Infrared–red cores in nearby elliptical galaxies

We present the Spitzer Space Telescope Infrared Array Camera observations for a sample of local elliptical galaxies to study later stages of active galactic nucleus (AGN) activity. A sample of 36 elliptical galaxies is selected from the Palomar spectroscopic survey. We detect nuclear non-stellar infrared emission in nine of them. There is unambiguous evidence of circumnuclear dust in these nine galaxies in their optical images. We also find a remarkable correlation between the infrared excess emission and the nuclear radio/X-ray emission, suggesting that infrared excess emission is tightly related to nuclear activity. The possible origin of infrared excess emission from hot dust heated by the central AGN is supported by the spectral indices of the infrared excess emission.     

Statistical Studies on the Excess Peak Flux in Soft X-rays and EUV Bands from Solar Flares

Based on the solar X-ray data in the band of 0.1??C?0.8?nm observed by Geostationary Operational Environmental Satellites (GOES), the XUV and EUV data in the bands of 26??C?34?nm and 0.1??C?50?nm observed by the Solar EUV Monitor (SEM) onboard the Solar and Heliospheric Observatory (SOHO), a statistical analysis on the excess peak flux (the pre-flare flux is subtracted) in two SEM bands during M- and X-class flares from 1998 to 2007 is given. The average ratio of the excess peak flux to the pre-flare flux for the M-class flares is 5.5?%±3.7?% and that for the X-class flares is 16?%±11?%. The excess peak fluxes in two SEM bands are positively correlated with the X-ray flare class; with the increase in the X-ray flare class, the excess peak flux in two SEM bands increases. However, a large dispersion in the excess peak flux in the SEM bands and their ratio is found for the same X-ray flare class. The relationship between the excess peak fluxes of the two SEM bands also shows large dispersion. It is considered that the diversity we found in the flare spectral irradiance is caused by many variable factors related to the structure and evolution of solar flares.     

The optical/ultraviolet excess of isolated neutron stars in the resonant cyclotron scattering model

X-ray dim isolated neutron stars are peculiar pulsar-like objects,characterized by their Planck-like spectrum.In studying their spectral energy distributions,optical/ultraviolet(UV) excess is a long standing problem.Recently Kaplan et al.measured the optical/UV excess for all seven sources,which is understandable in the resonant cyclotron scattering(RCS) model previously addressed.The RCS model calculations show that the RCS process can account for the observed optical/UV excess for most sources.The ?at spe...     

Galaxies with a UV excess in which supernovae have been observed

A list of galaxies with a UV excess in which at least one supernova (SN) has exploded is compiled. Distributions of the linear distances of SN in synthetic galaxies are obtained, constructed for galaxies with a UV excess and normal galaxies. It is shown that SN activity is the same in galaxies with a UV excess and in normal galaxies. Translated from Astrofizika, Vol. 40, No. 3, pp. 457–472, August, 1997.     

A binary model for the UV-upturn of elliptical galaxies

The discovery of a flux excess in the far-ultraviolet (FUV) spectrum of elliptical galaxies was a major surprise in 1969. While it is now clear that this UV excess is caused by an old population of hot helium-burning stars without large hydrogen-rich envelopes, rather than young stars, their origin has remained a mystery. Here we show that these stars most likely lost their envelopes because of binary interactions, similar to the hot subdwarf population in our own Galaxy. We have developed an evolutionary population synthesis model for the FUV excess of elliptical galaxies based on the binary model developed by Han et al. for the formation of hot subdwarfs in our Galaxy. Despite its simplicity, it successfully reproduces most of the properties of elliptical galaxies with a UV excess: the range of observed UV excesses, both in  (1550 − V )  and  (2000 − V )  , and their evolution with redshift. We also present colour–colour diagrams for use as diagnostic tools in the study of elliptical galaxies. The model has major implications for understanding the evolution of the UV excess and of elliptical galaxies in general. In particular, it implies that the UV excess is not a sign of age, as had been postulated previously, and predicts that it should not be strongly dependent on the metallicity of the population, but exists universally from dwarf ellipticals to giant ellipticals.     

Radiation loss and mechanical heating in the low solar chromosphere

We discuss Ulmschneider's claim to have established that the short-period acoustic wave energy input is the only one able to balance the chromospheric radiation loss. We first review the range of uncertainty in empirical and radiative equilibrium models, on which estimates of the excess radiation coming from mechanical heating rest. We then show that Ulmschneider's estimate of this excess radiation from such models uses an over-simplified computational method. The resultant of uncertainty in models and in computational methods suggests that Ulmschneider's results on excess radiation from heating in the low chromosphere is subject to overestimation by an order of magnitude.     

Simultaneous infrared and H-alpha measurements of Be stars

The observed infrared excess in Be stars is usually interpreted as free-free and free-bound emission from a hot gas envelope around the Be star. This hot gas should also emit H-alpha line radiation. Earlier observations had suggested that the infrared excess and Hα radiation were not consistent with models in which they arise from the same ionized region; however the observations were made at different times. We have made simultaneous observation of infrared and H-alpha line radiation. Our observations imply that either both these radiations cannot arise from the same hot gas or additional processes have to be invoked to account for the observed excess infrared radiation.     

39Ar‐40Ar dating of the Zagami Martian shergottite and implications for magma origin of excess 40Ar

Abstract— The Zagami shergottite experienced a complex, petrogenetic formation history (McCoy et al. 1992, 1999). Like several shergottites, Zagami contains excess ⁴⁰Ar relative to its formation age. To understand the origin of this excess ⁴⁰Ar, we made ³⁹Ar‐⁴⁰Ar analyses on plagioclase and pyroxene minerals from two phases representing different stages in the magma evolution. Surprisingly, all these separates show similar concentrations of excess ⁴⁰Ar, ?1 × 10^?6 cm³/g. We present arguments against this excess ⁴⁰Ar having been introduced from the Martian atmosphere as impact glass. We also present evidence against excess ⁴⁰Ar being a partially degassed residue from a basalt that actually formed ?4 Gyr ago. We utilize our experimental data on Ar diffusion in Zagami and evidence that it was shock‐heated to only ?70 °C, and we assume this heating occurred during an ejection from Mars ?3 Myr ago. With these constraints, thermal considerations necessitates either that its ejected mass was impossibly large, or that its shock‐heating temperature was an order of magnitude higher than that measured. We suggest that this excess ⁴⁰Ar was inherited from the Zagami magma, and that it was introduced into the magma either by degassing of a larger volume of material or by early assimilation of old, K‐rich crustal material. Similar concentrations of excess ⁴⁰Ar in the analyzed separates imply that this magma maintained a relatively constant ⁴⁰Ar concentration throughout its crystallization. This likely occurred through volatile degassing as the magma rose toward the surface and lithostatic pressure was released. These concepts have implications for excess ⁴⁰Ar in other shergottites.     

Circular polarization and the structure of compact extragalactic radio sources

The origin of the circularly polarized (CP) component of the synchrotron radiation in compact extragalactic radio sources is investigated. A convenient quantity, the CP excess, is defined as the ratio of the observed to the expected degree of CP in a source, with the latter calculated from synchrotron theory for transparent sources, using magnetic field strengths from VLBI measurements, and the degree of inhomogeneity estimated from the observed degree of linear polarization. For almost all sources, the CP excess is much larger than unity, and in addition appears to depend on the absolute luminosity of the source for both the radio galaxy and the quasar populations. Explanations for the amount and the luminosity dependence of the CP excess are considered, and the origin of the excess is suggested to lie in a special magnetic field geometry of the compact sources. A simple model with helical magnetic field and relativistic beaming, consistent with the quasar data, is presented. The importance of considering the CP component of radiation in the context of different physical source models is emphasized.     

与发射线区成协的类星体CIV吸收系统研究(Ⅱ)统计研究(1)

本文是系列文章的第二篇,我们在文(1)建立的均匀无偏的CIV吸收线样本的基础上,对该样本进行了统计检验和分析,结果支持成协系统的出现频率比非成协系统有明显的过超.而这种过超现象几乎和类星体的射电性质无关.但不同射电性质的类星体成协吸收出现频率随z_(em)的变化不尽相同.这种随z_(em)的变化可能反映了各种类星体,特别是射电类星体与环境相互作用的演化效应.但我们的样本中高红移射电类星体较少,因此非常需要获得更大的高红移射电类星体样本,以检验我们的结果.     

A relation between ultraviolet excess and superficial gravity for Cepheids

A linear relation is calculated between the six-colour ultraviolet excess and superficial gravity for Cepheid variables. This excess appears to be a sensitive indicator of gravity behaviour for these stars.On leave from Departamento de Astronomia, Instituto Astronômico e Geofisico da Universidade de São Paulo, Brasil.     

Asymmetric lepton production in a universe with non-zero baryon number

It is pointed out that as a result of processes during different stages of stellar evolution a universe with a net baryon number develops during a Hubble age an excess of neutrinos over antineutrinos of the same order as the observed relative strength of CP violation. The same processes also favour excess positron production.     

Properties of the continua of eight PG QSOs from ASCA data

We have analyzed the continua of eight PG QSOs, obtained by the ASCA SIS detector with a higher energy resolution and a broader band than by ROSAT/PSPC and attempted to fit the data with a single power law, a double power law and a truncated power law. Four of the objects exhibit soft X excess in 0.4 – 10 keV. They are Mkn 478, PG 1444+407, PG 1543+48 and 3C 273. Furthermore, the ratio of the excess to total flux is the smaller, the greater the optical luminosity is. The presence or otherwise of the soft X-ray excess is unrelated to the radio properties and luminosity of the object.     

On the electrization caused by the gravitation of a massive body

The excess charge in the core of a heavy body (and the excess opposite charge at its surface) resulting from the action of gravitation is determined.Translated from Astrofizika, Vol. 39, No. 3, pp. 467–474, July–September, 1996.     

Detection of Polarized Millimeter and Submillimeter Emission from Sagittarius A*

We report the detection of linear polarization from Sgr A* at 750, 850, 1350, and 2000 μm which confirms the contribution of synchrotron radiation. From the lack of polarization at longer wavelengths, it appears to arise in the millimeter/submillimeter excess. There are large position angle changes between the millimeter and submillimeter results, and these are discussed in terms of a polarized dust contribution in the submillimeter and various synchrotron models. In the model that best explains the data, the synchrotron radiation from the excess is self-absorbed in the millimeter region and becomes optically thin in the submillimeter. This implies that the excess arises in an extremely compact source of approximately 2 Schwarzschild radii.     

Extinction techniques and impact on dust property determination

The near-infrared (NIR) extinction power-law index (β) and its uncertainty is derived from three different techniques based on star counts, colour excess and a combination of them. We have applied these methods to Two Micron All Sky Survey (2MASS) data to determine maps of β and NIR extinction of the small cloud IC 1396 W. The combination of star counts and colour excess results in the most reliable method to determine β. It is found that the use of the correct β map to transform colour excess values into extinction is fundamental for column density profile analysis of clouds. We describe how artificial photometric data, based on the model of stellar population synthesis of the Galaxy, can be used to estimate uncertainties and derive systematic effects of the extinction methods presented here. We find that all colour excess based extinction determination methods are subject to small but systematic offsets, which do not affect the star counting technique. These offsets occur since stars seen through a cloud do not represent the same population as stars in an extinction-free control field.     

Spin rate distribution of small asteroids

The spin rate distribution of main belt/Mars crossing (MB/MC) asteroids with diameters 3-15 km is uniform in the range from f=1 to 9.5 d⁻¹, and there is an excess of slow rotators with f<1 d⁻¹. The observed distribution appears to be controlled by the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. The magnitude of the excess of slow rotators is related to the residence time of slowed down asteroids in the excess and the rate of spin rate change outside the excess. We estimated a median YORP spin rate change of ≈0.022 d⁻¹/Myr for asteroids in our sample (i.e., a median time in which the spin rate changes by 1 d⁻¹ is ≈45 Myr), thus the residence time of slowed down asteroids in the excess is ≈110 Myr. The spin rate distribution of near-Earth asteroids (NEAs) with sizes in the range 0.2-3 km (∼5 times smaller in median diameter than the MB/MC asteroids sample) shows a similar excess of slow rotators, but there is also a concentration of NEAs at fast spin rates with f=9-10 d⁻¹. The concentration at fast spin rates is correlated with a narrower distribution of spin rates of primaries of binary systems among NEAs; the difference may be due to the apparently more evolved population of binaries among MB/MC asteroids.     

Precise wideband photometry of photospheric faculae with an emphasis on the disk center

The center-to-limb variation of the excess intensity in faculae was obtained for 266 active regions with an accuracy of 10^–3. For this observation full-disk images were obtained with a rotating one-dimensional diode array whose rotation axis was set at the disk center, at the wavelength of 5450 Å with a bandpass of 400 Å. From the center-to-limb variation of excess intensity of active regions the excess effective temperature was found to be 6.4 K on the average where the mean longitudinal magnetic field is 65 G as measured by 5233 Å line. In other words the ratio of the excess radiative flux to the total flux was 0.44% on the average for the present measurements of low spatial resolution of 20.The average excess intensity for 60 active regions near the disk center was found to be 4 × 10^–4 of the quiet Sun intensity. This very low excess brightness averaged over the whole active region, in contrast to the reported high excess brightness of facular points (diameter 0.2) of 0.4, leads to a hypothesis that the background in between facular points in the active region is darker than the true quiet photosphere by 1%. It is further surmised that the inferred darkness of intra facular points is due to partial compensation for excess total irradiance of facular points. This interpretation is also consistent with previous observations of the contrast of facular points near the limb.     

Preliminary observation of missing energy flux of sunspot

We have searched for the missing energy flux of the sunspot by measuring white-light photographs over the region around the sunspots exceeding ten times of the diameter of spots. It was found that the excess brightness amounts to 0.3–0.8% of the local continuum intensity immediately beyond the penumbra and smoothly decrease to zero at the edge of our inspected radii of 130 000–160000km. This result suggests that the flux deficit in sunspots of the order of 30% over the umbra-penumbra is roughly the same as the excess flux found in the very large surrounding region which includes photospheric facular contributions. Among nineteen spots fourteen showed this extended bright ring. Narrow band photoelectric scans revealed that the excess radiation originates in the continuum, not from weakened absorption lines.     

New Evidence on the Excess Redshift of Companion Galaxies

Three recent studies have furnished strong observational confirmation that companion galaxies have significant excess redshifts. In the best studied groups and clusters of galaxies, the new evidence shows that smaller, hydrogen rich or later type companions have excess redshifts of the order of +200 km s^-1 or more. This revised version was published online in July 2006 with corrections to the Cover Date.