Reduced transition probabilities for 4~He radiative capture reactions at astrophysical energies

The reduced transition probabilities from an electric quadrupole B(E2) and reduced transition probabilities from a magnetic dipole B(M1) between the ground state and the first excited state have been calculated for the3He(α,γ)7Be,8Be(α,γ)12C and12C(α,γ)16O radiative capture reactions with the M3Y potential.These reactions are important in stellar evolution.The calculated B(M1) and B(E2) for7Be nuclei are found to be 1.082×10-3e2fm2and 1.921 e2fm4from transitions 3/2-to 1/2-,respectively.The obtained values for reduced transition probabilities B(E2) for the12C and16O nuclei from transitions 0+to 2+are 12.54 e2fm4and 14.18 e2fm4,respectively.The results are in satisfactory agreement with available experimental data.     

The comparison of H_2CO(1_(10)–1_(11)),C~(18)O(1–0) and the continuum towards molecular clouds

We present large scale observations of C18O(1–0) towards four massive star forming regions: MON R2,S156,DR17/L906 and M17/M18. The transitions of H2CO(110–111),C18O(1–0) and the 6 cm continuum are compared in these four regions. Our analysis of the observations and the results of the Non–LTE model shows that the brightness temperature of the formaldehyde absorption line is strongest in a background continuum temperature range of about 3 – 8 K. The excitation of the H2 CO absorption line is affected by strong background continuum emission. From a comparison of H2 CO and C18 O maps,we found that the extent of H2 CO absorption is broader than that of C18 O emission in the four regions. Except for the DR17 region,the maximum in H2 CO absorption is located at the same position as the C18 O peak. A good correlation between intensities and widths of H2 CO absorption and C18 O emission lines indicates that the H2 CO absorption line can trace the dense,warm regions of a molecular cloud. We find that N(H2CO) is well correlated with N(C18O) in the four regions and that the average ratio of column densities is N(H2CO)/N(C18O) ～ 0.03.     

C_2H, HC_3N and HNC observations in OMC-2/3

For the first time, the OMC-2/3 region was mapped in C2H (1-0), HC3N (10-9) and HNC (1-0) lines. In general, the emissions from all the three molecular species reveal an extended filamentary structure. The distribution of C2H cores almost follows that of the 1300μm condensations, which might suggest that C2H is a good tracer to study the core structure of molecular clouds. The core masses traced by HNC are rather ?at, ranging from 18.8 to 49.5 M , while also presenting a large span for those from C2H, rangi...     

时号改正数

UTC(CSAO)一Signal号频呼载时刻(UTC)1997年7月MJDBPL/6000 100 kHz08:00:00 (娜)LC/9970 100 kHz00:00:00 (拌s) BPMe2.5,5,10,15 MHz- 0():00:00 (ms) BPMI2。5,5,10,15 MHz 00:00:00 (ms)一一一一5063050631506325063350634一1 .75一1 .66一1。62一1 .59一1 .51一19.98一19.98一19。97一19。98一19.97一521.8’一521.1一520.3一519.7一519.0,l夕曰O口月性5063550636506375063850639一1 .37一1。24一1。17一1 .08一1 .0选一19.97一19。97一19。97一19.96一20.01一518。4一517。7一517.5一517.2一517。1一一一一一丹b叮‘︹…     

Resolution-dependent subsonic non-thermal line dispersion revealed by ALMA

We report here Atacama Large Millimeter/submillimeter Array(ALMA)N2H+(1-0)images of the Orion Molecular Cloud 2 and 3(OMC-2/3)with high angular resolution(3"or 1200 au)and high spatial dynamic range.Combining a dataset from the ALMA main array,Atacama Compact Array(ACA),Nobeyama 45-m Telescope and Very Large Array(VLA)(providing temperature measurement on matching scales),we find that most of the dense gas in OMC-2/3 is subsonic(σQNT/cs=0.62)with a mean line width(△v)of 0.39 kms-1 full width at half maximum(FWHM).This is markedly different from the majority of previous observations of massive star-forming regions.In contrast,line widths from the Nobeyama Telescope are transonic at 0.69 km s-1(σNT/cs=1.08).We demonstrated that the larger line widths obtained by the single-dish telescope arose from unresolved sub-structures within their respective beams.The dispersions from larger scalesσls(as traced by the Nobeyama Telescope)can be decomposed into three components such thatσls2=σss2+σbm2+σrd2,where small-scaleσss is the line dispersion of each ALMA beam,bulk motionσbm is dispersion between peak velocity of each ALMA beam andσrd is the residual dispersion.Such decomposition,though purely empirical,appears to be robust throughout our data cubes.Apparent supersonic line widths,commonly found in massive molecular clouds,are thus likely due to the effect of poor spatial resolution.The observed non-thermal line dispersion(sometimes referred to as’turbulence’)transits from supersonic to subsonic at~0.05 pc scales in the OMC-2/3 region.Such transition could be commonly found with sufficient spatial(not just angular)resolution,even in regions with massive young clusters,such as the Orion molecular clouds studied here.     

Infall in massive clumps harboring bright infrared sources

Thirty massive clumps associated with bright infrared sources were observed to detect the infall signatures and characterize infall properties in the envelope of the massive clumps by APEX telescope in CO(4-3)and C17O(3-2)lines.Eighteen objects exhibit a"blue profile"in the CO(4-3)line with virial parameters less than 2,suggesting that global collapse is taking place in these massive clumps.The CO(4-3)lines were fitted via the two-layer model in order to obtain infall velocities and mass infall rates.Derived mass infall rates range from 10-3 to 10-1 M☉yr*(-1).A positive relationship between clump mass and infall rate appears to indicate that gravity plays a dominant role in the collapsing process.Higher luminosity clumps have a larger mass infall rate,implying that those clumps with higher mass infall rates possess a higher star formation rate.     

H.地球自转参数和时号改正数

O产八J尹6月1乙.78 76 73 71682加3年10月 日加幻D (沪U丁C) 1 52913 2 52914 3 52915 4 52916 5 52917 X YUTI一Ul℃Ul、一U几RU几一即喊X(JYD)Y(JYD)0.(减城旧1,0.以兀旧1’ o.oolrns 0.oolrDs 0.lms 0.(扣旧1’0,(KK!1尸乃舫3公卯38256252549925363汉抖加3()139298692961529努5一357506一357558一357530一357580一357721一1249一946一533一130 1632532乃21251024卯熟837 7 7 77月J内J ljo沙弓l65 62 59 5654︸﹄﹄︸︸10529185291952艾犯5292152922乃乞络之铂9624960别811料翻3一358(抖0一358600一359333一肠加77一筑刃758 2…     

A statistical study towards high-mass BGPS clumps with the MALT90 survey

In this work,we perform a statistical investigation towards 50 high-mass clumps using data from the Bolocam Galactic Plane Survey(BGPS)and Millimetre Astronomy Legacy Team 90-GHz survey(MALT90).Eleven dense molecular lines(N_2H~+(1–0),HNC(1–0),HCO~+(1–0),HCN(1–0),HN~(13)C(1–0),H~(13)CO~+(1–0),C_2H(1–0),HC_3N(10–9),SiO(2–1),~(13)CS(2–1)and HNCO(4_(4,0)-3_(0,3)))are detected.N_2H~+ and HNC are shown to be good tracers for clumps in various evolutionary stages since they are detected in all the fields.The detection rates of N-bearing molecules decrease as the clumps evolve,but those of O-bearing species increase with evolution.Furthermore,the abundance ratios[N_2H~+]/[HCO~+]and log([HC_3N]/[HCO~+])decline with log([HCO~+])as two linear functions,respectively.This suggests that N~+2H~+ and HC_3N transform to HCOas the clumps evolve.We also find that C_2H is the most abundant molecule with an order of magnitude 10~(-8).In addition,three new infall candidates,G010.214–00.324,G011.121–00.128 and G012.215–00.118(a),are discovered to have large-scale infall motions and infall rates with an order of magnitude 10~(-3)M_⊙yr~(-1).     

H.地球自转参数和时号改正数

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The X-ray Background (Deep Fields, Luminosity Functions and Type-Ⅱ Quasars)

1　IntroductionDeepX raysurveysindicatethatthecosmicX raybackground (XRB)islargelyduetoaccretionontosupermassiveblackholes,integratedovercosmictime .Inthesoft (0 .5-2keV)bandmorethan 90 %oftheXRBfluxhasbeenresolvedusing 1 .4MsecobservationswithROSAT[1 ]andrecently 1 -2MsecChandraobservations [2 ,3 ]and 1 0 0ksecobservationswithXMM Newton [4] .Intheharder (2 -1 0keV)bandasimilarfractionofthebackgroundhasbeenresolvedwiththeaboveChandraandXMM Newtonsurveys,reachingsourcedensitiesofabou…     

CO observations towards a sample of nearby galaxies

We have simultaneously observed12 CO,13CO and C18O(J = 1- 0)rotational transitions in the centers of a sample of 58 nearby spiral galaxies using the 13.7-m millimeter-wave telescope administered by Purple Mountain Observatory.Forty-two galaxies were detected in13 CO emission, but there was a null detection for C18 O emission with a σ upper limit of 2 m K. The central beam ratios, R, of12 CO and13CO range mostly from 5 to 13, with an average value of 8.1±4.2, which is slightly lower than previous estimates for normal galaxies. Clear correlations are found between12 CO and13CO luminosities. An average X factor of 1.44 ± 0.84 ×1020cm-2(K km s-1)-1is slightly lower than that in the Milky Way.     

Evidence of Evolution in the Dense Cores in Massive Star Forming Regions

The excitation of H2O masers usually needs very high density gas, hence it can serve as a marker of dense gas in HII region. We selected a sample of H2O maser sources from Plume et al. (four with, and four without detected CS(J = 7-6) emission), and observed them in 13CO(J=1-0) and C18O (J=1-0). C18O (J=1-0) emission was detected only in three of the sources with detected CS(J=7-6) emission. An analysis combined with some data in the literature suggests that these dense cores may be located at different evolutionary stages. Multi-line observation study may provide us clues on the evolution of massive star forming regions and the massive stars themselves.     

The isotropic energy function and formation rate of short gamma-ray bursts

Gamma-ray bursts (GRBs) are brief,intense,gamma-ray flashes in the universe,lasting from a few milliseconds to a few thousand seconds.For short gamma-ray bursts (s GRBs) with duration less than 2 seconds,the isotropic energy (E_(iso)) function may be more scientifically meaningful and accurately measured than the luminosity (L_p) function.In this work we construct,for the first time,the isotropic energy function of s GRBs and estimate their formation rate.First,we derive the L_p-E_pcorrelation using22 s GRBs with known redshifts and well-measured spectra and estimate the pseduo redshifts of 334 Fermi s GRBs.Then,we adopt the Lynden-Bell c~-method to study isotropic energy functions and formation rate of s GRBs without any assumption.A strong evolution of isotropic energy E_(iso)∝(1+z)~(5.79)is found,which is comparable to that between L_pand z.After removing effect of the cosmic evolution,the isotropic energy function can be reasonably fitted by a broken power law,which isφ(E_(iso,0))∝E~(-0)_(iso),._0~(45)for dim s GRBs andφ(E_(iso,0))∝E~(-1)_(iso),._0~(11)for bright s GRBs,with the break energy 4.92×10~(49)erg.We obtain the local formation rate of s GRBs is about 17.43 events Gpc~(-3)yr~(-1).If assuming a beaming angle is 6?to 26?,the local formation rate including off-axis s GRBs is estimated asρ_(0,all)=155.79-3202.35 events Gpc~(-3)yr~(-1).     

The kinematical and space structures of IC 2391 open cluster and moving group with Gaia-DR2

The kinematical parameters,spatial shape and structure of the open cluster IC 2391 and the associated stellar stream are studied here using Gaia Data Release 2(GDR2) astrometry data.The apex positions are determined for the open cluster IC 2391(data taken from Cantat-Gaudin et al.) and for the kinematical stream's stars mentioned in Montes et al.employing both convergent point and AD-diagram methods.The values of apex coordinates are:(A,D)CP=(6.~h17 ± 0.~h004,-6.°88 ± 0.°381;for cluster) and(6.~h07 ± 0.~h007,-5.°00 ± 0.°447;stream),and(A0,D0) =(6.~h12 ± 0.~h004,-3.°4 ± 0.°3;cluster) and(6.~h21 ±0.~h007,-11.°895 ± 0.°290;stream).The results are in good agreement with the previously calculated values.The positions of the stars in the disk and the spatial dispersion velocities are determined.The paths of cluster and associated stream are traced in the disk by orbit calculation back in time to their places of formation.A possible genetic relationship between the cluster and stream has been detected.The approximation of the spatial and kinematical shape of the stream and the cluster is made.According to this study,even though currently the cluster and stream seem to have a spatial difference in their locations,they appear to have formed in the same region of the Galactic disk.     

Photometric investigation on the W-subtype contact binary V1197 Her

Multi-color light curves of V1197 Her were obtained with the 2.4 meter optical telescope at the Thai National Observatory and the Wilson-Devinney(W-D) program was used to model the observational light curves. The photometric solutions reveal that V1197 Her is a W-subtype shallow contact binary system with a mass ratio of q = 2.61 and a fill-out factor of f = 15.7%. The temperature difference between the primary star and secondary star is only 140 K in spite of the low degree of contact, which means that V1197 Her is not only in geometrical contact configuration but is also already under thermal contact status.The orbital inclination of V1197 Her is as high as i = 82.7?, and the primary star is completely eclipsed at the primary minimum. The totally eclipsing characteristic implies that the determined physical parameters are highly reliable. The masses, radii and luminosities of the primary star(star 1) and secondary star(star2) are estimated to be M1 = 0.30(1) M_⊙, M2 = 0.77(2) M_⊙, R1 = 0.54(1) R_⊙, R2 = 0.83(1) R_⊙,L1 = 0.18(1) L_⊙and L2 = 0.38(1) L_⊙. The evolutionary statuses of the two component stars are drawn in the Hertzsprung-Russell diagram, showing that the less massive but hotter primary star is more evolved than the secondary star. The period of V1197 Her is decreasing continuously at a rate of d P/dt =-2.58 ×10-7 day · year-1, which can be explained by mass transfer from the more massive star to the less massive one at a rate of dM_2/dt=-1.61 × 10~(-7) M_⊙year~(-1). The light curves of V1197 Her are reported to show the O'Connell effect. Thus, a cool spot is added to the more massive star to model the asymmetry in the light curves.     

H.地球自转参数和时号改正数

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红外暗云G79.2+0.38的性质

对MSX红外暗云G79.2+0.38的11'×7'的区域范围进行了12CO(1-0)、13CO(1-0)和C18O(1-0)谱线的同时观测.观测到的两个C18O(1-0)谱线所界定的云核峰值分布分别对应MSX A波段的两块高消光区域.该区域的氢分子柱密度N(H2)-(5-12)×1022 cm-2,平均密度n-(3±1)×104cm-3.两块分子云核的13CO的线尺度分别是1.7和1.2 pc,而C18O的线尺度分别是1.2和0.6 pc,它们包含的质量为2×102-2×103M(?).分子云核的视向平均密度结构可用幂函数(?)(p)-p-0.34±0.02表征. 13CO和C18O的丰度和典型的光学暗云相比低了4至11倍,但是目前还没有证据表明13CO和C18O的相对丰度比X13/18随柱密度有显著变化.     

Constraints on gen4eralized Chaplygin gas model including gamma-ray bursts

Generalized Chaplygin gas (whose equation of state is PGCG = -A/PGCGα) was proposed as a candidate for unification of dark energy and dark matter. We inves-tigate constraints on this model with the latest observed data. We test the model with type-Ia supernovae (SNe Ia), cosmic microwave background (CMB) anisotropy, X-ray gas mass fractions in clusters, and gamma-ray bursts (GRBs). We calibrate the GRB lu-minosity relations without assuming any cosmological models using SNe Ia. We show that GRBs can extend the Hubble diagram to higher redshifts (z> 6). The GRB Hubble diagram is well behaved and delineates the shape of the Hubble diagram well. We mea-sure As≡A/PGCG,0α+1=0.68-0.08+0.04 (where PGCG,0 is the energy density today) and α=-0.22-0.13+0.15at the 1σconfidence level using all the datasets. Our results rule out the standard Chaplygin gas model (α = 1) at the 3a confidence level. The ACDM is allowed at the 2or confidence level. We find that acceleration could have started at a redshift of z ～ 0.70. The concordance of the generalized Chaplygin gas model with the age estimate of an old high redshift quasar is found. In addition, we show that GRBs can break the degeneracy between the generalized Chaplygin gas model and the XCDM model.     

C~(18)O Observations of the Dark Molecular Cloud L134 and Gas Depletion onto Dust

We map the dark molecular cloud core of L134 in the C18O (J = 1 - 0) emission line using the PMO 13.7m telescope, and present a contour map of integrated intensity of C18O (J = 1 - 0) emission. The C18O cloud is inside the distribution of extinction AB, the visual extinction of blue light, as well as inside the 13CO cloud in the L134 region. The depletion factors in this C18O cloud are generally greater than unity, which means there is gas depletion onto dust. Since only a minimum AB = 9.7 mag is available, and our observations measure both undepleted and depleted regions along the line of sight, the depletion factors could very likely be larger in the central core than the calculated value. So we conclude that depletion does occur in the bulk of the C18O cloud through a comparison between the C18O and blue extinction maps in the L134 region. There is no direct evidence as yet for star formation in L134, and so cores on the verge of collapse will not be visible in CO and other gas molecules.