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We study the properties and mass distributions of ultramagnetized nuclei produced as a result of heavy ion collisions, inside magnetar crust, explosions of type II supernovas, and the merging of neutron stars. For magnetic field strengths ranging from 0.1 to 10 TT, the Zeeman effect results in a linear nuclear magnetic response that can be described using magnetic susceptibility. Binding energies rise correspondingly for nuclei with open shells and fall for nuclei with closed shells. A noticeable increase in the generation of corresponding explosion nucleosynthetic products with antimagic numbers is predicted for nuclei belonging to the iron group and the r-process. The magnetic enhancement of 44Ti isotopes is consistent with results from observations and testifying to the substantial increase in the share of the main titanium isotope (48Ti) in the Galaxy’s chemical composition. An increased number of nuclides with low mass numbers is predicted in the peak of the r-process as a result of magnetic effects.

The properties and mass distribution of the ultramagnetized atomic nuclei which arise in heavy-ion collisions and magnetar crusts, during Type II supernova explosions and neutron star mergers are analyzed. For the magnetic field strength range of 0.1&ndash, 10 teratesla, the Zeeman effect leads to a linear nuclear magnetic response that can be described in terms of magnetic susceptibility. Binding energies increase for open shell and decrease for closed shell nuclei. A noticeable enhancement in theyield of corresponding explosive nucleosynthesis products with antimagic numbers is predicted for iron group and r-process nuclei. Magnetic enrichment in a sampleof 44Ti corroborate theobservational results and imply a significant increase in the quantity of the main titanium isotope, 48Ti, in the chemical composition of galaxies. The enhancement of small mass number nuclides in the r-process peak may be due to magnetic effects.

Data on cosmic ray muon bundles accumulated at the NEVOD-DECOR complex over the period from May 2012 to December 2018 have been analyzed. Local muon density spectra at various zenith angles have been reconstructed and compared with CORSIKA-based simulations. At large zenith angles and high muon multiplicities corresponding to primary particle energies more than about 3 × 1017 eV an excess of multi-muon events compared to simulations is clearly seen. Present data are compatible with the expectation for recent LHC-adjusted hadron interaction models only under assumption of extremely heavy (iron group nuclei) primary composition. The assumption of a heavy composition is however in contradiction with other EAS observables, such as maximum depth and its fluctuations.

The research on supernovae explosions is one of the most exciting fields in astrophysics. Recent studies show that the electron capture and beta decay play key roles in supernovae explosions. In this paper, the half-lives of some iron group nuclei by β − -decay are investigated due to shell effect, pair effect, and the changes of the decay energy. We also discuss the influence of strong electron screening (SES) on the electron energy, beta decay threshold energy, and the antineutrino energy loss rates (AELR) in β − decay. The AELR increases, and the screening enhancement factor can get to 4.684 in SES due to Q-value correction, shell and pairing effect. The AELR can be suppressed at lower density and higher temperature environment (e.g., 0.1 30). The screening enhancement factor decreases about 14.10% (e.g., for 56Ni).

Accurate atomic data for line wavelengths, energy levels, line broadening such as hyperfine structure and isotope structure, and f-values, particularly for the line rich iron group elements, are needed for stellar astrophysics applications, and examples of recent measurements are given. These atomic data are essential for determination of elemental abundances in astronomical objects. With modern facilities, telescopes and spectrographs, access to underexplored regions (IR, UV, VUV), and improved stellar atmosphere models (3D, NLTE), and extremely large datasets, astronomers are tackling problems ranging from studying Galactic chemical evolution, to low mass stars and exoplanets. Such advances require improved accuracy and completeness of the atomic database for analyses of astrophysical spectra.

We summarize recent work at the National Institute of Standards and Technology and Imperial College London on wavelengths, hyperfine structure, energy levels, and analysis of singly ionized iron-group elements of astrophysical interest.

High-resolution spectroscopic observations of the eclipsing binary system RR Lyn were made using the 1.8 m telescope at the Bohuynsan Optical Astronomical Observatory in Korea. The spectral resolving power was R = 82,000, with a signal to noise ratio of S/N > 150. We found the effective temperatures and surface gravities of the primary and secondary components to be equal to Teff = 7,920 & 7,210 K and log(g) = 3.80 & 4.16, respectively. The abundances of 34 and 17 different chemical elements were found in the atmospheric components. Correlations between the derived abundances with condensation temperatures and the second ionization potentials of these elements are discussed. The primary component is a typical metallic line star with the abundances of light and iron group elements close to solar values, while elements with atomic numbers Z > 30 are overabundant by 0.5–1.5 dex with respect to solar values. The secondary component is a λ Boo type star. In this type of stars, CNO abundances are close to solar values, while the abundance pattern shows a negative correlation with condensation temperatures.

We have developed a method for determining elemental Fe-group abundances in planetary nebulae using an infrared emission line of Zn, the least refractory Fe-group species. Many planetary nebulae, particularly those of the Milky Way’s thick disk and bulge, display subsolar [Fe/H] (as inferred from Zn) although their abundances of α elements such as O, S, and Ar are nearly solar. We discuss the implications for determining enhancements of species synthesized by the progenitor star during the AGB (e.g.,s-process products), and for galactic chemical evolution in view of the metallicity dependence of AGB nucleosynthetic yields.

The explosive death of a star as a supernova is one of the most dramatic events in the Universe. Supernovae have an outsized impact on many areas of astrophysics: they are major contributors to the chemical enrichment of the cosmos and significantly influence the formation of subsequent generations of stars and the evolution of galaxies. Here we review the observational properties of thermonuclear supernovae, exploding white dwarf stars resulting from the stellar evolution of low-mass stars in close binary systems. The best known objects in this class are type Ia supernovae (SN Ia), astrophysically important in their application as standardisable candles to measure cosmological distances and the primary source of iron group elements in the Universe. Surprisingly, given their prominent role, SN Ia progenitor systems and explosion mechanisms are not fully understood; the observations we describe here provide constraints on models, not always in consistent ways. Recent advances in supernova discovery and follow-up have shown that the class of thermonuclear supernovae includes more than just SN Ia, and we characterise that diversity in this review., Comment: Authors' version of invited Review Article published as part of a Supernova Focus issue in Nature Astronomy; 14 pages, 8 figures

The direct measurement of the \(^{13}{\hbox {C}}\)(\(\alpha \),n)\(^{16}{\hbox {O}}\) nuclear reaction down to its Gamow window is essential to the complex understanding of the astrophysical s-process, which is responsible for the production of about half of the heavier elements above the iron group. The combination of a high efficiency experimental setup and the extremely low environmental background is required to measure cross sections of the order of picobarns. This paper presents the main features of the LUNA neutron detector array dedicated to the direct investigation of the \(^{13}{\hbox {C}}\)(\(\alpha \),n)\(^{16}{\hbox {O}}\) nuclear reaction in the Underground Laboratory of LNGS.

We present results from general relativistic calculations of nuclear ignition in white dwarf stars triggered by near encounters with rotating intermediate mass black holes with different spin and alignment parameters. These encounters create thermonuclear environments characteristic of Type Ia supernovae capable of producing both calcium and iron group elements in arbitrary ratios, depending primarily on the proximity of the interaction which acts as a strong moderator of nucleosynthesis. We explore the effects of black hole spin and spin-orbital alignment on burn product synthesis to determine whether they might also be capable of moderating reactive flows. When normalized to equivalent impact penetration, accounting for frame dragging corrections, the influence of spin is weak, no more than 25% as measured by nuclear energy release and mass of burn products, even for near maximally rotating black holes. Stars on prograde trajectories approach closer to the black hole and produce significantly more unbound debris and iron group elements than is possible by encounters with nonrotating black holes or by retrograde orbits, at more than 50% mass conversion efficiency. The debris contains several radioisotopes, most notably Ni56, made in amounts that produce sub-luminous (but still observable) light curves compared to branch-normal SNe Ia., Comment: 20 pages, 7 figures, submitted to ApJ

We present optical observations of a SN 2002cx-like supernova SN 2013en in UGC 11369, spanning from a phase near maximum light (t= +1 d) to t= +60 d with respect to the R-band maximum. Adopting a distance modulus of mu=34.11 +/- 0.15 mag and a total extinction (host galaxy+Milky Way) of $A_V \sim1.5$ mag, we found that SN 2013en peaked at $M(R)\sim -18.6$ mag, which is underluminous compared to the normal SNe Ia. The near maximum spectra show lines of Si II, Fe II, Fe III, Cr II, Ca II and other intermediate-mass and iron group elements which all have lower expansion velocities (i.e., ~ 6000 km/s). The photometric and spectroscopic evolution of SN 2013en is remarkably similar to those of SN 2002cx and SN 2005hk, suggesting that they are likely to be generated from a similar progenitor scenario or explosion mechanism., 8 pages, 8 figures, 3 tables, accepted for publication in MNRAS

We present near infrared (NIR) spectroscopy of the nearby supernova 2014J obtained $\sim$450 d after explosion. We detect the [Ni II] 1.939 $\mu$m line in the spectra indicating the presence of stable $^{58}$Ni in the ejecta. The stable nickel is not centrally concentrated but rather distributed as the iron. The spectra are dominated by forbidden [Fe II] and [Co II] lines. We use lines, in the NIR spectra, arising from the same upper energy levels to place constraints on the extinction from host galaxy dust. We find that that our data are in agreement with the high $A_V$ and low $R_V$ found in earlier studies from data near maximum light. Using a $^{56}$Ni mass prior from near maximum light $\gamma$-ray observations, we find $\sim$0.05 M$_\odot$ of stable nickel to be present in the ejecta. We find that the iron group features are redshifted from the host galaxy rest frame by $\sim$600 km s$^{-1}$., Comment: 6 pages, 4 figures, submitted to A&A

Synopsis Accurate atomic data of the iron group elements are of major importance in astrophysics. In the present work energy spectrum calculations are performed for 332 lowest states for Ni II ion. Energy levels are compared with NIST database recommended values. All computations were done using the general-purpose relativistic atomic structure package GRASP2018.

Based on the work of Wang et al. (Chin. Phys. Lett. 29:049701, 2012), we re-investigated electron capture on iron group nuclei in the outer crust of magnetars and studied magnetar evolution. Effects of ultra-strong magnetic field on electron capture rates for 57Co have been analyzed in the nuclear shell model and under the Landau-level-quantization approximation, and the electron capture rates and the neutrino energy loss rates on iron group nuclei in the outer crust of magnetar have been calculated. The results show that electron capture rates on 57Co are increase greatly in the ultra-strong magnetic field, and above 3 orders of magnitude generally; and the neutrino energy loss rates by electron capture on iron group nuclei increase above 3 orders of magnitude in the range from B=4.414×1013 G to B=4.414×1015 G. These conclusions play an important role in future studying the evolution of magnetar. Furthermore, we modify the expressions of the electron chemical potential (Fermi energy) and phase space factor by introducing Dirac δ-function, and select appropriate parameters of temperature T, magnetic field B and matter density ρ in the our crust, thus our results will be reliable than those of Wang et al.

Using the theory of relativity in superstrong magnetic fields (SMFs) and nuclear shell model, we carry out estimation for electron capture (EC) rates on iron group nuclei in SMFs. The rates of change of electronic abundance (RCEA) due to EC are also investigated in SMFs. It is concluded that the EC rates of most iron group nuclides are increased greatly by SMFs and even exceeded by nine orders of magnitude. On the other hand, RCEA is influenced greatly by SMFs and even reduced by more than eight orders of magnitude in the EC reaction.We also compare our results with those of Fuller et al.(FFN) and Aufderheide et al.(AUFD) in the case with and without SMFs. The results show that our results are in good agreement with AUFD's, but the rates of FFN's are about close to one order of magnitude bigger than ours in the case without SMFs. On the contrary, our calculated rates for most nuclides in SMFs are increased and even exceeded as much as for nine and eight orders of magnitude of compared to FFN's and AUFD's results, which is in the case without SMFs, respectively., 8 pages, 13 figures, accepted by MNRAS

β Cephei and SPB stars are pulsating stars for which the excitation of modes by the κ mechanism, due to the iron-group opacity peak, seems puzzling. We have first investigated the origins of the differences noticed between OP and OPAL iron and nickel opacity calculations (up to a factor 2), a fact which complicates the interpretation. To accomplish this task, new well-qualified calculations (SCO-RCG, HULLAC and ATOMIC) have been performed and compared to values of these tables, and most of the differences are now well understood. Next, we have exploited a dedicated experiment on chromium, iron and nickel, conducted at the LULI 2000 facilities. We found that, in the case of iron, detailed calculations (OP, ATOMIC and HULLAC) show good agreement, contrary to all of the non-detailed calculations. However, in the case of nickel, OP calculations show large discrepancies with the experiments but also with other codes. Thus, the opacity tables need to be revised in the thermodynamical conditions corresponding to the peak of the iron group. Consequently we study the evolution of this iron peak with changes in stellar mass, age, and metallicity to determine the relevant region where these tables should be revised.

The abundances of two chemical elements of the iron group, viz., Cr and Ti, were determined by their high-resolution spectra for 22 A, F, and G supergiants in the solar neighborhood (within 700 pc). The titanium and chromium abundances were obtained using the Cr II and Ti II lines. The average chromium abundance of logɛ(Cr) = 5.70 ± 0.13 within the error limit corresponds to the solar abundance of logɛ⊙(Cr) = 5.64. The average titanium abundance of logɛ(Ti) = 4.89 ± 0.10 within the error limit is very close to the solar abundance of logɛ⊙(Ti) = 4.95. The average Cr and Ti abundances may be indicative of the fact that the average metallicity of young closely located stars is identical to that of the Sun.

3rd International Conference on Theoretical and Experimental Studies in Nuclear Applications and Technology (TESNAT) -- MAY 10-12, 2017 -- Adana, TURKEY WOS: 000426429000028 Iron group elements (Sc, Mn, Fe, Co, Ni) are especially very important because structural material selection in design of fusion-fission reactors is very crucial. Obtained results from the nuclear reactions using structural materials can be used developing for these structural materials some isotopes. For this reason, in this study the cross sections of Sc-45(alpha, n) V-48, Mn-55(alpha, n) Co-58, Fe-54(alpha, n) Ni-57, Co-59(alpha, n) Cu-62, Ni-62(alpha, n) Zn-65 reactions have been calculated at 5-20 MeV energy ranges by using TALYS 1.8 and NON-SMOKER codes. Obtained results were compared experimental data from EXFOR database.

The paper considers the chains of successive electron capture reactions by nuclei of the iron group which take place in the crystal structures of neutron star envelopes. It is shown that as a result of such reactions the daughter nuclei in excited states accumulate within certain layers of neutron star crusts. The phonon model of interactions is proposed between the excited nuclei in the crystalline structure, as well as formation of highly excited nuclear states which emit neutrons and higher energy photons., 11 pages, 1 figure

Radiative transfer studies of Type Ia supernovae (SNe Ia) hold the promise of constraining both the time-dependent density profile of the SN ejecta and its stratification by element abundance which, in turn, may discriminate between different explosion mechanisms and progenitor classes. Here we present a detailed analysis of Hubble Space Telescope ultraviolet (UV) and ground-based optical spectra and light curves of the SN Ia SN 2010jn (PTF10ygu). SN 2010jn was discovered by the Palomar Transient Factory (PTF) 15 days before maximum light, allowing us to secure a time-series of four UV spectra at epochs from -11 to +5 days relative to B-band maximum. The photospheric UV spectra are excellent diagnostics of the iron-group abundances in the outer layers of the ejecta, particularly those at very early times. Using the method of 'Abundance Tomography' we have derived iron-group abundances in SN 2010jn with a precision better than in any previously studied SN Ia. Optimum fits to the data can be obtained if burned material is present even at high velocities, including significant mass fractions of iron-group elements. This is consistent with the slow decline rate (or high 'stretch') of the light curve of SN 2010jn, and consistent with the results of delayed-detonation models. Early-phase UV spectra and detailed time-dependent series of further SNe Ia offer a promising probe of the nature of the SN Ia mechanism., Comment: 17 pages, 9 figures (v3: several small updates to content including models; v2: metadata fixed), MNRAS, in press

We report here the first successful detection of highly relativistic cosmic ray iron group nuclei in the new type of solid state track detector, CR-39 (Allyl diglycol carbonate), in a stack composed of these plastics, nuclear emulsions and other types of plastic detectors, which was exposed in a balloon flight from Hyderabad, India, at 6 mb residual atmosphere for 8 h. The high value of the vertical geomagnetic cut-off rigidity of 16.7 GV ensured the relativistic nature of the particles and these were identified as Fe-group nuclei from the measurements in adjacent sheets of nuclear emulsion. Very well-defined etched cones were observed in the CR-39 plastics after 48 h etch in 6.25 N NaOH at 70 °C, at the locations corresponding to Fe-group nuclei tracks in the nuclear emulsions. The track etch rate (Vt) for relativistic (≥ GeV/nucleon) Fe-group nuclei was measured as 3.5 ± 1.3 μm/h and the bulk etch rate (Vg) as 1.5 ± 0.6 μm/h. The normalised track etch rate, (Vt/Vg) - 1, is compared with the data obtained at lower energies by other workers and the results are found to be consistent. The charge detection threshold for Cr-39 is obtained as Z≈20 for |β {reversed tilde equals} 1. © 1979.

The chemical abundances of the Ba stars are excellent information for setting constraints on models of s-processes nucleosynthesis. In this work, we adopt a new analysis approach to determine the relative contributions from individual neutron-capture processes to the elemental abundances of Ba stars. We find that the production of s-process elements should accompany by the production of Cu and Zn, the calculated results on Cu and Zn abundances are in quite good agreement with observed data. The observed [Cu, Zn/Fe]–[s/Fe] correlations of Ba stars can be explained by binary scenario in which Ba stars formed.

Direct evidence of the presence of 44Ti and content of the isotope in the supernova remnant Cassiopeia A are obtained from the analysis of gamma-ray spectrum of the remnant. A significant excess of observational 44Ti volume on predictions of supernova models can be explained as the magnetization effect in the process of explosive nucleosynthesis. The formation of chemical elements is considered accounting for superstrong magnetic fields predicted for supernovae and neutron stars. Using the arguments of nuclear statistical equilibrium, a significant effect of magnetic field on the nuclear shell energy is demonstrated. The magnetic shift of the most tightly “bound” nuclei from the transition metals of iron series to titanium leads to an exponential increase in the portion of 44Ti and, accordingly to a significant excess of the yield of these products of nucleosynthesis.

The B-type pulsators known as \beta Cephei and Slowly Pulsating B (SPB) stars present pulsations driven by the \kappa mechanism, which operates thanks to an opacity bump due to the iron group elements. In low-metallicity environments such as the Magellanic Clouds, \beta Cep and SPB pulsations are not expected. Nevertheless, recent observations show evidence for the presence of B-type pulsator candidates in both galaxies. We seek an explanation for the excitation of \beta Cep and SPB modes in those galaxies by examining basic input physics in stellar modelling: i) the specific metal mixture of B-type stars in the Magellanic Clouds; ii) the role of a potential underestimation of stellar opacities. We first derive the present-day chemical mixtures of B-type stars in the Magellanic Clouds. Then, we compute stellar models for that metal mixture and perform a non-adiabatic analysis of these models. In a second approach, we simulate parametric enhancements of stellar opacities due to different iron group elements. We then study their effects in models of B stars and their stability. We find that adopting a representative chemical mixture of B stars in the Small Magellanic Cloud cannot explain the presence of B-type pulsators there. An increase of the opacity in the region of the iron-group bump could drive B-type pulsations, but only if this increase occurs at the temperature corresponding to the maximum contribution of Ni to this opacity bump. We recommend an accurate computation of Ni opacity to understand B-type pulsators in the Small Magellanic Cloud, as well as the frequency domain observed in some Galactic hybrid \beta Cep-SPB stars.

New three-body resonances appeared in the neutron scattering on two nuclei fixed in nodes of overdense crystalline lattice have been calculated for the iron group isotopes. These resonances are strongly dependent on the lattice parameters and characteristics of two-body resonances in neutron–nucleus subsystems. The effective forces created by the neutron resonance rescatterings supplement the Coulomb forces between nuclei of the crystalline lattice. These effective resonance interactions occur only at certain distances between nuclei and are accompanied by gamma radiation.

We present an overview of current needs for accurate laboratory atomic transition probabilities (log(gf)) for astrophysical applications, particularly for iron group element spectra in the IR, optical, UV, and VUV spectral regions. Examples are given of our recent measurements, undertaken using the combination of high-resolution Fourier transform spectrometry and time-resolved laser-induced fluorescence. Laboratory measured log(gf) values are particularly important for the determination of elemental abundances in astrophysical objects. Advances in astronomical instrumentation, particularly access to underexplored regions (IR, vacuum UV,VUV), require improved accuracy and completeness of the atomic database for meaningful analyses of astrophysical spectra.

Using coadded spectrograms taken with the Coude Echelle Spectrograph (CES) of the 1.50-m Russian-Turkish Telescope of the TUBITAK National Observatory (TUG) near Antalya in Turkey, elemental abundance analyses of three HgMn stars 11 Per, HR 2801, and ν Cnc were performed. Comparisons are made with spectra obtained with the long camera of the Dominion Astrophysical Observatory (DAO) coude spectrograph and its SITe4 CCD. The CES equivalent widths are about 12% larger than that for the DAO long camera. Our first results from TUG data/spectra show that all three stars exhibit the Hg II λ3984 line and somewhat diverse abundance patterns. 11 Per tends to have underabundant light elements with underabundant and overabundant Fe-peak elements. HR 2801 has mostly underabundant elements, with a few elements having solar abundances while N and Mn are overabundant. The coolest star ν Cnc has light elements having mostly solar abundances, overabundant iron group abundances, and very overabundant SrYZr and Ba. Comparisons with the abundance patterns of other HgMn stars show that they have a wide diversity of abundance patterns (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The main atmospheric parameters and abundances of the iron group elements (vanadium, chromium, iron, cobalt and nickel) are determined for 62 red giant "clump" stars revealed in the Galactic field by the Hipparcos orbiting observatory. The stars form a homogeneous sample with the mean value of temperature T=4750 +- 160K, of surface gravity log g = 2.41 +- 0.26 and the mean value of metallicity [Fe/H] = -0.04 +- 0.15 dex. A Gaussian fit to the [Fe/H] distribution produces the mean [Fe/H] = -0.01 dex and dispersion of [Fe/H] = 0.08 dex. The near-solar metallicity and small dispersion of [Fe/H] of clump stars of the Galaxy obtained in this work confirm the theoretical model of the Hipparcos clump by Girardi & Salaris (2001). This suggests that nearby clump stars are (in the mean) relatively young objects, reflecting mainly the near-solar metallicities developed in the local disk during the last few Gyrs of its history. We find iron group element to iron abundance ratios in clump giants to be close to solar.

Neutron-capture (Z > 30) elements are detected in many very metal-poor halo stars, and so they must have been manufactured by some of the earliest element donors in our Galaxy's history. The bulk amounts of neutron-capture elements with respect to the iron group vary by several orders of magnitude from star to star at low metallicities. Additionally, abundance distributions among these elements are often strikingly different from that of the solar system. Some stars exhibit abundances that must have been made purely in “rapid” neutron-capture events (the r-process), some in “slow” events (the s-process), and some have hybrid mixes. Here we summarize the major observed categories of the neutron-capture abundances in metal-poor stars, and discuss their implications for early Galactic nucleosynthesis.

The electron capture of Gamow-Teller transition on iron group nuclei is investigated in a strong magnetic field at the crusts of neutron stars. The results show that the magnetic field has only a slight effect on the electron capture rates with the range of the magnetic fields (109 ~ 1013 G) on surfaces of most neutron stars, whereas for some magnetars whose range of the magnetic field is 1013 ~ 1018 G, the electron capture rates of most iron group nuclei would be debased greatly and may be even decreased overrun 3 orders of magnitude by the strong magnetic field.

The influences on the neutrino energy loss rates in iron group nuclei at the same density are investigated in the presence of strong electron screening and in the absence of electron screening. The results show that at a temperature of 15 ? 109 K, the neutrino energy loss rates which come from the electron capture process for most iron group nuclei decrease no more than 2 orders of magnitude but for the others (such as 53,55,56,57,58,59,60 Co, 56,59Ni) they can decrease about 3 orders of magnitude due to strong electron screening (SES), whereas, at a temperature of 109K the neutrino energy loss rates of the most iron group nuclei can be diminished greatly due to the SES. For example, 61Fe, 60Fe, and 62Ni the neutrino energy loss rates decrease about 4, 15 and 16 orders of magnitude and for 57Cr, 58Cr, and 60Cr decrease about 18, 12, and 10 orders of magnitude respectively. According to our calculations the neutrino energy loss rates of nuclei 58Mn, 59Mn, 60Mn, and 62Mn may decrease about 13 orders of magnitude at a temperature of 109 K due to the SES.

In this paper electron capture on iron group nuclei in crusts of neutron stars in a strong magnetic field is investigated. The results show that the magnetic fields have only a slight effect on electron capture rates in a range of 108 − 1013G on surfaces of most neutron stars, whereas for some magnetars the magnetic fields range from 1013 to 1018 G. The electron capture rates of most iron group nuclei are greatly decreased, reduced by even four orders of magnitude due to the strong magnetic field.

The neutrino energy loss rates on iron group nuclei by electron capture are calculated in a strong magnetic field at the crusts of Neutron stars. The results show that the magnetic field has only a slight effect on the neutrino energy loss rates in a range of 108–1013 G on surfaces of the most neutron stars. Whereas for some magnetars which range of the magnetic field is 1013–1018 G, the neutrino energy loss rates of the most iron group nuclei would be debased greatly and may be even decreased for 4 orders of magnitude by the strong magnetic field.

We investigate the uncertainty in surface abundances and yields of asymptotic giant branch (AGB) stars. We apply three different mass loss laws to a 1.5 solar mass star of metallicity Z=0.008 at the beginning of the thermally pulsing asymptotic giant branch (TP-AGB) phase. Efficient third dredge-up is found even at very low envelope mass, contrary to previous simulations with other evolution codes. We find that the yield of carbon is uncertain by about 15% and for most other light elements the yield is uncertain at the level of 20-80%. For iron group elements the uncertainty varies from around 30% for the more abundant species to over a factor of two for the less abundant radioactive species, like iron-60. The post-AGB surface abundances for this mass and metallicity are much more uncertain due to the dilution of dredged-up material in differing envelope masses in the later stages of the models. Our results are compared to known planetary nebula (PN) and post-AGB abundances. We find that the models are mostly consistent with observations but we are unable to reproduce observations of some of the isotopes.

Recently radiatively-driven diusion in Cephei stars has been suggested as a possible explanation to account for excitation of the observed oscillation modes of the Cephei stars Eridani and 12 Lacertae. Preliminary results (Bourge and Alecian 2006) show that microscopic diusion of iron could indeed occur in a region situated just above the opacity bump of the iron group elements. This diusion has little inuence on the position of the star in the HR diagram and on the spectrum of low radial order eigenfrequencies. It does, however, increase the number of excited frequencies. We show here that the ratio between the number of p-modes to the number of g-modes could be used as a signature of this diusion process.

We present ultraviolet (UV) and optical photometry and spectra of the 1999aa-like supernova (SN) iPTF14bdn. The UV data were observed using the Swift Ultraviolet/Optical Telescope (UVOT) and constitute the first UV spectral series of a 1999aa-like SN. From the photometry we measure $\Delta m_{15}({\it B})\,=\,0.84 \pm0.05$ mag and blue UV colors at epochs earlier than $-5$ days. The spectra show that the early-time blue colors are the result of less absorption between $2800 - 3200 \,\AA~$ than is present in normal SNe Ia. Using model spectra fits of the data at $-10 $ and $+10 $ days, we identify the origin of this spectral feature to be a temperature effect in which doubly ionized iron group elements create an opacity 'window'. We determine that the detection of high temperatures and large quantities of iron group elements at early epochs imply the mixing of a high Ni mass into the outer layers of the SN ejecta. We also identify the source of the I-band secondary maximum in iPTF14bdn to be the decay of Fe III to Fe II, as is seen in normal SNe Ia., Comment: 10 pages, 11 figures, 4 tables. Accepted to ApJ

We report new measurements of atomic data for the neutral, singly and doubly ionised iron group element spectra for modern astrophysics applications.

We investigate the origin of the most iron-poor stars including SMSS J031300.36-670839.3 with [Fe/H] < -7.52. We compute the change of surface metallicity of stars with the accretion of interstellar matter (ISM) after their birth using the chemical evolution model within the framework of the hierarchical galaxy formation. The predicted metallicity distribution function agrees very well with that observed from extremely metal-poor stars. In particular, the lowest metallicity tail is well reproduced by the Population III stars whose surfaces are polluted with metals through ISM accretion. This suggests that the origin of iron group elements is explained by ISM accretion for the stars with [Fe/H]$\lesssim -5$. The present results give new insights into the nature of the most metal-poor stars and the search for Population III stars with pristine abundances., Accepted for publication in ApJ Letters

We have observed 15 red giant stars in the relatively massive, metal-poor globular cluster NGC 4833 using the Magellan Inamori Kyocera Echelle spectrograph at Magellan. We calculate stellar parameters for each star and perform a standard abundance analysis to derive abundances of 43 species of 39 elements, including 20 elements heavier than the iron group. We derive = -2.25 +/- 0.02 from Fe I lines and = -2.19 +/- 0.013 from Fe II lines. We confirm earlier results that found no internal metallicity spread in NGC 4833, and there are no significant star-to-star abundance dispersions among any elements in the iron group (19, Comment: Accepted for publication in MNRAS. Version 2 adds final publication reference

In the first stage of this work, we perform detailed calculations for the cross sections of the electron capture on nuclei under laboratory conditions. Towards this aim we exploit the advantages of a refined version of the proton-neutron quasi-particle random-phase approximation (pn-QRPA) and carry out state-by-state evaluations of the rates of exclusive processes that lead to any of the accessible transitions within the chosen model space. In the second stage of our present study, we translate the above mentioned $e^-$-capture cross sections to the stellar environment ones by inserting the temperature dependence through a Maxwell-Boltzmann distribution describing the stellar electron gas. As a concrete nuclear target we use the $^{66}Zn$ isotope, which belongs to the iron group nuclei and plays prominent role in stellar nucleosynthesis at core collapse supernovae environment., 23 pages, 4 figures, 7 tables, Article Ref.:Advances in High Energy Physics, Article ID 398796, in press

We present the excitation energies and lifetimes for the 3s3 p3d 4 F 7/2,9/2 levels for five aluminium-like ions of the iron group. Apart from the wavelengths, this also includes the transition probabilities and branching ratios for the electric-dipole allowed (E1) and forbidden (M1, E2, M2) lines into the energetically lower lying levels of the 3s 2 3d ,3 s3 p 2 and 3s3 p3d con

We present extensive NLTE calculations for a semi-empirical solar 1D chromosphere model based on the VAL C model. We report on a significant influence of nitrogen, oxygen, and sulfur on the emergent hydrogen emission with respect to LTE vs. NLTE calculations for these elements. Moreover, we present a model spectrum with 20 light and iron group elements computed in NLTE. We compare this to an observed solar spectrum and to a photospheric model spectrum. We find that the agreement for this model with the data is less good than the original VAL C model especially in the UV. This may imply the need of changes in the chromospheric temperature structure or may point to general problems of static 1D chromospheric models.

The positions of the energy levels of free ions of the iron group V2+, Cr3+, Mn4+, Fe5+, and Co6+, whose ground configuration is 3d3, and Co2+, Ni3+, Cu4+, and Zn5+, whose configuration is 3d7, are interpreted theoretically within the framework of the single-configuration approximation with a Hamiltonian that takes into account real electrostatic, spin-orbit, and spin-spin interactions, as well as electrostatic and spin-orbit interactions correlated by configuration mixing. It is shown that the correct positions of all the energy levels are determined when the Hamiltonian includes the operators of the theory of the nonlinear configuration interaction. The most correct theoretical description of the experimental spectra is obtained by taking into account relativistic interactions and correlation effects of spin-orbit interactions. Semiempirical parameters of the interactions included into the Hamiltonian are found for all the ions.

We apply an ad hoc model for dynamical ignition in three-dimensional numerical simulations of thermonuclear supernovae assuming pure deflagrations. The model makes use of the statistical description of temperature fluctuations in the pre-supernova core proposed by Wunsch & Woosley (2004). Randomness in time is implemented by means of a Poisson process. We are able to vary the explosion energy and nucleosynthesis depending on the free parameter of the model which controls the rapidity of the ignition process. However, beyond a certain threshold, the strength of the explosion saturates and the outcome appears to be robust with respect to number of ignitions. In the most energetic explosions, we find about 0.75 solar masses of iron group elements. Other than in simulations with simultaneous multi-spot ignition, the amount of unburned carbon and oxygen at radial velocities of a few 1000 km/s tends to be reduced for an ever increasing number of ignition events and, accordingly, more pronounced layering results., 7 pages, 6 figures, accepted for publication in Astron. Astrophys.; PDF version with full resolution figures available from http://www.astro.uni-wuerzburg.de/~schmidt/Paper/StochIgnt_AA.pdf

We report the presence of elements beyond the iron group in the atmospheres of the cool DO white dwarfs HD 149499 B and HZ 21. Photospheric lines of germanium (Z = 32), arsenic (33), selenium (34), tin (50), tellurium (52), iodine (53), and perhaps bromine (35) are observed in ultraviolet spectra of HD 149499 B obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE), the Goddard High Resolution Spectrograph (GHRS), and the International Ultraviolet Explorer. Germanium, arsenic, and tellurium are also observed in FUSE and GHRS spectra of HZ 21. Light elements such as carbon, silicon, phosphorus, and sulfur are present in the atmospheres of both stars. Nitrogen is detected in HZ 21 but not in HD 149499 B. We calculated a grid of synthetic spectra covering the range of effective temperatures, surface gravities, and element abundances appropriate for a detailed line profile analysis. The measured mass fractions of elements heavier than iron reveal overabundances ranging from about a factor of 3 to a factor of 1000 relative to the Sun. The heavy-element enrichment in both stars could be the result of slow neutron capture nucleosynthesis, which would have occurred during the asymptotic giant branch phase of their evolution.

We study the formation of antiferromagnetic magnetoelastic domains in easy-plane antiferromagnets of the iron-group dihalides, in which the infinite degeneracy of the spatial orientation of the antiferromagnetic vector in the basal plane is lifted on account of the spontaneous magnetostriction. In these crystals the domains differ from each other not only by the direction of the antiferromagnetic vector L in them but also by the related directions of the principal axes of the spontaneous magneostrictive strain. The system of antiferromagnetic domains turns out to be identical to the system of elastic domains. It is shown that the processes of magnetization and the induced striction in a magnetic field in the multidomain antiferromagnetic state are interconnected. Data on the field dependence of the induced magnetostriction in the multidomain state of the easy-plane antiferromagnets CoCl2 and NiCl2 are presented and analyzed. It is shown that although the magnetostriction in the cycles of imposition and re...

This work presents the abundance patterns of three barium dwarf candidates, HD 8270, HD 13551, and HD 22589, based on high-resolution optical spectra. This work also reports the spectroscopic stellar parameters, temperature, and microturbulent velocity, as well as the stellar surface gravity from a solution of excitation and ionization equilibria of Fe I and Fe II lines under the assumption of local thermodynamic equilibrium. The abundance analysis reveals that HD 8270, HD 13551, and HD 22589 have metallicities of [Fe/H] = -0.43, -0.28, and -0.12, respectively. It was found that the abundances of iron group and α-elements follow the abundance pattern of a disk population. The heavy-element abundance patterns of the three stars show enhancements by a factor of 4–8 with respect to the Sun. The abundances of the s-process elements are discussed and compared with other barium giants and dwarfs through diagrams involving the indices [hs/ls] and [s/Fe]. The metallicity distribution of barium giants and dwarfs is also discussed.

We present LTE and NLTE atmospheric models of a star with solar parameters, and study the effect of treating many thousands of Iron group lines out of LTE on the computed atmospheric structure, overall absolute flux distribution, and the moderately high resolution spectrum in the visible and near UV bands. Our NLTE modeling includes the first two or three ionization stages of 20 chemical elements, up to and including much of the Fe-group, and includes about 20000 Fe I and II lines. We investigate separately the effects of treating the light metals and the Fe-group elements in NLTE. Our main conclusions are that 1) NLTE line blanketed models with direct multi-level NLTE for many actual transitions gives qualitatively similar results as the more approximate treatment of Anderson (1989) for both the Fe statistical equilibrium and the atmospheric temperature structure, 2) models with many Fe lines in NLTE have a temperature structure that agrees more closely with LTE semi-empirical models based on center-to-limb variation and a wide variety of spectra lines, whereas LTE models agree more with semi-empirical models based only on an LTE calculation of the Fe I excitation equilibrium, 3) the NLTE effects of Fe-group elements on the model structure and flux distribution are much more important than the NLTE effects of all the light metals combined, and serve to substantially increases the violet and near UV flux level as a result of NLTE Fe over-ionization. These results suggest that there may still be important UV opacity missing from the models., Comment: Accepted for publication in The Astrophysical Journal