Effective Blackbody Temperature Research Articles

Soft X-Ray Excess from Shocked Black Hole Accretion

A certain class of luminous galaxies hosting supermassive black holes (BHs) is known to exhibit an excess of “soft X-rays” in their X-ray spectra. However, its physical identity and origin are yet to be understood. In this work, we systematically study a sample of 9 well-documented narrow-line Seyfert 1 active galactic nuclei by utilizing the archival XMM-Newton/EPIC spectra in the context of general relativistic magnetohydrodynamic model. In this scenario, thermal accretion disk photons (in UV) are Compton up-scattered by nonthermal energetic electrons in the hot downstream accretion due to shock compression, producing the observed soft excess. Our spectral model consists primarily of the shock Comptonization component and the underlying continuum including reflection from the accretion disk. Based on χ 2-statistics, we successfully constrain the model parameters, most notably electron energy of the downstream flow kT e , effective disk blackbody temperature kT bb, and inclination angle θ for a given BH spin. The disk temperature is commonly found to be kT bb 10 eV and the electron energy ranges from kT e 75–160 keV (for Schwarzschild BHs) to 126–232 keV (for Kerr BHs) depending on inclination. Our analyses imply that the characteristics of the observed soft excess are strongly dependent on the properties of the downstream accretion flow and BH spin.

Characterization of directional and anisotropic scattering dependency of emissivity for fibrous heat shields under non-isothermal conditions

The spectral and directional dependence of emissivity along with radiative emissions of scattering media has been characterized as functions of the optical thickness, scattering albedo, and anisotropic scattering phase function. Emissivity is found to be a strong function of the scattering albedo and the anisotropic scattering phase function of the medium, and a generalized relation between spectral emissivity and scattering behavior for thick optical media is developed through the use of Bézier curves. A comparison of the newly developed relation with the spectral emissivities of silica- and carbon-based fibrous media demonstrated excellent agreement, with a root mean square error of 0.19%. The characterization of directional emissivity through scattering media indicates that directional emissivity is higher than hemispherical emissivity in directions normal to the surface, but drops at polar angles greater than 50° because of increased reflection. A novel model is also developed to capture emissions from a medium with a non-uniform temperature distribution using the same emissivities derived under isothermal conditions, but with an effective blackbody temperature, which differs from the surface temperature of the medium. The new emission model exhibited excellent agreement compared to the true emissions under various conditions, with a root mean square error of 1.27%. This new approach offers a practical computationally tractable solution for the radiation energy balance at surfaces that can be used in current state-of-the-art computational fluid dynamics and thermal response simulations.

TESS Phase Curve of the Hot Jupiter WASP-19b

Abstract We analyze the phase curve of the short-period transiting hot Jupiter system WASP-19, which was observed by the Transiting Exoplanet Survey Satellite (TESS) in Sector 9. WASP-19 is one of only five transiting exoplanet systems with full-orbit phase curve measurements at both optical and infrared wavelengths. We measure a secondary eclipse depth of ppm and detect a strong atmospheric brightness modulation signal with a semiamplitude of 319 ± 51 ppm. No significant offset is detected between the substellar point and the region of maximum brightness on the dayside. There is also no significant nightside flux detected, which is in agreement with the nightside effective blackbody temperature of derived from the published Spitzer phase curves for this planet. Placing the eclipse depth measured in the TESS bandpass alongside the large body of previous values from the literature, we carry out the first atmospheric retrievals of WASP-19b’s secondary eclipse spectrum using the SCARLET code. The retrieval analysis indicates that WASP-19b has a dayside atmosphere consistent with an isotherm at T = 2240 ± 40 K and a visible geometric albedo of 0.16 ± 0.04, indicating significant contribution from reflected starlight in the TESS bandpass and moderately efficient day–night heat transport.

A remarkable recurrent nova in M 31: The predicted 2014 outburst in X-rays withSwift

The M 31 nova M31N 2008-12a was recently found to be a recurrent nova (RN) with a recurrence time of about 1 year. This is by far the fastest recurrence time scale of any known RNe. Our optical monitoring programme detected the predicted 2014 outburst of M31N 2008-12a in early October. We immediately initiated an X-ray/UV monitoring campaign with Swift to study the multiwavelength evolution of the outburst. We monitored M31N 2008-12a with daily Swift observations for 20 days after discovery, covering the entire supersoft X-ray source (SSS) phase. We detected SSS emission around day six after outburst. The SSS state lasted for approximately two weeks until about day 19. M31N 2008-12a was a bright X-ray source with a high blackbody temperature. The X-ray properties of this outburst were very similar to the 2013 eruption. Combined X-ray spectra show a fast rise and decline of the effective blackbody temperature. The short-term X-ray light curve showed strong, aperiodic variability which decreased significantly after about day 14. Overall, the X-ray properties of M31N 2008-12a are consistent with the average population properties of M 31 novae. The optical and X-ray light curves can be scaled uniformly to show similar time scales as those of the Galactic RNe U Sco or RS Oph. The SSS evolution time scales and effective temperatures are consistent with a high-mass WD. We predict the next outburst of M31N 2008-12a to occur in autumn 2015.

A remarkable recurrent nova in M 31: The X-ray observations

Another outburst of the recurrent M31 nova M31N 2008-12a was announced in late November 2013. Optical data suggest an unprecedentedly short recurrence time of approximately one year. In this Letter we address the X-ray properties of M31N 2008-12a. We requested Swift monitoring observations shortly after the optical discovery. We estimated source count rates and extracted X-ray spectra from the resulting data. The corresponding ultraviolet (UV) data was also analysed. M31N 2008-12a was clearly detected as a bright supersoft X-ray source (SSS) only six days after the well-constrained optical discovery. It displayed a short SSS phase of two weeks duration and an exceptionally hot X-ray spectrum with an effective blackbody temperature of ~97 eV. During the SSS phase the X-ray light curve displayed significant variability that might have been accompanied by spectral variations. The very early X-ray variability was found to be anti-correlated with simultaneous variations in the UV flux. The X-ray properties of M31N 2008-12a coherently point towards a high-mass white dwarf in the nova system. This object might be a promising Type Ia supernova progenitor. We re-discovered additional X-ray detections of M31N 2008-12a that are consistent with our data and increase the number of known nova outbursts to seven. This nova is an exceptional object that merits further attention in the future.

The Effect of Pressure Relief Valve Blowdown and Fire Conditions on the Thermo-Hydraulics Within a Pressure Vessel

In the summers of 2000 and 2001, a series of controlled fire tests were conducted on horizontal 1890liter (500 US gallon) propane pressure vessels. The test vessels were instrumented with pressure transducers, liquid space, vapor space, and wall thermocouples, and an instrumented flow nozzle in place of a pressure relief valve (PRV). A computer controlled PRV was used to control pressure. The vessels were heated using high momentum, liquid propane utility torches. Open pool fires were not used for the testing because they are strongly affected by wind. These wind effects make it almost impossible to have repeatable test conditions. The fire conditions used were calibrated to give heat inputs similar to a luminous hydrocarbon pool fire with an effective blackbody temperature in the range of 850°C±50°C. PRV blowdown (i.e., blowdown=poppressure−reclosepressure) and fire conditions were varied in this test series while all other input parameters were held constant. The fire conditions were varied by changing the number of burners applied to the vessel wall areas wetted by liquid and vapor. It was found that the vessel content’s response and energy storage varied according to the fire conditions and the PRV operation. The location and quantity of the burners affected the thermal stratification within the liquid, and the liquid swelling (due to vapor generation in the liquid) at the liquid∕vapor interface. The blowdown of the PRV affected the average vessel pressure, average liquid temperature, and time to temperature destratification in the liquid. Large blowdown also delayed thermal rupture.

On the thermal rupture of 1.9 m 3 propane pressure vessels with defects in their thermal protection system

This paper describes the results from a series of fire tests that were carried out to measure the effect of defects in thermal protection systems on fire engulfed propane pressure vessels. In North America thermal protection is used to protect dangerous goods rail tank-cars from accidental fire impingement. They are designed so that a tank-car will not rupture for 100 min in a defined engulfing fire, or 30 min in a defined torching fire. One common system includes a 13 mm blanket of high-temperature ceramic fibre thermal insulation covered with a 3 mm steel jacket. Recent inspections have shown that some tanks have significant defects in these thermal protection systems. This work was done to establish what levels of defect are acceptable from a safety standpoint. The tests were conducted using 1890 l (500 US gallon) ASME code propane pressure vessels (commonly called tanks in the propane industry). The defects tested covered ∼8% and 15% of the tank surface. The tanks were 25% engulfed in a fire that simulated a hydrocarbon pool fire with an effective blackbody temperature of ∼870 °C. The fire testing showed that even relatively small defects can result in tank rupture if the defect area is engulfed in a severe fire, and the defect area is not wetted by liquid from the inside. A wall failure prediction technique based on uniaxial high-temperature stress rupture test data has been developed and agrees well with the observed failure times.

Solar Irradiance and Effective Brightness Temperature for SWIR Channels of AVHRR/NOAA and GOES Imagers

Abstract Satellite observations in the shortwave infrared (SWIR) part of spectrum between 3.5 and 4.0 μm deliver critically important information for many applications. The satellite signal in this spectral band consists of solar-reflected radiation and thermal radiation emitted by surface, clouds, and atmosphere. Accurate retrievals require precise knowledge of solar irradiance values within a channel's bandwidth. The magnitudes of solar irradiance for shortwave infrared channels (3.7–3.9 μm) for the Advanced Very High Resolution Radiometer (AVHRR) on board the National Oceanic and Atmospheric Administration-7 (NOAA-7) to NOAA-18 satellites and the Geostationary Operational Environmental Satellite-8 (GOES-8) to GOES-12 are considered in this paper. Four recent solar reference spectra [those of Kurucz, Gueymard, the American Society for Testing and Materials (ASTM), and Wehrli] are analyzed to determine uncertainties in the knowledge of solar irradiance values for SWIR channels of the listed sensors. Because thermal radiation is frequently converted to effective blackbody temperature for analysis, computations, and calibration purposes, it is proposed here to express band-limited solar irradiance values in terms of brightness temperature as well. It is shown that band-limited solar irradiance for AVHRR radiometers expressed in terms of blackbody equivalent brightness temperature correspond to the range 355–360 K, and vary around 345 K for the SWIR channels of the GOES imagers. The values of band-limited solar irradiance and brightness temperatures are provided for various reference solar spectra. The relative differences in band-limited solar irradiance computed for the considered reference solar spectra are between 0% and 2.5%. Differences expressed in terms of brightness temperatures may reach 0.8 K. The results for the ASTM and the Kurucz reference spectra agree within 0.1% relative difference. Parameters of linear fits relating effective brightness temperatures and spectral radiance equivalent temperatures are also determined for all sensors. They are required for precise radiance–temperature and temperature–radiance conversion through Planck's functions in the case of the finite spectral response of real sensors.

Gas phase activation energy for unimolecular dissociation of biomolecular ions determined by focused RAdiation for gaseous multiphoton ENergy transfer (FRAGMENT)

We present a novel approach for the determination of activation energy for the unimolecular dissociation of a large (>50 atoms) ion, based on measurement of the unimolecular dissociation rate constant as a function of continuous-wave CO(2) laser intensity. Following a short ( approximately 1 s) induction period, CO(2) laser irradiation produces an essentially blackbody internal energy distribution, whose 'temperature' varies inversely with laser intensity. The only currently available method for measuring such activation energies is blackbody infrared radiative dissociation (BIRD). Compared with BIRD, FRAGMENT: (a) eliminates the need to heat the surrounding ion trap and vacuum chamber to each of several temperatures (each requiring hours for temperature equilibration); (b) offers a three-fold wider range of effective blackbody temperature; and (c) extends the range of applications to include initially cold ions (e.g., gas-phase H/D exchange). Our FRAGMENT-determined activation energy for dissociation of protonated bradykinin, 1.2 +/- 0.1 eV, agrees within experimental error to the value, 1.3 +/- 0.1 eV, previously reported by Williams et al. from BIRD experiments. Copyright 1999 John Wiley & Sons, Ltd.

Light emission during fracture of a Zr–Ti–Ni–Cu–Be bulk metallic glass

A light emission phenomenon observed during dynamic fracture of a bulk metallic glass, Zr41.2Ti13.8Cu12.5Ni10Be22.5 (at. %), has been investigated using Charpy V-notch impact specimens. Unlike more conventional crystalline metals, these Zr-based amorphous alloys emit intense flashes of visible light when ruptured. The mechanisms for this surprising behavior are unknown and the phenomenon remains uncharacterized. Here we report spectroscopic measurements of the light emitted from specimens fractured in both room air and nitrogen gas. Spectra acquired from specimens ruptured in air exhibited a single broad peak, which could be fit to a blackbody temperature of ∼3175 K. Emission from specimens fractured in nitrogen, however, was at least four orders of magnitude less intense. The spectrum was shifted to the red with an effective blackbody temperature of ∼1400 K. Fracture surfaces of specimens ruptured in both air and nitrogen exhibited local melting, providing further evidence of intense heating during fracture. Based on these observations we argue that the intense light emission in air is associated with pyrolysis of fresh material exposed during rupture.

Mechanism for Light Emission During Fracture of a Zr-Ti-Cu-Ni-Be Bulk Metallic Glass: Temperature Measurements in Air and Nitrogen

AbstractLight emitted during rupture of Zr41.2Ti13.8Cu12.5 Ni10Be22.5 (at%) bulk metallic glass has been investigated. Charpy V-notch specimens fractured in a pendulum impact apparatus were used to excite light emission. Spectra acquired from rupture in air exhibited a single broad peak and were fit to a blackbody temperature of ∼3175 K. In nitrogen, however, light emission was no longer visible to the eye. In this case, the captured light was at least four orders of magnitude less intense, and spectra were shifted to the red with an effective blackbody temperature of ∼1400 K. Fracture surfaces generated in both air and nitrogen exhibited local melting, providing further evidence of intense heating during fracture. Based on these observations we argue that the intense light emission in air is associated with pyrolysis of fresh material exposed during rupture. Results were compared to preliminary observations of light emission from ribbons of a Zr57Nb5Ni12.6Cu15.4Al10 (at%) glass.

Infrared projector effective blackbody temperature

The effective blackbody temperature used to specify the radiant output from an IR projector is defined formally as the temperature assumed by the blackbody target that generates the same signal radiance as the IR projector characterized. Analytical expressions and graphical analyses are developed enabling the calculation of the blackbody temperature in terms of both the actual device temperature and a specified active zone attenuation coefficient, the latter quantifying the deviation from blackbody behavior. Both the projector signal radiance and the signal current developed in the imaging unit under test illuminated by the projector are shown to be readily calculable once the value of the effective blackbody temperature is known. The analysis is applied to the comparison of the thin film resistor, silicon bridge resistor, and suspended membrane resistor emissive IR projection technologies.

Blackbody absorption efficiencies for six lamp pumped Nd laser materials

Utilizing high resolution spectra, the absorption efficiency for six Nd laser materials was calculated as functions of the effective blackbody temperature of the lamp and laser crystal size. The six materials were Nd:YAG, Nd:YLF, Nd:Q-98 Glass, Nd:YVO(4), Nd:BEL, and Nd:Cr:GSGG. Under the guidelines of this study, Nd:Cr:GSGG's absorption efficiency is twice the absorption efficiency of any of the other laser materials.

The infrared color evolution of active nuclei

view Abstract Citations (14) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Infrared Color Evolution of Active Nuclei Baan, Willem A. Abstract The far-infrared color evolution is studied for galaxies with a nuclear starburst or an AGN. The nuclear source heats the surrounding dust to an effective blackbody temperature (T_d_ = 50-100 K). The color and luminosity evolution for such galaxies is simulated by letting the central heating source and the resulting warm dust emission (the primary source) decay exponentially in combination with a slower decaying secondary IR emission source. Secondary spectral components can be nonthermal or (hot or cold) thermal in nature and may be associated with the nuclear activity or with the rest of the galaxy. The evolving far-infrared (FIR) galaxy traverses the FIR color diagrams in a rather systematic fashion, and an FIR galaxy can be modeled very effectively with an appropriate mixture of primary and secondary luminosity contributions. The secondary components must have an initial strength of 0.1-0.005 relative to the primary source. Superluminous FIR sources with dominant nuclear sources lie at the start of the simulated evolutionary tracks in the color-color diagrams. While these sources evolve across the color diagram they will reveal more of their nuclear characteristics and eventually they may appear to the observer as normal Seyferts or quasars. The group of powerful FIR sources also incorporates the OH megamaser galaxies. A luminosity function is constructed for the family of nuclear FIR sources. A single distribution of nuclear FIR sources can account for the observed luminosity function at high L_IR_. Another distribution of nonnuclear sources is required to explain the low-luminosity end. Publication: The Astrophysical Journal Pub Date: July 1988 DOI: 10.1086/166508 Bibcode: 1988ApJ...330..743B Keywords: Active Galactic Nuclei; Color-Color Diagram; Infrared Sources (Astronomy); Seyfert Galaxies; Far Infrared Radiation; Infrared Spectra; Interstellar Matter; Luminosity; Starburst Galaxies; Astrophysics; GALAXIES: NUCLEI; INFRARED: SOURCES; INTERSTELLAR: GRAINS full text sources ADS | data products SIMBAD (10) NED (6)

Estimating Noise Levels of Remotely Sensed Measurements from Satellites Using Spatial Structure Analysis

A technique is presented whereby the noise level of satellite measurements of the atmosphere and earth can be estimated. The technique analyzes a spatial array of data measured by a satellite instrument. A minimum of about 200 satellite measurements is required, preferably in a regular pattern. Statistical structure analysis is used to describe a combination of the mean gradient and noise in the data. The noise level is then estimated by separating out the gradient information and leaving only the noise. Results are presented for four satellite sounding instruments, and effective blackbody or brightness temperature noise levels were compared to prelaunch specifications or inflight calibrations for each instrument. Comparisons showed that in the absence of cloud-contaminated measurements (in the case of infrared data) and away from the highly variable ground surface, the noise level of various satellite instruments can be obtained without the need for calibration data. The noise levels imply how much spatial averaging is possible, without smearing the detected geophysical gradient, and how much is necessary, to meet the absolute signal accuracy requirements for the intended use of the satellite measurements.

Measurements of surface energy budgets in the Rocky Mountains of Colorado

The surface energy balance of a mountain valley and a mountain peak were continuously monitored for periods of 126 and 34 days, respectively. The data yielded temporally resolved, high‐quality measurements of the radiative, soil, and total atmospheric turbulent heat fluxes. Comparative data for the two sites reveal the effects of terrain setting and surface cover in modulating the heat balance. A procedure is suggested for accommodating local advective affects due to variable terrain and surface cover to allow partitioning of the total turbulent flux into values for sensible and latent heat. This procedure relies on a stability‐dependent coefficient of turbulent transfer which is locally calibrated to systematically minimize advection‐related errors. Scaling functions for the transfer coefficient are based on the effective blackbody temperature of the surface. Consequently, the procedure offers an opportunity for developing reliable bulk representations of heat transfer at the surface for use with remote sensing data and with models of the soil and surface cover in complex terrain.

Recent Results from the Japanese X‐Ray Astronomy Satellites

Observations of neutron stars and their environments, and the emission and absorption of iron, obtained with the Hakucho and Tenma satellites, are examined. The characteristics of X-ray bursts, neutron stars, and accretion disks, in particular spectra, color and effective temperatures, blackbody temperature and radius, the emissivity factor, and the Eddington limit luminosity, are discussed. Consideration is given to the rapid burster discovered by Lewin et al. (1976) and potential blackhole sources. 43 references.

How many equivalent black-body temperatures are there?

1. 1.|Several thermal indices, including “equivalent black-body temperature”, “effective blackbody ambient temperature” and “operative environmental temperature”, are identical with operative temperature and should be so designated. 2. 2.|“Standard operative environmental temperature”, essentially identical to standard operative tempature, is a distinct but related thermal index. 3. 3.|Operative temperature is an index of the potential driving heat flow, and must be used with a thermal resistance or conductance term. Standard operative temperature is a direct index of heat flow. 4. 4.|Both operative and standard operative temperature can either be calculated from animal and environmental heat-transfer parameters or be measured with taxidermic mounts.

Effective blackbody temperature of high-current gas-filled flashlamps

Under the assumption that a high-current gas-filled flashlamp is a fully ionized plasma and radiates as a blackbody, an expression for the effective blackbody temperature of the flashlamp is derived. This calculation is compared with the experimental results from several sources.

Measurement of the Error of Temperature Sensors in Flowing Gases

Received January 6, 1972; revision received March 6, 1972. Index categories: Radiation and Radiative Heat Transfer; Research Facilities and Instrumentation. * Research Mechanical Engineer; formerly Graduate Student, Mechanical Engineering Department, Tulane University. t Associate Professor, Mechanical Engineering Department; presently at Purdue University, Indianapolis, Indiana. k = thermal conductivity of wire Nu = Nu 'selt number Pr == Prandtl number Re = Reynolds number T — absolute temperature 7^ = effective black body temperature of the environment of the sensor as seen by the sensor V = gas velocity x = coordinate along wire axis a = absorptivity of sensor e = emissivity of sensor a = Stefan-Boltzmann constant