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] /T [4] |
B−V color index | −0.02 |
Astrometry | |
Proper motion (μ) | RA: -42.059 [5] mas/yr Dec.: -48.895 [5] mas/yr |
Parallax (π) | 9.8472 ± 0.0367 mas [5] |
Distance | 331 ± 1 ly (101.6 ± 0.4 pc) |
Orbit [6] | |
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 | |
Mass | 0.39 ± 0.035 [6] M☉ |
Radius | 0.0186 ± 0.0012 [6] R☉ |
Luminosity | 0.023 ± 0.004 [6] L☉ |
Surface gravity (log g) | 7.49 ± 0.08 [6] cgs |
Temperature | 16500 ± 500 [6] K |
Age | 250 ± 80 [6] Myr |
WD 0137-349B | |
Mass | 0.053 ± 0.006 [2] M☉ |
Temperature | 1300 to 1400 [2] K |
Other designations | |
Database references | |
SIMBAD | A |
B |
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]
It is composed of a white dwarf with a brown dwarf in orbit around it, and is one of the few systems composed of a white dwarf and an associated brown dwarf. [6] The brown dwarf orbits with a period of 116 minutes, or nearly 2 hours. [6]
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). [6] With a high effective temperature of 16,500 K, it emits radiation mostly in the ultraviolet range. [8]
The brown dwarf, designated WD 0137-349B, can be detected from an infrared excess. [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. [8] The "night" side spectrum of WD 0137-349B therefore matches that of a mid-T-type brown dwarf, while the "day" side spectrum matches that of an early L-type brown dwarf. [4] The brown dwarf is suspected to be a white dwarf or even a strange star, as a hydrogen-dominated substellar object may be unstable in such a small orbit. [9]
The brown dwarf is known to have survived being engulfed when the primary star was a red giant, [6] because it was relatively massive. At that time, the red giant had a radius of 100 R☉. [10] 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. [11]
The orbit of the brown dwarf is slowly decaying. [6] 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. [6]
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. [11]
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 [12] was confirmed as a PCEB in 2011, five years later than WD 0137-349. [13]
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to Earth's. A white dwarf's low luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf. The nearest known white dwarf is Sirius B, at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name white dwarf was coined by Willem Jacob Luyten in 1922.
Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main-sequence stars. Their mass is approximately 13 to 80 times that of Jupiter (MJ)—not big enough to sustain nuclear fusion of ordinary hydrogen (1H) into helium in their cores, but massive enough to emit some light and heat from the fusion of deuterium (2H). The most massive ones can fuse lithium (7Li).
The Hyades is the nearest open cluster and one of the best-studied star clusters. Located about 153 light-years away from the Sun, it consists of a roughly spherical group of hundreds of stars sharing the same age, place of origin, chemical characteristics, and motion through space. From the perspective of observers on Earth, the Hyades Cluster appears in the constellation Taurus, where its brightest stars form a "V" shape along with the still-brighter Aldebaran. However, Aldebaran is unrelated to the Hyades, as it is located much closer to Earth and merely happens to lie along the same line of sight.
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The Beehive Cluster, is an open cluster in the constellation Cancer. One of the nearest open clusters to Earth, it contains a larger population of stars than other nearby bright open clusters holding around 1,000 stars. Under dark skies, the Beehive Cluster looks like a small nebulous object to the naked eye, and has been known since ancient times. Classical astronomer Ptolemy described it as a "nebulous mass in the breast of Cancer". It was among the first objects that Galileo studied with his telescope.
Zeta Cygni is a binary star system in the northern constellation of Cygnus, the swan. It has an apparent visual magnitude of 3.26 and, based upon parallax measurements, is about 143 light-years away.
Blanco 1 is a nearby open cluster of stars located around 850 light years away from the Sun in the southern constellation of Sculptor near the star ζ Sculptoris. It was discovered by Puerto Rican astronomer Víctor Manuel Blanco in 1949, who noticed an unusually high proportion of A-type stars in an area spanning 1.5°. This cluster is relatively young, with an age of about 100–150 million years. It is positioned at a high galactic latitude of b = –79.3° and is located some 780 ly (240 pc) below the galactic plane.
GD 165 is a binary white dwarf and brown dwarf system located in the Boötes constellation, roughly 109 light-years from Earth. Neither of the stars have any known exoplanets.
2MASS J03552337+1133437 is a nearby brown dwarf of spectral type L5γ, located in constellation Taurus at approximately 29.8 light-years from Earth.
RR Caeli is an eclipsing binary star system, located 69 light-years from Earth in the constellation Caelum. It is made up of a red dwarf star and a white dwarf, which complete an orbit around each other every seven hours. There is evidence of two circumbinary planets orbiting even further away.
WD 1145+017 is a white dwarf approximately 476 light-years from Earth in the constellation of Virgo. It is the first white dwarf to be observed with a transiting minor planet orbiting it.
A post-common envelope binary (PCEB) or pre-cataclysmic variable is a binary system consisting of a white dwarf or hot subdwarf and a main-sequence star or a brown dwarf. The star or brown dwarf shared a common envelope with the white dwarf progenitor in the red giant phase. In this scenario the star or brown dwarf loses angular momentum as it orbits within the envelope, eventually leaving a main-sequence star and white dwarf in a short-period orbit. A PCEB will continue to lose angular momentum via magnetic braking and gravitational waves and will eventually begin mass-transfer, resulting in a cataclysmic variable. While there are thousands of PCEBs known, there are only a few eclipsing PCEBs, also called ePCEBs. Even more rare are PCEBs with a brown dwarf as the secondary. A brown dwarf with a mass lower than 20 MJ might evaporate during the common envelope phase and therefore the secondary is supposed to have a mass higher than 20 MJ.
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