Formation and Evolution of LMXBs

Formation and Evolution of LMXBs [@TaurisvandenHeuvel+2023]

← Physics of Binary Star Evolution

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Rare formation process

• Due to the lower mass of the donor star when compared to the accretor, mass transfer in LMXBs can be long stable on large timescales, such as … \begin{list}{-}{}
• nuclear (fuel of the star)
• orbital shrinking due to loss of angular momentum

\item When comapring the theoretical lifespan of them, to the quanity obsreved, we find that they have formation rate of $10^{-7}{\text{yr}}^{-1}$ \item one out of $\sim 10^5$ finishes in a LMXB system, whereas HMXBS it is one out of ten \end{list}

Possible formation channels

• AIC of a massive WD reaching Chandrasekhar Limit sec:LMXBAICFormation
• Formation Via Common Envelope Evolution sec:LMXBFormViaCE

Formation Via Common Envelope Evolution

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Deduced by looking at the Her x-1 system

• far distance (3kpc) from the galactic plane, but a family young star
• must have experienced something to launch hit out of the plane at 120kms${}^{-1}$
• This was from an SN, most likely some sort of natal-kick
• The velocity of this NS is much greater than a possible value formed via AIC on a WD

Evolutionary Steps In this config the initial system consists of a relatively massive star ($\sim 12\text{to}15M_{\odot }$) together with a $2M_{\odot }$ star in a wide orbit ($P_{orb}>1yr$)

AIC of a massive WD reaching Chandrasekhar Limit

Origin from a HMXB with a much lower mass companion (triple star system)