Supersoft X-ray source: Difference between revisions

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As of early 2005, more than 100 SSSs have been reported in ~20 external galaxies, the [[Large Magellanic Cloud]] (LMC), [[Small Magellanic Cloud]] (SMC), and the [[Milky Way]] (MW).<ref name=Kahabka/> Those with luminosities below ~3 x 10³⁸ [[erg]]/s are consistent with steady [[Stellar surface fusion|nuclear burning]] in accreting [[white dwarf]]s (WD)s or post-novae.<ref name=Kahabka/> There are a few SSS with luminosities ≥10³⁹ erg/s.<ref name=Kahabka/>

Super softSupersoft X-rays are believed to be produced by steady [[nuclear fusion]] on a [[white dwarf]]'s surface of material pulled from a [[binary star|binary companion]],<ref name=SSXSmpe>{{ cite web |title=Super Soft X-ray Sources - Discovered with ROSAT |url=http://www.mpe.mpg.de/~jcg/sss/sss_high.html |author=Max Planck Institute for Extraterrestrial Physics }}</ref> the so-called close-binary supersoft source (CBSS).<ref name=Greiner/> This requires a flow of material sufficiently high to sustain the fusion. Contrast this with the [[nova]], where less flow causes the material to only fuse sporadically. Super softSupersoft X-ray sources can evolve into [[type Ia supernova]], where a sudden fusion of material destroys the white dwarf, and neutron stars, through collapse.<ref name=SSXSws>{{ cite web |title=Proceedings of the Workshop on Supersoft X-ray Sources |url=http://www.mpe.mpg.de/~jcg/sss/sssw.html |author=Max Planck Institute for Extraterrestrial Physics }}</ref>

Super softSupersoft X-ray sources were first discovered by the [[Einstein Observatory]]. Further discoveries were made by [[ROSAT]].<ref name=SSXScat>{{ cite web |title=Catalog of Supersoft X-ray Sources |url=http://www.aip.de/~jcg/sss/ssscat.html |url-status=dead |archiveurl=https://web.archive.org/web/20071128104800/http://www.aip.de/~jcg/sss/ssscat.html |archivedate=2007-11-28 }}</ref> Many different classes of objects emit supersoft X-radiation (emission dominantly below 0.5 keV).<ref name=Greiner/>

==Luminous supersoft X-ray sources==

Luminous super softsupersoft X-ray sources have a characteristic blackbody temperature of a few tens of eV (~20–100 eV)<ref name=Kahabka>{{ cite journal |author=Kahabka P |title=Supersoft X-ray sources |journal= Advances in Space Research|date=Dec 2006 |volume=38 |issue=12 |pages=2836–9 |doi=10.1016/j.asr.2005.10.058 |bibcode=2006AdSpR..38.2836K}}</ref> and a bolometric luminosity of ~10³⁸ erg/s (below ~ 3 x 10³⁸ erg/s).<ref name=White>{{ cite journal|display-authors=4|author=White NE|author2=Giommi P|author3=Heise J|author4=Angelini L|author5=Fantasia S|title=RX J0045.4+4154: A Recurrent Supersoft X-ray Transient in M31|journal= The Astrophysical Journal|volume=445|pages=L125|url=http://lheawww.gsfc.nasa.gov/users/white/wgacat/apjl.html|doi=10.1086/187905|bibcode=1995ApJ...445L.125W|date=1995|url-status=dead|archiveurl=https://web.archive.org/web/20090703002924/http://lheawww.gsfc.nasa.gov/users/white/wgacat/apjl.html|archivedate=2009-07-03}}</ref><ref name=Kahabka/>

Apparently, luminous SSXSs can have equivalent blackbody temperatures as low as ~15 eV and luminosities ranging from 10³⁶ to 10³⁸ erg/s.<ref name=KahabkaHeuvel>{{ cite journal |author=Kahabka P|author2=van den Heuvel EPJ |title=Luminous Supersoft X-Ray Sources |journal= Annual Review of Astronomy and Astrophysics|date=1997 |volume=35 |issue=1 |pages=69–100 |bibcode=1997ARA&A..35...69K |doi=10.1146/annurev.astro.35.1.69 |s2cid=70774203 |url=https://pure.uva.nl/ws/files/4067674/37187_162193y.pdf }}</ref> The numbers of luminous SSSs in the disks of ordinary spiral galaxies such as the MW and M31 are estimated to be on the order of 10³.<ref name=KahabkaHeuvel/>

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==Milky Way SSXSs==

SSXSs have now been discovered in our galaxy and in globular cluster M3.<ref name=White/> MR Velorum (RX J0925.7-4758) is one of the rare MW super softsupersoft X-ray binaries.<ref name=Greiner>{{ cite journal |doi=10.1016/S1384-1076(00)00018-X |author=Greiner J |title=Catalog of supersoft X-ray sources |journal= New Astronomy|date=2000 |volume=5 |issue=3 |pages=137–41 |url=http://www.mpe.mpg.de/~jcg/sss/ssscat.html |arxiv = astro-ph/0005238 |bibcode = 2000NewA....5..137G |s2cid=52241439 }}</ref> "The source is heavily reddened by interstellar material, making it difficult to observe in the blue and ultraviolet."<ref name=Schmidtke>{{ cite journal |doi=10.1086/322155 |author=Schmidtke PC |author2=Cowley AP|author2-link=Anne Cowley |title=Synoptic Observations of the Supersoft Binary MR Velorum (RX J0925.7-4758): Determination of the Orbital Period |journal= The Astronomical Journal|date=Sep 2001 |volume=122 |issue= 3|pages=1569–71 |url=http://www.iop.org/EJ/article/1538-3881/122/3/1569/201190.text.html |bibcode=2001AJ....122.1569S|doi-access=free |url-access=subscription }}</ref> The period determined for MR Velorum at ~4.03 d is considerably longer than that of other supersoft systems, which is usually less than a day.<ref name=Schmidtke/>

==Close-binary supersoft source (CBSS)==

The CBSS model invokes steady [[Stellar surface fusion|nuclear burning on the surface]] of an accreting [[white dwarf]] (WD) as the generator of the prodigious super softsupersoft X-ray flux.<ref name=Greiner/> As of 1999, eight SSXSs have orbital periods between ~4 hr and 1.35 d: RX J0019.8+2156 (MW), [[RX J0439.8−6809|RX J0439.8-6809]] (MW halo near LMC), RX J0513.9-6951 (LMC), RX J0527.8-6954 (LMC), RX J0537.7-7034 (LMC), CAL 83 (LMC), CAL 87 LMC), and 1E 0035.4-7230 (SMC).<ref name=Greiner/>

==Symbiotic binary==

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==Noninteracting white dwarfs==

The youngest, hottest WD, [[KPD 0005+5106]], is very close to 100,000 K, of type DO and is the first single WD recorded as an X-ray source with ROSAT.<ref name=Fleming>{{ cite journal |author=Fleming TA|author2=Werner K |author3=Barstow MA |journal= The Astrophysical Journal|date=October 1993 |volume=416 |pages=L79 |title=Detection of the First Coronal X-Ray Source about a White Dwarf |bibcode=1993ApJ...416L..79F |doi=10.1086/187075 |doi-access=free }}</ref><ref name=Werner1994>{{ cite journal |title=Spectral analysis of the hottest known helium-rich white dwarf: KPD 0005+5106 |author=Werner |journal= Astronomy and Astrophysics|date=1994 |volume=284 |pages=907 |bibcode = 1994A&A...284..907W }}</ref>

==Cataclysmic variables==

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X-rays from magnetic cataclysmic variables are common because accretion provides a continuous supply of coronal gas.<ref name=Trimble/> A plot of number of systems vs. orbit period shows a statistically significant minimum for periods between 2 and 3 hr which can probably be understood in terms of the effects of magnetic braking when the companion star becomes completely convective and the usual dynamo (which operates at the base of the convective envelope) can no longer give the companion a magnetic wind to carry off angular momentum.<ref name=Trimble/> The rotation has been blamed on asymmetric ejection of planetary nebulae and winds<ref name=Spruit>{{ cite journal |title=Origin of the rotation rates of single white dwarfs |author=Spruit HC |date=1998 |journal= Astronomy and Astrophysics|volume=333 |pages=603 |arxiv = astro-ph/9802141 |bibcode = 1998A&A...333..603S }}</ref> and the fields on in situ dynamos.<ref name=Schmidt97>{{ cite journal |doi=10.1086/304746 |author=Schmidt GD |author2=Grauer AD |date=1997 |title=Upper Limits for Magnetic Fields on Pulsating White Dwarfs |journal= The Astrophysical Journal|volume=488 |issue=2 |pages=827–830 |bibcode=1997ApJ...488..827S|doi-access=free }}</ref> Orbit and rotation periods are synchronized in strongly magnetized WDs.<ref name=Trimble/> Those with no detectable field never are synchronized.

With temperatures in the range 11,000 to 15,000 K, all the WDs with the most extreme fields are far too cool to be detectable EUV/X-ray sources, e.g., Grw +70°8247, LB 11146, SBS 1349+5434, PG 1031+234 and GD 229.<ref name=Schmidt95>{{ cite journal |doi=10.1086/175962 |author=Schmidt GD |author2=Smith PS |title=A Search for Magnetic Fields among DA White Dwarfs |journal= The Astrophysical Journal|date=1995 |volume=448 |pages=305 |bibcode=1995ApJ...448..305S|doi-access=free }}</ref>

Most highly magnetic WDs appear to be isolated objects, although G 23–46 (7.4 MG) and LB 1116 (670 MG) are in unresolved binary systems.<ref name=Barstow/>

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In the SMC, 1E 0056.8-7154 is a WD with bolometric luminosity of 2 x 10³⁷ that has a planetary nebula associated with it.<ref name=Greiner/>

==Super softSupersoft active galactic nuclei==

Supersoft active galactic nuclei reach luminosities up to 10⁴⁵ erg/s.<ref name=Greiner/>

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==Large amplitude outbursts==

Large amplitude outbursts of super softsupersoft X-ray emission have been interpreted as [[tidal disruption event]]s.<ref name=Komossa>{{ cite journal |title=Discovery of a giant and luminous X-ray outburst from the optically inactive galaxy pair RX J1242.6-1119 |author=Komossa S|author2=Greiner J |journal=Astron. Astrophys. |volume=349 |date=1999 |pages=L45 |arxiv = astro-ph/9908216 |bibcode = 1999A&A...349L..45K }}</ref>

== See also ==

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{{white dwarf}}

[[Category:Astronomical X-ray sources|*super softsupersoft X-ray source]]

[[Category:X-ray astronomy]]