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%.
Forty years passed since the optical identification of the first isolated neutron star (INS), the Crab pulsar. 25 INSs have been now identified in the optical (O), near-ultraviolet (nUV), or ...near-infrared (nIR), hereafter UVOIR, including rotation-powered pulsars (RPPs), magnetars, and X-ray-dim INSs (XDINSs), while deep investigations have been carried out for compact central objects (CCOs), Rotating RAdio transients (RRATs), and high-magnetic field radio pulsars (HBRPs). In this review I describe the status of UVOIR observations of INSs, their emission properties, and I present the results from recent observations.
Abstract
We present results of optical-UV observations of the 200 Myr old rotation-powered radio pulsar J0108−1431 with the Hubble Space Telescope. We found a putative candidate for the far-UV (FUV) ...pulsar counterpart, with the flux density
f
ν
= 9.0 ± 3.2 nJy at
λ
= 1528 Å. The pulsar was not detected, however, at longer wavelengths, with 3
σ
upper limits of 52, 37, and 87 nJy at
λ
= 4326, 3355, and 2366 Å, respectively. Assuming that the pulsar counterpart was indeed detected in FUV, and the previously reported marginal
U
and
B
detections with the Very Large Telescope were real, the optical-UV spectrum of the pulsar can be described by a power-law model with a nearly flat
f
ν
spectrum. Similar to younger pulsars detected in the optical, the slope of the nonthermal spectrum steepens in the X-ray range. The pulsar’s luminosity in the 1500–6000 Å wavelength range,
L
∼ 1.2 × 10
27
(
d
/210 pc)
2
erg s
−1
, corresponds to a high efficiency of conversion of pulsar rotation energy-loss rate
to the optical-UV radiation,
, depending on somewhat uncertain values of distance and spectral slope. The brightness temperature of the bulk neutron star surface does not exceed 59,000 K (3
σ
upper bound), as seen by a distant observer. If we assume that the FUV flux is dominated by a thermal component, then the surface temperature can be in the range of 27,000–55,000 K, Requiring a heating mechanism to operate in old neutron stars.
On the PSR B1133+16 optical counterpart Zharikov, Sergey; Mignani, Roberto P.
Monthly notices of the Royal Astronomical Society,
11/2013, Volume:
435, Issue:
3
Journal Article
Peer reviewed
The aim of this work is to confirm the optical identification of PSR B1133+16, whose candidate optical counterpart was detected in Very Large Telescope (VLT) images obtained back in 2003. We used new ...deep optical images of the PSR B1133+16 field obtained with both the 10.4 m Gran Telescopio Canarias (GTC) and the VLT in the g
′ and B bands, respectively, to confirm the detection of its candidate optical counterpart and its coincidence with the most recent pulsar's radio coordinates. We did not detect any object at the position of the pulsar candidate counterpart (B ∼ 28), measured in our 2003 VLT images. However, we tentatively detected an object of comparable brightness in both the 2012 GTC and VLT images, whose position is offset by ∼ 3.03 arcsec from that of the pulsar's candidate counterpart in the 2003 VLT images and lies along the pulsar's proper motion direction. Accounting for the time span of ∼9 yr between the 2012 quasi-contemporary GTC and VLT images and the 2003 VLT one, this offset is consistent with the yearly displacement of the pulsar due to its proper motion. Therefore, both the flux of the object detected in the 2012 GTC and VLT images and its position, consistent with the proper motion-corrected pulsar radio coordinates, suggest that we have detected the candidate pulsar counterpart that has moved away from its 2003 discovery position.
Isolated neutron stars are known to be endowed with extreme magnetic fields, whose maximum intensity ranges from1012–1015G, which permeates their magnetospheres. Their surrounding environment is also ...strongly magnetized, especially in the compact nebulae powered by the relativistic wind from young neutron stars. The radiation from isolated neutron stars and their surrounding nebulae is, thus, supposed to bring a strong polarization signature. Measuring the neutron star polarization brings important information about the properties of their magnetosphere and of their highly magnetized environment. Being the most numerous class of isolated neutron stars, polarization measurements have been traditionally carried out for radio pulsars, hence in the radio band. In this review, I summarize multi-wavelength linear polarization measurements obtained at wavelengths other than radio both for pulsars and other types of isolated neutron stars and outline future perspectives with the upcoming observing facilities.
ABSTRACT A particularly intriguing recent result from γ-ray astronomy missions is the detection of powerful flares from the Crab Nebula, which challenges the current understanding of pulsar wind ...nebulae and acceleration mechanisms. To search for the production site(s) of these flares, we conducted a multi-wavelength observing campaign using Keck, the Hubble Space Telescope (HST), and the Chandra X-ray Observatory. As the short timescales of the γ-ray flares ( day) suggest a small emitting region, the Crab's inner knot (about 0.6 arcsec from the pulsar) is a candidate site for such flaring. This paper describes observations of the inner knot, seeking to understand its nature and possible relationship with γ-ray flares. Using singular-value decomposition, analysis of the HST images yielded results consistent with traditional methods while substantially reducing some uncertainties. These analyses show that the knot's intrinsic properties (especially size and brightness) are correlated with its (projected) separation from the pulsar. This characterization of the inner knot helps in constraining standard shock model parameters, under the assumption that the knot lies near the shocked surface. While the standard shock model gives good agreement in several respects, two puzzles persist: (a) the observed angular size of the knot relative to the pulsar-knot separation is much smaller than expected; and (b) the variable high degree of polarization (reported by others) is difficult to reconcile with a highly relativistic downstream flow. However, the IR-optical flux of the inner knot is marginally consistent with the shock accelerating most of the Nebula's optical-emitting particles.
An anomalous effect in the near field of crossing microwave beams, which consists of an unexpected transfer of modulation from one beam to the other, has found a plausible interpretation within the ...framework of a locally broken Lorentz invariance. A theoretical approach of this kind deserves to be reconsidered also in the light of further experimental work, including a counter-check of the phenomenon.
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