Search Publications
Gaussian process model for the local stellar velocity field from Gaia data release 2
Widrow, Lawrence M.; Nelson, Patrick
We model the local stellar velocity field using position and velocity measurements for 4M stars from the second data release of Gaia. We determine the components of the mean or bulk velocity in $\sim 27\, 000$ spatially defined bins. Our assumption is that these quantities constitute a Gaussian process where the correlation between the bulk veloci…
Average bolometric corrections and optical to X-ray flux measurements as a function of accretion rate for X-ray binaries
Zezas, A.; Steiner, J. F.; Reig, P. +1 more
In this paper, we use an RXTE library of spectral models from 10 black hole and 9 pulsar X-ray binaries, as well as model spectra available in the literature from 13 extra-galactic ultra-luminous X-ray sources (ULXs). We compute average bolometric corrections (BC = Lband/Lbol) for our sample as a function of different accreti…
A study of the F-giant star θ Scorpii A: a post-merger rapid rotator?
Lewis, Fiona; Bailey, Jeremy; Cotton, Daniel V. +3 more
We report high-precision observations of the linear polarization of the F1III star θ Scorpii. The polarization has a wavelength dependence of the form expected for a rapid rotator, but with an amplitude several times larger than seen in otherwise similar main-sequence stars. This confirms the expectation that lower-gravity stars should have strong…
SEAGLE - III: Towards resolving the mismatch in the dark-matter fraction in early-type galaxies between simulations and observations
Schaye, Joop; Koopmans, Léon V. E.; Schaller, Matthieu +4 more
The central dark-matter fraction of galaxies is sensitive to feedback processes during galaxy formation. Strong gravitational lensing has been effective in the precise measurement of the dark-matter fraction inside massive early-type galaxies. Here, we compare the projected dark-matter fraction of early-type galaxies inferred from the SLACS (Sloan…
The massive system V375 Cassiopeia is a semidetached mass-transfer binary with a massive stellar companion
Zhang, J.; Qian, S. -B.; Liao, W. -P. +3 more
V375 Cassiopeia (V375 Cas) is an early B-type close binary with an orbital period of 1.4734273 d. Based on high-quality and continuous light curves from the Transiting Exoplanet Survey Satellite (TESS) and new low-resolution spectra, we have determined photometric solutions of the eclipsing binary using the Wilson-Devinney method. We have found th…
The fall of CSS100217: a tidal disruption-induced low state in an apparently hostless active galactic nucleus
Levan, A. J.; Cannizzaro, G.; van Velzen, S. +1 more
CSS100217 was a nuclear, rapid, and luminous flare in a narrow-line seyfert 1 galaxy, whose initial interpretation as a supernova is now debated between variability of the active galactic nucleus (AGN) and a tidal disruption event (TDE). In this paper, we present and discuss new evidence in favour of a TDE or extreme flaring episode scenario. Afte…
Predicting the black hole mass and correlations in X-ray reverberating AGNs using neural networks
Chainakun, P.; Young, A. J.; Hancock, S. +1 more
We develop neural network models to predict the black hole mass using 22 reverberating active galactic nucleus (AGN) samples in the XMM-Newton archive. The model features include the fractional excess variance (Fvar) in 2-10 keV band, Fe-K lag amplitude, 2-10 keV photon counts, and redshift. We find that the prediction accuracy of the n…
Solenoidal turbulent modes and star formation efficiency in Galactic plane molecular clouds
Rigby, Andrew J.; Eden, David J.; Rani, Raffaele +1 more
It is speculated that the high star formation efficiency observed in spiral-arm molecular clouds is linked to the prevalence of compressive (curl-free) turbulent modes, while the shear-driven solenoidal (divergence-free) modes appear to be the main cause of the low star formation efficiency that characterizes clouds in the Central Molecular Zone. …
Age-morphology dependence of the Milky Way boxy/peanut bulge seen in Mira variables
Schönrich, Ralph; Dehnen, Walter; Semczuk, Marcin +1 more
We analyse the distribution of Mira variable stars in the central region of the Milky Way. We find that with increasing period, i.e. decreasing age, the Miras shift towards negative Galactic longitudes ℓ. Comparing to a cosmological zoom simulation of a barred galaxy, we find that this shift with age can be explained by an age-morphology dependenc…
Multiwavelength study of the gravitationally lensed blazar QSO B0218+357 between 2016 and 2020
Maraschi, L.; Covino, S.; Antonelli, L. A. +207 more
We report multiwavelength observations of the gravitationally lensed blazar QSO B0218+357 in 2016-2020. Optical, X-ray, and GeV flares were detected. The contemporaneous MAGIC observations do not show significant very high energy (VHE; ≳100 GeV) gamma-ray emission. The lack of enhancement in radio emission measured by The Owens Valley Radio Observ…