Discovery of WINERED-HVS1: A Metal-rich Hypervelocity Star Candidate Ejected from the Galactic Center
We report the discovery of a metal-rich red-giant star, WINERED-HVS1, which is a candidate for a hypervelocity star (HVS). Its past trajectory suggests that this star may have been ejected by the Galactic supermassive black hole (SMBH; Sgr A*), with a modest ejection velocity of at least 500 km s ^−...
Saved in:
| Main Authors: | , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
|
| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/ade78a |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1850033545275244544 |
|---|---|
| author | Kohei Hattori Daisuke Taniguchi Takuji Tsujimoto Noriyuki Matsunaga Hiroaki Sameshima Scarlet S. Elgueta Shogo Otsubo |
| author_facet | Kohei Hattori Daisuke Taniguchi Takuji Tsujimoto Noriyuki Matsunaga Hiroaki Sameshima Scarlet S. Elgueta Shogo Otsubo |
| author_sort | Kohei Hattori |
| collection | DOAJ |
| description | We report the discovery of a metal-rich red-giant star, WINERED-HVS1, which is a candidate for a hypervelocity star (HVS). Its past trajectory suggests that this star may have been ejected by the Galactic supermassive black hole (SMBH; Sgr A*), with a modest ejection velocity of at least 500 km s ^−1 . Since WINERED-HVS1 is gravitationally bound to the Milky Way and is not necessarily young, it is not an unambiguous HVS candidate from a kinematic perspective, unlike the previously confirmed A-type main-sequence HVS known as S5-HVS1. Therefore, the chemical characterization of this star is essential for understanding its origin. Through a spectroscopic follow-up observation with Magellan/WINERED, we determined its metallicity $[{\rm{Fe}}/{\rm{H}}]=-0.14{7}_{-0.045}^{+0.046}$ , as well as the abundances of Na, Mg, Si, S, K, Ca, Ti, Cr, Ni, and Sr. The high-metallicity value suggests that this star was ejected from the Galactic center and is unlikely to be a halo star with a radial orbit. The abundance pattern of this star—including the patterns of [ α /Fe], [Mg/Fe], [Si/Mg], and [Ca/Mg]—is consistent with that of the nuclear star cluster surrounding the SMBH, further supporting our view. This discovery opens a new window to look through the Galactic center environment without the hindrance of dust extinction, by using the HVSs moving in the halo region where dust extinction is minimal. |
| format | Article |
| id | doaj-art-32eb1d8609db4dd19b2642ce1ea5d535 |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-32eb1d8609db4dd19b2642ce1ea5d5352025-08-20T02:58:11ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01989214210.3847/1538-4357/ade78aDiscovery of WINERED-HVS1: A Metal-rich Hypervelocity Star Candidate Ejected from the Galactic CenterKohei Hattori0https://orcid.org/0000-0001-6924-8862Daisuke Taniguchi1https://orcid.org/0000-0002-2861-4069Takuji Tsujimoto2https://orcid.org/0000-0002-9397-3658Noriyuki Matsunaga3Hiroaki Sameshima4https://orcid.org/0000-0001-6401-723XScarlet S. Elgueta5https://orcid.org/0000-0001-5642-2569Shogo Otsubo6National Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan ; khattori@ism.ac.jp; The Institute of Statistical Mathematics , 10-3 Midoricho, Tachikawa, Tokyo 190-8562, Japan; Department of Astronomy, University of Michigan , 1085 S. University Avenue, Ann Arbor, MI 48109, USANational Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan ; khattori@ism.ac.jp; Department of Physics, Tokyo Metropolitan University , 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397, JapanNational Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan ; khattori@ism.ac.jpDepartment of Astronomy, Graduate School of Science, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; Laboratory of Infrared High-resolution spectroscopy (LiH), Koyama Astronomical Observatory, Kyoto Sangyo University , Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, JapanInstitute of Astronomy, Graduate School of Science, The University of Tokyo , 2-21-1 Osawa, Mitaka, Tokyo 181-0015, JapanDepartamento de Física, Universidad de Santiago de Chile , Av. Victor Jara 3659, Santiago, Chile; Millenium Nucleus ERIS, Instituto de Estudios Astrofísicos, Universidad Diego Portales , Av. Ejército Libertador 441, Santiago, ChileLaboratory of Infrared High-resolution spectroscopy (LiH), Koyama Astronomical Observatory, Kyoto Sangyo University , Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, JapanWe report the discovery of a metal-rich red-giant star, WINERED-HVS1, which is a candidate for a hypervelocity star (HVS). Its past trajectory suggests that this star may have been ejected by the Galactic supermassive black hole (SMBH; Sgr A*), with a modest ejection velocity of at least 500 km s ^−1 . Since WINERED-HVS1 is gravitationally bound to the Milky Way and is not necessarily young, it is not an unambiguous HVS candidate from a kinematic perspective, unlike the previously confirmed A-type main-sequence HVS known as S5-HVS1. Therefore, the chemical characterization of this star is essential for understanding its origin. Through a spectroscopic follow-up observation with Magellan/WINERED, we determined its metallicity $[{\rm{Fe}}/{\rm{H}}]=-0.14{7}_{-0.045}^{+0.046}$ , as well as the abundances of Na, Mg, Si, S, K, Ca, Ti, Cr, Ni, and Sr. The high-metallicity value suggests that this star was ejected from the Galactic center and is unlikely to be a halo star with a radial orbit. The abundance pattern of this star—including the patterns of [ α /Fe], [Mg/Fe], [Si/Mg], and [Ca/Mg]—is consistent with that of the nuclear star cluster surrounding the SMBH, further supporting our view. This discovery opens a new window to look through the Galactic center environment without the hindrance of dust extinction, by using the HVSs moving in the halo region where dust extinction is minimal.https://doi.org/10.3847/1538-4357/ade78aHypervelocity starsHigh-velocity starsSupermassive black holesStellar abundances |
| spellingShingle | Kohei Hattori Daisuke Taniguchi Takuji Tsujimoto Noriyuki Matsunaga Hiroaki Sameshima Scarlet S. Elgueta Shogo Otsubo Discovery of WINERED-HVS1: A Metal-rich Hypervelocity Star Candidate Ejected from the Galactic Center The Astrophysical Journal Hypervelocity stars High-velocity stars Supermassive black holes Stellar abundances |
| title | Discovery of WINERED-HVS1: A Metal-rich Hypervelocity Star Candidate Ejected from the Galactic Center |
| title_full | Discovery of WINERED-HVS1: A Metal-rich Hypervelocity Star Candidate Ejected from the Galactic Center |
| title_fullStr | Discovery of WINERED-HVS1: A Metal-rich Hypervelocity Star Candidate Ejected from the Galactic Center |
| title_full_unstemmed | Discovery of WINERED-HVS1: A Metal-rich Hypervelocity Star Candidate Ejected from the Galactic Center |
| title_short | Discovery of WINERED-HVS1: A Metal-rich Hypervelocity Star Candidate Ejected from the Galactic Center |
| title_sort | discovery of winered hvs1 a metal rich hypervelocity star candidate ejected from the galactic center |
| topic | Hypervelocity stars High-velocity stars Supermassive black holes Stellar abundances |
| url | https://doi.org/10.3847/1538-4357/ade78a |
| work_keys_str_mv | AT koheihattori discoveryofwineredhvs1ametalrichhypervelocitystarcandidateejectedfromthegalacticcenter AT daisuketaniguchi discoveryofwineredhvs1ametalrichhypervelocitystarcandidateejectedfromthegalacticcenter AT takujitsujimoto discoveryofwineredhvs1ametalrichhypervelocitystarcandidateejectedfromthegalacticcenter AT noriyukimatsunaga discoveryofwineredhvs1ametalrichhypervelocitystarcandidateejectedfromthegalacticcenter AT hiroakisameshima discoveryofwineredhvs1ametalrichhypervelocitystarcandidateejectedfromthegalacticcenter AT scarletselgueta discoveryofwineredhvs1ametalrichhypervelocitystarcandidateejectedfromthegalacticcenter AT shogootsubo discoveryofwineredhvs1ametalrichhypervelocitystarcandidateejectedfromthegalacticcenter |