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Register a new userMultiwavelength Campaign of Observations of AE Aqr
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Christopher W. Mauche
Publication date
2011
fields
Physics
and research's language is
English
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We provide a summary of results, obtained from a multiwavelength (TeV gamma-ray, X-ray, UV, optical, and radio) campaign of observations of AE Aqr conducted in 2005 August 28-September 2, on the nature and correlation of the flux variations in the various wavebands, the white dwarf spin evolution, the properties of the X-ray emission region, and the very low upper limits on the TeV gamma-ray flux.
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We have developed a numerical MHD model of the propeller candidate star AE Aqr using axisymmetric magneto-hydrodynamic (MHD) simulations. We suggest that AE Aqr is an intermediate polar-type star, where the magnetic field is relatively weak and an accretion disc may form around the white dwarf. The star is in the propeller regime, and many of its observational properties are determined by the disc-magnetosphere interaction. Comparisons of the characteristics of the observed versus modelled AE Aqr star show that the model can explain many observational properties of AE Aqr. In a representative model, the magnetic field of the star is Bapprox 3.3x10^5 G and the time averaged accretion rate in the disc is 5.5times 10^{16} g/s. Most of this matter is ejected into conically-shaped winds. The numerical model explains the rapid spin-down of AE Aqr through the outflow of angular momentum from the surface of the star to the wind, corona and disc. The energy budget in the outflows, 9x10^{33} erg/s, is sufficient for explaining the observed flaring radiation in different wavebands. The time scale of ejections into the wind matches the short time scale variability in the light curves of AE Aqr.
We report on radio timing and multiwavelength observations of the 4.66 ms redback pulsar J1048+2339, which was discovered in an Arecibo search targeting the Fermi-LAT source 3FGLJ1048.6+2338. Two years of timing allowed us to derive precise astrometric and orbital parameters for the pulsar. PSR J1048+2339 is in a 6-hour binary, and exhibits radio eclipses over half the orbital period and rapid orbital period variations. The companion has a minimum mass of 0.3 solar masses, and we have identified a $V sim 20$ variable optical counterpart in data from several surveys. The phasing of its $sim 1$~mag modulation at the orbital period suggests highly efficient and asymmetric heating by the pulsar wind, which may be due to an intrabinary shock that is distorted near the companion, or to the companions magnetic field channeling the pulsar wind to specific locations on its surface. We also present gamma-ray spectral analysis of the source and preliminary results from searches for gamma-ray pulsations using the radio ephemeris.
We report on the second AGILE multiwavelength campaign of the blazar 3C 454.3 during the first half of December 2007. This campaign involved AGILE, Spitzer, Swift,Suzaku,the WEBT consortium,the REM and MITSuME telescopes,offering a broad band coverage that allowed for a simultaneous sampling of the synchrotron and inverse Compton (IC) emissions.The 2-week AGILE monitoring was accompanied by radio to optical monitoring by WEBT and REM and by sparse observations in mid-Infrared and soft/hard X-ray energy bands performed by means of Target of Opportunity observations by Spitzer, Swift and Suzaku, respectively.The source was detected with an average flux of~250x10^{-8}ph cm^-2s^-1 above 100 MeV,typical of its flaring states.The simultaneous optical and gamma-ray monitoring allowed us to study the time-lag associated with the variability in the two energy bands, resulting in a possible ~1-day delay of the gamma-ray emission with respect to the optical one. From the simultaneous optical and gamma-ray fast flare detected on December 12, we can constrain the delay between the gamma-ray and optical emissions within 12 hours. Moreover, we obtain three Spectral Energy Distributions (SEDs) with simultaneous data for 2007 December 5, 13, 15, characterized by the widest multifrequency coverage. We found that a model with an external Compton on seed photons by a standard disk and reprocessed by the Broad Line Regions does not describe in a satisfactory way the SEDs of 2007 December 5, 13 and 15. An additional contribution, possibly from the hot corona with T=10^6 K surrounding the jet, is required to account simultaneously for the softness of the synchrotron and the hardness of the inverse Compton emissions during those epochs.
Thorstensen (2020) recently argued that the cataclysmic variable (CV) LAMOST J024048.51+195226.9 may be a twin to the unique magnetic propeller system AE Aqr. If this is the case, two predictions are that it should display a short period white dwarf spin modulation, and that it should be a bright radio source. We obtained follow-up optical and radio observations of this CV, in order to see if this holds true. Our optical high-speed photometry does not reveal a white dwarf spin signal, but lacks the sensitivity to detect a modulation similar to the 33-s spin signal seen in AE Aqr. We detect the source in the radio, and measure a radio luminosity similar to that of AE Aqr and close to the highest so far reported for a CV. We also find good evidence for radio variability on a time scale of tens of minutes. Optical polarimetric observations produce no detection of linear or circular polarization. While we are not able to provide compelling evidence, our observations are all consistent with this object being a propeller system.
We report results of the 2006 April multi-wavelengths campaign of SS 433, focusing on X-ray data observed with Suzaku at two orbital phases (in- and out-of- eclipse) and simultaneous optical spectroscopic observations. By analyzing the Fe25 K_alpha lines originating from the jets, we detect rapid variability of the Doppler shifts, dz/dt ~ 0.019/0.33 day^-1, which is larger than those expected from the precession and/or nodding motion. This phenomenon probably corresponding to jitter motions observed for the first time in X-rays, for which significant variability both in the jet angle and intrinsic speed is required. From the time lag of optical Doppler curves from those of X-rays, we estimate the distance of the optical jets from the base to be ~(3-4) times 10^14 cm. Based on the radiatively cooling jet model, we determine the innermost temperature of the jets to be T_0 = 13 +/- 2 keV and 16 +/- 3 keV (the average of the blue and red jets) for the out-of-eclipse and in-eclipse phase, respectively, from the line intensity ratio of Fe25 K_alpha and Fe26 K_alpha. While the broad band continuum spectra over the 5--40 keV band in eclipse is consistent with a multi-temperature bremsstrahlung emission expected from the jets, and its reflection component from cold matter, the out-of-eclipse spectrum is harder than the jet emission with the base temperature determined above, implying the presence of an additional hard component.
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