EG Andromedae (often abbreviated to EG And) is a symbiotic binary in the constellation Andromeda. Its apparent visual magnitude varies between 6.97 and 7.80. [3]
EG Andromedae (often abbreviated to EG And) is a symbiotic binary in the constellation Andromeda. Its apparent visual magnitude varies between 6.97 and 7.80. [3]
The EG Andromedae system hosts a white dwarf and an evolved giant star, with an orbital period of 482.5 days. The giant star is losing mass through its stellar wind at a rate higher than 10−6 M☉/yr, and the white dwarf is accreting a fraction of this mass without forming an accretion disk. The white dwarf itself could emit a hot wind that interacts with the cooler one of the giant star, in addition to inducing the photoionization of the latter. [7] X-ray observations, however, failed to detect emission coming from colliding winds, but established the non-magnetic nature of the white dwarf and estimated its accretion rate at 1–10×10−7 M☉/yr. [8]
The giant star does not fill its Roche lobe but there are still large uncertainties on its mass and radius. [6] Even the parameters of the white dwarf are not strictly constrained, but available models can give lower and upper limits. [7]
The optical spectral classification of EG Andromedae is M2IIIep, [3] the one of a cool giant star with a peculiar spectrum and strong emission lines. The white dwarf contaminates the spectrum of the giant star photoionizes the stellar wind, giving rise to the spectral peculiarities. Emission lines H-alpha and H-beta, as well as TiO and Ca I ones, change in phase with the orbit. [6]
The white dwarf is best studied in the ultraviolet, where also highly ionized species sulfur, oxygen, nitrogen, carbon and phosphorus can be identified with their absorption or emission lines. [7]
X-ray observation of EG Andromedae detected a hot plasma (at a temperature of 3 keV) that is likely situated in the outer boundary layer of the white dwarf, without any contribution from an accretion disk. [8]
Discovery of the photometric variability of EG Andromedae was announced in 1964 by Polish astronomer Tadeusz Jarzębowski, based on observations made from 1961 through 1963 at Wroclaw Observatory. [9]
To date, no outburst has been observed in EG Andromedae. The observed variability is well described by the two components eclipsing each other during the orbit. However, there is some evidence that the giant star and the wind flow have an intrinsic variation. [10]
Ross 248, also called HH Andromedae or Gliese 905, is a small star approximately 10.30 light-years from Earth in the northern constellation of Andromeda. Despite its proximity it is too dim to be seen with the naked eye. It was first catalogued by Frank Elmore Ross in 1926 with his second list of proper-motion stars; on which count it ranks 261st in the SIMBAD database. It was too dim to be included in the Hipparcos survey. In about 40,000 years, Voyager 2 will pass 1.7 light-years from the star.
Upsilon Andromedae is a binary star located 44 light-years from Earth in the constellation of Andromeda. The system consists of an F-type main-sequence star and a smaller red dwarf.
HD 88133 is a yellow star with an orbiting exoplanet in the equatorial constellation of Leo. It has an apparent visual magnitude of 8.01, which is too faint to be visible to the naked eye. With a small telescope it should be easily visible. The distance to this system, as measured through parallax, is 240 light years, but it is slowly drifting closer with a radial velocity of −3.6 km/s.
Groombridge 34 is a binary star system in the northern constellation of Andromeda. It was listed as entry number 34 in A Catalogue of Circumpolar Stars, published posthumously in 1838 by British astronomer Stephen Groombridge. Based upon parallax measurements taken by the Gaia spacecraft, the system is located about 11.6 light-years from the Sun. This positions the pair among the nearest stars to the Solar System.
Z Andromedae is a binary star system consisting of a red giant and a white dwarf. It is the prototype of a type of cataclysmic variable star known as symbiotic variable stars or simply Z Andromedae variables. The brightness of those stars vary over time, showing a quiescent, more stable phase and then an active one with a more pronounced variability and stronger brightening and/or dimming.
A symbiotic binary is a type of binary star system, often simply called a symbiotic star. They usually contain a white dwarf with a companion red giant. The cool giant star loses material via Roche lobe overflow or through its stellar wind, which flows onto the hot compact star, usually via an accretion disk.
RX Andromedae is a variable star in the constellation of Andromeda. Although it is classified as a dwarf nova of the Z Camelopardalis (UGZ) type, it has shown low-luminosity periods typical of VY Sculptoris stars. However, for most of the time it varies from an apparent visual magnitude of 15.1 at minimum brightness to a magnitude of 10.2 at maximum brightness, with a period of approximately 13 days.
56 Pegasi is a binary star system in the northern constellation of Pegasus. It is visible to the naked eye with a combined apparent visual magnitude of 4.74. The system is approximately 590 light years away from the Sun based on parallax, but is drifting closer with a radial velocity of −28 km/s. It is listed as a member of the Wolf 630 moving group.
AG Pegasi is a symbiotic binary star in the constellation Pegasus. It is a close binary composed of a red giant and white dwarf, estimated to be around 2.5 and 0.6 times the mass of the Sun respectively. It is classified as a symbiotic nova; it has undergone one extremely slow nova outburst and a smaller outburst.
SY Muscae is a binary star system in the constellation Musca composed of a red giant and a white dwarf. Its apparent magnitude varies from 10.2 to 12.7 over a period of 624.5 days. Although the binary is a symbiotic star system, it is unusual in that it does not have an eruptive component. It is an S-type symbiotic system, which means that the light comes from the stars rather than surrounding dust.
Gliese 754 is a dim star in the southern constellation of Telescopium. It has an apparent visual magnitude of 12.25, which requires a telescope to view. The star is located at a distance of 19.3 light-years from the Sun based on parallax, and it is drifting further away with a radial velocity of +6 km/s. It is one of the hundred closest stars to the Solar System. Calculations of its orbit around the Milky Way showed that it is eccentric, and indicate that it might be a thick disk object.
DD Microscopii, also known as CD−43°14304, is a binary star system in the constellation Microscopium. The system has a combined average apparent magnitude around 11, making it readily visible in telescopes but not to the naked eye. It is thought to be at a distance of one or two thousand parsecs, although parallax measurements place the system at a distance of around 30,000 light years.
CH Cygni is a red giant, variable, symbiotic binary in the constellation Cygnus. It is the nearest symbiotic star to Earth, and one of the brightest, making it an ideal candidate for study.
AR Andromedae is a dwarf nova of the SS Cygni type in the constellation Andromeda. Its typical apparent visual magnitude is 17.6, but increases up to 11.0 magnitude during outbursts. The outbursts occur approximately every 23 days.
FF Andromedae is a spectroscopic binary in the constellation Andromeda. It has a typical apparent visual magnitude of 10.4, but undergoes flare events that can increase its brightness by about a magnitude.
QR Andromedae is an eclipsing binary star in the constellation Andromeda. Its maximum apparent visual magnitude is 12.16, but its light curve shows clearly eclipsing events where its brightness can drop to a magnitude of 13.07. This leads to its classification as an Algol variable star.
V455 Andromedae is a dwarf nova in the constellation Andromeda. It has a typical apparent visual magnitude of 16.5, but reached a magnitude of 8.5 during the only observed outburst.
HM Sagittae is a dusty-type symbiotic nova in the northern constellation of Sagitta. It was discovered by O. D. Dokuchaeva and colleagues in 1975 when it increased in brightness by six magnitudes. The object displays an emission line spectrum similar to a planetary nebula and was detected in the radio band in 1977. Unlike a classical nova, the optical brightness of this system did not rapidly decrease with time, although it showed some variation. It displays activity in every band of the electromagnetic spectrum from X-ray to radio.
4 Draconis, also known as HR 4765 and CQ Draconis, is a star about 570 light years from the Earth, in the constellation Draco. It is a 5th magnitude star, so it will be faintly visible to the naked eye of an observer far from city lights. It is a variable star, whose brightness varies slightly from 4.90 to 5.12 over a period of 4.66 years.
IW Andromedae is a binary star system in the northern constellation of Andromeda, abbreviated IW And. It is the prototype of a class of variable stars known as IW And variables, which is an anomalous sub-class of the Z Camelopardalis variables. The brightness of this system ranges from an apparent visual magnitude of 13.7 down to 17.3, which requires a telescope to view. The system is located at a distance of approximately 2,860 light years from the Sun based on parallax measurements.
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