The angular momentum of a binary star system decreases over time
the verdict
INSUFFICIENT LEANING
refutedsupported
the weight of evidence
8 sources for · 0 against
Astrophysical studies report that many binary systems undergo angular momentum loss mechanisms leading to decreasing orbital periods, while other binary systems experience period increases or conservative conservation laws.
Context. Current scenarios for the evolution of interacting close binaries – such as cataclysmic variables (CVs) – rely mainly on our understanding of low-mass star angular momentum loss (AML) mechanisms. The coupling of stellar wind with its magnetic field, i.e., magnetic braking, is the most promising mechanism believed to drive AML in these stars. There are basically two properties thought to drive magnetic braking: the stellar magnetic field and the stellar wind. Understanding the mechanisms that drive AML therefore requires a comprehensive understanding of these two properties as well. Aims. RR Cae is a well-known nearby (d = 20pc) eclipsing DA+M binary with an orbital period of P = 7.29h. The system harbors a metal-rich cool DA white dwarf (WD) and a highly active M-dwarf locked in synchronous rotation. The metallicity of the WD suggests that wind accretion is taking place, which provides a good opportunity to obtain the mass-loss rate of the M-dwarf component. We aim to reach a better understanding of the AML mechanisms in close binaries by characterizing the relevant properties of the M-dwarf component of this system. Methods. We analyzed multi-epoch time-resolved high-resolution spectra of RR Cae in search for traces of magnetic activity and accretion. We selected a number of well-known chromospheric activity indicators and studied their phasedependence and long-term behavior. Indirect-imaging tomographic techniques were also applied to provide the surface brightness distribution of the magnetically active M-dwarf. The blue part of the spectrum was modeled using a stateof-the-art atmosphere model to constrain the WD properties and its metal enrichment. The latter was used to improve the determination of the mass-accretion rate from the M-dwarf wind. Results. Doppler imaging of the M-dwarf component of RR Cae reveals a polar feature similar to those observed in fast-rotating solar-type stars. Analysis of tomographic reconstruction of the Hα emission line reveals two components, one traces the motion of the M dwarf and is generated by chromospheric activity, while the other clearly follows the motion of the WD. The presence of metals in the WD spectrum suggests that this component arises from accretion of the M-dwarf wind. A model fit to the WD spectrum provides Teff = (7260 ± 250)K and log g = (7.8 ± 0.1)dex with a metallicity of < log[X/X ] >= (−2.8±0.1)dex. This maps into a mass-accretion rate of Ṁacc = (7±2)×10−16M ·yr−1 onto the surface of the WD.
I measure and collect timings of phase markers (like eclipse times) for the orbits of 25 X-ray binaries (XRBs) so as to calculate the steady evolutionary period change ( Ṗ ). I combine these with my observed Ṗ measures from 52 cataclysmic variables (CVs). Further, I subtract out the contributions from gravitational radiation ( ṖGR ) and mass transfer ( Ṗmt ), deriving the period change from the residual unknown angular momentum loss ( ṖAML = Ṗ – ṖGR – Ṗmt ). I have ṖAML measures for 77 XRBs and CVs, with these being direct measures of the driver of binary evolution. The venerable magnetic braking model of binary evolution has its most fundamental predictions tested, with most systems having predictions wrong by over 1 order of magnitude. Other proposed mechanisms to explain the angular momentum loss (AML) also fail, so we are left with no known mechanism that dominates the AML. An alternative path to the AML law is empirical, where my ṖAML measures are fitted to a power law involving the fundamental binary properties. With this, the dominant AML law for systems with orbital periods (P) from 0.13–1.0 day is ṖAML=−1500×10−12P1.29Mprim2.75Mcomp−1.00Ṁ−80.43 , in appropriate units. Similar AML laws for binaries below the period gap and for binaries with P > 1.0 day are derived. These three AML laws are of good accuracy and are the best representations of the actual evolution for all 77 XRBs and CVs of all classes, so the three taken together can be called “universal.”
SMC X-1 is a high-mass X-ray binary with an orbital period of 3.9 days. The mass of the neutron star is as low as ∼1M☉, suggesting that it was likely formed through an electron-capture supernova rather than an iron-core collapse supernova. From the present system configurations, we argue that the orbital period at the supernova was ≲ 10 days. Since the mass transfer process between the neutron star's progenitor and the companion star before the supernova should have increased the orbital period to tens of days, a mechanism with efficient orbit angular momentum loss and relatively small mass loss is required to account for its current orbital period. We have calculated the evolution of the progenitor binary systems from zero-age main sequence to the pre-supernova stage with different initial parameters and various mass and angular momentum loss mechanisms. Our results show that the outflow from the outer Lagrangian point or a circumbinary disk formed during the mass transfer phase may be qualified for this purpose. We point out that these mechanisms may be popular in binary evolution and significantly affect the formation of compact star binaries.
The hierarchical multiple system XY Leo, despite nearly 90 yr of observations, remains enigmatic. It offers a unique testbed for close binary evolution, involving processes like mass transfer, angular momentum loss, and the von Zeipel–Lidov–Kozai mechanism. Previously identified as a quadruple system, XY Leo shows long-term orbital period modulations. Our new ground-based and Transiting Exoplanet Survey Satellite data suggest this may stem from either magnetic cycles or the influence of an unseen companion. While the latter remains speculative, both scenarios are discussed within a unified framework. Using all available photometric and spectroscopic data, we derived ultraprecise physical parameters for the contact binary XY Leo A as M _A1 = 0.629 ± 0.009 M _⊙ , M _A2 = 0.865 ± 0.012 M _⊙ , R _A1 = 0.739 ± 0.007 R _⊙ , R _A2 = 0.855 ± 0.008 R _⊙ , L _A1 = 0.271 ± 0.026 L _⊙ , and L _A2 = 0.288 ± 0.030 L _⊙ and orbital separation a _A = 2.078 ± 0.010 R _⊙ based on simultaneous solutions of light and radial velocity curves. The detached binary subsystem XY Leo B is confirmed to be on a wide ∼20 yr orbit around the contact system. A second ∼23 yr modulation is also detected, which may stem from either stellar magnetic activity or an additional, unseen companion. After removing both trends, a coherent residual modulation with a characteristic timescale of 14.2 ± 0.8 yr remains in the O – C diagram, consistent with a magnetic activity cycle of Applegate type. We modeled XY Leo A wi
We present a study on low-mass contact binaries (LMCB) with orbital periods shorter than 0.3 days and total mass lower than about 1.4 solar mass. We show that such systems have a long pre-contact phase, which lasts for 8-9 Gyrs, while the contact phase takes only about 0.8 Gyr, which is rather a short fraction of the total life. With low mass transfer rate during contact, moderate mass ratios prevail in LMCBs since they do not have enough time to reach extreme mass ratios often observed in higher mass binaries. During the whole evolution both components of LMCBs remain within the MS band. The evolution of cool contact binaries towards merging is controlled by the interplay between the evolutionary expansion of the less massive component resulting in the mass transfer to the more massive component and the angular momentum loss from the system by the magnetized wind. In LMCB the angular momentum loss prevails. As a result, the orbital period systematically decreases until the binary overflows the outer critical Roche surface and the components merge into a single fast rotating star of a solar type surrounded by a remnant disk carrying excess angular momentum. The disk can be a place of planet formation with the age substantially lower than the age of a host star. The calculated theoretical tracks show good agreement with the physical properties of LMCB from the available observations. Estimates of the frequency of occurrence of LMCB and the merger formation rate indicate that a
A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars are among
A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars are among the most important objects in astrophysics because they allow direct measurement of stellar masses and test theories of stellar evolution. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate
The Applegate mechanism explains long term orbital period variations seen in certain eclipsing binaries. As a main-sequence star goes through an activity cycle, the outer layers of the star are subject to a magnetic torque changing the distribution of angular momentum, resulting in a change in the star's oblateness. The orbit of the stars in the binary pair is gravitationally coupled to their shape changes, so that the period shows modulations (typically on the order of ∆P/P ~ 10−5) on the same time scale as the activity cycles (typically on the order of decades).
Another phenomenon observed in some Algol binaries has been monotonic period increases. This is quite distinct from the far more common observations of alternating period increases and decreases explained by the Applegate mechanism. Monotonic period increases have been attributed to mass transfer, usually (but not always) from the less massive to the more massive star
(p) and position vectors angular (L) ee momentum vectors Linear (Vv) and angular (@ ( ) eae) Torque vectors … Under a Net Torque 309 10.8 Angular Momentum 313 10.9 Conservation of Angular Momentum 316 10.10 Precessional … the end of a problem and deter- mine if it seems reasonable. If you are calculating the mass of a house-
mechanics, the moment of momentum of the entire system is a constant quantity. This law is also expressed in three equations, one for each of the three planes
Everything we examined (8) — 7 independent sources
This check searched the claim as stated. It did not run a separate search for evidence against it.