Search Publications
X-ray observations of VY Scl-type nova-like binaries in the high and low state
Mukai, K.; Orio, M.; Shugarov, S. +1 more
Four VY Scl-type nova-like systems were observed in X-rays during both the low- and the high-optical states. We examined Chandra, ROSAT, Swift and Suzaku archival observations of BZ Cam, MV Lyr, TT Ari and V794 Aql. The X-ray flux of BZ Cam is higher during the low state, but there is no supersoft X-ray source (SSS) as hypothesized in previous art…
A new candidate Wolf-Rayet X-ray binary in NGC 253
Zezas, Andreas; Maccarone, Thomas J.; Hornschemeier, Ann +5 more
We have discovered a persistent, but highly variable X-ray source in the nearby starburst galaxy NGC 253. The source varies at the level of a factor of about 5 in count rate on time-scales of a few hours. Two long observations of the source with Chandra and XMM-Newton show suggestive evidence for the source having a period of about 14-15 hours, bu…
KK258, a new transition dwarf galaxy neighbouring the Local Group
Wu, Po-Feng; Karachentsev, I. D.; Makarova, L. N. +2 more
Here, we present observations with the Advanced Camera for Surveys on the Hubble Space Telescope of the nearby, transition-type dwarf galaxy KK258 = ESO468-020. We measure a distance of 2.23 ± 0.05 Mpc using the Tip of Red Giant Branch method. We also detect Hα emission from this gas-poor dwarf transition galaxy at the velocity Vh = 92 …
Evolution from protoplanetary to debris discs: the transition disc around HD 166191
Ménard, F.; Sitko, M. L.; Wyatt, M. C. +12 more
HD 166191 has been identified by several studies as hosting a rare and extremely bright warm debris disc with an additional outer cool disc component. However, an alternative interpretation is that the star hosts a disc that is currently in transition between a full gas disc and a largely gas-free debris disc. With the help of new optical to mid-i…
Application of the new comprehensive X-ray spectral model to the two brightest intermediate polars EX Hydrae and V1223 Sagittarii
Ishida, Manabu; Hayashi, Takayuki
We applied the new comprehensive X-ray spectral model for the post-shock accretion column (PSAC) of the intermediate polars (IPs) constructed by Hayashi and Ishida to the Suzaku data of the two brightest IPs EX Hydrae and V1223 Sagittarii. The white dwarf (WD) mass and the specific accretion rate of EX Hya are estimated to be M_WD= 0.63_{-0.14}^{+…
Probing interstellar extinction near the 30 Doradus nebula with red giant stars
Girardi, Léo; Panagia, Nino; De Marchi, Guido
We have studied the interstellar extinction in a field of ∼ 3 arcmin × 3 arcmin located about 6 arcmin southwest of 30 Doradus in the Large Magellanic Cloud (LMC). Hubble Space Telescope observations in the U, B, V, I and Hα bands reveal patchy extinction in this field. The colour-magnitude diagram (CMD) shows an elongated stellar sequence, almost…
Locating star-forming regions in quasar host galaxies
Netzer, H.; Shemmer, O.; Lutz, Dieter +5 more
We present a study of the morphology and intensity of star formation in the host galaxies of eight Palomar-Green quasars using observations with the Hubble Space Telescope. Our observations are motivated by recent evidence for a close relationship between black hole growth and the stellar mass evolution in its host galaxy. We use narrow-band [O II…
Millihertz quasi-periodic oscillations and broad iron line from LMC X-1
Belloni, T.; Dewangan, G. C.; Alam, Md. Shah +2 more
We study the temporal and energy spectral characteristics of the persistent black hole X-ray binary LMC X-1 using two XMM-Newton and a Suzaku observation. We report the discovery of low-frequency (∼26-29 m Hz) quasi-periodic oscillations (QPOs). We also report the variability of the broad iron Kα line studied earlier with Suzaku. The QPOs are foun…
A blowout numerical model for the supernova remnant G352.7-0.1
Velázquez, P. F.; Esquivel, A.; Giacani, E. +1 more
We present 3D hydrodynamical simulations of the Galactic supernova remnant G352.7-0.1. This remnant is peculiar for having a shell-like inner ring structure and an outer arc in radio observations. In our model, the supernova explosion producing the remnant occurs inside and near the border of a spherical cloud with a density higher than that of th…
Ionized gas discs in elliptical and S0 galaxies at z < 1
Aragón-Salamanca, Alfonso; Zaritsky, Dennis; Kuntschner, Harald +7 more
We analyse the extended, ionized-gas emission of 24 early-type galaxies (ETGs) at 0 < z < 1 from the ESO Distant Cluster Survey (EDisCS). We discuss different possible sources of ionization and favour star formation as the main cause of the observed emission. 10 galaxies have disturbed gas kinematics, while 14 have rotating gas discs. In add…