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X-ray and optical-to-infrared follow-up observations of the transient X-ray burster SAX J1810.8–2609
J. Greiner A. J. Castro-Tirado TH. Boller H. W. Duerbeck S. Covino G. L. Israel M. J. D. Linden-Vørnle X. Otazu-Porter 《Monthly notices of the Royal Astronomical Society》1999,308(3):L17-L21
We have performed a ROSAT follow-up observation of the X-ray transient SAX J1810.8–2609 on 1998 March 24 and detected a bright X-ray source (named RX J1810.7–2609) which was not detected during the ROSAT all-sky survey in September 1990. Optical-to-infrared follow-up observations of the 10" radius ROSAT HRI X-ray error box revealed one variable object ( R =19.5±0.5 on March 13, R >21.5 on 1998 August 27) which we tentatively propose as the optical/IR counterpart of RX J1810.7–2609≡SAX J1810.8–2609. 相似文献
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V.Kolokotronis M.Plionis P.Coles S.Borgani 《Monthly notices of the Royal Astronomical Society》1998,295(1):19-32
We investigate the sampling and dipole convergence properties of flux-limited samples of mock X-ray clusters in relation to their underlying 'parent' cluster distribution. To this purpose, we resort to numerical simulations of the cluster distribution and extract samples resembling the main observational features of X-ray selected cluster samples. The flux-limited samples, being quite sparse, underestimate the amplitude of the 'parent' cluster dipole by ≈ 15 per cent on average for Local Group-like observers. However, the general shapes of their dipole amplitude profiles are in relatively good agreement. We also calculate the expected contribution of clusters, selected according to the relevant criteria, to the soft (i.e. 0.1–2.4 keV) extragalactic X-ray background (XRB), using the ESO Key Project X-ray luminosity function, assuming a flat universe with vanishing cosmological constant. We obtain a value of about 10 per cent of the observed XRB flux. 相似文献
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F. J. Carrera X. Barcons A. C. Fabian G. Hasinger K. O. Mason R. G. McMahon J. P. D. Mittaz & M. J. Page 《Monthly notices of the Royal Astronomical Society》1998,299(1):229-236
A total of 235 active galactic nuclei (AGN) from two different soft X-ray surveys [the ROSAT Deep Survey (DRS) and the ROSAT International X-ray Optical Survey (RIXOS)] with redshifts between 0 and 3.5 are used to study the clustering of X-ray selected AGN and its evolution. A 2σ significant detection of clustering of such objects is found on scales < 40–80 h −1 Mpc in the RIXOS sample, while no clustering is detected on any scales in the DRS sample. Assuming a single power-law model for the spatial correlation function (SCF), quantitative limits on the AGN clustering have been obtained: a comoving correlation length 1.5 ≲ r 0 ≲ 3.3 h −1 Mpc is implied for comoving evolution, while 1.9 ≲ r 0 ≲ 4.8 for stable clustering and 2.2 ≲ r 0 ≲ 5.5 for linear evolution. These values are consistent with the correlation lengths and evolutions obtained for galaxy samples, but imply smaller amplitude or faster evolution than recent ultraviolet and optically selected AGN samples. We also constrain the ratio of bias parameters between X-ray selected AGN and IRAS galaxies to be ≲ 1.7 on scales ≲ 10 h −1 Mpc, a somewhat smaller value than is inferred from local large-scale dynamical studies. 相似文献
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J.Manners O.Almaini A.Lawrence 《Monthly notices of the Royal Astronomical Society》2002,330(2):390-398
We present an analysis of X-ray variability in a sample of 156 radio-quiet quasars taken from the ROSAT archive, covering a redshift range 0.12) in the sense that QSOs of the same X-ray luminosity are more variable at z>2 . We discuss possible explanations for this effect. The simplest explanation may be that high-redshift QSOs are accreting at a larger fraction of the Eddington limit than local AGNs. 相似文献
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R. J. Wilman A. C. Fabian P. Gandhi 《Monthly notices of the Royal Astronomical Society》2000,318(1):L11-L14
The two brightest hard X-ray sources discovered serendipitously by Chandra in the field of the lensing cluster A2390 are found to have ISOCAM counterparts at 6.7 and 15 μm. We use this fact, together with their non-detection by SCUBA at 850 μm, as the basis for dusty radiative transfer modelling of their infrared spectral energy distributions. For the best-fitting models, we find that the dust that reprocesses the optical–ultraviolet light in these Compton-thin active galactic nuclei (AGN) is heated to near its sublimation temperature (above 1000 K), with an inner radius within a parsec of the nucleus. Some warm-dust models with inner temperatures of 200 K are also formally acceptable. These findings strongly support the obscured AGN hypothesis for the new hard X-ray Chandra sources, which lack both strong emission lines and 850-μm SCUBA detections. 相似文献
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The X-ray nuclei of intermediate-redshift radio sources 总被引：2，自引：0，他引：2
M. J. Hardcastle D. A. Evans J. H. Croston 《Monthly notices of the Royal Astronomical Society》2006,370(4):1893-1904
We re-assess the question of a systematic time delay between the formation of the progenitor and its explosion in a Type Ia supernova (SN Ia) using the Hubble Higher- z Supernova Search sample. While a previous analysis indicated a significant time delay, with a most likely value of 3.4 Gyr, effectively ruling out all previously proposed progenitor models, our analysis shows that the time-delay estimate is dominated by systematic errors, in particular due to uncertainties in the star formation history (SFH). We find that none of the popular progenitor models under consideration can be ruled out with any significant degree of confidence. The inferred time delay is mainly determined by the peak in the assumed SFH. We show that, even with a much larger supernova sample, the time-delay distribution cannot be reliably reconstructed without better constraints on the SFH. 相似文献
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New radio and X-ray data are reported for the rich cluster Abell 2319. This object is known from optical data to consist of two separate clusters, which are displaced by about 10′ in the NW direction, and could be in a pre-merger state.
In the radio domain, the cluster is characterized by the presence of a central diffuse halo source, more extended and powerful than the prototype halo in the Coma cluster. The radio halo shows an irregular structure, elongated in the NE-SW direction, and also extended towards the NW. We also report data on the extended radio galaxies located within the halo, or in its proximity.
The cluster X-ray brightness distribution shows an elongated structure towards the NW, in the radial region between 6′–12′, i.e. in the direction of the subcluster. This feature is exactly coincident with the NW extension of the radio halo. In addition, more substructural features are identified which could be due to an ongoing merger of the cluster with yet another mass component.
The radio halo morphology is correlated with the X-ray structure and the existence of merger processes in the cluster. The cluster merger can provide energy to maintain the radio halo, while the origin of the relativistic particles seems more problematic. 相似文献
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Lupin Chun-Che Lin Hsiang-Kuang Chang 《Monthly notices of the Royal Astronomical Society》2008,387(2):729-734
A periodicity search of gamma-ray data is usually difficult because of the small number of detected photons. A periodicity in the timing signal at other energy bands from the counterpart to the gamma-ray source may help to establish the periodicity in the gamma-ray emission and strengthen the identification of the source in different energy bands. However, it may still be difficult to find the period directly from X-ray data because of limited exposure. We have developed a procedure, by cross-checking two X-ray data sets, to find candidate periods for X-ray sources that are possible counterparts to gamma-ray pulsar candidates. Here, we report on the results of this method obtained with all the currently available X-ray data of eight X-ray sources. Some attractive periodicity features were found. These candidate periods can serve as the target periods for a future search when new data become available, so that a blind search with a huge number of trials can be avoided. 相似文献
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K. O. Mason F. J. Carrera G. Hasinger H. Andernach A. Aragon-Salamanca X. Barcons R. Bower W. N. Brandt G. Branduardi-Raymont J. Burgos-Martín F. Cabrera-Guerra R. Carballo F. Castander R. S. Ellis J. I. González-Serrano E. Martínez-González J. M. Martín-Mirones R. G. McMahon J. P. D. Mittaz K. L. Nicholson M. J. Page I. Pérez-Fournon E. M. Puchnarewicz E. Romero-Colmenero A. D. Schwope B. Vila M. G. Watson D. Wonnacott 《Monthly notices of the Royal Astronomical Society》2000,311(3):456-484
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In this paper we propose that the observed unpulsed X-ray emission in AE Aquarii is the result of a very tenuous hot corona associated with the secondary star, which is pumped magnetohydrodynamically by the propeller action of the fast rotating white dwarf. It is shown that the closed coronal field of the secondary star envelops a substantial portion of the binary system, including the fast rotating magnetized white dwarf. This implies that the propeller outflow of material in AE Aquarii is initiated inside an enveloping magnetic cavity. The outflow crossing the secondary dead-zone field constitutes a βgen = (8πρ v 2 esc / B 2 ) ≫ 1 plasma, acting as a magnetohydrodynamic generator resulting in the induction of field-aligned currents in these closed magnetospheric circuits where βcir = (8π nkT / B 2 ) ≪ 1 . The Ohmic heating of the coronal circuit can readily account for a T x ≥ 107 K plasma in the coronal flux tubes connecting the generator and the stellar surface. Further, the bremsstrahlung losses of the thermal electrons in the coronal circuit can readily drive the observed unpulsed X-ray luminosity of L x ∼ 1031 erg s −1 , which correlates with the luminosity and relatively large source implied by recent XMM–Newton observations. 相似文献
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