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On the discovery of K-enhanced and possibly Mg-depleted stars throughout the Milky Way

Kemp, Alex J. and Casey, Andrew R. and Miles, Matthew T. and Norfolk, Brodie J. and Lattanzio, John C. and Karakas, Amanda I. and Schlaufman, Kevin C. and Ho, Anna Y. Q. and Tout, Christopher A. and Ness, Melissa and Ji, Alexander P. (2018) On the discovery of K-enhanced and possibly Mg-depleted stars throughout the Milky Way. Monthly Notices of the Royal Astronomical Society, 480 (1). pp. 1384-1392. ISSN 0035-8711.

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Stars with unusual elemental abundances offer clues about rare astrophysical events or nucleosynthetic pathways. Stars with significantly depleted magnesium and enhanced potassium ([Mg/Fe] < −0.5; [K/Fe] > 1) have to date only been found in the massive globular cluster NGC 2419 and, to a lesser extent, NGC 2808. The origin of this abundance signature remains unknown, as does the reason for its apparent exclusivity to these two globular clusters. Here we present 112 field stars, identified from 454 180 LAMOST giants, that show significantly enhanced [K/Fe] and possibly depleted [Mg/Fe] abundance ratios. Our sample spans a wide range of metallicities (−1.5 < [Fe/H] < 0.3), yet none show abundance ratios of [K/Fe] or [Mg/Fe] that are as extreme as those observed in NGC 2419. If confirmed, the identified sample of stars represents evidence that the nucleosynthetic process producing the anomalous abundances ratios of [K/Fe] and [Mg/Fe] probably occurs at a wide range of metallicities. This would suggest that pollution scenarios that are limited to early epochs (such as Population III supernovae) are an unlikely explanation, although they cannot be ruled out entirely. This sample is expected to help guide modelling attempts to explain the origin of the Mg–K abundance signature.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Casey, Andrew R.0000-0003-0174-0564
Lattanzio, John C.0000-0003-2952-859X
Karakas, Amanda I.0000-0002-3625-6951
Schlaufman, Kevin C.0000-0001-5761-6779
Ho, Anna Y. Q.0000-0002-9017-3567
Tout, Christopher A.0000-0002-1556-9449
Ness, Melissa0000-0001-5082-6693
Additional Information:© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2018 July 13. Received 2018 July 10; in original form 2018 March 2. We thank David W. Hogg (NYU), and Hans-Walter Rix (MPIA). ARC is supported through an Australian Research Council Discovery Project under grant DP160100637. AYQH is supported by a Fulbright grant through the German-American Fulbright Commission and a National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144469. CAT thanks Churchill College for his fellowship and Monash University for hosting him as a Kevin Westfold distinguished visitor. This research has made use of NASA’s Astrophysics Data System. Guoshoujing Telescope (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope LAMOST) is a National Major Scientific Project built by the Chinese Academy of Sciences. Funding for the project has beenprovided by the National Development and Reform Commission. LAMOST is operated and managed by the National Astronomical Observatories, Chinese Academy of Sciences. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.
Funding AgencyGrant Number
Australian Research CouncilDP160100637
German-American Fulbright CommissionUNSPECIFIED
NSF Graduate Research FellowshipDGE-1144469
Churchill CollegeUNSPECIFIED
National Development and Reform Commission (China)UNSPECIFIED
Subject Keywords:methods: data analysis, catalogues, stars: chemically peculiar, Galaxy: abundances, Galaxy: evolution, globular clusters: individual: evolution
Issue or Number:1
Record Number:CaltechAUTHORS:20180913-133205871
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Official Citation:Alex J Kemp, Andrew R Casey, Matthew T Miles, Brodie J Norfolk, John C Lattanzio, Amanda I Karakas, Kevin C Schlaufman, Anna Y Q Ho, Christopher A Tout, Melissa Ness, Alexander P Ji; On the discovery of K-enhanced and possibly Mg-depleted stars throughout the Milky Way, Monthly Notices of the Royal Astronomical Society, Volume 480, Issue 1, 11 October 2018, Pages 1384–1392,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:89625
Deposited By: George Porter
Deposited On:13 Sep 2018 22:15
Last Modified:09 Mar 2020 13:19

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