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The cosmic microwave background Cold Spot anomaly: the impact of sky masking and the expected contribution from the integrated Sachs-Wolfe effect
Lahav, Ofer; Benoit-Lévy, Aurélien; Naidoo, Krishna
We re-analyse the cosmic microwave background (CMB) Cold Spot (CS) anomaly with particular focus on understanding the bias a mask (contaminated by Galactic and point sources) may introduce. We measure the coldest spot, found by applying the Spherical Mexican Hat Wavelet transform on 100 000 cut-sky (masked) and full-sky CMB simulated maps. The CS …
A mechanism for comet surface collapse as observed by Rosetta on 67P/Churyumov-Gerasimenko
Sierks, H.; Prialnik, D.
We explore a possible mechanism that may explain sudden depressions of surface areas on a comet nucleus, as suggested by observations of the Rosetta mission on comet 67P/Churyumov-Gerasimenko (hereafter, 67P/C-G). Assuming the area is covered by a thin, compact dust layer of low permeability to gas flow compared to deeper, porous layers, gas can a…
Energy-dependent variability of the bare Seyfert 1 galaxy Ark 120
Dewangan, Gulab C.; McHardy, I. M.; Mallick, Labani +1 more
We present results from a detailed spectral-timing analysis of a long ∼486 ks XMM-Newton observation of the bare Seyfert 1 galaxy Ark 120 which showed alternating diminution and increment in the 0.3-10 keV X-ray flux over four consecutive orbits in 2014. We study the energy-dependent variability of Ark 120 through broad-band X-ray spectroscopy, fr…
SOFIA-EXES Mid-IR Observations of [Fe II] Emission from the Extended Atmosphere of Betelgeuse
Ryde, N.; Greathouse, T. K.; Guinan, E. F. +5 more
We present a NASA-DLR SOFIA-Echelon Cross Echelle Spectrograph (EXES) and NASA Infrared Telescope Facility-Texas Echelon Cross Echelle Spectrograph (TEXES) mid-IR R≃ {{50,000}} spectral study of forbidden Fe II transitions in the early-type M supergiants, Betelgeuse (α Ori: M2 Iab) and Antares (α Sco: M1 Iab + B3 V). With EXES, we spectrally resol…
X-rays from Green Pea analogues
Kaaret, P.; Brorby, M.
X-ray observations of two metal-deficient luminous compact galaxies (LCG; SHOC 486 and SDSS J084220.94+115000.2) with properties similar to the so-called Green Pea galaxies were obtained using the Chandra X-ray Observatory. Green Pea galaxies are relatively small, compact (a few kpc across) galaxies that get their green colour from strong [O III] …
Stability of the interstellar hydrogen inflow longitude from 20 years of SOHO/SWAN observations
Schmidt, W.; Bertaux, J. -L.; Lallement, R. +3 more
Aims: A recent debate on the decade-long stability of the interstellar He flow vector, and in particular the flow longitude, has prompted us to check for any variability in the interstellar H flow vector as observed by the SWAN instrument on board SOHO.
Methods: We used a simple model-independent method to determine the interstellar H fl…
Quantification of the total ion transport in the near-Earth plasma sheet
Karlsson, Tomas; Nilsson, Hans; Slapak, Rikard +4 more
Recent studies strongly suggest that a majority of the observed O+ cusp outflows will eventually escape into the solar wind, rather than be transported to the plasma sheet. Therefore, an investigation of plasma sheet flows will add to these studies and give a more complete picture of magnetospheric ion dynamics. Specifically, it will pr…
Optimal Stellar Photometry for Multi-conjugate Adaptive Optics Systems Using Science-based Metrics
Massari, D.; Stetson, P. B.; Bono, G. +5 more
We present a detailed discussion of how to obtain precise stellar photometry in crowded fields using images from multi-conjugate adaptive optics (MCAO) systems, with the intent of informing the scientific development of this key technology for the Extremely Large Telescopes. We use deep J and K s exposures of NGC 1851 taken with the Gem…
XMM-Newton observation of the supernova remnant Kes 78 (G32.8-0.1): Evidence of shock-cloud interaction
Chen, Y.; Miceli, M.; Bocchino, F. +4 more
Context. The Galactic supernova remnant Kes 78 is surrounded by dense molecular clouds, whose projected position overlaps with the extended HESS γ-ray source HESS J1852-000. The X-ray emission from the remnant has recently been revealed by Suzaku observations, which have shown indications for a hard X-ray component in the spectra that might be ass…
Search for active lava flows with VIRTIS on Venus Express
Drossart, P.; Piccioni, G.; Smrekar, S. +3 more
The Visible Infrared Thermal Imaging Spectrometer (VIRTIS) instrument on Venus Express observed thermal emission from the surface of Venus at 1 µm wavelength and thus would have detected sufficiently bright incandescent lava flows. No eruptions were detected in the observations between April 2006 and October 2008, covering an area equivalent…