Search Publications
The Second Nucleus of NGC 7727: Direct Evidence for the Formation and Evolution of an Ultracompact Dwarf Galaxy
Kelson, Daniel D.; Seitzer, Patrick; Whitmore, Bradley C. +2 more
We present new observations of the late-stage merger galaxy NGC 7727, including Hubble Space Telescope/WFPC2 images and long-slit spectra obtained with the Clay telescope. NGC 7727 is relatively luminous ({M}V = -21.7) and features two unequal tidal tails, various bluish arcs and star clusters, and two bright nuclei 480 pc apart in proj…
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…
The Mass of the Cepheid V350 Sgr
Evans, Nancy Remage; Carpenter, Kenneth G.; Kober, Gladys V. +6 more
V350 Sgr is a classical Cepheid suitable for mass determination. It has a hot companion which is prominent in the ultraviolet (UV) and which is not itself a binary. We have obtained two high-resolution echelle spectra of the companion at orbital velocity maximum and minimum with the Space Telescope Imaging Spectrograph on the Hubble Space Telescop…
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 …
Spectral analysis of four surprisingly similar hot hydrogen-rich subdwarf O stars
Latour, M.; Chayer, P.; Green, E. M. +2 more
Context. Post-extreme horizontal branch stars (post-EHB) are helium-shell burning objects evolving away from the EHB and contracting directly towards the white dwarf regime. While the stars forming the EHB have been extensively studied in the past, their hotter and more evolved progeny are not so well characterized.
Aims: We perform a compreh…
The XXL Survey. XIX. A realistic population of simulated X-ray AGN: Comparison of models with observations
Paltani, S.; Lidman, C.; Pierre, M. +11 more
Modern cosmological simulations heavily rely on feedback from active galactic nuclei (AGN) in order to stave off overcooling in massive galaxies, and galaxy groups and clusters. Given that AGN are a key component of such simulations, an important independent test is whether or not the simulations capture the broad demographics of the observed AGN …
Constraints on brane-world inflation from the CMB power spectrum: revisited
Gangopadhyay, Mayukh R.; Mathews, Grant J.
We analyze the Randal Sundrum brane-world inflation scenario in the context of the latest CMB constraints from Planck. We summarize constraints on the most popular classes of models and explore some more realistic inflaton effective potentials. The constraint on standard inflationary parameters changes in the brane-world scenario. We confirm that …
Impact of gaps in the asteroseismic characterization of pulsating stars. I. The efficiency of pre-whitening
Garrido, R.; Moya, A.; Suárez, J. C. +4 more
Context. It is known that the observed distribution of frequencies in CoRoT and Kepler δ Scuti stars has no parallelism with any theoretical model. Pre-whitening is a widespread technique in the analysis of time series with gaps from pulsating stars located in the classical instability strip, such as δ Scuti stars. However, some studies have point…