- ID:
- ivo://CDS.VizieR/J/ApJ/838/45
- Title:
- eta Carinae obs. around the 2014 X-ray minimum
- Short Name:
- J/ApJ/838/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on Swift X-ray Telescope observations of Eta Carinae ({eta}Car), an extremely massive, long-period, highly eccentric binary obtained during the 2014.6 X-ray minimum/periastron passage. These observations show that {eta} Car may have been particularly bright in X-rays going into the X-ray minimum state, while the duration of the 2014 X-ray minimum was intermediate between the extended minima seen in 1998.0 and 2003.5 by Rossi X-Ray Timing Explorer (RXTE), and the shorter minimum in 2009.0. The hardness ratios derived from the Swift observations showed a relatively smooth increase to a peak value occurring 40.5 days after the start of the X-ray minimum, though these observations cannot reliably measure the X-ray hardness during the deepest part of the X-ray minimum when contamination by the "central constant emission" component is significant. By comparing the timings of the RXTE and Swift observations near the X-ray minima, we derive an updated X-ray period of P_X_=2023.7+/-0.7days, in good agreement with periods derived from observations at other wavelengths, and we compare the X-ray changes with variations in the HeII4686 emission. The middle of the "Deep Minimum" interval, as defined by the Swift column density variations, is in good agreement with the time of periastron passage derived from the HeII{lambda}4686 line variations.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/826/37
- Title:
- Fermi/GBM obs. of V404 Cygni 2015 outburst
- Short Name:
- J/ApJ/826/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- V404 Cygni was discovered in 1989 by the Ginga X-ray satellite during its only previously observed X-ray outburst and soon after confirmed as a black hole binary. On 2015 June 15, the Gamma-ray Burst Monitor (GBM) triggered on a new outburst of V404 Cygni. We present 13 days of GBM observations of this outburst, including Earth occultation flux measurements and spectral and temporal analysis. The Earth occultation fluxes reached 30 Crab with detected emission to 100keV and determined, via hardness ratios, that the source was in a hard state. At high luminosity, spectral analysis between 8 and 300keV showed that the electron temperature decreased with increasing luminosity. This is expected if the protons and electrons are in thermal equilibrium during an outburst with the electrons cooled by the Compton scattering of softer seed photons from the disk. However, the implied seed photon temperatures are unusually high, suggesting a contribution from another source, such as the jet. No evidence of state transitions is seen during this time period. The temporal analysis reveals power spectra that can be modeled with two or three strong, broad Lorentzians, similar to the power spectra of black hole binaries in their hard state.
- ID:
- ivo://CDS.VizieR/J/MNRAS/440/365
- Title:
- Galactic Bulge accreting binaries spectroscopy
- Short Name:
- J/MNRAS/440/365
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the identification of optical counterparts to 23 GBS X-ray sources. All sources are classified as accreting binaries according to the emission-line characteristics inferred from medium-resolution spectroscopy. To distinguish accreting binaries from chromospherically active objects, we develop criteria based on H{alpha} and HeI {lambda}{lambda}5786, 6678 emission-line properties available in the literature. The spectroscopic properties and photometric variability of each object is discussed and a classification is given where possible. At least 12 of the 23 systems show an accretion-dominated optical spectrum and another 6 show stellar absorption features in addition to emission lines indicating that they are probably accreting binaries in quiescence or in a low accretion rate state. Two sources are confirmed to be eclipsing: CX207 and CX794. CX207 is likely a magnetic cataclysmic variable (CV), while CX794 is a nova-like CV in the period gap. Finally, the large broadening (2100km/s FWHM) of the H{alpha} emission lines in CX446 and CX1004 suggests that they are also high-inclination or even eclipsing systems. Whether the compact object is a white dwarf in an eclipsing CV, a neutron star or a black hole in a high-inclination low-mass X-ray binary remains to be established.
- ID:
- ivo://CDS.VizieR/J/A+A/564/A107
- Title:
- Galactic ridge X-ray emission
- Short Name:
- J/A+A/564/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We predict a thin diffuse component of the Galactic ridge X-ray emission (GRXE) arising from the scattering of the radiation of bright X-ray binaries (XBs) by the interstellar medium. This scattered component has the same scale height as that of the gaseous disk (~80pc) and is therefore thinner than the GRXE of stellar origin (scale height ~130pc). The morphology of the scattered component is furthermore expected to trace the clumpy molecular and HI clouds. We calculate this contribution to the GRXE from known Galactic XBs assuming that they are all persistent. The known XBs sample is incomplete, however, because it is flux limited and spans the lifetime of X-ray astronomy (~50-years), which is very short compared with the characteristic time of 1000-10000 years that would have contributed to the diffuse emission observed today due to time delays. We therefore also use a simulated sample of sources, to estimate the diffuse emission we should expect in an optimistic case assuming that the X-ray luminosity of our Galaxy is on average similar to that of other galaxies. In the calculations we also take into account the enhancement of the total scattering cross-section due to coherence effects in the elastic scattering from multi-electron atoms and molecules.
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/2500
- Title:
- GX 339-4 radio/X-ray flux correlation
- Short Name:
- J/MNRAS/428/2500
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The existing radio and X-ray flux correlation for Galactic black holes in the hard and quiescent states relies on a sample which is mostly dominated by two sources (GX 339-4 and V404 Cyg) observed in a single outburst. In this paper, we report on a series of radio and X-ray observations of the recurrent black hole GX 339-4 with the Australia Telescope Compact Array, the Rossi X-ray Timing Explorer and the Swift satellites. With our new long-term campaign, we now have a total of 88 quasi-simultaneous radio and X-ray observations of GX 339-4 during its hard state, covering a total of seven outbursts over a 15-yr period. Our new measurements represent the largest sample for a stellar mass black hole, without any bias from distance uncertainties, over the largest flux variations and down to a level that could be close to quiescence, making GX 339-4 the reference source for comparison with other accreting sources (black holes, neutrons stars, white dwarfs and active galactic nuclei).
- ID:
- ivo://CDS.VizieR/J/A+A/559/A87
- Title:
- H{alpha} observations of LSI+61 303
- Short Name:
- J/A+A/559/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report 137 spectral observations of the H{alpha} emission line of the radio- and gamma-ray-emitting Be/X-ray binary LSI+61 303 obtained during the period of September 1998 - January 2013. From measuring various H{alpha} parameters, we found that the orbital modulation of the H{alpha} is best visible in the equivalent width ratio EW(B)/EW(R), the equivalent width of the blue hump, and in the radial velocity of the central dip. The periodogram analysis confirmed that the H{alpha} emission is modulated with the orbital and superorbital periods. For the past 20 years the radius of the circumstellar disk is similar to the Roche lobe size at the periastron. It is probably truncated by a 6:1 resonance. The orbital maximum of the equivalent width of H{alpha} emission peaks after the periastron and coincides on average with the X-ray and gamma-ray maxima.
- ID:
- ivo://CDS.VizieR/J/A+A/441/685
- Title:
- HeI & HeII radial velocities of Sk 160/SMC X-1
- Short Name:
- J/A+A/441/685
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new optical spectroscopy of the eclipsing binary pulsar Sk 160/SMC X-1. From the He I absorption lines, taking heating corrections into account, we determine the radial velocity semi-amplitude of Sk 160 to be 21/8+/-1.8km/s. Assuming Sk 160 fills its Roche-lobe, the inclination angle of the system is i=65.3+/-1.3{deg} and in this case we obtain upper limits for the mass of the neutron star as Mx=1.21+/-0.10M_{sun}_ and for Sk 160 as Mo=16.6+/-0.4M_{sun}.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A110
- Title:
- Her X-1 pulse profiles
- Short Name:
- J/A+A/550/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The accreting X-ray pulsar Her X-1 shows two types of long-term variations, both with periods of ~35 days: 1) Turn-on cycles, a modulation of the flux, with a ten-day long Main-On and a five-day long Short-On, separated by two Off-states, and 2) a systematic variation in the shape of the 1.24s pulse profile. While there is general consensus that the flux modulation is due to variable shading of the X-ray emitting regions on the surface of the neutron star by the precessing accretion disk, the physical reason for the variation in the pulse profiles has remained controversial. Following the suggestion that free precession of the neutron star may be responsible for the variation in the pulse profiles, we developed a physical model of strong feedback interaction between the neutron star and the accretion disk in order to explain the seemingly identical values for the periods of the two types of variations, which were found to be in basic synchronization. In a deep analysis of pulse profiles observed by several different satellites over the last three decades we now find that the clock behind the pulse profile variations shows exactly the same erratic behavior as the turn-on clock, even on short time scales (a few 35d cycles), suggesting that there may in fact be only one 35d clock in the system. If this is true, it raises serious questions with respect to the idea of free precession of the neutron star, namely how the neutron star can change its precessional period every few years by up to 2.5% and how the feedback can be so strong, such that these changes can be transmitted to the accretion disk on rather short time scales.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/1701
- Title:
- High-frequency QPO in black hole binaries
- Short Name:
- J/MNRAS/426/1701
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the analysis of a large data base of X-ray observations of 22 galactic black hole transients with the Rossi X-Ray Timing Explorer throughout its operative life for a total exposure time of ~12ms. We excluded persistent systems and the peculiar source GRS 1915+105, as well as the most recently discovered sources. The semi-automatic homogeneous analysis was aimed at the detection of high-frequency (100-1000Hz) quasi-periodic oscillations (QPO), of which several cases were previously reported in the literature.
- ID:
- ivo://CDS.VizieR/J/A+A/442/1135
- Title:
- High-mass X-ray binaries in the Magellanic Clouds
- Short Name:
- J/A+A/442/1135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of high-mass X-ray binaries in the Magellanic Clouds. The catalogue lists source name(s), coordinates, apparent magnitudes, orbital parameters, and X-ray luminosity of 128 high-mass X-ray binaries, together with stellar parameters of the components, other characteristic properties and a comprehensive selection of the relevant literature. The aim of this catalogue is to provide easy access to the basic information on the X-ray sources and their counterparts in other wavelength ranges (UV, optical, IR, radio). Most of the sources are identified to be Be/X-ray binaries. Some sources, however, are only tentatively identified as high-mass X-ray binaries on the basis of a transient character and/or a hard X-ray spectrum. Further identification in other wavelength bands is needed to finally determine the nature of these sources. In cases where there is some doubt about the high-mass nature of the X-ray binary this is mentioned. Literature published before 1 May 2005 has, as far as possible, been taken into account.
