An Overview of the Veritas Prototype Telescope and Camera

The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is the next-generation ground-based gamma-ray observatory that is being built in southern Arizona by a collaboration of 10 institutions in Canada, Ireland, the UK and the USA. VERITAS is designed to operate in the range from 50 GeV to 50 TeV with optimal sensitivity near 200 GeV; it will effectively overlap with the next generation of space-based gamma-ray telescopes. The first phase of VERITAS, consisting of four telescopes of 12 m aperture, will be operational by the time of the GLAST launch in 2007. Eventually, the array will be expanded to include the full array of seven telescopes on a filled hexagonal grid of side 80 m. A prototype VERITAS telescope with a reduced number of mirrors and signal channels has been built. Its design and performance is described here. The prototype is scheduled to be upgraded to a full 499 pixel camera with 350 mirrors during the autumn of 2004. The VERITAS collaboration consists of universities and institutions from Ireland, UK, USA and Canada. See for a full listing.     

A low density of the extragalactic background light revealed by the H.E.S.S. spectra of the BL Lac objects 1ES 1101-232 and H 2356-309

The study of the TeV emission from extragalactic sources is hindered by the uncertainties on the diffuse Extragalactic Background Light (EBL). The recent H.E.S.S. results on the blazars 1ES 1101-232 and H 2356-309 represent a breakthrough on this issue. Their unexpectedly hard spectra allow an upper limit to be derived on the EBL in the optical/near-infrared range, which is very close to the lower limit given by the resolved galaxy counts. This result seems to exclude a large contribution to the EBL from other sources (e.g. Population III stars) and indicates that the intergalactic space is more transparent to γ-rays than previously thought. A discussion of EBL absorption effects and further observational tests with Cherenkov telescopes are presented. For the H.E.S.S. collaboration.     

Dense Molecular Gas Around Protostars and in Galactic Nuclei: Pdrs and Xdrs

The chemical and thermal structure of dense gas irradiated by FUV and X-ray photons is explored. The relevance of these so-called PDRs (FUV) and XDRs (X-ray) for AGN and YSOs is discussed. Observational line diagnostics and chemical tracers are summarized.     

Rolling down from the 30 keV peak: Modelling the Hard X-Ray and γ-Ray Backgrounds

We will briefly discuss the importance of sensitive X-ray observations above a few tens of keV for a better understanding of the physical mechanisms associated to the Supermassive Black Hole primary emission in both radio quiet and radio loud AGN and to the cosmological evolution of the most obscured sources.     

Fine structure of the BL Lac object 1803+784

We have investigated the superfine structure of the BL Lac object 1803+784, determined the ejector location, the helical structure of the jet, its parameters and relationship to the precession and nutation of the ejector rotation axis, and established the relationship to the periods of enhanced nuclear activity. The multimode precession is shown to be produced by the reactive action of the ejected relativistic plasma flow. The visibility of helix-structure fragments is determined by the transparency of the surrounding thermal plasma—the cocoon wall. The absorption in the cocoon wall has been found to depend on the distance from the core. The absorption of the synchrotron radio emission from the ejector region at 18 cm reaches ～30 dB. The spectra of the compact components located near the core have a low-frequency cutoff that is determined by the reabsorption of the synchrotron emission and by the absorption in the cocoon wall. The spectral index of the low-frequency part is α = 3.1–4.2.     

ESO 113-G010的一对准周期振荡信号

2005年11月XMM-Newton望远镜对窄线赛弗特星系ESO 113-G010进行了长达100 ks的观测.采用Lomb-Scargle周期图(LSP)法和加权小波Z变换(Weighted Wavelet Z-transform,WWZ)两种方法对数据进行分析,发现存在着～2.24 11和～4.09 h准周期振荡(Quasi-Periodic Oscillation,QPO),其置信度分别为7.3σ和4.8σ.这两个QPO信号的周期具有大约1:2 (1:1.83)的关系.在该源的其他的观测中并没有发现QPO信号,表明这是一种暂现现象.ESO 113-G010中心黑洞的质量MBH和其QPO频率f_(QPO)满足已知的从恒星级黑洞到超大质量黑洞的质量与QPO频率之间的对数线性关系.该源的能谱分析显示在1 keV以下有软X射线超的现象.     

Stellar And Galactic Environment survey (SAGE)

This paper describes a proposed high resolution soft X-ray and Extreme Ultraviolet spectroscopy mission to carry out a survey of Stellar and Galactic Environments (SAGE). The payload is based on novel diffraction grating technology which has already been proven in a sub-orbital space mission and which is ready to fly on a satellite platform with minimal development. We discuss the goals of a SAGE base-line mission and demonstrate the scientific importance of high resolution spectroscopy in the Extreme Ultraviolet for the study of stars and the local interstellar medium.     

BVRI CCD-Photometry of Comparison Stars in the Neighborhoods of Galaxies with Active Nuclei. II

Results are presented from CCD BVRI-observations of 145 comparison stars in the neighborhoods of 14 Seyfert galaxies, 3 quasars, and 5 BL Lac objects with right ascensions of 12 to 24 hours. The magnitudes of the observed stars ranged from V=11 to V=17. The typical photometric error for stars brighter V=14 is 0^m.01. The B, V, Rc, and Ic magnitudes of most of these stars were not known previously. 14′ x 14′ finding charts are provided. These results can be used for differential photometry of the nuclei of active galaxies in the B, V, Rc, and Ic bands.__________Translated from Astrofizika, Vol. 48, No. 3, pp. 365–379 (August 2005).     

类星体SDSS J0916+2921的类银河系2175 ?尘埃消光特征

光谱观测显示类星体SDSS J091613.60+292106.1 (简称J0916+2921,系统红移zem=1.1418±0.0018)中有特殊的2175?尘埃消光特征,其强度显著大于银河系平均强度.光谱同时探测到与尘埃成协的丰富气体吸收线,确定吸收线系统红移为zabs=1.1413±0.0002,和类星体红移一致.气态金属离子柱密度相对太阳丰度的比例为[Al/Zn]=-1.68±0.10,[Cr/Zn]=-0.49±0.10,[Fe/Zn]=-0.81±0.18.尘埃耗散作用显著,说明该系统中尘埃十分丰富,与观测的强尘埃消光特征吻合.类银河系的2175?尘埃消光特征在类星体光谱中多见于中间插入吸收线系统,至今未明确认证内禀吸收线系统出现该特征,类星体SDSS J0916+2921是目前仅有的数个候选者之一.该类星体X射线辐射相较一般类星体更强,后续可用作研究2175?尘埃在强高能射线照射条件下的形成与离解平衡,以揭示2175?尘埃的化学成分、物理性质和起源.     

赛弗特星系中的分子环

介绍了近年来Ｓｅｙｆｅｒｔ领域中关于分子环（ｔｏｒｕｓ）研究情况和现状。分子环模型的提出源于２型Ｓｅｙｆｅｒｔ星系核的光学偏振观测的结果与传统的１型Ｓｅｙｆｅｒｔ核的观测特征的相似性。在ｔｏｒｕｓ结构存在的假设下,讨论其对观测的作用,阐述了ｔｏｒｕｓ可能的结构和演化及其在Ｓｅｙｆｅｒｔ统一模型中的重要地位。还讨论了ｔｏｒｕｓ的遮挡、束流效应和由此造成的多波段观测特性,着重介绍了散射效应及其造成的偏