The Role of Binarity and Stellar Rotation in the Split Main Sequence of NGC 2422
In addition to the extended main-sequence turnoffs widely found in young and intermediate-age (∼600 Myr to 2 Gyr old) star clusters, some younger clusters even exhibit split main sequences (MSs). Different stellar rotation rates are proposed to account for the bifurcated MS pattern, with red and blu...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2022-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ac8b08 |
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| author | Chenyu He Weijia Sun Chengyuan Li Lu Li Zhengyi Shao Jing Zhong Li Chen Richard de Grijs Baitian Tang Songmei Qin Zara Randriamanakoto |
| author_facet | Chenyu He Weijia Sun Chengyuan Li Lu Li Zhengyi Shao Jing Zhong Li Chen Richard de Grijs Baitian Tang Songmei Qin Zara Randriamanakoto |
| author_sort | Chenyu He |
| collection | DOAJ |
| description | In addition to the extended main-sequence turnoffs widely found in young and intermediate-age (∼600 Myr to 2 Gyr old) star clusters, some younger clusters even exhibit split main sequences (MSs). Different stellar rotation rates are proposed to account for the bifurcated MS pattern, with red and blue MSs (rMS and bMS) populated by fast and slowly rotating stars, respectively. Using photometry from Gaia Early Data Release 3, we report a Galactic open cluster with a bifurcated MS, NGC 2422 (∼90 Myr). We exclude the possibilities that the bifurcated MS pattern is caused by photometric noise or differential reddening. We aim to examine if stellar rotation can account for the split MS. We use spectra observed with the Canada–France–Hawaii Telescope and the Southern African Large Telescope and directly measured $v\sin i$ , the projected rotational velocities, for stars populating the bMS and rMS. We find that their $v\sin i$ values are weakly correlated with their loci in the color–magnitude diagram because of contamination caused by a large fraction of rMS stars with low projected rotational velocities. Based on the spectral energy distribution fitting method, we suggest that these slowly rotating stars at the rMS may hide a binary companion, which breaks the expected $v\sin i$ –color correlation. Future time-domain studies focusing on whether these slowly rotating stars are radial velocity variables are crucial to test the roles of stellar rotation and binarity in generating the split MSs. |
| first_indexed | 2024-03-11T23:56:00Z |
| format | Article |
| id | doaj.art-67612473fedc4f02ae9a3f72ea3bbc40 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-11T23:56:00Z |
| publishDate | 2022-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-67612473fedc4f02ae9a3f72ea3bbc402023-09-18T11:21:31ZengIOP PublishingThe Astrophysical Journal1538-43572022-01-0193814210.3847/1538-4357/ac8b08The Role of Binarity and Stellar Rotation in the Split Main Sequence of NGC 2422Chenyu He0https://orcid.org/0000-0001-9131-6956Weijia Sun1https://orcid.org/0000-0002-3279-0233Chengyuan Li2https://orcid.org/0000-0002-3084-5157Lu Li3https://orcid.org/0000-0002-0880-3380Zhengyi Shao4https://orcid.org/0000-0001-8611-2465Jing Zhong5https://orcid.org/0000-0001-5245-0335Li Chen6https://orcid.org/0000-0002-4907-9720Richard de Grijs7https://orcid.org/0000-0002-7203-5996Baitian Tang8https://orcid.org/0000-0002-0066-0346Songmei Qin9https://orcid.org/0000-0003-3713-2640Zara Randriamanakoto10https://orcid.org/0000-0003-2666-4158School of Physics and Astronomy, Sun Yat-sen University , Zhuhai, 519082, People's Republic of China; CSST Science Center for the Guangdong–Hong Kong–Macau Greater Bay Area , Zhuhai, 519082, People's Republic of China ; lichengy5@mail.sysu.edu.cnDepartment of Astronomy, Peking University , Yi He Yuan Lu 5, Hai Dian District, Beijing, 100871, People's Republic of China ; weijia@gmail.com; CAS Key Laboratory of Optical Astronomy, National Astronomical Observatories , Chinese Academy of Sciences, Beijing, 100101, People's Republic of ChinaSchool of Physics and Astronomy, Sun Yat-sen University , Zhuhai, 519082, People's Republic of China; CSST Science Center for the Guangdong–Hong Kong–Macau Greater Bay Area , Zhuhai, 519082, People's Republic of China ; lichengy5@mail.sysu.edu.cnKey Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory , Chinese Academy of Sciences, 80 Nandan Road, Shanghai, 200030, People's Republic of China; School of Astronomy and Space Science, University of Chinese Academy of Sciences , 19A Yuquan Road, Beijing, 100049, People's Republic of China; Centre for Astrophysics and Planetary Science, Racah Institute of Physics , The Hebrew University, Jerusalem, 91904, IsraelKey Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory , Chinese Academy of Sciences, 80 Nandan Road, Shanghai, 200030, People's Republic of China; Key Laboratory for Astrophysics , Chinese Academy of Sciences, Shanghai, 200234, People's Republic of ChinaKey Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory , Chinese Academy of Sciences, 80 Nandan Road, Shanghai, 200030, People's Republic of ChinaKey Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory , Chinese Academy of Sciences, 80 Nandan Road, Shanghai, 200030, People's Republic of China; School of Astronomy and Space Science, University of Chinese Academy of Sciences , 19A Yuquan Road, Beijing, 100049, People's Republic of ChinaSchool of Mathematical and Physical Sciences, Macquarie University , Balaclava Road, Sydney, NSW 2109, Australia; Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University , Balaclava Road, Sydney, NSW 2109, AustraliaSchool of Physics and Astronomy, Sun Yat-sen University , Zhuhai, 519082, People's Republic of China; CSST Science Center for the Guangdong–Hong Kong–Macau Greater Bay Area , Zhuhai, 519082, People's Republic of China ; lichengy5@mail.sysu.edu.cnKey Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory , Chinese Academy of Sciences, 80 Nandan Road, Shanghai, 200030, People's Republic of China; School of Astronomy and Space Science, University of Chinese Academy of Sciences , 19A Yuquan Road, Beijing, 100049, People's Republic of ChinaSouth African Astronomical Observatory , P.O. Box 9, Observatory, Cape Town 7935, South Africa; Department of Physics, University of Antananarivo , P.O. Box 906, Antananarivo, MadagascarIn addition to the extended main-sequence turnoffs widely found in young and intermediate-age (∼600 Myr to 2 Gyr old) star clusters, some younger clusters even exhibit split main sequences (MSs). Different stellar rotation rates are proposed to account for the bifurcated MS pattern, with red and blue MSs (rMS and bMS) populated by fast and slowly rotating stars, respectively. Using photometry from Gaia Early Data Release 3, we report a Galactic open cluster with a bifurcated MS, NGC 2422 (∼90 Myr). We exclude the possibilities that the bifurcated MS pattern is caused by photometric noise or differential reddening. We aim to examine if stellar rotation can account for the split MS. We use spectra observed with the Canada–France–Hawaii Telescope and the Southern African Large Telescope and directly measured $v\sin i$ , the projected rotational velocities, for stars populating the bMS and rMS. We find that their $v\sin i$ values are weakly correlated with their loci in the color–magnitude diagram because of contamination caused by a large fraction of rMS stars with low projected rotational velocities. Based on the spectral energy distribution fitting method, we suggest that these slowly rotating stars at the rMS may hide a binary companion, which breaks the expected $v\sin i$ –color correlation. Future time-domain studies focusing on whether these slowly rotating stars are radial velocity variables are crucial to test the roles of stellar rotation and binarity in generating the split MSs.https://doi.org/10.3847/1538-4357/ac8b08Open star clustersStar clustersStellar rotation |
| spellingShingle | Chenyu He Weijia Sun Chengyuan Li Lu Li Zhengyi Shao Jing Zhong Li Chen Richard de Grijs Baitian Tang Songmei Qin Zara Randriamanakoto The Role of Binarity and Stellar Rotation in the Split Main Sequence of NGC 2422 The Astrophysical Journal Open star clusters Star clusters Stellar rotation |
| title | The Role of Binarity and Stellar Rotation in the Split Main Sequence of NGC 2422 |
| title_full | The Role of Binarity and Stellar Rotation in the Split Main Sequence of NGC 2422 |
| title_fullStr | The Role of Binarity and Stellar Rotation in the Split Main Sequence of NGC 2422 |
| title_full_unstemmed | The Role of Binarity and Stellar Rotation in the Split Main Sequence of NGC 2422 |
| title_short | The Role of Binarity and Stellar Rotation in the Split Main Sequence of NGC 2422 |
| title_sort | role of binarity and stellar rotation in the split main sequence of ngc 2422 |
| topic | Open star clusters Star clusters Stellar rotation |
| url | https://doi.org/10.3847/1538-4357/ac8b08 |
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