LP 40-365
Tangential movement of LP 40-365 between 1955 and 1995. The field of view is 8 × 8 arcminutes. Credit: Digitized Sky Survey | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Minor |
| Right ascension | 14h 06m 35.45s[1] |
| Declination | +74° 18′ 58.0″[1] |
| Apparent magnitude (V) | 15.51 ± 0.09[2] |
| Characteristics | |
| Spectral type | D[2] |
| Astrometry | |
| Radial velocity (Rv) | 498[2] km/s |
| Total velocity | ~546[2] km/s |
| Proper motion (μ) | RA: −49.569±0.029 mas/yr[3] Dec.: 148.642±0.029 mas/yr[3] |
| Parallax (π) | 1.6375±0.0257 mas[3] |
| Distance | 1,990 ± 30 ly (611 ± 10 pc) |
| Absolute magnitude (MV) | 8.14+0.60 −0.90[2] |
| Details[4] | |
| Mass | 0.28+0.28 −0.14 M☉ |
| Radius | 0.16±0.01 R☉ |
| Surface gravity (log g) | 5.50±0.30 cgs |
| Temperature | 9800±300 K |
| Rotation | 8.914122 ± 0.000020 hours[5] |
| Rotational velocity (v sin i) | 30.5 ± 2.0[2] km/s |
| Other designations | |
| 2MASS J14063545+7418579[6] | |
| Database references | |
| SIMBAD | data |
LP 40-365 is a low-mass white dwarf star in the constellation Ursa Minor. It travels at high speed through the Milky Way and has a very unusual elemental composition, lacking hydrogen, helium or carbon. It may have been produced in a subluminous Type Iax supernova that failed to destroy its host star totally.[2][7][8] The "LP" name is derived from the Luyten-Palomar proper motion catalogue in which it appeared in the 1960s.[9] Another catalog name for this star is "GD 492".[6] The star was cataloged as a Giclas object with the designation "GD 492" being assigned by Henry Giclas in 1970.[10]
The abundance analysis of LP 40-365 did show that the atmosphere is dominated by oxygen and neon, with substantial traces of intermediate-mass elements such as aluminium and silicon. The white dwarf core on the other hand is likely composed of a mix of carbon, oxygen and neon.[2] Additional observations did suggest the atmosphere is dominated by helium. This is in contrast to the previous analysis.[11] Later helium was excluded with high quality spectra for other similar stars and therefore a oxygen-neon dominated atmosphere is favoured for LP 40-365. Neon has the highest mass fraction of below 60%, oxygen has a mass fraction of around 30%, followed by around 8% of magnesium.[nb 1] 11 other elements are detected in the atmosphere, but they make up 1–2% of the mass. The atmospheric composition is a strong indicator of partial carbon-, oxygen- and silicon-burning, likely connected to a thermonuclear explosion that did not entirely disrupt the progenitor. The origin could be either a peculiar Type Iax or electron-capture supernova. In the future LP 40-365 and similar objects are predicted to evolve into oxygen-rich white dwarfs.[4]
The new parallax with Gaia helped to refine the radius to 18% of the radius of the Sun. This is 15 times larger than other white dwarfs. The new kinematic analysis showed that LP 40-365 is leaving the Milky Way with 1.5 times the escape velocity of the solar neighbourhood. The object crossed the galactic disk 5.3±0.5 Ma ago in the direction of Carina, likely coming from beneath the plane. The team estimated that it was ejected with a speed of 600 km/s from its progenitor binary. This speed suggests a close binary consisting of a white dwarf and a helium-star donor. This donor-star had a mass of 0.8 to 1.32 M☉ and the binary had an orbital period of 30 to 60 minutes. Today LP 40-365 has a rest-frame velocity of 852±10 km/s.[12] Variability was detected with the help of TESS, Hubble and WISE. TESS in the optical showed an amplitude of 1.0%, Hubble in the ultraviolet showed an amplitude of 5.8% and WISE in the infrared shows an amplitude of around 2.2%. The rotation period was measured at 8.914 hours. The researchers suggest the variations are caused by an inhomogeneity on the surface, rotating in and out of view.[5]
Additional stars with similar characteristics are called LP 40-365 stars, making LP 40-365 the prototype of chemically peculiar runaway stars that are the survivors of thermonuclear explosions.[4]
Notes
- ^ These values are measured from figure 13 and are therefore less accurate. General values for LP 40-365-like stars are given in section 5.1.2: Ne (59–65%), O (29–31%), Mg (3–9%).
References
- ^ a b Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
- ^ a b c d e f g h Vennes, Stephane; Nemeth, Peter; Kawka, Adela; Thorstensen, John R.; Khalack, Viktor; Ferrario, Lilia; Alper, Erek H. (18 August 2017). "An unusual white dwarf star may be a surviving remnant of a subluminous Type Ia supernova". Science. 357 (6352): 680–683. arXiv:1708.05568. Bibcode:2017Sci...357..680V. doi:10.1126/science.aam8378. PMID 28818942. S2CID 24141207.
- ^ a b 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 Raddi, R.; Hollands, M. A.; Koester, D.; Hermes, J. J.; Gaensicke, B. T.; Heber, U.; Shen, K. J.; Townsley, D. M.; Pala, A. F. (2019-06-07). "Partly burnt runaway stellar remnants from peculiar thermonuclear supernovae". MNRAS. 489 (2): 1489–1508. arXiv:1902.05061. Bibcode:2019MNRAS.489.1489R. doi:10.1093/mnras/stz1618. Retrieved 2026-03-02.
- ^ a b Hermes, J. J.; Putterman, Odelia; Hollands, Mark A.; Wilson, David J.; Swan, Andrew; Raddi, Roberto; Shen, Ken J.; Gänsicke, Boris T. (2021-06-01). "8.9 hr Rotation in the Partly Burnt Runaway Stellar Remnant LP 40-365 (GD 492)". The Astrophysical Journal Letters. 914 (1): L3. arXiv:2105.06480. Bibcode:2021ApJ...914L...3H. doi:10.3847/2041-8213/ac00a8. ISSN 2041-8205.
- ^ a b "GD 492". SIMBAD. Centre de données astronomiques de Strasbourg.
- ^ "Science Press Release". Astroserver.org. Retrieved 17 August 2017.
- ^ Javier Barbuzano (17 August 2017). "The White Dwarf That Survived". Sky & Telescope.
- ^ Luyten, W. J. (1963–1981). "Proper Motion Survey with the 48 inch Schmidt Telescope". University of Minnesota.
- ^ Giclas, Henry L.; Burnham, Robert; Thomas, Norman Gene (1970). "A list of white dwarf suspects III : Special objects of small proper motion from the Lowell survey". Bulletin of the Lowell Observatory. 7 (153): 183. Bibcode:1970LowOB...7..183G.
- ^ Raddi, R.; Hollands, M. A.; Koester, D.; Gänsicke, B. T.; Fusillo, N. P. Gentile; Hermes, J. J.; Townsley, D. M. (2018-04-26). "Further Insight on the Hypervelocity White Dwarf, LP 40–365 (GD 492): A Nearby Emissary from a Single-degenerate Type Ia Supernova". The Astrophysical Journal. 858 (1): 3. arXiv:1803.07564. Bibcode:2018ApJ...858....3R. doi:10.3847/1538-4357/aab899. ISSN 0004-637X.
- ^ Raddi, R.; Hollands, M. A.; Gaensicke, B. T.; Townsley, D. M.; Hermes, J. J.; Fusillo, N. P. Gentile; Koester, D. (2018-06-08). "Anatomy of the hyper-runaway star LP 40-365 with Gaia". MNRAS: Letters. 479 (1): L96–L101. arXiv:1804.09677. Bibcode:2018MNRAS.479L..96R. doi:10.1093/mnrasl/sly103. Retrieved 2026-03-02.