Z Andromedae

Last updated
Z Andromedae
Observation data
Epoch J2000       Equinox J2000
Constellation Andromeda
Right ascension 23h 33m 39.9551s [1]
Declination +48° 49′ 05.974″ [1]
Apparent magnitude  (V)7.7 - 11.3 [2]
Characteristics
Spectral type M2III + B1eq [3]
U−B color index −0.49 [4]
B−V color index +1.35 [4]
Variable type Z And [2]
Astrometry
Radial velocity (Rv)-0.59 [5]  km/s
Proper motion (μ)RA: -1.606 ± 0.049 [1]   mas/yr
Dec.: -2.971 ± 0.040 [1]   mas/yr
Parallax (π)0.5123 ± 0.0300  mas [1]
Distance 6,400 ± 400  ly
(2,000 ± 100  pc)
Orbit
Period (P)759.0±1.9 [6] days
Eccentricity (e)0.0 [6]
Inclination (i)47±12 [7] °
Semi-amplitude (K1)
(primary)		6.73±0.22 [6] km/s
Details
Red giant
Mass 2 [6]   M☉
Radius 85 [3]   R☉
Luminosity 880 [8]   L☉
Temperature 3,400 [3]   K
White dwarf
Mass 0.75 [6]   M☉
Radius 0.17 - 0.36 [9]   R☉
Luminosity1,500 - 9,800 [9]   L☉
Temperature 90,000 - 150,000 [9]   K
Rotation 1682.6 ± 0.6 s [10]
Other designations
MWC 416, HD 221650, HIP 116287, SAO 53146, PPM 64386, AG+48° 2087, GCRV 14773, IRAS 23312+4832, HV 193, AN 41.1901, JP11 3636, TYC 3645-2066-1, BD+48° 4093, GSC 03645-02066, 2MASS J23333994+4849059, AAVSO 2328+48, 2E 2331.6+4834, PLX 5697, 2E 4735
Database references
SIMBAD data
Data sources:
Hipparcos Catalogue,
CCDM (2002),
Bright Star Catalogue (5th rev. ed.)

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. [11]

Contents

Binary system

Z Andromedae is a binary star system. The two components have a circular orbit that takes 759 days to complete. [6] The red giant is around twice the mass of the sun and 880 times its luminosity, but its effective temperature is only 2,800 K. The white dwarf is around a thousand times the luminosity of the sun during the quiescent phase, but up to 10 times more luminous during the active phases. Its temperature is as high as 150,000 K when quiescent, but drops below 100,000 K when active. [9] It also spins around its rotation axis every 1,682 seconds and displays a strong magnetic field. [10]

The evolved red giant star is losing mass, since radiation pressure overcomes the low gravity on the surface. The outflow of matter is captured by the gravitational field of the white dwarf and falls on its surface in the end. At least during the active phase an accretion disk forms around the white dwarf. [12]

Variability

Light curve of Z Andromedae, showing a typical outburst in 1986 and the abnormally long active period from 2000 onwards Z Andromedae light curve.png
Light curve of Z Andromedae, showing a typical outburst in 1986 and the abnormally long active period from 2000 onwards

The variability of Z Andromedae was discovered by Williamina Paton Stevens Fleming , and announced in 1901. [13]

During the quiescent phase, most of the white dwarf luminosity comes from stable hydrogen burning on its surface, and photons emitted this way ionize the wind of the red giant which causes nebular emission. The giant star, however, follows a quasi-periodic activity cycle (similar to the solar cycle) roughly every 7,550 days; when the activity of the star is enhanced, the stellar wind becomes stronger, and in response the white dwarf increases in size and cools, triggering the active phase. [7]

In the quiescent phase, the brightness of Z Andromedae is modulated by the orbital period of the system, and can reach a magnitude of mv = 11.3 at minimum. During the active phase Z Andromedae makes luminosity outbursts and can increase its brightness up to a magnitude of mv = 7.7. Eclipses from the red giant are still visible in this phase. During this phase, a shorter periodicity of 685 days is observed; this could be a beat period between the unknown rotation period of the giant star and the orbital period, which arise from the non-spherical outflow of matter from the atmosphere of the giant star. [8] [2] [7]

Z Andromedae started an unusually long active phase in September 2000, brightening by several magnitudes multiple times over at least a decade. During the outbursts, irregular brightness variations (up to 0.065 magnitudes) were observed at timescales shorter than a day, interpreted as warping in the accretion disk. If models for this source are correct, it should enter a quiescent phase again in 2020. [12]

Spectrum

Optical

The spectrum of Z Andromedae has been recognised as extremely peculiar since the early 20th century. Early spectra during a bright period, showing only emission lines against a red continuum, were interpreted as a star embedded in dense nebulosity. [14] As the star's brightness faded, the spectrum lost the high excitation "nebular" lines and developed absorption lines with P Cygni profiles. These spectra were readily identified as being due to a hot nova-like star with a cool companion. [15] Emission lines identified included low ionization states of hydrogen and helium with high ionization states of oxygen and iron. [9]

The MK spectral classification is typical of a cool giant, for example M4.5. [3] The exact spectral type has been shown to vary, for example between M5 in 1987 and M3.5 in 1989. [16] Infrared observations gave a combination spectral type of M2III + B1eq. Here the luminosity class of III is for a normal giant star, and the peculiarity codes eq indicate emission lines with P Cygni profiles. [3]

Ultraviolet

Z Andromedae shows also a strong ultraviolet emission, which follows the optical behaviour; absorption lines identified during the quiescent phase becomes emission lines during outbursts. Elements identified in this region of the spectrum are carbon, nitrogen, phosphorus and silicon in their ionized states. [9]

Radio

The radio flux from Z Andromedae at the beginning of outbursts is lower than the usual quiescent level, and has a maximum after the optical one. After the outbursts, radio jets can be seen flowing out of this system, in a direction perpendicular to the orbital plane. [9]

X-ray

Z Andromedae is much fainter in X-ray, and has not been detected when in the quiescent phase. During outbursts, X-ray emission comes from shock-heated plasma, where the kinetic energy of the outflowing material is converted in X-ray radiation. This emission "mimics" a blackbody radiation with a temperature different from the one of the white dwarf, but its real nature can be identified because it shows absorption edges (which shows also the presence of neon) and an excess at high frequencies. [9]

Bipolar jets

Following the 2006 outburst, the hydrogen Balmer emission lines included faint wings at a velocity of ±1,150 km/s. Since extended radio outflows had previously been seen during the long 2000-2002 outbursts, collimated jets along the axis of the system were the most likely explanation for this phenomenon. It is thought that the jets are only present during bright outbursts. [17] The jets were observed again during subsequent outbursts; their velocity is highly variable at the beginning but settles on a constant velocity after roughly 1 month. A single jet can also occur. The jets could be formed by material that cannot accrete on the white dwarf that reaches the Eddington limit. [12]

Related Research Articles

<span class="mw-page-title-main">T Coronae Borealis</span> Recurrent nova in the constellation Corona Borealis

T Coronae Borealis, nicknamed the Blaze Star, is a binary star and a recurrent nova about 3,000 light-years away in the constellation Corona Borealis. It was first discovered in outburst in 1866 by John Birmingham, though it had been observed earlier as a 10th magnitude star. It may have been observed in 1217 and in 1787 as well. In February 1946 a 15 year old schoolboy from Wales named Michael Woodman observed a flare up, subsequently writing to the Astronomer Royal and leading to the theory that the star flares each 80 years.

<span class="mw-page-title-main">Delta Trianguli</span> Binary star in the constellation Triangulum

Delta Trianguli, Latinized from Delta Tri, is a spectroscopic binary star system approximately 35 light-years (11 pc) away in the constellation of Triangulum. The primary star is a yellow dwarf, while the secondary star is thought to be an orange dwarf. It has an apparent magnitude of +4.87 and forms an optical (line-of-sight) triple with Gamma Trianguli and 7 Trianguli.

<span class="mw-page-title-main">Omega Andromedae</span> Binary star system in the constellation Andromeda

Omega Andromedae is the Bayer designation for a slowly co-rotating binary star system in the northern constellation of Andromeda. Parallax measurements made during the Gaia mission make this system to be approximately 93.9 light-years from Earth. Its apparent visual magnitude is +4.83, which makes it bright enough to be seen with the naked eye.

<span class="mw-page-title-main">8 Andromedae</span> Multiple star system in the constellation Andromeda

8 Andromedae, abbreviated 8 And, is a probable triple star system in the northern constellation of Andromeda. 8 Andromedae is the Flamsteed designation. It is visible to the naked eye with an apparent visual magnitude of 4.82. Based upon an annual parallax shift of 5.7 mas, it is located about 570 light years from the Earth. It is moving closer with a heliocentric radial velocity of −8 km/s.

<span class="mw-page-title-main">R Aquarii</span> Star in the constellation of Aquarius

R Aquarii is a variable star in the constellation Aquarius.

<span class="mw-page-title-main">Symbiotic binary</span> Class of astronomical objects

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.

<span class="mw-page-title-main">AG Draconis</span> Star in the constellation Draco

AG Draconis is a binary star system in the northern constellation of Draco. It consists of a giant star and a white dwarf that revolve around each other every 550 days.

<span class="mw-page-title-main">AG Pegasi</span> Star in the constellation Pegasus

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.

<span class="mw-page-title-main">DD Microscopii</span> Star in the constellation Microscopium

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.

<span class="mw-page-title-main">CH Cygni</span> Variable star in the Cygnus constellation

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.

<span class="mw-page-title-main">DX Andromedae</span> Star in the constellation Andromeda

DX Andromedae is a cataclysmic variable star in the constellation Andromeda. It has a typical apparent visual magnitude of 15.5 during the quiescent phase, but becomes brighter during outbursts recurring with a mean cycle length of 330 days, thus is classified as a dwarf nova of the SS Cygni type.

<span class="mw-page-title-main">EG Andromedae</span> Binary star system in the constellation Andromeda

EG Andromedae is a symbiotic binary in the constellation Andromeda. Its apparent visual magnitude varies between 6.97 and 7.80.

<span class="mw-page-title-main">FF Andromedae</span> Star in the constellation Andromeda

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.

<span class="mw-page-title-main">PX Andromedae</span> Star in the constellation Andromeda

PX Andromedae is an eclipsing cataclysmic variable star in the constellation Andromeda. It has been classified as a SW Sextantis variable, and its apparent visual magnitude varies between 14.04 and 17.

<span class="mw-page-title-main">V455 Andromedae</span> Dwarf nova star in the constellation Andromeda

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.

<span class="mw-page-title-main">EX Lupi</span>

EX Lupi is a young, single T-Tauri star in the southern constellation of Lupus. An irregular variable, it is the prototype of young, low-mass eruptive stars named EXors, with EX Lupi being this object's variable star designation. At its minimal activity level, EX Lupi resembles a classical T-Tauri star of the M0 dwarf type. The low latitude of this star, at a declination of −40°, makes it difficult for northern observers to view. Based on parallax measurements, it is located at a distance of about 505 light years from the Sun. The star lies next to a gap in the Lupus cloud complex, a star forming region.

<span class="mw-page-title-main">HM Sagittae</span> Symbiotic nova in the constellation of Sagitta

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.

<span class="mw-page-title-main">4 Draconis</span> Variable star in the constellation Draco

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.

<span class="mw-page-title-main">IW Andromedae</span> Star system in the constellation Andromeda

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.

<span class="mw-page-title-main">MWC 560</span> Binary star in the constellation Monoceros

MWC 560 is a symbiotic binary star system in the equatorial constellation of Monoceros. The identifier comes from the Mount Wilson Calatogue of class O, B and A stars with bright hydrogen lines, published in 1933 by P. W. Merrill and associates. It has the variable star designation V694 Monoceros. This system has a typical apparent visual magnitude of 9.70, which is too dim to be visible to the naked eye. Based on parallax measurements, it is located at a distance of approximately 7,700 light years from the Sun.

References

  1. 1 2 3 4 5 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.
  2. 1 2 3 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. Bibcode:2009yCat....102025S.
  3. 1 2 3 4 5 Shenavrin, V. I.; Taranova, O. G.; Nadzhip, A. E. (2011). "Search for and study of hot circumstellar dust envelopes". Astronomy Reports. 55 (1): 31–81. Bibcode:2011ARep...55...31S. doi:10.1134/S1063772911010070. S2CID   122700080.
  4. 1 2 Martel, M. T.; Gravina, R (1985). "UBV Observations of Symbiotic Stars in July and October 1982". Information Bulletin on Variable Stars. 2750: 1. Bibcode:1985IBVS.2750....1M.
  5. ↑ Pourbaix, D; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; Levato, H; Morrell, N. I.; Torres, G; Udry, S (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727–732. arXiv: astro-ph/0406573 . Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213. S2CID   119387088.
  6. 1 2 3 4 5 6 Fekel, Francis C; Hinkle, Kenneth H; Joyce, Richard R; Skrutskie, Michael F (2000). "Infrared Spectroscopy of Symbiotic Stars. II. Orbits for Five S-Type Systems with Two-Year Periods". The Astronomical Journal. 120 (6): 3255. Bibcode:2000AJ....120.3255F. doi: 10.1086/316872 .
  7. 1 2 3 Leibowitz, Elia M; Formiggini, Liliana (2008). "Activity cycle of the giant star of Z Andromedae and its spin period". Mon. Not. R. Astron. Soc. 385 (1): 445–452. arXiv: 0712.2120 . Bibcode:2008MNRAS.385..445L. doi: 10.1111/j.1365-2966.2008.12847.x . S2CID   88510675.
  8. 1 2 Skopal, A (2003). "Discovery of the eclipse in the symbiotic binary Z Andromedae". Astronomy & Astrophysics. 401 (3): L17 –L20. arXiv: astro-ph/0304046 . Bibcode:2003A&A...401L..17S. doi:10.1051/0004-6361:20030332. S2CID   13413270.
  9. 1 2 3 4 5 6 7 8 Sokoloski, J. L.; Kenyon, S. J.; Espey, B. R.; Keyes, Charles D; McCandliss, S. R.; Kong, A. K. H; Aufdenberg, J. P.; Filippenko, A. V.; Li, W; Brocksopp, C; Kaiser, Christian R; Charles, P. A.; Rupen, M. P.; Stone, R. P. S (2006). "A Combination Nova Outburst in Z Andromedae: Nuclear Shell Burning Triggered by a Disk Instability". The Astrophysical Journal. 636 (2): 1002–1019. arXiv: astro-ph/0509638 . Bibcode:2006ApJ...636.1002S. doi:10.1086/498206. S2CID   8941207.
  10. 1 2 Sokoloski, J. L.; Bildsten, Lars (1999). "Discovery of a Magnetic White Dwarf in the Symbiotic Binary Z Andromedae". The Astrophysical Journal. 517 (2): 919–924. arXiv: astro-ph/9812294 . Bibcode:1999ApJ...517..919S. doi:10.1086/307234. S2CID   18394589.
  11. ↑ "Z Andromedae star" . Retrieved 2018-01-16.
  12. 1 2 3 Skopal, A.; Tarasova, T. N.; Wolf, M.; Dubovský, P. A.; Kudzej, I. (2018). "Repeated Transient Jets from a Warped Disk in the Symbiotic Prototype Z And: A Link to the Long-lasting Active Phase". The Astrophysical Journal. 858 (2): 120. arXiv: 1805.10908 . Bibcode:2018ApJ...858..120S. doi: 10.3847/1538-4357/aabc11 . S2CID   73652665.
  13. ↑ Pickering, E. C.; Colson, H. R.; Fleming, W. P.; Wells, L. D. (April 1901). "Sixty-four new variable stars". Astrophysical Journal. 13: 226–230. Bibcode:1901ApJ....13..226P. doi:10.1086/140808 . Retrieved 12 November 2024.
  14. ↑ Plaskett, J. S. (1928). "The composite stellar and nebular spectrum of Z Andromedae". Publications of the Dominion Astrophysical Observatory Victoria. 4: 119. Bibcode:1928PDAO....4..119P.
  15. ↑ Swings, P; Struve, O (1941). "The Evolution of a Peculiar Stellar Spectrum: Z Andromedae". Astrophysical Journal. 93: 356. Bibcode:1941ApJ....93..356S. doi:10.1086/144272. hdl: 2268/72129 .[ permanent dead link ]
  16. ↑ Mürset, U; Schmid, H. M. (1999). "Spectral classification of the cool giants in symbiotic systems". Astronomy and Astrophysics Supplement. 137 (3): 473. Bibcode:1999A&AS..137..473M. doi: 10.1051/aas:1999105 .
  17. ↑ Burmeister, M; Leedjärv, L (2006). "Evidence for bipolar jets from the optical spectra of the prototypical symbiotic star Z Andromedae". Astronomy & Astrophysics. 461 (1): L5 –L8. arXiv: astro-ph/0611475 . Bibcode:2007A&A...461L...5B. doi:10.1051/0004-6361:20066630. S2CID   16474465.

Further reading

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.