Mass Transfer Cycles Research Articles

Microdroplets initiate organic-inorganic interactions and mass transfer in thermal hydrous geosystems

Organic-inorganic interactions regulate the dynamics of hydrocarbons, water, minerals, CO2, and H2 in thermal rocks, yet their initiation remains debated. To address this, we conducted isotope-tagged and in-situ visual thermal experiments. Isotope-tagged studies revealed extensive H/O transfers in hydrous n-C20H42-H2O-feldspar systems. Visual experiments observed water microdroplets forming at 150–165 °C in oil phases near the water-oil interface without surfactants, persisting until complete miscibility above 350 °C. Electron paramagnetic resonance (EPR) detected hydroxyl free radicals concurrent with microdroplet formation. Here we propose a two-fold mechanism: water-derived and n-C20H42-derived free radicals drive interactions with organic species, while water-derived and mineral-derived ions trigger mineral interactions. These processes, facilitated by microdroplets and bulk water, blur boundaries between organic and inorganic species, enabling extensive interactions and mass transfer. Our findings redefine microscopic interplays between organic and inorganic components, offering insights into diagenetic and hydrous-metamorphic processes, and mass transfer cycles in deep basins and subduction zones.

Decades-long variations in NS-LMXBs observed with MAXI/GSC, RXTE/ASM, and Ginga/ASM

Abstract We investigate the decades-long X-ray variations in bright low-mass X-ray binaries containing a neutron star (NS-LMXBs). The light curves of MAXI/GSC and RXTE/ASM cover ∼26 yr, and high-quality X-ray light curves are obtained from 33 NS-LMXBs. Among these, together with Ginga/ASM, two sources (GX 3+1 and GX 9+1) showed an apparent sinusoidal variation with respective periods of ∼5 and ∼10 yr in the 34 yr light curve. Their X-ray luminosities were (1–4) × 1037 erg s−1 in the middle of the NS-LMXB luminosity distribution. Seven other sources (Ser X-1, 4U 1735−444, GX 9+9, 4U 1746−37, 4U 1708−40, 4U 1822−000, and 1A 1246−588) have similar sinusoidal variations, although the profiles (amplitude, period, and phase) are variable. Compering the 21 sources with known orbital periods, one possible cause of the long-term sinusoidal variation might be mass-transfer cycles induced by irradiation to the donor star.

Searching for nova shells around cataclysmic variables – II. A second campaign

ABSTRACT We report on our second campaign to search for old nova shells around cataclysmic variables (CVs). Our aim was to test the theory that nova eruptions cause cycles in the mass transfer rates of CVs. These mass transfer cycles change the behaviour of CVs during their intereruption periods. We examined Hα images of 47 objects and found no new shells around any of the targets. Combining our latest results with those of our previous campaign (Sahman et al.), and the searches by Schmidtobreick et al. and Pagnotta & Zurek, we estimate that the nova-like phase of the mass transfer cycle lasts ∼3000 yr.

Separation and enrichment of Rb(I) in dicyclohexano 18 crown 6(DCH18C6)/PVC polymer inclusion membrane assisted by electric field

The effective extraction of liquid rubidium resources such as salt lake brine and seawater and the recovery of rubidium(I) at the end of the extraction process of lithium resources have always been a challenge in the industry. Two series of polymer inclusion membranes(PDA-PIM and PDT-PIM) were prepared to study the separation and enrichment of Rb(I). PDA-PIM and PDT-PIM used polyvinyl chloride (PVC) and dicyclohexano 18 crown 6(DCH18C6) as carriers, and tricaprylmethylammonium chloride (Aliquat 336) and trioctylphosphine oxide (TOPO) as a plasticizer, respectively. The optimal mass ratio (W/W) of PDA-PIM and PDT-PIM were P25D3.5A25 and P25D3.5T1, respectively. The applied electric field is a core condition for the mass transfer and separation of Rb(I). With the increase of voltage, the permeability coefficient P of Rb(I) and the separation factor (S) relative to Na(I) and K(I) increases. At 180 V, the PRb of PDA-PIM and PDT-PIM were 12.08 and 2.39 µm/s, and the SRB/NA were 11.21 and 14.44. After four mass transfer cycles of PDT-PIM, PRb only decreased by 4.6%. In addition, after 81.5 h of mass transfer, the enrichment ratio of Rb(I) was 3.02 times. These results show the excellent stability and mass transfer performance of PDT-PIM. It's of great significance for low concentration Rb(I) extraction.

Identifying the formation mechanism of redback pulsars

ABSTRACT We analyse the evolution of close binary systems containing a neutron star that lead to the formation of redback pulsars. Recently, there has been some debate on the origin of such systems and the formation mechanism of redbacks may still be considered as an open problem. We show that the operation of a strong evaporation mechanism, starting from the moment when the donor star becomes fully convective (or alternatively since the formation of the neutron star by accretion-induced collapse), produces systems with donor masses and orbital periods in the range corresponding to redbacks with donors appreciably smaller than their Roche lobes, i.e. they have low filling factors (lower than 0.75). Models of redback pulsars can be constructed assuming the occurrence of irradiation feedback. They have been shown to undergo cyclic mass transfer during the epoch at which they attain donor masses and orbital periods corresponding to redbacks, and stay in quasi-Roche lobe overflow conditions with high filling factors. We show that, if irradiation feedback occurs and radio ejection inhibits further accretion on to the neutron star after the first mass transfer cycle, the redback systems feature high filling factors. We suggest that the filling factor should be considered as a useful tool for discriminating among those redback formation mechanisms. We compare theoretical results with available observations and conclude that observations tend to favour models with high filling factors.

Experimental study of a solar adsorption refrigeration system integrated with a compound parabolic concentrator based on an enhanced mass transfer cycle in Kunming, China

A new solar adsorption refrigeration system integrated with a compound parabolic concentrator (CPC) adsorber was proposed. Comparative experiments were conducted to investigate the system behaviour with the enhanced and natural mass transfer cycle under different weather conditions in Kunming, China. The parameter λ (the refrigerant utilization ratio) was defined to describe and compare the effective utilization ratio of the refrigerant in a refrigeration cycle for some different adsorption refrigeration system with a different quantity of the adsorbent and refrigerant. The results show that the system performance level with the enhanced mass transfer cycle is always higher than the system performance level with the natural mass transfer cycle under different weather conditions. On sunny day with a clear sky, the volume of the desorbed refrigerant and the COPsolar with the enhanced mass transfer cycle were increased by 39.2% and 39.0%, respectively, compared with the natural mass transfer cycle. The refrigerant utilization ratio in the CPC adsorption refrigeration system could be improved by 32.5% and 51.2% for the natural and enhanced mass transfer cycle compared with the non-CPC adsorption refrigeration system, respectively. While on sunny day with a partly cloudy sky, the volume of the desorbed refrigerants and the COPsolar with the enhanced mass transfer cycle were improved by 51.7% and 52.8%, respectively, compared with the natural mass transfer cycle. And the refrigerant utilization ratio in the CPC adsorption refrigeration system improved by 33.5% and 61.2%, respectively, for the natural and enhanced mass transfer cycle compared with the non-CPC adsorption refrigeration system.

Evolutionary paths of binaries with a neutron star. I. The case of SAX J1808.4-3658

The evolutionary status of the low mass X-ray binary SAX J1808.4-3658 is simulated by following the binary evolution of its possible progenitor system through mass transfer, starting at a period of $\sim$6.6 hr. The evolution includes angular momentum losses via magnetic braking and gravitational radiation. It also takes into account the effects of illumination of the donor by both the X-ray emission and the spin down luminosity of the pulsar. The system goes through stages of mass transfer and stages during which it is detached, where only the rotationally powered pulsar irradiates the donor. We show that the pulsar irradiation is a necessary ingredient to reach SAX J1808.4-3658 orbital period when the donor mass is reduced to 0.04 - 0.06 M$_\odot$. We also show that the models reproduce important properties of the system, including the orbital period derivative, which is shown to be directly linked to the evolution through mass transfer cycles. Moreover we find that the effects of the irradiation on the internal structure of the donor are non negligible, causing the companion star to be non completely convective at the values of mass observed for the system and significantly altering its long term evolution, as the magnetic braking remains active along the whole evolution.

THE QUASI-ROCHE LOBE OVERFLOW STATE IN THE EVOLUTION OF CLOSE BINARY SYSTEMS CONTAINING A RADIO PULSAR

We study the evolution of close binary systems formed by a normal (solar composition), intermediate mass donor star together with a neutron star. We consider models including irradiation feedback and evaporation. These non-standard ingredients deeply modify the mass transfer stages of these binaries. While models that neglect irradiation feedback undergo continuous, long standing mass transfer episodes, models including these effect suffer a number cycles of mass transfer and detachment. During mass transfer the systems should reveal themselves as low-mass X-ray binaries (LMXBs), whereas when detached they behave as a binary radio pulsars. We show that at these stages irradiated models are in a Roche lobe overflow (RLOF) state or in a quasi-RLOF state. Quasi-RLOF stars have a radius slightly smaller than its Roche lobe. Remarkably, these conditions are attained for orbital period and donor mass values in the range corresponding to a family of binary radio pulsars known as "redbacks". Thus, redback companions should be quasi-RLOF stars. We show that the characteristics of the redback system PSR J1723-2837 are accounted for by these models. In each mass transfer cycle these systems should switch from LMXB to binary radio pulsar states with a timescale of \sim million years. However, there is recent and fast growing evidence of systems switching on far shorter, human timescales. This should be related to instabilities in the accretion disc surrounding the neutron star and/or radio ejection, still to be included in the model having the quasi-RLOF state as a general condition.

On pulsar-driven mass ejection in low-mass X-ray binaries

There is accumulating evidence for mass ejection in low-mass X-ray binaries (LMXBs) driven by radio pulsar activity during X-ray quiescence. We consider the condition for mass ejection by comparing the radiation pressure from a millisecond pulsar, and the gas pressure at the inner Lagrange point or at the surrounding accretion disk. We calculate the critical spin period of the pulsar below which mass ejection is allowed. Combining with the evolution of the mass transfer rate, we present constraints on the orbital periods of the systems. We show that mass ejection could happen in both wide and compact LMXBs. It may be caused by transient accretion due to thermal instability in the accretion disks in the former, and irradiation-driven mass-transfer cycles in the latter.

Is irradiation important for the secular evolution of low-mass X-ray binaries?

It is argued that irradiation in low-mass X-ray binaries (LMXBs) caused by accretion-generated X-rays can not only change the optical appearance of LMXBs but also their outburst properties and possibly also their long-term evolution. Irradiation during an outburst of the outer parts of the accretion disc in a transient LMXB leads to drastic changes in the outburst properties. As far as the secular evolution of such systems is concerned, these changes can result in enhanced loss of mass and angular momentum from the system and, most important, in neutron star LMXBs in a much less efficient use of the transferred matter to spin up the neutron star to a ms-pulsar. Irradiation of the donor star can destabilize mass transfer and lead to irradiation-driven mass transfer cycles, i.e. to a secular evolution which differs drastically from an evolution in which irradiation is ignored. It is argued that irradiation-driven mass transfer cycles cannot occur in systems which are transient because of disc instabilities, i.e. in particular in long-period LMXBs with a giant donor. It is furthermore shown that for irradiating either the disc or the donor star, direct irradiation alone is insufficient. Rather, indirect irradiation via scattered accretion luminosity must play an important role in transient LMXBs and is, in fact, necessary to destabilize mass transfer in short-period systems by irradiating the donor star. Whether and to what extent irradiation in LMXBs does change their secular evolution depends on a number of unsolved problems which are briefly discussed at the end of this article.

Origin and age of pore waters in an actively venting gas hydrate field near Sado Island, Japan Sea: Interpretation of halogen and 129I distributions

A gas hydrate field with highly active venting of methane was recently found near Sado Island in the eastern Japan Sea. Piston cores were collected from active venting sites and nearby locations in the Umitaka Spur–Joetsu Knoll area during two cruises in 2004 (UT04) and 2005 (KY05-08). We report here halogen concentrations and 129I/I ratios in pore waters associated with gas hydrates from these expeditions. The strongly biophilic behavior of I and, to a lesser degree, of Br together with the presence of the long-lived iodine radioisotope ( 129I) allow evaluation of potential source materials for methane in gas hydrate systems. Depth profiles of all three halogens, particularly the very rapid downward increases of Br and I concentrations, strongly suggest input of deep fluids enriched in Br and I, but the profiles also display the effects of gas hydrate formation and dissociation. Although the 129I/I ratios are modified by 129I from seawater and sediments at shallow depth, likely ratios of the deep fluids are estimated to be between 400 × 10 − 15 and 600 × 10 − 15 , equivalent to a Late Oligocene to Early Miocene age. Ages in the active methane venting sites typically are closer to the old end of this range than those in the reference sites. This age range suggests that the methane associated with venting and gas hydrate formation in this area is derived from organic materials accumulated during the initial opening of the Japan Sea. The Umitaka Spur–Joetsu Knoll gas hydrate field demonstrates the movement of deep fluids associated with the release of significant amounts of methane from the seafloor, processes which might be important components of mass transfer and carbon cycle in the shallow geosphere.

Long-term evolution of compact binaries with irradiation feedback

We resume the discussion about irradiation-driven mass transfer cycles in semi-detached compact binary systems. The analytical model that describes the onset of these cycles, which occur on a thermal timescale of the donor star, is reexam- ined. We take into account a contribution of the thermal relaxation which is not related to the irradiation of the donor star and which was neglected in previous studies. Cataclysmic variables (CVs) containing extended giant donors are more stable than previously thought. CVs close to the upper edge of the period gap can undergo cycles at low angular momentum loss rates, as has been suggested by recent magnetic braking prescriptions, while they are stable for high braking rates. A model for the irradiation geometry that takes into account surface elements near the terminator of the donor star indicates that possibly also low-mass X-ray binaries (LMXBs) can undergo mass transfer cycles. Regarding the braking rate, which is necessary to drive cycles, the same restrictions apply for short period LMXBs as for short period CVs. We confirm that LMXBs containing giants can undergo cyles. In terms of the irradiation efficiency parameter α, CVs are susceptible to irradiation instability for α 0.1 while LMXBs are susceptible for α 0.1. The predictions of the analytical model are checked by the first long-term evolutionary computations of systems undergoing mass transfer cycles with full 1D stellar models. For unevolved main sequence (MS) and giant donors the analytic model provides reasonable values for the boundaries of the stable and unstable regions while CVs containing highly evolved MS donors are more stable than expected at high braking rates. Taking into account irradiation, the minimum period of CVs is increased by up to 1−2 min, depending on α.

Thermal stability and nova cycles in permanent superhump systems

Archival data on permanent superhump systems are compiled to test the thermal stability of their accretion discs. We find that their discs are almost certainly thermally stable as expected. This result confirms Osaki's suggestion that permanent superhump systems form a new subclass of cataclysmic variables (CVs), with relatively short orbital periods and high mass-transfer rates. We note that if the high accretion rates estimated in permanent superhump systems represent their mean secular values, then their mass-transfer rates cannot be explained by gravitational radiation, therefore, either magnetic braking should be extrapolated to systems below the period gap or they must have mass-transfer cycles. Alternatively, a new mechanism that removes angular momentum from CVs below the gap should be invoked. We suggest applying the nova cycle scenarios offered for systems above the period gap to the short orbital period CVs. Permanent superhumps have been observed in the two non-magnetic ex-novae with binary periods below the gap. Their post-nova magnitudes are brighter than their pre-outburst values. In one case (V1974 Cyg) it has been demonstrated that the pre-nova should have been a regular SU UMa system. Thus, it is the first nova whose accretion disc was observed to change its thermal stability. If the superhumps in this system indicate persistent high mass-transfer rates rather than a temporary change induced by irradiation from the hot post-nova white dwarf, it is the first direct evidence for mass-transfer cycles in CVs. The proposed cycles are driven by the nova eruption.

Mass Transfer Cycles in Close Binaries with Evolved Companions

We give a global analysis of mass transfer variations in low-mass X-ray binaries and cataclysmic variables whose evolution is driven by the nuclear expansion of the secondary star. We show that limit cycles caused by irradiation of the secondary by the accreting primary are possible in a large class of these binaries. In the high state, the companion transfers a large fraction of its envelope mass on a thermal timescale. In most cases this implies super-Eddington transfer rates and would thus probably lead to common-envelope evolution and the formation of an ultrashort-period binary. Observed systems with (sub)giant secondaries stabilize themselves against this possibility either by being transient or by shielding the secondary from irradiation in some way.

Secular Evolution of Cataclysmic Variables with Irradiation-Induced Mass Transfer

The possible importance of the reaction of a low-mass star to external irradiation for the long-term evolution of compact binaries has been noted only rather recently; first in the context of the evolution of low-mass X-ray binaries (e.g. Podsiadlowski 1991; Harpaz & Rappaport 1991; Frank, King & Lasota 1992; Hameury et al. 1993) and subsequently by Ritter, Zhang & Kolb (1995a,b, hereafter RZK) also for the evolution of cataclysmic variables (CVs). Based on a simple model for describing the reaction of a low-mass star to irradiation RZK showed that CVs can be dynamically unstable against irradiation-induced mass transfer and that, as a consequence of this, mass transfer could occur via cycles in which phases of high, irradiation-enhanced mass transfer alternate with phases of little or no mass transfer. The occurrence of such mass transfer cycles in CVs was subsequently discussed from a more general point of view by King (1995) and King et al. (1995). Whereas the possibility of mass transfer cycles in CVs is now fully recognised, the question as to which systems can undergo such cycles and which cannot has not yet been addressed in detail. It is the purpose of this contribution to provide at least a partial answer to this question.

Mass transfer cycles in cataclysmic variables

It is well known that in cataclysmic variables the mass transfer rate must fluctuate about the evolutionary mean on timescales too long to be directly observable. We show that limit-cycle behavior can occur if the radius change of the secondary star is sensitive to the instantaneous mass transfer rate. The only reasonable way in which such a dependence can arise is through irradiation of this star by the accreting component. The system oscillates between high states, in which irradiation causes slow expansion of the secondary and drives an elevated transfer rate, and low states, in which this star contracts.