Astronomy:V1429 Aquilae

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V1429 Aquilae is a candidate luminous blue variable multiple star system located in the constellation of Aquila. It is often referred to by its Mount Wilson Observatory catalog number as MWC 314. It is a hot luminous star with strong emission lines in its spectrum.

Spectrum

V1429 Aql has a peculiar spectrum dominated by emission lines of hydrogen and many ionised metals, with Feii being particularly strong and numerous. There are also comparatively weak forbidden lines, primarily [Feii], but also [Nii]. Some absorption lines are present, but are either very weak or hidden by the emission. Many lines have variable profiles, particularly the hydrogen and helium series which vary during the orbit from emission to P Cygni profiles. The absorption lines are considered to be formed in the photosphere of the primary star, although some Feii absorption appears to be from gas between the stars. No lines of the secondary can be detected. The emission lines are formed in circumstellar material between and around the two stars[1] Overall, the spectral type is given as B3 Ibe.[2][3]

In infrared spectra, the Pfund series of lines are strongly in emission, a very unusual feature characteristic of supergiant Be stars and LBVs. V1429 Aql is given a B2:e spectral type from analysis in the infrared.[4]

System

V1429 Aquilae is a single-lined spectroscopic binary. The existence of a companion is inferred from the highly periodic variations in the radial velocity of its spectral lines and by equally periodic variations in brightness and spectral line profiles. It is unclear whether there are partial eclipses of the larger star or just of gas surrounding the stars.[1]

The orbital period is well-defined at 60.7 days and it is moderately eccentric (0.244). The primary star fills its roche lobe for at least part of the orbit. The other characteristics of the orbit are disputed. The orbital velocity of the secondary is unknown, and the possible inclinations do not sufficiently restrict the possible models of the system. Assumptions based on broadly similar data produce wildly different results for the masses of the stars, from 5 M to 40 M for the primary.[1]

A third star is visible in infrared images just over one arc second away. It is statistically likely to be in a wide orbit around the spectroscopic pair, about 5,700 AU away.[5]

The system contains material being transferred from the primary to the secondary star as well as material surrounding both stars. A dense clump of gas near the centre of mass of the system, and co-rotating with the stars, produces the bulk of the emission lines. A more diffuse region of gas surrounds both stars and produces some absorption components in the spectrum.[1]

The entire system is surrounded by a shell of material about 0.8 parsecs across, assuming that MWC 314 is 3,000 parsecs away. This appears in infrared images as a circular ring 25 arc-seconds from the central star.[5] There is a much larger bipolar nebula detected by its Hα radiation. It is 13 parsecs from end to end.[6]

Variability

V1429 Aquilae shows brightness variations of about 0.3 magnitudes and a detectable period of 4.16 days. No longterm variations in brightness have been detected over several decades of observations.[7] The profiles of many spectral lines also vary with the same period, produced partly by radial velocity variations.[8] The absorption and emission lines show different radial velocity amplitudes, but with the same period. Most of these variations can be accounted for by the orbit of the two stars and material being transferred from the primary to the secondary, with the gas being involved in partial eclipses and possible also a partial eclipse of the primary star. The two stars are also distorted into ellipsoidal shapes by their gravity and vary in brightness as they rotate.[1]

In addition to the orbital variations, two pulsation modes have been observed with amplitudes of a few thousandths of a magnitude and periods of 0.77 and 1.42 days.[9]

Physical properties

V1429 Aquilae is sufficiently remote that its distance must be determined by indirect methods: estimates range between 2.4[9] and 4.3 kiloparsecs (9,800-14,000 light years), with 3 kpc usually being adopted.[8]

The primary is a hot B-type star. Its total luminosity has been estimated to be as much as 1,200,000 times that of the Sun (L), with a radius 60 times larger than that of the Sun (R), and 80 times more massive than the Sun (M).[10] More recent calculations give a luminosity of 710,000 L, radius of 87 R, and mass of 40 M.[11] Alternative assumptions about the orbit lead to lower values of 500,000 L, 73 R, and 5 M.[9]

The physical parameters of the star, and its spectrum, are comparable to a luminous blue variable (LBV). Although it has not shown the defining outbursts and spectral variations, the surrounding nebulae indicate episodes of heavy mass loss in the past.[11] Alternatively, it may be a supergiant Be star.[8]

The secondary cannot be observed. Making some assumptions, primarily the existence of a partial eclipse of the primary star, allows its mass and some physical properties to be estimated, giving a mass of 26 M and temperature of 6,227 K,[11] but these are speculative.[1]

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Frasca, A.; Miroshnichenko, A. S.; Rossi, C.; Friedjung, M.; Marilli, E.; Muratorio, G.; Busà, I. (2016). "Interpreting the spectral behavior of MWC 314". Astronomy & Astrophysics 585: A60. doi:10.1051/0004-6361/201527022. Bibcode2016A&A...585A..60F. 
  2. Carmona, A.; van den Ancker, M. E.; Audard, M.; Henning, Th.; Setiawan, J.; Rodmann, J. (2010). "New Herbig Ae/Be stars confirmed via high-resolution optical spectroscopy". Astronomy and Astrophysics 517: A67. doi:10.1051/0004-6361/200913800. ISSN 0004-6361. Bibcode2010A&A...517A..67C. 
  3. Chentsov, E. L.; Klochkova, V. G.; Tavolganskaya, N. S. (1999). "Spectral atlas of two peculiar supergiants: MWC 314 and IRC +10420". Bulletin of the Special Astrophysical Observatory 48: 25. Bibcode1999BSAO...48...25C. 
  4. Liermann, A.; Schnurr, O.; Kraus, M.; Kreplin, A.; Arias, M. L.; Cidale, L. S. (2014). "A K-band spectral mini-survey of Galactic B[e] stars". Monthly Notices of the Royal Astronomical Society 443 (2): 947–956. doi:10.1093/mnras/stu1174. ISSN 0035-8711. Bibcode2014MNRAS.443..947L. 
  5. 5.0 5.1 Martayan, Christophe; Lobel, Alex; Baade, Dietrich; Mehner, Andrea; Rivinius, Thomas; Boffin, Henri M. J.; Girard, Julien; Mawet, Dimitri et al. (2016). "Luminous blue variables: An imaging perspective on their binarity and near environment⋆". Astronomy & Astrophysics 587: A115. doi:10.1051/0004-6361/201526578. Bibcode2016A&A...587A.115M. 
  6. Marston, A. P.; McCollum, B. (August 2008). "Extended shells around B[e] stars. Implications for B[e] star evolution". Astronomy and Astrophysics 477 (1): 193–202. doi:10.1051/0004-6361:20066086. Bibcode2008A&A...477..193M 
  7. Muratorio, G.; Rossi, C.; Friedjung, M. (August 2008). "Analysis of the variability of the luminous emission line star MWC 314". Astronomy and Astrophysics 487 (2): 637–644. doi:10.1051/0004-6361:20078940. Bibcode2008A&A...487..637M 
  8. 8.0 8.1 8.2 Miroshnichenko, A. S. (August 1996). "MWC 314: a high-luminosity peculiar Be star.". Astronomy and Astrophysics 312: 941–949. Bibcode1996A&A...312..941M 
  9. 9.0 9.1 9.2 Richardson, Noel D.; Moffat, Anthony F. J.; Maltais-Tariant, Raphaël; Pablo, Herbert; Gies, Douglas R.; Saio, Hideyuki; St-Louis, Nicole; Schaefer, Gail et al. (2016). "Spectroscopy, MOST photometry, and interferometry of MWC 314: Is it an LBV or an interacting binary?". Monthly Notices of the Royal Astronomical Society 455: 244–257. doi:10.1093/mnras/stv2291. Bibcode2016MNRAS.455..244R. 
  10. Miroshnichenko, A. S.; Fremat, Y.; Houziaux, L.; Andrillat, Y.; Chentson, E. L.; Klochkova, V. G. (September 1998). "High resolution spectroscopy of the galactic candidate LBV MWC 314". Astronomy and Astrophysics Supplement 312 (3): 469–478. doi:10.1051/aas:1998283. Bibcode1998A&AS..131..469M. http://libres.uncg.edu/ir/uncg/f/A_Miroshnichenko_HighResolution_1998.pdf 
  11. 11.0 11.1 11.2 Lobel, A.; Groh, J. H.; Martayan, C.; Frémat, Y.; Torres Dozinel, K.; Raskin, G.; Van Winckel, H.; Prins, S. et al. (2013). "Modelling the asymmetric wind of the luminous blue variable binary MWC 314". Astronomy & Astrophysics 559: A16. doi:10.1051/0004-6361/201220421. ISSN 0004-6361. Bibcode2013A&A...559A..16L. 

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