WD 0137-349 is a
binary star in the
constellation of
Sculptor
Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable sc ...
. It is located about 330
light-years (100
parsec
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, an ...
s) away, and appears exceedingly faint with an
apparent magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...
of 15.33.
[
It is composed of a ]white dwarf
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 the Earth's. A white dwarf's faint luminosity comes ...
with a brown dwarf
Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen ( 1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most ...
in orbit around it, and is one of the few systems composed of a white dwarf and an associated brown dwarf.[ The brown dwarf orbits with a ]period
Period may refer to:
Common uses
* Era, a length or span of time
* Full stop (or period), a punctuation mark
Arts, entertainment, and media
* Period (music), a concept in musical composition
* Periodic sentence (or rhetorical period), a concept ...
of 116 minutes, or nearly 2 hours.[
]
Properties
The primary is a typical hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
white dwarf, as indicated by its spectral type of DA. It has about 39% of the Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
's mass and is only 1.86% as wide (12,900 km).[ With a high effective temperature of 16,500 K, it emits radiation mostly in the ]ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...
range.[
The brown dwarf, designated WD 0137-349B, can be detected from an ]infrared excess
An infrared excess is a measurement of an astronomical source, typically a star, that in their spectral energy distribution has a greater measured infrared flux than expected by assuming the star is a blackbody radiator. Infrared excesses are oft ...
.[ 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.][ 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.
]
Evolution
The brown dwarf is known to have survived being engulfed when the primary star was a red giant,[ because it was relatively massive. At that time, the red giant had a radius of .][
The orbit of the brown dwarf is slowly decaying.][ 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
In astronomy, cataclysmic variable stars (CVs) are stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state. They were initially called novae (), since ones with an outburst brightness visible t ...
.[
As of 2006, this is the coldest known companion to a white dwarf.][ 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 mass
Jupiter mass, also called Jovian mass, is the unit of mass equal to the total mass of the planet Jupiter. This value may refer to the mass of the planet alone, or the mass of the entire Jovian system to include the moons of Jupiter. Jupiter is by ...
es would have evaporated.
Post common envelope white dwarf-brown dwarf binaries
WD 0137-349 represents the first confirmed post common envelope binary
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 prog ...
(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 was confirmed as a PCEB in 2011, five years later than WD 0137-349.
References
External links
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{{DEFAULTSORT:WD 0137-349
White dwarfs
Brown dwarfs
L-type stars
Spectroscopic binaries
Sculptor (constellation)
J01394284-3442393