WD 0137-349 is a
binary star
A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...
in the
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The first constellati ...
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-year
A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...
s (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, and ...
s) away, and appears exceedingly faint with an
apparent magnitude
Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...
of 15.33.
[
It is composed of a ]white dwarf
A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...
with a brown dwarf
Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main sequence, main-sequence stars. Their mass is approximately 13 to 80 Jupiter mass, times that of Jupiter ()not big en ...
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
* Period (punctuation)
* Era, a length or span of time
*Menstruation, commonly referred to as a "period"
Arts, entertainment, and media
* Period (music), a concept in musical composition
* Periodic sentence (o ...
of 116 minutes, or nearly 2 hours.[
]
Properties
The primary is a typical hydrogen
Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
white dwarf, as indicated by its spectral type of DA. It has about 39% of the Sun
The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
's mass and is only 1.86% as wide (12,900 km).[ With a high ]effective temperature
The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...
of 16,500 K, it emits radiation mostly in the ultraviolet
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
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 of ...
.[ 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.]T-type
T-Type was the performance marker used on Buick automobiles during the 1980s. Marketed during a hiatus of the Gran Sport branding, the T-Type vehicles were the sportiest versions of each Buick model line, in line with Super Sport-branded Chevro ...
brown dwarf, while the "day" side spectrum matches that of an early L-type brown dwarf.[ The brown dwarf is suspected to be a white dwarf or even a ]strange star
A strange star, also called a strange quark star, is a hypothetical compact astronomical object, a quark star made of strange quark matter.
Strange stars might exist without regard to the Bodmer–Witten assumption of stability at near-zero te ...
, 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
A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The stellar atmosphere, outer atmosphere is inflated and tenuous, making the radius large and the surface t ...
,[ 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 those with an outburst brightness visible to ...
.[
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 dwarf
A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...
s had been known to survive being enveloped during a red giant phase. It is thought that objects smaller than 20 Jupiter mass
The 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 ...
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 GD may refer to:
Arts and entertainment
* G-Dragon (born 1988), leader of the South Korean musical group Big Bang
* Grateful Dead, an American rock band
* Green Day, an American rock band
* ''Geometry Dash'', a side-scrolling music platforming v ...
, 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
*
*
{{DEFAULTSORT:WD 0137-349
White dwarfs
Brown dwarfs
L-type brown dwarfs
Spectroscopic binaries
Sculptor (constellation)
J01394284-3442393