NEW OPTICAL/ULTRAVIOLET COUNTERPARTS AND THE SPECTRAL ENERGY DISTRIBUTIONS OF NEARBY, THERMALLY EMITTING, ISOLATED NEUTRON STARS
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We present Hubble Space Telescope optical and ultraviolet photometry for five nearby, thermally emitting neutron stars. With these measurements, all seven such objects have confirmed optical and ultraviolet counterparts. Combining our data with archival space-based photometry, we present spectral energy distributions for all sources and measure the "optical excess": the factor by which the measured photometry exceeds that extrapolated from X-ray spectra. We find that the majority have optical and ultraviolet fluxes that are inconsistent with that expected from thermal (Rayleigh-Jeans) emission, exhibiting more flux at longer wavelengths. We also find that most objects have optical excesses between 5 and 12, but that one object (RX J2143.0+0654) exceeds the X-ray extrapolation by a factor of more than 50 at 5000 A, and that this is robust to uncertainties in the X-ray spectra and absorption. We consider explanations for this ranging from atmospheric effects, magnetospheric emission, and resonant scattering, but find that none is satisfactory.Keywords:
Ultraviolet
Spectral energy distribution
The purpose of this paper is to present a method to self‐calibrate the spectral energy distribution (SED) of objects in a survey based on the fitting of a SED library to observed multicolor photometry. We adopt, for illustrative purposes, the Vilnius and Gunn & Stryker SED libraries. The self‐calibration technique can improve the quality of observations which are not taken under perfectly photometric conditions. The more passbands used for the photometry, the better the results. This technique has been applied to the BATC 15 passband CCD survey.
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In association with the Goldreich-Julian's magnetic braking mechanism to explain the luminosity of radio pulsars as a result of their spin-down, it is of some interest to explore how much of magnetic flux can actually penetrate the surface of the rotating neutron stars at least in idealized situations. In order to address this issue, one needs to figure out the amount of charge on and the structure of magnetic field around a rotating neutron star. In the present work, based on the solution-generating method given by Wald, the magnetic fields around both the uncharged and (slightly) charged neutron star have been obtained. Particularly for the charged neutron star, it has been demonstrated following again the argument by Wald that the neutron star will gradually accrete the charge until it reaches the equilibrium value $\tilde{Q}=2B_{0}J$. Then next, the magnetic flux through one half of the surface of the rotating neutron star has been computed as well. With the nonvanishing accretion charge having value in the range $0 < \tilde{Q} \leq 2B_{0}J$, the total magnetic flux through the neutron star has been shown to be greater than that without the accretion charge.
Star (game theory)
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An energy distribution for P Cyg (B1 Ia+) has been produced using UKIRT photometry and spectra, flux-calibrated IUE high-resolution spectra, Johnson and Mitchell 13-colour photometry and IRAS photometry. Infrared excesses due to free-free emission from the wind have then been derived and modelled.
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Energy distribution
Spectrum analysis
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Color temperatures have been estimated by comparing ultraviolet observations of HgMn and magnetic Ap stars with those of normal stars. Ultraviolet data from the OAO-2, ANS, TD-1, and IUE satellites generally give similar results. The values for the normal stars were derived from comparison of fluxes predicted by solar-composition fully line-blanketed model atmospheres with optical region spectrophotometry. The ultraviolet temperatures of the HgMn stars cover a narrower temperature range than do their optical region values. Magnetic Ap stars with similar optical region temperatures can show substantial differences in their ultraviolet color temperatures. This may result from magnetic field configuration and abundance differences.
Ultraviolet
Ultraviolet astronomy
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We investigate the quantum hadrodynamic equation of state for neutron stars (with and without including hyperons) in the presence of strong magnetic fields. The deduced masses and radii are consistent with recent observations of high mass neutron stars even in the case of hyperonic nuclei for sufficiently strong magnetic fields. The calculated adiabatic index and the moments of inertia for magnetized neutron stars exhibit rapid changes with density. This may provide some insight into the mechanism of star-quakes and flares in magnetars.
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Abstract I comment on some of the steps required to convert raw instrumental magnitudes, derived by profile-fitting or synthetic-aperture photometry from CCD images, to final calibrated photometry on a standard system. The status of the DAO program to obtain homogeneous BV photometry for star clusters and nearby galaxies will also be discussed.
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The design considerations and operation features of DoPHOT, a point spread function fitting (PSF) photometry program, are described. Some relevant details of the PSF fitting are discussed. The quality of the photometry returned by DoPHOT is assessed via reductions of an 'artificial' globular cluster generated from a list with well known magnitudes and colors. Results from comparative tests between DoPHOT and DAOPHOT using this synthetic cluster and real data are also described.
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This Technical Note gives guidance on the use of terms and units in photometry, particularly in relation to terms and units applicable for mesopic photometry. It can be used in conjunction with CIE 191:2010 Recommended System for Mesopic Photometry based on Visual Performance, which gives details of the method that should be used to calculate mesopic quantities and is fully compliant with the requirements of the SI system and the principles governing photometry, as published by the Bureau International des Poids et Mesures (BIPM). Keywords: photometry, mesopic vision
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A review is given for the progress of the photometric analysis of copper in China according to general photometry,dual-wavelength photometry,three wavelength photometry,extraction photometry,flotation photometry,kinetic photometry,flow injection photometry,calculation photometry,fluorescence spectrophotometry during the recent year(1998-2001) One hundred and forty seven references were cited
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