HR 4049

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
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Antlia
Right ascension 10h 18m 07.59s[1]
Declination –28° 59′ 31.2″[1]
Apparent magnitude (V) 5.29 - 5.83[2]
Characteristics
Spectral type B9.5Ib-II[2]
B−V color index +0.24[3]
Variable type Post-AGB[4]
Astrometry
Radial velocity (Rv)-33[5] km/s
Proper motion (μ) RA: –15.734 ± 0.247[6] mas/yr
Dec.: 10.671 ± 0.250[6] mas/yr
Parallax (π)0.5799 ± 0.1514[6] mas
Distanceapprox. 6,000 ly
(approx. 1,700 pc)
Orbit[4]
Period (P)430.66±0.28
Eccentricity (e)0.30±0.01
Semi-amplitude (K1)
(primary)		15.96±0.19 km/s
Details
A
Mass0.56[4] M☉
Radius47±7[4] R☉
Luminosity6,300[4] L☉
Surface gravity (log g)+1.0±0.5[4] cgs
Temperature7,500±500[4] K
Metallicity [Fe/H]−4.5[7] dex
B
Mass0.56[4] M☉
Radius0.6[4] R☉
Luminosity0.06[4] L☉
Surface gravity (log g)4.6[4] cgs
Temperature3,500[4] K
Other designations
AG Antliae, CD-28°8070, 2MASS J10180758-2859308, GSC 06630-01759, HD 89353, FK5 1265, PPM 257470, HIP 50456, SAO 178644, HR 4049
Database references
SIMBADdata

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.[8][9] It also shows a strong infrared excess, corresponding closely to a 1,200 K blackbody produced by a disk of material surrounding the star.[10] The star is also undergoing intense mass-loss[11]

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.[4]

HR 4049 is an unusual variable star, ranging between magnitudes 5.29 and 5.83 with a period of 429 days.[12] 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,[13] 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.[4]

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.[14]

References
  1. van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.Vizier catalog entry
  2. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
  3. Hoffleit, Dorrit; Jaschek, Carlos (1991). "The Bright star catalogue". New Haven. Bibcode:1991bsc..book.....H.
  4. Bakker; et al. (1998). "Spectral variability of the binary HR 4049". Astronomy and Astrophysics. 336 (1): 263–275. arXiv:astro-ph/9802120. Bibcode:1998A&A...336..263B.
  5. Kharchenko, N. V.; Scholz, R. -D.; Piskunov, A. E.; Röser, S.; Schilbach, E. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ̃55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. S2CID 119323941.
  6. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  7. Kiss, L. L.; Derekas, A.; Szabó, Gy. M.; Bedding, T. R.; Szabados, L. (2007). "Defining the instability strip of pulsating post-AGB binary stars from ASAS and NSVS photometry". Monthly Notices of the Royal Astronomical Society. 375 (4): 1338–1348. arXiv:astro-ph/0612217. Bibcode:2007MNRAS.375.1338K. doi:10.1111/j.1365-2966.2006.11387.x. S2CID 14716983.
  8. Waelkens, C.; Lamers, H.; Waters, R. (September 1987). "HR 4049 - an old low-mass star disguised as a young massive supergiant". ESO Messenger. 49: 29–32. Bibcode:1987Msngr..49...29W.
  9. Takeda, Y.; Parthasarathy, M.; Aoki, W.; Ita, Y.; Nakada, Y.; Izumiura, H.; Noguchi, K.; Takada-Hidai, M.; Sato, B.; Tajitsu, A.; Honda, S.; Kawanomoto, S.; Ando, H.; Karoji, H. (2002). "Detection of Zinc in the Very Metal-Poor Post-AGB Star HR 4049". Publications of the Astronomical Society of Japan. 54 (5): 765. Bibcode:2002PASJ...54..765T. doi:10.1093/pasj/54.5.765.
  10. Acke, B.; Degroote, P.; Lombaert, R.; De Vries, B. L.; Smolders, K.; Verhoelst, T.; Lagadec, E.; Gielen, C.; Van Winckel, H.; Waelkens, C. (2013). "Amorphous carbon in the disk around the post-AGB binary HR 4049". Astronomy & Astrophysics. 551: A76. Bibcode:2013A&A...551A..76A. doi:10.1051/0004-6361/201219282.
  11. Geballe, T. R.; Noll, K. S.; Whittet, D. C. B.; Waters, L. B. F. M. (1989). "Unusual features of the 1-4 micron spectrum of HR 4049". The Astrophysical Journal. 340: L29. Bibcode:1989ApJ...340L..29G. doi:10.1086/185431.
  12. VSX (4 January 2010). "AG Antliae". The International Variable Star Index. American Association of Variable Star Observers. Retrieved 15 June 2013.
  13. Hillen, M.; Van Winckel, H.; Menu, J.; Manick, R.; Debosscher, J.; Min, M.; De Wit, W. -J.; Verhoelst, T.; Kamath, D.; Waters, L. B. F. M. (2017). "A mid-IR interferometric survey with MIDI/VLTI: Resolving the second-generation protoplanetary disks around post-AGB binaries". Astronomy and Astrophysics. 599: A41. arXiv:1610.09930. Bibcode:2017A&A...599A..41H. doi:10.1051/0004-6361/201629161. S2CID 119095913.
  14. Malek, S. E.; Cami, J. (2014). "The Gas-Rich Circumbinary Disk of Hr 4049. I. A Detailed Study of the Mid-Infrared Spectrum". The Astrophysical Journal. 780 (1): 41. arXiv:1310.6361. Bibcode:2014ApJ...780...41M. doi:10.1088/0004-637X/780/1/41. S2CID 118617900.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.