We have measured the orbital parameters of seven close binaries, including six new objects, in a radial velocity survey of 38 objects comprising a hot subdwarf star with orbital periods ranging from ...∼0.17 to 3 d. One new system, GALEX J2205−3141, shows reflection on an M dwarf companion. Three other objects show significant short-period variations, but their orbital parameters could not be constrained. Two systems comprising a hot subdwarf paired with a bright main-sequence/giant companion display short-period photometric variations possibly due to irradiation or stellar activity and are also short-period candidates. All except two candidates were drawn from a selection of subluminous stars in the Galaxy Evolution Explorer ultraviolet sky survey. Our new identifications also include a low-mass subdwarf B star and likely progenitor of a low-mass white dwarf (GALEX J0805−1058) paired with an unseen, possibly substellar, companion. The mass functions of the newly identified binaries imply minimum secondary masses ranging from 0.03 to 0.39 M⊙. Photometric time series suggest that, apart from GALEX J0805−1058 and J2205−3141, the companions are most likely white dwarfs. We update the binary population statistics: close to 40 per cent of hot subdwarfs have a companion. Also, we found that the secondary mass distribution shows a low-mass peak attributed to late-type dwarfs, and a higher mass peak and tail distribution attributed to white dwarfs and a few spectroscopic composites. Also, we found that the population kinematics imply an old age and include a few likely halo population members.
The fit note replaced the sick note in 2010. The statement of fitness for work (fit note) is expected to benefit the British economy by helping more people stay in work and prevent long-term sickness ...absence. Understanding and responding to employers' views on the fit note is key, in order for this goal to be achieved.
To explore employers' views on the fit note.
A qualitative study was undertaken and face-to-face interviews were conducted with participants representing employers from a variety of industries.
There were 21 participants who were mainly human resources officers and line managers. Employers welcomed the introduction of the fit note and felt that it was an improvement on the sick note. The majority of employers felt the fit note had the potential to promote an earlier return to work, if used properly. The main problems reported were the completion of the fit notes and quality of advice received from general practitioners. Employers felt that the most helpful advice came from fit notes with information on the functional effects of the medical condition. Some employers found return to work decisions problematic.
The fit note has the potential to promote an earlier return to work. In order for the fit note to achieve its aim, further understanding of the difficulties employers are having when making return to work decisions is important, in order to develop guidance to enable them to provide the practical support employees need to return to work sooner.
We report on a detailed optical spectroscopic follow-up of the black hole (BH) transient MAXI J1820+070 (ASASSN-18ey). The observations cover the main part of the X-ray binary outburst, when the ...source alternated between hard and soft states following the classical pattern widely seen in other systems. We focus the analysis on the He i emission lines at 5876 and 6678 , as well as on H . We detect clear accretion disk wind features (P-Cyg profiles and broad emission line wings) in the hard state, both during outburst rise and decay. These are not witnessed during the several months long soft state. However, our data suggest that the visibility of the outflow might be significantly affected by the ionization state of the accretion disk. The terminal velocity of the wind is above ∼1200 km s−1, which is similar to outflow velocities derived from (hard-state) optical winds and (soft-state) X-ray winds in other systems. The wind signatures, in particular the P-Cyg profiles, are very shallow, and their detection has only been possible thanks to a combination of source brightness and intense monitoring at very high signal-to-noise. This study indicates that cold, optical winds are most likely a common feature of BH accretion, and therefore, that wind-like outflows are a general mechanism of mass and angular momentum removal operating throughout the entire X-ray binary outburst.
ABSTRACT
X-ray transients, such as accreting neutron stars, periodically undergo outbursts, thought to be caused by a thermal-viscous instability in the accretion disc. Usually outbursts of accreting ...neutron stars are identified when the accretion disc has undergone an instability, and the persistent X-ray flux has risen to a threshold detectable by all sky monitors on X-ray space observatories. Here, we present the earliest known combined optical, UV, and X-ray monitoring observations of the outburst onset of an accreting neutron star low-mass X-ray binary (LMXB) system. We observed a significant, continuing increase in the optical i′-band magnitude starting on July 25, 12 d before the first X-ray detection with Swift/XRT and NICER (August 6), during the onset of the 2019 outburst of SAX J1808.4−3658. We also observed a 4 d optical to X-ray rise delay, and a 2 d UV to X-ray delay, at the onset of the outburst. We present the multiwavelength observations that were obtained, discussing the theory of outbursts in X-ray transients, including the disc instability model, and the implications of the delay. This work is an important confirmation of the delay in optical to X-ray emission during the onset of outbursts in LMXBs, which has only previously been measured with less sensitive all sky monitors. We find observational evidence that the outburst is triggered by ionization of hydrogen in the disc.
Context. Doppler tomography is a technique that has revolutionised the interpretation of the phase-resolved spectroscopic observations of interacting binary systems. Aims. We present the results of ...our investigation of reversing the velocity axis to create an inside-out Doppler coordinate framework with the intent to expose overly compacted and enhance washed out emission details in the standard Doppler framework. Methods. The inside-out tomogram is constructed independently of the standard tomogram by directly projecting phase-resolved spectra onto an inside-out velocity coordinate frame. For the inside-out framework, the zero-velocity origin is transposed to the outer circumference and the maximum velocities to the origin of the velocity space. We test the technique on a simulated system and two real systems with easily identifiable features, namely the accretion disc and bright spot in WZ Sge, and spiral shocks in IP Peg. Results. Our tests show that there is a redistribution of the relative brightness of emission components throughout the tomograms, i.e., where the standard framework tends to concentrate and enhance lower velocity features towards the origin, the inside-out velocity framework tends to concentrate and enhance higher velocity features towards the origin. Conversely, the standard framework disperses and smears the higher velocities farther away from the origin whereas the inside-out framework disperses and smears the lower velocities. In addition, the projection of the accretion disc in velocity space now appears correctly orientated with the inner edge close to the maximum velocity origin and its outer edge closer to the zero-velocity outer circumference. Furthermore, the gas stream and secondary star are projected on the outside of the disc with the bright spot of the stream-disc impact region on the disc’s outer edge in the inside-out velocity space. Conclusions. We conclude that inside-out Doppler tomography complements the already powerful tomographic techniques in the analysis of spectroscopic emissions from interacting binary systems.
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Context. Doppler tomography of magnetic cataclysmic variables is a valuable tool for the interpretation of the complex spectroscopic emission line profiles observed for these systems. Aims. We ...present the results of applying our inside-out velocity projection and flux modulation mapping techniques to the Doppler tomography of magnetic cataclysmic variables. Methods. The inside-out projection reverses the standard velocity direction by transposing the zero-velocity origin to the outer circumference and the maximum velocities to the origin of the velocity space. The inside-out tomogram is constructed by directly projecting phase-resolved spectra onto the inside-out framework. In addition, our flux modulation mapping technique extracts any information related to the modulation of the line flux by utilising consecutive half-phase tomograms. We apply this to both the standard and the inside-out techniques. Results. Our test cases, the polars HU Aqr and V834 Cen, and the intermediate polar PQ Gem, were chosen because of their known accretion characteristics, namely ballistic, magnetic and curtain dominated accretion, respectively. In all three cases the inside-out tomogram better exposes low-velocity emission details which are overly compacted in the standard tomogram. This is especially apparent for the mid-inclination V834 Cen where the almost blob-like blended lower velocity emission in the standard tomogram is more exposed in the inside-out tomogram, making it easier to distinguish between the ballistic and magnetically confined accretion flows that are evident in the trailed spectra. Similarly, the inside-out tomogram enhances high velocity emission details which are washed out in the standard tomogram. This is particularly effective in revealing the high velocity magnetic accretion flows in the polars HU Aqr and V834 Cen. The addition of our flux modulation technique gives a significant improvement in reproducing the trailed input spectra adding more confidence to the interpretation of the Doppler maps. Furthermore, amplitude and phase maps are constructed that further reveal amplitude and phasing characteristics of the emission components in the three test cases.
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ABSTRACT
We report the discovery of the first transient with MeerKAT, MKT J170456.2–482100, discovered in ThunderKAT images of the low-mass X-ray binary GX339–4. MKT J170456.2–482100 is variable in ...the radio, reaching a maximum flux density of $0.71\pm 0.11\, \mathrm{mJy}$ on 2019 October 12, and is undetected in 15 out of 48 ThunderKAT epochs. MKT J170456.2–482100 is coincident with the chromospherically active K-type sub-giant TYC 8332-2529-1, and $\sim 18\, \mathrm{yr}$ of archival optical photometry of the star shows that it varies with a period of $21.25\pm 0.04\, \mathrm{d}$. The shape and phase of the optical light curve changes over time, and we detect both X-ray and UV emission at the position of MKT J170456.2–482100, which may indicate that TYC 8332-2529-1 has large star spots. Spectroscopic analysis shows that TYC 8332-2529-1 is in a binary, and has a line-of-sight radial velocity amplitude of $43\, \mathrm{km\, s^{-1}}$. We also observe a spectral feature in antiphase with the K-type sub-giant, with a line-of-sight radial velocity amplitude of $\sim 12\pm 10\, \mathrm{km\, s^{-1}}$, whose origins cannot currently be explained. Further observations and investigation are required to determine the nature of the MKT J170456.2–482100 system.
We present 33 new mid-eclipse times spanning approximately eight years of the eclipsing polar UZ Fornacis. We have used our new observations to test the two-planet model previously proposed to ...explain the variations in its eclipse times measured over the past ~35 yr. We find that the proposed model does indeed follow the general trend of the new eclipse times, however, there are significant departures. In order to accommodate the new eclipse times, the two-planet model requires that one or both of the planets require highly eccentric orbits, that is, e ≥ 0.4. Such multiple planet orbits are considered to be unstable. Whilst our new observations are consistent with two cyclic variations as previously predicted, significant residuals remain. We conclude that either additional cyclic terms, possibly associated with more planets, or other mechanisms, such as the Applegate mechanism are contributing to the eclipse time variations. Further long-term monitoring is required.
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Scandium is an important industrial metal for which demand is projected to increase in the future. Although many Sc deposits are secondary, Sc is scavenged by clinopyroxene during fractional ...crystallization of primary, mafic-ultramafic magmas. Sc may thus occur in sub-economic concentrations in mafic-ultramafic intrusions. In this work, we present new data on the concentration of Sc in the Bushveld Complex (BC) of South Africa. The eastern and western limbs of the BC are considered to be largely pristine, primary magmatic deposits, whereas the northern limb shows evidence of large-scale, localized crustal contamination. Samples from the primary magmatic cumulates of the eastern limb, from the mineralized Flatreef of the northern limb, and from the crustal-contaminated Footwall Assimilation Zone (FAZ) of the Flatreef were analysed for Sc. Despite the FAZ containing abundant clinopyroxene, interpreted to have recrystallized from the original cumulates in the presence of melted sedimentary rocks, no significant differences are seen in the concentration of Sc compared to other cumulate rocks of the BC containing less-abundant clinopyroxene. The concentration of Sc in the analysed samples is mainly controlled by mineralogy, with anorthosites, chromitites, and harzburgites containing under 20 ppm, and norites and pyroxenites containing 20-40 ppm. The parapyroxenites of the FAZ are less enriched in Sc than expected, suggesting that Sc may have been lost during alteration and recrystallization.
ABSTRACT
We present phase-resolved spectroscopy, photometry, and circular spectropolarimetry of the eclipsing polar UZ Fornacis. Doppler tomography of the strongest emission lines using the ...inside-out projection revealed the presence of three emission regions: from the irradiated face of the secondary star, the ballistic stream and the threading region, and the magnetically confined accretion stream. The total intensity spectrum shows broad emission features and a continuum that rises in the blue. The circularly polarized spectrum shows the presence of three cyclotron emission harmonics at ∼4500, 6000, and 7700 Å, corresponding to harmonic numbers 4, 3, and 2, respectively. These features are dominant before the eclipse and disappear after the eclipse. The harmonics are consistent with a magnetic field strength of ∼57 MG. We also present phase-resolved circular and linear photopolarimetry to complement the spectropolarimetry around the times of eclipse. MeerKAT radio observations show a faint source that has a peak flux density of 30.7 ± 5.4 $\mu$Jy beam−1 at 1.28 GHz at the position of UZ For.
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