- ID:
- ivo://CDS.VizieR/J/ApJ/863/119
- Title:
- Cosmic-ray nuclei studies with Voyager, ACE & AMS-02
- Short Name:
- J/ApJ/863/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The acceleration of cosmic-ray particles and their propagation in the Milky Way and the heliosphere tangle with each other, leading to complexity and degeneracy of the modeling of Galactic cosmic rays (GCRs). The recent measurements of the GCR spectra by Voyager-1 from outside of the heliosphere gave the first direct observation of GCRs in the local interstellar (LIS) environment. Together with the high-precision data near the Earth taken by the Advanced Composition Explorer (ACE) and AMS-02, we derive the LIS spectra of helium, lithium, beryllium, boron, carbon, and oxygen nuclei from a few MeV/n to TeV/n, using a non-parameterization method. These LIS spectra are helpful in further studying the injection and propagation parameters of GCRs. The nearly 20 years of data recorded by ACE are used to determine the solar modulation parameters over solar cycles 23 and 24, based on the force-field approximation. We find general agreements of the modulation potential with the results inferred from neutron monitors and other cosmic-ray data.
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- ID:
- ivo://CDS.VizieR/J/ApJ/854/183
- Title:
- Cosmic-ray nucleosynthesis of p-nuclei
- Short Name:
- J/ApJ/854/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the cosmic-ray nucleosynthesis (CRN) of proton-rich stable nuclides (p-nuclides). We calculate the cosmic-ray (CR) energy spectra of heavy nuclides with mass number A=[74,209], taking into account the detailed nuclear spallation, decay, energy loss, and escape from the Galaxy during the CR propagation. We adopt the latest semiempirical formula SPACS (Schmitt+ 2014PhRvC..90f4605S) for the spallation cross sections and the latest data on nuclear decay. Effective electron-capture decay rates are calculated using the proper cross sections for recombination and ionization in the whole CR energy region. Calculated CR spectral shapes vary for different nuclides. Abundances of proton-rich unstable nuclides increase in CRs with increasing energy relative to those of other nuclides. Yields of the primary and secondary spallation processes and differential yields from respective seed nuclides are calculated. We find that the CR energy region of <=O(100)MeV/nucleon predominantly contributes to the total yields. The atomic cross sections in the low-energy range adopted in this study are then necessary. Effects of CRN on the Galactic chemical evolution of p-nuclides are calculated. Important seed nuclides are identified for respective p-nuclides. The contribution of CRN is significant for ^180m^Ta, accounting for about 20% of the solar abundance. About 87% of the ^180m^Ta CRN yield can be attributed to the primary process. The most important production routes are reactions of ^181^Ta, ^180^Hf, and ^182^W. CRN yields of other p-nuclides are typically about O(10^-4^-10^-2^) of solar abundances.
- ID:
- ivo://CDS.VizieR/J/A+A/310/893
- Title:
- C_2_ Phillips and CN Red bands in HD 56126
- Short Name:
- J/A+A/310/893
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the detection of molecular absorption lines in the optical spectrum of the post-AGB star HD 56126. The C_2_ Phillips A^1^{PI}_u_-X^1^{SIGMA}^+^_g_(1,0), (2,0), and (3,0); Swan d^3^{PI}_g_-a^3^{PI}_u_(0,0) and (1,0); and CN Red system A^2^{PI}-X^2^{SIGMA}^+^ (1,0), (2,0), (3,0), and (4,0) bands have been identified. From the identification of the molecular bands we find an expansion velocity of 8.5+/-0.6km/s independent of excitation condition or molecular specie. On the basis of the expansion velocity, rotational temperatures, and molecular column densities we argue that the line-forming region is the AGB remnant. This is in agreement with the expansion velocity derived from the CO lines. We find column densities of logN_C_2__=15.3+/-0.3cm^-2^ and logN_CN_=15.5+/-0.3cm^-2^, and rotational temperatures of T_rot_=242+/-20K and T_rot_=24+/-5K respectively for C_2_ and CN. By studying molecular line absorption in optical spectra of post-AGB stars we have found a new tracer of the AGB remnant. From comparison with the results of CO and IR observations it is possible to obtain information on non-spherical behavior of the AGB remnant. Using different molecules with different excitation conditions it should be possible to study the AGB remnant as a function of the distance to the star, and thus as a function of the evolutionary status of the star on the AGB.
- ID:
- ivo://CDS.VizieR/J/ApJ/667/1267
- Title:
- CrI transition probabilities
- Short Name:
- J/ApJ/667/1267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Branching fraction measurements from Fourier transform spectra in conjunction with published radiative lifetimes are used to determine transition probabilities for 263 lines of neutral chromium.
- ID:
- ivo://CDS.VizieR/J/ApJ/833/196
- Title:
- Cross sections produced by ^3^He reactions
- Short Name:
- J/ApJ/833/196
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ^3^He abundance in impulsive solar energetic particle (SEP) events is enhanced up to several orders of magnitude compared to its photospheric value of [^3^He]/[^4^He] = 1-3 x 10^-4^. Interplanetary magnetic field and timing observations suggest that these events are related to solar flares. Observations of ^3^He in flare-accelerated ions would clarify the relationship between these two phenomena. Energetic ^3^He interactions in the solar atmosphere produce gamma-ray nuclear-deexcitation lines, both lines that are also produced by protons and {alpha} particles and lines that are essentially unique to ^3^He. Gamma-ray spectroscopy can, therefore, reveal enhanced levels of accelerated ^3^He. In this paper, we identify all significant deexcitation lines produced by ^3^He interactions in the solar atmosphere. We evaluate their production cross sections and incorporate them into our nuclear deexcitation-line code. We find that enhanced ^3^He can affect the entire gamma-ray spectrum. We identify gamma-ray line features for which the yield ratios depend dramatically on the ^3^He abundance. We determine the accelerated ^3^He/{alpha} ratio by comparing these ratios with flux ratios measured previously from the gamma-ray spectrum obtained by summing the 19 strongest flares observed with the Solar Maximum Mission Gamma-Ray Spectrometer. All six flux ratios investigated show enhanced ^3^He, confirming earlier suggestions. The ^3^He/{alpha} weighted mean of these new measurements ranges from 0.05 to 0.3 (depending on the assumed accelerated {alpha}/proton ratio) and has a <1 x 10^-3^ probability of being consistent with the photospheric value. With the improved code, we can now exploit the full potential of gamma-ray spectroscopy to establish the relationship between flare-accelerated ions and ^3^He-rich SEPs.
- ID:
- ivo://CDS.VizieR/J/A+A/506/1501
- Title:
- CrVIII radiative and excitation rates
- Short Name:
- J/A+A/506/1501
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we report on calculations of energy levels, radiative rates, oscillator strengths, line strengths, and effective collision strengths for transitions among the lowest 362 levels of the (1s^2^2s^2^2p^6^) 3s^2^3p^5^, 3s3p^6^, 3s^2^3p^4^3d, 3s3p^5^3d, 3s^2^3p^3^3d^2^, 3s3p^4^3d^2^, 3p^6^3d, and 3s^2^3p^4^4l configurations of Cr VIII.
- ID:
- ivo://CDS.VizieR/J/A+A/640/A77
- Title:
- Crystallization of a neutron star inner crust
- Short Name:
- J/A+A/640/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The possible presence of amorphous and heterogeneous phases in the inner crust of a neutron star is expected to reduce the electrical conductivity of the crust, with potentially important consequences on the magneto-thermal evolution of the star. In cooling simulations, the disorder is quantified by an impurity parameter which is often taken as a free parameter. We aim to give a quantitative prediction of the impurity parameter as a function of the density in the crust, performing microscopic calculations including up-to-date microphysics of the crust. A multi-component approach is developed at finite temperature using a compressible liquid drop description of the ions with an improved energy functional based on recent microscopic nuclear models and optimized on extended Thomas-Fermi calculations. Thermodynamic consistency is ensured by adding a rearrangement term and deviations from the linear mixing rule are included in the liquid phase. The impurity parameter is consistently calculated at the crystallization temperature as determined in the one-component plasma approximation for the different functionals. Our calculations show that at the crystallization temperature the composition of the inner crust is dominated by nuclei with charge number around Z~40, while the range of the Z distribution varies from about 20 near the neutron drip to about 40 closer to the crust-core transition. This reflects on the behavior of the impurity parameter that monotonically increases with density up to around 40 in the deeper regions of the inner crust. Our study shows that the contribution of impurities is non-negligible, thus potentially having an impact on the transport properties in the neutron-star crust. The obtained values of the impurity parameter represent a lower limit; larger values are expected in the presence of non-spherical geometries and/or fast cooling dynamics.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A149
- Title:
- Crystallization of neutron star outer crust
- Short Name:
- J/A+A/633/A149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interior of a neutron star is usually assumed to be made of cold catalyzed matter. However, the outer layers are unlikely to remain in full thermodynamic equilibrium during the formation of the star and its subsequent cooling, especially after crystallization occurs. We study the cooling and the equilibrium composition of the outer layers of a non-accreting neutron star down to crystallization. Here the impurity parameter, generally taken as a free parameter in cooling simulations, is calculated self-consistently using a microscopic nuclear model for which a unified equation of state has recently been determined. We follow the evolution of the nuclear distributions of the multi-component Coulomb liquid plasma fully self-consistently, adapting a general formalism originally developed for the description of supernova cores. We calculate the impurity parameter at the crystallization temperature as determined in the one-component plasma approximation. Our analysis shows that the sharp changes in composition obtained in the one-component plasma approximation are smoothed out when a full nuclear distribution is allowed. The Coulomb coupling parameter at melting is found to be reasonably close to the canonical value of 175, except for specific values of the pressure for which supercooling occurs in the one-component plasma approximation. Our multi-component treatment leads to non-monotonic variations of the impurity parameter with pressure. Its values can change by several orders of magnitude reaching about 50, suggesting that the crust may be composed of an alternation of pure (highly conductive) and impure (highly resistive) layers. The results presented here complement the recent unified equation of state obtained within the same nuclear model. Our self-consistent approach to hot dense multi-component plasma shows that the presence of impurities in the outer crust of a neutron star is non- negligible and may have a sizeable impact on transport properties. In turn, this may have important implications not only for the cooling of neutron stars, but also for their magneto-rotational evolution.
- ID:
- ivo://CDS.VizieR/J/ApJS/233/11
- Title:
- Cyanoacetylene (HC_3_N) infrared spectrum
- Short Name:
- J/ApJS/233/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HC_3_N is a ubiquitous molecule in interstellar environments, from external galaxies to Galactic interstellar clouds, star-forming regions, and planetary atmospheres. Observations of its rotational and vibrational transitions provide important information on the physical and chemical structures of the above environments. We present the most complete global analysis of the spectroscopic data of HC_3_N. We recorded the high-resolution infrared spectrum from 450 to 1350cm^-1^, a region dominated by the intense {nu}_5_ and {nu}_6_ fundamental bands, located at 660 and 500cm^-1^, respectively, and their associated hot bands. Pure rotational transitions in the ground and vibrationally excited states were recorded in the millimeter and submillimeter regions in order to extend the frequency range so far considered in previous investigations. All of the transitions from the literature and from this work involving energy levels lower than 1000cm^-1^ were fitted together to an effective Hamiltonian. Because of the presence of various anharmonic resonances, the Hamiltonian includes a number of interaction constants, in addition to the conventional rotational and vibrational l-type resonance terms. The data set contains about 3400 ro-vibrational lines of 13 bands and some 1500 pure rotational lines belonging to 12 vibrational states. More than 120 spectroscopic constants were determined directly from the fit, without any assumption deduced from theoretical calculations or comparisons with similar molecules. An extensive list of highly accurate rest frequencies was produced to assist astronomical searches and data interpretation. These improved data enabled a refined analysis of the ALMA observations toward Sgr B2(N2).
- ID:
- ivo://CDS.VizieR/J/A+A/638/A3
- Title:
- Cyanoketene (NC-CH=C=O) mm wave spectroscopy
- Short Name:
- J/A+A/638/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ketene was detected in the interstellar medium (ISM) in 1977. Until now, only one derivative, the ketenyl radical, has been observed in this medium. Due to its large dipole moment value, cynaoketene is one of the best candidates for possible ketene derivative detection. Aims.To date, the measurements of the rotational spectra have been limited to 60GHz. The extrapolation of the prediction in the millimeter wave domain is inaccurate and does not permit an unambiguous detection. The rotational spectra were re-investigated up to 330GHz. Using the new prediction cyanoketene was sought after in a variety of astronomical sources: NGS 63341, SgrB2(N), and ASAI sources. A total of 1594 transitions were newly assigned and fitted together with those from previous studies, reaching quantum numbers up to J=82 and K_a_=24. Watson's asymmetric top Hamiltonian in the I^r^ representation was used for the analysis; both reductions A and S were tested. Logically, the S reduction gave the best results confirming that the molecule is very close to the prolate limit. Cynaoketene was not found in ISM; upper limits to the column density were derived in each source.
