Gang Zhao

East China University of Science and Technology, Shanghai, Shanghai Shi, China

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Publications (257)652.78 Total impact

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    ABSTRACT: We report on the observations of two ultra metal-poor (UMP) stars with [Fe/H]~-4.0 including one new discovery. The two stars are studied in the on-going and quite efficient project to search for extremely metal-poor (EMP) stars with LAMOST and Subaru. Detailed abundances or upper limits of abundances have been derived for 15 elements from Li to Eu based on high-resolution spectra obtained with Subaru/HDS. The abundance patterns of both UMP stars are consistent with the "normal-population" among the low-metallicity stars. Both of the two program stars show carbon-enhancement without any excess of heavy neutron-capture elements, indicating that they belong to the subclass of CEMP-no stars, as is the case of most UMP stars previously studied. The [Sr/Ba] ratios of both CEMP-no UMP stars are above [Sr/Ba]~-0.4, suggesting the origin of the carbon-excess is not compatible with the mass transfer from an AGB companion where the s-process has operated. Lithium abundance is measured in the newly discovered UMP star LAMOST J125346.09+075343.1, making it the second UMP turnoff star with Li detection. The Li abundance of LAMOST J125346.09+075343.1 is slightly lower than the values obtained for less metal-poor stars with similar temperature, and provides a unique data point at [Fe/H]~-4.2 to support the "meltdown" of the Li Spite-plateau at extremely low metallicity. Comparison with the other two UMP and HMP (hyper metal-poor with [Fe/H]<-5.0) turnoff stars suggests that the difference in lighter elements such as CNO and Na might cause notable difference in lithium abundances among CEMP-no stars.
    Publications- Astronomical Society of Japan 06/2015; DOI:10.1093/pasj/psv053 · 2.07 Impact Factor
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    ABSTRACT: We report the discovery of an extremely metal-poor (EMP) giant, LAMOST J110901.22+075441.8, which exhibits large excess of r-process elements with [Eu/Fe] ~ +1.16. The star is one of the newly discovered EMP stars identified from LAMOST low-resolution spectroscopic survey and the high-resolution follow-up observation with the Subaru Telescope. Stellar parameters and elemental abundances have been determined from the Subaru spectrum. Accurate abundances for a total of 23 elements including 11 neutron-capture elements from Sr through Dy have been derived for LAMOST J110901.22+075441.8. The abundance pattern of LAMOST J110901.22+075441.8 in the range of C through Zn is in line with the "normal" population of EMP halo stars, except that it shows a notable underabundance in carbon. The heavy element abundance pattern of LAMOST J110901.22+075441.8 is in agreement with other well studied cool r-II metal-poor giants such as CS 22892-052 and CS 31082-001. The abundances of elements in the range from Ba through Dy well match the scaled Solar r-process pattern. LAMOST J110901.22+075441.8 provides the first detailed measurements of neutron-capture elements among r-II stars at such low metallicity with [Fe/H]<-3.4, and exhibits similar behavior in the abundance ratio of Zr/Eu as well as Sr/Eu and Ba/Eu as other r-II stars.
    Research in Astronomy and Astrophysics 06/2015; 15(8). DOI:10.1088/1674-4527/15/8/011 · 1.64 Impact Factor
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    ABSTRACT: Due to stellar rotation, the observed radial velocity of a star varies during the transit of a planet across its surface, a phenomenon known as the Rossiter-McLaughlin (RM) effect. The amplitude of the RM effect is related to the radius of the planet which, because of differential absorption in the planetary atmosphere, depends on wavelength. Therefore, the wavelength-dependent RM effect can be used to probe the planetary atmosphere. We measure for the first time the RM effect of the Earth transiting the Sun using a lunar eclipse observed with the ESO HARPS spectrograph. We analyze the observed RM effect at different wavelengths to obtain the transmission spectrum of the Earth's atmosphere after the correction of the solar limb-darkening and the convective blueshift. The ozone Chappuis band absorption as well as the Rayleigh scattering features are clearly detectable with this technique. Our observation demonstrates that the RM effect can be an effective technique for exoplanet atmosphere characterization. Its particular asset is that photometric reference stars are not required, circumventing the principal challenge for transmission spectroscopy studies of exoplanet atmospheres using large ground-based telescopes.
    06/2015; 806(2). DOI:10.1088/2041-8205/806/2/L23
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    ABSTRACT: A novel family of dipeptide-based multifunctional quaternary phosphonium salts has been developed as chiral phase-transfer catalysts, which feature ready accessibility and structure modularity, allowing easy fine-tunings of activity. They demonstrated high efficiency in catalyzing the tandem asymmetric Michael addition/intramolecular SN 2 reaction between 6 or 7-substituted conjugate enones and malonates, providing synthetically important five or six-membered carbocycles and heterocycles in good yields and with good to excellent enantioselectivities. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Chemistry - A European Journal 06/2015; 21(28). DOI:10.1002/chem.201501806 · 5.73 Impact Factor
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    ABSTRACT: Hyper-velocity stars are believed to be ejected out from the Galactic center through dynamical interactions between (binary) stars and the central massive black hole(s). In this paper, we report 19 low mass F/G/K type hyper-velocity star candidates from over one mil- lion stars of the first data release of the LAMOST general survey. We determine the unbound probability for each candidate using a Monte-Carlo simulation by assuming a non-Gaussian proper-motion error distribution, Gaussian heliocentric distance and radial velocity error dis- tributions. The simulation results show that all the candidates have unbound possibilities over 50% as expected, and one of them may even exceed escape velocity with over 90% probabili- ty. In addition, we compare the metallicities of our candidates with the metallicity distribution functions of the Galactic bulge, disk, halo and globular cluster, and conclude that the Galactic bulge or disk is likely the birth place for our candidates.
    Research in Astronomy and Astrophysics 06/2015; 15(8). DOI:10.1088/1674-4527/15/8/018 · 1.64 Impact Factor
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    ABSTRACT: Palladium (Pd) and silver (Ag) are the key elements for probing the weak component in the rapid neutron-capture process (r-process) of stellar nucleosynthesis. We performed a detailed analysis of the high-resolution and high signal-to-noise ratio near-UV spectra from the archive of HIRES on the Keck telescope, UVES on the VLT, and HDS on the Subaru Telescope, to determine the Pd and Ag abundances of 95 stars. This sample covers a wide metallicity range with -2.6 $\lesssim$ [Fe/H] $\lesssim$ +0.1, and most of them are dwarfs. The plane-parallel LTE MAFAGS-OS model atmosphere was adopted, and the spectral synthesis method was used to derive the Pd and Ag abundances from Pd I {\lambda} 3404 {\AA} and Ag I {\lambda} 3280/3382 {\AA} lines. We found that both elements are enhanced in metal-poor stars, and their ratios to iron show flat trends at -0.6 < [Fe/H] < +0.1. The abundance ratios of [Ag/H] and [Pd/H] are well correlated over the whole abundance range. This implies that Pd and Ag have similar formation mechanisms during the Galactic evolution.
    Astronomy and Astrophysics 05/2015; 579. DOI:10.1051/0004-6361/201525679 · 4.38 Impact Factor
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    ABSTRACT: A new simple mechanism due to cold electron flow to produce strong magnetic field is proposed. A 600-T strong magnetic field is generated in the free space at the laser intensity of 5.7x10^15 Wcm^-2. Theoretical analysis indicates that the magnetic field strength is proportional to laser intensity. Such a strong magnetic field offers a new experimental test bed to study laser-plasma physics, in particular, fast-ignition laser fusion research and laboratory astrophysics.
  • Yude Bu · Gang Zhao · A-li Luo · Jingchang Pan · Yuqin Chen
    Astronomy and Astrophysics 04/2015; 576:A96. DOI:10.1051/0004-6361/201424194 · 4.38 Impact Factor
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    Bo Han · Feilu Wang · David Salzmann · Gang Zhao
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    ABSTRACT: We present a new code, RCF (“Radiative–Collisional code based on FAC”), which is used to simulate steady-state plasmas under non-local thermodynamic equilibrium condition, especially photoinization-dominated plasmas. RCF takes almost all of the radiative and collisional atomic processes into a rate equation to interpret the plasmas systematically. The Flexible Atomic Code (FAC) supplies all the atomic data needed for RCF, which insures calculating completeness and consistency of atomic data. With four input parameters relating to the radiation source and target plasma, RCF calculates the population of levels and charge states, as well as potential emission spectrum. In a preliminary application, RCF successfully reproduced the results of a photoionization experiment with reliable atomic data. The effects of the most important atomic processes on the charge state distribution are also discussed.
    Publications- Astronomical Society of Japan 03/2015; 67(2). DOI:10.1093/pasj/psu162 · 2.07 Impact Factor
  • XiaoLing Yang · YuQin Chen · Gang Zhao
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    ABSTRACT: We have compiled a list of all planet host star candidates reported in the literature, which are likely to be cluster members, and we checked their memberships by the spatial location, radial velocity, proper motion and photometric criteria. We found that only six stars, BD-13 2130, HD 28305, Kepler-66, Kepler-67, Pr0201 and Pr0211, are planet orbiting stars in open clusters to date. Two stars, HD 70573 and HD 89744, belong to moving groups and one star, TYC 8975-2606-1, may not be a planet host star, while three stars, HD 16175, HD 46375 and HD 108874 are not members of open clusters. We note that all these six planetary systems in the stellar cluster environment are younger than ∼1 Gyr, which might indicate that the planetary system in open cluster can not survive for a long time, and we speculate that close stellar encounters between member stars in open cluster can potentially destroy, or at least strongly affect, the presence of planetary systems.
    Science China: Physics, Mechanics and Astronomy 03/2015; 58(3). DOI:10.1007/s11433-014-5593-z · 1.14 Impact Factor
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    ABSTRACT: Desymmetrization of meso-aziridines with aromatic thiols was realized by using α-amino acids-derived chiral quaternary phosphonium salts catalysts to provide chiral β-amino sulfides with high yields (up to 99%) and in moderate enantioselectivities (up to 70%).
    Tetrahedron 02/2015; 46(27). DOI:10.1016/j.tet.2015.02.001 · 2.64 Impact Factor
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    ABSTRACT: A combination of an amino acid derived chiral phosphine catalyst and methyl acrylate efficiently catalyzed the direct Mannich reaction of cyclic β-ketoesters and N-Boc-aldimines. The dual-reagent catalysis was presumed to function through the formation of a zwitterion, which catalyzed the reaction with excellent stereocontrol via a hydrogen-bonding assisted chiral ion-pair pathway.
    Organic Letters 01/2015; 46(26). DOI:10.1021/ol503712m · 6.36 Impact Factor
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    ABSTRACT: We report on early results from a pilot program searching for metal-poor stars with LAMOST and follow-up high-resolution observation acquired with the MIKE spectrograph attached to the Magellan~II telescope. We performed detailed abundance analysis for eight objects with iron abundances [Fe/H] < -2.0, including five extremely metal-poor (EMP; [Fe/H] < -3.0) stars with two having [Fe/H] < -3.5. Among these objects, three are newly discovered EMP stars, one of which is confirmed for the first time with high-resolution spectral observations. Three program stars are regarded as carbon-enhanced metal-poor (CEMP) stars, including two stars with no enhancement in their neutron-capture elements, which thus possibly belong to the class of CEMP-no stars; one of these objects also exhibits significant enhancement in nitrogen, and is thus a potential carbon and nitrogen-enhanced metal-poor star. The [X/Fe] ratios of the sample stars generally agree with those reported in the literature for other metal-poor stars in the same [Fe/H] range. We also compared the abundance patterns of individual program stars with the average abundance pattern of metal-poor stars, and find only one chemically peculiar object with abundances of at least two elements (other than C and N) showing deviations larger than 0.5dex. The distribution of [Sr/Ba] versus [Ba/H] agrees that an additional nucleosynthesis mechanism is needed aside from a single r-process. Two program stars with extremely low abundances of Sr and Ba support the prospect that both main and weak r-process may have operated during the early phase of Galactic chemical evolution. The distribution of [C/N] shows that there are two groups of carbon-normal giants with different degrees of mixing. However, it is difficult to explain the observed behavior of the [C/N] of the nitrogen-enhanced unevolved stars based on current data.
    The Astrophysical Journal 01/2015; 798(2). DOI:10.1088/0004-637X/798/2/110 · 5.99 Impact Factor
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    ABSTRACT: The atmospheres of exoplanets are commonly studied by observing the transit of the planet passing in front of its parent star. The obscuration of part of the stellar disk during a transit will reveal aspects of its surface structure resulting from general centre-to-limb variations (CLVs). These become apparent when forming the ratio between the stellar light in and out of transit. These phenomena can be seen particularly clearly during the progress of a penumbral lunar eclipse, where the Earth transits the solar disk and masks different regions of the solar disk as the eclipse progresses. When inferring the properties of the planetary atmosphere, it is essential that this effect originating at the star is properly accounted for. Using the data observed from the 2014-April-15 lunar eclipse with the ESPaDOnS spectrograph mounted on the Canada France Hawaii Telescope (CFHT), we have obtained for the first time a time sequence of the penumbral spectra. These penumbral spectra enable us to study the centre-to-limb variations of solar Fraunhofer lines when the Earth is transiting Sun. The Na i and Ca ii absorption features reported from previous lunar eclipse observations are demonstrated to be CLV features, which dominate the corresponding line profiles and mask possible planetary signal. Detecting atmospheric species in exoplanets via transit spectroscopy must account for the CLV effect.
    Astronomy and Astrophysics 01/2015; 574. DOI:10.1051/0004-6361/201425220 · 4.38 Impact Factor
  • Chen Zeng · Jingyun Zhao · Gang Zhao
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    ABSTRACT: Enantioselective divergent total syntheses of (+)-fawcettimine, (+)-fawcettidine, (+)-lycoflexine, (+)-lycoposerramine Q, (-)-Huperzine Q and (+)-N-oxyhuperzine Q have been described from a common precursor. The syntheses feature a vinylogous Rubottom oxidation and several biomimetic transformations.
    Tetrahedron 01/2015; 71(1):64-69. DOI:10.1016/j.tet.2014.11.041 · 2.64 Impact Factor
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    ABSTRACT: A novel method of initiating nuclear fusion reactions in a full plasma environment was suggested, and a proof-of-concept experiment was carried out with the \(\hbox {D}+\hbox {D } \rightarrow \hbox { n}\,+\,^3\)He reaction. In this new approach, two plasma jets generated by high-intensity lasers collide head-on-head. The center-of-mass energy of the nuclei increases accordingly, and therefore, reaction products can be significantly enhanced, especially in the sub-Coulomb barrier ranges. As a result of the fusion reaction, up to \(\sim 7.6\times 10^{5}\) neutrons had been observed. This new type of “plasma collider” could provide an innovative tool to study nuclear reactions under astrophysical conditions.
    01/2015; DOI:10.1007/s11434-015-0821-0
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    ABSTRACT: For the laboratory astrophysics community, those spectroscopic modeling codes extensively used in astronomy, e.g. Chianti, AtomDB, Cloudy and Xstar, cannot be directly applied to analyzing laboratory measurements due to their discrepancies from astrophysical cases. For example, plasma from an electron beam ion trap has an electron energy distribution that follows a Gaussian profile, instead of a Maxwellian one. The laboratory miniature for a compact object produced by a laser-driven implosion shows a departure from equilibrium, that often occurs in celestial objects, so we setup a spectral analysis system for astrophysical and laboratory (SASAL) plasmas to act as a bridge between them, which benefits the laboratory astrophysical community.
    Research in Astronomy and Astrophysics 10/2014; 14(10):1351. DOI:10.1088/1674-4527/14/10/013 · 1.64 Impact Factor
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    ABSTRACT: We present distance determinations for a large and clean sample of red giant branch stars selected from the ninth data release of the Sloan Digital Sky Survey. The distances are calculated based on both observational cluster fiducials and theoretical isochrones. Distributions of distances from the two methods are very similar with peaks at about 10 kpc and tails extending to more than 70 kpc. We find that distances from the two methods agree well for the majority of the sample stars; though, on average, distances based on isochrones are 10% higher than those based on fiducials. We test the accuracy of our distance determinations using 332 stars from 10 Galactic globular and open clusters. The average relative deviation from the literature cluster distances is 4% for the fiducial-based distances and 8% for the isochrone-based distances, both of which are within the uncertainties. We find that the effective temperature and surface gravity derived from low-resolution spectra are not accurate enough to essentially improve the performance of distance determinations. However, for stars with significant extinction, effective temperature may help to better constrain their distances to some extent. We make our sample stars and their distances available from an online catalog. The catalog comprises 17,941 stars with reasonable distance estimations reaching to more than 70 kpc, which is suitable for the investigation of the formation and evolution of the Galaxy, especially the Galactic halo.
    The Astrophysical Journal 09/2014; 794(1):60. DOI:10.1088/0004-637X/794/1/60 · 5.99 Impact Factor
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    ABSTRACT: We report the detection of a substellar companion orbiting an evolved intermediate-mass ($M_\star=2.4\,M_\odot$) star HD 14067 (G9 III) using precise Doppler technique. Radial velocities of this star can be well fitted either by a periodic Keplerian variation with a decreasing linear velocity trend (P=1455 days, $K_1=92.2$ m s$^{-1}$, $e=0.533$, and $\dot{\gamma}=-22.4$ m s$^{-1}$ yr$^{-1}$) or a single Keplerian orbit without linear trend (P=2850 days, $K_1=100.1$ m s$^{-1}$, and $e=0.697$). The minimum mass ($m_2\sin{i}=7.8\,M_{\rm J}$ for the model with a linear trend, or $m_2\sin{i}=9.0\,M_{\rm J}$ for the model without a linear trend) suggests a long-period giant planet around an evolved intermediate-mass star. The eccentricity of the orbit is among the highest known for planets ever detected around evolved stars.
    Publications- Astronomical Society of Japan 09/2014; 66(6). DOI:10.1093/pasj/psu113 · 2.07 Impact Factor
  • Kai Zhang · Gang Zhao · Weiguo Cao
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    ABSTRACT: A series of 4-fluoro-pyrazole derivatives were synthesized in moderate to good yields via a one-pot tandem procedure involving an Rh-2(OAc)(4)-catalyzed C-H insertion and an electrophilic fluorination with N-fluorobenzenesulfonimide (NFSI).
    Tetrahedron 09/2014; 70(35):5659–5665. DOI:10.1016/j.tet.2014.06.065 · 2.64 Impact Factor

Publication Stats

2k Citations
652.78 Total Impact Points


  • 2015
    • East China University of Science and Technology
      • School of Pharmacy
      Shanghai, Shanghai Shi, China
  • 1999–2015
    • Chinese Academy of Sciences
      • • Key Laboratory of Synthetic Chemistry of Natural Substances
      • • Purple Mountain Observatory
      • • Shanghai Astronomical Observatory
      • • National Astronomical Observatories
      Peping, Beijing, China
    • Shanghai Research Institute of Chemical Industry
      Shanghai, Shanghai Shi, China
  • 2014
    • Peking University
      • Department of Astronomy
      Peping, Beijing, China
  • 2007–2013
    • University of Science and Technology of China
      • Department of Chemistry
      Luchow, Anhui Sheng, China
    • Shanghai Institute of Health Sciences
      Shanghai, Shanghai Shi, China
  • 2012
    • Sun Yat-Sen University
      • Department of Chemical Engineering
      Shengcheng, Guangdong, China
  • 2008–2012
    • Shanghai University
      • Department of Chemistry
      Shanghai, Shanghai Shi, China
  • 2011
    • Shandong University
      Chi-nan-shih, Shandong Sheng, China
    • Clemson University
      CEU, South Carolina, United States
    • Tokyo Institute of Technology
      • Earth and Planetary Sciences Department
      Edo, Tōkyō, Japan
  • 2009
    • Xinjiang University
      Hsin-chien, Jiangxi Sheng, China
  • 2006
    • Anhui Normal University
      Wu-hu-shih, Anhui Sheng, China
  • 2001
    • China Academy of Chinese Medical Sciences
      Peping, Beijing, China
  • 1998
    • Academia Sinica
      T’ai-pei, Taipei, Taiwan