Some recent results on extragalactic X-ray sources from the Einstein observatory

Extragalactic research studies by the Harvard/Smithsonian group with the Einstein Observatory have emphasized quasars and clusters of galaxies. More than 100 QSO's have been detected, including 20 serendipitous discoveries. The ratio of L_x/L_o for radio loud quasars is on the average 3 times that of radio quiet ones. QSO's with a large intrinsic optical luminosity have a smaller ratio of L_x/L_o. X-ray images of clusters of galaxies reveal a variety of morphological types which may correspond to different stages in their evolution. Several examples of bi-modal clusters have been discovered. An X-ray plume associated with M86 is apparently gas being stripped. From X-ray studies, a mass between 1.7 × 10¹³M_θ and 4.0 × 10¹³ M_θ has been derived for M87.     

X射线选择类星体的一些性质

本文对109个X射线选择的类星体和114个射电及光学选择的类星体进行统计分析.发现在它们的红移、光学光度以及平均光学-X射线谱指数的直方分布图上, X射线选择类星体统计上都分布在这些参数图的低端.在所有样品的单色X射线光度l_X与单色光学光度l_O的关系图上, X射线选择类星体绝大部分处在光学暗的低光度区域.若以lglo=31.2erg/s·Hz为分界点, 可把光学光度划分为光学亮和暗两个区域, 则发现射电及光学选择类星体在图中光学亮区内的斜率b=0.64, 在光学暗区内的斜率b=0.95, 而X射线选择类星体的b仅为0.78, 因而暗示出它们可能是类星体现象中的一个次型.      

Type I supernovae origin: “Dualistic” hypothesis

Stars that explode as Type I Supernovae (SNI) are white dwarfs with masses practically equal to the Chandrasekhar limit M_ch. These white dwarfs forme either as a result of gas overflow onto a degenerate component in a binary system or due to the evolution of nuclei of the stars whose mass, on the main sequence, was 3 to 7 M_o. The masses of their nuclei are quite close to M_ch. It is convenient to consider three types of stellar evolution 1) “hyperbolic”: masses of nuclei formed as a result of evolution are > M_ch; such evolution ends in a Type II Supernova (SNII) outburst; 2) “parabolic” - masses of nuclei ≈ M_ch, with the evolution ending in an SNI outburst; 3) “elliptical” with nuclei masses < M_ch. The latter type of evolution leads to the formation of planetary nebulae and white dwarfs. A new hypothesis is suggested that explains more frequent occurrence of SNI in irregular galaxies by flashes of star formation.     

The X-ray properties of accreting black holes

Accreting black holes in binary systems exhibit two properties that distinguish them from the vast majority of binary X-ray sources: (1) rapid ≤ 1 s variability and (2) bi-modal spectral behaviour. These findings are based primarily on the observed properties of Cyg X-1 where an estimate of the X-ray source mass from radial velocity studies indicates a mass of 10 M. The recently suggested black hole candidacy of LMC X-3 is based on a similar mass estimate. The X-ray properties are similar to those of Cyg X-1 in its “high state”. The unique spectral properties of these systems are used to search for other similar systems, and new “possible” candidates are suggested, that include several transient sources. A possible spectral connection between these systems and their more massive counterparts in AGN is discussed.     

类星体的X射线辐射研究

由爱因斯坦天文台最近观测到的273个类星体、Ⅰ型Seyfeft星系的软X射线光度(L_x为0.5—4.5keV)资料,与它们的红移z值构成一个连续序列(图1)。利用球对称吸积模型计算得到:高红移的类星体,由于其较大的吸积率,在这个序列上停留的时间较短(～106年);而低红移类星体及Ⅰ型Seyfert星系停留的时间较长(～108年)。利用现有的107个类星体的射电单色光度l_r,光学单色光度l_o以及X射线单色光度l_x的资料,讨论了类星体大尺度谱的硬度,发现类星体的光学光度有两个不同的演化阶段;文中还定性地讨论了类星体射电辐射机制不同于光学和射电辐射的机制之处。      

Observations of A0535+26 transient X-ray source

Observations of the transient X-ray A0535+26 source with the SIGNE-2MP instrument on-board the Soviet “Prognoz-6” and “Prognoz-7” satellites are considered in the paper.     

Millimeter-wave continuum observation of high-z radio quasars

Millimeter-wave continuum observations of high redshift (z3) radio loud quasars (RLQs) and radio intermediate quasars (RIQs) have been performed with the 45 m telescope of the Nobeyama Radio Observatory. Sixteen RLQs with S_5GHz > 200 mJy and nine RIQs with 200 mJy > S_5GHz > 20 mJy were observed at four millimeter-wave frequencies. All the observed quasars have synchrotron spectra and their possible dust emission component is obscured by the synchrotron emission in millimeter-wave frequencies, which can be explained by their strong AGN activities. Observed quasars are classified into three spectral classes, according to their millimeter-wave spectral index as steep spectrum, millimeter turn over and extreme flat spectrum quasars. Extreme flat spectrum quasars have relatively flat spectra up to 150 GHz, where the rest frequency is higher than 600 GHz. This is an indication that the objects are in very young stage of quasar evolution and shows higher nuclear activity than lower redshift quasars. One of the QSOs, 2358+189 previously known as a RIQ, is found to have extreme flat spectrum, and is now classified as RLQs.     

X-ray and gamma-ray observations of a white-light flare

HEAO-1 observed hard radiations (X- and gamma-rays) from a major solar flare on 11 July 1978. The observations showed gamma-ray line and continuum emission extending to the highest energy observed. The lines are identified with the 2.2 MeV line of deuterium formation and the 4.4 MeV line of inelastic scattering on ¹²C, both previously observed in the flares of August 1972 [1]. The 11 July flare was identified as a white-light flare by observations at Debrecen [2]. It thus provides the first opportunity for a detailed examination of white-light flare theories that depend upon proton heating of the photosphere. The line strength over a four-minute integration at 2.2 MeV was 1.00 ± 0.29 ph(cm² sec)⁻¹, and the gamma-ray emission (excluding the 2.2 MeV line which was appreciably delayed) lagged by less than 20 sec approximately after the hard X-ray and microwave fluxes. We conclude that the “second-stage” acceleration of high-energy solar particles must commence promptly after the impulsive phase.     

HEAO-1 and BBXRT non-source X-ray observations

A more appropriate title for this talk would have been “Measurements of Large Scale Structure from X-ray Background Fluctuations”. While it has long been recognized that the X-ray Background (XRB) is primarily of a cosmological origin (with z < a few), it has recently become apparent that surface brightness fluctuations in the surveys of the XRB can be used to trace the distribution of matter in much the same way as complete catalogs of individual objects. The distance which is probed is related to the angular resolution of the detector; for the HEAO-1 A2 experiment, which provides the best all-sky data base for the XRB in the 2–20 keV band, the effective depth is a few 100 Mpc.     

类星体X射线辐射的性质

本文对247个类星体的X射线性质进行了统计分析,这些X射线资料是由爱因斯坦卫星在0.5—4.5keV的能带内观测到的。主要结果是:在各种视亮度和红移(或距离)的已知1619个类星体中,都有百分比相近的部分为X射线源。Ⅰ型Seyferc星系的发射线H_β与[OⅢ]的等值宽度比R_EW同X射线光度L_x强相关,这可作为Ⅰ型Seyfert星系的X射线光度的一个新指标。光学辐射以及2.5GHz以上的高频射电辐射都同X射线辐射相关,说明这三种辐射的区域依次相邻而且机制也相似。色指数U-B和B-V都同X射线辐射不相关,但U-B同B-V弱相关。      

Free librations of the two-layer Moon and the possibilities of their detection

Based on the forthcoming second stage of the Japanese Lunar mission ILOM (2013), when an optical telescope will be set on the surface near one of the Lunar poles, the possibility to detect free Lunar modes (Chandler-like wobble and free-core nutation) is considered. The difference between the Lunar Eulerian and Chandler-like wobble is explained. The terms “arbitrary libration” and “free libration” are discussed. The geometrical and physical interpretations of the free polar motion over the Lunar surface are considered from the viewpoints of Lunar surface-based observations and the Lunar Navigation Almanac. The dependencies of the free libration period on the core’s radius, density, and ellipticity are modelled and discussed.     

Prognoz-6 data about ultraviolet sky background in dark and Milky Way regions of the sky

Ultraviolet spectra (1100–1900 Å) of the sky background of 10 wide angle (6°×6°) regions obtained between 70 000 km and 200 000 km from the Earth with the photoelectric spectrometer “GALACTIKA” on board the satellite “PROGNOZ-6” are considered. The spectral energy distribution of the sky background, after subtraction of the stellar component, is similar for regions on both sides of the Milky Way and exhibits a strong U.V. light contribution. On the contrary, the Milky Way (l_II=190° b_II=+6°) is less rich in far U.V. light; this can be related to the predominance of an expected selective absorption near the galactic plane. The nature of U.V. excess at high galactic latitudes needs further investigations.     

The dark matter halo structure of “fossil” groups candidates

We investigated properties of four isolated giant elliptical galaxies with extended X-ray halo using ASCA data. The derived size of X-ray halo, X-ray luminosity, and gravitational mass of the dark halo are unusually large those of X-ray halo of a single galaxy, but are typical for X-ray halos of groups and poor clusters of galaxies. The measured temperatures and abundances of the X-ray halo gas in these galaxies are also similar to those of the groups and poor clusters. Based on these results we identified these galaxies as “isolated X-ray overluminous elliptical galaxy” (IOLEG). The radial profiles of dark halo in these objects were derived from X-ray data. It is found that some are similar to those of compact groups while others are the same as those of normal ellipticals. The dark halos of lOLEGs are thus indistinguishable from those of groups (and poor clusters), which appears to be consistent with a widely believed idea that lOLEGs are a product of dynamical evolution of a compact group. However, mass-to-light ratios of IOLEGs (M₂₀₀/L_B  100–1000) are far greater than those of Hickson compact groups M₂₀₀/L_B  40–60). Since it is hard to consider that total optical luminosity of a compact group decreases by an order of magnitude in the course of dynamical evolution, such difference in the observed mass-to-light ratio between IOLEGs and Hickson compact groups strongly suggests that most IOLEGs have not evolved from compact groups which are observed at present.     

Gamma rays from accreting matter onto collapsed objects

In the spherical accretion onto massive objects, the matter may be heated up to temperatures as high as 10¹² °K. In such a hot plasma, the thermal bremsstrahlung (e-e and e-p) and π° decay from inelastic collisions of protons are the main γ-ray sources. We determined the γ -ray production spectra from the π° decay and from bremsstrahlung for different temperatures. The expected γ-ray spectra were evaluated too in order to fit experimental data. We have fitted COS B data from 3C 273 using a two temperatures plasma model. The best fit is for

Full-size image (1K)

(M₈ is the black hole mass in 10⁸ M) which gives . The hard X-ray measurements do not contradict the bremsstrahlung spectrum.     

ROSAT all-sky-survey detections of classical novae and related objects

In the ROSAT all-sky-survey 7 classical novae were detected, but only 1 of the 26 that had an outburst in the 10 years before the survey. 3 are new X-ray detections; 1 source is a known intermediate polar and 4 are suspect “magnetic novae”. 3 objects show a very soft spectrum. Among the objects related to novae we found 2 dwarf-novae with unusually long periodicity, the peculiar source KR Aur and 4 X-ray novae. One of these, V404 Cyg, was detected at quiescence for the first time.     

New magnetodynamic principles in cosmic physics

The effect of gravity on super-escape particles spiralling along magnetic field lines need not be negligible when the field lines are long enough and the field-strength variation small. If the magnetic field strength decreases with altitude but only very slowly, some unexpected phenomena may occur owing to gravity: some super-high-velocity particles can possess an upper level of reflection which impedes their escape into higher regions. Some of these “super-escape particles may, however, propagate through the level at which their pitch angle is 90° and continue spiralling in the same direction (“hole” boundary). In addition, the pitch angle of some super-escape particles may only achieve a maximum which can be very small (hole effect). Many plasma phenomena can be derived from these charecteristic features of particle trajectories.     

A study of a complete soft X-ray selected sample of AGN

We present preliminary results from analyses of hard X-ray and optical observations of a soft X-ray selected sample. We created a small but complete sample with 20 of the softest and brightest objects with low Galactic absorption from the ROSAT bright soft X-ray selected radio-quiet AGN sample. This sample consists of 10 narrow-line Seyfert 1 galaxies and 10 broad-line Seyfert galaxies. We analyze ASCA data in the 0.6–10 keV band and optical spectra from ground-based telescopes. We investigate the photon indices in the hard X-ray band, soft excesses in the ASCA band, and optical emission line properties. The photon indices in the 2–10 keV band are nominal for both narrow-line Seyfert 1 galaxies and broad-line Seyfert 1 galaxies in each class compared with other heterogeneous samples. All of the narrow-line Seyfert 1 galaxies show soft excesses, but this component seems to be less significant for broad-line Seyfert 1 galaxies. There seems to be a trend of steeper X-ray spectra to be accompanied by narrower Hβ for narrow-line Seyfert 1 galaxies, but this is not extended to the larger velocity width regime of broad-line Seyfert 1 galaxies, and no clear trend is seen among them.     

X-ray synchrotron nebulae and the origin of neutron stars

“With all reserve, we advance the view that a supernova represents the transition of an ordinary star into a neutron star.”This conclusion, reached just 50 years ago in a classic paper by Walter Baade and Fritz Zwicky (1934), was published three decades before the first direct observational evidence for the existence of neutron stars was uncovered. It still informs the standard picture of neutron star production in the Galaxy. We examine herein some recent evidence bearing on this question which has been derived from Observatory X-ray observations of supernova remnants and radio pulsars. In particular, the discovery that X-ray synchrotron nebulae are found surrounding most young ( 10⁶ yr) pulsars observed to date is discussed. We explore the implications of the lack of such nebulae in the majority of supernova remnants (SNR) for the properties and frequency of neutron star formation in supernova events.     

X-ray observations of high-z radio loud/quiet quasars

It is widely recognized that a knowledge of the X-ray properties of high-z radio loud/quiet quasars (RLQs/RQQs) would have important consequences for probing the conditions of the early Universe, studying the evolution of quasars, and assessing quasar contributions to the CXB. In distant active galactic nuclei (AGN) we can detect only the quasars having high luminosities or collimated beams with current X-ray astronomy satellites. We have also detected more than ten RLQs above z=2 with ASCA. We have observed 8 high z RQQs above z=2, but have not detected the higher z RQQs, above z=2.5. A considerable fraction of the high z RLQs show excess absorption over Galactic column densities, while most high z RQQs do not indicate excess absorption, although the samples are small. The X-ray photon index of RLQs is smaller than that of RQQs. The two RLQs above z=4 are very flat, suggesting that they are blazar-like AGN. A long term observation of RQQ, H1400#10 (z=2.078) did not indicate an Fe Kα emission line, giving a weaker upper limit than a typical line intensity of Seyfert 1 galaxies.