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The XMM-Newton Bright Survey sample of absorbed quasars: X-ray and accretion properties
Vignali, C.; Ballo, L.; Carrera, F. J. +5 more
Although absorbed quasars are extremely important for our understanding of the energetics of the Universe, the main physical parameters of their central engines are still poorly known. In this work, we present and study a complete sample of 14 quasars (QSOs) that are absorbed in the X-rays (column density NH > 4 × 1021 cm<…
Quantitative Method for the Optimal Subtraction of Continuum Emission from Narrow-band Images: Skewness Transition Analysis
Dickinson, Mark; Calzetti, Daniela; Hong, Sungryong
We present an objective method to remove the stellar continuum emission from narrow-band images to derive emission-line images. The method is based on the skewness of the pixel histogram of the residual images. Specifically, we exploit a transition in the skewness of the signal in the continuum-subtracted image, which appears when the image change…
The Emerging Planetary Nebula CRL 618 and its Unsettled Central Star(s)
Velázquez, P. F.; Balick, B.; Kwitter, K. B. +2 more
We report deep long-slit emission-line spectra, the line flux ratios, and Doppler profile shapes of various bright optical lines. The low-ionization lines (primarily [N I], [O I], [S II], and [N II]) originate in shocked knots, as reported by many previous observers. Dust-scattered lines of higher ionization are seen throughout the lobes but do no…
The effective temperatures of O-type stars from UV spectroscopy
Bianchi, Luciana; Garcia, Miriam
We present an analysis of high resolution spectra in the far-UV - UV range (∼905-2000 Å) with non-LTE, spherical, hydrodynamical, line-blanketed models, of three O-type Galactic stars, and derive their photospheric and wind parameters. These data extend previously analyzed samples and fill a gap in spectral type coverage. The combined sample confi…
Timing studies of X Persei and the discovery of its transient quasi-periodic oscillation feature
Serim, M. M.; Şahiner, Ş.; Baykal, A. +3 more
We present a timing analysis of X Persei (X Per) using observations made between 1998 and 2010 with the Proportional Counter Array (PCA) onboard the Rossi X-ray Timing Explorer (RXTE) and with the INTEGRAL Soft Gamma-Ray Imager (ISGRI). All pulse arrival times obtained from the RXTE-PCA observations are phase-connected and a timing solution is obt…
Rummaging inside the Eskimo's parka: variable asymmetric planetary nebula fast wind and a binary nucleus?
Prinja, R. K.; Urbaneja, M. A.
We report on high-resolution optical time series spectroscopy of the central star of the `Eskimo' planetary nebula NGC 2392. Data sets were secured with the European Southern Observatory (ESO) 2.3 m in 2006 March and Canada-France-Hawaii Telescope (CFHT) 3.6 m in 2010 March to diagnose the fast wind and photospheric properties of the central star.…
Hard X-ray continuum from lunar surface: Results from High Energy X-ray spectrometer (HEX) onboard Chandrayaan-1
Banerjee, D.; Sreekumar, P.; Sudhakar, M. +10 more
The High Energy X-ray spectrometer (HEX) on Chandrayaan-1 was designed to study the photon emission in the range of 30-270 keV from naturally occurring radioactive decay of 238U and 232Th series nuclides from the lunar surface. The primary objective of HEX was to study the transport of volatiles on the lunar surface using rad…
The main pillar: Assessment of space weather observational asset performance supporting nowcasting, forecasting, and research to operations
St. Cyr, O. C.; Hesse, M.; Posner, A.
Space weather forecasting critically depends upon availability of timely and reliable observational data. It is therefore particularly important to understand how existing and newly planned observational assets perform during periods of severe space weather. Extreme space weather creates challenging conditions under which instrumentation and space…
Ionizing stellar population in the disc of NGC 3310 - II. The Wolf-Rayet population
Pérez-Montero, E.; Sánchez, S. F.; Díaz, A. I. +3 more
We use integral field spectroscopy to study in detail the Wolf-Rayet (WR) population in NGC 3310, spatially resolving 18 star-forming knots with typical sizes of 200-300 pc in the disc of the galaxy hosting a substantial population of WRs. The detected emission in the so-called blue bump is attributed mainly to late-type nitrogen WRs (WNL), rangin…
Validation of optimized population synthesis through mock spectra and Galactic globular clusters
Schiavon, Ricardo P.; Courteau, Stéphane; Roediger, Joel C. +1 more
Optimized population synthesis provides an empirical method to extract the relative mix of stellar evolutionary stages and the distribution of atmospheric parameters within unresolved stellar systems, yet a robust validation of this method is still lacking. We here provide a calibration of population synthesis via non-linear bound-constrained opti…