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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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]]