Search Publications
Pulsation in Intermediate-Mass Stars
Balona, Luis A.
A new perspective of pulsation in stars within the δ Scuti instability strip has recently emerged as a result of Kepler observations. The majority of stars within the instability strip do not pulsate and practically all δ Scuti stars contain low frequencies. Because γ Doradus stars co-exist with δ Sct stars in the same region of the instability st…
A Hubble Diagram for Quasars
Risaliti, Guido; Lusso, Elisabeta; Bisogni, Susanna
The cosmological model is at present not tested between the redshift of the farthest observed supernovae (z 1.4) and that of the Cosmic Microwave Background (z 1,100). Here we introduce a new method to measure the cosmological parameters: we show that quasars can be used as “standard candles” by employing the non-linear relation between their intr…
The MEXSAS2 Sample and the Ensemble X-ray Variability of Quasars
Serafinelli, Roberto; Middei, Riccardo; Chiaraluce, Elia +1 more
We present the second Multi-Epoch X-ray Serendipitous AGN Sample (MEXSAS2), extracted from the 6th release of the XMM Serendipitous Source Catalogue release (XMMSSC-DR6), cross-matched with Sloan Digital Sky Survey quasar catalogues DR7Q and DR12Q. Our sample also includes the available measurements for masses, bolometric luminosities, and Eddingt…
Catalog of 3<z<5.5 quasar candidates selected among XMM-Newton sources and its spectroscopic verification
Khorunzhev, Georgii; Sazonov, Sergey; Burenin, Rodion +1 more
We have compiled a catalog of 903 quasar candidates (including known quasars) at 3<z<5.5 selected among X-ray sources from the XMM-Newton serendipitous survey (3XMM-DR4 catalog). We used photometric SDSS, 2MASS and WISE data to select the objects. The surface number density of objects in our sample exceeds that in the SDSS spectroscopic quas…
Gaia space mission and quasars
Zwitter, Tomaž
Quasars are often considered to be point-like objects. This is largely true and allows for an excellent alignment of the optical positional reference frame of the ongoing ESA mission Gaia with the International Celestial Reference Frame. But presence of optical jets in quasars can cause shifts of the optical photo-centres at levels detectable by G…
Multi-frequency databases for AGN investigation - Results and perspectives
La Mura, Giovanni; Berton, Marco; Chen, Sina +5 more
Active Galactic Nuclei (AGNs) are characterized by emission of radiation over more than 10 orders of magnitude in frequency. Therefore, the execution of extensive surveys of the sky, with different types of detectors, is providing the attractive possibility to identify and to investigate the properties of AGNs on very large statistical samples. Th…
Evidence for a Magnetic Flux Rope in Observations of a Solar Prominence-Cavity System
Reeves, Katharine K.; Su, Yingna; Jibben, Patricia R.
Lifecycle of a large-scale polar coronal pseudostreamer/cavity system
Auchère, Frédéric; Rachmeler, Laurel; Seaton, Daniel +1 more
We report on an exceptional large-scale coronal pseudostreamer/cavity system in the southern polar region of the solar corona that was visible for approximately a year starting in February 2014. It is unusual to see such a large closed-field structure embedded within the open polar coronal hole. We investigate this structure to document its format…
Connecting VLBI and Gaia celestial reference frames
Malkin, Zinovy
The current state of the link problem between radio and optical celestial reference frames is considered. The main objectives of the investigations in this direction during the next few years are the preparation of a comparison and the mutual orientation and rotation between the optical Gaia Celestial Reference Frame (GCRF) and the 3rd generation …
A survey of solar wind conditions at 5 AU: A tool for interpreting solar wind-magnetosphere interactions at Jupiter
Bagenal, Fran; Ebert, Robert; McComas, David +1 more
We examine Ulysses solar wind and interplanetary magnetic field (IMF) observations at 5 AU for two ~13 month intervals during the rising and declining phases of solar cycle 23 and the predicted response of the Jovian magnetosphere during these times. The declining phase solar wind, composed primarily of corotating interaction regions and high-spee…