Search Publications
The rise and fall of the UV upturn: z = 0.3, 0.55, and 0.7
Bremer, M. N.; De Propris, R.; Phillipps, S. +1 more
We have analysed the strength of the ultraviolet (UV) upturn in red sequence galaxies with luminosities reaching to below the L* point within four clusters at z = 0.3, 0.55, and 0.7. We find that the incidence and strength of the upturn remains constant up to z = 0.55. In comparison, the prevalence and strength of the UV upturn is significantly di…
Correlations between age, kinematics, and chemistry as seen by the RAVE survey
Grebel, Eva K.; Steinmetz, Matthias; Bland-Hawthorn, Joss +20 more
We explore the connections between stellar age, chemistry, and kinematics across a Galactocentric distance of 7.5 < R(kpc) < 9.0, using a sample of ∼12 000 intermediate-mass (FGK) turn-off stars observed with the RAdial Velocity Experiment (RAVE) survey. The kinematics of this sample are determined using radial velocity measurements from RAV…
Identification of two new HMXBs in the LMC: an ∼2013 s pulsar and a probable SFXT
Haberl, F.; Hatzidimitriou, D.; Vasilopoulos, G. +2 more
We report on the X-ray and optical properties of two high-mass X-ray binary systems located in the Large Magellanic Cloud (LMC). Based on the obtained optical spectra, we classify the massive companion as a supergiant star in both systems. Timing analysis of the X-ray events collected by XMM-Newton revealed the presence of coherent pulsations (spi…
The absence of a thin disc in M81*
McHardy, I.; Young, A. J.; Emmanoulopoulos, D. +1 more
We present the results of simultaneous Suzaku and NuSTAR observations of the nearest low-luminosity active galactic nucleus (LLAGN), M81*. The spectrum is well described by a cut-off power law plus narrow emission lines from Fe K α, Fe xxv, and Fe xxvi. There is no evidence of Compton reflection from an optically thick disc, and we obtain the stro…
Are narrow-line Seyfert 1 galaxies highly accreting low-MBH AGNs?
Gliozzi, Mario; Williams, James K.; Rudzinsky, Ross V.
In this work, we test the hypothesis that narrow-line Seyfert 1 galaxies (NSL1s) are active galactic nuclei in their early phase and are therefore younger and more active than the more common broad-line Seyfert 1 galaxies (BLS1s). If that is true, then NLS1s should, on average, have lower black hole (BH) masses and higher accretion rates than BLS1…
M13 multiple stellar populations seen with the eyes of Strömgren photometry
Dalessandro, E.; Massari, D.; Bragaglia, A. +2 more
We present a photometric study of M13 multiple stellar populations over a wide field of view, covering approximately 6.5 half-light radii, using archival Isaac Newton Telescope observations to build an accurate multiband Strömgren catalogue. The use of the Strömgren index cy permits us to separate the multiple populations of M13 on the …
Dark halo structure in the Carina dwarf spheroidal galaxy: joint analysis of multiple stellar components
Dall'Ora, Massimo; Bono, Giuseppe; Monelli, Matteo +4 more
Photometric and spectroscopic observations of the Carina dSph revealed that this galaxy contains two dominant stellar populations of different age and kinematics. The coexistence of multiple populations provides new constraints on the dark halo structure of the galaxy, because different populations should be in equilibrium in the same dark matter …
Effects of interstellar dust scattering on the X-ray eclipses of the LMXB AX J1745.6-2901 in the Galactic Centre
Haberl, Frank; Jin, Chichuan; Ponti, Gabriele +2 more
AX J1745.6-2901 is an eclipsing low-mass X-ray binary in the Galactic Centre (GC). It shows significant X-ray excess emission during the eclipse phase, and its eclipse light curve shows an asymmetric shape. We use archival XMM-Newton and Chandra observations to study the origin of these peculiar X-ray eclipsing phenomena. We find that the shape of…
Anticorrelation between X-ray luminosity and pulsed fraction in the Small Magellanic Cloud pulsar SXP 1323
Zezas, Andreas; Drake, Jeremy J.; Wik, Daniel R. +4 more
We report the evidence for the anticorrelation between pulsed fraction (PF) and luminosity of the X-ray pulsar SXP 1323, found for the first time in a luminosity range 1035-1037 erg s-1 from observations spanning 15 yr. The phenomenon of a decrease in X-ray PF when the source flux increases has been observed in our…
Discovery of a 23.8 h QPO in the Swift light curve of XMMU J134736.6+173403
Jin, C.; Carpano, S.
XMMU J134736.6+173403 is an X-ray source discovered serendipitously by XMM-Newton, which was found to be spatially coincident with a pair of galaxies, including a Seyfert 2 galaxy, but presented in 2003 a very sharp persistent flux drop of a factor of 6.5 within 1 h. From the analysis of a set of 29 Swift observations conducted from 2008 February …