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Register a new userSpectral observations of X Persei: Connection between H-alpha and X-ray emission
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Radoslav K. Zamanov
Publication date
2018
fields
Physics
and research's language is
English
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We present spectroscopic observations of the Be/X-ray binary X Per obtained during the period 1999 - 2018. Using new and published data, we found that during disc-rise the expansion velocity of the circumstellar disc is 0.4 - 0.7 km/s. Our results suggest that the disc radius in recent decades show evidence of resonant truncation of the disc by resonances 10:1, 3:1, and 2:1, while the maximum disc size is larger than the Roche lobe of the primary and smaller than the closest approach of the neutron star. We find correlation between equivalent width of H-alpha emission line ($Walpha$) and the X-ray flux, which is visible when $15 : AA : < Walpha le 40 : AA$. The correlation is probably due to wind Roche lobe overflow.
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The impact of ram pressure stripping (RPS) on galaxy evolution has been studied for over forty years. Recent multi-wavelength data have revealed many examples of galaxies undergoing RPS, often accompanied with multi-phase tails. As energy transfer in the multi-phase medium is an outstanding question in astrophysics, RPS galaxies are great objects to study. Despite the recent burst of observational evidence, the relationship between gas in different phases in the RPS tails is poorly known. Here we report, for the first time, a strong linear correlation between the X-ray surface brightness (SB$_{rm X}$) and the H$alpha$ surface brightness (SB$_{rm Halpha}$) of the diffuse gas in the RPS tails at $sim$ 10 kpc scales, as SB$_{rm X}$/SB$_{rm Halpha} sim$ 3.6. This discovery supports the mixing of the stripped interstellar medium (ISM) with the hot intracluster medium (ICM) as the origin of the multi-phase RPS tails. The established relation in stripped tails, also in comparison with the likely similar correlation in similar environments like X-ray cool cores and galactic winds, provides an important test for models of energy transfer in the multi-phase gas. It also indicates the importance of the H$alpha$ data for our understanding of the ICM clumping and turbulence.
We present results from an H-alpha monitoring campaign of the Be X-ray binary systems HDE 245770 = A 0535+26 and X Per. We use the H-alpha equivalent widths together with adopted values of the Be star effective temperature, disk inclination, and disk outer boundary to determine the half-maximum emission radius of the disk as a function of time. The observations of HDE 245770 document the rapid spectral variability that apparently accompanied the regeneration of a new circumstellar disk. This disk grew rapidly during the years 1998 - 2000, but then slowed in growth in subsequent years. The outer disk radius is probably truncated by resonances between the disk gas and neutron star orbital periods. Two recent X-ray outbursts appear to coincide with the largest disk half-maximum emission radius attained over the last decade. Our observations of X Per indicate that its circumstellar disk has recently grown to near record proportions, and concurrently the system has dramatically increased in X-ray flux, presumably the result of enhanced mass accretion from the disk. We find that the H-alpha half-maximum emission radius of the disk surrounding X Per reached a size about six times larger than the stellar radius, a value, however, that is well below the minimum separation between the Be star and neutron star. We suggest that spiral arms excited by tidal interaction at periastron may help lift disk gas out to radii where accretion by the neutron star companion becomes more effective.
We present spectroscopic observations of the Be/X-ray binary X Per obtained during the period December 2017 - January 2020 (MJD~58095 - MJD~58865). In December 2017 the $Halpha$, $Hbeta$, and HeI 6678 emission lines were symmetric with violet-to-red peak ratio $V/R approx 1$. During the first part of the period (December 2017 - August 2018) the V/R-ratio decreased to 0.5 and the asymmetry developed simultaneously in all three lines. In September 2018, a third component with velocity $approx 250$~km~s$^{-1}$ appeared on the red side of the HeI line profile. Later this component emerged in $Hbeta$, accompanied by the appearance of a red shoulder in $Halpha$. Assuming that it is due to an eccentric wave in the circumstellar disc, we find that the eccentric wave appeared first in the innermost part of the disc, it spreads out with outflowing velocity $v_{wave} approx 1.1 pm 0.2 $~km~s$^{-1}$, and the eccentricity of the eccentric wave is $e_{wave} approx 0.29 pm 0.07$. A detailed understanding of the origin of such eccentricities would have applications to a wide range of systems from planetary rings to AGNs.
The energy and spectral shape of radio bursts may help us understand the generation mechanism of solar eruptions, including solar flares, CMEs, eruptive filaments, and various scales of jets. The different kinds of flares may have different characteristics of energy and spectral distribution. In this work, we selected 10 mostly confined flare events during October 2014 to investigate their overall spectral behavior and the energy emitted in microwaves by using radio observations from microwaves to interplanetary radio waves, and X-ray observations of GOES, RHESSI, and Fermi/GBM. We found that: All the confined flare events were associated with a microwave continuum burst extending to frequencies of 9.4 - 15.4 GHz, and the peak frequencies of all confined flare events are higher than 4.995 GHz and lower than or equal to 17 GHz. The median value is around 9 GHz. The microwave burst energy (or fluence) as well as the peak frequency are found to provide useful criteria to estimate the power of solar flares. The observations imply that the magnetic field in confined flares tends to be stronger than that in 412 flares studied by Nita et al. 2004. All 10 events studied did not produce detectable hard X-rays with energies above 300 keV indicating the lack of efficient acceleration of electrons to high energies in the confined flares.
We present a comprehensive flux resolved spectral analysis of the bright Narrow line Seyfert I AGNs, Mrk~335 and Ark~564 using observations by XMM-Newton satellite. The mean and the flux resolved spectra are fitted by an empirical model consisting of two Comptonization components, one for the low energy soft excess and the other for the high energy power-law. A broad Iron line and a couple of low energies edges are required to explain the spectra. For Mrk~335, the 0.3 - 10 keV luminosity relative to the Eddington value, L{$_{X}$}/L$_{Edd}$, varied from 0.002 to 0.06. The index variation can be empirically described as $Gamma$ = 0.6 log$_{10}$ L{$_{X}$}/L$_{Edd}$ + 3.0 for $0.005 < L{_{X}}/L_{Edd} < 0.04$. At $ L_{{X}}/L_{Edd} sim 0.04$ the spectral index changes and then continues to follow $Gamma$ = 0.6 log$_{10}$ L$_{{X}}$/L$_{Edd}$ + 2.7, i.e. on a parallel track. We confirm that the result is independent of the specific spectral model used by fitting the data in the 3 - 10 keV band by only a power-law and an Iron line. For Ark~564, the index variation can be empirically described as $Gamma$ = 0.2 log$_{10}$ L$_{{X}}$/L$_{Edd}$ + 2.7 with a significantly large scatter as compared to Mrk~335. Our results indicate that for Mrk~335, there may be accretion disk geometry changes which lead to different parallel tracks. These changes could be related to structural changes in the corona or enhanced reflection at high flux levels. There does not seem to be any homogeneous or universal relationship for the X-ray index and luminosity for different AGNs or even for the same AGN.
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