10 pages, 2 tables.-- En: "Supernovae: lights in the darkness", October 3-5, 2007, Mao ... more 10 pages, 2 tables.-- En: "Supernovae: lights in the darkness", October 3-5, 2007, Mao (Menorca), to appear in Proceedings of Science.Thermonuclear (type Ia) supernovae are explosions in accreting white dwarfs, but the exact scenario leading to these explosions is still unclear. An important step to clarify this point is to understand the behaviour of accreting white dwarfs in close binary systems. The characteristics of the white dwarf (mass, chemical composition, luminosity), the accreted material (chemical composition) and those related with the properties of the binary system (mass accretion rate), are crucial for the further evolution towards the explosion. An analysis of the outcome of accretion and the implications for the growth of the white dwarf towards the Chandrasekhar mass and its thermonuclear explosion is presented.This research has been funded by the spanish MEC grants ESP2007-61593 and AYA2007-66256, by the catalan AGAUR grant 2005-SGR00378 and by FEDER fu...
Classical novae are potential gamma-ray emitters, both in lines and in a continuum. Continuum emi... more Classical novae are potential gamma-ray emitters, both in lines and in a continuum. Continuum emission (at energies between 20-30 and 511 keV) and line emission at 511 keV are related to positron annihilation and its Comptonization in the expanding shell; 18 F is the main responsible of positron production. The lines at 478 and 1275 keV have their origin on the decay of the radioactive nuclei 7 Be and 22 Na. Updated models of nova explosions have been adopted for the computation of the gamma-ray emission. New yields of some radioactive isotopes directly translate into new detectability distances of classical novae with INTEGRAL.
The origin of Galactic ^26Al is a long-standing question in nuclear astrophysics. The ^26Si(p,γ)^... more The origin of Galactic ^26Al is a long-standing question in nuclear astrophysics. The ^26Si(p,γ)^27P reaction has been thought to be important in the sequence that bypasses the production of this galactic γ-ray emitter ^26Al. Its reaction rate is dominated by a key 3/2^+ proton resonance in ^27P at the explosive hydrogen-burning temperature. However, the current recommended rate in REACLIB still has large uncertainties. In this work, the precise β-decay spectroscopy of the drip-line nucleus ^27S was studied by an implantation-decay method, where the β-delayed protons and γ rays were measured simultaneously. We observed for the first time β-delayed γ ray at 1125(2) keV from ^27S decay, corresponding to the and exit channel of the astrophysically important 3/2^+ resonance in ^26Si(p,γ)^27P reaction. To date, the most precise proton-separation energy and mass excess of ^27P is determined, and the ratio between γ and proton partial widths is pinned down experimentally for the first time...
Proceedings of International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos - IX — PoS(NIC-IX), 2010
Rates of sub-barrier, radiative capture reactions involving radioactive reactants, needed for und... more Rates of sub-barrier, radiative capture reactions involving radioactive reactants, needed for understanding various astrophysical explosive scenarios, are often quite difficult to measure directly at relevant stellar temperatures. In general relatively intense radioactive beams (>10 11 /s) are needed for these inverse kinematic studies, as cross sections are very low. A new production approach is described herein that would supply such required intensities in a relatively straightforward fashion. While this system may have many applications, one area could be increasing our understanding of classical novae and X-ray bursts.
… New science will be driven by time-domain population studies at MeV γ-ray energies. This scienc... more … New science will be driven by time-domain population studies at MeV γ-ray energies. This science is enabled by next-generation γ-ray instruments with one to two orders of magnitude better sensitivity, larger sky coverage, and faster cadence than all previous γ-ray instruments. This transformative capability …
Type I X-ray bursts are thermonuclear explosions that occur in the envelopes of accreting neutron... more Type I X-ray bursts are thermonuclear explosions that occur in the envelopes of accreting neutron stars. Detailed observations of these phenomena have prompted numerous studies in theoretical astrophysics and experimental nuclear physics since their discovery over 35 years ago. In this review, we begin by discussing key observational features of these phenomena that may be sensitive to the particular patterns of nucleosynthesis from the associated thermonuclear burning. We then summarize efforts to model type I X-ray bursts, with emphasis on determining the nuclear physics processes involved throughout these bursts. We discuss and evaluate limitations in the models, particularly with regard to key uncertainties in the nuclear physics input. Finally, we examine recent, relevant experimental measurements and outline future prospects to improve our understanding of these unique environments from observational, theoretical and experimental perspectives.
The shield of the INTEGRAL spectrometer provides a large detection area with a wide field-of-view... more The shield of the INTEGRAL spectrometer provides a large detection area with a wide field-of-view. Calculations have been performed to check whether the temporal analysis of the counting rate of the SPI anticoincidence allows the detection of explosions of novae. The background rate of the shield as well as its response to gamma-ray have been modelled with monte-carlo simulations. Accounting
The 15O(alpha,gamma)19Ne reaction is one of two known routes for breakout from the hot CNO cycles... more The 15O(alpha,gamma)19Ne reaction is one of two known routes for breakout from the hot CNO cycles into the rp process. Its astrophysical rate depends on the decay properties of excited states in 19Ne lying just above the 15O + alpha threshold. We have measured the alpha-decay branching ratios for these states using the p(21Ne,t)19Ne reaction at 43 MeV/u. Combining our branching ratio measurements with previous determinations of the radiative widths of these states, we calculate the astrophysical rate of 15O(alpha,gamma)19Ne. Using this reaction rate, we perform hydrodynamic calculations of nova outbursts and conclude that no significant breakout from the hot CNO cycles into the rp process occurs in classical novae via 15O(alpha,gamma)19Ne.
Modelisations of galactic 1.275 MeV emission produced by the decay 22Na have been performed for s... more Modelisations of galactic 1.275 MeV emission produced by the decay 22Na have been performed for several frequency-spatial distributions of ONe novae. Recent results of nova rates and their distributions in our Galaxy have been used. These modelisations allow to estimate the lower-limit of the 22Na mass ejected per ONe novae detectable with the future spectrometer (SPI) of the INTEGRAL observatory as a function of their frequency-spatial distribution in the Galaxy. Calculations using recent estimations of the expected 22Na mass ejected per ONe nova show that the diffuse galactic 1.275 MeV emission will be difficult to detect with SPI.
Populating states in 22 Mg via the (p, t) reaction in inverse kinematics with a 55 MeV/nucleon 24... more Populating states in 22 Mg via the (p, t) reaction in inverse kinematics with a 55 MeV/nucleon 24 Mg beam, we have measured the proton-decay branching ratios of the levels at 5.96 MeV and 6.05 MeV and obtained an experimental upper limit on the branching ratio of the 5.71 MeV state. On the basis of the present and previous measurements, we assign spins and parities to the 5.96 MeV and 6.05 MeV states. We combine our branching ratios with independent measurements of the lifetimes of these states or their 22 Ne analogs to compute the resonance strengths and thereby the astrophysical rate of the 21 Na(p, γ) 22 Mg reaction. We perform hydrodynamic calculations of nova outbursts with this new rate and analyze its impact on 22 Na yields.
The 30 P(p, γ) 31 S reaction rate is expected to be the principal determinant for the endpoint of... more The 30 P(p, γ) 31 S reaction rate is expected to be the principal determinant for the endpoint of nucleosynthesis in classical novae. To date, the reaction rate has only been estimated through Hauser-Feschbach calculations and is unmeasured experimentally. This paper aims to remedy this situation. Excited states in 31 S and 31 P were populated in the 12 C(20 Ne,n) and 12 C(20 Ne,p) reactions, respectively, at a beam energy of 32 MeV, and their resulting γ decay was detected with the Gammasphere array. Around half the relevant proton unbound states in 31 S corresponding to the Gamow window for the 30 P(p, γ) 31 S reaction were identified. The properties of the unobserved states were inferred from mirror symmetry using our extended data on 31 P. The implications of this new spectroscopic information for the 30 P(p, γ) 31 S reaction rate are considered and recommendations for future work with radioactive beams are discussed.
Gamma-ray telescopes in orbit around the Earth are searching for evidence of the elusive radionuc... more Gamma-ray telescopes in orbit around the Earth are searching for evidence of the elusive radionuclide 22 Na produced in novae. Previously published uncertainties in the dominant destructive reaction, 22 Na(p, γ) 23 Mg, indicated new measurements in the proton energy range of 150 to 300 keV were needed to constrain predictions. We have measured the resonance strengths, energies, and branches directly and absolutely by using protons from the University of Washington accelerator with a specially designed beamline, which included beam rastering and cold vacuum protection of the 22 Na implanted targets. The targets, fabricated at TRIUMF-ISAC, displayed minimal degradation over a ∼ 20 C bombardment as a result of protective layers. We avoided the need to know the absolute stopping power, and hence the target composition, by extracting resonance strengths from excitation functions integrated over proton energy. Our measurements revealed that resonance strengths for Ep = 213, 288, 454, and 610 keV are stronger by factors of 2.4 to 3.2 than previously reported. Upper limits have been placed on proposed resonances at 198-, 209-, and 232-keV. These substantially reduce the uncertainty in the reaction rate. We have re-evaluated the 22 Na(p, γ) reaction rate, and our measurements indicate the resonance at 213 keV makes the most significant contribution to 22 Na destruction in novae. Hydrodynamic simulations including our rate indicate that the expected abundance of 22 Na ejecta from a classical nova is reduced by factors between 1.5 and 2, depending on the mass of the white-dwarf star hosting the nova explosion.
Classical novae are potential gamma-ray emitters, because of the disintegration of some radioacti... more Classical novae are potential gamma-ray emitters, because of the disintegration of some radioactive nuclei synthesized during the explosion. Some short-lived isotopes (such as 13 N and 18 F), as well as the medium-lived 22 Na, decay emitting positrons, which annihilate with electrons and thus are responsible for the prompt emission of gamma-rays from novae. This emission consists of a 511 keV line plus a continuum between 20 and 511 keV, and is released before the maximum in visual luminosity, i.e., before the discovery of the nova. The main characteristics of this prompt emission, together with the related uncertainties (both of nuclear and hydrodynamical origin, with a particular emphasis on the influence of the envelope properties) and prospects for detectability are analyzed in this paper.
We examine the sensitivity of nucleosynthesis in Type I X-ray bursts to variations in nuclear rat... more We examine the sensitivity of nucleosynthesis in Type I X-ray bursts to variations in nuclear rates. As a large number of nuclear processes are involved in these phenomena-with the vast majority of reaction rates only determined theoretically due to the lack of any experimental information-our results can provide a means for determining which rates play significant roles in the thermonuclear runaway. These results may then motivate new experiments. For our studies, we have performed a comprehensive series of one-zone post-processing calculations in conjunction with various representative X-ray burst thermodynamic histories. We present those reactions whose rate variations have the largest effects on yields in our studies.
Monthly Notices of the Royal Astronomical Society, 1998
We investigate the evolution of cooling helium atmosphere white dwarfs using a full evolutionary ... more We investigate the evolution of cooling helium atmosphere white dwarfs using a full evolutionary code, specifically developed to follow the effects of element diffusion and gravitational settling on white dwarf cooling. The major difference between this work and previous work is that we use more recent opacity data from the OPAL project. Since, in general, these opacities are higher than those available 10 years ago, at a given effective temperature, convection zones go deeper than in models with older opacity data. Thus convective dredge-up of observationally detectable carbon in helium atmosphere white dwarfs can occur for thicker helium layers than found by Pelletier et al. We find that the range of observed C to He ratios in different DQ white dwarfs of similar effective temperature is well explained by a range of initial helium layer mass between 10 ¹3 and 10 ¹2 M ᭪ , in good agreement with stellar evolution theory, assuming a typical white dwarf mass of 0:6 M ᭪. We also predict that oxygen will be present in DQ white dwarf atmospheres in detectable amounts if the helium layer mass is near the lower limit compatible with stellar evolution theory. Determination of the oxygen abundance has the potential of providing information on the profile of oxygen in the core and hence on the important 12 Cða; gÞ 16 O reaction rate.
Monthly Notices of the Royal Astronomical Society, 2000
Models of Galactic 1.275-MeV emission produced by the decay of the radionuclide 22 Na have been c... more Models of Galactic 1.275-MeV emission produced by the decay of the radionuclide 22 Na have been computed. Several frequency±spatial distributions of novae have been investigated using recent results of nova rates and spatial distributions of novae in our Galaxy. These models allow us to estimate the lower limit of the 22 Na mass ejected per ONe nova detectable with the future spectrometer (SPI) of the INTEGRAL observatory as a function of the frequency±spatial distribution of ONe novae in the Galaxy. Calculations using recent estimations of the expected 22 Na mass ejected per ONe nova show that the detection of the Galactic emission of 1.275-MeV photons will be difficult with the future spectrometer of the INTEGRAL observatory, whereas the cumulative emission around the Galactic Centre has some chance of being detected during the deep survey of the central radian of the Galaxy.
10 pages, 2 tables.-- En: "Supernovae: lights in the darkness", October 3-5, 2007, Mao ... more 10 pages, 2 tables.-- En: "Supernovae: lights in the darkness", October 3-5, 2007, Mao (Menorca), to appear in Proceedings of Science.Thermonuclear (type Ia) supernovae are explosions in accreting white dwarfs, but the exact scenario leading to these explosions is still unclear. An important step to clarify this point is to understand the behaviour of accreting white dwarfs in close binary systems. The characteristics of the white dwarf (mass, chemical composition, luminosity), the accreted material (chemical composition) and those related with the properties of the binary system (mass accretion rate), are crucial for the further evolution towards the explosion. An analysis of the outcome of accretion and the implications for the growth of the white dwarf towards the Chandrasekhar mass and its thermonuclear explosion is presented.This research has been funded by the spanish MEC grants ESP2007-61593 and AYA2007-66256, by the catalan AGAUR grant 2005-SGR00378 and by FEDER fu...
Classical novae are potential gamma-ray emitters, both in lines and in a continuum. Continuum emi... more Classical novae are potential gamma-ray emitters, both in lines and in a continuum. Continuum emission (at energies between 20-30 and 511 keV) and line emission at 511 keV are related to positron annihilation and its Comptonization in the expanding shell; 18 F is the main responsible of positron production. The lines at 478 and 1275 keV have their origin on the decay of the radioactive nuclei 7 Be and 22 Na. Updated models of nova explosions have been adopted for the computation of the gamma-ray emission. New yields of some radioactive isotopes directly translate into new detectability distances of classical novae with INTEGRAL.
The origin of Galactic ^26Al is a long-standing question in nuclear astrophysics. The ^26Si(p,γ)^... more The origin of Galactic ^26Al is a long-standing question in nuclear astrophysics. The ^26Si(p,γ)^27P reaction has been thought to be important in the sequence that bypasses the production of this galactic γ-ray emitter ^26Al. Its reaction rate is dominated by a key 3/2^+ proton resonance in ^27P at the explosive hydrogen-burning temperature. However, the current recommended rate in REACLIB still has large uncertainties. In this work, the precise β-decay spectroscopy of the drip-line nucleus ^27S was studied by an implantation-decay method, where the β-delayed protons and γ rays were measured simultaneously. We observed for the first time β-delayed γ ray at 1125(2) keV from ^27S decay, corresponding to the and exit channel of the astrophysically important 3/2^+ resonance in ^26Si(p,γ)^27P reaction. To date, the most precise proton-separation energy and mass excess of ^27P is determined, and the ratio between γ and proton partial widths is pinned down experimentally for the first time...
Proceedings of International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos - IX — PoS(NIC-IX), 2010
Rates of sub-barrier, radiative capture reactions involving radioactive reactants, needed for und... more Rates of sub-barrier, radiative capture reactions involving radioactive reactants, needed for understanding various astrophysical explosive scenarios, are often quite difficult to measure directly at relevant stellar temperatures. In general relatively intense radioactive beams (>10 11 /s) are needed for these inverse kinematic studies, as cross sections are very low. A new production approach is described herein that would supply such required intensities in a relatively straightforward fashion. While this system may have many applications, one area could be increasing our understanding of classical novae and X-ray bursts.
… New science will be driven by time-domain population studies at MeV γ-ray energies. This scienc... more … New science will be driven by time-domain population studies at MeV γ-ray energies. This science is enabled by next-generation γ-ray instruments with one to two orders of magnitude better sensitivity, larger sky coverage, and faster cadence than all previous γ-ray instruments. This transformative capability …
Type I X-ray bursts are thermonuclear explosions that occur in the envelopes of accreting neutron... more Type I X-ray bursts are thermonuclear explosions that occur in the envelopes of accreting neutron stars. Detailed observations of these phenomena have prompted numerous studies in theoretical astrophysics and experimental nuclear physics since their discovery over 35 years ago. In this review, we begin by discussing key observational features of these phenomena that may be sensitive to the particular patterns of nucleosynthesis from the associated thermonuclear burning. We then summarize efforts to model type I X-ray bursts, with emphasis on determining the nuclear physics processes involved throughout these bursts. We discuss and evaluate limitations in the models, particularly with regard to key uncertainties in the nuclear physics input. Finally, we examine recent, relevant experimental measurements and outline future prospects to improve our understanding of these unique environments from observational, theoretical and experimental perspectives.
The shield of the INTEGRAL spectrometer provides a large detection area with a wide field-of-view... more The shield of the INTEGRAL spectrometer provides a large detection area with a wide field-of-view. Calculations have been performed to check whether the temporal analysis of the counting rate of the SPI anticoincidence allows the detection of explosions of novae. The background rate of the shield as well as its response to gamma-ray have been modelled with monte-carlo simulations. Accounting
The 15O(alpha,gamma)19Ne reaction is one of two known routes for breakout from the hot CNO cycles... more The 15O(alpha,gamma)19Ne reaction is one of two known routes for breakout from the hot CNO cycles into the rp process. Its astrophysical rate depends on the decay properties of excited states in 19Ne lying just above the 15O + alpha threshold. We have measured the alpha-decay branching ratios for these states using the p(21Ne,t)19Ne reaction at 43 MeV/u. Combining our branching ratio measurements with previous determinations of the radiative widths of these states, we calculate the astrophysical rate of 15O(alpha,gamma)19Ne. Using this reaction rate, we perform hydrodynamic calculations of nova outbursts and conclude that no significant breakout from the hot CNO cycles into the rp process occurs in classical novae via 15O(alpha,gamma)19Ne.
Modelisations of galactic 1.275 MeV emission produced by the decay 22Na have been performed for s... more Modelisations of galactic 1.275 MeV emission produced by the decay 22Na have been performed for several frequency-spatial distributions of ONe novae. Recent results of nova rates and their distributions in our Galaxy have been used. These modelisations allow to estimate the lower-limit of the 22Na mass ejected per ONe novae detectable with the future spectrometer (SPI) of the INTEGRAL observatory as a function of their frequency-spatial distribution in the Galaxy. Calculations using recent estimations of the expected 22Na mass ejected per ONe nova show that the diffuse galactic 1.275 MeV emission will be difficult to detect with SPI.
Populating states in 22 Mg via the (p, t) reaction in inverse kinematics with a 55 MeV/nucleon 24... more Populating states in 22 Mg via the (p, t) reaction in inverse kinematics with a 55 MeV/nucleon 24 Mg beam, we have measured the proton-decay branching ratios of the levels at 5.96 MeV and 6.05 MeV and obtained an experimental upper limit on the branching ratio of the 5.71 MeV state. On the basis of the present and previous measurements, we assign spins and parities to the 5.96 MeV and 6.05 MeV states. We combine our branching ratios with independent measurements of the lifetimes of these states or their 22 Ne analogs to compute the resonance strengths and thereby the astrophysical rate of the 21 Na(p, γ) 22 Mg reaction. We perform hydrodynamic calculations of nova outbursts with this new rate and analyze its impact on 22 Na yields.
The 30 P(p, γ) 31 S reaction rate is expected to be the principal determinant for the endpoint of... more The 30 P(p, γ) 31 S reaction rate is expected to be the principal determinant for the endpoint of nucleosynthesis in classical novae. To date, the reaction rate has only been estimated through Hauser-Feschbach calculations and is unmeasured experimentally. This paper aims to remedy this situation. Excited states in 31 S and 31 P were populated in the 12 C(20 Ne,n) and 12 C(20 Ne,p) reactions, respectively, at a beam energy of 32 MeV, and their resulting γ decay was detected with the Gammasphere array. Around half the relevant proton unbound states in 31 S corresponding to the Gamow window for the 30 P(p, γ) 31 S reaction were identified. The properties of the unobserved states were inferred from mirror symmetry using our extended data on 31 P. The implications of this new spectroscopic information for the 30 P(p, γ) 31 S reaction rate are considered and recommendations for future work with radioactive beams are discussed.
Gamma-ray telescopes in orbit around the Earth are searching for evidence of the elusive radionuc... more Gamma-ray telescopes in orbit around the Earth are searching for evidence of the elusive radionuclide 22 Na produced in novae. Previously published uncertainties in the dominant destructive reaction, 22 Na(p, γ) 23 Mg, indicated new measurements in the proton energy range of 150 to 300 keV were needed to constrain predictions. We have measured the resonance strengths, energies, and branches directly and absolutely by using protons from the University of Washington accelerator with a specially designed beamline, which included beam rastering and cold vacuum protection of the 22 Na implanted targets. The targets, fabricated at TRIUMF-ISAC, displayed minimal degradation over a ∼ 20 C bombardment as a result of protective layers. We avoided the need to know the absolute stopping power, and hence the target composition, by extracting resonance strengths from excitation functions integrated over proton energy. Our measurements revealed that resonance strengths for Ep = 213, 288, 454, and 610 keV are stronger by factors of 2.4 to 3.2 than previously reported. Upper limits have been placed on proposed resonances at 198-, 209-, and 232-keV. These substantially reduce the uncertainty in the reaction rate. We have re-evaluated the 22 Na(p, γ) reaction rate, and our measurements indicate the resonance at 213 keV makes the most significant contribution to 22 Na destruction in novae. Hydrodynamic simulations including our rate indicate that the expected abundance of 22 Na ejecta from a classical nova is reduced by factors between 1.5 and 2, depending on the mass of the white-dwarf star hosting the nova explosion.
Classical novae are potential gamma-ray emitters, because of the disintegration of some radioacti... more Classical novae are potential gamma-ray emitters, because of the disintegration of some radioactive nuclei synthesized during the explosion. Some short-lived isotopes (such as 13 N and 18 F), as well as the medium-lived 22 Na, decay emitting positrons, which annihilate with electrons and thus are responsible for the prompt emission of gamma-rays from novae. This emission consists of a 511 keV line plus a continuum between 20 and 511 keV, and is released before the maximum in visual luminosity, i.e., before the discovery of the nova. The main characteristics of this prompt emission, together with the related uncertainties (both of nuclear and hydrodynamical origin, with a particular emphasis on the influence of the envelope properties) and prospects for detectability are analyzed in this paper.
We examine the sensitivity of nucleosynthesis in Type I X-ray bursts to variations in nuclear rat... more We examine the sensitivity of nucleosynthesis in Type I X-ray bursts to variations in nuclear rates. As a large number of nuclear processes are involved in these phenomena-with the vast majority of reaction rates only determined theoretically due to the lack of any experimental information-our results can provide a means for determining which rates play significant roles in the thermonuclear runaway. These results may then motivate new experiments. For our studies, we have performed a comprehensive series of one-zone post-processing calculations in conjunction with various representative X-ray burst thermodynamic histories. We present those reactions whose rate variations have the largest effects on yields in our studies.
Monthly Notices of the Royal Astronomical Society, 1998
We investigate the evolution of cooling helium atmosphere white dwarfs using a full evolutionary ... more We investigate the evolution of cooling helium atmosphere white dwarfs using a full evolutionary code, specifically developed to follow the effects of element diffusion and gravitational settling on white dwarf cooling. The major difference between this work and previous work is that we use more recent opacity data from the OPAL project. Since, in general, these opacities are higher than those available 10 years ago, at a given effective temperature, convection zones go deeper than in models with older opacity data. Thus convective dredge-up of observationally detectable carbon in helium atmosphere white dwarfs can occur for thicker helium layers than found by Pelletier et al. We find that the range of observed C to He ratios in different DQ white dwarfs of similar effective temperature is well explained by a range of initial helium layer mass between 10 ¹3 and 10 ¹2 M ᭪ , in good agreement with stellar evolution theory, assuming a typical white dwarf mass of 0:6 M ᭪. We also predict that oxygen will be present in DQ white dwarf atmospheres in detectable amounts if the helium layer mass is near the lower limit compatible with stellar evolution theory. Determination of the oxygen abundance has the potential of providing information on the profile of oxygen in the core and hence on the important 12 Cða; gÞ 16 O reaction rate.
Monthly Notices of the Royal Astronomical Society, 2000
Models of Galactic 1.275-MeV emission produced by the decay of the radionuclide 22 Na have been c... more Models of Galactic 1.275-MeV emission produced by the decay of the radionuclide 22 Na have been computed. Several frequency±spatial distributions of novae have been investigated using recent results of nova rates and spatial distributions of novae in our Galaxy. These models allow us to estimate the lower limit of the 22 Na mass ejected per ONe nova detectable with the future spectrometer (SPI) of the INTEGRAL observatory as a function of the frequency±spatial distribution of ONe novae in the Galaxy. Calculations using recent estimations of the expected 22 Na mass ejected per ONe nova show that the detection of the Galactic emission of 1.275-MeV photons will be difficult with the future spectrometer of the INTEGRAL observatory, whereas the cumulative emission around the Galactic Centre has some chance of being detected during the deep survey of the central radian of the Galaxy.
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Papers by Jordi Jose