Diamond Midnight: Star Stories

The following story is the forth in a series of stories about stars. A table of contents of more star stories is located here.

This information is not copyright. Feel free to use it in whatever project you like, so long as the project is not commercial. A link or APA or MLA bibliographic reference to this page would be appreciated if you use any of this information. Also drop me a line, just so I know who is interested in this page. If the page is popular, I may add a few others.

You can reference this page as: Urban, Shawn. (2007). Frolicking Suns: BK Lyncis: King of the Dancers. Diamond Midnight: Star Stories. http://www.ualberta.ca/~urban/Samples/Stars/Dancer.htm.

Thanks, enjoy and keeping watching the skies,
Shawn Urban

Frolicking Suns
BK Lyncis: King of the Dancers
BK Lyncis

BK Lyncis explodes or bursts at regular intervals. It is simply cataclysmic, releasing energy rapidly into surrounding space. It is one of four such separate stars in Lynx, except that BK Lyncis is not alone. It is accompanied by a cluster of seven other cataclysmic novalike stars, Henden+Honeycutts 2 to 8. This cluster in turn is set against a cluster of galaxies, Abell 779. It's as if Abell 779 were the stage for a troupe of dancers and BK Lyncis, Henden+Honeycutt 1, were the king of this troupe.

The explosions of BK Lyncis are between those of unusually rapid novas (typified by fewer, larger explosions) and rare dwarf-novas (typified by more, smaller explosions). The majority of explosive and novalike variables are close binary systems. The binary stars of BK Lyncis orbit their common center of gravity unusually fast for a nova system. In usual circumstances, each nova would consume energy the stars would use to orbit each other. The stars would move further apart and slow down. In addition, novas would become less frequent. In BK Lyncis and other novalike variables, anomalously high loss of angular momentum means that instead of separating and slowing down the stars move closer and orbit faster. This implies an external mechanism for sapping the angular momentum of the stars. This mechanism may be magnetic stellar-wind braking, where the stellar winds blown off by the exploding stars actually drag the stars and sap their angular momentum. This may be the first evidence of magnetic activity occurring in the faintest M dwarfs, at least in an interacting M binary.

The components of BK Lyncis likely interact, mutually influencing the evolution of each star. The hot dwarf component of such systems is often surrounded by an accretion disk formed by matter lost by the other, cooler, and more extended component.

BK Lyncis Statistics

Novalike variable
Location (J2000) RA: 9h 20m 8.6s Dec: +33o 57' 11"
Amplitude of magnitude change: 0.32 mag
Change in brightness: 1.34 times minimum
Maximum magnitude (during explosion only): 14.17
Minimum magnitude (average): 14.49
Spectral class (Sun=G2V): NV (red carbon dwarf star)
B-V color index (Sun=0.62): 0.61 (at minimum mag)

Summary of novalike variables in the Lynx:

NameNormal MagnitudeMagnitude on Explosion Spectral ClassColor
BH*16.313.7CV?
BI* 13.3012.93?0.23
BK* 14.4914.17NV0.61
BP*14.3314.19CV?

   * BH and BP are also eclipsing variables

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