New Tools, New Universes: Correlation in Astronomy

Computer Measurement of Line Strengths with Application to the Methane Spectrum

One of the complexities in modelling integrated spectra of stellar populations is the effect of interacting binary stars besides type Ia supernovae (SNeIa). These include common envelope systems, CVs, novae, and are usually ignored in models predicting the chemistry and spectral absorption line strengths in galaxies. In this paper predictions of chemical yields from populations of single and binary stars are incorporated into a galactic chemical evolution model to explore the significance of the effects of these other binary yields. Effects on spectral line strengths from different progenitor channels of SNeIa are also explored. Small systematic effects are found when the yields from binaries, other than SNeIa, are included, for a given star formation history. These effects are, at present, within the observational uncertainties on the line strengths. More serious differences can arise in considering different types of SNIa models, their rates and contributions.

In this book a collection of the lecture notes given during the Eighth European Summer School on Experimental Nuclear Astrophysics is given. The school, whose first edition was first held in 2003, took place from 13 to 20 of September 2015 in Santa Tecla, a small village about 15 km north of Catania, characterized by its position on the volcanic shores of the Ionian Sea, surrounded by the spectacular "Timpa" area, a green protected park specific for its mediterranean vegetation. 80 young students and researchers from more than 20 countries attended the lectures and were also encouraged to present their work and results.

view Abstract Citations (191) References (103) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Late Emission from Supernovae: A Window on Stellar Nucleosynthesis Fransson, Claes ; Chevalier, Roger A. Abstract Observations of Type Ib and Type II supernovae show strong evidence that the energy input after 100-200 days is dominated by γ-rays from radioactive decay of ^56^Co. The energy deposition of these γ-rays, and the subsequent thermalization of the nonthermal electrons, are calculated using Monte Carlo techniques. The relative fractions going into heating, ionizations, and direct excitations are studied. Above an electron fraction of ~ 0.1 direct excitations are negligible, and the line emission arises from thermal processes. The temperature and ionization structure of the ejecta and its emission are discussed for general cases, and for detailed nucleosynthesis models. It is found that the emission is dominated by neutral and singly ionized lines, the strongest due to [O I], [Ca II], Mg I], [C I] and [Si I]. Tests of the explosion models and determinations of absolute and relative abundances from the late emission are studied. For a given model, the relative and absolute line strengths depend on both the column densities of the different abundance zones, and the relative abundances within each zone. For reliable modeling, the density structure must be known. It is shown how the emission-line profiles can be used as a powerful diagnostic of this, as well as of the abundance structure of the ejecta. The variation of the composition with the He core mass is shown to lead to substantial differences in the spectra, especially in the [O I]/[Ca II] emission-line ratio. Also, the degree of convective mixing is important for the result. The late spectrum is thus a good diagnostic of the nucleosynthetic structure of the supernova. At late times, a thermal instability is possible, since fine-structure far-IR lines dominate the cooling. This may trigger molecule and dust formation in the ejecta. The emission from a central pulsar may prevent this from occurring. The model is applied to the observations of the Type Ib SN 1985F. From a nebular analysis, including most of the diagnostic lines available, it is concluded that a white dwarf model cannot be excluded, purely on this basis. However, from calculations of the emission from 4-8 M_sun_ He cores, it is found that a core mass of ~ 8 M_sun_ reproduces both the total and the relative line strengths well, while lower mass cores give a considerably poorer agreement. Thus, the spectrum indicates that the Type Ib supernovae come from stars of ~ 25 M_sun_ and above. The density distribution, as inferred from the line profiles, is, however, considerably more extended than in the hydrodynamical models. This may be a result of instabilities. A macroscopic mixing of clumps from the different burning shells is shown to be the most likely explanation for the lack of a velocity correlation from lines of the different elements. Models based on exploding white dwarfs are shown to be inconsistent with the observations, owing to low absolute line luminosities and to the strong [C I] lines. Publication: The Astrophysical Journal Pub Date: August 1989 DOI: 10.1086/167707 Bibcode: 1989ApJ...343..323F Keywords: Cobalt Isotopes; Emission Spectra; Nuclear Astrophysics; Radioactive Decay; Supernovae; Line Spectra; Monte Carlo Method; Stellar Interiors; Astrophysics; GAMMA RAYS: GENERAL; NUCLEOSYNTHESIS; STARS: INTERIORS; STARS: SUPERNOVAE full text sources ADS | data products NED (12) SIMBAD (7)

In a wall-stabilized cascade arc helium plasma with some traces of SF6 has been generated. On the basis of measured total line intensities emitted from the plasma, the relative line strengths within twelve multiplets of neutral sulfur (SI) have been determined. The studied lines cover the spectral range from 415 nm to 1046 nm. The obtained experimental line strengths are compared with results of recent theoretical data as well as with results of older experiments. In addition the SI line strength data are compared with analogous transitions in the OI spectrum.

Due to the Askaryan effect, radio emissions will be produced when ultra-high-energy (UHE) cosmic rays and neutrinos impact the lunar regolith. Many experiments have been proposed and performed to detect such radio emissions from the lunar regolith. However, none of the Cherenkov radio signals has been detected in these experiments up to now. In order to improve the detectability of the UHE particles, we proposed an experiment to carry out the radio observations of the UHE cosmic rays and neutrinos with two 30 m telescopes for a far longer time than the present experiments. The expected sensitivity for the detection of such UHE particles has been calculated, both for cosmic rays and neutrinos. The results show that a few UHE particle events above 1020 eV could be detected with the expected observation time of several thousand hours.

Astrophysics as a sub-discipline provides both unique opportunities and unique challenges relative to other fields of physics. On the one hand, the scope of astrophysics is literally universal, and we are free to examine the most interesting and exotic phenomena to be found anywhere. On the other hand, our access to the universe is limited to only those bits of information that nature happens to provide to us here on Earth. As astrophysicists, we have no direct control over our subject of study. We cannot conduct experiments to arrange stars in galaxies to our liking. We cannot initiate supernovas at specific times and places just to test our hypotheses. What we can do is to squeeze whatever information possible out of the the tiny particles that have traveled across vast distances to act as messengers to Earth from space.Fortunately, we are getting quite good at building a picture of the universe from the available astrophysical information. Nearly a decade into the millennium, scientists have deployed an impressive collection of sensitive observatories that are especially capable of unlocking the secrets of some of the most persistent astrophysical puzzles. In particular, in the fields of high-energy astrophysics corresponding to gamma-ray, cosmic ray and neutrino detection, we are moving to a new generation of experimental techniques that are dramatically more sensitive than prior efforts. These new instruments have two key properties: (1) increased collection area, which is critical for the low fluxes corresponding to high-energy messenger particles, and (2) precision directional reconstructions which allow observers to trace back the paths of these messengers to the originating astrophysical objects.Furthermore, as observational techniques mature, results from these complementary instruments provide an increasingly comprehensive picture of some of the more elusive astrophysical subjects. Each photon, cosmic ray, and neutrino result reported represents another clue to understanding the nature of high-energy objects both within and outside our galaxy. And yet, along with new understandings, we are also faced with new puzzles.Each of the papers in this focus issue presents the field of high-energy particle astronomy from the perspective of a given instrumental approach, corresponding to the current state-of-the-art for a particular class of messenger particle in a given energy range. For gamma-ray astronomy, we have a excellent report by R Johnson and R Mukherjee on results from space-borne telescopes, first from the Compton Gamma Ray Observatory and then from the recently commissioned Fermi Gamma-Ray Space Telescope. The detailed paper by J Hinton describes a wealth of results from several ground-based gamma-ray telescopes using the atmospheric Cherenokov technique. Gamma-ray results and the prospects from air-shower detectors which can provide all-sky monitoring are very well described in a paper by G Sinnis. Larger plans for the future of ground-based gamma-ray astronomy are summarized in a paper by F Krennrich (in preparation). We also include two papers for 'non-photon' particle detection, a summary of the exciting new results for cosmic ray physics by P Sommers and S Westerhoff and an article by K Hoffman describing the astrophysics and capabilities of truly remarkable, large-volume neutrino detectors. For both cosmic rays and neutrinos, the fields seem to be on the threshold of doing astronomy—that is, associating specific detected particles with particular astrophysical objects.Together, the fully operational space- and ground-based gamma-ray observatories and the new large-area experiments for cosmic ray and neutrino detection represent a new era in astronomy. We can be confident that the field of high-energy particle astronomy will continue to rapidly develop as more exciting results from these instruments are reported in the future. Focus on High Energy Particle Astronomy ContentsGamma ray astronomy with atmospheric Cherenkov telescopes: the future Frank KrennrichGeV telescopes: results and prospects for Fermi R P Johnson and R MukherjeeAir shower detectors in gamma-ray astronomy G SinnisHigh energy neutrino telescopes K D HoffmanGround-based gamma-ray astronomy with Cherenkov telescopes Jim HintonCosmic ray astronomy P Sommers and S Westerhoff

A method is described for calculating the relative absorption oscillator strengths of spectral lines of an element from the gradients of their working curves in emission spectral analysis. A mathematical expression for the gradient of the working curve is derived taking into account the atomic self- absorption of the spectral lines in the cooler region of the discharge and assuming a Doppler broadening line profile for both emission and self-absorption. Local thermal equilibrium is assumed in the absorption region in the arc fringe, and the principle of detailed balance is applied to that region for evaluating the relative population of the lower excited states of the atoms. Correlation between theory and published experimental results for the average gradient of the working curves for 14 lines of Fe I lead to calculation of their relative oscillator strengths as well as to some informations of the average temperatures of the emission and absorption regions. The good agreement between the calculated gf values and those determined by other investigators emphasizes the validity of the assumption of local thermal equilibrium in the arc fringe.

view Abstract Citations (5) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Relative Strengths of Spectral Lines with Mixed Vector Couplings: Dipole Transitions between LS and Other Couplings Escalante, V. ; Gongora-T., A. Abstract The relative strength of spectral lines of electric dipole transitions is calculated in which one of the states is described with the LS coupling scheme and the other is described with the LK, j-K, or j-j coupling scheme. Selection rules for each type of transition are described. As examples, tables are given for transitions of the type 2P nl - 2P m(l-prime) for 1 = l or less, l-prime = 4 or less, and any n and m for the LS-LK and LS-j-K cases. The results can be compared with observed relative intensities of optically thin spectral lines between states with similar quantum numbers. As examples, the results for transitions in the array 3d-4f of N II are compared with observations of planetary nebulae. Publication: The Astrophysical Journal Supplement Series Pub Date: November 1990 DOI: 10.1086/191519 Bibcode: 1990ApJS...74..819E Keywords: Electric Dipoles; Heavy Elements; Line Spectra; Planetary Nebulae; Transition Probabilities; Optical Thickness; Quantum Numbers; Astrophysics; ATOMIC PROCESSES; NEBULAE: PLANETARY; TRANSITION RATES full text sources ADS | data products SIMBAD (2)

A theoretical and experimental investigation has been made of the 2p53p–2p53s transition array in Ne i. Relative line strengths were experimentally measured, using electron-beam excitation of low-pressure neon gas and a single-photon counter, with an accuracy of better than 6%. Relative line strengths were also calculated in various coupling schemes and compared to experimental values. No choices of pure coupling schemes reproduced the experimental data. A recently modified intermediate-coupling calculation by Mehlhorn gives results in good agreement with our experimental values. By normalizing the measured relative line strengths to the experimental lifetimes of Bennett and Kindlmann, absolute A values were obtained which are believed to have an accuracy of better than 10%. The radial factor of the spontaneous dipole transition matrix was determined from the absolute A values and relative line strengths. This radial factor was found to be within 7% of the calculated radial factor using the Coulomb approximation.

We propose a method to investigate the scenario that cosmic relic neutrinos are highly clustered around stars and galaxies, or dark-matter clusters, rather than uniformly distributed in the universe. Such a scenario can be detected or constrained by the interaction of high-energy cosmic ray protons and nuclei with the cosmic neutrinos. There should be an observable signature in the energy spectra of cosmic ray protons and nuclei for a neutrino clustering factor beyond 1013. We provide a relation on the signature onset positions between proton and nuclei spectra, and discuss possible support from existing experiments. It is also suggested that the relative abundance of cosmic ray nuclei may detect or constrain the cosmic neutrinos with smaller clustering.

We present recent observations from the Hubble Space Telescope-Cosmic Origins Spectrograph aimed at characterizing the auroral emission from the extrasolar planet HD 209458b. We obtained medium-resolution (R ∼ 20,000) far-ultraviolet (1150–1700 Å) spectra at both the Phase 0.25 and Phase 0.75 quadrature positions as well as a stellar baseline measurement at secondary eclipse. This analysis includes a catalog of stellar emission lines and a star-subtracted spectrum of the planet. We present an emission model for planetary H2 emission, and compare this model to the planetary spectrum. No unambiguously identifiable atomic or molecular features are detected, and upper limits are presented for auroral/dayglow line strengths. An orbital velocity cross-correlation analysis finds a statistically significant (3.8σ) feature at +15(± 20) km s−1 in the rest frame of the planet, at λ1582 Å. This feature is consistent with emission from H2 B–X (2–9) P(4) (λrest = 1581.11 Å); however, the physical mechanism required to excite this transition is unclear. We compare limits on relative line strengths seen in the exoplanet spectrum with models of ultraviolet fluorescence to constrain the atmospheric column density of neutral hydrogen between the star and the planetary surface. These results support models of short-period extrasolar giant planets with weak magnetic fields and extended atomic atmospheres.

With a high-current wall-stabilized arc, operated in helium with small admixtures of CO2, relative line strengths for some prominent infrared multiplets of neutral carbon have been measured. The results are analyzed in conjunction with previously obtained experimental data in the visible and near infrared region of the spectrum. Our experimental results are compared with those resulting from the Russell-Saunders coupling scheme and with recent sophisticated intermediate coupling calculations. The results of this paper may be helpful for the improvement of atomic structure codes used for line strength calculations. The determined relative line strengths may also be useful in astrophysical applications.

The Fermi orbiter, mapping the entire gamma-ray sky every three hours, monitors the cosmos for high-energy phenomena both fleeting and enduring.

Long-duration observations of Neptune's brightness at two visible wavelengths provide a disk-averaged estimate of its atmospheric aerosol. Brightness variations were previously associated with the 11-year solar cycle, through solar-modulated mechanisms linked with either ultraviolet or galactic cosmic ray (GCR) effects on atmospheric particles. Here, we use a recently extended brightness data set (1972–2014), with physically realistic modelling to show, rather than alternatives, ultraviolet and GCR are likely to be modulating Neptune's atmosphere in combination. The importance of GCR is further supported by the response of Neptune's atmosphere to an intermittent 1.5- to 1.9-year periodicity, which occurred preferentially in GCR (not ultraviolet) during the mid-1980s. This periodicity was detected both at Earth, and in GCR measured by Voyager 2, then near Neptune. A similar coincident variability in Neptune's brightness suggests nucleation onto GCR ions. Both GCR and ultraviolet mechanisms may occur more rapidly than the subsequent atmospheric particle transport.