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The Hubble Space Telescope's Near-UV and Optical Transmission Spectrum of Earth as an Exoplanet
Roberge, Aki; France, Kevin; Youngblood, Allison +3 more
We observed the 2019 January total lunar eclipse with the Hubble Space Telescope's STIS spectrograph to obtain the first near-UV (1700-3200 Å) observation of Earth as a transiting exoplanet. The observatories and instruments that will be able to perform transmission spectroscopy of exo-Earths are beginning to be planned, and characterizing the tra…
Changes in the Period of the Population II Cepheid CC Lyr
Berdnikov, L. N.; Pastukhova, E. N.; Yacob, A. M.
The reduction of all the available photometry for the Cepheid CC Lyr has allowed its $O-C$ diagram spanning a time interval of 124 years to be constructed. The data obtained provide evidence for the existence of large random fluctuations in the period ($\varepsilon/P≈ 0.046$). A formal fitting of the $O-C$ residuals has made it possible to estimat…
Softening of the Metagalactic Ionizing Background from Internal He II Absorption in Quasars
Shull, J. Michael; Danforth, Charles W.
Quasars and other active galactic nuclei (AGN) are significant contributors to the metagalactic ionizing background at redshifts z < 3. Recent Hubble Space Telescope (HST)/Cosmic Origins Spectrograph (COS) composite spectra of AGN find a harder flux distribution in the Lyman continuum, ${F}_{\nu }\propto {\nu }^{-{\alpha }_{s}}$ (αs …
The evolutionary status of chemically peculiar eclipsing binary star DV Boo
Aliçavuş, F.; Kahraman Aliçavuş, Filiz
Eclipsing binary systems are unique stellar objects to examine and understand stellar evolution and formation. Thanks to these systems, the fundamental stellar parameters (mass, radius) can be obtained very precisely. The existence of metallic-line (Am) stars in binaries is noticeably common. However, the known number of Am stars in eclipsing bina…
Multi-wavelength, spatially resolved modelling of HD 48682's debris disc
Marshall, J. P.; Horner, J.; Marsden, S. C. +1 more
Asteroids and comets (planetesimals) are created in gas- and dust-rich protoplanetary discs. The presence of these planetesimals around main-sequence stars is usually inferred from the detection of excess continuum emission at infrared wavelengths from dust grains produced by destructive processes within these discs. Modelling of the disc structur…
Searching for Nuclear Obscuration in the Infrared Spectra of Nearby FR I Radio Galaxies
O'Dea, C. P.; Baum, S. A.; Gallimore, J. F. +2 more
How do active galactic nuclei with low optical luminosities produce powerful radio emission? Recent studies of active galactic nuclei with moderate radio and low optical luminosities (Fanaroff & Riley class I, FR I) searching for broad nuclear emission lines in polarized light, as predicted by some active galactic nucleus unification models, h…
Nondetection of Radio Emissions From Titan Lightning by Cassini RPWS
Gurnett, D. A.; Kurth, W. S.; Fischer, G. +1 more
The Saturn-orbiting Cassini spacecraft completed 126 close Titan flybys from 2004 until 2017. During almost all of them the Cassini Radio and Plasma Wave Science (RPWS) instrument was turned on to search for radio emissions attributed to Titan lightning. Here we report about their nondetection after close inspection of all Titan flybys throughout …
Extragalactic X-ray discrete sources
Zadorozhna L. V.; Tugay A. V.; Shevchenko S. Yu.
Extra-galactic X-ray research with the launch of XMM-Newton has become the forefront of X-ray astronomy. X-ray sources outside our galaxy are the other galaxies - normal galaxies, radio galaxies, quasars, blazars, Seyfert galaxies, as well as extended sources in galaxy clusters - the glow of cluster's halo. X-ray space observatory's equipment reac…
Low optical polarization at the core of the optically thin jet of M87
Merloni, A.; Prieto, M. A.; Acosta-Pulido, J. A. +2 more
We study the optical linear and circular polarization in the optically thin regime of the core and jet of M87. Observations were acquired two days before the Event Horizon Telescope (EHT) campaign in early 2017 April. A high degree (∼20 per cent) of linear polarization (Plin) is detected in the bright jet knots resolved at $\sim 10\,\ma…
Geological characterization of Chandrayaan-2 landing site in the southern high latitudes of the Moon
Harish; Bhatt, Megha; Bhardwaj, Anil +7 more
ISRO's lunar orbiter-lander-rover mission Chandryaan-2 is scheduled to be launched in the mid of 2019. In this contribution, we have carried out detailed geological characterization of the prime landing site (70.9°S, 22.8°E) of the Chandrayaan-2 lander - "Vikram". The proposed landing site is located amidst the nearside lunar highlands at high sou…