67 research outputs found
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No full textRelato de Efrain Gatuzz para la revista Sci-FdI.Depto. de Sistemas Informáticos y ComputaciónFac. de InformáticaTRUEpu
Progenitores
No full textRelato de Efrain Gatuzz para la revista Sci-FdI.Depto. de Sistemas Informáticos y ComputaciónFac. de InformáticaTRUEpu
Probing the structure of the gas in the Milky Way through X-ray high-resolution spectroscopy
No full text
Searching for the warm-hot intergalactic medium using XMM-Newton high-resolution X-ray spectra
No full textThe problem of missing baryons in the local universe remains an open
question. One propose alternative is that at low redshift missing baryons are
in the form of the Warm Hot Intergalactic Medium (WHIM). In order to test this
idea, we present a detailed analysis of X-ray high-resolution spectra of six
extragalactic sources, Mrk 421, 1ES 1028+511, 1ES 1553+113, H2356-309, PKS
0558-504 and PG 1116+215, obtained with the XMM-Newton Reflection Grating
Spectrometer to search for signals of WHIM and/or circumgalactic medium (CGM)
X-ray absorbing gas. We fit the X-ray absorption with the IONeq model, allowing
us to take into account the presence of X-ray spectral features due to the
multiphase component of the local ISM. An additional IONeq component is
included to model the WHIM absorption, instead of the traditional Gaussian
absorption line modeling. We found no statistical improvement in the fits when
including such component in any of the sources, concluding that we can safely
reject a successful detection of WHIM absorbers towards these lines of sights.
Our simulation shows that the presence of the multiphase ISM absorption
features prevents detection of low-redshift WHIM absorption features in the 17
A spectral region for moderate exposures using high-resolution spectra.Comment: 12 pages, 7 figure
Probing the physical properties of the intergalactic medium using SRG/eROSITA spectra from blazars
No full textMost baryonic matter resides in the intergalactic medium (IGM). This diffuse gas is primarily composed of ionized hydrogen and helium and fills the space between galaxies. Observations of this environment are crucial for better understanding the physical processes in it. We present an analysis of the IGM absorption using blazar spectra from the first eROSITA all-sky survey (eRASS1) performed onboard of the Spectrum-Roentgen-Gamma mission (SRG) and XMM-Newton X-ray observations. First, we fit the continuum spectra using a log-parabolic spectrum model and fixed the Galactic absorption. Then, we included a collisional ionization equilibrium model, namely IONe
On the Detectability of CO Molecules in the Interstellar Medium via X-Ray Spectroscopy
No full textWe present a study of the detectability of CO molecules in the Galactic interstellar medium using high-resolution X-ray spectra obtained with the XMM-Newton Reflection Grating Spectrometer. We analysed 10 bright low mass X-ray binaries (LMXBs) to study the CO contribution in their line of sights. A total of 25 observations were fitted with the ISMabs X-ray absorption model which includes photoabsorption cross-sections for Oi, Oii, Oiii and CO. We performed a Monte Carlo (MC) simulation analysis of the goodness of fit in order to estimate the significance of the CO detection. We determine that the statistical analysis prevents a significant detection of CO molecular X-ray absorption features, except for the lines of sight towards XTE J1718-330 and 4U 1636-53. In the case of XTE J1817-330, this is the first report of the presence of CO along its line of sight. Our results reinforce the conclusion that molecules have a minor contribution to the absorption features in the O K-edge spectral region. We estimate a CO column density lower limit to perform a significant detection with XMM-Newton of N(CO) greater than 6 x 10(exp 16) per sq cm for typical exposure times
Implications of the Warm Corona and Relativistic Reflection Models for the Soft Excess in Mrk 509
No full textWe present the analysis of the first Nuclear Spectroscopic Telescope Array observations (~220 ks), simultaneous with the last Suzaku observations (~50 ks), of the active galactic nucleus of the bright Seyfert 1 galaxy Mrk 509. The time-averaged spectrum in the 1–79 keV X-ray band is dominated by a power-law continuum (Γ ~ 1.8–1.9), a strong soft excess around 1 keV, and signatures of X-ray reflection in the form of Fe K emission (~6.4 keV), an Fe K absorption edge (~7.1 keV), and a Compton hump due to electron scattering (~20–30 keV). We show that these data can be described by two very different prescriptions for the soft excess: a warm (kT ~ 0.5–1 keV) and optically thick (τ ~ 10–20) Comptonizing corona or a relativistically blurred ionized reflection spectrum from the inner regions of the accretion disk. While these two scenarios cannot be distinguished based on their fit statistics, we argue that the parameters required by the warm corona model are physically incompatible with the conditions of standard coronae. Detailed photoionization calculations show that even in the most favorable conditions, the warm corona should produce strong absorption in the observed spectrum. On the other hand, while the relativistic reflection model provides a satisfactory description of the data, it also requires extreme parameters, such as maximum black hole spin, a very low and compact hot corona, and a very high density for the inner accretion disk. Deeper observations of this source are thus necessary to confirm the presence of relativistic reflection and further understand the nature of its soft excess
Nitrogen X-ray absorption in the local ISM
No full textNitrogen is one of the most abundant metals in the interstellar medium (ISM), and thus it constitutes an excellent test to study a variety of astrophysical environments, ranging from nova to active galactic nuclei. We present a detailed analysis of the gaseous component of the N K-edge using high-resolution XMM–Newton spectra of 12 Galactic and 40 extragalactic sources. For each source, we have estimated column densities for N i, N ii, N iii, N v, N vi, and N vii ionic species, which trace the cold, warm, and hot phases of the local Galactic ISM. We have found that the cold-warm component column densities decrease with the Galactic latitude, while the hot component does not. Moreover, the cold column density distribution is in good agreement with UV measurements. This is the first detailed analysis of the nitrogen K-edge absorption due to ISM using high-resolution X-ray spectra
What We Learn from the X-Ray Grating Spectra of Nova SMC 2016
No full textNova SMC 2016 has been the most luminous nova known in the direction of the Magellanic Clouds. It turned into a very luminous supersoft X-ray source between days 16 and 28 after the optical maximum. We observed it with Chandra, the HRC-S camera, and the Low Energy Transmission Grating on 2016 November and 2017 January (days 39 and 88 after optical maximum), and with XMM-Newton on 2016 December (day 75). We detected the compact white dwarf (WD) spectrum as a luminous supersoft X-ray continuum with deep absorption features of carbon, nitrogen, magnesium, calcium, probably argon, and sulfur on day 39, and oxygen, nitrogen, and carbon on days 75 and 88. The spectral features attributed to the WD atmosphere are all blueshifted, by about 1800 km s-1 on day 39 and up to 2100 km s-1 in the following observations. Spectral lines attributed to low-ionization potential transitions in the interstellar medium are also observed. Assuming the distance to the Small Magellanic Cloud, the bolometric luminosity exceeded the Eddington level for at least three months. A preliminary analysis with atmospheric models indicates an effective temperature of around 700,000 K on day 39, peaking at the later dates in the 850,000-900,000 K range, as expected for a ≃1.25 M ⊙ WD. We suggest a possible classification as an oxygen-neon WD, but more precise modeling is needed to accurately determine the abundances. The X-ray light curves show a large, aperiodic flux variability, which is not associated with spectral variability. We detected red noise, but did not find periodic or quasiperiodic modulations
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