A Second Candidate Magnetic Helium Core White Dwarf and 3 Other Variable White Dwarfs in the Globular Cluster NGC 6397
Using archival Hubble Space Telescope observations, we report the discovery of four variable low-mass white dwarfs (WDs; 0.18 M _⊙ ≤ M ≤ 0.5 M _⊙ ) in the globular cluster NGC 6397. One source exhibits a periodic optical modulation of 5.21 ± 0.02 hr, which we interpret as potentially due to the rota...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ada144 |
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| author | Manuel Pichardo Marcano Liliana E. Rivera Sandoval Thomas J. Maccarone Rene D. Rohrmann Leandro G. Althaus Craig O. Heinke Diogo Belloni Arash Bahramian |
| author_facet | Manuel Pichardo Marcano Liliana E. Rivera Sandoval Thomas J. Maccarone Rene D. Rohrmann Leandro G. Althaus Craig O. Heinke Diogo Belloni Arash Bahramian |
| author_sort | Manuel Pichardo Marcano |
| collection | DOAJ |
| description | Using archival Hubble Space Telescope observations, we report the discovery of four variable low-mass white dwarfs (WDs; 0.18 M _⊙ ≤ M ≤ 0.5 M _⊙ ) in the globular cluster NGC 6397. One source exhibits a periodic optical modulation of 5.21 ± 0.02 hr, which we interpret as potentially due to the rotation of a magnetic helium core WD (He WD). This makes this candidate the second magnetic He WD in NGC 6397, and one of the few He WDs with a measured rotation period. The other three candidates show aperiodic variability, with a change in magnitude ranging from ∼0.11 to 0.6. These discoveries highlight the importance of high-cadence photometric surveys in dense stellar environments. Follow-up spectroscopic observations are needed to confirm the nature of the variability of these systems. |
| format | Article |
| id | doaj-art-ed680348ff0d47dea4a0d8e3e48fbfb2 |
| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-ed680348ff0d47dea4a0d8e3e48fbfb22025-01-24T10:03:37ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01979216710.3847/1538-4357/ada144A Second Candidate Magnetic Helium Core White Dwarf and 3 Other Variable White Dwarfs in the Globular Cluster NGC 6397Manuel Pichardo Marcano0https://orcid.org/0000-0003-4436-831XLiliana E. Rivera Sandoval1https://orcid.org/0000-0002-9396-7215Thomas J. Maccarone2https://orcid.org/0000-0003-0976-4755Rene D. Rohrmann3https://orcid.org/0000-0001-7209-3574Leandro G. Althaus4https://orcid.org/0000-0003-2771-7805Craig O. Heinke5https://orcid.org/0000-0003-3944-6109Diogo Belloni6https://orcid.org/0000-0003-1535-0866Arash Bahramian7https://orcid.org/0000-0003-2506-6041Department of Life and Physical Sciences, Fisk University , 1000 17th Avenue N., Nashville, TN 37208, USA ; mmarcano@fisk.edu; Department of Physics and Astronomy, Vanderbilt University , 6301 Stevenson Center Lane, Nashville, TN 37235, USADepartment of Physics and Astronomy, University of Texas Rio Grande Valley , Brownsville, TX 78520, USADepartment of Physics and Astronomy, Texas Tech University , Lubbock, TX 79409, USAInstituto de Ciencias Astronómicas , de la Tierra y del Espacio (CONICET-UNSJ), Av. España 1512 (sur), 5400 San Juan, ArgentinaGrupo de Evolución Estelar y Pulsaciones. Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata , Paseo del Bosque s/n, 1900 La Plata, Argentina; IALP—CONICET , La Plata, ArgentinaDepartment of Physics, University of Alberta , CCIS 4-183, Edmonton, AB, T6G 2E1, CanadaDepartamento de Física, Universidad Técnica Federico Santa María , Av. España 1680, Valparaíso, ChileInternational Center for Radio Astronomy Research Curtin University , GPO Box U1987, Perth, WA 6845, AustraliaUsing archival Hubble Space Telescope observations, we report the discovery of four variable low-mass white dwarfs (WDs; 0.18 M _⊙ ≤ M ≤ 0.5 M _⊙ ) in the globular cluster NGC 6397. One source exhibits a periodic optical modulation of 5.21 ± 0.02 hr, which we interpret as potentially due to the rotation of a magnetic helium core WD (He WD). This makes this candidate the second magnetic He WD in NGC 6397, and one of the few He WDs with a measured rotation period. The other three candidates show aperiodic variability, with a change in magnitude ranging from ∼0.11 to 0.6. These discoveries highlight the importance of high-cadence photometric surveys in dense stellar environments. Follow-up spectroscopic observations are needed to confirm the nature of the variability of these systems.https://doi.org/10.3847/1538-4357/ada144White dwarf starsGlobular star clustersStellar magnetic fields |
| spellingShingle | Manuel Pichardo Marcano Liliana E. Rivera Sandoval Thomas J. Maccarone Rene D. Rohrmann Leandro G. Althaus Craig O. Heinke Diogo Belloni Arash Bahramian A Second Candidate Magnetic Helium Core White Dwarf and 3 Other Variable White Dwarfs in the Globular Cluster NGC 6397 The Astrophysical Journal White dwarf stars Globular star clusters Stellar magnetic fields |
| title | A Second Candidate Magnetic Helium Core White Dwarf and 3 Other Variable White Dwarfs in the Globular Cluster NGC 6397 |
| title_full | A Second Candidate Magnetic Helium Core White Dwarf and 3 Other Variable White Dwarfs in the Globular Cluster NGC 6397 |
| title_fullStr | A Second Candidate Magnetic Helium Core White Dwarf and 3 Other Variable White Dwarfs in the Globular Cluster NGC 6397 |
| title_full_unstemmed | A Second Candidate Magnetic Helium Core White Dwarf and 3 Other Variable White Dwarfs in the Globular Cluster NGC 6397 |
| title_short | A Second Candidate Magnetic Helium Core White Dwarf and 3 Other Variable White Dwarfs in the Globular Cluster NGC 6397 |
| title_sort | second candidate magnetic helium core white dwarf and 3 other variable white dwarfs in the globular cluster ngc 6397 |
| topic | White dwarf stars Globular star clusters Stellar magnetic fields |
| url | https://doi.org/10.3847/1538-4357/ada144 |
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