Search Publications
Pointing Chandra toward the Extreme Ultraviolet Fluxes of Very Low Mass Stars
Drake, Jeremy J.; Kashyap, Vinay L.; Wolk, Scott J. +1 more
The X-ray and EUV emission of stars plays a key role in the loss and evolution of the atmospheres of their planets. The coronae of dwarf stars later than M6 appear to behave differently from those of earlier spectral types and are more X-ray dim and radio bright. Too faint to have been observed by the Extreme Ultraviolet Explorer, their EUV behavi…
Testing the Lamp-post and Wind Reverberation Models with XMM-Newton Observations of NGC 5506
Zoghbi, Abderahmen; Kalli, Sihem; Miller, Jon M. +1 more
The lamp-post geometry is often used to model X-ray data of accreting black holes. Despite its simple assumptions, it has proven to be powerful in inferring fundamental black hole properties such as the spin. Early results of X-ray reverberations showed support for such a simple picture, though wind reverberation models have also been shown to exp…
Evidence for periodic accretion-ejection in LS I +61°303
Migliari, S.; Readhead, A. C. S.; Kraus, A. +7 more
The stellar binary system LS I +61°303, composed of a compact object in an eccentric orbit around a B0 Ve star, emits from radio up to γ-ray energies. The orbital modulation of radio spectral index, X-ray, and GeV γ-ray data suggests the presence of two peaks. This two-peaked profile is in line with the accretion theory predicting two accretion-ej…
The giant outburst of 4U 0115+634 in 2011 with Suzaku and RXTE. Minimizing cyclotron line biases
Rothschild, Richard E.; Fürst, Felix; Grinberg, Victoria +19 more
We present an analysis of X-ray spectra of the high-mass X-ray binary 4U 0115+634 as observed with Suzaku and RXTE in 2011 July, during the fading phase of a giant X-ray outburst. We used a continuum model consisting of an absorbed cutoff power law and an ad hoc Gaussian emission feature centered around 8.5 keV, which we attribute to cyclotron emi…
X-ray reverberation lags from the 1.5 Seyfert galaxy NGC 5273
McHardy, I.; Vincentelli, F. M.; Ingram, A. +2 more
We present the results of X-ray spectral-timing analysis of a 90 ks XMM-Newton observation of the nearby, broad-line, early-type AGN NGC5273. The X-ray spectrum revealed the clear presence of a reflection component at high energies, with a clear signature of a narrow iron line at 6.4 keV, consistent with distant reflection. Applying a relativistic…
Differential Rotation of the Halo Traced by K-giant Stars
Tian, Hao; Xu, Yan; Yang, Chengqun +4 more
We use K-giant stars selected from the LAMOST DR5 to study the variation of the rotational velocity of the Galactic halo at different space positions. Modeling the rotational velocity distribution with both the halo and disk components, we find that the rotational velocity of the halo population decreases almost linearly with increasing vertical d…
KELT-17: a chemically peculiar Am star and a hot-Jupiter planet
González, J. F.; Jofré, E.; Jaque Arancibia, M. +6 more
Context. There is very little information to be found in the literature regarding the detection of planets orbiting chemically peculiar stars.
Aims: Our aim is to determine the detailed chemical composition of the remarkable planet host star KELT-17. This object hosts a hot-Jupiter planet with 1.31 MJup detected by transits, and it…
Study of the departures from LTE in the unevolved stars infrared spectra
Bonifacio, P.; Caffau, E.; Oliva, E. +2 more
We present a study of departures from Local Thermodynamic Equilibrium (LTE) in the formation of infrared (IR) lines of Na I, Mg I, Al I, S I, K I, and Sr II in unevolved stars of spectral types F, G, K and metallicities around the solar metallicity. The purpose of this investigation is to identify lines of these species that can be safely treated …
Electron Acceleration in a Magnetotail Reconnection Outflow Region Using Magnetospheric MultiScale Data
Khotyaintsev, Yuri V.; Graham, Daniel B.; Vaivads, Andris +3 more
We study Magnetospheric MultiScale observations in the outflow region of magnetotail reconnection. We estimate the power density converted via the three fundamental electron acceleration mechanisms: Fermi, betatron, and parallel electric fields. The dominant mechanism, both on average and the peak values, is Fermi acceleration with a peak power de…
Neglected X-ray discovered polars. II. The peculiar eclipsing binary HY Eridani
Burwitz, V.; Beuermann, K.; Schwope, A. +2 more
We report on the X-ray observations of the eclipsing polar HY Eri (RX J0501-0359), along with its photometric, spectrophotometric, and spectropolarimetric optical variations, collected over 30 years. With an orbital period of 2.855 h,