The astrophysical S-Factor of 4He(3He,γ)7Be reaction at very low-energies

The astrophysical S-factor for ⁴He-³He radiative capture is calculated at very low-energies. We construct conserved two- and three-body electromagnetic currents, using minimal substitution in the explicit momentum dependence of the two- and three-cluster interactions. The realistic Argonne v ₁₈ two-nucleon and Urbana IX or Tucson-Melbourne three-cluster interactions are considered for calculation. The zero energy S-factor is found to be S(0)=0.563 (0.581) keV?b, with (without) three-body interactions, in satisfactory agreement with other theoretical results and experiment data.     

Measurement of the 25Mg(p,γ)26Al reaction at stellar energies

Stellar nuclear reactions, generally occurring at energies well below the Coulomb barrier, have extremely low cross sections posing a very difficult task for their determination using the usual prompt γ-ray detection method. We describe here the application of the highly sensitive Accelerator Mass Spectrometry technique (AMS) as an alternative method for the determination of the resonance strengths of the ²⁵Mg(p,γ) reaction, by off-line counting of the produced ²⁶Al nuclei.     

Strong screening effects on resonant nuclear reaction ~(23)Mg(p,γ) ~(24)Al in the surface of magnetars

Based on the theory of relativistic superstrong magnetic fields(SMFs), by using the method of Thomas-Fermi-Dirac approximations, we investigate the problem of strong electron screening(SES) in SMFs and the influence of SES on the nuclear reaction of ~(23)Mg(p,γ)~(24)Al. Our calculations show that the nuclear reaction will be markedly effected by the SES in SMFs in the surface of magnetars. Our calculated screening rates can increase two orders of magnitude due to SES in SMFs.     

Infrared Spectroscopy from San Fernando Observatory: He I 1083 nm, O I 1316 nm, and Fe I 1565 nm

Imaging spectroscopy of the Sun was carried out at the California State University Northridge San Fernando Observatory using an InGaAs near-IR video camera. Using the Sii 1082.71 nm and Hei 1083.03 nm lines the Evershed effect is measured simultaneously in the photosphere and the chromosphere for three sunspots; the speed of the Evershed flow is measured to be between 3 to 8 times greater in the Hei line than in the Sii line, and the direction is radially inward in the chromosphere and outward in the photosphere. Telluric absorption lines prevented a meaningful measurement of Oi 1128.7 nm limb emission, but an upper limit of 20×10^–3 B is measured for chromospheric limb emission at Oi 1316.3 nm. Zeeman splitting in Fei 1564.9 nm was observed in six sunspot umbrae, and a linear relationship between magnetic field and umbral continuum intensity is confirmed.     

Be星的星周盘模型与Be/X射线双星系统(英)

介绍了Be星的基本特性．评述了近年来对Be星星周物质结构研究的成果．重点介绍了最新的关于Be星星周盘产生和变化的动力学模型．另外，对Be／X射线双星系统的研究也做了简要评述，重点论述了致密星与Be星延伸大气的相互作用．     

Cross section and astrophysical S-factor for 12C(p,γ)13N* reaction with Halo Effective Field Theory at low-energies

We considered one of the proton halo nuclei candidates, ¹³N* nucleus, and calculated the cross section and astrophysical S-factor for ¹²C(p, γ)¹³N* reaction using halo effective field theory without pion (hEFT${}^{\neg \pi }$). The halo effective field theory is used to examine the halo nucleus bound state with a large S-wave scattering length. We calculated the radiative proton capture cross section and the astrophysical S-factor from the fields of the core and the valence proton at the Leading-Order (LO). We showed that there is a good agreement among the our results for cross section and astrophysical S-factor of the ¹²C(p, γ)¹³N* reaction and the experimental data. The astrophysical S-factor that has been estimated at the zero energy (E_cm=0) by using a theoretical calculation of the cross section for direct radiative capture and an extrapolation of this calculation obtained $S\left(0\right)=1.883\times {10}^{-3}$ MeV-b.     

中国天文学会学术会议(序号7):理论天体物理学术讨论会(1983年8月,乌鲁木齐市)

理论天体物理学术讨论会于1983年8月22—28日在新疆乌鲁木齐市昆仑宾馆召开。这个会议是由中国天文学会“高能天体物理”和“星系与宇宙学”两个专业委员会联合召开的。会前,于8月15日—21日,还由这两个专业委员会举办了一期宇宙学暑期讲习班。 参加宇宙学暑期讲习班的有来自全国各地的专业工作者三十余人。这次讲习班由方励之作了宇宙     

Isospin violation in the d(n,γ)~3 H process at energies relevant for big bang nucleosynthesis

The cross section for a neutron-deuteron(nd) radiative capture is calculated using the pionless effective field theory including isospin symmetry breaking(ISB) corrections up to higher order.The triton is studied as a three-body bound state and one has to take into account various ISB effects,relativistic corrections and external electromagnetic currents.The isospin violation in nd radiative capture is improved compared to the one at NLO and N2LO.The cross section is determined to beσtot= [0.505 ± 0.003] mb up to N2LO.A satisfactory agreement between theory and experiment for the calculated cross section has been found by insertion of three-body forces and ISB effects.     

第7届巴西天文奥林匹克竞赛第4等级试题(一)(2004年,高中年级组)

巴西天文奥林匹克竞赛于1998年首次举办,每年一届,至今从未间断。2004年举办的是第七届比赛。巴西一至十二年级的在校生(7至18岁)参加比赛,并从中选拔出九、十、十一年级的选手参加国际天文奥赛。2004年天文奥赛的参赛人数达到了120000人,全国所有的27个州都派出了代表参赛。     

A theoretical qualitatively-explained new-variant of Modified-Newtonian-Dynamics (MOND)

It is surprising that we hardly know only 4% of the universe. Rest of the universe is made up of 73% of dark-energy and 23% of dark-matter. Dark-energy is responsible for acceleration of the expanding universe; whereas dark-matter is said to be necessary as extra-mass of bizarre-properties to explain the anomalous rotational-velocity of galaxy. Though the existence of dark-energy has gradually been accepted in scientific community, but the candidates for dark-matter have not been found as yet and are too crazy to be accepted. Thus, it is obvious to look for an alternative theory in place of dark-matter. Milgrom (Astrophys. J. 270:365, 1983a; 270:371, 1983b) has suggested a ‘Modified Newtonian Dynamics (MOND)’ which appears to be highly successful for explaining the anomalous rotational-velocity. But unfortunately MOND lacks theoretical support. The MOND, in-fact, is (empirical) modification of Newtonian-Dynamics through modification in the kinematical acceleration term ‘a’ (which is normally taken as a=\fracv²ra=\frac{v^{2}}{r}) as effective kinematic acceleration a_effective = a m(\fracaa₀)a_{\mathit{effective}} = a \mu(\frac{a}{a_{0}}), wherein the μ-function is 1 for usual-values of accelerations but equals to \fracaa₀ ( << 1)\frac{a}{a_{0}} (\ll1) if the acceleration ‘a’ is extremely-low lower than a critical value a ₀(10⁻¹⁰ m/s²). In the present paper, a novel variant of MOND is proposed with theoretical backing; wherein with the consideration of universe’s acceleration a _d due to dark-energy, a new type of μ-function on theoretical-basis emerges out leading to a_effective = a(1 -K \fraca₀a)a_{\mathit{effective}} = a(1 -K \frac{a_{0}}{a}). The proposed theoretical-MOND model too is able to fairly explain ‘qualitatively’ the more-or-less ‘flat’ velocity-curve of galaxy-rotation, and is also able to predict a dip (minimum) on the curve.     

中国天文学会学术会议(序号4):图书情报工作学术交流会(1983年5月,昆明)

中国天文学会图书情报委员会主持召开的第一次图书情报学术交流会于1983年5月24日至28日在昆明举行。 全国天文界中有十五个单位的图书情报部门的代表和科研人员代表参加了会议。 长期从事天文学科图书情报工作的一些老同志,结合自已的工作经验,就书刊管理和资料交换等     

L_(syn)-E_(syn,p)-δ relation in active galactic nucleus jets and implication for the physical origin of the L_p-E_(p,z)-Γ_0 relation of gamma-ray bursts

High energy photon radiations of gamma-ray bursts(GRBs) and active galactic nuclei(AGNs)are dominated by their jet radiations.We examine whether the synchrotron radiations of jets in BL Lacs,flat spectrum radio quasars(FSRQs),and Narrow Line Seyfert 1 galaxies(NLS1s) follow the relation between the prompt gamma-ray emission and the initial Lorentz factor(Γ_0) of GRBs.It is shown that the AGN sample does not agree with the L_p-E_(p,z)-Γ_0 relation of GRBs.In addition,we obtain a tight relation of ■ for FSRQs and NLS1 galaxies,where L_(syn) is the luminosity at peak photon energy E_(syn,p) of the synchrotron radiations.This relation is different from the L_p-E_(p,z)-Γ_0 relation of GRB s.The dependence of L_(syn) to δ is consistent with the expectation of the Doppler boosting effect for the FSRQs and NLS1 galaxies,but it is not for GRBs.We argue that Γ_0 may be a representative of the kinetic power of the radiating region and the tight L_p-E_(p,z)-Γ_0 relation is shaped by the radiation physics and the jet power together.     

活动星系核的γ辐射(英文)

本文第1部份,描述从SAS-2卫星得到的能量大于100MeV的宇宙Υ射线数据来证认有Υ射线的活动星系核。11个类星体、3个BLLac天体和1个射电星系的Υ射线辐射已得到证认。 本文第2部分描述活动星系核对河外Υ射线背景辐射的影响。SAS-2的Υ辐射数据,已被用来测定类星体和赛弗特星系的Υ辐射绝对光度与光学绝对光度间的函数关系,并由此导出它们对河外Υ射线背景辐射的贡献。我们指出,类星体(B<20)、赛弗特星系(1型和1.5型)对35—100MeV能量范围的弥散Υ射线背景辐射有相当大的贡献(59％)。由此我们得出河外Υ射线背景辐射可能是由类星体和赛弗特星系这类活动星系产生的结论。 本文第3部份我们对3个有Υ辐射的活动星系核综合其Υ波段和其他波段的数据,以探索这些天体辐射的发射机制。这些综合的数据对发射机制给出严格的限制。我们指出,对这3个天体的数据,与同步自康普顿模型(SSC)的预计是一致的。     

The Parker Problem Revisited: Response to the Interpretation of Low (2010)

This paper responds to points made by Low (Solar Phys. 2010. doi:) with regard to the Parker problem as formulated in Craig and Sneyd (Solar Phys. 232, 41, 2005). We first point out that, since Low focuses mainly on interpreting approximate linearized solutions to the Parker problem, his approach cannot address key issues relating to the finite amplitude stability and dynamic accessibility of potential equilibria. Further difficulties are shown to surround Low’s assertion that non-linear equilibria derived by magneto-frictional relaxation of the Parker problem should be discounted. We conclude that both linear and non-linear approaches to the Parker problem appear remarkably consistent: they demonstrate the development of smooth 3D equilibria as opposed to the routine collapse to singular current sheets.     

Latitude Dependence of the Variations of Sunspot Group Numbers (SGN) and Coronal Mass Ejections (CMEs) in Cycle 23

The 12-month running means of the conventional sunspot number Rz, the sunspot group numbers (SGN) and the frequency of occurrence of Coronal Mass Ejections (CMEs) were examined for cycle 23 (1996 – 2006). For the whole disc, the SGN and Rz plots were almost identical. Hence, SGN could be used as a proxy for Rz, for which latitude data are not available. SGN values were used for 5° latitude belts 0° – 5°, 5° – 10°, 10° – 15°, 15° – 20°, 20° – 25°, 25° – 30° and > 30°, separately in each hemisphere north and south. Roughly, from latitudes 25° – 30° N to 20° – 25° N, the peaks seem to have occurred later for lower latitudes, from latitudes 20° – 25° N to 15° – 20° N, the peaks are stagnant or occur slightly earlier, and then from latitudes 15° – 20° N to 0° – 5° N, the peaks seem to have occurred again later for lower latitudes. Thus, some latitudinal migration is suggested, clearly in the northern hemisphere, not very clearly in the southern hemisphere, first to the equator in 1998, stagnant or slightly poleward in 1999, and then to the equator again from 2000 onwards, the latter reminiscent of the Maunder butterfly diagrams. Similar plots for CME occurrence frequency also showed multiple peaks (two or three) in almost all latitude belts, but the peaks were almost simultaneous at all latitudes, indicating no latitudinal migration. For similar latitude belts, SGN and CME plots were dissimilar in almost all latitude belts except 10° – 20° S. The CME plots had in general more peaks than the SGN plots, and the peaks of SGN often did not match with those of CME. In the CME data, it was noticed that whereas the values declined from 2002 to 2003, there was no further decline during 2003 – 2006 as one would have expected to occur during the declining phase of sunspots, where 2007 is almost a year of sunspot minimum. An inquiry at GSFC-NASA revealed that the person who creates the preliminary list was changed in 2004 and the new person picks out more weak CMEs. Thus a subjectivity (overestimates after 2002) seems to be involved and hence, values obtained before and during 2002 are not directly comparable to values recorded after 2002, except for CMEs with widths exceeding 60°.     

国际电联(ITU-R SG 7)会议消息

1.国际电讯联盟无线电通信局(ITU-R)科学业务组(SG7)于1999年6月7日～11日在瑞士日内瓦电联总部召开99年度 SG7研究组会议。有11个国家及瑞士电讯总局、国际业余无线电联盟、欧洲空间局、ITU-R 的33位代表出席。中国科学院陕西天文台派出代表出席了这次会议。2.SG7根据任务、研究进展的需要建立若干工作组、任务组、或文献联合起草组     

A Low-Frequency (30 – 110 MHz) Antenna System for Observations of Polarized Radio Emission from the Solar Corona

An interferometer antenna system to observe polarized radio emission from the solar corona at different frequencies in the range 30?–?110 MHz has been commissioned recently by the Indian Institute of Astrophysics at the Gauribidanur Radio Observatory (latitude 13°36^′12^′′N and longitude 77°27^′07^′′E), about 100 km north of Bangalore (http://www.iiap.res.in/centres_radio.htm). This paper describes the antenna system, associated analog/digital receiver setup, calibration scheme, and preliminary results.     

中国天文学会学术讨论班(序号3):《双星问题》(1983年9月,北京)

1983年9月12日至18日在北京天文台连营寨观测站(河北省兴隆县境内)举行了“双星动力学”学术讨论班。参加这次讨论班的有紫金山天文台、上海天文台、云南天文台、南京大学天文系、北京师范大学天文系、北京天文台等六个单位的36名科技人员。 这次讨论班上宣读的文章或工作报告共16篇,     

Contribution of 19F resonances on 18O(p,α)15N reaction rate

The ¹⁸O(p,α)¹⁵N reaction influences the isotopes production such as ¹⁹F, ¹⁸O, and ¹⁵N which can be used to test the models of stellar evolution. ¹⁹F is synthesized in both asymptotic giant branch (AGB) and metal-rich Wolf-Rayet (WR) stars. Using R-matrix theory we allow new values of resonances parameters in ¹⁹F. We show that the most important contribution to the differential and total cross section at low energies, comes from the levels in ¹⁹F situated at resonances energies E _R =151, 680 and 840 keV with spin and parity 1/2⁺. The total width of the 680 keV resonance is badly known. So, we have focused on this broad resonance corresponding to the 8.65 MeV level in ¹⁹F. We delimit the temperature range in which each resonance contribution to the total reaction rate occurs by analyzing the ratio (N _A 〈σν〉 _i /N _A 〈σν〉). This allowed us to show that the 680 and 840 keV broad resonances strongly dominate the reaction rate over the stellar temperature range T ₉=0.02–0.06 and T ₉=0.5–5. Finally, these results were compared to NACRE and Iliadis astrophysical compilations.