Search Publications
Positive correlation between the cyclotron line energy and luminosity in sub-critical X-ray pulsars: Doppler effect in the accretion channel
Tsygankov, Sergey S.; Mushtukov, Alexander A.; Suleimanov, Valery F. +2 more
Cyclotron resonance scattering features observed in the spectra of some X-ray pulsars show significant changes of the line centroid energy with the pulsar luminosity. Whereas for bright sources above the so-called critical luminosity, these variations are established to be connected with the appearance of the high-accretion column above the neutro…
500 days of SN 2013dy: spectra and photometry from the ultraviolet to the infrared
Fox, O. D.; Lee, W. H.; Zheng, W. +23 more
SN 2013dy is a Type Ia supernova (SN Ia) for which we have compiled an extraordinary data set spanning from 0.1 to ∼ 500 d after explosion. We present 10 epochs of ultraviolet (UV) through near-infrared (NIR) spectra with Hubble Space Telescope/Space Telescope Imaging Spectrograph, 47 epochs of optical spectra (15 of them having high resolution), …
The progenitors of the Milky Way stellar halo: big bricks favoured over little bricks.
Belokurov, V.; Deason, A. J.; Weisz, D. R.
We present a census of blue horizontal branch (BHB) and blue straggler (BS) stars belonging to dwarf galaxies and globular clusters, and compare these counts to that of the Milky Way stellar halo. We find, in agreement with earlier studies, that the ratio of BS-to-BHB stars in these satellite populations is dependent on stellar mass. Dwarf galaxie…
New light on Galactic post-asymptotic giant branch stars - I. First distance catalogue
Parker, Quentin A.; Vickers, Shane B.; Frew, David J. +1 more
We have commenced a detailed analysis of the known sample of Galactic post-asymptotic giant branch (PAGB) objects compiled in the Toruń catalogue of Szczerba et al., and present, for the first time, homogeneously derived distance determinations for the 209 likely and 87 possible catalogued PAGB stars from that compilation. Knowing distances are es…
Magnetic field-gas density relation and observational implications revisited
Panopoulou, G. V.; Pavlidou, V.; Tassis, K. +2 more
We revisit the relation between magnetic-field strength (B) and gas density (ρ) for contracting interstellar clouds and fragments (or, cores), which is central in observationally determining the dynamical importance of magnetic fields in cloud evolution and star formation. Recently, it has been claimed that a relation B ∝ ρ2/3 is statis…
Gone without a bang: an archival HST survey for disappearing massive stars
Gilmore, Gerard; Reynolds, Thomas M.; Fraser, Morgan
It has been argued that a substantial fraction of massive stars may end their lives without an optically bright supernova (SN), but rather collapse to form a black hole. Such an event would not be detected by current SN surveys, which are focused on finding bright transients. Kochanek et al. proposed a novel survey for such events, using repeated …
Sizes and shapes of young star cluster light profiles in M83
Larsen, S.; Bastian, N.; Gallagher, J. S. +6 more
We measure the radii and two-dimensional light profiles of a large sample of young, massive star clusters in M83 using archival HST/Wide Field Camera 3 (WFC3) imaging of seven adjacent fields. We use GALFIT to fit the two-dimensional light profiles of the clusters, from which we find effective (half-light) radii, core radii, and slopes of the powe…
How clustering dark energy affects matter perturbations
Mehrabi, A.; Basilakos, S.; Pace, F.
The rate of structure formation in the Universe is different in homogeneous and clustered dark energy models. The degree of dark energy clustering depends on the magnitude of its effective sound speed c2_eff and for c2_eff=0 dark energy clusters in a similar fashion to dark matter while for c2_eff=1 it stays (appro…
ALMA imaging of SDP.81 - II. A pixelated reconstruction of the CO emission lines
Andreani, P.; Rybak, M.; Vegetti, S. +2 more
We present a sub-100 pc-scale analysis of the CO molecular gas emission and kinematics of the gravitational lens system SDP.81 at redshift 3.042 using Atacama Large Millimetre/submillimetre Array (ALMA) science verification data and a visibility-plane lens reconstruction technique. We find clear evidence for an excitation-dependent structure in th…
Spitzer infrared spectrograph point source classification in the Small Magellanic Cloud
van Loon, J. Th.; Antoniou, V.; Szczerba, R. +16 more
The Magellanic Clouds are uniquely placed to study the stellar contribution to dust emission. Individual stars can be resolved in these systems even in the mid-infrared, and they are close enough to allow detection of infrared excess caused by dust. We have searched the Spitzer Space Telescope data archive for all Infrared Spectrograph (IRS) stari…