We present the first optical spectroscopy of five confirmed (or strong candidate) redback millisecond pulsar binaries, obtaining complete radial velocity curves for each companion star. The ...properties of these millisecond pulsar binaries with low-mass, hydrogen-rich companions are discussed in the context of the 14 confirmed and 10 candidate field redbacks. We find that the neutron stars in redbacks have a median mass of 1.78 0.09 M with a dispersion of = 0.21 0.09. Neutron stars with masses in excess of 2 M are consistent with, but not firmly demanded by, current observations. Redback companions have median masses of 0.36 0.04 M with a scatter of = 0.15 0.04 M , and a tail possibly extending up to 0.7-0.9 M . Candidate redbacks tend to have higher companion masses than confirmed redbacks, suggesting a possible selection bias against the detection of radio pulsations in these more massive candidate systems. The distribution of companion masses between redbacks and the less massive black widows continues to be strongly bimodal, which is an important constraint on evolutionary models for these systems. Among redbacks, the median efficiency of converting the pulsar spin-down energy to γ-ray luminosity is ∼10%.
Gold(iii) complexes are attractive candidates as phosphorescent dopants in organic light-emitting devices for high-luminance full-colour displays. However, no data on the stability of such devices ...have been reported to date. Through rational molecular design and synthesis, we have successfully generated a new class of cyclometalated gold(iii) C^C^N complexes with tunable emission colours spanning from sky-blue to red. These complexes exhibit high photoluminescence quantum yields of up to 80% in solid-state thin films, excellent solubility and high thermal stability. Solution-processable and vacuum-deposited organic light-emitting devices based on these complexes operate with external quantum efficiencies of up to 11.9% and 21.6%, respectively, and operational half-lifetimes of up to 83,000 h at 100 cd m−2.Cyclometalated gold(iii) complexes are shown to offer tunable emission colours spanning from sky-blue to red and enable the fabrication of phosphorescent organic light-emitting devices with high external quantum efficiency and long lifetimes.
Abstract
I report here a new result extracted from the Fermi Large Area Telescope observation of the classical nova ASASSN-16ma that exhibits coherent
γ
-ray pulsations at 544.84(7) s during its ...outburst in 2016. Considering the number of independent trials, the significance of the evidence is 4.0
σ
, equivalent to a false-alarm probability of 5.9 × 10
−5
. The periodicity was steady during the 4 days of its appearance, indicating its origin as the spinning signal of the white dwarf. Given that the optical and
γ
-ray light curves of some shock-powered
γ
-ray novae have been recently shown to be closely correlated to each other, the
γ
-ray pulsation phenomenon likely implies an existence of associated optical pulsations, which would provide detailed ephemerides for these extreme white dwarf binaries for further investigations in the near future.
ABSTRACT We report the discovery of an eclipsing low-mass X-ray binary at the center of the 3FGL error ellipse of the unassociated Fermi/Large Area Telescope γ-ray source 3FGL J0427.9-6704. ...Photometry from OGLE and the SMARTS 1.3 m telescope and spectroscopy from the SOAR telescope have allowed us to classify the system as an eclipsing low-mass X-ray binary (P = 8.8 hr) with a main-sequence donor and a neutron-star accretor. Broad double-peaked H and He emission lines suggest the ongoing presence of an accretion disk. Remarkably, the system shows separate sets of absorption lines associated with the accretion disk and the secondary, and we use their radial velocities to find evidence for a massive (∼1.8-1.9 M ) neutron-star primary. In addition to a total X-ray eclipse with a duration of ∼2200 s observed with NuSTAR, the X-ray light curve also shows properties similar to those observed among known transitional millisecond pulsars: short-term variability, a hard power-law spectrum ( ), and a comparable 0.5-10 keV luminosity ( erg s−1). We find tentative evidence for a partial ( ) γ-ray eclipse at the same phase as the X-ray eclipse, suggesting the γ-ray emission may not be confined to the immediate region of the compact object. The favorable inclination of this binary is promising for future efforts to determine the origin of γ-rays among accreting neutron stars.
Abstract
We have performed a systematic study of the rotational, orbital, and X-ray properties of millisecond pulsars (MSPs) in globular clusters (GCs) and compared their nature with those of the ...MSPs in the Galactic field (GF). We found that GC MSPs generally rotate slower than their counterparts in the GF. Different from the expectation of a simple recycling scenario, no evidence for the correlation between the orbital period and the rotation period can be found in the MSP binaries in GCs. There is also an indication that the surface magnetic field of GC MSPs is stronger than those in the GF. All these suggest dynamical interactions in GCs can alter the evolution of MSPs/their progenitors, which can leave an imprint on their X-ray emission properties. While the MSPs in both GF and GCs have similar distributions of X-ray luminosity and hardness, our sample supports the notion that these two populations follow different relations between the X-ray luminosity and spin-down power. We discuss this in terms of both the pulsar emission model and the observational bias.
Abstract
We report optical observations of the millisecond pulsar binary system PSR J1622–0315 with the Lulin 1 m telescope in Taiwan and the Lijiang 2.4 m telescope in China between 2019 and 2021. ...The companion of the pulsar, which is of
V
∼ 19 mag, showed ellipsoidal-distorted orbital variations in its light curves. The best-fit model to the light curves, with the binary code
PHOEBE
, gives a companion mass of 0.122 ± 0.006
M
⊙
. This places PSR J1622–0315 in the spider-system subclass. We compared the properties of PSR J1622–0315 with other spider pulsar binaries for the scalings between the spin-down luminosity derived for the pulsar, irradiation luminosity of the companion, and X-ray luminosity of the binary. We find that pulsar irradiation in PSR J1622–0315 is insignificant and the irradiation luminosity of the transitional millisecond pulsars PSR J1023+0038 and PSR J1227–4853 are the highest among the redback systems.
Abstract
The Dragonfly Nebula (G75.2+0.1) powered by the young pulsar J2021+3651 is a rare pulsar wind nebula (PWN) that shows double tori and polar jets enclosed by a bow-shock structure in X-rays. ...We present new radio observations of this source taken with the Very Large Array at 6 GHz. The radio PWN has an overall size about two times as large as the X-ray counterpart, consisting of a bright main-body region in the southwest, a narrow and fainter bridge region in the northeast, and a dark gap in between. The nebula shows a radio spectrum much softer than that of a typical PWN. This could be resulting from compression by the ram pressure as the system travels mildly supersonically in the interstellar medium. Our polarization maps reveal a highly ordered and complex
B
-field structure. This can be explained by a toroidal field distorted by the pulsar motion.
Abstract
Despite the 30 yr history of ultraluminous X-ray sources (ULXs) studies, issues such as the majority of their physical natures (i.e., neutron stars, stellar-mass black holes, or intermediate ...black holes) as well as the accretion mechanisms are still under debate. Expanding the ULX sample size in the literature is clearly a way to help. To this end, we investigated the X-ray source population, ULXs in particular, in the barred spiral galaxy NGC 1559 using a Chandra observation made in 2016. In this 45 ks exposure, 33 X-ray point sources were detected within the 2.′7 isophotal radius of the galaxy. Among them, eight ULXs were identified with the criterion of the X-ray luminosity
L
x
> 10
39
erg s
−1
(0.3–7 keV). Both X-ray light curves and spectra of all the sources were examined. Except for some low-count spectra that only provide ambiguous spectral fitting results, all the X-ray sources were basically spectrally hard and therefore likely have nonthermal origins. While no strong X-ray variability was present in most of the sources owing to the relatively short exposure of the observation, we found an intriguing ULX, named X-24, exhibiting a periodicity of ∼7500 s with a detection significance of 2.7
σ
. We speculate that it is the orbital period of the system. Roche-lobe overflow and Roche limit are consistent with the speculation. Thus, we suggest that X-24 may be one of the rare compact binary ULXs, and hence, a good candidate as a stellar-mass black hole.
Phosphorescent dopants are promising candidates for organic light‐emitting diodes (OLEDs). Although it has been established that the out‐coupling efficiency and overall performances of ...vacuum‐deposited OLEDs can be significantly improved by a horizontal orientation of the dopants, no horizontally oriented gold(III) complexes have been reported to date. Herein, a novel class of tetradentate C^C^N^N ligand‐containing gold(III) complexes with a preferential horizontal orientation successfully generated through a one‐pot reaction is reported. These complexes demonstrate high photoluminescence quantum yields of 70 % and a high horizontal dipole ratio of 0.87 in solid‐state thin films. Green‐emitting OLEDs based on these complexes operate with a maximum external quantum efficiency of 20.6 % with an estimated out‐coupling efficiency of around 30 %. A promising device stability has been achieved in the vacuum‐deposited OLEDs, with operational half‐lifetimes of around 37 500 h at 100 cd m−2.
A novel class of tetradentate C^C^N^N ligand‐containing gold(III) complexes with a preferential horizontal orientation has been obtained through a one‐pot reaction. A high maximum external quantum efficiency of 20.6 % has been realized in the vacuum‐deposited gold(III)‐based OLEDs, with operational half‐lifetimes of around 37 500 h at 100 cd m−2.
Full text
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We present the discovery and characterization of a radio-bright binary in the Galactic globular cluster M10. First identified in deep radio continuum data from the Karl G. Jansky Very Large Array, ...M10-VLA1 has a flux density of 27 4 Jy at 7.4 GHz and a flat-to-inverted radio spectrum. Chandra imaging shows an X-ray source with LX 1031 erg s−1 matching the location of the radio source. This places M10-VLA1 within the scatter of the radio-X-ray luminosity correlation for quiescent stellar-mass black holes, and a black hole X-ray binary is a viable explanation for this system. The radio and X-ray properties of the source disfavor, but do not rule out, identification as an accreting neutron star or white dwarf system. Optical imaging from the Hubble Space Telescope and spectroscopy from the SOAR telescope show that the system has an orbital period of 3.339 days and an unusual "red straggler" component: an evolved star found redward of the M10 red giant branch. These data also show UV/optical variability and double-peaked H emission characteristic of an accretion disk. However, SOAR spectroscopic monitoring reveals that the velocity semi-amplitude of the red straggler is low. We conclude that M10-VLA1 is most likely either a quiescent black hole X-ray binary with a rather face-on (i < 4°) orientation or an unusual flaring RS Canum Venaticorum variable-type active binary, and discuss future observations that could distinguish between these possibilities.
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