Search Publications
The Nature of the Broadband X-Ray Variability in the Dwarf Seyfert Galaxy NGC 4395
Kaastra, J. S.; Stern, D.; Brandt, W. N. +14 more
We present a flux-resolved X-ray analysis of the dwarf Seyfert 1.8 galaxy NGC 4395, based on three archival XMM-Newton and one archival NuSTAR observations. The source is known to harbor a low-mass black hole (∼ {10}4{--}{{a}} {few} × {10}5 {M}⊙ ) and shows strong variability in the full X-ray range during these ob…
The Hubble Catalog of Variables (HCV)
Hatzidimitriou, D.; Rest, A.; Georgantopoulos, I. +33 more
Aims: Over its lifetime and despite not being a survey telescope, the Hubble Space Telescope (HST) has obtained multi-epoch observations by multiple, diverse observing programs, providing the opportunity for a comprehensive variability search aiming to uncover new variables. We have therefore undertaken the task of creating a catalog of varia…
Probing Clumpy Wind Accretion in IGR J18027-2016 with XMM-Newton
Paul, Biswajit; Ferrigno, Carlo; Pradhan, Pragati +2 more
Supergiant X-ray binaries usually comprise a neutron star accreting from the wind of an OB supergiant companion. They are classified as classical systems and supergiant fast X-ray transients (SFXTs). The different behavior of these subclasses of sources in X-rays, with SFXTs displaying much more pronounced variability, is usually (at least) partly…
Pronounced morphological changes in a southern active zone on comet 67P/Churyumov-Gerasimenko
Lamy, P. L.; Lara, L. M.; Bertaux, J. -L. +30 more
A smooth deposit in the southern Khonsu region has been seen in ESA/Rosetta observations as active during the second half of 2015, when the southern summer coincided with the perihelion passage of 67P/Churyumov-Gerasimenko (67P). Image color sequences acquired by the OSIRIS instrument in the period of January 2015 to July 2016, pre- and post-perih…
Excess H, Suppressed He, and the Abundances of Elements in Solar Energetic Particles
Reames, Donald V.
Recent studies of the abundances of H and He relative to those of heavier ions in solar energetic particle (SEP) events suggest new features in the underlying physics. Impulsive SEP events, defined by uniquely large enhancements of Fe/O, emerge from magnetic reconnection in solar jets. In small, "pure," shock-free, impulsive SEP events, protons wi…
Confronting expansion distances of planetary nebulae with Gaia DR2 measurements
Steffen, M.; Schönberner, D.
Context. Individual distances to planetary nebulae are of the utmost relevance for our understanding of post-asymptotic giant-branch evolution because they allow a precise determination of stellar and nebular properties. Also, objects with individual distances serve as calibrators for the so-called statistical distances based on secondary nebular …
Distribution of red clump stars does not support the X-shaped Galactic bulge
López-Corredoira, M.; Lee, Y. -W.; Garzón, F. +1 more
Context. Claims of an X-shaped Galactic bulge were based on the assumption of red clump stars as standard candles in some lines of sight crossing the off-plane bulge. However, some doubts have been cast on whether the two peaks in star counts along the line of sight really represent a double peak in the density distribution, or whether there is so…
Re-reduction of CCD astrometric observations of Neptunian satellites in 2006-2007 based on Gaia DR2 and comparison with ephemerides
Cheng, X.; Yan, D.; Qiao, R. C. +3 more
Based on the newly released Gaia DR2 star catalogue, the CCD images of Neptunian satellites taken by the telescopes at Xinglong Observatory of National Astronomical Observatory in 2006-2007 were re-reduced. A total of 174 satellite positions were derived, including 34 new observed positions of Triton, 28 new and 112 updated observed positions of N…
A spectral synergy method to retrieve martian water vapor column-abundance and vertical distribution applied to Mars Express SPICAM and PFS nadir measurements
Montmessin, F.; Ferron, S.
Up to now, all attempts to retrieve martian water vapor from nadir observations have focused their analysis on a single spectral domain and comparison between the results of various experiments showed the difficulty to reconcile the water vapor datasets together. Inspired by a methodology recently developed for the analysis of Earth observations, …
Hierarchical Bayesian model to infer PL(Z) relations using Gaia parallaxes
Sarro, L. M.; Clementini, G.; Garofalo, A. +2 more
In a recent study we analysed period-luminosity-metallicity (PLZ) relations for RR Lyrae stars using the Gaia Data Release 2 (DR2) parallaxes. It built on a previous work that was based on the first Gaia Data Release (DR1), and also included period-luminosity (PL) relations for Cepheids and RR Lyrae stars. The method used to infer the relations fr…