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Modeling of Possible Plume Mechanisms on Europa
Wurz, Peter; Vorburger, Audrey
Plumes spewing water high above Europa's surface have been inferred from several observation campaigns in the past decade. Whereas the occasional existence of plumes on Europa has thus been confirmed, the origin of the plumes remains uncertain. Most notably, it is still unclear whether the inferred plumes are of oceanic origin, possibly containing…
Convection and rotation boosted prescription of magnetic braking: application to the formation of extremely low-mass white dwarfs
Kepler, S. O.; Soethe, L. T. T.
Extremely low-mass white dwarfs (ELM WDs) are the result of binary evolution in which a low-mass donor star is stripped by its companion leaving behind a helium-core white dwarf (WD). We explore the formation of ELM WDs in binary systems considering the Convection And Rotation Boosted magnetic braking treatment. Our evolutionary sequences were cal…
A Deep Polarimetric Study of the Asymmetrical Debris Disk HD 106906
MacGregor, Meredith A.; Weinberger, Alycia J.; Debes, John H. +16 more
Located in the Lower Centaurus Crux group, HD 106906 is a young, binary stellar system. This system is unique among discovered systems in that it contains an asymmetrical debris disk, as well as an 11 MJup planet companion, at a separation of ~735 au. Only a handful of other systems are known to contain both a disk and a directly imaged…
Toward the true number of flaring giant stars in the Kepler field. Are their flaring specialities associated with their being giant stars?
Pál, A.; Günther, M. N.; Oláh, K. +4 more
Aims: We aim to give a reliable estimate of the number of flaring giant stars in the Kepler field. By analyzing the flaring activity of these stars, we explored their flare statistics and the released flare energies. The role of oscillation in suppressing magnetic activity was also investigated. We searched for flaring specialities that may b…
Competitive X-Ray and Optical Cooling in the Collisionless Shocks of WR 140
Corcoran, M. F.; Russell, C. M. P.; Hamaguchi, K. +9 more
The long-period, highly eccentric Wolf-Rayet star binary system WR 140 has exceptionally well-determined orbital and stellar parameters. Bright, variable X-ray emission is generated in shocks produced by the collision of the winds of the WC7pd+O5.5fc component stars. We discuss the variations in the context of the colliding-wind model using broadb…
Self-organized Criticality in Stellar Flares
Güdel, Manuel; Aschwanden, Markus J.
Power-law size distributions are the hallmarks of nonlinear energy dissipation processes governed by self-organized criticality (SOC). Here we analyze 75 data sets of stellar flare size distributions, mostly obtained from the Extreme-Ultraviolet Explorer and the Kepler mission. We aim to answer the following questions for size distributions of ste…
The Search for Binary Supermassive Black Holes among Quasars with Offset Broad Lines Using the Very Long Baseline Array
Eracleous, Michael; Lazio, T. Joseph W.; Breiding, Peter +4 more
In several previous studies, quasars exhibiting broad emission lines with ≳1000 km s-1 velocity offsets with respect to the host galaxy rest frame have been discovered. One leading hypothesis for the origin of these velocity-offset broad lines is the dynamics of a binary supermassive black hole (SMBH). We present high-resolution radio i…
X-Ray Spectroscopy of the Highly Magnetized Pulsar PSR J1846-0258, Its Wind Nebula, and Hosting Supernova Remnant Kes 75
Gotthelf, E. V.; Safi-Harb, S.; Straal, S. M. +1 more
We present broadband X-ray spectroscopy of the energetic components that make up the supernova remnant (SNR) Kesteven 75 using concurrent 2017 August 17-20 XMM-Newton and NuSTAR observations, during which the pulsar PSR J1846-0258 is found to be in the quiescent state. The young remnant hosts a bright pulsar wind nebula powered by the highly energ…
The HARPS search for southern extra-solar planets. XLVI. 12 super-Earths around the solar type stars HD 39194, HD 93385, HD 96700, HD 154088, and HD 189567
Alonso, R.; Bouchy, F.; Deleuil, M. +23 more
Context. We present precise radial-velocity measurements of five solar-type stars observed with the HARPS Echelle spectrograph mounted on the 3.6-m telescope in La Silla (ESO, Chile). With a time span of more than 10 yr and a fairly dense sampling, the survey is sensitive to low mass planets down to super-Earths on orbital periods up to 100 days. …
Long-term X-ray observations of seyfert 1 galaxy ark 120: on the origin of soft-excess
Chatterjee, Arka; Nandi, Prantik; Chakrabarti, Sandip K. +1 more
We present the long-term X-ray spectral and temporal analysis of a 'bare-type AGN' Ark 120. We consider the observations from XMM-Newton, Suzaku, Swift, and NuSTAR from 2003 to 2018. The spectral properties of this source are studied using various phenomenological and physical models present in the literature. We report (a) the variations of sever…