavier elements, we find this helium buffer actually increases the Burning rate for magnetars. We compute simple analytic scalings of the Burning rate with temperature and magnetic field for a range of core temperatures. We conclude that magnetar photospheres are very unlikely to contain Hydrogen. This motivates theoretical work on heavy element atmospheres that are needed to measure the effective temperature from the observed thermal emission and constrains models of AXPs that rely on magnetar cooling through thick light element envelopes.
Mariko Kato - One of the best experts on this subject based on the ideXlab platform.
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Optical light curves of RS Oph (2006) and Hydrogen Burning turnoff
arXiv: Astrophysics, 2008Co-Authors: Izumi Hachisu, Mariko Kato, Seiichiro Kiyota, Katsuaki Kubotera, Hiroyuki Maehara, Kazuhiro Nakajima, Yuko Ishii, M. Kamada, Sahori Mizoguchi, Shinji NishiyamaAbstract:We report a coordinated multi-band photometry of the RS Oph 2006 outburst and highlight the emission line free y-band photometry that shows a mid-plateau phase at y ~ 10.2 mag from day 40 to day 75 after the discovery followed by a sharp drop of the final decline. Such mid-plateau phases are observed in other two recurrent novae, U Sco and CI Aql, and are interpreted as a bright disk irradiated by the white dwarf. We have calculated theoretical light curves based on the optically thick wind theory and have reproduced the early decline, mid-plateau phase, and final decline. The final decline is identified with the end of steady Hydrogen shell-Burning, which turned out at about day 80. This turnoff date is consistent with the end of a supersoft X-ray phase observed with Swift. Our model suggests a white dwarf mass of 1.35 \pm 0.01 M_\sun, which indicates that RS Oph is a progenitor of Type Ia supernovae. We strongly recommend the y-filter observation of novae to detect both the presence of a disk and the Hydrogen Burning turnoff. Observational data of y magnitudes are provided here together with other multi-wavelength light curve data.
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Thermal Stability of White Dwarfs Accreting Hydrogen-rich Matter and Progenitors of Type Ia Supernovae
The Astrophysical Journal, 2007Co-Authors: Ken'ichi Nomoto, Mariko Kato, Hideyuki Saio, Izumi HachisuAbstract:We revisit the properties of white dwarfs accreting Hydrogen-rich matter, by constructing steady state models in which Hydrogen shell Burning consumes Hydrogen at the same rate as the white dwarf accretes it. We obtain steady models for various accretion rates and white dwarf masses. We confirm that these are thermally stable only when the accretion rate is higher than ~10-7 M☉ yr-1. We show that recent models of quiescent "surface Hydrogen Burning" for a much wider range of accretion rates result from the use of too large a zone mass in the outer part of the models; Hydrogen Burning must occur in a much thinner layer. A comparison of the positions on the H-R diagram suggests that most of the luminous supersoft X-ray sources are white dwarfs accreting matter at rates high enough that the Hydrogen-Burning shell is thermally stable. Implications for the progenitors of Type Ia supernovae are discussed.
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The Hydrogen-Burning turnoff of RS Ophiuchi (2006)
The Astrophysical Journal, 2006Co-Authors: Izumi Hachisu, Mariko Kato, Seiichiro Kiyota, Katsuaki Kubotera, Hiroyuki Maehara, Kazuhiro Nakajima, Yuko Ishii, M. Kamada, Sahori Mizoguchi, Shinji NishiyamaAbstract:We report a coordinated multiband photometry of the RS Oph 2006 outburst and highlight the emission-line-free y-band photometry that shows a midplateau phase at y ~ 10.2 mag from day 40 to day 75 after the discovery, followed by a sharp drop of the final decline. Such midplateau phases are observed in other two recurrent novae, U Sco and CI Aql, and are interpreted as a bright disk irradiated by the white dwarf. We have calculated theoretical light curves based on the optically thick wind theory and have reproduced the observed light curves, including the midplateau phase and the final sharp decline. This final decline is identified with the end of steady Hydrogen shell Burning, which turned out at about day 80. This turnoff date is consistent with the end of a supersoft X-ray phase observed with Swift. Our model suggests a white dwarf mass of 1.35 ± 0.01 M☉, which indicates that RS Oph is a progenitor of Type Ia supernovae. We strongly recommend the y-filter observation of novae to detect both the presence of a disk and the Hydrogen Burning turnoff.
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the Hydrogen Burning turn off of rs ophiuchi 2006
arXiv: Astrophysics, 2006Co-Authors: Izumi Hachisu, Mariko Kato, Seiichiro Kiyota, Katsuaki Kubotera, Hiroyuki Maehara, Kazuhiro Nakajima, Yuko Ishii, M. Kamada, Sahori Mizoguchi, Shinji NishiyamaAbstract:We report a coordinated multi-band photometry of the RS Oph 2006 outburst and highlight the emission line free y-band photometry that shows a mid-plateau phase at y ~ 10.2 mag from day 40 to day 75 after the discovery followed by a sharp drop of the final decline. Such mid-plateau phases are observed in other two recurrent novae, U Sco and CI Aql, and are interpreted as a bright disk irradiated by the white dwarf. We have calculated theoretical light curves based on the optically thick wind theory and have reproduced the observed light curves including the mid-plateau phase and the final sharp decline. This final decline is identified with the end of steady Hydrogen shell-Burning, which turned out the day ~80. This turnoff date is consistent with the end of a supersoft X-ray phase observed with Swift. Our model suggests a white dwarf mass of 1.35 \pm 0.01 M_\sun, which indicates that RS Oph is a progenitor of Type Ia supernovae. We strongly recommend the y-filter observation of novae to detect both the presence of a disk and the Hydrogen Burning turn-off.
Bill Paxton - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen Burning on Accreting White Dwarfs: Stability, Recurrent Novae, and the Post-nova Supersoft Phase
The Astrophysical Journal, 2013Co-Authors: William M. Wolf, Lars Bildsten, J. Brooks, Bill PaxtonAbstract:We examine the properties of white dwarfs (WDs) accreting Hydrogen-rich matter in and near the stable Burning regime of accretion rates as modeled by time-dependent calculations done with Modules for Experiments in Stellar Astrophysics (MESA). We report the stability boundary for WDs of masses between 0.51 M ? and 1.34 M ? as found via time-dependent calculations. We also examine recurrent novae that are accreting at rates close to, but below, the stable Burning limit and report their recurrence times. Our dense grid in accretion rates finds the expected minimum possible recurrence times as a function of the WD mass. This enables inferences to be made about the minimum WD mass possible to reach a specific recurrence time. We compare our computational models of post-outburst novae to the stably Burning WDs and explicitly calculate the duration and effective temperature (T eff) of the post-nova WD in the supersoft phase. We agree with the measured turnoff time-T eff relation in M31 by Henze and collaborators, infer WD masses in the 1.0-1.3 M ? range, and predict ejection masses consistent with those observed. We close by commenting on the importance of the hot helium layer generated by stable or unstable Hydrogen Burning for the short- and long-term evolution of accreting WDs.
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Hydrogen Burning on accreting white dwarfs stability recurrent novae and the post novae supersoft source
arXiv: Solar and Stellar Astrophysics, 2013Co-Authors: William M. Wolf, Lars Bildsten, J. Brooks, Bill PaxtonAbstract:We examine the properties of white dwarfs (WDs) accreting Hydrogen-rich matter in and near the stable Burning regime of accretion rates as modeled by time-dependent calculations done with Modules for Experiments in Stellar Astrophysics (MESA). We report the stability boundary for WDs of masses between 0.51 solar masses and 1.34 solar masses as found via time-dependent calculations. We also examine recurrent novae that are accreting at rates close to, but below, the stable Burning limit and report their recurrence times and ignition masses. Our dense grid in accretion rates finds the expected minimum possible recurrence times as a function of the WD mass. This enables inferences to be made about the minimum WD mass possible to reach a specific recurrence time. We compare our computational models of post-outburst novae to the stably Burning WDs and explicitly calculate the duration and effective temperature (Teff) of the post-novae WD in the supersoft phase. We agree with the measured turnoff time - Teff relation in M31 by Henze and collaborators, infer WD masses in the 1.0-1.3 solar masses range, and predict ejection masses consistent with those observed. We close by commenting on the importance of the hot helium layer generated by stable or unstable Hydrogen Burning for the short- and long-term evolution of accreting white dwarfs.
