共查询到20条相似文献，搜索用时 31 毫秒
1.
2.
3.
4.
Magaretha L. Pretorius 《Monthly notices of the Royal Astronomical Society》2009,395(1):386-393
The European Space Agency γ-ray telescope, INTEGRAL , is detecting relatively more intrinsically rare cataclysmic variables (CVs) than were found by surveys at lower energies. Specifically, a large fraction of the CVs that are INTEGRAL sources consists of asynchronous polars and intermediate polars (IPs). IP classifications have been proposed for the majority of CVs discovered by INTEGRAL , but, in many cases, there is very little known about these systems. In order to address this, I present time-resolved optical data of five CVs discovered through INTEGRAL observations. The white dwarf spin modulation is detected in high-speed photometry of three of the new CVs (IGR J15094−6649, IGR J16500−3307 and IGR J17195−4100), but two others (XSS J12270−4859 and IGR J16167−4957) show no evidence of magnetism, and should be considered unclassified systems. Spectroscopic orbital period ( P orb ) measurements are also given for IGR J15094−6649, IGR J16167−4957, IGR J16500−3307 and IGR J17195−4100. 相似文献
5.
Magaretha L. Pretorius Christian Knigge Ulrich Kolb 《Monthly notices of the Royal Astronomical Society》2007,374(4):1495-1505
Large differences between the properties of the known sample of cataclysmic variable stars (CVs) and the predictions of the theory of binary star evolution have long been recognized. However, because all existing CV samples suffer from strong selection effects, observational biases must be taken into account before it is possible to tell whether there is an inconsistency. In order to address this problem, we have modelled the impact of selection effects on observed CV samples using a Monte Carlo approach. By simulating the selection criteria of the Palomar–Green (PG) Survey, we show that selection effects cannot reconcile the predictions of standard CV evolution theory with the observed sample. More generally, we illustrate the effect of the biases that are introduced by magnitude limits, selection cuts in U − B and restrictions in Galactic latitude. 相似文献
6.
M. L. Pretorius C. Knigge D. O'Donoghue J. P. Henry I. M. Gioia C. R. Mullis 《Monthly notices of the Royal Astronomical Society》2007,382(3):1279-1288
We use the ROSAT North Ecliptic Pole (NEP) survey to construct a small, but purely X-ray flux-limited sample of cataclysmic variable stars (CVs). The sample includes only four systems, two of which (RX J1715.6+6856 and RX J1831.7+6511) are new discoveries. We present time-resolved spectroscopy of the new CVs and measure orbital periods of 1.64 ± 0.02 and 4.01 ± 0.03 h for RX J1715.6+6856 and RX J1831.7+6511, respectively. We also estimate distances for all the CVs in our sample, based mainly on their apparent brightness in the infrared. The space density of the CV population represented by our small sample is 1.1+2.3 −0.7 × 10−5 pc−3 . We can also place upper limits on the space density of any subpopulation of CVs too faint to be included in the NEP survey. In particular, we show that if the overall space density of CVs is as high as 2 × 10−4 pc−3 (as has been predicted theoretically), the vast majority of CVs must be fainter than L X ≃ 2 × 1029 erg s−1 . 相似文献
7.
8.
9.
10.
This contribution to “The 1st year of science with X‐shooter” conference illustrates 2 different applications of the new ESO multi‐waveband spectrograph to the study of interacting binaries. In particular we present spectra collected during the late decline of U Sco 2010 outburst and during a low/hard X‐ray phase of the black hole candidate GX339‐4. In both cases the unprecedented spectral coverage and resolution offered by X‐shooter have unveiled unexpected features (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
A. Siviero U. Munari S. Dallaporta P. Valisa V. Luppi S. Moretti S. Tomaselli S. Bacci F. Ballardini G. Cherini M. Graziani A. Frigo A. Vagnozzi 《Monthly notices of the Royal Astronomical Society》2009,399(4):2139-2145
In this paper, we discuss the early phases of the ongoing outburst that CI Cyg, a prototype symbiotic star, is currently undergoing after 30-year quiescence. We have tightly monitored CI Cyg in B V R C I C bands, starting a whole year before the onset of the outburst, and in addition we obtained numerous Echelle high- and low-resolution absolutely flux-calibrated spectra. The outburst started while the accreting white dwarf (WD) was being eclipsed by the Roche lobe filling M giant companion, and it was discovered during the egress phase on the second half of 2008 August. The system reached peak V -band brightness in early 2008 October and has been characterized by amplitudes Δ B = 1.9, Δ V = 1.5, Δ R C = 0.9, Δ I C = 0.4 mag. At maximum V -band brightness, the outbursting WD had expanded to closely resemble an F3 II/Ib star, with MV =−3.5, T eff ∼ 6900 K and R = 28 R⊙ . The high-ionization emission lines ([Ne v ], [Fe vii ], He ii ) disappeared and only lower ionization lines were visible. Balmer and He i emission lines declined in equivalent width but increased in absolute flux. The output radiated by the hot component during the outburst corresponds to nuclear burning proceeding at a 2 × 10−8 M⊙ yr−1 rate. 相似文献
12.
F. Haberl 《Astronomische Nachrichten》2010,331(2):239-240
The workshop “Supersoft X‐ray Sources – New Developments” brought together observers and theoretician to discuss the present status and unsolved problems of supersoft source research. A large part of the workshop was devoted to optical novae and their supersoft state. Large samples of supersoft X‐ray sources were presented from nearby galaxies, as well as extensive monitoring campaigns ofbright individual sources. The theoretical modelling oflight curves and high‐resolution X‐ray spectra are well underway, but details are often not yet understood (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
Short time-scale photometric properties of eight faint cataclysmic variable (CV) stars are presented. Nova Carinae 1895 (RS Car) has a photometric modulation at 1.977 h that could be either an orbital or a superhump period. Nova Carinae 1948 (V365 Car) shows flickering, but any orbital modulation has a period in excess of 6 h. The nova-like variable and X-ray source V436 Car has an orbital modulation at P orb = 4.207 h , no detectable period near 2.67 h (which had previously given it a possible intermediate polar classification), and dwarf nova oscillations (DNOs) at ∼40 s. Nova Crucis 1936 (AP Cru) has a double-humped ellipsoidal modulation at P orb = 5.12 h and a stable modulation at 1837 s characteristic of an intermediate polar. Nova Chamaeleontis 1953 (RR Cha) is an eclipsing system with P orb = 3.362 h , but at times shows negative superhumps at 3.271 h and positive superhumps at 3.466 h. In addition it has a stable period at 1950 s, characteristic of an intermediate polar. BI Ori is a dwarf nova that we observed at quiescence and outburst without detecting any orbital modulation. CM Phe is a nova-like variable for which we confirm the value of P orb = 6.454 h found by Hoard, Wachter & Kim-Quijano . We have identified the remnant of Nova Sagittarii 1931 (V522 Sgr) with a flickering source ∼2.2 mag fainter than the previously proposed candidate (which we find to be non-variable). 相似文献
14.
15.
16.
17.
18.
R. Baptista 《Astronomische Nachrichten》2004,325(3):181-184
The accretion disc eclipse mapping method is an astrotomographic inversion technique that makes use of the information contained in eclipse light curves to probe the structure, the spectrum and the time evolution of accretion discs in cataclysmic variables. This paper presents examples of eclipse mapping results that have been key to improve our understanding of accretion physics. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
19.