V1429 Aquilae is a candidate luminous blue variable

multiple star system A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a '' star cluster'' or '' galaxy'', although, broadly speaki ...

located in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

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 Fe being particularly strong and numerous. There are also comparatively weak forbidden lines, primarily e but also 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 Fe 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 Overall, the spectral type is given as B3 Ibe. In

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

spectra, the

Pfund series The emission spectrum of atomic hydrogen has been divided into a number of spectral series, with wavelengths given by the Rydberg formula. These observed spectral lines are due to the electron making transitions between two energy levels in an ...

of lines are strongly in emission, a very unusual feature characteristic of supergiant

Be star Be stars are a heterogeneous set of stars with B spectral types and emission lines. A narrower definition, sometimes referred to as ''classical Be stars'', is a non-supergiant B star whose spectrum has, or had at some time, one or more Balmer e ...

s and LBVs. V1429 Aql is given a B2:e spectral type from analysis in the infrared.

System

V1429 Aquilae is a single-lined

spectroscopic binary A binary star is a system of two star, stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separa ...

. The existence of a companion is inferred from the highly periodic variations in the

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

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. The orbital period is well-defined at 60.7 days and it is moderately eccentric (0.244). The primary star fills its

roche lobe In astronomy, the Roche lobe is the region around a star in a binary system within which orbiting material is gravitationally bound to that star. It is an approximately teardrop-shaped region bounded by a critical gravitational equipotential, wit ...

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 to for the primary. 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. 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. 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. There is a much larger bipolar nebula detected by its H_α radiation. It is 13 parsecs from end to end.

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. The profiles of many spectral lines also vary with the same period, produced partly by radial velocity variations. 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 possibly also partial eclipses of the stars themselves. The two stars are also distorted into ellipsoidal shapes by their gravity and vary in brightness as they rotate. 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.

Physical properties

Estimates of the distance of V1429 Aquilae made by indirect methods range between 2.4 and 4.3 kilo parsecs (9,800-14,000 light years), with 3 kpc usually being adopted. The

Gaia EDR3 The ''Gaia'' catalogues are star catalogues created using the results obtained by ''Gaia'' space telescope. The catalogues are released in stages that will contain increasing amounts of information; the early releases also miss some stars, especia ...

parallax is , suggesting a somewhat larger distance. 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 (), with a radius 60 times larger than that of the Sun (), and 80 times more massive than the Sun (). More recent calculations give a luminosity of , radius of , and mass of . Alternative assumptions about the orbit lead to lower values of , , and . The physical parameters of the star, and its spectrum, are comparable to a

luminous blue variable Luminous blue variables (LBVs) are massive evolved stars that show unpredictable and sometimes dramatic variations in their spectra and brightness. They are also known as S Doradus variables after S Doradus, one of the brightest stars of the Larg ...

(LBV). Although it has not shown the defining outbursts and spectral variations, the surrounding nebulae indicate episodes of heavy mass loss in the past. Alternatively, it may be a supergiant Be star. 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 and temperature of 6,227 K, but these are speculative. A more recent survey of LBVs put V1429 Aquilae's luminosity at a much higher .

References

{{DEFAULTSORT:V1429 Aquilae B-type supergiants Luminous blue variables Aquila (constellation) Aquilae, V1429 BD+14 3887 J19213397+1452570 Eclipsing binaries Emission-line stars