SPECTRAL ENERGY DISTRIBUTIONS OF THE MAJOR PLANETS
Spectral energy distributions of the major planets based on color photometry measurements, including scanning and data reduction procedures
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Redshifts and absolute spectral energy distributions of galaxies in distant clusters.
Absolute spectral energy distributions were measured in galaxies of three distant clusters. Redshifts and information on evolutionary effects are inferred by a comparison of the results with the integrated light energy distribution for nearby giant elliptical galaxies. Evidence for evolution over the last 3 to 6 billion years could not be established for these galaxies.
Oke, J. B.↗
The spectral energy distribution of NGC 1275
An analysis of absolute spectral energy distributions of interstellar gas for a galaxy (NGC 1275) is presented. Infrared spectra data shows heavy reddening. It is proposed that the interstellar gas may be ionized by shock waves or by nonthermal or stellar radiation. It is suggested, that high velocity, emission-line knots are H2 regions in a Perseus cluster galaxy or intergalactic gas cloud seen in projection against NGC 1275.
Shields, G. A.↗
The spectral energy distribution of NGC 1275
An analysis of absolute spectral energy distributions for NGC 1275 (Per A) covering the wavelength interval from 3300 A to 10,800 A is presented. The data are consistent with the heavy reddening discovered by Wampler (1971). The H-alpha intensity varied by less than 10% between the times of Wampler's earlier measurements and the two occasions of the present observations. The line-emitting region has a characteristic density of about 10 to the 4.5 power per cu cm, a mass of about 10 to the 5.5 power solar masses, and a volume filling factor of about 10 to the -6th power. The gas may be ionized by shock waves or by nonthermal or stellar radiation. It is suggested, in the vein of Minkowski's (1957) original proposal, that the high-velocity emission-line knots described by Minkowski are H II regions in a Perseus-cluster galaxy or intergalactic gas cloud seen in projection against NGC 1275.
Shields, G. A.↗
Spectral energy distributions of hot stars with circumstellar dust
Combined spectral energy distribution curves of six Ae/Be stars (BD+61 deg 154, AB Aur, V380 Ori, HD 259431, ZCMa, and BD+40 deg 4124), five peculiar shell stars (HD 31648, HD 45677, HD 50138, HD 163296, and HD 190073), and the peculiar central object in the Red Rectangle nebula (HD 44179), obtained with the IUE and a variety of ground-based optical and infrared telescope systems, are presented, covering the wavelength range of approximately 1300 A to 12.5 microns. The observations are reviewed, and include ultraviolet observations, low-resolution absolute visual spectrophotometry, moderate-resolution relative visual spectrophotometry, and infrared photometry. For most of the objects the ratio of the flux deficiency for lambda equals less than 1 micron to the flux excess for lambda equals greater than 1 micron is approximately unity. Only two of the objects (AB Aur and HD 163296) possess a strong emission feature at 9.7 microns, while one other (HD 31648) may have a weak 9.7 micron emission feature. Most of the objects have a broad, smooth, infrared emission curve resembling those seen in some WC stars. It is concluded that the dust surrounding these stars may be different from that seen in the diffuse interstellar medium.
Sitko, M. L.↗
On the spectral energy distributions of blazars
The multifrequency spectral properties of complete samples of three kinds of blazars observed with the Rosat position sensitive proportional counter (PSPC) in pointed mode are investigated: radio selected BL Lacs (RBLs); X-ray selected BL Lacs (XBLs); and flat spectrum radio quasars (FSRQs). Their spectral energy distributions are compared. The bolometric luminosities and peak emission frequencies of each source are estimated by fitting parabolic functions to the individual rest frame spectra of the power per decade. The shape of the optical to X-ray continua is described, and it is found that the continua of XBLs are convex while those of FSRQs are concave.
Maraschi, L.↗
The spectral energy distribution of Zeta Puppis and HD 50896
The ultraviolet spectral energy distribution of the O5f star Zeta Pup and the WN5 star HD 50896 are derived from OAO-2 observations with the calibration of Bless, Code, and Fairchild (1976). An estimate of the interstellar reddening (0.12 magnitude) of the Wolf-Rayet star is determined from the size of the characteristic interstellar extinction bump at 4.6 inverse microns. After correction for extinction, both stars show a flat energy distribution in the ultraviolet. The distribution of HD 50896 from 1100 A to 2 microns is in good agreement with results of extended model atmospheres, but some uncertainty remains because of the interstellar-extinction correction. The absolute energy distribution of Zeta Pup is fitted by a 42,000-K plane-parallel model if the model's flux is adjusted for the effects of electron scattering in the stellar wind and for UV line blanketing that was determined empirically from high-resolution Copernicus satellite observations. To achieve this fit, it is necessary to push both the spectroscopically determined temperature and the ultraviolet calibration to the limits of their probable errors.
Holm, A. V.↗
Uncovering the Spectral Energy Distribution in Active Galaxies Using High Ionization Mid-Infrared Emission Lines
The shape of the spectral energy distribution of active galaxies in the EUV soft X-ray band (13.6 eV to 1 keV) is uncertain because obscuration by dust and gas can hamper our view of the continuum. To investigate the shape of the spectral energy distribution in this energy band, we have generated a set of photoionization models which reproduce the small dispersion found in correlations between high-ionization mid-infrared emission lines in a sample of hard X-ray selected AGN. Our calculations show that a broken power-law continuum model is sufficient to reproduce the [Ne V]14.32 microns/[Ne III], [Ne V]24.32 microns/[O IV]25.89 micron and [O IV] 25.89 microns/[Ne III] ratios, and does not require the addition of a "big bump" EUV model component. We constrain the EUV-soft X-ray slope, alpha(sub i), to be between 1.5 - 2.0 and derive a best fit of alpha(sub i) approx. 1.9 for Seyfert 1 galaxies, consistent with previous studies of intermediate redshift quasars. If we assume a blue bump model, most sources in our sample have derived temperatures between T(sub BB) = 10(exp 5.18) K to 10(exp 5.7) K, suggesting that the peak of this component spans a large range of energies extending from approx. (Lambda)600 A to > (Lambda)1900 A. In this case, the best fitting peak energy that matches the mid-infrared line ratios of Seyfert 1 galaxies occurs between approx. (Lambda)700-(Lambda)1000 A. Despite the fact that our results do not rule out the presence of an EUV bump, we conclude that our power-law model produces enough photons with energies > 4 Ry to generate the observed amount of mid-infrared emission in our sample of BAT AGN.
Melendez, M.↗
Spectral energy distributions of the brightest Palomar-Green quasars at intermediate redshifts
We have combined low-dispersion International Ultraviolet Explorer (IUE) spectra with the optical/near-IR spectrophotometry of Neugebauer et al. (1987) in order to study the spectral energy distributions of seven of the brightest Palomar-Green (PG) quasars at intermediate redshifts (Z(sub em) greater than or equal to 0.9 and less than or equal to 1.5). Some of these PG quasars are barely detectable in long IUE exposures, so we have used the Gaussian Extraction (GEX) technique to maximize the signal-to-noise of the IUE data, and we have co-added all spectra available from the IUE archive for each QSO unless the ultraviolet spectra varied significantly from one exposure to the next. We have corrected the spectral energy distributions for Milky Way reddening using the observed neutral hydrogen column densities on each sight line and the gas-to-dust relation recently derived by Diplas & Savage. Six of the seven quasars are detected down to lambda much less than 700 A in the rest frame, and consequently continuum reddening due to dust in the immediate vicinity of the quasar can have a dramatic effect on the spectral energy distributions. In order to explore the possible importance of intrinsic continuum reddening, we have assembled a heuristic extinction curve which extends to lambda much less than 912 A. Using this heuristic extinction curve, we derive reasonable upper limits on the intrinsic E(B-V) for each quasar. We briefly discuss some of the implications of the derived intrinsic continuum reddening limits. We use geometrically thin accretion disk models to derive the black hole masses and accretion rates implied by the spectral energy distributions. Even if we neglect intrinsic reddening, we find that a large fraction of the quasars require super-Eddington accretion rates (which is not consistent with the thin disk assumption). Comparison of the data in this paper to a large body of data from the literature on the accretion disk M(sub BH) - M dot grid calculated by Wandel & Petrosian reveals that our quasars are among the brightest in the sky at 1450 A, and ostensibly suggests that the fraction of quasars which require super-Eddington accretion rates is much smaller than the fraction that we derive from our data alone. However, intrinsic continuum reddening has been ignored in this comparison, and a small amount of intrinsic reddening will push more of the quasars into the super-Eddington regime. We also plot the recent reverberation monitoring results on NGC 5548 and NGC 3783 on the Wandel & Petrosian grid, and we find that these Seyfert galaxies appear to vary along lines of constant M(sub BH). Continuum flux from two of the quasars in our main sample, PG 1338+416 and PG 1630+377, is detected at lambda(sub rest) less than 584 A. These quasars can in principle be used for the He I Gunn-Peterson test, but the S/N of IUE spectra of individual objects is usually too low to place interesting limits on the Gunn-Peterson optical depth. In order to improve the S/N, we have formed a composite spectrum from the spectra of five quasars detected with IUE at lambda(sub rest) less than 584 A, and we have used this composite spectrum to place a tighter limit on tau(sub GP, He I). We briefly discuss intermediate-redshift Lyman limit systems (Z(sub LL) greater than or equal to 0.5 and less than or equal to 1.6) detected in the IUE spectra of five quasars, including lower limits on N(H I) in each Lyman limit system.
Tripp, Todd M.↗
Planck Early Results. XV. Spectral Energy Distributions and Radio Continuum Spectra of Northern Extragalactic Radio Sources
Spectral energy distributions (SEDs) and radio continuum spectra are presented for a northern sample of 104 extragalactic radio sources. based on the Planck Early Release Compact Source Catalogue (ERCSC) and simultaneous multi frequency data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous observations ranging from radio to gamma-rays. This is the first extensive frequency coverage in the radio and millimetre domains for an essentially complete sample of extragalactic radio sources, and it shows how the individual shocks, each in their own phase of development, shape the radio spectra as they move in the relativistic jet. The SEDs presented in this paper were fitted with second and third degree polynomials to estimate the frequencies of the synchrotron and inverse Compton (IC) peaks, and the spectral indices of low and high frequency radio data, including the Planck ERCSC data, were calculated. SED modelling methods are discussed, with an emphasis on proper. physical modelling of the synchrotron bump using multiple components. Planck ERCSC data also suggest that the original accelerated electron energy spectrum could be much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The implications of this are discussed for the acceleration mechanisms effective in blazar shock. Furthermore in many cases the Planck data indicate that gamma-ray emission must originate in the same shocks that produce the radio emission.
Aatrokoski, J.↗
An Array of Frequency Selective Bolometers (FSB) for the Spectral Energy Distribution (SPEED) Camera
The SPEED camera is being developed to study the spectral energy distributions of high redshift galaxies using the Heinrich Hertz Telescope (HHT) in Arizona. SPEED requires a small cryogenic detector array of 2x2 pixels with each pixel having four frequency bands in the 150-350 GHz range. Here we describe the development of the detector array of these high efficiency FSBs. The FSB design provides the multi-pixel multi-spectral band capability required for SPEED in a compact stackable array. The SPEED bolometers will use proximity effect superconducting transition edge sensors as their temperature-sensing element allowing for higher levels of multiplexing in future applications.
Silverberg, R. F.↗
The Mega-MUSCLES Treasury Survey: X-Ray to Infrared Spectral Energy Distributions of a Representative Sample of M Dwarfs
We present 5–1 × 107 Å spectral energy distributions (SEDs) for 12 M dwarf stars covering spectral types M0–M8. Our SEDs are provided for community use as a sequel to the Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems (MUSCLES) survey. The 12 stars include eight known exoplanet hosts and four stars chosen to fill out key parameter space in spectral type and rotation period. The SEDs are constructed from Hubble Space Telescope ultraviolet spectroscopy and XMM Newton, Chandra, and/or Swift X-ray observations, and completed with various model data, including Lyα reconstructions, PHOENIX optical models, APEC coronal models, and differential emission measure models in the currently-unobservable extreme ultraviolet. We provide a complete overview of the Mega-MUSCLES program, including a description of the observations, models, and SED construction. The SEDs are available as MAST high-level science products and we describe the various data products here. We also present ensemble measurements from our sample that are of particular relevance to exoplanet science, including the high-energy fluxes in the habitable zone and the farultraviolet to near-ultraviolet ratio. Combined with MUSCLES, Mega-MUSCLES provides SEDs covering a wide range of M dwarf spectral types and ages such that suitable proxies for any M dwarf planet host of interest may be found in our sample. However, we find that ultraviolet and X-ray fluxes can vary even between stars with similar parameters, such that observations of each exoplanet host star will remain the gold standard for interpreting exoplanet atmosphere observations.
David J. Wilson↗
The Spectral Energy Distribution of the Seyfert Galaxy Ton S180
We present spectral results from a multi-satellite, broad-band campaign on the Narrow-line Seyfert 1 galaxy Ton S180 performed at the end of 1999. We discuss the spectral-energy distribution of the source, combining simultaneous Chandra, ASCA and EUVE data with contemporaneous FUSE, HST, and ground-based optical and infrared data. The resulting SED shows that most of the, energy is emitted in the 10 - 100 eV regime, which must be dominated by the primary energy source. No spectral turnover is evident in the UV regime. This, the strong soft X-ray emission, and the overall shape of the SED indicate that emission from the accretion disk peaks between 15 and 100 eV. High resolution FUSE spectra showing UV absorption due to OVI and the lack of detectable X-ray absorption in the Candra spectrum demonstrate the presence of a low column density of highly ionized gas along our line of sight.
Turner, T. J.↗
Distance Estimate Method for Asymptotic Giant Branch Stars Using Infrared Spectral Energy Distributions
We present a method to estimate distances to asymptotic giant branch (AGB) stars in the Galaxy, using spectral energy distributions (SEDs) in the near- and mid-infrared. By assuming that a given set of source properties (initial mass, stellar temperature, composition, and evolutionary stage) will provide a typical SED shape and brightness, sources are color matched to a distance-calibrated template and thereafter scaled to extract the distance. The method is tested by comparing the distances obtained to those estimated from very long baseline interferometry or Gaia parallax measurements, yielding a strong correlation in both cases. Additional templates are formed by constructing a source sample likely to be close to the Galactic center, and thus with a common, typical distance for calibration of the templates. These first results provide statistical distance estimates to a set of almost 15,000 Milky Way AGB stars belonging to the Bulge Asymmetries and Dynamical Evolution (BAaDE) survey, with typical distance errors of ±35%. With these statistical distances, a map of the intermediate-age population of stars traced by AGBs is formed, and a clear bar structure can be discerned, consistent with the previously reported inclination angle of 30° to the GC–Sun direction vector. These results motivate deeper studies of the AGB population to tease out the intermediate-age stellar distribution throughout the Galaxy, as well as determining statistical properties of the AGB population luminosity and mass-loss-rate distributions.
79 ASTRONOMY AND ASTROPHYSICS↗
Absolute spectral energy distribution of quasi- stellar objects from 0.3 to 2.2 microns
Quasi-stellar objects absolute spectral energy distribution, considering electron temperature and photon density
Becklin, E. E.↗
Spectral energy distributions of active galactic nuclei between 0.1 and 100 microns
The 0.1-100-micron line-free spectral energy distributions of 29 AGN are characterized by fitting simple models to data from IRAS and IUE observations and ground-based NIR and optical spectrophotometry. The data are presented in tables and graphs and discussed in detail. It is found that nuclear dust does not play a major role in most of the Seyfert 1 galaxies and QSOs, which can be described by a model with four spectral components.
Edelson, R. A.↗
Spectral Energy Distribution and Bolometric Luminosity of the Cool Brown Dwarf Gliese 229B
Infrared broadband photometry of the cool brown dwarf Gliese 229B extending in wavelength from 0.8 to 10.5 micron is reported. These results are derived from both new data and reanalyzed, previously published data. Existing spectral data reported have been rereduced and recalibrated. The close proximity of the bright Gliese 229A to the dim Gliese 229B required the use of special techniques for the observations and also for the data analysis. We describe these procedures in detail. The observed luminosity between 0.8 and 10.5 micron is (4.9 +/- 0.6) x 10(exp -6) solar luminosity. The observed spectral energy distribution is in overall agreement with a dust-free model spectrum by Tsuji et al. for T(eff) approx. equal to 900 K. If this model is used to derive the bolometric correction, the best estimate of the bolometric luminosity is 6.4 x 10(exp -6) solar luminosity and 50% of this luminosity ties between 1 and 2.5 microns. Our best estimate of the effective temperature is 900 K. From the observed near-infrared spectrum and the spectral energy distribution, the brightness temperatures (T(sub B) are estimated. The highest, T(sub B) = 1640 K, is seen at the peak of the J band spectrum, while the lowest, T(sub B) is less than or equal to 600 K, is at 3.4 microns, which corresponds to the location of the fundamental methane band.
Matthews, K.↗
The Spectral Energy Distribution of Fermi Bright Blazars
We have conducted a detailed investigation of the broadband spectral properties of the gamma-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi gamma-ray spectra with Swift, radio, infra-red, optical, and other hard X-ray /gamma-ray data, collected within 3 months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous spectral energy distributions (SED) for 48 LBAS blazars. The SED of these gamma-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual log v-log v Fv representation, the typical broadband spectral signatures normally attributed to a combination of low-energy synchrotron radiation followed by inverse Compton emission of one or more components. We have used these SED to characterize the peak intensity of both the low- and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broadband colors (i.e., the radio to optical, alpha(sub ro) , and optical to X-ray, alpha(sub ox), spectral slopes) and from the gamma-ray spectral index. Our data show that the synchrotron peak frequency (v(sup S) (sub peak)) is positioned between 10(exp 12.5) and 10(exp 14) Hz in broad-lined flat spectrum radio quasars (FSRQs) and between 10(exp 13) and 10(exp 17) Hz in featureless BL Lacertae objects. We find that the gamma-ray spectral slope is strongly correlated with the synchrotron peak energy and with the X-ray spectral index, as expected at first order in synchrotron-inverse Compton scenarios. However, simple homogeneous, one-zone, synchrotron self-Compton (SSC) models cannot explain most of our SED, especially in the case of FSRQs and low energy peaked (LBL) BL Lacs. More complex models involving external Compton radiation or multiple SSC components are required to reproduce the overall SED and the observed spectral variability. While more than 50% of known radio bright high energy peaked (HBL) BL Lacs are detected in the LBAS sample, only less than 13% of known bright FSRQs and LBL BL Lacs are included. This suggests that the latter sources, as a class, may be much fainter gamma-ray emitters than LBAS blazars, and could in fact radiate close to the expectations of simple SSC models. We categorized all our sources according to a new physical classification scheme based on the generally accepted paradigm for Active Galactic Nuclei and on the results of this SED study. Since the LAT detector is more sensitive to flat spectrum gamma-ray sources, the correlation between v(sup S) (sub peak) and gamma-ray spectral index strongly favors the detection of high energy peaked blazars, thus explaining the Fermi overabundance of this type of sources compared to radio and EGRET samples. This selection effect is similar to that experienced in the soft X-ray band where HBL BL Lacs are the dominant type of blazars.
Abdo, A. A.↗