Spectral Energy Distributions Of Objects Research Articles

The intrinsic gamma-ray spectrum of TXS 0506+056: intergalactic propagation effects

ABSTRACT The recent observation of high-energy neutrinos from the 2017 flare of the blazar TXS 0506+056, together with counterparts across the whole electromagnetic spectrum, opens up new possibilities for investigating the properties of this class of objects as well as the traversed medium. Propagation effects such as the attenuation of the very-high-energy gamma-ray component by the extragalactic background light are well known, and usually taken into account when fitting spectral energy distributions of objects. Other effects such as those of intergalactic magnetic fields are, however, often neglected. In this work, we present a comprehensive study of the influence of these fields and the extragalactic background light on the determination of the intrinsic gamma-ray spectrum of this blazar.

MID-INFRARED HIGH-CONTRAST IMAGING OF HD 114174 B: AN APPARENT AGE DISCREPANCY IN A “SIRIUS-LIKE” BINARY SYSTEM

We present new observations of the faint "Sirius-like" companion discovered to orbit HD 114174. Previous attempts to image HD 114174 B at mid-infrared wavelengths using NIRC2 at Keck have resulted in a non-detection. Our new L'-band observations taken with the Large Binocular Telescope and LMIRCam recover the companion ($\Delta L$ = 10.15 $\pm$ 0.15 mag, $\rho$ = 0.675'' $\pm$ 0.016'') with a high signal-to-noise ratio (10 $\sigma$). This measurement represents the deepest L' high-contrast imaging detection at sub-arcsecond separations to date, including extrasolar planets. We confirm that HD 114174 B has near-infrared colors consistent with the interpretation of a cool white dwarf ($J-L'$ = 0.76 $\pm$ 0.19 mag, $K-L'$ = 0.64 $\pm$ 0.20). New model fits to the object's spectral energy distribution indicate a temperature $T_{\rm eff}$ = 4260 $\pm$ 360 K, surface gravity log g = 7.94 $\pm$ 0.03, a cooling age t$_{c} \approx$ 7.8 Gyr, and mass $M$ = 0.54 $\pm$ 0.01 $M_{\odot}$. We find that the cooling age given by theoretical atmospheric models do not agree with the age of HD 114174 A derived from both isochronological and gyrochronological analyses. We speculate on possible scenarios to explain the apparent age discrepancy between the primary and secondary. HD 114174 B is a nearby benchmark white dwarf that will ultimately enable a dynamical mass estimate through continued Doppler and astrometric monitoring. Efforts to characterize its physical properties in detail will test theoretical atmospheric models and improve our understanding of white dwarf evolution, cooling, and progenitor masses.

KIC 9406652: AN UNUSUAL CATACLYSMIC VARIABLE IN THEKEPLERFIELD OF VIEW

KIC 9406652 is a remarkable variable star in the Kepler field of view that shows both very rapid oscillations and long term outbursts in its light curve. We present an analysis of the light curve over quarters 1 to 15 and new spectroscopy that indicates that the object is a cataclysmic variable with an orbital period of 6.108 hours. However, an even stronger signal appears in the light curve periodogram for a shorter period of 5.753 hours, and we argue that this corresponds to the modulation of flux from the hot spot region in a tilted, precessing disk surrounding the white dwarf star. We present a preliminary orbital solution from radial velocity measurements of features from the accretion disk and the photosphere of the companion. We use a Doppler tomography algorithm to reconstruct the disk and companion spectra, and we also consider how these components contribute to the object's spectral energy distribution from ultraviolet to infrared wavelengths. This target offers us a remarkable opportunity to investigate disk processes during the high mass transfer stage of evolution in cataclysmic variables.

SIMBA's view of the ϵ Eri disk

We present the first observational confirmation for an extended circumstellar dust disk around ϵ Eri. The observations were obtained with the bolometer array SIMBA at the 15 m radio telescope SEST in Chile and measure the dust continuum at 1.2 mm. The emission, with a total flux of 21.4 mJy and a rms of 2.2 mJy/beam, is resolved to a deconvolved size of 274 which corresponds to 88 AU. No clear indication for a ring-like disk structure is seen, possibly also due to the telescope's large beam width of 24''. Models of the object's spectral energy distribution from IR to mm-wavelengths show that the emission can also be explained by a simple disk model. We further demonstrate the strong influence of noise and propose to be cautious with interpretations of the ring substructure.

The Blue Companion of 3C 65: A Star‐forming Galaxy with a Probable Redshift of 2.8

We present BVRIK images and photometry of the z = 1.175 radio galaxy 3C 65 and its extended blue companion, along with a 6 cm radio map. These data are used to test the hypotheses that the companion is scattering the continuum of a hidden active nucleus within the radio galaxy and/or is undergoing a starburst triggered by interaction with its radio plasma. However, we find that the object's spectral energy distribution (SED) is best fitted by a model of constant star formation with moderate dust extinction for a redshift of approximately 2.8, while no fit to the SED can be obtained for redshifts equal to or below that of 3C 65. The object thus appears to be part of the recently discovered population of star-forming galaxies at z ~ 3, which is also consistent with its morphology and size as revealed by Hubble Space Telescope WFPC2 images. The age of the object is not well-constrained by the model fits and could range from 0.2 to 3.5 Gyr. Our best-fitting model has an age of 1.4 Gyr, which at z ≅ 2.8 does not violate standard cosmologies.