Chemical abundances of open clusters from high-resolution infrared spectra-I. NGC 6940

We present near-infrared spectroscopic analysis of 12 red giant members of the Galactic open cluster NGC 6940. High-resolution (R ~ 45 000) and high-signal-to-noise ratio (S/N > 100) near-infrared H- A nd K-band spectra were gathered with the Immersion Grating Infrared Spectrograph (IGRINS) on the 2.7-m Smith Telescope at McDonald Observatory.We obtained abundances of H-burning (C, N, O), ? (Mg, Si, S, Ca), light odd-Z (Na, Al, P, K), Fe-group (Sc, Ti, Cr, Fe, Co, Ni), and neutron-capture (Ce, Nd, Yb) elements.We report the abundances of S, P, K, Ce, and Yb in NGC 6940 for the first time. Many OH and CN features in the H band were used to obtain O and N abundances. C abundances were measured from four different features: CO molecular lines in the K band, high excitation CI lines present in both near-infrared and optical, CH and C2 bands in the optical region. We have also determined 12C/13C ratios from the R-branch band heads of first overtone (2.0) and (3.1) 12COand (2.0) 13CO lines near 23 440 A and (3.1) 13CO lines at about 23 730 A. We have also investigated the HF feature at 23 358.3 A, finding solar fluorine abundances without ruling out a slight enhancement. For some elements (such as the ? group), IGRINS data yield more internally self-consistent abundances.We also revisited the CMD of NGC 6940 by determining the most probable cluster members using Gaia DR2. Finally, we applied Victoria isochrones and MESA models in order to refine our estimates of the evolutionary stages of our targets. © 2019 The Author(s).Korea Astronomy and Space Science Institute: AST-1229522 European Space Agency University of Texas at Austin National Science Foundation: AST 16-16040 Texas A and M University-Central Texas 116F407We thank the anonymous referee for her/his comments and suggestions that improved the quality of the paper. We thank Karin Lind and Henrique Reggiani for helpful discussions on this work. Our work has been supported by The Scientific and Technological Research Council of Turkey (TÜB'TAK, project No. 116F407), by the US National Science Foundation (NSF, grant AST 16-16040), and by the University of Texas Rex G. Baker, Jr. Centennial Research Endowment. This work used the Immersion Grating Infrared Spectrometer (IGRINS) that was developed under a collaboration between the University of Texas at Austin and the Korea Astronomy and Space Science Institute (KASI) with the financial support of the US National Science Foundation under grant AST-1229522, of the University of Texas at Austin, and of the Korean GMT Project of KASI. This work has made use of data from the European Space Agency (ESA) mission Gaia (https: //www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web /gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This research has made use of NASA’s Astrophysics Data System Bibliographic Services; the SIMBAD database and the VizieR service, both operated at CDS, Strasbourg, France. This research has made use of the WEBDA database, operated at the Department of Theoretical Physics and Astrophysics of the Masaryk University, and the VALD database, operated at Uppsala University, the Institute of Astronomy RAS in Moscow, and the University of Vienna. This paper includes data taken at The McDonald Observatory of The University of Texas at Austin. -

The Rate and Spatial Distribution of Novae in M31 as Determined by a 20 Year Survey

A long-term (1995-2016) survey for novae in the nearby Andromeda galaxy (M31) was conducted as part of the Research-Based Science Education initiative. During the course of the survey 180 nights of observation were completed at Kitt Peak, Arizona. A total of 262 novae were either discovered or confirmed, 40 of which have not been previously reported. Of these, 203 novae form a spatially complete sample detected by the KPNO/WIYN 0.9 m telescope within a 20 ′ × 20 ′ field centered on the nucleus of M31. An additional 50 novae are part of a spatially complete sample detected by the KPNO 4 m telescope within a larger 36 ′ × 36 ′ field. Consistent with previous studies, it is found that the spatial distribution of novae in both surveys follows the bulge light of M31 somewhat more closely than the overall background light of the galaxy. After correcting for the limiting magnitude and the spatial and temporal coverage of the surveys, a final nova rate in M31 is found to be R = 40 − 4 + 5 yr−1, which is considerably lower than recent estimates. When normalized to the K-band luminosity of M31, this value yields a luminosity-specific nova rate, ν K = 3.3 ± 0.4 yr − 1 [ 10 10 L ⊙ , K ] − 1 . By scaling the M31 nova rate using the relative infrared luminosities of M31 and our Galaxy, a nova rate of R G = 28 − 4 + 5 yr−1 is found for the Milky Way. © 2022. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The origin and abundances of the chemical elements revisited

The basic scheme of nucleosynthesis (building of heavy elements from light ones) has held up very well since it was first proposed more than 30 years ago by E.M. Burbidge, G.R. Burbidge, A.G.W. Cameron, W.A. Fowler, and F. Hoyle. Significant advances in the intervening years include (a) observations of elemental and a few isotopic ratios in many more extrasolar-system sites, including metal-poor dwarf irregular galaxies, where very little has happened, and supernovae and their remnants, where a great deal has happened, (b) recognition of the early universe as good for making all the elements up to helium, (c) resolution of heavy element burning in stars into separate carbon, neon, oxygen, and silicon burning, with fine tuning of the resulting abundances by explosive nucleosynthesis in outgoing supernova shock waves, (d) clarification of the role of Type I supernovae, (e) concordance between elements produced in short-lived and long-lived stars with those that increased quickly and slowly over the history of the galaxy, and (f) calibration of calculations of the evolution and explosion of massive stars against the detailed observations of SN 1987A. The discussion presupposes a reader (a) with some prior knowledge of astronomy at the level of recognizing what is meant by an A star and an AGB star and (b) with at least a mild interest in how we got to where we currently are. © 1991 Springer-Verlag