Lunar University Network for Astrophysics Research - Science … · 2011-08-30 · • Black Hole...
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R.S. Miller University of Alabama in Huntsville [email protected] The Lunar Occultation Observer (LOCO) is a new γ-ray astrophysics mission concept expected to have unprecedented sensitivity in the nuclear regime (~0.1-10 MeV). Top-level science goals are consistent with those formalized in the National Research Council’s recent decadal review "New Worlds, New Horizons in Astronomy and Astrophysics", and include, but are not limited to: time domain astronomy, all-sky surveys, galactic nucleosynthesis, galaxies & black holes, and to extend knowledge across electromagnetic spectrum. LOCO will also be uniquely capable of addressing key questions in solar physics and possibly planetary science. The breadth of science enabled by observations in the nuclear regime - from probing the most cataclysmic events in the Cosmos, to understanding the life cycle of matter in our Galaxy, to probing energetic processes on our nearest star, to the search for one of life’s fundamental components (water) - is significant. The next-generation capabilities for high-sensitivity observations by LOCO will be transformational. We will review the science goals, discuss the science-driven instrument and mission requirements specifications, and provide preliminary estimates of science return for the LOCO mission. Science Goals for the Lunar Occultation Observer (LOCO) Mission Concept Abstract Goals & Decadal Review Galactic Nucleosynthesis Motivation Lunar Science 26Al all-sky map made by COMPTEL (left). Ratios of 60Fe/26Al as determined by a number of independent observations (right). The hatched regions and yellow line show theoretical predictions; discrepancies derive from the different nuclear physics parameterizations used, as well as details of stellar evolution models. Prantzos 2004 Limongi & Chie 2006 Timmes et al 1995 2004 1982 1994 1997 1997 1998 2007 Nuclear Astrophysics Solar Physics LINE EMISSION ( MeV) FLUX LIMIT (cm -2 s -1 MeV -1 ) 1.63 6.3×10 -5 2.223 4.1×10 -5 8.07 1.9×10 -5 1 to 10 (broadband) 2.1×10 -5 Neutron capture and γ-ray de-excitation lines are sensitive probes of the accelerated ion populations. For example, the capture of low energy protons (>1 MeV) will give rise to specific line emission from 20 Ne (1.63 MeV) , 12 C (2.37 MeV), 13 C (8.07 MeV), 14 N (7.56 MeV), 15 N (12.44 MeV) [26], while the 2.223 MeV neutron capture line fluence is a proxy for the total energy of accelerated nuclei having energies above ~10 MeV/nucleon. Flares Quiescent Emission Non-thermal particle acceleration may be taking place in the form of solar micro- or nano-flares. These non-thermal processes are supported by X-ray observations of small flares and should be observable at nuclear energies during periods of low solar activity. Thus the same nuclear emission expected from flares may also be present in the quiescent emission - albeit at significantly reduced intensities. To date, the searches have led only to upper limits on the “quiescent” accelerated ion population (Table 2). This is due, in part, to the relatively small effective areas of the observing instruments and/or short exposures. The neutron capture line at 2.223 MeV is of particular interest since the presence of this line implies a continuous power input for ions with energies >10 MeV. SOURCE TASK PERFORMANCE METRIC Type-Ia SNe Time evolution of 56 Co & broadband emission derived from analytical models Light-curve parameterization Sensitivity to explosive nucleosynthesis models Systematics from lunar/solar backgrounds Galactic Diffuse 26 Al and/or annihilation radiation derived from Monte Carlo simulation Quantify systematics impacting spatial morphology determination driven by long timescale variations in backgrounds (e.g. lunar albedo) Flare Generate flare library from Monte Carlo simulation Flux & spectroscopic performance Quantify science impact Quiet Sun Scale flare library to quiescent levels Flux & spectroscopic performance Impact of long timescale variations in backgrounds (e.g. lunar albedo) Quantify science impact Lunar Albedo Produce average and spatially resolved lunar albedo model Elemental abundance sensitivities Impact of solar activity variations Imaging (i.e. lunar mapping) performance Lunar Albedo + H 2 O Add localized hydrogen distribution to albedo model Quantify sensitivity to H 2 O weight fraction vs. localization Imaging (i.e. lunar mapping) performance Ongoing Efforts Gamma-ray spectroscopy is an established technique for planetary exploration (e.g. [40, 41]), yielding important information about the elemental compositions of airless bodies throughout the Solar System. In contrast to X-rays, which give information about the top few microns of the surface layers of these planetary bodies, gamma-rays can probe to depths of approximately a meter. This enables differentiation of regolith, and potentially the identification of water and other buried resources While some of the spectral features shown here are dominated by a single element (e.g. Fe, O, Th, Si, and K), all the peaks have contributions from at least two elements. Near 7 MeV, for example, Ti and O have nearly equal contributions, while near 2.2 MeV - the unmistakable signature of neutron capture on hydrogen - there are contributions from both Al and the U decay chain [1, 2] The Moon is a unique location for experimental astrophysics and itʼs beneficial characteristics can be brought to bear on challenges in high- energy astrophysics, solar physics, and planetary sciences in particular. In particular, the lunar environment provides a unique environment for nuclear (MeV) γ-ray astrophysics observations. While observations in other electromagnetic regimes can also leverage the Moon, high- sensitivity investigations in the range 0.1-10 MeV are uniquely enabled there. Lunar and solar science are integral to any successful lunar-based endeavor operating in the nuclear regime. As one example, the Moonʼs γ- ray albedo is the dominant source of background at MeV energies. The albedo is produced by cosmic-ray bombardment of the regolith, and therefore its intensity is directly related to the flux of primary cosmic-rays entering the inner solar system, which is in turn affected by the solar cycle and related activity. A lunar scientific platform, therefore, represents an opportunity for synergistic investigations spanning topical areas in astrophysics, solar physics, and planetary/lunar science. Interdisciplinary science investigations (solar, planetary) leveraged by our primary nuclear astrophysics goals will be transformative - due in part to the requirement for a meter-class γ-ray spectrometer with excellent energy resolution (<4% FWHM @ 0.662 MeV), and its operation from lunar orbit. The specifications for this primary instrument are driven by the astrophysics goals, yet provide a unique, and critical, set of capabilities in the other topical areas. As an example, the baseline spectrometer configuration will have a sensitivity: • ~10 1 x greater than COMPTEL, the last large-scale nuclear astrophysics survey mission • ~10 2 x greater than RHESSI, the most recent high-energy solar mission • ~10 3 x greater than the Lunar Prospector Gamma-ray Spectrometer The transformational potential is clear. A subset of science goals are reviewed here. Details of the LOCO mission concept will be presented during Parallel Session #8, 12:00 July 21 Lunar γ-ray spectra based on elemental abundances of Reedy. Shown are the spectra for (a) a Lunar Prospector GRS- like energy resolution (~12% FWHM @ 0.662 MeV), and (b) the LOCO baseline spectroscopy performance of ~3% FWHM @ 0.226 MeV. Orange bands show the elemetal RMS variation across the lunar surface, based on LP-GRS observations. Also shown is the cosmic diffuse γ-ray flux (solid line). Emission lines below the diffuse emission are unlikely to be detected. (a) (b) The breadth of science enabled by observations in the nuclear regime - from probing the most cataclysmic events in the Cosmos, to understanding the life cycle of matter in our Galaxy, to probing energetic processes on our nearest star, to the search for one of lifeʼs fundamental components (water) - is significant. Next-generation capabilities for high- sensitivity observations such processes will be transformational. Top-level science goals are consistent with those formalized in the National Research Councilʼs recent decadal review New Worlds, New Horizons in Astronomy and Astrophyiscs [9], and include, but are not limited to: • Time Domain Astronomy • All-sky Surveys • Galactic Nucleosynthesis • Galaxies & Black Holes • Extend knowledge across electromagnetic spectrum •Star Formation Rates Cosmic nucleosynthesis takes place in stars whose lives end in supernovae or novae. Mapping the Galactic distributions (e.g. Figure 1) of the radioactive signatures from these events - including nuclear lines (e.g. 22 Na, 44 Ti, 60 Fe, 26 Al), nuclear de-excitations ( 12 C, 16 O, 56 Fe), and e + e - annihilations - will enable detailed investigations of galactic event rates, models of cosmic and galactic evolution, probes of extreme environments, and the underlying dynamic processes shaping the Galaxy. •Novae & Supernovae While Galactic nucleosynthesis can be studied by mapping long-lived isotopic signatures distributed as diffuse emission, short lived isotopes generated and decaying during the early phases of these events can be used to probe their dynamics and structure. Of paramount importance is the understanding of Type Ia supernovae. Issues related to their progenitors, nuclear propagation, shocks and other instabilities could have significant relevance in astrophysical and cosmological contexts. • Black Hole Census & Compact Objects A large fraction of black holes (BHs) are obscured by gas and dust. These BHs span a wide range of masses, from stellar mass objects in our local neighborhood, to supermassive BHs that exist in the nuclei of other galaxies. A survey will provide information relevant to cosmological structure formation as well as the evolution of galaxies and stellar objects. • Dark Matter-Annihilation Radiation The origin of the observed Galactic 511 keV emission is unclear. Competing models include supernovae, unresolved point sources, or dark matter signatures. Improved spectral and spatial resolutions are required for further analysis. • Multiwavelength Correlation Studies The nature of processes powering Active Galactic Nuclei (AGN) requires near-simultaneous observations that span X-rays through TeV gamma-rays. These multi-wavelength observations can give insight into the processes responsible for emission from the central engine (BH), as well as shed light on the spectra of the cosmic diffuse infrared and MeV radiations. •An effective nuclear astrophysics survey mission must address these, and other, multiple high-priority science topics. As such, the key mission implementation requirements include: • Spectroscopic energy resolution: <3% FWHM @ 0.662 MeV ⇒ detect ~3% doppler broadening of 56 Co line from Type-Ia SNe • Flux Sensitivity: ~10 -5 cm -2 s -1 (10 6 sec actual, not on-src) ⇒ 100+ SNe during mission • Wide Field-of-View: maximize ⇒ transients sources, monitoring & variability, time-domain astronomy • Uniform Sky Coverage: maximize ⇒ true survey & all-sky monitoring capability, time-domain astronomy LOCO represents a paradigm shift in nuclear astrophysics - the first mission to utilize occultation imaging as its primary detection technique. The benefits of occultation imaging include: In an effort to improve LOCO science return estimates we have an active program leveraging expertise in nuclear astrophysics, high-energy solar, and lunar science. Utilizing a combination of in-situ measurements, analytic models, and Monte Carlo simulations of both sources and the LOCO mission, these analyses will further refine mission impact and design. While ongoing, a brief overview of topics currently under study include: An example of a key topic in nuclear astrophysics is an improved understanding of the origin of heavy elements and their production within the Galaxy. To date both 26 Al (COMPTEL, INTEGRAL/SPI) and 60 Fe (RHESSI, INTEGRAL/SPI) have been detected as diffuse emission within the Galaxy. Both are believed to be associated with the core-collapse of massive stars, with 26 Al also perhaps injected into the ISM via strong stellar winds. While detections of these isotopes are in agreement with the general outline of nucleosynthesis theory, there are some significant discrepancies in details. Improved mapping capability, as well as energy resolution, can help resolve outstanding issues.
Transcript of Lunar University Network for Astrophysics Research - Science … · 2011-08-30 · • Black Hole...
R.S. Miller University of Alabama in Huntsville [email protected]
The Lunar Occultation Observer (LOCO) is a new γ-ray astrophysics mission concept expected to have unprecedented sensitivity in the nuclear regime (~0.1-10 MeV). Top-level science goals are consistent with those formalized in the National Research Council’s recent decadal review "New Worlds, New Horizons in Astronomy and Astrophysics", and include, but are not limited to: time domain astronomy, all-sky surveys, galactic nucleosynthesis, galaxies & black holes, and to extend knowledge across electromagnetic spectrum. LOCO will also be uniquely capable of addressing key questions in solar physics and possibly planetary science. The breadth of science enabled by observations in the nuclear regime - from probing the most cataclysmic events in the Cosmos, to understanding the life cycle of matter in our Galaxy, to probing energetic processes on our nearest star, to the search for one of life’s fundamental components (water) - is significant. The next-generation capabilities for high-sensitivity observations by LOCO will be transformational. We will review the science goals, discuss the science-driven instrument and mission requirements specifications, and provide preliminary estimates of science return for the LOCO mission.
Science Goals for the Lunar Occultation Observer (LOCO) Mission Concept
Abstract Goals & Decadal Review Galactic Nucleosynthesis
Motivation
Lunar Science
26Al all-sky map made by COMPTEL (left). Ratios of 60Fe/26Al as determined by a number of independent observations (right). The hatched regions and yellow line show theoretical predictions; discrepancies derive from the different nuclear physics parameterizations used, as well as details of stellar evolution models.
Prantzos 2004
Limongi & Chie! 2006
Timmes et al 1995
20041982 1994 1997 1997 1998 2007Nuclear Astrophysics
Solar Physics
LINE EMISSION
(MeV)
FLUX L IMIT (cm-2 s-1 MeV -1)
1.63 6.3×10-5
2.223 4.1×10 -5
8.07 1.9×10 -5
1 to 10 (broadband)
2.1×10 -5
Neutron capture and γ-ray de-excitation lines are sensitive probes of the accelerated ion populations. For example, the capture of low energy protons (>1 MeV) will give rise to specific line emission from 20Ne (1.63 MeV) , 12C (2.37 MeV), 13C (8.07 MeV), 14N (7.56 MeV), 15N (12.44 MeV) [26], while the 2.223 MeV neutron capture line fluence is a proxy for the total energy of accelerated nuclei having energies above ~10 MeV/nucleon.
Flares
Quiescent Emission
Non-thermal particle acceleration may be taking place in the form of solar micro- or nano-flares. These non-thermal processes are supported by X-ray observations of small flares and should be observable at nuclear energies during periods of low solar activity. Thus the same nuclear emission expected from flares may also be present in the quiescent emission - albeit at significantly reduced intensities.To date, the searches have led only to upper limits on the “quiescent” accelerated ion population (Table 2). This is due, in part, to the relatively small effective areas of the observing instruments and/or short exposures.The neutron capture line at 2.223 MeV is of particular interest since the presence of this line implies a continuous power input for ions with energies >10 MeV.
SOURCE TASK PERFORMANCE METRIC
Type-Ia SNe Time evolution of 56Co & broadband emission derived from analytical models
Light-curve parameterization
Sensitivity to explosive nucleosynthesis models
Systematics from lunar/solar backgrounds
Galactic Diffuse 26Al and/or annihilation radiation derived from Monte Carlo simulation
Quantify systematics impacting spatial morphology determination driven by long timescale variations in backgrounds (e.g. lunar albedo)
Flare Generate flare library from Monte Carlo simulation
Flux & spectroscopic performance
Quantify science impact
Quiet Sun Scale flare library to quiescent levels Flux & spectroscopic performance
Impact of long timescale variations in backgrounds (e.g. lunar albedo)
Quantify science impact
Lunar Albedo Produce average and spatially resolved lunar albedo model
Elemental abundance sensitivities
Impact of solar activity variations
Imaging (i.e. lunar mapping) performance
Lunar Albedo + H2O Add localized hydrogen distribution to albedo model
Quantify sensitivity to H2O weight fraction vs. localization
Imaging (i.e. lunar mapping) performance
Ongoing Efforts
Gamma-ray spectroscopy is an established technique for planetary exploration (e.g. [40, 41]), yielding important information about the elemental compositions of airless bodies throughout the Solar System. In contrast to X-rays, which give information about the top few microns of the surface layers of these planetary bodies, gamma-rays can probe to depths of approximately a meter. This enables differentiation of regolith, and potentially the identification of water and other buried resources
While some of the spectral features shown here are dominated by a single element (e.g. Fe, O, Th, Si, and K), all the peaks have contributions from at least two elements. Near 7 MeV, for example, Ti and O have nearly equal contributions, while near 2.2 MeV - the unmistakable signature of neutron capture on hydrogen - there are contributions from both Al and the U decay chain [1, 2]
The Moon is a unique location for experimental astrophysics and itʼs beneficial characteristics can be brought to bear on challenges in high-energy astrophysics, solar physics, and planetary sciences in particular. In particular, the lunar environment provides a unique environment for nuclear (MeV) γ-ray astrophysics observations. While observations in other electromagnetic regimes can also leverage the Moon, high-sensitivity investigations in the range 0.1-10 MeV are uniquely enabled there.Lunar and solar science are integral to any successful lunar-based endeavor operating in the nuclear regime. As one example, the Moonʼs γ-ray albedo is the dominant source of background at MeV energies. The albedo is produced by cosmic-ray bombardment of the regolith, and therefore its intensity is directly related to the flux of primary cosmic-rays entering the inner solar system, which is in turn affected by the solar cycle and related activity. A lunar scientific platform, therefore, represents an opportunity for synergistic investigations spanning topical areas in astrophysics, solar physics, and planetary/lunar science.
Interdisciplinary science investigations (solar, planetary) leveraged by our primary nuclear astrophysics goals will be transformative - due in part to the requirement for a meter-class γ-ray spectrometer with excellent energy resolution (<4% FWHM @ 0.662 MeV), and its operation from lunar orbit. The specifications for this primary instrument are driven by the astrophysics goals, yet provide a unique, and critical, set of capabilities in the other topical areas. As an example, the baseline spectrometer configuration will have a sensitivity:•~101x greater than COMPTEL, the last large-scale nuclear astrophysics survey mission•~102x greater than RHESSI, the most recent high-energy solar mission•~103x greater than the Lunar Prospector Gamma-ray Spectrometer
The transformational potential is clear. A subset of science goals are reviewed here.
Details of the LOCO mission concept will be presented during Parallel Session #8, 12:00 July 21
Lunar γ-ray spectra based on elemental abundances of Reedy. Shown are the spectra for (a) a Lunar Prospector GRS-like energy resolution (~12% FWHM @ 0.662 MeV), and (b) the LOCO baseline spectroscopy performance of ~3% FWHM @ 0.226 MeV.
Orange bands show the elemetal RMS variation across the lunar surface, based on LP-GRS observations.
Also shown is the cosmic diffuse γ-ray flux (solid line). Emission lines below the diffuse emission are unlikely to be detected.
(a)
(b)
The breadth of science enabled by observations in the nuclear regime - from probing the most cataclysmic events in the Cosmos, to understanding the life cycle of matter in our Galaxy, to probing energetic processes on our nearest star, to the search for one of lifeʼs fundamental components (water) - is significant. Next-generation capabilities for high-sensitivity observations such processes will be transformational. Top-level science goals are consistent with those formalized in the National Research Councilʼs recent decadal review New Worlds, New Horizons in Astronomy and Astrophyiscs [9], and include, but are not limited to:
• Time Domain Astronomy• All-sky Surveys• Galactic Nucleosynthesis• Galaxies & Black Holes• Extend knowledge across electromagnetic spectrum
•Star Formation Rates Cosmic nucleosynthesis takes place in stars whose lives end in supernovae or novae. Mapping the Galactic distributions (e.g. Figure 1) of the radioactive signatures from these events - including nuclear lines (e.g. 22Na, 44Ti, 60Fe, 26Al), nuclear de-excitations (12C, 16O, 56Fe), and e+e- annihilations - will enable detailed investigations of galactic event rates, models of cosmic and galactic evolution, probes of extreme environments, and the underlying dynamic processes shaping the Galaxy. •Novae & Supernovae While Galactic nucleosynthesis can be studied by mapping long-lived isotopic signatures distributed as diffuse emission, short lived isotopes generated and decaying during the early phases of these events can be used to probe their dynamics and structure. Of paramount importance is the understanding of Type Ia supernovae. Issues related to their progenitors, nuclear propagation, shocks and other instabilities could have significant relevance in astrophysical and cosmological contexts.• Black Hole Census & Compact Objects A large fraction of black holes (BHs) are obscured by gas and dust. These BHs span a wide range of masses, from stellar mass objects in our local neighborhood, to supermassive BHs that exist in the nuclei of other galaxies. A survey will provide information relevant to cosmological structure formation as well as the evolution of galaxies and stellar objects. • Dark Matter-Annihilation Radiation The origin of the observed Galactic 511 keV emission is unclear. Competing models include supernovae, unresolved point sources, or dark matter signatures. Improved spectral and spatial resolutions are required for further analysis.• Multiwavelength Correlation Studies The nature of processes powering Active Galactic Nuclei (AGN) requires near-simultaneous observations that span X-rays through TeV gamma-rays. These multi-wavelength observations can give insight into the processes responsible for emission from the central engine (BH), as well as shed light on the spectra of the cosmic diffuse infrared and MeV radiations.
•An effective nuclear astrophysics survey mission must address these, and other, multiple high-priority science topics. As such, the key mission implementation requirements include:
• Spectroscopic energy resolution: <3% FWHM @ 0.662 MeV ⇒ detect ~3% doppler broadening of 56Co line from Type-Ia SNe
• Flux Sensitivity: ~10-5 cm-2 s-1 (106 sec actual, not on-src) ⇒ 100+ SNe during mission
• Wide Field-of-View: maximize ⇒ transients sources, monitoring & variability, time-domain astronomy
• Uniform Sky Coverage: maximize ⇒ true survey & all-sky monitoring capability, time-domain astronomy
LOCO represents a paradigm shift in nuclear astrophysics - the first mission to utilize occultation imaging as its primary detection technique. The benefits of occultation imaging include:
In an effort to improve LOCO science return estimates we have an active program leveraging expertise in nuclear astrophysics, high-energy solar, and lunar science. Utilizing a combination of in-situ measurements, analytic models, and Monte Carlo simulations of both sources and the LOCO mission, these analyses will further refine mission impact and design. While ongoing, a brief overview of topics currently under study include:
An example of a key topic in nuclear astrophysics is an improved understanding of the origin of heavy elements and their production within the Galaxy. To date both 26Al (COMPTEL, INTEGRAL/SPI) and 60Fe (RHESSI, INTEGRAL/SPI) have been detected as diffuse emission within the Galaxy. Both are believed to be associated with the core-collapse of massive stars, with 26Al also perhaps injected into the ISM via strong stellar winds.
While detections of these isotopes are in agreement with the general outline of nucleosynthesis theory, there are some significant discrepancies in details. Improved mapping capability, as well as energy resolution, can help resolve outstanding issues.
