Search Publications
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…
Lyman Continuum Emission Escaping from Luminous Green Pea Galaxies at z = 0.5
Malkan, Matthew A.; Malkan, Brian K.
Compact starburst galaxies are thought to include many or most of the galaxies from which substantial Lyman continuum emission can escape into the intergalactic medium. Li & Malkan used Sloan Digital Sky Survey photometry to find a population of such starburst galaxies at z ∼ 0.5. They were discovered by their extremely strong [O III] λλ4959+5…
Orbital and physical parameters of eclipsing binaries from the ASAS catalogue - XII. A sample of systems with K2 photometry
Kambe, E.; Maehara, H.; Espinoza, N. +10 more
We present results of the analysis of light and radial velocity (RV) curves of eight detached eclipsing binaries observed by the All-Sky Automated Survey, which we have followed up with high-resolution spectroscopy, and were later observed by the Keplersatellite as part of the K2mission. The RV measurements came from spectra obtained with OAO-188/…
Physical and geometrical parameters of CVBS XIV: the two nearby systems HIP 19206 and HIP 84425
Mardini, Mohammad K.; Al-Wardat, Mashhoor A.; Hussein, Abdallah M. +6 more
Data release 2 (DR2) from the Gaia mission was of great help in precise determination of fundamental parameters of Close Visual Binary and Multiple Systems (CVBMSs), especially masses of their components, which are crucial parameters in understanding formation and evolution of stars and galaxies. This article presents the complete set of fundament…
Solar surges related to UV bursts. Characterization through k-means, inversions, and density diagnostics
Guglielmino, S. L.; Sainz Dalda, A.; Nóbrega-Siverio, D.
Context. Surges are cool and dense ejections typically observed in chromospheric lines and closely related to other solar phenomena such as UV bursts or coronal jets. Even though surges have been observed for decades now, questions regarding their fundamental physical properties such as temperature and density, as well as their impact on upper lay…