WD 1856+534 is a white dwarf located in the constellation of Draco. At a distance of about 25 parsecs (80 ly) from Earth, it is the outer component of a visual triple star system consisting of an inner pair of red dwarf stars, named G 229-20. The white dwarf displays a featureless absorption spectrum, lacking strong optical absorption or emission features in its atmosphere. It has an effective temperature of 4,700 K (4,430 °C; 8,000 °F), corresponding to an age of approximately 5.8 billion years.[4] WD 1856+534 is approximately half as massive as the Sun, while its radius is much smaller, being 40% larger than Earth.[5]
.jpg) Artist's impression of WD 1856+534 and its planet. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Draco |
| WD 1856+534 | |
| Right ascension | 18h 57m 39.34s[1] |
| Declination | +53° 30′ 33.30″[1] |
| Apparent magnitude (V) | 17.244±0.046[2] |
| G 229-20 A | |
| Right ascension | 18h 57m 38.4s[2] |
| Declination | 53° 31′ 14.43″[2] |
| Apparent magnitude (V) | 13.15[2] |
| G 229-20 B | |
| Right ascension | 18h 57m 38.33s[2] |
| Declination | 53° 31′ 12.24″[2] |
| Apparent magnitude (V) | 13.23[2] |
| Characteristics | |
| WD 1856+534 | |
| Evolutionary stage | white dwarf |
| Spectral type | DA[3] |
| Apparent magnitude (J) | 15.677±0.055[1] |
| Apparent magnitude (H) | 15.429±0.094[1] |
| Apparent magnitude (K) | 15.548±0.186[1] |
| Astrometry | |
| Proper motion (μ) | RA: −240.759±0.148[1] mas/yr Dec.: −52.514±0.143[1] mas/yr |
| Parallax (π) | 40.3983±0.0705[1] mas |
| Distance | 80.737±0.144 ly (24.754±0.044[4] pc) |
| G 299-20 A | |
| Proper motion (μ) | RA: 256.12 mas/yr[2] Dec.: -52.72 mas/yr[2] |
| Parallax (π) | 40.298 ± 0.024 mas[2] |
| Distance | 80.94 ± 0.05 ly (24.82 ± 0.01 pc) |
| G 299-20 B | |
| Proper motion (μ) | RA: 241.4[2] mas/yr[2] Dec.: -44.176 mas/yr[2] |
| Parallax (π) | 40.33 ± 0.024 mas[2] |
| Distance | 80.87 ± 0.05 ly (24.80 ± 0.01 pc) |
| Details[3] | |
| WD 1856+534 | |
| Mass | 0.576±0.040 M☉ |
| Radius | 0.01263±0.00050 R☉ |
| Surface gravity (log g) | 7.995±0.065 cgs |
| Temperature | 4860±60 K |
| Metallicity [Fe/H] | <−8.8[4] dex |
| Age | 6.60±0.48 Gyrs (cooling age) 8 to 10 (total age) Gyr |
| G 299-20 A[4] | |
| Mass | 0.335±0.024 M☉ |
| Radius | 0.35±0.02 R☉ |
| Temperature | 3,521 K |
| G 299-20 B[4] | |
| Mass | 0.322±0.023 M☉ |
| Radius | 0.34±0.02 R☉ |
| Temperature | 3,513 K |
| Position (relative to G 229-20)[4] | |
| Angular distance | ~43″ |
| Projected separation | 1030+130 −55 AU [4] |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
Planetary system
editThe white dwarf is known to host one exoplanet, WD 1856+534 b, in orbit around it. The exoplanet was detected through the transit method by the Transiting Exoplanet Survey Satellite (TESS) between July and August 2019. An analysis of the transit data in 2020 revealed that it is a Jupiter-like giant planet with a radius over ten times that of Earth's, and orbits its host star closely at a distance of 0.02 astronomical units (AU), with an orbital period 60 times shorter than that of Mercury around the Sun.
The unexpectedly close distance of the exoplanet to the white dwarf implies that it must have migrated inward after its host star evolved from a red giant to a white dwarf, otherwise it would have been engulfed by its star.[4] This migration may be related to the fact that WD 1856+534 belongs to a hierarchical triple-star system: the white dwarf and its planet are gravitationally bound to a distant companion, G 229–20, which itself is a binary system of two red dwarf stars.[4] Gravitational interactions with the companion stars may have triggered the planet's migration through the Lidov–Kozai mechanism[6][7][8] in a manner similar to some hot Jupiters. An alternative hypothesis is that the planet instead has survived a common envelope phase.[9] In the latter scenario, other planets engulfed before may have contributed to the expulsion of the stellar envelope.[10] JWST observations seem to disfavour the formation via common envelope and instead favour high eccentricity migration.[11]
The planetary transmission spectrum obtained with GTC OSIRIS is gray and featureless, likely because of the high level of hazes.[12] The transmission spectrum was also obtained with Gemini GMOS. It does not show any features beside a possible dip at 0.55 μm. This feature could be caused be auroral emission at the nightside of the planet. The research find a minimum mass of 0.84 MJ by accounting for the transit geometry of a grazing transit. The researchers also revised the white dwarf parameters and found a total age of 8-10 billion years, in agreement with the system belonging to the thin disk.[3]
A search with transit timing variations found no additional planets. The search exclude planets with a mass more than 2 MJ with orbital periods as long as 500 days and planets with >10 MJ with orbital periods as long as 1000 days.[13]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 2.4-13.8[12] or >0.84[3] MJ | 0.0204±0.0012 | 1.40793925±0.00000004[3] | ~0 | 88.778±0.059° | 0.966+0.040 −0.039[3][nb 1] RJ |
See also
edit- WD 1145+017, a white dwarf with a transiting disrupted planetary-mass object
- WD J0914+1914, a white dwarf with a disk of debris originating from a possible giant planet
- ZTF J0139+5245, another white dwarf with a disk of debris from a disrupted planetary-mass object
- CWISEP J1935-1546 a free-floating object with aurora emission in the infrared
- List of exoplanets and planetary debris around white dwarfs
Notes
edit- ^ Calculated using the Radius ratio in table 4 and the white dwarf radius in table 3, convertion into jupiter radius using 1 R☉ is 0.1028 RJ, see solar radius
References
edit- ^ a b c d e f g h "LP 141-14 -- White Dwarf". SIMBAD. Université de Strasbourg. Retrieved 20 September 2020.
- ^ a b c d e f g h i j k l "WD 1856+534 Overview". NASA Exoplanet Archive.
- ^ a b c d e f Xu, Siyi; Diamond-Lowe, Hannah; MacDonald, Ryan J.; Vanderburg, Andrew; Blouin, Simon; Dufour, P.; Gao, Peter; Kreidberg, Laura; Leggett, S. K.; Mann, Andrew W.; Morley, Caroline V.; Stephens, Andrew W.; O'Connor, Christopher E.; Thao, Pa Chia; Lewis, Nikole K. (2021-12-01). "Gemini/GMOS Transmission Spectroscopy of the Grazing Planet Candidate WD 1856+534 b". The Astronomical Journal. 162 (6): 296. arXiv:2110.14106. Bibcode:2021AJ....162..296X. doi:10.3847/1538-3881/ac2d26. ISSN 0004-6256.
- ^ a b c d e f g h i j Vanderburg, Andrew; Rappaport, Saul A.; Xu, Siyi; Crossfield, Ian J. M.; Becker, Juliette C.; Gary, Bruce; et al. (September 2020). "A giant planet candidate transiting a white dwarf". Nature. 585 (7825): 363–367. arXiv:2009.07282. Bibcode:2020Natur.585..363V. doi:10.1038/s41586-020-2713-y. PMID 32939071. S2CID 221738865.
- ^ Potter, Steve (16 September 2020). "NASA Missions Spy First Possible 'Survivor' Planet Hugging White Dwarf Star". NASA. 20-086. Retrieved 20 September 2020.
- ^ Muñoz, Diego J.; Petrovich, Cristobal (2020-11-19). "Kozai Migration Naturally Explains the White Dwarf Planet WD1856b". The Astrophysical Journal. 904 (1): L3. arXiv:2010.04724. Bibcode:2020ApJ...904L...3M. doi:10.3847/2041-8213/abc564. ISSN 2041-8213. S2CID 222290559.
- ^ O'Connor, Christopher E.; Liu, Bin; Lai, Dong (2020-11-30). "Enhanced Lidov-Kozai migration and the formation of the transiting giant planet WD1856+534b". Monthly Notices of the Royal Astronomical Society. 501: 507–514. arXiv:2010.04163. doi:10.1093/mnras/staa3723. ISSN 0035-8711. S2CID 222272242.
- ^ Stephan, Alexander P.; Naoz, Smadar; Gaudi, B. Scott (2021). "Giant Planets, Tiny Stars: Producing Short-period Planets around White Dwarfs with the Eccentric Kozai–Lidov Mechanism". The Astrophysical Journal. 922 (1): 4. arXiv:2010.10534. Bibcode:2021ApJ...922....4S. doi:10.3847/1538-4357/ac22a9. S2CID 224819085.
- ^ Lagos, F.; Schreiber, M. R.; Zorotovic, M.; Gänsicke, B. T.; Ronco, M. P.; Hamers, Adrian S. (2021), "WD 1856 b: a close giant planet around a white dwarf that could have survived a common-envelope phase", Monthly Notices of the Royal Astronomical Society, 501 (1): 676–682, arXiv:2010.09747, Bibcode:2021MNRAS.501..676L, doi:10.1093/mnras/staa3703, S2CID 224802868
- ^ Chamandy, Luke; Blackman, Eric G.; Nordhaus, Jason; Wilson, Emily (2021), "Successive common envelope events from multiple planets", Monthly Notices of the Royal Astronomical Society: Letters, 502: L110–L114, arXiv:2011.11106, doi:10.1093/mnrasl/slab017
- ^ O'Connor, Christopher; Lai, Dong; MacDonald, Ryan; The JWST WD1856b Team (2024-08-01). "The thermal evolution of WD1856b reveals its migration history". AAS Division on Dynamical Astronomy Meeting #55, Id. 401.01. 56 (6): 401.01. Bibcode:2024DDA....5540101O.
{{cite journal}}: CS1 maint: numeric names: authors list (link) - ^ a b Alonso, R.; Rodríguez-Gil, P.; Izquierdo, P.; Deeg, H. J.; Lodieu, N.; Cabrera-Lavers, A.; Hollands, M. A.; Pérez-Toledo, F. M.; Castro-Rodríguez, N.; Reverte-Payá, D. (2021), "A transmission spectrum of the planet candidate WD 1856+534 b and a lower limit to its mass", Astronomy & Astrophysics, 649: A131, arXiv:2103.15720, Bibcode:2021A&A...649A.131A, doi:10.1051/0004-6361/202140359, S2CID 232417057
- ^ Kubiak, Sarah; Vanderburg, Andrew; Becker, Juliette; Gary, Bruce; Rappaport, Saul A.; Xu, Siyi; de Beurs, Zoe (2023-05-01). "TTV constraints on additional planets in the WD 1856+534 system". Monthly Notices of the Royal Astronomical Society. 521 (3): 4679–4694. arXiv:2303.06157. Bibcode:2023MNRAS.521.4679K. doi:10.1093/mnras/stad766. ISSN 0035-8711.
External links
edit- NASA Missions Spy First Possible ‘Survivor’ Planet Hugging White Dwarf Star, Sean Potter, NASA, 16 September 2020
- Planet discovered transiting a dead star, Steven Parsons, Nature News and Views, 16 September 2020