313 research outputs found
First measurement of the total gravitational quadrupole moment of a black widow companion
We present the first measurement of the gravitational quadrupole moment of the companion star of a spider pulsar, namely the black widow PSR J2051â0827. To this end, we have re-analysed radio timing data using a new model that is able to account for periastron precession caused by tidal and centrifugal deformations of the star as well as by general relativity. The model allows for a time-varying component of the quadrupole moment, thus self-consistently accounting for the ill-understood orbital period variations observed in these systems. Our analysis results in the first detection of orbital precession in a spider system at ÏË=â68â.6+0â.9â0â.5 yrâ1 and the most accurate determination of orbital eccentricity for PSR J2051â0827 with e = (4.2 ± 0.1) Ă 10â5. We show that the variable quadrupole component is about 100 times smaller than the average quadrupole moment QÂŻ=â2.2+0.6â1Ă1041 kgm2â . We discuss how accurate modelling of high-precision optical light curves of the companion star will allow its apsidal motion constant to be derived from our results
Optical, X-ray, and Îł-ray observations of the candidate transitional millisecond pulsar 4FGL J0427.8-6704
We present an optical, X-ray, and Îł-ray study of 1SXPS J042749.2-670434, an eclipsing X-ray binary that has an associated Îł-ray counterpart, 4FGL J0427.8-6704. This association has led to the source being classified as a transitional millisecond pulsar (tMSP) in an accreting state. We analyse 10.5 yr of Fermi LAT data and detect a Îł-ray eclipse at the same phase as optical and X-ray eclipses at the >5âÏ level, a significant improvement on the 2.8âÏ level of the previous detection. The confirmation of this eclipse solidifies the association between the X-ray source and the Îł-ray source, strengthening the tMSP classification. However, analysis of several optical data sets and an X-ray observation do not reveal a change in the sourceâs median brightness over long time-scales or a bi-modality on short time-scales. Instead, the light curve is dominated by flickering, which has a correlation time of 2.6 min alongside a potential quasi-periodic oscillation at âŒ21 min. The mass of the primary and secondary stars is constrained to be M1=1.43+0.33â0.19 Mâ and M2=0.3+0.17â0.12 Mâ through modelling of the optical light curve. While this is still consistent with a white dwarf primary, we favour the tMSP in a low accretion state classification due to the significance of the Îł-ray eclipse detection
The orbit and companion of PSR J1622-0315: variable asymmetry and a massive neutron star
The companion to PSR J1622-0315, one of the most compact known redback millisecond pulsars, shows extremely low irradiation despite its short orbital period. We model this system to determine the binary parameters, combining optical observations from the New Technology Telescope in 2017 and the Nordic Optical Telescope in 2022 with the binary modeling code ICARUS. We find a best-fit neutron star mass of 2.3 ± 0.4 Mâ, and a companion mass of 0.15 ± 0.02 Mâ. We detect for the first time low-level irradiation from asymmetry in the minima as well as a change in the asymmetry of the maxima of its light curves over five years. Using starspot models, we find better fits than those from symmetric direct heating models, with consistent orbital parameters. We discuss an alternative scenario where the changing asymmetry is produced by a variable intrabinary shock. In summary, we find that PSR J1622-0315 combines low irradiation with variable light-curve asymmetry and a relatively high neutron star mass
Mass estimates from optical modelling of the new TRAPUM redback PSR J1910â5320
Spider pulsars continue to provide promising candidates for neutron star mass measurements. Here we present the discovery of PSR J1910â5320, a new millisecond pulsar discovered in a MeerKAT observation of an unidentified Fermi-LAT gamma-ray source. This pulsar is coincident with a recently identified candidate redback binary, independently discovered through its periodic optical flux and radial velocity. New multicolour optical light curves obtained with ULTRACAM/New Technology Telescope in combination with MeerKAT timing and updated SOAR/Goodman spectroscopic radial velocity measurements allow a mass constraint for PSR J1910â5320. ICARUS optical light curve modelling, with streamlined radial velocity fitting, constrains the orbital inclination and companion velocity, unlocking the binary mass function given the precise radio ephemeris. Our modelling aims to unite the photometric and spectroscopic measurements available by fitting each simultaneously to the same underlying physical model, ensuring self-consistency. This targets centre-of-light radial velocity corrections necessitated by the irradiation endemic to spider systems. Depending on the gravity darkening prescription used, we find a moderate neutron star mass of either 1.6 ± 0.2 or 1.4 ± 0.2 Mâ. The companion mass of either 0.45 ± 0.04 or
Mâ also further confirms PSR J1910â5320 as an irradiated redback spider pulsar
A rapid optical and X-ray timing study of the neutron star X-ray binary Swift J1858.6â0814
We present a rapid timing analysis of optical (HiPERCAM and ULTRACAM) and X-ray (NICER) observations of the X-ray transient SwiftâJ1858.6â0814 during 2018 and 2019. The optical light curves show relatively slow, large amplitude (âŒ1âmag in gs) âblueâ flares (i.e. stronger at shorter wavelengths) on time-scales of âŒminutes as well as fast, small amplitude (âŒ0.1âmag in gs) âredâ flares (i.e. stronger at longer wavelengths) on time-scales of âŒseconds. The âblueâ and âredâ flares are consistent with X-ray reprocessing and optically thin synchrotron emission, respectively, similar to what is observed in other X-ray binaries. The simultaneous optical versus soft- and hard-band X-ray light curves show time- and energy-dependent correlations. The 2019 March 4 and parts of the June data show a nearly symmetric positive cross-correlations (CCFs) at positive lags consistent with simple X-ray disc reprocessing. The soft- and hard-band CCFs are similar and can be reproduced if disc reprocessing dominates in the optical and one component (disc or synchrotron Comptonization) dominates both the soft and hard X-rays. A part of the 2019 June data shows a very different CCFs. The observed positive correlation at negative lag in the soft band can be reproduced if the optical synchrotron emission is correlated with the hot flow X-ray emission. The observed timing properties are in qualitative agreement with the hybrid inner hot accretion flow model, where the relative role of the different X-ray and optical components that vary during the course of the outburst, as well as on shorter time-scales, govern the shape of the optical/X-ray CCFs
Measuring the mass of the black widow PSR J1555-2908
Accurate measurements of the masses of neutron stars are necessary to test
binary evolution models, and to constrain the neutron star equation of state.
In pulsar binaries with no measurable post-Keplerian parameters, this requires
an accurate estimate of the binary system's inclination and the radial velocity
of the companion star by other means than pulsar timing. In this paper, we
present the results of a new method for measuring this radial velocity using
the binary synthesis code Icarus. This method relies on constructing a model
spectrum of a tidally distorted, irradiated star as viewed for a given binary
configuration. This method is applied to optical spectra of the newly
discovered black widow PSR J1555-2908. By modelling the optical spectroscopy
alongside optical photometry, we find that the radial velocity of the companion
star is km s (errors quoted at 95\% confidence interval), as
well as a binary inclination of . Combined with -ray
pulsation timing information, this gives a neutron star mass of
1.67 M and a companion mass of
0.060 M, placing PSR J1555-2908 at the observed
upper limit of what is considered a black widow system.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Society. 15 pages, 7 Figures. Underlying data available at
https://zenodo.org/record/565306
Ammonite Faunal Dynamics Across Bio-Events During the Mid-and Late Cretaceous Along the Russian Pacific Coast
JagtâYazykova, E.A. 2012. Ammonite faunal dynamics across bioâevents during the mid â and Late Cretaceous along th
Optical photometry of two transitional millisecond pulsars in the radio pulsar state
We present ULTRACAM multiband optical photometry of two transitional millisecond pulsars (tMSPs), PSR J1023+0038 and PSR J1227â4853, taken while both were in their radio pulsar states. The light curves show significant asymmetry about the flux maxima in all observed bands, suggesting an asymmetric source of heating in the system. We model the light curves using the icarus binary code, using models with an additional âhotspotâ heating contribution and an anisotropic heat redistribution model to treat the asymmetry. Our modelling reveals companion stars with underfilled Roche lobes in both PSRs J1023+0038 and J1227â4853, with Roche lobe filling factors in the range f ⌠0.82â0.92. While the volume-averaged filling factors are closer to unity, significant underfilling is unexpected from tMSPs as they must rapidly overfill their Roche lobes to start transferring mass, which occurs on time-scale of weeks or months. We discuss the motivation and validity of our extensions to the models and the implications of the underfilled Roche lobe, and suggest future work to further investigate the role of the filling factor in the tMSP cycle
Evidence for a narrow dip structure at 1.9 GeV/c in diffractive photoproduction
A narrow dip structure has been observed at 1.9 GeV/c in a study of
diffractive photoproduction of the final state performed by the
Fermilab experiment E687.Comment: The data of Figure 6 can be obtained by downloading the raw data file
e687_6pi.txt. v5 (2nov2018): added Fig. 7, the 6 pion energy distribution as
requested by a reade
Customer emotions in service failure and recovery encounters
Emotions play a significant role in the workplace, and considerable attention has been given to the study of employee emotions. Customers also play a central function in organizations, but much less is known about customer emotions. This chapter reviews the growing literature on customer emotions in employeeâcustomer interfaces with a focus on service failure and recovery encounters, where emotions are heightened. It highlights emerging themes and key findings, addresses the measurement, modeling, and management of customer emotions, and identifies future research streams. Attention is given to emotional contagion, relationships between affective and cognitive processes, customer anger, customer rage, and individual differences
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