WZ Sagittae

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WZ Sagittae
WZSgeLightCurve.png
A visual band light curve for WZ Sagittae. The main plot, adapted from Kato (2015), [1] shows the period after the 2001 eruption, and the inset plot, adapted from Patterson et al. (2018), [2] shows the short-term variability including the eclipse.
Observation data
Epoch J2000       Equinox J2000
Constellation Sagitta
Right ascension 20h 07m 36.5036s [3]
Declination +17° 42′ 14.734″ [3]
Apparent magnitude  (V)15.20 [4]
7.0 - 15.5 B [5]
Characteristics
Spectral type DApe [6]
U−B color index +1.45 [7]
B−V color index +1.49 [7]
Variable type Dwarf nova [4]
Astrometry
Radial velocity (Rv)−51 [4]  km/s
Proper motion (μ)RA: 71.635 [3]   mas/yr
Dec.: -24.348 [3]   mas/yr
Parallax (π)22.1564 ± 0.0395  mas [3]
Distance 147.2 ± 0.3  ly
(45.13 ± 0.08  pc)
Orbit
Period (P)82 mins [8]
Inclination (i)77 ± 2 [9] °
Semi-amplitude (K1)
(primary)		40 ± 10 [9] km/s
Details
A
Mass 0.85±0.04 [8]   M☉
Surface gravity (log g)9.0 [9]   cgs
Temperature 17,800 [9]   K
B
Mass 0.078 - 0.13 [8]   M☉
Other designations
WZ Sge, Sge 1913, 2MASS J20073649+1742147, WD 2003+17. [4]
Database references
SIMBAD data

WZ Sagittae (WZ Sge) is a cataclysmic dwarf nova [4] star system in the constellation Sagitta. It consists of a white dwarf primary being orbited by a low mass companion. The white dwarf is about 0.85 solar masses while the companion is only 0.08 solar masses. This implies that the companion is a spectral class L2 star, although this has yet to be confirmed. [8] The distance to this system has been determined by parallax, yielding a distance of 45.1 parsecs. [10] [3]

WZ Sagittae is an ultrashort period cataclysmic nova, with outbursts observed in 1913, 1946, 1978 and 2001. During the well-observed 2001 outburst, the nova reached a peak visual magnitude of 8.21. The 1913 event was the brightest of the observed outbursts, reaching a photographic magnitude of 7.0. [10]

This nova is classified as a SU Ursae Majoris class star, which is a subclass of dwarf nova that produces what are termed superoutbursts spaced several months apart, interspaced with normal outbursts every few weeks. The normal outbursts typically last 2−3 days, while a superoutburst lasts a few weeks. However, WZ Sagittae is unusual in that it is only observed to emit superbursts. [11]

The outbursts of a dwarf nova are caused when matter from a ring-like accretion disk becomes unstable. In this system, the companion star is sufficiently close to the white dwarf that the tidal bulge of the former overlaps the Roche limit, allowing matter to pass across and accumulate onto the disk. When the disk reaches a critical temperature, the gas collapses onto the white dwarf resulting in the release of gravitational potential energy. [12]

A superoutburst may be caused by a tidal interaction of the accretion disk with the donor star, resulting in a greater deposition of matter on the white dwarf. In the case of WZ Sagittae, however, magnetic effects may act to enhance the deposition, resulting in the lack of normal outbursts. [11] Because of the unique timing differences in the rate of superoutbursts of this nova, it been designated the prototype star for a WZ Sagittae subclass.

The orbital period of this system is 1.361 hours. Based upon observations of eclipses of the hot spot on the white dwarf (created by infalling material), the orbital plane of this system is inclined by 76° ± 6° to the line of sight from the Earth. [10]

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Sagitta is a dim but distinctive constellation in the northern sky. Its name is Latin for 'arrow', not to be confused with the significantly larger constellation Sagittarius 'the archer'. It was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations defined by the International Astronomical Union. Although it dates to antiquity, Sagitta has no star brighter than 3rd magnitude and has the third-smallest area of any constellation.

<span class="mw-page-title-main">DQ Herculis</span> Nova in the constellation Hercules

DQ Herculis, or Nova Herculis 1934, was a slow, bright nova occurring in the northern constellation of Hercules in December 1934. This cataclysmic variable star was discovered on 13 December 1934 by J. P. M. Prentice from Stowmarket, Suffolk. It reached peak brightness on 22 December 1934 with an apparent magnitude of 1.5. The nova remained visible to the naked eye for several months.

<span class="mw-page-title-main">V838 Herculis</span> 1991 Nova seen in the constellation Hercules

V838 Herculis, also known as Nova Herculis 1991, was a nova which occurred in the constellation Hercules in 1991. It was discovered by George Alcock of Yaxley, Cambridgeshire, England at 4:35 UT on the morning of 25 March 1991. He found it with 10×50 binoculars, and on that morning its apparent visual magnitude was 5. Palomar Sky Survey plates showed that before the outburst, the star was at photographic magnitude 20.6 and 18.25.

<span class="mw-page-title-main">V1494 Aquilae</span> Nova seen in 1999 in the constellation of Aquila

V1494 Aquilae or Nova Aquilae 1999 b was a nova which occurred during 1999 in the constellation Aquila and reached a brightness of magnitude 3.9 on 2 December 1999. making it easily visible to the naked eye. The nova was discovered with 14×100 binoculars by Alfredo Pereira of Cabo da Roca, Portugal at 18:50 UT on 1 December 1999, when it had a visual magnitude of 6.0.

<span class="mw-page-title-main">Dwarf nova</span> Cataclysmic variable star, consisting of a close binary star system

A dwarf nova, or U Geminorum variable, is one of several types of cataclysmic variable star, consisting of a close binary star system in which one of the components is a white dwarf that accretes matter from its companion. Dwarf novae are dimmer and repeat more frequently than "classical" novae.

<span class="mw-page-title-main">U Geminorum</span> Star in the constellation Gemini

U Geminorum, in the constellation Gemini, is an archetypal example of a dwarf nova. The binary star system consists of a white dwarf closely orbiting a red dwarf. Every few months it undergoes an outburst that greatly increases its brightness. The dwarf nova class of variable stars are often referred to as U Geminorum variables after this star.

<span class="mw-page-title-main">RX Andromedae</span> Cataclysmic variable star system in the constellation Andromeda

RX Andromedae is a variable star in the constellation of Andromeda. Although it is classified as a dwarf nova of the Z Camelopardalis (UGZ) type, it has shown low-luminosity periods typical of VY Sculptoris stars. However, for most of the time it varies from an apparent visual magnitude of 15.1 at minimum brightness to a magnitude of 10.2 at maximum brightness, with a period of approximately 13 days.

<span class="mw-page-title-main">V803 Centauri</span> Star in the constellation Centaurus

V803 Centauri is a cataclysmic binary consisting of a dwarf helium star losing mass to a white dwarf. It is an example of the AM Canum Venaticorum type of cataclysmic variable stars.

<span class="mw-page-title-main">EK Trianguli Australis</span> Star system in the constellation Triangulum Australe

EK Trianguli Australis is a star in the constellation Triangulum Australe. It is a dwarf nova of the SU Ursae Majoris type that officially classified as such in 1980, after the characteristic eruptions of a short eruption and a supereruption were observed in May 1978 and June 1979 respectively. These systems are characterised by frequent eruptions and less frequent supereruptions. The former are smooth, while the latter exhibit short "superhumps" of heightened activity. The distance of the system has been assumed at 180 parsecs from the Solar System, for the donor star. Spectroscopic analysis and calculation gave an estimate of 125 parsecs.

<span class="mw-page-title-main">BV Centauri</span> Star in the constellation Centaurus


BV Centauri is a cataclysmic variable binary star in the constellation Centaurus. It is a dwarf nova, and undergoes rapid increases in brightness that are recurrent with a mean period of 150 days. This period seems to have increased in the last few decades. During quiescence, its visual apparent magnitude is about 13, with variations of a few tenths of magnitude over an orbit due to differences in the star's visible surface area, brightening to a maximum magnitude of 10.7 during outbursts. From its luminosity, it is estimated that the system is about 500 parsecs (1,600 ly) away from Earth. A Gaia parallax of 2.81 mas has been measured, corresponding to about 360 pc.

<span class="mw-page-title-main">SU Ursae Majoris</span> Variable star in the constellation Ursa Major

SU Ursae Majoris, or SU UMa, is a close binary star in the northern circumpolar constellation of Ursa Major. It is a periodic cataclysmic variable that varies in magnitude from a peak of 10.8 down to a base of 14.96. The distance to this system, as determined from its annual parallax shift of 4.53 mas, is 719 light-years. It is moving further from the Earth with a heliocentric radial velocity of +27 km/s.

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

AR Andromedae is a dwarf nova of the SS Cygni type in the constellation Andromeda. Its typical apparent visual magnitude is 17.6, but increases up to 11.0 magnitude during outbursts. The outbursts occur approximately every 23 days.

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

LL Andromedae is a dwarf nova in the constellation Andromeda, discovered during an outburst in 1979. Its typical apparent visual magnitude is 19.4, but undergoes outbursts events when can reach a peak magnitude of 14.3. Since this magnitude is reached during the most powerful outbursts, while less bright outbursts can occur, it is classified as a SU Ursae Majoris variable.

<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">WY Sagittae</span> 1783 Nova seen in the constellation Sagitta

WY Sagittae, also known as Nova Sagittae 1783, is a star in the constellation Sagitta which had a nova eruption visible in 1783. It was discovered on 26 July 1783 by the French astronomer Joseph Lepaute D'Agelet. It is usually difficult to precisely identify novae that were discovered hundreds of years ago, because the positions were often vaguely reported and historically there was not a clear distinction drawn between different sorts of transient astronomical events such as novae and comet apparitions. However D'Agelet observed this nova with a mural quadrant, which produced coordinates accurate enough to allow modern astronomers to identify the star. D'Agelet reported the apparent magnitude of the star as 6, but Benjamin Apthorp Gould, who analysed D'Agelet's records, determined that what D'Agelet called magnitude 6 corresponds to magnitude 5.4 ± 0.4 on the modern magnitude scale, so the nova was visible to the naked eye.

<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">BZ Ursae Majoris</span> Dwarf Nova in the constellation Ursa Major

BZ Ursae Majoris is a dwarf nova star system in the northern circumpolar constellation of Ursa Major. It consists of a white dwarf primary in a close orbit with a red dwarf. The latter star is donating mass, which is accumulating in an accretion disk orbiting the white dwarf. The system is located at a distance of approximately 505 light years from the Sun based on parallax measurements.

<span class="mw-page-title-main">SW Ursae Majoris</span> Variable star in the constellation Ursa Major

SW Ursae Majoris is a cataclysmic binary star system in the northern circumpolar constellation of Ursa Major, abbreviated SW UMa. During quiescence it has an apparent visual magnitude of 16.5–17, which is too faint to be visible to the naked eye. Based on parallax measurements, it is located at a distance of approximately 526 light years from the Sun.

<span class="mw-page-title-main">DW Ursae Majoris</span> Variable star in the constellation Ursa Major

DW Ursae Majoris is an eclipsing binary star system in the northern circumpolar constellation of Ursa Major, abbreviated DW UMa. It is a cataclysmic variable of the SX Sextanis type, consisting of a compact white dwarf that is accreting matter from an orbiting companion star. The brightness of this source ranges from an apparent visual magnitude of 13.6 down to magnitude 18, which is too faint to be viewed with the naked eye. The distance to this system is approximately 1,920 light years based on parallax measurements.

<span class="mw-page-title-main">CR Boötis</span> Star system in the constellation Boötes

CR Boötis is an interacting binary system in the northern constellation of Boötes, abbreviated CR Boo. It is one of the best-known AM Canum Venaticorum stars. The system varies widely in brightness, ranging in apparent visual magnitude from 13.6 down to 17.5. The distance to this system is approximately 1,150 light years from the Sun, based on parallax measurements.

References

  1. ↑ Kato, Taichi (21 September 2015). "WZ Sge-type dwarf novae". Publications of the Astronomical Society of Japan. 67 (6): 108. arXiv: 1507.07659 . doi: 10.1093/pasj/psv077 . Retrieved 6 March 2022.
  2. ↑ Patterson, Joseph; Stone, Geoffrey; Kemp, Jonathan; Skillman, David R.; de Miguel, Enrique; Potter, Michael; Starkey, Donn; Uthas, Helena; Jones, Jim; Slauson, Douglas; Koff, Robert; Myers, Gordon; Menzies, Kenneth; Campbell, Tut; Roberts, George; Foote, Jerry; Vanmunster, Tonny; Cook, Lewis M.; Krajci, Thomas; Ogmen, Yenal; Sabo, Richard; Seargeant, Jim (2018). "Orbital Period Changes in WZ Sagittae". Publications of the Astronomical Society of the Pacific. 130 (988): 064202. arXiv: 1801.00189 . Bibcode:2018PASP..130f4202P. doi:10.1088/1538-3873/aaa7e7. S2CID   119383220 . Retrieved 6 March 2022.
  3. 1 2 3 4 5 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 .
  4. 1 2 3 4 5 "V* WZ Sge". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2009-09-03.
  5. ↑ "GCVS Query=WZ Sge". General Catalogue of Variable Stars @ Sternberg Astronomical Institute, Moscow, Russia . Retrieved 2010-12-01.
  6. ↑ Greenstein, J. L. (1975). "A further list of degenerate stars. VIII". Astrophysical Journal. 196: L117. Bibcode:1975ApJ...196L.117G. doi:10.1086/181758.
  7. 1 2 Krzeminski, W.; Kraft, Robert P (1964). "Binary Stars among Cataclysmic Variables. V. Photoelectric and Spectroscopic Observations of the Ultra-Short Binary Nova WZ Sagittae". Astrophysical Journal. 140: 921–935. Bibcode:1964ApJ...140..921K. doi: 10.1086/147995 .
  8. 1 2 3 4 Steeghs, Danny; Howell, Steve B.; Knigge, Christian; Gänsicke, Boris T.; Sion, Edward M.; Welsh, William F. (September 2007). "Dynamical Constraints on the Component Masses of the Cataclysmic Variable WZ Sagittae". The Astrophysical Journal. 667 (1): 442–447. arXiv: 0706.0987 . Bibcode:2007ApJ...667..442S. doi:10.1086/520702. S2CID   209833493.
  9. 1 2 3 4 Spruit, H. C.; Rutten, R. G. M. (1998). "The stream impact region in the disc of WZ SGE". Monthly Notices of the Royal Astronomical Society. 299 (3): 768–776. Bibcode:1998MNRAS.299..768S. doi: 10.1046/j.1365-8711.1998.01809.x .
  10. 1 2 3 Harrison, Thomas E.; Johnson, Joni J.; McArthur, B. E.; Benedict, G. F.; Szkody, Paula; Howell, Steve B.; Gelino, Dawn M. (2004). "An Astrometric Calibration of the MV-Porb Relationship for Cataclysmic Variables based on Hubble Space Telescope Fine Guidance Sensor Parallaxes". The Astronomical Journal. 127 (1): 460–468. Bibcode:2004AJ....127..460H. CiteSeerX   10.1.1.509.9281 . doi:10.1086/380228. S2CID   45283092.
  11. 1 2 Matthews, O. M.; Speith, R.; Wynn, G. A.; West, R. G. (February 2007). "Magnetically moderated outbursts of WZ Sagittae". Monthly Notices of the Royal Astronomical Society . 375 (1): 105–114. arXiv: astro-ph/0611200 . Bibcode:2007MNRAS.375..105M. doi:10.1111/j.1365-2966.2006.11252.x. S2CID   6180379.
  12. ↑ "WZ Sagittae". Variable Star of the Month series. American Association of Variable Star Observers. September 2001. Retrieved 2009-02-21.
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