Search Publications
Robust identification of active galactic nuclei through HST optical variability in GOODS-S: comparison with the X-ray and mid-IR-selected samples★
Hatzidimitriou, D.; Georgantopoulos, I.; Gavras, P. +9 more
Identifying active galactic nuclei (AGNs) through their X-ray emission is efficient, but necessarily biased against X-ray-faint objects. We aim to characterize this bias by comparing X-ray-selected AGNs to the ones identified through optical variability and mid-infrared (mid-IR) colours. We present a catalogue of AGNs selected through optical vari…
The Galactic Disk Phase Spirals at Different Galactic Positions Revealed by Gaia and LAMOST Data
Wang, H. -F.; Huang, Y.; Chen, B. -Q. +9 more
We have investigated the distributions of stellar azimuthal and radial velocity components V Φ and V R in the vertical position-velocity plane Z-V Z across the Galactic disk of 6.34 ≲ R ≲ 12.34 kpc and | {{Φ }}| ≲ 7\buildrel{\circ}\over{.} 5 using a Gaia and Gaia-LAMOST sample of stars. As found in previous wor…
Numerical integration of stochastic differential equations: A parallel cosmic ray modulation implementation on Africa's fastest computer
Moeketsi, D. M.; Engelbrecht, N. E.; Strauss, R. D. +2 more
Three-dimensional studies of the transport and modulation of cosmic ray particles in turbulent astrospheres require large-scale simulations using specialized scientific codes. Essentially, a multi-dimensional Fokker-Planck type equation (a parabolic diffusion equation) must be integrated numerically. One such approach is to convert the relevant tr…
Indications of non-conservative mass transfer in AMXPs
Sanna, A.; Papitto, A.; Di Salvo, T. +7 more
Context. Since the discovery of the first accreting millisecond X-ray pulsar (AMXP) SAX J1808.4-3658 in 1998, the family of these sources has kept growing. Currently, it has 22 members. All AMXPs are transients with usually very long quiescence periods, implying that the mass accretion rate in these systems is quite low and not constant. Moreover,…
Understanding Cassini RPWS Antenna Signals Triggered by Dust Impacts
Hospodarsky, G. B.; Kurth, W. S.; Zaslavsky, A. +11 more
Electric field antennas are capable of detecting dust impacts in different space environment. We analyze the dust impact signals detected by the Cassini Radio and Plasma Wave Science instrument at different locations around Saturn and compare them with dust impact signals simulated in laboratory conditions and numerically. The spacecraft potential…
Gliese 49: activity evolution and detection of a super-Earth. A HADES and CARMENES collaboration
Schmitt, J. H. M. M.; Rebolo, R.; Amado, P. J. +40 more
Context. Small planets around low-mass stars often show orbital periods in a range that corresponds to the temperate zones of their host stars which are therefore of prime interest for planet searches. Surface phenomena such as spots and faculae create periodic signals in radial velocities and in observational activity tracers in the same range, s…
The tilt of the local velocity ellipsoid as seen by Gaia
Evans, N. W.; Belokurov, V.; Schönrich, R. +1 more
The Gaia Radial Velocity Spectrometer (RVS) provides a sample of 7224 631 stars with full six-dimensional phase space information. Bayesian distances of these stars are available from the catalogue of Schönrich, McMillan & Eyer. We exploit this to map out the behaviour of the velocity ellipsoid within 5 kpc of the Sun. We find that the tilt of…
The First Metallicity Study of M83 Using the Integrated UV Light of Star Clusters
Skillman, Evan D.; Hernandez, Svea; Aloisi, Alessandra +8 more
Stellar populations are powerful tools for investigating the evolution of extragalactic environments. We present the first UV integrated-light spectroscopic observations for 15 young star clusters in the starburst M83 with a special focus on metallicity measurements. The data were obtained with the Cosmic Origins Spectrograph on board the Hubble S…
The host galaxies of FeLoBAL quasars at z ∼ 0.9 are not dominated by recent major mergers
Villforth, C.; Hamann, F.; Hamilton, T. +4 more
Theoretical models have suggested an evolutionary model for quasars, in which most of luminous quasars are triggered by major mergers. It is also postulated that reddening as well as powerful outflows indicate an early phase of activity, close to the merger event. We test this model on a sample of quasars with powerful low-ionization outflows seen…
The SOFIA Massive (SOMA) Star Formation Survey. II. High Luminosity Protostars
Tanaka, Kei E. I.; Zhang, Yichen; Tan, Jonathan C. +6 more
We present multiwavelength images observed with SOFIA-FORCAST from ∼10 to 40 µm of seven high luminosity massive protostars, as part of the SOFIA Massive Star Formation Survey. Source morphologies at these wavelengths appear to be influenced by outflow cavities and extinction from dense gas surrounding the protostars. Using these images, we …