Observations Of Thermal Radiation Research Articles

Neutron Stars—Cooling and Transport

Observations of thermal radiation from neutron stars can potentially provide information about the states of supranuclear matter in the interiors of these stars with the aid of the theory of neutron-star thermal evolution. We review the basics of this theory for isolated neutron stars with strong magnetic fields, including most relevant thermodynamic and kinetic properties in the stellar core, crust, and blanketing envelopes.

Application of flash thermography for crack identification in concrete materials

Deterioration of concrete materials is always initiated with the formation of cracks. Therefore, monitoring crack formation and their propagation is crucial in concrete durability assessment. This paper proposes to apply short-duration pulsed thermography - flash thermography (FT) - for surface crack detection. It allows full-field and noncontact qualitative observation of thermal radiation from the object surface and is widely accepted in the aerospace industry. It is superior to the common practice of surface crack detection - visual inspection - since overall inspection time is saved and the maintenance costs are lowered. FT can be employed to detect and monitor a large number of cracks at the same time with just a flash time. A surface crack is detected based on the difference in light and IR radiation reflections between the cracks and intact region. The surface cracks, with widths ranging from 0.04 mm to 0.6 mm, are inspected and the results show that FT can detect surface cracks with widths larger than 0.32 mm successfully without further image processing. First-derivative processing has been applied and finer cracks of widths ranging from 0.04 mm to 0.1 mm can be observed.

Pycnonuclear reactions in dense stellar matter

We discuss pycnonuclear burning of highly exotic atomic nuclei in deep crusts of neutron stars, at densities up to 1e13 g/cc. As an application, we consider pycnonuclear burning of matter accreted on a neutron star in a soft X-ray transient (SXT, a compact binary containing a neutron star and a low-mass companion). The energy released in this burning, while the matter sinks into the stellar crust under the weight of newly accreted material, is sufficient to warm up the star and initiate neutrino emission in its core. The surface thermal radiation of the star in quiescent states becomes dependent of poorly known equation of state (EOS) of supranuclear matter in the stellar core, which gives a method to explore this EOS. Four qualitatively different model EOSs are tested against observations of SXTs. They imply different levels of the enhancement of neutrino emission in massive neutron stars by (1) the direct Urca process in nucleon/hyperon matter; (2) pion condensates; (3) kaon condensates; (4) Cooper pairing of neutrons in nucleon matter with the forbidden direct Urca process. A low level of the thermal quiescent emission of two SXTs, SAX J1808.4-3658 and Cen X-4, contradicts model (4). Observations of SXTs test the same physics of dense matter as observations of thermal radiation from cooling isolated neutron stars, but the data on SXTs are currently more conclusive.

Retrieval of vertical constituents and temperature profiles from passive submillimeter wave limb observations of the Martian atmosphere: a feasibility study

The investigation of the Martian atmosphere is of key importance for an understanding of the planets present and past. Passive limb observations of thermal radiation at submillimeter wavelengths in the 320-350-GHz range by use of a state-of-the-art satellite receiver on a low Mars orbit allow important parameters such as the mixing ratios of H2O, HDO, 12CO, 13CO, O3, and H2O2 as well as the thermal profile to be retrieved with high precision and unprecedented vertical range and resolution, providing valuable information for better understanding of the planet's water cycle, atmospheric dynamics, and photochemistry. The feasibility of these kinds of measurement is demonstrated by means of model simulations based on realistic atmospheric, spectroscopic, and instrumental parameters. Temperature can be retrieved to approximately 90 km with half-scale height vertical resolution from single-scan measurements of emission lines of the long-lived species 12CO and 13CO. The global water-vapor distribution can be measured even under dry or wet conditions with good vertical resolution from the surface to approximately 45 km, and simultaneous observations of HDO allow useful information on the D/H ratio up to an altitude of approximately 30 km to be derived. The sensitivity of the limb-sounding technique also permits information on the photochemically important minor species O3, and H2O2 to be obtained. It is shown that spectral averaging may improve precision, altitude range, and resolution of the retrieved profiles. Other frequency bands are explored, and the 435-465-GHz range is suggested as a possible alternative to the 320-350-GHz range.

Neutron star cooling

The impact of nuclear physics theories on cooling of isolated neutron stars is analyzed. Physical properties of neutron star matter important for cooling are reviewed such as composition, the equation of state, superfluidity of various baryon species, neutrino emission mechanisms. Theoretical results are compared with observations of thermal radiation from neutron stars. Current constraints on theoretical models of dense matter, derived from such a comparison, are formulated.

Neutron Star Cooling

▪ Abstract Observation of cooling neutron stars can potentially provide information about the states of matter at supernuclear densities. We review physical properties important for cooling such as neutrino emission processes and superfluidity in the stellar interior, surface envelopes of light elements owing to accretion of matter, and strong surface magnetic fields. The neutrino processes include the modified Urca process and the direct Urca process for nucleons and exotic states of matter, such as a pion condensate, kaon condensate, or quark matter. The dependence of theoretical cooling curves on physical input and observations of thermal radiation from isolated neutron stars are described. The comparison of observation and theory leads to a unified interpretation in terms of three characteristic types of neutron stars: high-mass stars, which cool primarily by some version of the direct Urca process; low-mass stars, which cool via slower processes; and medium-mass stars, which have an intermediate behavior. The related problem of thermal states of transiently accreting neutron stars with deep crustal burning of accreted matter is discussed in connection with observations of soft X-ray transients. Observations imply that some stars cool more rapidly than can be explained on the basis of nonsuperfluid neutron star models cooling via the modified Urca process, whereas other star cool less rapidly. We describe possible theoretical models that are consistent with observations.

Emissivity as a method of surfaces and thin films analysis

Limited to the field of pyrometry, the observation of thermal radiation has never been really used as a source of information for the characterization of material surface. An IR spectrometry technique which is briefly described has been conceived in order to study the influence of surface physico-chemical parameters on the directional and spectral emissivity (ελθ) of materials. One of these apparatus has been set up on a conventional UHV system equipped with AES and SIMS. The variation (Δϵϵ)λθ is recorded in situ during the evolution of a surface parameter. The examples shown are platinum deposit on graphite by vapour condensation, growth of an oxide film on metal, growth of homogeneous or inhomogeneous films, influence of the crystalline phase transition of a deposit, etc. For each case, an optical theoretical description has been carried out. From the comparison with other observations (electron microscopy. X-ray diffraction, AES and kinetic measurements), it is shown how the observation of (Δϵ)λθ enables us to obtain information on parameters such as the number, the shape or the orientation of islands in granular deposits, the crystal structure, the porosity of a film or the failure critical thickness of a coating.

Neutron star disk formation from supernova fall-back and possible observational consequences

We have examined a simple model for gravitational fall-back of supernova ejecta to estimate the effect of delayed fall-back on pulsar activity from the central neutron star. Direct dimensional arguments suggest that a Kepler disk will be created with a mass of the order of 10−5 M⊙ for the probable initial magnetic fields and rotation rates. It has already been argued that such a disk would be required for pulsar action. The disk expected to be formed by fall-back is, at first, too distant to favour pulsar action. We therefore predict a neutron star disk that may be detectable when the nebula around SN1987A clears, although the same model also suggests that the pulsar action might not at first be taking place. Because this disk should be composed of the same sort of shocked and highly processed matter that presently maintains the supernova light curve through radioactive heating, the disk should be hot and luminous, thereby providing a point power-law optical source in the nebula. Thus, observational possibilities include: (1) observation of thermal radiation from the disk, (2) observation of X-rays from a transient episode of accretion on to the neutron star, and (3) a delayed turn-on of the pulsar.

Infrared Observations of Asteroids

This paper is a brief preliminary report about a program of reconnaissance photometry designed to study the thermal radiation emitted from asteroids. Observations of thermal radiation, and their subsequent interpretation, can provide new knowledge that presently cannot be gained by any other method. The emitted thermal power is by and large that portion of the insolation which is absorbed. Part of the asteroid’s emission spectrum can be observed through windows in Earth’s atmosphere. With the aid of models for the details of energy transfer at the asteroid’s surface, and accurate visual photometry, reliable estimates can be made for some of the important parameters in the models. Of particular interest are Bond albedo, size, emissivity, and thermal inertia.