Edge Of Disk Research Articles

ALMA and VLBA views on the outflow associated with an O-type protostar in G26.50+0.28

Protostellar jets and outflows are essential ingredients of the star formation process. A better understanding of this phenomenon is important in its own right as well as for many fundamental aspects of star formation. Jets and outflows associated with O-type protostars are rarely studied with observations reaching the close vicinity of the protostars. In this work, we report high-resolution ALMA and VLBA observations to reveal a clear and consistent picture of an outflow associated with an O-type protostar candidate in the G26.50+0.28 region. These observations reveal, for the first time, a collimated jet located in the middle of the outflow cavity. The jet is found to be perpendicular to an elongated disk/toroid and its velocity gradient. The collimated jet appears to show a small amplitude (α≈0°.06) counterclockwise precession, when looking along the blueshifted jet axis from the strongest continuum source MM1, with a precession length of 0.22 pc. The inclination of the jet is likely to be very low (≈8°), which makes it a promising target to study its transverse morphologies and kinematics. However, no clear evidence of jet rotation is found in the ALMA and VLBA observations. The three-dimensional velocities of the water maser spots appear to show the same absolute speed with respect to different opening angles, suggesting the jet winds may be launched in a relatively small region. This favors the X-wind model, that is, jets are launched in a small area near the inner disk edge.

Accretion Spin-up and a Strong Magnetic Field in the Slow-spinning Be X-Ray Binary MAXI J0655-013

We present Monitor of All-sky X-ray Image (MAXI) and Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the Be X-ray binary, MAXI J0655−013, in outburst. NuSTAR observed the source once early in the outburst, when spectral analysis yields a bolometric (0.1–100 keV), unabsorbed source luminosity of L bol = 5.6 × 1036 erg s−1, and a second time 54 days later, by which time the luminosity had dropped to L bol = 4 × 1034 erg s−1 after first undergoing a dramatic increase. Timing analysis of the NuSTAR data reveals a neutron star spin period of 1129.09 ± 0.04 s during the first observation, which decreased to 1085 ± 1 s by the time of the second observation, indicating spin-up due to accretion throughout the outburst. Furthermore, during the first NuSTAR observation, we observed quasi-periodic oscillations (QPOs) with centroid frequency ν 0 = 89 ± 1 mHz, which exhibited a second harmonic feature. By combining the MAXI and NuSTAR data with pulse period measurements reported by Fermi/GBM, we are able to show that apparent flaring behavior in the MAXI light curve is an artifact introduced by uneven sampling of the pulse profile, which has a large pulsed fraction. Finally, we estimate the magnetic field strength at the neutron star surface via three independent methods, invoking a tentative cyclotron resonance scattering feature at 44 keV, QPO production at the inner edge of the accretion disk, and spin-up via interaction of the neutron star magnetic field with accreting material. Each of these result in a significantly different value. We discuss the strengths and weaknesses of each method and infer that MAXI J0655−013 is likely to have a high surface magnetic field strength, B s > 1013 G.

Comparative Analysis of the Performance Characteristics of Butterfly and Pinch Valves

Valves are important components in controlling the amount of fluid going to devices. One of these types is the butterfly valve (BFV) that adjusts the amount of flow by rotating the valve disk by means of its shafts which is usually located in the middle of the flow. Despite its common usage in various applications, the BFV is known to cause a high-pressure drop. Conversely, the pinch valve is another type of flow control device that uses a pinching mechanism to open and close the inner tube by pinching at different degrees. The absence of flow-controlling mechanisms in the flow path, such as the valve disk and its shaft, contribute to the minimal pressure drop in pinch valves. The high-pressure drop in BFVs and the minimal pressure drop in pinch valve flow make it worthwhile to investigate and compare their flow at all opening positions of the two valves. Therefore, this work numerically explores the potential of using the pinch valve as an alternative to the BFV in terms of its ability to attain a lower pressure loss, hence better flow rate. The influence of various BFV parameters such as shaft diameter, valve thickness, and valve disk edge were examined. The performance characteristics of both valves were obtained using CFD models formed on the SolidWorks program. This CFD model solves the differential equations using the finite element method. Moreover, a mathematical model to determine the area of the pinch valve at various pinching degrees was developed and compared with the results obtained from other mathematical models and CFD. It was shown that using a flat 1 mm valve disk thickness with round edges resulted in a 7.5% increase in mass flow rate compared to standard BFVs. On the other hand, using the pinch valve resulted in over a 700% mass flow rate compared to the BFV at a 25% opening position and a 49% increase in flow rate at a 75% opening position. Thus, the pinch valve has the potential to replace the BFV due to its better flow characteristics in any application.

Halting migration in magnetospherically sculpted protoplanetary discs

ABSTRACT We present a physically motivated model for the manner in which a stellar magnetic field sculpts the inner edge of a protoplanetary disc, and examines the consequence for the migration and stopping of sub-Neptune and super-Earth planets. This model incorporates a transition zone exterior to the inner truncation of the disc, where the surface density profile is modified by the diffusion of the stellar magnetic field into the disc. This modification results in a migration trap at the outer edge of the transition zone. We performed simulations of single-planet migration, considering a range of stellar magnetic field strengths and magnetic diffusion profiles. Our simulations show a tight relationship between the final locations of planets and the total magnetic budget available for the disc from their host star. We found that a stellar magnetic field between 67 and 180 G and a power-law index between 3 and 2.75 can reasonably reproduce the location at which the observed occurrence rate of close-in super-Earth and sub-Neptune populations changes slope.

Macular Retinoschisis from Optic Disc without a Visible Optic Pit or Advanced Glaucomatous Cupping (No Optic Pit Retinoschisis [NOPIR

To review eyes with peripapillary and macular retinoschisis without a visible optic pit or advanced glaucomatous optic atrophy, or No Optic Pit Retinoschisis (NOPIR). Retrospective multicenter case series. The study included 11 eyes of 11 patients. Retrospective study of eyes with macular retinoschisis without a visible optic pit, advanced optic nerve head cupping, or macular leakage on fluorescein angiography. Visual acuity (VA), retinoschisis resolution, months to resolution, and recurrence of retinoschisis RESULTS: The mean age was 68.1 ± 17.6 years, mean intraocular pressure was 17.4 ± 3.8 mmHg, and the mean spherical equivalent refractive error was-3.1 ± 2.9 diopters. No subject had pathologic myopia. Seven subjects were treated for glaucoma, and 9 subjects had nerve fiber layer defects on OCT. All eyes had retinoschisis in the outer nuclear layer (ONL) in the nasal macula and extending to the edge of the optic disc, and 8 subjects had fovea-involving retinoschisis. Three nonfoveal and 4 fovea-involved eyes were observed, and 4 fovea-involved eyes with vision loss underwent surgery. Surgery involved preoperative juxtapapillary laser followed by vitrectomy and membrane and internal limiting membrane peeling with intraocular gas and face-down position. The mean baseline VA was significantly worse in the surgery group than that in the observation group (P= 0.020). Retinoschisis resolved and vision improved in all surgical cases. The mean resolution time for the surgery group was 2.75 ± 0.96 months, which was shorter than that for the observation group (28.0 ± 21.2 months; P= 0.014). No eye developed recurrence of the retinoschisis after surgery. Peripapillary and macular retinoschisis can develop in eyes without a visible optic pit or advanced glaucomatous cupping. Eyes without foveal involvement and those with foveal involvement but only mild decrease in vision can be observed for spontaneous resolution. If there is persistent foveal involvement with vision loss, surgery can improve vision by resolving the macular retinoschisis. Surgery for fovea-involved macular retinoschisis without a visible optic pit resulted in faster anatomic resolution and better vision recovery. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

The GRAVITY young stellar object survey

Context. T Tauri stars are known to be the cradle of planet formation. Most exoplanets discovered to date lie at the very inner part of the circumstellar disk (<1 au). The innermost scale of young stellar objects is therefore a compelling region to be addressed, and long-baseline interferometry is a key technique to unveil their mysteries. Aims. We aim to spatially and spectrally resolve the innermost scale (≤1 au) of the young stellar system CI Tau to constrain the inner disk properties and better understand the magnetospheric accretion phenomenon. Methods. The high sensitivity offered by the combination of the four 8-m class telescopes of the Very Large Telescope Interferometer (VLTI) allied with the high spectral resolution (R ~ 4000) of the K-band beam combiner GRAVITY offers a unique capability to probe the sub-au scale of the CI Tau system, tracing both dust (continuum) and gas (Brγ line) emission regions. We developed a physically motivated geometrical model to fit the interferometric observables – visibilities and closure phases (CP) – and constrained the physical properties of the inner dusty disk. The continuum-corrected pure line visibilities have been used to estimate the size of the Hydrogen I Brγ emitting region. Results. From the K-band continuum study, we report a highly inclined (i ~ 70°) resolved inner dusty disk, with an inner edge located at a distance of 21 ± 2 R★ from the central star, which is significantly larger than the dust sublimation radius (Rsub = 4.3 to 8.6 R★). The inner disk appears misaligned compared to the outer disk observed by ALMA and the non-zero closure phase indicates the presence of an asymmetry that could be reproduced with an azimuthally modulated ring with a brighter south-west side. From the differential visibilities across the Brγ line, we resolved the line-emitting region, and measured a size of 4.8- 1.0+ 0.8 R★. Conclusions. The extended inner disk edge compared to the dust sublimation radius is consistent with the claim of an inner planet, CI Tau b, orbiting close in. The inner-outer disk misalignment may be induced by gravitational torques or magnetic warping. The size of the Brγ emitting region is consistent with the magnetospheric accretion process. Assuming it corresponds to the magnetospheric radius, it is significantly smaller than the co-rotation radius (Rcor= 8.8 ± 1.3 R★), which suggests an unstable accretion regime that is consistent with CI Tau being a burster.

New Strategy on Power Absorption of a Concentric Two-Body Wave Energy Converter

The wave energy converter (WEC) system, which extracts electricity through the relative heave motion of two concentric cylinders, comprises an inner cylinder and a torus-type outer cylinder sliding along the inner cylinder. To maximize the relative heave motion between two cylinders, the natural frequencies of the two cylinders must be precisely tuned to resonate and be situated on each side of the peak frequency of the wave spectrum. However, the demerit of this strategy is that it demands a deep draft of each cylinder for tuning, and a large-scale PTO damping device is necessary for mechanical power amplified by resonance. As an alternative to efficient and stable WECs, we adopt a new strategy in which the outer cylinder follows the incoming waves and the motion of the inner one is restricted to be minimal using a heave disk. The viscous damping due to formation of vortices at the disk edge is realized by the drag force in the Morison equation. The developed hydrodynamic model of two-body WEC based on a matched eigenfunction expansion method (MEEM) is applied to irregular waves characterized by significant wave height and peak period. It is found that the present two-body WEC with heave disk produces wave energy stably across a wide range of wave frequencies compared to the previous two-body WECs using resonance.

Accurate C/D ratio estimation with elliptical fitting for OCT image based on joint segmentation and detection network

Proper estimation of the cup-to-disc ratio (C/D ratio) plays a significant role in ophthalmic examinations, and it is urgent to improve the efficiency of C/D ratio automatic measurement. Therefore, we propose a new method for measuring the C/D ratio of OCTs in normal subjects. Firstly, the end-to-end deep convolution network is used to segment and detect the inner limiting membrane (ILM) and the two Bruch's membrane opening (BMO) terminations. Then, we introduce an ellipse fitting technique to post-process the edge of the optic disc. Finally, the proposed method is evaluated on 41 normal subjects using the optic-disc-area scanning mode of three machines: BV1000, Topcon 3D OCT-1, and Nidek ARK-1. In addition, pairwise correlation analyses are carried out to compare the C/D ratio measurement method of BV1000 to existing commercial OCT machines as well as other state-of-the-art methods. The correlation coefficient between the C/D ratio calculated by BV1000 and the C/D ratio calculated by manual annotation is 0.84, which indicates that the proposed method has a strong correlation with the results of manual annotation by ophthalmologists. Moreover, in comparison between BV1000, Topcon and Nidek in practical screening among normal subjects, the proportion of the C/D ratio less than 0.6 calculated by BV1000 accounts for 96.34%, which is the closest to the clinical statistics among the three OCT machines. The above experimental results and analysis show that the proposed method performs well in cup and disc detection and C/D ratio measurement, and compared with the existing commercial OCT equipment, the C/D ratio measurement results are relatively close to reality, which has certain clinical application value.

NGTS clusters survey – IV. Search for Dipper stars in the Orion Nebular Cluster

ABSTRACTThe dipper is a novel class of young stellar object associated with large drops in flux on the order of 10–50 per cent lasting for hours to days. Too significant to arise from intrinsic stellar variability, these flux drops are currently attributed to disc warps, accretion streams, and/or transiting circumstellar dust. Dippers have been previously studied in young star-forming regions, including the Orion Complex. Using Next Generation Transit Survey (NGTS) data, we identified variable stars from their light curves. We then applied a machine learning random forest classifier for the identification of new dipper stars in Orion using previous variable classifications as a training set. We discover 120 new dippers, of which 83 are known members of the Complex. We also investigated the occurrence rate of discs in our targets, again using a machine learning approach. We find that all dippers have discs, and most of these are full discs. We use dipper periodicity and model-derived stellar masses to identify the orbital distance to the inner disc edge for dipper objects, confirming that dipper stars exhibit strongly extended sublimation radii, adding weight to arguments that the inner disc edge is further out than predicted by simple models. Finally, we determine a dipper fraction (the fraction of stars with discs which are dippers) for known members of 27.8 ± 2.9 per cent. Our findings represent the largest population of dippers identified in a single cluster to date.

Anterior Column Realignment Using an Anterior-To-Psoas Approach: A Radiographic-Anatomic Feasibility Study at L1-L5.

Cross-sectional radioanatomic study. To determine the feasibility of performing an anterior column realignment (ACR) using an anterior-to-psoas (ATP) approach at L1-L5. Axial magnetic resonance images (MRI) of the L1-L5 disc levels obtained at a single institution were obtained and analyzed. The feasibility of performing an ACR was assessed using a combination of the size of the left oblique corridor (OC), the psoas morphology using the modified Moro classification, and the anterior disc edge to great vessel distance. Three hundred MRI studies obtained from 300 patients were included. All patients had a measurable left OC at the L1-L4 levels. Twenty patients (6.7%) had no measurable OC at the L4-L5 level. According to the modified Moro's classification, a high-rising psoas was seen in 4 patients (1.3%) at the L3-L4 level and 57 patients (19.0%) at the L4-L5 level. An ALL release was considered high risk due to no measurable space between the anterior disc edge and the great vessels in 54 patients (18.0%) at the L1-L2 level, 39 patients (13.0%) at the L2-L3 level, 119 patients (39.7%) at the L3-L4 level, and 226 patients (75.3%) at the L4-L5 level. ACR using an ATP approach is the most radioanatomically feasible at L2-L3. The L4-L5 level has the highest risk with regards to both the ATP approach and the ALL release for an ACR due to high rates of unmeasurable left OC and space between the anterior disc edge and the great vessels.

New insights on the near-infrared veiling of young stars using CFHT/SPIRou data

Context. Veiling is ubiquitous at different wavelength ranges in classical T Tauri stars. However, the origin of the veiling in the infrared (IR) domain is not well understood at present. The accretion spot alone is not enough to explain the shallow photospheric IR lines in accreting systems, suggesting that another source is contributing to the veiling in the near-infrared (NIR). The inner disk is often quoted as the additional emitting source meant to explain the IR veiling. Aims. In this work, we aim to measure and discuss the NIR veiling to understand its origins and variability timescale. Methods. We used a sample of 14 accreting stars observed with the CFHT/SPIRou spectrograph, within the framework of the SPIRou Legacy Survey, to measure the NIR veiling along the YJHK bands. We compared the veiling measurements with accretion and inner disk diagnostics. We also analyzed circumstellar emission lines and photometric observations from the literature. Results. The measured veiling grows from the Y to the K band for most of the targets in our sample. The IR veiling agrees with NIR emission excess obtained using photometric data. However, we also find a linear correlation between the veiling and the accretion properties of the system, showing that accretion contributes to the inner disk heating and, consequently, to the inner disk emission excess. We also show a connection between the NIR veiling and the system’s inclination with respect to our line of sight. This is probably due to the reduction of the visible part of the inner disk edge, where the NIR emission excess is expected to arise, as the inclination of the system increases. Our search for periods on the veiling variability showed that the IR veiling is not clearly periodic in the typical timescale of stellar rotation – which, again, is broadly consistent with the idea that the veiling comes from the inner disk region. The NIR veiling appears variable on a timescale of a day, showing the night-by-night dynamics of the optical veiling variability. In the long term, the mean NIR veiling seems to be stable for most of the targets on timescales of a month to a few years. However, during occasional episodes of high accretion in classical T Tauri stars, which affect the system’s dynamic, the veiling also seems to be much more prominent at such times, as we found in the case of the target RU Lup. Conclusions. We provide further evidence that for most targets in our sample, the veiling that mainly occurs in the JHK bands arises from dust in the inner disk.

V4142 Sgr: Double periodic variable with an accretor surrounded by the accretion disk’s atmosphere

Context.A detailed study of the close interacting binary V4142 Sgr, based on photometric and spectroscopic analyses, indicates that this system belongs to the enigmatic class of Algol-like variables exhibiting a long photometric cycle of an unknown nature.Aims.By performing photometric data-mining and spectroscopic observations covering the orbital cycle, we obtained the orbital parameters and the stellar properties of the binary system, along with the physical properties of the accretion disk located around the hot star. In addition, we gained insights into the evolutive path of the system.Methods.We modeled the light curve through an inverse method, using a theoretical light curve of the binary system that considers the light curve contribution of both stars and the accretion disk of the hot star to obtain the fundamental parameters. To constrain the main stellar parameters, the mass ratio was fixed in addition to the donor temperature, using the obtained values from our spectroscopic analysis, which includes deblending methods to isolate the spectral lines of the stellar components. The system parameters were compared with a grid of binary star evolutive models in order to gain insights into the evolutionary history of the system.Results.The orbital period and the long cycle were re-calculated, with the following result: 30d​​.633 ± 0d​​.002 and 1201 ± 14 days. The spectral analysis reveals Hαdouble emission with a persistentV ≤ Rasymmetry, which is considered evidence of a possible wind emerging from the hotspot region. In addition, a cold and evolved donor star ofMd = 1.11 ± 0.2 M⊙,Td = 4500 ± 125 K and aRd = 19.4 ± 0.2 R⊙as well as a rejuvenated B-dwarf companion ofMg = 3.86 ± 0.3 M⊙,Tg = 14 380 ± 700 K, andRg = 6.35 ± 0.2 R⊙were found. The gainer is surrounded by a concave and geometrically thick disk, creating its own atmosphere around the main component of a radial extension, ℛd= 22.8 ± 0.3R⊙, contributing ∼1.4 percent of the total luminosity of the system at theV-band at orbital phase 0.25. The disk is characterized by a hot-spot roughly placed where the stream hits the disk and an additional bright-spot separated 102.​​° 5 ± 0.​​° 04 degrees along the disk edge rim in the direction of the orbital motion. The system is seen under an inclination of 81.​​° 5 ± 0.​​° 3 and at a distance ofdGaia = 1140 ± 35 pc. Doppler maps of the emission lines reveal sites of enhanced line emission in the second and third velocity quadrants. The former would correspond to a hotspot and the latter to a bright spot detected by the light curve analysis. We find that the system comes from an initially shorter orbital period binary that inverted its mass ratio due to mass exchange. A plausible model scenario indicates that, at present, the K-type giant should have been depleted of hydrogen in its core, while the companion would have gained about 2M⊙through a process lasting about 2 Myr.

Flow characteristics of a centrifugal fan with optimized edge curvatures of an impeller front disk

In this study, the flow characteristics of different radiated impeller front disk fans were investigated by computational fluid dynamics to explore the effect of the radiated impeller front disk of the centrifugal fan on the three-dimensional flow of the volute-free centrifugal fan. Specifically, the flow-static pressure performance curve of the prototype fan was obtained to compare the numerical simulation results with the experimental results, so as to verify the accuracy of the numerical simulation. Besides, the linear fitting function of the radian edge of the front disk of the impeller was adjusted to acquire improved optimized fans. After numerical simulation analysis, the modification increases the outlet flow, static pressure at the outlet of the fan, static pressure efficiency, and total efficiency by 19 m³/h, 4.7 Pa, 5.6%, and 6.8%, respectively. The research reveals that the curvature of the front disk edge of the impeller can increase the flow channel volume between the blades and reduce the energy loss generated inside the impeller, thereby improving the static pressure and efficiency of the fan.

Testing relativistic accretion disk models with GRO J1655‐40

AbstractBlack hole X‐ray binaries are ideal environments to test the accretion phenomena in the presence of strong gravitational potentials. KERRBB held an important place in the X‐ray spectral continuum method for measuring the black hole spin modeling the emission from the innermost regions of the accretion disk. In this work, we present the results of X‐ray spectral analysis using publicly available RXTE data of GRO J1655‐40 obtained during the 2005 outburst with the two relativistic accretion disk models, KERRBB and KYNBB. Our analysis showed that both models provide identical results with black hole spin measurements, disk temperature, and disk luminosity when the inner edge of the accretion disk is set at the innermost stable circular orbit (ISCO) for the same accretion rates. We could not obtain reasonable fits for ∼89% of the observations with a fixed black hole spin value at a* = 0.7 using both models. Allowing the spin parameter to vary improved the fit statistic significantly with reduced χ2 values being reduced from ∼10 to 100 to below 2. Both models revealed black hole spin values varying between 0.52 < a* < 0.94, which can be interpreted as a variable inner edge of the disk throughout different accretion states.

On the origin of the lump in circumbinary discs

ABSTRACT Accreting binary black holes (BBHs) are multimessenger sources, emitting copious electromagnetic (EM) and gravitational waves. One of their most promising EM signatures is the light-curve modulation caused by a strong unique and extended azimuthal overdensity structure orbiting at the inner edge of the circumbinary disc (CBD), dubbed ‘lump’. In this paper, we investigate the origin of this structure using 2D general-relativistic (GR) hydrodynamical simulations of a CBD in an approximate BBH space–time. First, we use the symmetric mass-ratio case to study the transition from the natural m = 2 mode to m = 1. The asymmetry with respect to m = 2 grows exponentially, pointing to an instability origin. We indeed find that the CBD edge is prone to a (magneto)hydrodynamical instability owing to the disc edge density sharpness: the Rossby Wave Instability (RWI). The RWI criterion is naturally fulfilled at the CBD edge and we report the presence of vortices, which are typical structures of the RWI. The RWI is also at work in the asymmetric mass-ratio cases (from 0.1 to 0.5). However, the CBD edge sharpness decreases with a decreasing mass ratio, and so the lump. By proposing a scenario for this lump formation, our work further supports its existence in astrophysical CBDs and potential source for an EM signature of BBHs. Finally, because the RWI is not caused by GR effects, it is also a robust candidate for the lump origin in CBDs around non-compact objects, e.g. binary protostars.

The trophoblast giant cells of cricetid rodents.

Giant cells are a prominent feature of placentation in cricetid rodents. Once thought to be maternal in origin, they are now known to be trophoblast giant cells (TGCs). The large size of cricetid TGCs and their nuclei reflects a high degree of polyploidy. While some TGCs are found at fixed locations, others migrate throughout the placenta and deep into the uterus where they sometimes survive postpartum. Herein, we review the distribution of TGCs in the placenta of cricetids, including our own data from the New World subfamily Sigmodontinae, and attempt a comparison between the TGCs of cricetid and murid rodents. In both families, parietal TGCs are found in the parietal yolk sac and as a layer between the junctional zone and decidua. In cricetids alone, large numbers of TGCs, likely from the same lineage, accumulate at the edge of the placental disk. Common to murids and cricetids is a haemotrichorial placental barrier where the maternal-facing layer consists of cytotrophoblasts characterized as sinusoidal TGCs. The maternal channels of the labyrinth are supplied by trophoblast-lined canals. Whereas in the mouse these are lined largely by canal TGCs, in cricetids canal TGCs are interspersed with syncytiotrophoblast. Transformation of the uterine spiral arteries occurs in both murids and cricetids and spiral artery TGCs line segments of the arteries that have lost their endothelium and smooth muscle. Since polyploidization of TGCs can amplify selective genomic regions required for specific functions, we argue that the TGCs of cricetids deserve further study and suggest avenues for future research.

TOI-1136 is a Young, Coplanar, Aligned Planetary System in a Pristine Resonant Chain

Convergent disk migration has long been suspected to be responsible for forming planetary systems with a chain of mean-motion resonances (MMRs). Dynamical evolution over time could disrupt the delicate resonant configuration. We present TOI-1136, a 700 ± 150 Myr old G star hosting at least six transiting planets between ∼2 and 5 R ⊕. The orbital period ratios deviate from exact commensurability by only 10−4, smaller than the ∼10−2 deviations seen in typical Kepler near-resonant systems. A transit-timing analysis measured the masses of the planets (3–8M ⊕) and demonstrated that the planets in TOI-1136 are in true resonances with librating resonant angles. Based on a Rossiter–McLaughlin measurement of planet d, the star’s rotation appears to be aligned with the planetary orbital planes. The well-aligned planetary system and the lack of a detected binary companion together suggest that TOI-1136's resonant chain formed in an isolated, quiescent disk with no stellar flyby, disk warp, or significant axial asymmetry. With period ratios near 3:2, 2:1, 3:2, 7:5, and 3:2, TOI-1136 is the first known resonant chain involving a second-order MMR (7:5) between two first-order MMRs. The formation of the delicate 7:5 resonance places strong constraints on the system’s migration history. Short-scale (starting from ∼0.1 au) Type-I migration with an inner disk edge is most consistent with the formation of TOI-1136. A low disk surface density (Σ1 au ≲ 103g cm−2; lower than the minimum-mass solar nebula) and the resultant slower migration rate likely facilitated the formation of the 7:5 second-order MMR.

Универсальный пневматический высевающий аппарат

Designing a seeding unit for the combined sowing of grain crops is a relevant and promising area of the development of sowing equipment. For this purpose, the authors designed a universal pneumatic vacuum-type seeding unit capable of sowing seeds of two crops simultaneously by dotted, combined, and nested methods and providing different sowing rates. Openings of the sowing polymer disc are equipped with built-in metal bushings, located at a 20-mm offset from the disc edge. The polymer material was chosen based on greater efficiency compared to a metal disc: longer life, moisture resistance, lower damage to seeds. The developed sowing disc is equipped with round magnetic pads with a diameter larger than the hole diameter, the ratio between the sowing disc diameter and the hole is 1:20; the ratio between the thickness of the magnetic pad and that of the sowing disc is 1:3. Magnetic pads may have up to four holes with a diameter of 1.5 to 2 mm. Due to this feature the sowing device can sow seeds according to different patterns. When sowing seeds in the dotted method, seeds of one crop are fed into a half-part of the sowing unit hopper, a coulter with one slide is installed and a one-hole disc with a magnetic pad is used. The use of a blind magnetic pad makes it possible to change the distance between seeds in the row.

The unaltered pulsar: GRO J1750-27, a supercritical X-ray neutron star that does not blink an eye

When accreting X-ray pulsars (XRPs) undergo bright X-ray outbursts, their luminosity-dependent spectral and timing features can be analyzed in detail. The XRP GRO J1750-27 recently underwent one such episode, during which it was observed withNuSTARand monitored with NICER. Such a data set is rarely available, as it samples the outburst over more than 1 month at a luminosity that is always exceeding ∼5 × 1037 erg s−1. This value is larger than the typical critical luminosity value, where a radiative shock is formed above the surface of the neutron star. Our data analysis of the joint spectra returns a highly (NH ∼ (5 − 8) × 1022 cm−2) absorbed spectrum showing a Kαiron line, a soft blackbody component likely originating from the inner edge of the accretion disk, and confirms the discovery of one of the deepest cyclotron lines ever observed, at a centroid energy of ∼44 keV corresponding to a magnetic field strength of 4.7 × 1012 G. This value is independently supported by the best-fit physical model for spectral formation in accreting XRPs which, in agreement with recent findings, favors a distance of 14 kpc and also reflects a bulk-Comptonization-dominated accretion flow. Contrary to theoretical expectations and observational evidence from other similar sources, the pulse profiles as observed by NICER remain remarkably steady through the outburst rise, peak and decay. The NICER spectrum, including the iron Kαline best-fit parameters, also remain almost unchanged at all probed outburst stages, similar to the pulsed fraction behavior. We argue that all these phenomena are linked and interpret them as resulting from a saturation effect of the emission from the accretion column, which occurs in the high-luminosity regime.

On-chip ultraviolet second-harmonic generation in lithium-tantalate thin film microdisk

The compact and reliable ultraviolet (UV) source has attracted remarkable attention for its potential use in optical measurement systems, high-density optical storage, and biomedical applications. We demonstrate ultraviolet generation by frequency doubling in a lithium-tantalate-on-insulator (LTOI) microdisk via modal phase matching. The 50-µm-diameter microdisk was milled by a focused ion beam (FIB) and followed by chemo-mechanical polishing (CMP) to smooth the disk surface and edge, and the Q-factor reaches 2.74×105 in the visible band. On-chip UV coherent light with a wavelength of 384.3 nm was achieved, which shows great promise for using LTOIs in integrated ultraviolet source platforms.