Cool, Luminous, and Highly Variable Stars in the Magellanic Clouds. II. Spectroscopic and Environmental Analysis of Thorne–Żytkow Object and Super-AGB Star Candidates
In previous work, we identified a population of 38 cool and luminous variable stars in the Magellanic Clouds and examined 11 in detail in order to classify them as either Thorne–Żytkow objects (TŻOs; red supergiants with a neutron star cores) or super-asymptotic giant branch (sAGB) stars (the most m...
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| Format: | Article |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/aca655 |
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| author | Anna J. G. O‘Grady Maria R. Drout B. M. Gaensler C. S. Kochanek Kathryn F. Neugent Carolyn L. Doherty Joshua S. Speagle B. J. Shappee Michael Rauch Ylva Götberg Bethany Ludwig Todd A. Thompson |
| author_facet | Anna J. G. O‘Grady Maria R. Drout B. M. Gaensler C. S. Kochanek Kathryn F. Neugent Carolyn L. Doherty Joshua S. Speagle B. J. Shappee Michael Rauch Ylva Götberg Bethany Ludwig Todd A. Thompson |
| author_sort | Anna J. G. O‘Grady |
| collection | DOAJ |
| description | In previous work, we identified a population of 38 cool and luminous variable stars in the Magellanic Clouds and examined 11 in detail in order to classify them as either Thorne–Żytkow objects (TŻOs; red supergiants with a neutron star cores) or super-asymptotic giant branch (sAGB) stars (the most massive stars that will not undergo core collapse). This population includes HV 2112, a peculiar star previously considered in other works to be either a TŻO or high-mass asymptotic giant branch (AGB) star. Here we continue this investigation, using the kinematic and radio environments and local star formation history of these stars to place constraints on the age of the progenitor systems and the presence of past supernovae. These stars are not associated with regions of recent star formation, and we find no evidence of past supernovae at their locations. Finally, we also assess the presence of heavy elements and lithium in their spectra compared to red supergiants. We find strong absorption in Li and s-process elements compared to RSGs in most of the sample, consistent with sAGB nucleosynthesis, while HV 2112 shows additional strong lines associated with TŻO nucleosynthesis. Coupled with our previous mass estimates, the results are consistent with the stars being massive (∼4–6.5 M _⊙ ) or sAGB (∼6.5–12 M _⊙ ) stars in the thermally pulsing phase, providing crucial observations of the transition between low- and high-mass stellar populations. HV 2112 is more ambiguous; it could either be a maximally massive sAGB star, or a TŻO if the minimum mass for stability extends down to ≲13 M _⊙ . |
| first_indexed | 2024-03-12T04:33:57Z |
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| id | doaj.art-895901d5696945a6ae3f6cbc82d4d9f4 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T04:33:57Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
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| spelling | doaj.art-895901d5696945a6ae3f6cbc82d4d9f42023-09-03T09:58:13ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0194311810.3847/1538-4357/aca655Cool, Luminous, and Highly Variable Stars in the Magellanic Clouds. II. Spectroscopic and Environmental Analysis of Thorne–Żytkow Object and Super-AGB Star CandidatesAnna J. G. O‘Grady0https://orcid.org/0000-0002-7296-6547Maria R. Drout1https://orcid.org/0000-0001-7081-0082B. M. Gaensler2https://orcid.org/0000-0002-3382-9558C. S. Kochanek3https://orcid.org/0000-0001-6017-2961Kathryn F. Neugent4https://orcid.org/0000-0002-5787-138XCarolyn L. Doherty5https://orcid.org/0000-0001-8161-4087Joshua S. Speagle6https://orcid.org/0000-0003-2573-9832B. J. Shappee7https://orcid.org/0000-0003-4631-1149Michael Rauch8https://orcid.org/0000-0002-1690-3488Ylva Götberg9https://orcid.org/0000-0002-6960-6911Bethany Ludwig10https://orcid.org/0000-0003-0857-2989Todd A. Thompson11https://orcid.org/0000-0003-2377-9574David A. Dunlap Department of Astronomy & Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON, M5S3H4 Canada anna.ogrady@mail.utoronto.ca; Dunlap Institute for Astronomy & Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON, M5S3H4, CanadaDavid A. Dunlap Department of Astronomy & Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON, M5S3H4 Canada anna.ogrady@mail.utoronto.ca; The Observatories of the Carnegie Institution for Science , 813 Santa Barbara Street, Pasadena, CA 91101, USADavid A. Dunlap Department of Astronomy & Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON, M5S3H4 Canada anna.ogrady@mail.utoronto.ca; Dunlap Institute for Astronomy & Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON, M5S3H4, CanadaDepartment of Astronomy, The Ohio State University , 140 West 18th Avenue, Columbus, OH 43210, USA; Center for Cosmology and Astroparticle Physics, The Ohio State University , 191 W. Woodruff Avenue, Columbus, OH 43210, USADunlap Institute for Astronomy & Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON, M5S3H4, Canada; Lowell Observatory , 1400 W Mars Hill Road, Flagstaff, AZ 86001, USA; Center for Astrophysics | Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138-1516, USASchool of Physics and Astronomy, Monash University , VIC 3800, AustraliaDavid A. Dunlap Department of Astronomy & Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON, M5S3H4 Canada anna.ogrady@mail.utoronto.ca; Dunlap Institute for Astronomy & Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON, M5S3H4, Canada; Department of Statistical Sciences, University of Toronto , 100 St George Street, Toronto ON, M5S3G3, CanadaInstitute for Astronomy, University of Hawaii , 2680 Woodlawn Drive, Honolulu, H i 96822, USAThe Observatories of the Carnegie Institution for Science , 813 Santa Barbara Street, Pasadena, CA 91101, USAThe Observatories of the Carnegie Institution for Science , 813 Santa Barbara Street, Pasadena, CA 91101, USADavid A. Dunlap Department of Astronomy & Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON, M5S3H4 Canada anna.ogrady@mail.utoronto.ca; Dunlap Institute for Astronomy & Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON, M5S3H4, CanadaDepartment of Astronomy, The Ohio State University , 140 West 18th Avenue, Columbus, OH 43210, USA; Center for Cosmology and Astroparticle Physics, The Ohio State University , 191 W. Woodruff Avenue, Columbus, OH 43210, USAIn previous work, we identified a population of 38 cool and luminous variable stars in the Magellanic Clouds and examined 11 in detail in order to classify them as either Thorne–Żytkow objects (TŻOs; red supergiants with a neutron star cores) or super-asymptotic giant branch (sAGB) stars (the most massive stars that will not undergo core collapse). This population includes HV 2112, a peculiar star previously considered in other works to be either a TŻO or high-mass asymptotic giant branch (AGB) star. Here we continue this investigation, using the kinematic and radio environments and local star formation history of these stars to place constraints on the age of the progenitor systems and the presence of past supernovae. These stars are not associated with regions of recent star formation, and we find no evidence of past supernovae at their locations. Finally, we also assess the presence of heavy elements and lithium in their spectra compared to red supergiants. We find strong absorption in Li and s-process elements compared to RSGs in most of the sample, consistent with sAGB nucleosynthesis, while HV 2112 shows additional strong lines associated with TŻO nucleosynthesis. Coupled with our previous mass estimates, the results are consistent with the stars being massive (∼4–6.5 M _⊙ ) or sAGB (∼6.5–12 M _⊙ ) stars in the thermally pulsing phase, providing crucial observations of the transition between low- and high-mass stellar populations. HV 2112 is more ambiguous; it could either be a maximally massive sAGB star, or a TŻO if the minimum mass for stability extends down to ≲13 M _⊙ .https://doi.org/10.3847/1538-4357/aca655Massive starsAsymptotic giant branch starsChemically peculiar starsLithium starsSpectroscopyStellar kinematics |
| spellingShingle | Anna J. G. O‘Grady Maria R. Drout B. M. Gaensler C. S. Kochanek Kathryn F. Neugent Carolyn L. Doherty Joshua S. Speagle B. J. Shappee Michael Rauch Ylva Götberg Bethany Ludwig Todd A. Thompson Cool, Luminous, and Highly Variable Stars in the Magellanic Clouds. II. Spectroscopic and Environmental Analysis of Thorne–Żytkow Object and Super-AGB Star Candidates The Astrophysical Journal Massive stars Asymptotic giant branch stars Chemically peculiar stars Lithium stars Spectroscopy Stellar kinematics |
| title | Cool, Luminous, and Highly Variable Stars in the Magellanic Clouds. II. Spectroscopic and Environmental Analysis of Thorne–Żytkow Object and Super-AGB Star Candidates |
| title_full | Cool, Luminous, and Highly Variable Stars in the Magellanic Clouds. II. Spectroscopic and Environmental Analysis of Thorne–Żytkow Object and Super-AGB Star Candidates |
| title_fullStr | Cool, Luminous, and Highly Variable Stars in the Magellanic Clouds. II. Spectroscopic and Environmental Analysis of Thorne–Żytkow Object and Super-AGB Star Candidates |
| title_full_unstemmed | Cool, Luminous, and Highly Variable Stars in the Magellanic Clouds. II. Spectroscopic and Environmental Analysis of Thorne–Żytkow Object and Super-AGB Star Candidates |
| title_short | Cool, Luminous, and Highly Variable Stars in the Magellanic Clouds. II. Spectroscopic and Environmental Analysis of Thorne–Żytkow Object and Super-AGB Star Candidates |
| title_sort | cool luminous and highly variable stars in the magellanic clouds ii spectroscopic and environmental analysis of thorne zytkow object and super agb star candidates |
| topic | Massive stars Asymptotic giant branch stars Chemically peculiar stars Lithium stars Spectroscopy Stellar kinematics |
| url | https://doi.org/10.3847/1538-4357/aca655 |
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