Search results for "Color–color diagram"
showing 5 items of 5 documents
Spectral Evolution of Scorpio X‐1 along its Color‐Color Diagram
2007
We analyze a large collection of RXTE archive data of the bright X‐ray source Scorpius X‐1 in order to study the broadband spectral evolution of the source for different values of the inferred mass accretion rate by selecting energy spectra from its Color‐Color Diagram. We model the spectra with the combination of two absorbed components: a soft thermal component, which can be interpreted as thermal emission from an accretion disk, and a hybrid Comptonization component, which self‐consistently includes the Fe Kα fluorescence line and the Compton reflected continuum. The presence of hard emission in Scorpius X‐1 has been previously reported, however, without a clear relation with the accreti…
On the Spectral Evolution of Cygnus X-2 along its Color-Color Diagram
2002
We report on the results of a broad band (0.1-200 keV) spectral study of Cyg X-2 using two BeppoSAX observations taken in 1996 and 1997, respectively, for a total effective on-source time of ~100 ks. The color-color (CD) and hardness-intensity (HID) diagrams show that the source was in the horizontal branch (HB) and normal branch (NB) during the 1996 and 1997 observation, respectively. Five spectra were selected around different positions of the source in the CD/HID, two in the HB and three in the NB. These spectra are fit to a model consisting of a disk blackbody, a Comptonization component, and two Gaussian emission lines at ~1 keV and ~6.6 keV, respectively. The addition of a hard power-…
Study of the Temporal Behavior of 4U 1728−34 as a Function of Its Position in the Color‐Color Diagram
2001
We study the timing properties of the bursting atoll source 4U 1728-34 as a function of its position in the X-ray color-color diagram. In the island part of the color-color diagram (corresponding to the hardest energy spectra), the power spectrum of 4U 1728-34 shows several features such as a band-limited noise component present up to a few tens of Hz, a low-frequency quasi-periodic oscillation (LFQPO) at frequencies between 20 and 40 Hz, a peaked noise component around 100 Hz, and one or two QPOs at kHz frequencies. In addition to these, in the lower banana (corresponding to softer energy spectra) we also find a very low frequency noise (VLFN) component below ∼1 Hz. In the upper banana (co…
The VISTA Carina Nebula Survey II. Spatial distribution of the infrared-excess-selected young stellar population
2015
We performed a deep wide-field (6.76 deg^2) near-infrared survey with the VISTA telescope that covers the entire extent of the Carina nebula complex (CNC). The point-source catalog created from these data contains around four million individual objects down to masses of 0.1 M_sun. We present a statistical study of the large-scale spatial distribution and an investigation of the clustering properties of infrared-excesses objects, which are used to trace disk-bearing young stellar objects (YSOs). We find that a (J - H) versus (Ks - [4.5]) color-color diagram is well suited to tracing the population of YSO-candidates (cYSOs) by their infrared excess. We identify 8781 sources with strong infrar…
Broad-band Spectral Evolution of Scorpius X-1 along its Color-Color Diagram
2007
We analyze a large collection of RXTE archive data from April 1997 to August 2003 of the bright X-ray source Scorpius X-1 in order to study the broadband spectral evolution of the source for different values of the inferred mass accretion rate by studying energy spectra from selected regions in the Z-track of its Color-Color Diagram. A two-component model, consisting of a soft thermal component interpreted as thermal emission from an accretion disk and a thermal Comptonization component, is unable to fit the whole 3--200 keV energy spectrum at low accretion rates. Strong residuals in the highest energy band of the spectrum require the addition of a third component that can be fitted with a …