Post common envelope binary
{{Short description|Binary system consisting of a white dwarf and a main sequence star or a brown dwarf}}
File:HD 101584.jpg is a suspected post-common envelope binary. The engulfed companion triggered an outflow of gas, creating the nebula seen by ALMA.]]
File:Common envelope phase - ejection or merger.svg. Middle: The companion is engulfed; the core and companion spiral towards one another inside a common envelope. Bottom: The envelope is ejected and forms a PCEB or the two stars merge.]]
A post-common envelope binary (PCEB) or pre-cataclysmic variable is a binary system consisting of a white dwarf or hot subdwarf and a main-sequence star or a brown dwarf.{{Cite journal|last1=Casewell|first1=S. L.|last2=Braker|first2=I. P.|last3=Parsons|first3=S. G.|last4=Hermes|first4=J. J.|last5=Burleigh|first5=M. R.|last6=Belardi|first6=C.|last7=Chaushev|first7=A.|last8=Finch|first8=N. L.|last9=Roy|first9=M.|last10=Littlefair|first10=S. P.|last11=Goad|first11=M.|date=2018-05-01|title=The first sub-70 minute non-interacting WD-BD system: EPIC212235321|journal=Monthly Notices of the Royal Astronomical Society|volume=476|issue=1|pages=1405–1411|doi=10.1093/mnras/sty245|doi-access=free |issn=0035-8711|arxiv=1801.07773|bibcode=2018MNRAS.476.1405C|s2cid=55776991}} The star or brown dwarf shared a common envelope with the white dwarf progenitor in the red giant phase. In this scenario the star or brown dwarf loses angular momentum as it orbits within the envelope, eventually leaving a main-sequence star and white dwarf in a short-period orbit. A PCEB will continue to lose angular momentum via magnetic braking and gravitational waves and will eventually begin mass-transfer, resulting in a cataclysmic variable. While there are thousands of PCEBs known, there are only a few eclipsing PCEBs, also called ePCEBs.{{Cite journal|last1=Muirhead|first1=Philip S.|last2=Vanderburg|first2=Andrew|last3=Shporer|first3=Avi|last4=Becker|first4=Juliette|last5=Swift|first5=Jonathan J.|last6=Lloyd|first6=James P.|last7=Fuller|first7=Jim|last8=Zhao|first8=Ming|last9=Hinkley|first9=Sasha|last10=Pineda|first10=J. Sebastian|last11=Bottom|first11=Michael|date=2013-04-02|title=Characterizing the Cool KOIs. V. KOI-256: A Mutually Eclipsing Post-Common Envelope Binary|journal=The Astrophysical Journal|volume=767|issue=2|pages=111|doi=10.1088/0004-637X/767/2/111|issn=0004-637X|arxiv=1304.1165|bibcode=2013ApJ...767..111M|s2cid=30368826}} Even more rare are PCEBs with a brown dwarf as the secondary. A brown dwarf with a mass lower than 20 {{Jupiter mass|link=true}} might evaporate during the common envelope phase and therefore the secondary is supposed to have a mass higher than 20 {{Jupiter mass}}.{{Cite web|url=https://www.eso.org/public/news/eso0628/|title=A Sub-Stellar Jonah – Brown Dwarf Survives Being Swallowed|last=|website=www.eso.org|language=en|access-date=2020-02-02}}
The material ejected from the common envelope forms a planetary nebula. One in five planetary nebulae are ejected from common envelopes, but this might be an underestimate. A planetary nebula formed by a common envelope system usually shows a bipolar structure.{{Cite journal|last1=De Marco|first1=Orsola|author1-link=Orsola De Marco|last2=Reichardt|first2=T.|last3=Iaconi|first3=R.|last4=Hillwig|first4=T.|last5=Jacoby|first5=G. H.|last6=Keller|first6=D.|last7=Izzard|first7=R. G.|last8=Nordhaus|first8=J.|last9=Blackman|first9=E. G.|date=October 2017|title=Post-common envelope PN, fundamental or irrelevant?|journal= Proceedings of the International Astronomical Union|language=en|volume=323|pages=213–217|doi=10.1017/S1743921317002149|arxiv=1612.03515|bibcode=2017IAUS..323..213D|s2cid=119069917|issn=1743-9221}}
The suspected PCEB HD 101584 is surrounded by a complex nebula. During the common envelope phase the red giant phase of the primary was terminated prematurely, avoiding a stellar merger. The remaining hydrogen envelope of HD 101584 was ejected during the interaction between the red giant and the companion and it now forms the circumstellar medium around the binary.
Many eclipsing post-common envelope binaries show variations in the timing of eclipses, the cause of which is uncertain. While orbiting exoplanets are often proposed as the cause of these variations, planetary models often fail to predict subsequent changes in eclipse timing. Other proposed causes, such as the Applegate mechanism, often cannot fully explain the observed eclipse timing variations either.
List of post-common envelope binaries
{{Expand list|date=February 2020}}Sorted by increasing orbital period.
| class="wikitable"
|+ !Name !Period !Secondary !Note |
| SDSS J1205-0242
|low-mass star or brown dwarf |shortest period PCEB (as of 2017) |
| WD 0137−349
|116 minutes |brown dwarf |first confirmed PCEB with a brown dwarf as a companion |
| CSS21055
|brown dwarf |eclipsing binary |
| SDSS 1557
|brown dwarf |circumbinary debris disk with a polluted white dwarf |
| V470 Camelopardalis (HS0705+6700) |{{convert|0.096|d|h|disp=out|abbr=off}} |red dwarf |eclipsing binary |
| NY Virginis
|{{convert|0.101|d|h|disp=out|abbr=off}} |red dwarf |eclipsing binary |
| NSVS 14256825
|{{convert|0.110|d|h|disp=out|abbr=off}} |red dwarf |eclipsing binary |
| HW Virginis
|{{convert|0.117|d|h|disp=out|abbr=off}} |red dwarf |eclipsing binary |
| NN Serpentis
|eclipsing binary |
| WD 0837+185
|brown dwarf |extreme mass ratio of the progenitor, with the primary having a mass of 3.5-3.7 {{Solar mass}} and the secondary 25-30 {{Jupiter mass}} |
| RR Caeli
|{{convert|0.304|d|h|disp=out|abbr=off}} |red dwarf |eclipsing binary |
| DE Canum Venaticorum
|{{convert|0.364|d|h|disp=out|abbr=off}} |red dwarf |eclipsing binary |
| central source of Hen 2-11
|planetary nebula and eclipsing binary |
| K 1-2
| |
| central source of Fleming 1
|white dwarf |planetary nebula |
| KOI-256
|red dwarf |eclipsing binary |
| central source of NGC 2392
|hot white dwarf |planetary nebula and x-ray binary |
| central source of NGC 5189
|massive white dwarf |planetary nebula; primary is a low-mass Wolf-Rayet star |
| central source of NGC 2346
|>3.5 {{Solar mass}} sub-giant |planetary nebula; one of the longest period PCEB which could host the most massive secondary |
| HD 101584
|red dwarf or white dwarf |the engulfment of the companion probably triggered gas to outflow, creating the nebula, seen with Hubble and ALMA; primary is a post-RGB star |
See also
References
{{Reflist|refs=
{{cite journal |last1=Pulley |first1=D. |last2=Sharp |first2=I. D. |last3=Mallett |first3=J. |last4=von Harrach |first4=S. |date=August 2022 |title=Eclipse timing variations in post-common envelope binaries: Are they a reliable indicator of circumbinary companions? |journal=Monthly Notices of the Royal Astronomical Society |volume=514 |issue=4 |pages=5725–5738 |doi=10.1093/mnras/stac1676 |doi-access=free |arxiv=2206.06919 |bibcode=2022MNRAS.514.5725P}}
}}