GALEX J2339–0424 (GALEX J233917.0–042425, GALEX J2339) is a white dwarf that is suspected to be polluted with material originating from an icy exomoon. This is evident from the first detection of beryllium in this white dwarf, together with GD 378.[1][3]
 GALEX J2339–0424 (star in the center) as seen by GALEX Credit: NASA/JPL-Caltech GALEX | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 23h 39m 17.03s |
| Declination | −04° 24′ 24.67″ |
| Characteristics | |
| Evolutionary stage | white dwarf |
| Spectral type | DABZ[1] |
| Apparent magnitude (G) | 16.16[2] |
| Astrometry | |
| Radial velocity (Rv) | 6 ±5[1] km/s |
| Proper motion (μ) | RA: 24.501 ±0.058 mas/yr[2] Dec.: -32.293 ±0.048 mas/yr[2] |
| Parallax (π) | 11.2005 ± 0.0581 mas[2] |
| Distance | 291 ± 2 ly (89.3 ± 0.5 pc) |
| Details[1] | |
| Mass | 0.548 ±0.051 M☉ |
| Radius | 0.0133 ±0.0008 R☉ |
| Surface gravity (log g) | 7.93 ±0.09 cgs |
| Temperature | 13735 ±500 K |
| Age | cooling age: 241 ±6 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
GALEX J2339 was first identified as a possible quasar with GALEX in 2007.[4] It was identified as a white dwarf candidate from Gaia and virtual observatory data in 2018.[5] In 2020 it was identified as a DBAZ: white dwarf, which means that it had helium, hydrogen and metal absorption lines.[6] In 2021 the white dwarf was observed with Lick, Magellan 1 and Keck. The observations showed that the object had absorption due to hydrogen, helium, beryllium, oxygen, magnesium, silicon, calcium, titanium, chromium, manganese and iron.[1] The oxygen is present in excess, which indicates a water ice-rich body.[1][7] The accreted parent object had a chondrite-like composition and was 85% water ice in volume. The accretion event lasted for 2–4 Million years and the parent body had a mass of 3 × 1020–1 × 1021 kg, or between about the mass of Vesta to about the mass of Ceres.[3]
Exomoons as a source of white dwarf pollution has been proposed since 2016/2017[8][9] and their fate around white dwarfs was further studied later, showing that around 1% of polluted white dwarfs should be polluted with exomoons.[10] The presence of beryllium is thought to be the result of spallation of heavier elements (especially oxygen) on the surface of an icy dust belt around a giant planet. The icy dust belts enriched in beryllium will then form exomoons, which might pollute white dwarf. These icy dust belts are comparable to Saturns rings and rings around J1407b. Other scenarios are mentioned, such as the radiation of a Wolf-Rayet star. But these environments are less favourable to produce the observed beryllium excess. The spallation should also produce lithium and boron, but (as of September 2024) these are not detected around GALEX J2339 or GD 378.[3]
See also
editReferences
edit- ^ a b c d e f Klein, Beth L.; Doyle, Alexandra E.; Zuckerman, B.; Dufour, P.; Blouin, Simon; Melis, Carl; Weinberger, Alycia J.; Young, Edward D. (2021-06-01). "Discovery of Beryllium in White Dwarfs Polluted by Planetesimal Accretion". The Astrophysical Journal. 914 (1): 61. arXiv:2102.01834. Bibcode:2021ApJ...914...61K. doi:10.3847/1538-4357/abe40b. ISSN 0004-637X.
- ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
- ^ a b c Doyle, Alexandra E.; Desch, Steven J.; Young, Edward D. (2021-02-01). "Icy Exomoons Evidenced by Spallogenic Nuclides in Polluted White Dwarfs". The Astrophysical Journal. 907 (2): L35. arXiv:2102.01835. Bibcode:2021ApJ...907L..35D. doi:10.3847/2041-8213/abd9ba. ISSN 0004-637X.
- ^ Atlee, David W.; Gould, Andrew (2007-07-01). "Photometric Selection of QSO Candidates from GALEX Sources". The Astrophysical Journal. 664 (1): 53–63. arXiv:astro-ph/0611820. Bibcode:2007ApJ...664...53A. doi:10.1086/518467. ISSN 0004-637X.
- ^ Jiménez-Esteban, F. M.; Torres, S.; Rebassa-Mansergas, A.; Skorobogatov, G.; Solano, E.; Cantero, C.; Rodrigo, C. (2018-11-01). "A white dwarf catalogue from Gaia-DR2 and the Virtual Observatory". Monthly Notices of the Royal Astronomical Society. 480 (4): 4505–4518. arXiv:1807.02559. Bibcode:2018MNRAS.480.4505J. doi:10.1093/mnras/sty2120. ISSN 0035-8711.
- ^ Kilic, Mukremin; Bergeron, P.; Kosakowski, Alekzander; Brown, Warren R.; Agüeros, Marcel A.; Blouin, Simon (2020-07-01). "The 100 pc White Dwarf Sample in the SDSS Footprint". The Astrophysical Journal. 898 (1): 84. arXiv:2006.00323. Bibcode:2020ApJ...898...84K. doi:10.3847/1538-4357/ab9b8d. ISSN 0004-637X.
- ^ Brouwers, Marc G.; Buchan, Andrew M.; Bonsor, Amy; Malamud, Uri; Lynch, Elliot; Rogers, Laura; Koester, Detlev (2023-02-01). "Asynchronous accretion can mimic diverse white dwarf pollutants II: water content". Monthly Notices of the Royal Astronomical Society. 519 (2): 2663–2679. arXiv:2211.05113. Bibcode:2023MNRAS.519.2663B. doi:10.1093/mnras/stac3317. ISSN 0035-8711.
- ^ Payne, Matthew J.; Veras, Dimitri; Holman, Matthew J.; Gänsicke, Boris T. (2016-03-01). "Liberating exomoons in white dwarf planetary systems". Monthly Notices of the Royal Astronomical Society. 457 (1): 217–231. arXiv:1603.09344. Bibcode:2016MNRAS.457..217P. doi:10.1093/mnras/stv2966. ISSN 0035-8711.
- ^ Payne, Matthew J.; Veras, Dimitri; Gänsicke, Boris T.; Holman, Matthew J. (2017-01-01). "The fate of exomoons in white dwarf planetary systems". Monthly Notices of the Royal Astronomical Society. 464 (3): 2557–2564. arXiv:1610.01597. Bibcode:2017MNRAS.464.2557P. doi:10.1093/mnras/stw2585. ISSN 0035-8711.
- ^ Trierweiler, Isabella L.; Doyle, Alexandra E.; Melis, Carl; Walsh, Kevin J.; Young, Edward D. (2022-09-01). "Exomoons as Sources of White Dwarf Pollution". The Astrophysical Journal. 936 (1): 30. arXiv:2205.07935. Bibcode:2022ApJ...936...30T. doi:10.3847/1538-4357/ac86d5. ISSN 0004-637X.