A light curve for HR 4049. The main plot shows the visual band brightness over one orbital period. The inset plot shows how the amplitude of the brightness change varies as a function of wavelength−1; as the observing wavelength increases, the opacity of the dust decreases, so the dust obscures less of the star's light. Adapted from Jorissen & Frankowski (2008) [1] | |
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Antlia |
Right ascension | 10h 18m 07.59s [2] |
Declination | –28° 59′ 31.2″ [2] |
Apparent magnitude (V) | 5.29 - 5.83 [3] |
Characteristics | |
Spectral type | B9.5Ib-II [3] |
B−V color index | +0.24 [4] |
Variable type | Post-AGB [5] |
Astrometry | |
Radial velocity (Rv) | -33 [6] km/s |
Proper motion (μ) | RA: –15.734 ± 0.247 [7] mas/yr Dec.: 10.671 ± 0.250 [7] mas/yr |
Parallax (π) | 0.5799 ± 0.1514 mas [7] |
Distance | approx. 6,000 ly (approx. 1,700 pc) |
Orbit [5] | |
Period (P) | 430.66±0.28 |
Eccentricity (e) | 0.30±0.01 |
Semi-amplitude (K1) (primary) | 15.96±0.19 km/s |
Details | |
A | |
Mass | 0.56 [5] M☉ |
Radius | 47±7 [5] R☉ |
Luminosity | 6,300 [5] L☉ |
Surface gravity (log g) | +1.0±0.5 [5] cgs |
Temperature | 7,500±500 [5] K |
Metallicity [Fe/H] | −4.5 [8] dex |
B | |
Mass | 0.56 [5] M☉ |
Radius | 0.6 [5] R☉ |
Luminosity | 0.06 [5] L☉ |
Surface gravity (log g) | 4.6 [5] cgs |
Temperature | 3,500 [5] K |
Other designations | |
Database references | |
SIMBAD | data |
HR 4049, also known as HD 89353 and AG Antliae, is a binary post-asymptotic-giant-branch (post-AGB) star in the constellation Antlia. A very metal-poor star, it is surrounded by a thick unique circumbinary disk enriched in several molecules. With an apparent magnitude of about 5.5, the star can readily be seen under ideal conditions. It is located approximately 1,700 parsecs (5,500 ly) distant.
HR 4049 has a peculiar spectrum. The star appears, based on its spectrum in the Balmer series, to be a blue supergiant, although in reality it is an old low-mass star on the post-AGB phase of its life. Its atmosphere is extremely deficient in heavy elements, over with a metallicity over 30,000 lower than the Sun. [9] [10] It also shows a strong infrared excess, corresponding closely to a 1,200 K blackbody produced by a disk of material surrounding the star. [11] The star is also undergoing intense mass-loss [12]
HR 4049 has an unseen companion, detected from variations in the doppler shift of its spectral lines. The properties of the companion can only be estimated by making certain assumptions about the inclination of the orbit and the mass function. Given those assumptions, it is thought to be a low luminosity main sequence star. [5]
HR 4049 is an unusual variable star, ranging between magnitudes 5.29 and 5.83 with a period of 429 days. [13] It has been given the variable star designation AG Antliae, but is still more commonly referred to as HR 4049. It has been described as pulsating in a similar fashion to an RV Tauri variable, [14] although the preferred interpretation is that the variations are produced by variable extinction produced by the material around the star and that the period is the same as the orbital period. [5]
Although HR 4049 apparently has the spectrum of a blue supergiant, it is an old low-mass star which has exhausted nuclear fusion and is losing its outer layers as it transitions towards a white dwarf and possibly a planetary nebula. During this phase it has a luminosity several thousand times that of the Sun, although a mass around half that of the sun. The mass can only be guessed from the expected mass of the white dwarf that it is becoming. [15]
Antlia is a constellation in the Southern Celestial Hemisphere. Its name means "pump" in Latin and Greek; it represents an air pump. Originally Antlia Pneumatica, the constellation was established by Nicolas-Louis de Lacaille in the 18th century. Its non-specific (single-word) name, already in limited use, was preferred by John Herschel then welcomed by the astronomic community which officially accepted this. North of stars forming some of the sails of the ship Argo Navis, Antlia is completely visible from latitudes south of 49 degrees north.
Red supergiants (RSGs) are stars with a supergiant luminosity class of spectral type K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Antares are the brightest and best known red supergiants (RSGs), indeed the only first magnitude red supergiant stars.
RV Tauri is a star in the constellation Taurus. It is a yellow supergiant and is the prototype of a class of pulsating variables known as RV Tauri variables. It is a post-AGB star and a spectroscopic binary about 4,700 light years away.
U Antliae is a variable star in the constellation Antlia. It is a carbon star surrounded by two thin shells of dust.
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R Scuti is a star in the constellation of Scutum. It is a yellow supergiant and is a pulsating variable known as an RV Tauri variable. It was discovered in 1795 by Edward Pigott at a time when only a few variable stars were known to exist.
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AC Herculis, is an RV Tauri variable and spectroscopic binary star in the constellation of Hercules. It varies in brightness between apparent magnitudes 6.85 and 9.0.
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