Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Aquarius |
Right ascension | 22h 20m 30.6964s |
Declination | −00° 41′ 07.4740″ |
Characteristics | |
Evolutionary stage | white dwarf + brown dwarf |
Spectral type | DAZ + L8-L9 |
Apparent magnitude (G) | 17.327 ±0.003 |
Apparent magnitude (J) | 16.745 ±0.017 |
Apparent magnitude (H) | 16.444 ±0.025 |
Apparent magnitude (K) | 16.36 ±0.04 |
Astrometry | |
Radial velocity (Rv) | 52 ±5 km/s |
Proper motion (μ) | RA: -47.771 ±0.111 mas/yr [1] Dec.: -171.029 ±0.097 mas/yr [1] |
Parallax (π) | 13.6148 ± 0.1083 mas [1] |
Distance | 240 ± 2 ly (73.4 ± 0.6 pc) |
Orbit [2] | |
Primary | PHL 5038A |
Companion | PHL 5038B |
Semi-major axis (a) | 66+12 −24 AU |
Eccentricity (e) | <0.615 |
Inclination (i) | 132 ±11° |
Details [2] | |
PHL 5038A | |
Mass | 0.53 ±0.02 M☉ |
Surface gravity (log g) | 7.89 ±0.02 cgs |
Temperature | 7525 ±25 K |
Age | 10.26+3.09 −3.61 Gyr |
PHL 5038B | |
Mass | 73 MJup |
Surface gravity (log g) | 5.454 cgs |
Temperature | 1425 K |
Age | 10.26+3.09 −3.61 Gyr |
Other designations | |
Database references | |
SIMBAD | data |
PHL 5038AB (or just PHL 5038) is a binary system consisting out of a white dwarf and a brown dwarf on a wide orbit. The system is 240 light years (74 parsec) distant from earth.
The white dwarf PHL 5038A was discovered in 2006 in data from the Sloan Digital Sky Survey [3] and the brown dwarf companion was discovered in 2009 from UKIDSS infrared excess and confirmed with Gemini North to be a spacially resolved binary. [4] It was only the fourth known brown dwarf to orbit a white dwarf at the time. The others were GD 165B, WD 0137-349B and GD 1400B. [2]
The white dwarf was first classified as a DA white dwarf, which indicates a hydrogen-dominated atmosphere without any metal pollution. [4] A later work found weak pollution due to calcium in the atmosphere of the white dwarf thanks to XSHOOTER spectra from the Very Large Telescope. The calcium is detected as the K-line in two spectra. No infrared excess due to a disk was detected. PHL 5038A has either accreted all debris or is surrounded by a thin disk. The mass and temperature was also overestimated in the past and later works found a mass of around 0.53 to 0.57 M☉, an effective temperature of around 7500 to 7800 Kelvin and a surface gravity of around 7.9 dex. The progenitor main-sequence star had a mass of around 1.07 M☉ and it existed for around 9 billion years until it became an AGB star and around 1 billion years ago it became a white dwarf. [2]
The brown dwarf has a spectral type of around L8-L9. Its mass was initially estimated to be 60 MJ, [4] but this mass was likely an underestimate and more recent estimates find a mass of around 0.070 M☉ (or 73 MJ) and an effective temperature of 1425 K. [2]
The same team that discovered the metal pollution of the white dwarf also re-observed the system with Gemini North to determine the orbital parameters. The semi-major axis is 66+12
−24 astronomical units and the inclination is 132 ±11°. The eccentricity is unconstrained, but likely lower than 0.615. In the past the white dwarf was more massive, making the semi-major axis half as large at 33 AU. [2]
Casewell et al. suggest the following evolution of the system:
The PHL 5038 system during the main-sequence had a star with a mass similar or more massive than the sun and it had a brown dwarf at an orbit of 33 AU, similar to the orbital distance of Neptune. It also likely had rocky debris in the form of planetesimals in orbit around the star, maybe similar to the asteroid belt. At the end of its lifetime the star became an AGB star with a size smaller than 2.5 AU, leaving the rocky debris mostly intact. As the star lost around half of its mass, the orbit of the brown dwarf and the planetesimals increased. The debris would be stable within 17-32 AU (circular orbit of the brown dwarf) or 5-8 AU (e=0.6 for the brown dwarf orbit). A debris belt with an increased size might be close to the edge of this stable zone and gravitational interactions with the brown dwarf would scatter planetesimals into all kinds of directions, eroding the edge of the debris belt. Some of these planetesimals will be scattered inwards and are being disrupted by the tidal forces of the white dwarf, leading to the pollution of the white dwarf atmosphere. Alternatively the disk could have been larger than the stable zone, resulting in chaotic scattering at the beginning of the white dwarf stage, until the scattering decreased. [2]
Epsilon Indi, Latinized from ε Indi, is a star system located at a distance of approximately 12 light-years from Earth in the southern constellation of Indus. The star has an orange hue and is faintly visible to the naked eye with an apparent visual magnitude of 4.674. It consists of a K-type main-sequence star, ε Indi A, and two brown dwarfs, ε Indi Ba and ε Indi Bb, in a wide orbit around it. The brown dwarfs were discovered in 2003. ε Indi Ba is an early T dwarf (T1) and ε Indi Bb a late T dwarf (T6) separated by 0.6 arcseconds, with a projected distance of 1460 AU from their primary star.
Van Maanen 2, or van Maanen's Star, is the closest known solitary white dwarf to the Solar System. It is a dense, compact stellar remnant no longer generating energy and has equivalent to about 68% of the Sun's mass but only 1% of its radius. At a distance of 14.1 light-years it is the third closest of its type of star after Sirius B and Procyon B, in that order. Discovered in 1917 by Dutch–American astronomer Adriaan van Maanen, Van Maanen 2 was the third white dwarf identified, after 40 Eridani B and Sirius B, and the first solitary example.
HD 107146 is a star in the constellation Coma Berenices that is located about 90 light-years (28 pc) from Earth. The apparent magnitude of 7.028 makes this star too faint to be seen with the unaided eye.
Epsilon Reticuli, Latinized from ε Reticuli, is a double star approximately 60 light-years away in the southern constellation of Reticulum. The brighter member is visible to the naked eye with an apparent visual magnitude of 4.44. The primary component is an orange subgiant, while the secondary is a white dwarf. The two stars share a common motion through space and hence most likely form a binary star system. The brighter star should be easily visible without optical aid under dark skies in the southern hemisphere. In 2000, an extrasolar planet was confirmed to be orbiting the primary star in the system.
HD 114762 is a triple star system approximately 125 light-years (38.2 pc) away in the constellation Coma Berenices. It consists of a yellow-white F-type main-sequence star (HD 114762 A) and two red dwarf companions (HD 114762 Ab & HD 114762 B) approximately 0.36 & 130 AU distant. Both are low-metal subdwarfs. Planets around such metal-poor stars are rare. A telescope or strong binoculars are needed to view the primary. HD 114762 had been used by scientists as a "standard star", one whose radial velocity is well established, but with the discovery of the spectroscopic companion HD 114762 Ab its usefulness as a standard has been called into question.
WD 0137-349 is a binary star in the constellation of Sculptor. It is located about 330 light-years away, and appears exceedingly faint with an apparent magnitude of 15.33.
HD 162020 is a star in the southern constellation of Scorpius with a likely red dwarf companion. It has an apparent visual magnitude of 9.10, which is too faint to be visible to the naked eye. The distance to this system is 102 light-years based on stellar parallax. It is drifting closer to the Sun with a radial velocity of −27 km/s, and is predicted to come to within ~18 light-years in 1.1 million years.
GD 356 is a white dwarf in the constellation of Draco showing an unusual emission of circular polarised light. The star is 65 light years from earth. The class of this white dwarf is DAe meaning that it has a cool helium rich atmosphere. This star exhibits emission lines showing the Zeeman effect in the hydrogen Balmer spectrum. GD 356 belongs to a class of high field magnetic white dwarfs (HFMWD), but it is unique in that the split lines are purely emission lines with no absorption. The emission region appears to be due to a heated upper layer in the photosphere in which the magnetic field is uniform to within 10%. The emission can be produced by an atmosphere at 7500K in a gravity field of 106 ms−2 and a magnetic field of 13 megaGauss. The magnetically split emission lines, Hα and Hβ, are circularly polarised. One explanation is that it is caused by a large electric current flowing between the poles of the star and a highly conducting planet. This planet was not detected in a later, more detailed analysis with new data. Rejecting the idea of an orbiting planet. Other explanations such as being due to Bondi-Hoyle accretion or due to a corona are ruled out by the lack of radio and X-ray emissions. Accretion of gas at a low rate over a broad area of the star, only results in heating at levels high in the atmosphere and not down to the opacity depth of 1.0 as observed with these lines.
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.
HD 23514, is a star in the Pleiades. It is a main-sequence star of class F6, and has been seen to have hot dust particles orbiting around it. These materials, otherwise known as planetesimals which orbit within a circumstellar disc, are evidence of possible planetary formation. The debris disk shows evidence of being rich in silica.
KOI-256 is a double star located in the constellation Cygnus approximately 575 light-years (176 pc) from Earth. While observations by the Kepler spacecraft suggested the system contained a gas giant exoplanet orbiting a red dwarf, later studies determined that KOI-256 was a binary system composed of the red dwarf orbiting a white dwarf.
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.
WISE J080822.18-644357.3, also called J0808, is a 45+11
−7 Myr old star system in the Carina constellation with a circumstellar debris disk orbiting an M-type red dwarf about 331 lightyears from Earth.
SDSS J1228+1040 is a white dwarf with a debris disk around it. The disk formed when a planetary body was tidally disrupted around the white dwarf. It is the first gaseous disk discovered around a white dwarf.
ROXs 12 is a binary system of pre-main-sequence stars. It belongs to the Rho Ophiuchi cloud complex. The surface temperature of the primary star is 3900±100 K. ROXs 12 is much younger than the Sun with an age of 7.6+4.1
−2.5 million years.
HD 283750, also known as V833 Tauri, is a K-type main-sequence star 57 light-years away from the Sun. The star is much younger than the Sun's at 1 billion years. HD 283750 is similar to the Sun in its concentration of heavy elements.
WD 1054–226, also known as LP 849-31, is a relatively cool magnitude 16 white dwarf star with a hydrogen atmosphere, in the small southern constellation of Crater located approximately 117 light years away at right ascension 10h57' and declination −22°53'. The name WD 1054–226 is based on the coordinates in the J1950 epoch. The star was recognized as a white dwarf along with 32 other nearby white dwarfs in 2007.
SDSS 1557 is a binary system composed of a white dwarf and a brown dwarf. The system is surrounded by a circumbinary debris disk. The debris disk was formed when a minor planet was tidally disrupted around the white dwarf in the past.
GALEX J2339–0424 is a white dwarf that is suspected to be polluted with material originating from an icy exomoon. This is evident from the first detection of beryllium in this white dwarf, together with GD 378.
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