WD 0137−349

WD 0137-349 is a binary star in the constellation of Sculptor. It is located about 330 light-years (100 parsecs) away, and appears exceedingly faint with an apparent magnitude of 15.33.[2]

WD 0137-349
Observation data
Epoch J2000      Equinox J2000
Constellation Sculptor
Right ascension 01h 39m 42.847s[1]
Declination −34° 42′ 39.32″[1]
Apparent magnitude (V) +15.33 ± 0.02[2]
Characteristics
Spectral type DA[3] + L8[2]
B−V color index −0.02
Astrometry
Proper motion (μ) RA: -42.059[4] mas/yr
Dec.: -48.895[4] mas/yr
Parallax (π)9.8472 ± 0.0367[4] mas
Distance331 ± 1 ly
(101.6 ± 0.4 pc)
Orbit[5]
Period (P)0.0803 ± 0.0002
Semi-major axis (a)0.65 R☉
Periastron epoch (T)2453686.5276 ± 0.0001
Semi-amplitude (K1)
(primary)		27.9 ± 0.3 km/s
Semi-amplitude (K2)
(secondary)		−187.5 ± 1.1 km/s
Details
WD 0137-349A
Mass0.39 ± 0.035[5] M☉
Radius0.0186 ± 0.0012[5] R☉
Luminosity0.023 ± 0.004[5] L☉
Surface gravity (log g)7.49 ± 0.08[5] cgs
Temperature16500 ± 500[5] K
Age250 ± 80[5] Myr
WD 0137-349B
Mass0.053 ± 0.006[2] M☉
Temperature1300 to 1400[2] K
Other designations
2MASS J01394284-3442393, BPS CS 29504-0036[6]
Database references
SIMBADA
B

It is composed of a white dwarf and a brown dwarf in orbit around it, and it one of the few systems to a white dwarf and an associated brown dwarf.[5] The brown dwarf orbits with a period of 116 minutes, or nearly 2 hours.[5]

Properties

The primary is a typical hydrogen white dwarf, as indicated by its spectral type of DA. It has about 39% of the Sun's mass and is only 1.86% as wide (12,900 km).[5] With a high effective temperature of 16,500 K, it emits radiation mostly in the ultraviolet range.[7]

The brown dwarf, designated WD 0137-349B, can be detected from an infrared excess, and is a late L-type object.[2] Although it glows with an effective temperature of 1300 to 1400 K, the side facing the white dwarf's intercepts 1% of its light, and heats it up to around 2000 K.[7] The brown dwarf is suspected to be a white dwarf or even a strange star, as hydrogen-dominated substellar object may be unstable on such a small orbit.[8]

Evolution

The brown dwarf is known to have survived being engulfed when the primary star was a red giant,[5] because it was relatively massive. At that time, the red giant had a radius of 100 R☉.[9] It is thought that the red giant phase of the current white dwarf was shortened from around 100 million years on average, to a few decades—while the brown dwarf was within the red giant, it hastened the expulsion of matter during this phase by rapidly heating gas and accreting a portion of it. During this phase, drag from the red giant also decreased the orbital speed of the brown dwarf, causing it to fall inwards.[10]

The orbit of the brown dwarf is slowly decaying.[5] In about 1.4 billion years, it is thought that the orbit of the brown dwarf will have decayed sufficiently to allow the white dwarf to draw matter away and accrete it on its surface, leading to a cataclysmic variable.[5]

As of 2006, this is the coldest known companion to a white dwarf.[2] This brown dwarf was also the object with the lowest mass known to have survived being engulfed by a red giant. Previously, only red dwarfs had been known to survive being enveloped during a red giant phase. It is thought that objects smaller than 20 Jupiter masses would have evaporated.[10]

Post common envelope white dwarf-brown dwarf binaries

WD 0137-349 represents the first confirmed post common envelope binary (PCEB) containing a white dwarf and a brown dwarf. As of 2018 only 8 of these wd+bd PCEBs are known. The first with a confirmed spectral type was GD 1400, but this second confirmed wd+bd binary after GD 165B[11] was confirmed as a PCEB in 2011, five years later than WD 0137-349.[12]

References
  1. Cutri, R. M.; et al. (2003). "2MASS All-Sky Catalog of Point Sources". VizieR On-line Data Catalog. 2246. Bibcode:2003yCat.2246....0C.
  2. Burleigh, M. R.; Hogan, E.; Dobbie, P. D.; Napiwotzki, R.; Maxted, P. F. L. (2006). "A near-infrared spectroscopic detection of the brown dwarf in the post common envelope binary WD 0137-349". Monthly Notices of the Royal Astronomical Society: Letters. 373 (1): L55–L59. arXiv:astro-ph/0609366. Bibcode:2006MNRAS.373L..55B. doi:10.1111/j.1745-3933.2006.00242.x. S2CID 16186119.
  3. Koester, D.; Voss, B.; Napiwotzki, R.; Christlieb, N.; Homeier, D.; Lisker, T.; Reimers, D.; Heber, U. (2009). "High-resolution UVES/VLT spectra of white dwarfs observed for the ESO SN Ia Progenitor Survey" (PDF). Astronomy and Astrophysics. 505: 441–462. arXiv:0908.2322. Bibcode:2009A&A...505..441K. doi:10.1051/0004-6361/200912531. S2CID 10435049.
  4. Brown, A. G. A.; et al. (Gaia collaboration). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics (in press). arXiv:2012.01533. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
  5. Maxted, P. F. L.; Napiwotzki, R.; Dobbie, P. D.; Burleigh, M. R. (2006). "Survival of a brown dwarf after engulfment by a red giant star". Nature. 442 (7102): 543–5. arXiv:astro-ph/0608054. Bibcode:2006Natur.442..543M. doi:10.1038/nature04987. PMID 16885979. S2CID 4368344.
  6. "BPS CS 29504-0036". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 16 April 2017.
  7. Casewell, S. L.; Lawrie, K. A.; Maxted, P. F. L.; Marley, M. S.; Fortney, J. J.; Rimmer, P. B.; Littlefair, S. P.; Wynn, G.; Burleigh, M. R.; Helling, C. (2015). "Multiwaveband photometry of the irradiated brown dwarf WD0137-349B". Monthly Notices of the Royal Astronomical Society. 447 (4): 3218. arXiv:1412.6363. Bibcode:2015MNRAS.447.3218C. doi:10.1093/mnras/stu2721. S2CID 46597477.
  8. Close-in Exoplanets as Candidates of Strange Quark Matter Objects, 2019, arXiv:1908.11191
  9. Passy, Jean-Claude; Mac Low, Mordecai-Mark; De Marco, Orsola (2012). "On the Survival of Brown Dwarfs and Planets Engulfed by Their Giant Host Star". The Astrophysical Journal. 759 (2): L30. arXiv:1210.0879. Bibcode:2012ApJ...795L..30P. doi:10.1088/2041-8205/759/2/L30. S2CID 118657091.
  10. Ker Than (2 August 2006). "Object Survives Being Swallowed by a Star". Space.com. Retrieved 19 April 2017.
  11. Farihi, J.; Christopher, M. (October 2004). "A Possible Brown Dwarf Companion to the White Dwarf GD 1400". The Astronomical Journal. 128 (4): 1868–1871. arXiv:astro-ph/0407036. Bibcode:2004AJ....128.1868F. doi:10.1086/423919. ISSN 0004-6256. S2CID 119530628.
  12. Casewell, S. L.; Braker, I. P.; Parsons, S. G.; Hermes, J. J.; Burleigh, M. R.; Belardi, C.; Chaushev, A.; Finch, N. L.; Roy, M.; Littlefair, S. P.; Goad, M. (2018-05-01). "The first sub-70 minute non-interacting WD-BD system: EPIC212235321". Monthly Notices of the Royal Astronomical Society. 476 (1): 1405–1411. arXiv:1801.07773. Bibcode:2018MNRAS.476.1405C. doi:10.1093/mnras/sty245. ISSN 0035-8711.
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