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51. A search for prompt gamma-ray counterparts to fast radio bursts in the Insight-HXMT data

Author

Guidorzi, C., Marongiu, M., Martone, R., Nicastro, L., Xiong, S. L., Liao, J. Y., Li, G., Zhang, S. N., Amati, L., Frontera, F., Orlandini, M., Rosati, P., Virgilli, E., Zhang, S., Bu, Q. C., Cai, C., Cao, X. L., Chang, Z., Chen, G., Chen, L., Chen, T. X., Chen, Y. B., Chen, Y. P., Cui, W., Cui, W. W., Deng, J. K., Dong, Y. W., Du, Y. Y., Fu, M. X., Gao, G. H., Gao, H., Gao, M., Ge, M. Y., Gu, Y. D., Guan, J., Guo, C. C., Han, D. W., Huang, Y., Huo, J., Jia, S. M., Jiang, L. H., Jiang, W. C., Jin, J., Jin, Y. J., Kong, L. D., Li, B., Li, C. K., Li, M. S., Li, T. P., Li, W., Li, X., Li, X. B., Li, X. F., Li, Y. G., Li, Z. W., Liang, X. H., Liu, B. S., Liu, C. Z., Liu, G. Q., Liu, H. W., Liu, X. J., Liu, Y. N., Lu, B., Lu, F. J., Lu, X. F., Luo, Q., Luo, T., Ma, R. C., Ma, X., Meng, B., Nang, Y., Nie, J. Y., Oui, G., Qu, J. L, Sai, N., Shang, R. C., Song, L. M., Song, X. Y., Sun, L., Tani, Y., Tao, L., Tuo, Y. L., Wang, C., Wang, G. F., Wang, J., Wang, W. S., Wang, Y. S., Wen, X. Y., Wu, B. Y., Wu, B. B., Wu, M., Xiao, G. C., Xiao, S., Xu, Y. P., Yang, J. W., Yang, S., Yang, Y. J., Yi, Q. B., Yin, Q. Q., You, Y., Zhang, A. M. Zhang C. M., Zhang, F., Zhang, H. M., Zhang, J., Zhang, T., Zhang, W. C., Zhang, W., Zhang, W. Z., Zhang, Y., Zhang, Y. F., Zhang, Y. J., Zhang, Z., Zhang, Z. L., Zhang, H. S., Zhang, X. F., Zheng, S. J., Zhou, D. K., Zhou, J. F., Zhu, Y. X., Zhu, Y., and Zhuang, R. L.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

No robust detection of prompt electromagnetic counterparts to fast radio bursts (FRBs) has yet been obtained, in spite of several multi-wavelength searches carried out so far. Specifically, X/gamma-ray counterparts are predicted by some models. We planned on searching for prompt gamma-ray counterparts in the Insight-Hard X-ray Modulation Telescope (Insight-HXMT) data, taking advantage of the unique combination of large effective area in the keV-MeV energy range and of sub-ms time resolution. We selected 39 FRBs that were promptly visible from the High-Energy (HE) instrument aboard Insight-HXMT. After calculating the expected arrival times at the location of the spacecraft, we searched for a significant excess in both individual and cumulative time profiles over a wide range of time resolutions, from several seconds down to sub-ms scales. Using the dispersion measures in excess of the Galactic terms, we estimated the upper limits on the redshifts. No convincing signal was found and for each FRB we constrained the gamma-ray isotropic-equivalent luminosity and the released energy as a function of emission timescale. For the nearest FRB source, the periodic repeater FRB180916.J0158+65, we find $L_{\gamma,iso}<5.5\times 10^{47}$ erg/s over 1 s, whereas $L_{\gamma,iso}<10^{49}-10^{51}$ erg/s for the bulk of FRBs. The same values scale up by a factor of ~100 for a ms-long emission. Even on a timescale comparable with that of the radio pulse itself no keV-MeV emission is observed. A systematic association with either long or short GRBs is ruled out with high confidence, except for subluminous events, as is the case for core-collapse of massive stars (long) or binary neutron star mergers (short) viewed off axis. Only giant flares from extra-galactic magnetars at least ten times more energetic than Galactic siblings are ruled out for the nearest FRB., Comment: 15 pages, 3 figures, 6 tables, accepted by A&A

Published
2020
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52. Switches between accretion structures during flares in 4U 1901+03

Author

Ji, L., Ducci, L., Santangelo, A., Zhang, S., Suleimanov, V., Tsygankov, S., Doroshenko, V., Nabizadeh, A., Zhang, S. N., Ge, M. Y., Tao, L., Bu, Q. C., Qu, J. L., Lu, F. J., Chen, L., Song, L. M., Li, T. P., Xu, Y. P., Cao, X. L., Chen, Y., Liu, C. Z., Cai, C., Chang, Z., Chen, G., Chen, T. X., Chen, Y. B., Chen, Y. P., Cui, W., Cui, W. W., Deng, J. K., Dong, Y. W., Du, Y. Y., Fu, M. X., Gao, G. H., Gao, H., Gao, M., Gu, Y. D., Guan, J., Guo, C. C., Han, D. W., Huang, Y., Huo, J., Jia, S. M., Jiang, L. H., Jiang, W. C., Jin, J., Kong, L. D., Li, B., Li, C. K., Li, G., Li, M. S., Li, W., Li, X., Li, X. B., Li, X. F., Li, Y. G., Li, Z. W., Liang, X. H., Liao, J. Y., Liu, G. Q., Liu, H. X., Liu, H. W., Liu, X. J., Liu, Y. N., Lu, B., Lu, X. F., Luo, Q., Luo, T., Ma, X., Meng, B., Nang, Y., Nie, J. Y., Ou, G., Ren, X. Q., Sai, N., Song, X. Y., Sun, L., Tan, Y., Tuo, Y. L., Wang, C., Wang, G. F., Wang, J., Wang, P. J., Wang, W. S., Wang, Y. S., Wen, X. Y., Wu, B. Y., Wu, B. B., Wu, M., Xiao, G. C., Xiao, S., Xiong, S. L., Yang, J. W., Yang, S., Yang, Yan-Ji, Yang, Yi-Jung, Yi, Q. B., Yin, Q. Q., You, Y., Zhang, A. M., Zhang, C. M., Zhang, F., Zhang, H. M., Zhang, J., Zhang, P., Zhang, T., Zhang, W., Zhang, W. C., Zhang, W. Z., Zhang, Yi, Zhang, Y. F., Zhang, Y. J., Zhang, Y. H., Zhang, Yue, Zhang, Z., Zhang, Z. L., Zhao, H. S., Zhao, X. F., Zheng, S. J., Zhou, D. K., Zhou, J. F., Zhu, Y. X., and Zhu, Y.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We report on our analysis of the 2019 outburst of the X-ray accreting pulsar 4U 1901+03 observed with Insight-HXMT and NICER. Both spectra and pulse profiles evolve significantly in the decaying phase of the outburst. Dozens of flares are observed throughout the outburst. They are more frequent and brighter at the outburst peak. We find that the flares, which have a duration from tens to hundreds of seconds, are generally brighter than the persistent emission by a factor of $\sim$ 1.5. The pulse profile shape during the flares can be significantly different than that of the persistent emission. In particular, a phase shift is clearly observed in many cases. We interpret these findings as direct evidence of changes of the pulsed beam pattern, due to transitions between the sub- and super-critical accretion regimes on a short time scale. We also observe that at comparable luminosities the flares' pulse profiles are rather similar to those of the persistent emission. This indicates that the accretion on the polar cap of the neutron star is mainly determined by the luminosity, i.e., the mass accretion rate., Comment: 11 pages, 8 figures, accepted for publication in MNRAS

Published
2020
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53. Joint Analysis of Energy and RMS Spectra from MAXI J1535-571 with Insight-HXMT

Author

Kong, L. D., Zhang, S., Chen, Y. P., Ji, L., Zhang, S. N., Yang, Y. R., Tao, L., Ma, X., Qu, J. L., Lu, F. J., Bu, Q. C., Chen, L., Song, L. M., Li, T. P., Xu, Y. P., Cao, X. L., Chen, Y., Liu, C. Z., Cai, C., Chang, Z., Chen, G., Chen, T. X., Chen, Y. B., Cui, W., Cui, W. W., Deng, J. K., Dong, Y. W., Du, Y. Y., Fu, M. X., Gao, G. H., Gao, H., Gao, M., Ge, M. Y., Gu, Y. D., Guan, J., Guo, C. C., Han, D. W., Huang, Y., Huo, J., Jia, S. M., Jiang, L. H., Jiang, W. C., Jin, J., Li, B., Li, C. K., Li, G., Li, M. S., Li, W., Li, X., Li, X. B., Li, X. F., Li, Y. G., Li, Z. W., Liang, X. H., Liao, J. Y., Liu, G. Q., Liu, H. X., Liu, H. W., Liu, S. Z., Liu, X. J., Liu, Y. N., Lu, B., Lu, X. F., Luo, Q., Luo, T., Meng, B., Nang, Y., Nie, J. Y., Ou, G., Ren, X. Q., Sai, N., Song, X. Y., Sun, L., Tan, Y., Tuo, Y. L., Wang, C., Wang, G. F., Wang, J., Wang, P. J., Wang, W. S., Wang, Y. S., Wen, X. Y., Wu, B. Y., Wu, B. B., Wu, M., Xiao, G. C., Xiao, S., Xiong, S. L., Xu, H., Yang, J. W., Yang, S., Yang, Y. J., Yi, Q. B., You, Y., Zhang, A. M., Zhang, C. M., Zhang, F., Zhang, H. M., Zhang, J., Zhang, P., Zhang, T., Zhang, W., Zhang, W. C., Zhang, W. Z., Zhang, Y., Zhang, Y. F., Zhang, Y. J., Zhang, Y. H., Zhang, Z., Zhang, Z. L., Zhao, H. S., Zhao, X. F., Zheng, S. J., Zheng, Y. G., Zhou, D. K., Zhou, J. F., Zhu, Y. X., and Zhu, Y.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

A new black hole X-ray binary (BHXRB) MAXI J1535-571 was discovered by MAXI during its outburst in 2017. Using observations taken by the first Chinese X-ray satellite, the Hard X-ray Modulation Telescope (dubbed as Insight-HXMT), we perform a joint spectral analysis (2-150 keV) in both energy and time domains. The energy spectra provide the essential input for probing the intrinsic Quasi-Periodic Oscillation (QPO) fractional rms spectra (FRS). Our results show that during the intermediate state, the energy spectra are in general consistent with those reported by Swift/XRT and NuSTAR. However, the QPO FRS become harder and the FRS residuals may suggest the presence of either an additional power-law component in the energy spectrum or a turn-over in the intrinsic QPO FRS at high energies.

Published
2020

54. Diagnostic of the spectral properties of Aquila X-1 by Insight-HXMT snapshots during the early propeller phase

Author

Güngör, C., Ge, M. Y., Zhang, S., Santangelo, A., Zhang, S. N., Lu, F. J., Zhang, Y., Chen, Y. P., Tao, L., Yang, Y. J., Bu, Q. C., Cai, C., Cao, X. L., Chang, Z., Chen, G., Chen, L., Chen, T. X., Chen, Y., Chen, Y. B., Cui, W., Cui, W. W., Deng, J. K., Dong, Y. W., Du, Y. Y., Fu, M. X., Gao, G. H., Gao, H., Gao, M., Gu, Y. D., Guan, J., Guo, C. C., Han, D. W., Huang, Y., Huo, J., Ji, L., Jia, S. M., Jiang, L. H., Jiang, W. C., Jin, J., Kong, L. D., Li, B., Li, C. K., Li, G., Li, M. S., Li, T. P., Li, W., Li, X., Li, X. B., Li, X. F., Li, Y. G., Li, Z. W., Liang, X. H., Liao, J. Y., Liu, C. Z., Liu, G. Q., Liu, H. W., Liu, X. J., Liu, Y. N., Lu, B., Lu, X. F., Luo, T., Luo, Q., Ma, X., Meng, B., Nang, Y., Nie, J. Y., Ou, G., Sai, N., Song, L. M., Song, X. Y., Sun, L., Tan, Y., Tuo, Y. L., Wang, C., Wang, G. F., Wang, J., Wang, W. S., Wang, Y. S., Wen, X. Y., Wu, B. B., Wu, B. Y., Wu, M., Xiao, G. C., Xiao, S., Xiong, S. L., Xu, Y. P., Yang, J. W., Yang, S., Yi, Q. B., Yin, Q. Q., You, Y., Zhang, A. M., Zhang, C. M., Zhang, F., Zhang, H. M., Zhang, J., Zhang, T., Zhang, W., Zhang, W. C., Zhang, W. Z., Zhang, Y. F., Zhang, Y. J., Zhang, Z., Zhang, Z. L., Zhao, H. S., Zhao, X. F., Zheng, S. J., Zhou, D. K., Zhou, J. F., Zhu, Y., and Zhu, Y. X.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We study the 2018 outburst of Aql X-1 via the monitor of all sky X-ray image (MAXI) data. We show that the outburst starting in February 2018 is a member of short-low class in the frame of outburst duration and the peak count rate although the outburst morphology is slightly different from the other fast-rise-exponential-decay (FRED) type outbursts with a milder rising stage. We study the partial accretion in the weak propeller stage of Aql X-1 via the MAXI data of the 2018 outburst. We report on the spectral analysis of 3 observations of Aquila X-1 obtained by Insight - hard X-ray modulation telescope (Insight-HXMT) during the late decay stage of the 2018 outburst. We discuss that the data taken by Insight-HXMT is just after the transition to the weak propeller stage. Our analysis shows the necessity of a comptonization component to take into account the existence of an electron cloud resulting photons partly up-scattered., Comment: 8 pages, 4 figures, accepted for publication in JHEAp

Published
2019

55. $Insight$-HXMT study of the timing properties of Sco X-1

Author

Jia, S. M., Bu, Q. C., Qu, J. L., Lu, F. J., Zhang, S. N., Huang, Y., Ma, X., Tao, L., Xiao, G. C., Zhang, W., Chen, L., Song, L. M., Zhang, S., Li, T. B., Xu, Y. P., Cao, X. L., Chen, Y., Liu, C. Z., Cai, C., Chang, Z., Chen, G., Chen, T. X., Chen, Y. B., Chen, Y. P., Cui, W., Cui, W. W., Deng, J. K., Dong, Y. W., Du, Y. Y., Fu, M. X., Gao, G. H., Gao, H., Gao, M., Ge, M. Y., Gu, Y. D., Guan, J., Guo, C. C., Han, D. W., Huo, J., Jiang, L. H., Jiang, W. C., Jin, J., Kong, L. D., Li, B., Li, C. K., Li, G., Li, M. S., Li, W., Li, X., Li, X. B., Li, X. F., Li, Y. G., Li, Z. W., Liang, X. H., Liao, J. Y., Liu, G. Q., Liu, H. W., Liu, X. J., Liu, Y. N., Lu, B., Lu, X. F., Luo, Q., Luo, T., Meng, B., Nang, Y., Nie, J. Y., Ou, G., Sai, N., Song, X. Y., Sun, L., Tan, Y., Tuo, Y. L., Wang, C., Wang, G. F., Wang, J., Wang, W. S., Wang, Y. S., Wen, X. Y., Wu, B. Y., Wu, B. B., Wu, M., Xiao, S., Xiong, S. L., Yang, J. W., Yang, S., Yang, Y. J., Yin, Q. Q., Yi, Q. B., You, Y., Zhang, A. M., Zhang, C. M., Zhang, F., Zhang, H. M., Zhang, J., Zhang, T., Zhang, W. C., Zhang, W. Z., Zhang, Y., Zhang, Y. F., Zhang, Y. J., Zhang, Z., Zhang, Z. L., Zhao, H. S., Zhao, X. F., Zheng, S. J., Zhou, D. K., Zhou, J. F., Zhu, Y. X., and Zhu, Y.

Subjects
Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Phenomenology
Abstract

We present a detailed timing study of the brightest persistent X-ray source Sco X-1 using the data collected by the Hard X-ray Modulation Telescope ($Insight$-HXMT) from July 2017 to August 2018. A complete $Z$-track hardness-intensity diagram (HID) is obtained. The normal branch oscillations (NBOs) at $\sim$ 6 Hz in the lower part of the normal branch (NB) and the flare branch oscillations (FBOs) at $\sim$ 16 Hz in the beginning part of the flaring branch (FB) are found in observations with the Low Energy X-ray Telescope (LE) and the Medium Energy X-ray Telescope (ME) of $Insight$-HXMT, while the horizontal branch oscillations (HBOs) at $\sim$ 40 Hz and the kilohertz quasi-periodic oscillations (kHz QPOs) at $\sim$ 800 Hz are found simultaneously up to 60 keV for the first time on the horizontal branch (HB) by the High Energy X-ray Telescope (HE) and ME. We find that for all types of the observed QPOs, the centroid frequencies are independent of energy, while the root mean square (rms) increases with energy; the centroid frequencies of both the HBOs and kHz QPOs increase along the $Z$-track from the top to the bottom of the HB; and the NBOs show soft phase lags increasing with energy. A continuous QPO transition from the FB to NB in $\sim$ 200 s are also detected. Our results indicate that the non-thermal emission is the origin of all types of QPOs, the innermost region of the accretion disk is non-thermal in nature, and the corona is nonhomogeneous geometrically.

Published
2019

56. Insight-HXMT observation on 4U~1608--52: evolving spectral properties of a bright type-I X-ray burst

Author

Chen, Y. P., Zhang, S., Zhang, S. N., Ji, L., Kong, L. D., Santangelo, A., Qu, J. L., Lu, F. J., Li, T. P., Song, L. M., Xu, Y. P., Cao, X. L., Chen, Y., Liu, C. Z., Bu, Q. C., Cai, C., Chang, Z., Chen, G., Chen, L., Chen, T. X., Chen, Y. B., Cui, W., Cui, W. W., Deng, J. K., Dong, Y. W., Du, Y. Y., Fu, M. X., Gao, G. H., Gao, H., Gao, M., Ge, M. Y., Gu, Y. D., Guan, J., Guo, C. C., Han, D. W., Huang, Y., Huo, J., Jia, S. M., Jiang, L. H., Jiang, W. C., Jin, J., Li, B., Li, C. K., Li, G., Li, M. S., Li, W., Li, X., Li, X. B., Li, X. F., Li, Y. G., Li, Z. W., Liang, X. H., Liu, J. Y. Liao G. Q., Liu, H. W., Liu, X. J., Liu, Y. N., Lu, B., Lu, X. F., Luo, Q., Luo, T., Ma, X., Meng, B., Nang, Y., Nie, J. Y., Ou, G., Sai, N., Sun, L., Tan, Y., Tao, L., Tuo, Y. L., Wang, C., Wang, G. F., Wang, J., Wang, W. S., Wang, Y. S., Wen, X. Y., Wu, B. Y., Wu, B. B., Wu, M., Xiao, G. C., Xiao, S., Xiong, S. L., Yang, J. W., Yang, S., Yang, Yang-Ji, Yang, Yi-Jung, Yi, Q. B., Yin, Q. Q., You, Y., Zhang, A. M., Zhang, C. L., Zhang, C. M., Zhang, F., Zhang, H. M., Zhang, J., Zhang, T., Zhang, W. C., Zhang, W., Zhang, W. Z., Zhang, Yi., Zhang, Y. F., Zhang, Y. J., Zhang, Yue., Zhang, Z., Zhang, Z. L., Zhao, H. S., Zhao, X. F., Zheng, S. J., Zhou, D. K., Zhou, J. F., Zhu, Y., and Zhu, Y. X.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

The evidences for the influence of thermonuclear (type-I) X-ray bursts upon the surrounding environments in neutron star low-mass X-ray binaries (LMXB) were detected previously via spectral and timing analyses. Benefitting from a broad energy coverage of Insight-HXMT, we analyze one photospheric radius expansion (PRE) burst, and find an emission excess at soft X-rays. Our spectral analysis shows that, such an excess is not likely relevant to the disk reflection induced by the burst emission and can be attributed to an enhanced pre-burst/persistent emission. We find that the burst and enhanced persistent emissions sum up to exceed Eddington luminosity by $\sim$ 40 percentages. We speculate that the enhanced emission is from a region beyond the PRE radius, or through the Comptonization of the corona., Comment: accepted by JHEA(Journal of High Energy Astrophysics)

Published
2019

57. Insight-HXMT observations of 4U~1636-536: Corona cooling revealed with single short type-I X-ray burst

Author

Chen, Y. P., Zhang, S., Zhang, S. N., Ji, L., Kong, L. D., Cao, X. L., Chang, Z., Chen, G., Chen, L., Chen, T. X., Chen, Y., Chen, Y. B., Cui, W., Cui, W. W., Deng, J. K., Dong, Y. W., Du, Y. Y., Fu, M. X., Gao, G. H., Gao, H., Gao, M., Ge, M. Y., Gu, Y. D., Guan, J., Guo, C. C., Han, D. W., Hu, W., Huang, Y., Huo, J., Jia, S. M., Jiang, L. H., Jiang, W. C., Jin, J., Jin, Y. J., Li, B., Li, C. K., Li, G., Li, M. S., Li, T. P., Li, W., Li, X., Li, X. B., Li, X. F., Li, Y. G., Li, Z. J., Li, Z. W., Liang, X. H., Liao, J. Y., Liu, C. Z., Liu, G. Q., Liu, H. W., Liu, S. Z., Liu, X. J., Liu, Y., Liu, Y. N., Lu, B., Lu, F. J., Lu, X. F., Luo, T., Ma, X., Meng, B., Nang, Y., Nie, J. Y., Ou, G., Qu, J. L., Sai, N., Song, L. M., Sun, L., Tan, Y., Tao, L., Tao, W. H., Tuo, Y. L., Wang, G. F., Wang, H. Y., Wang, J., Wang, W. S., Wang, Y. S., Wen, X. Y., Wu, B. B., Wu, M., Xiao, G. C., Xiong, S. L., Xu, H., Xu, Y. P., Yan, L. L., Yang, J. W., Yang, S., Yang, Y. J., Zhang, A. M., Zhang, C. L., Zhang, C. M., Zhang, F., hang, H. M., Zhang, J., Zhang, Q., Zhang, T., Zhang, W., Zhang, W. C., Zhang, W. Z., Zhang, Y., Zhang, Y. F., Zhang, Y. J., Zhang, Z., Zhang, Z. L., Zhao, H. S., Zhao, J. L., Zhao, X. F., Zheng, S. J., Zhu, Y., Zhu, Y. X., and Zou, C. L.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

Corona cooling was detected previously from stacking a series of short type-I bursts occurred during the low/had state of atoll outburst. Type-I bursts are hence regarded as sharp probe to our better understanding on the basic property of the corona. The launch of the first Chinese X-ray satellite Insight-HXMT has large detection area at hard X-rays which provide almost unique chance to move further in this research field. We report the first detection of the corona cooling by Insight-HXMT from single short type-I burst showing up during {\bf flare} of 4U 1636-536. This type-I X-ray burst has a duration of $\sim$13 seconds and hard X-ray shortage is detected with significance 6.2~$\sigma$ in 40-70 keV. A cross-correlation analysis between the lightcurves of soft and hard X-ray band, shows that the corona shortage lag the burst emission by 1.6 $\pm$1.2~s. These results are consistent with those derived previously from stacking a large amount of bursts detected by RXTE/PCA within a series of {\bf flares} of 4U 1636-536. Moreover, the broad bandwidth of Insight-HXMT allows as well for the first time to infer the burst influence upon the continuum spectrum via performing the spectral fitting of the burst, which ends up with the finding that hard X-ray shortage appears at around 40 keV in the continuum spectrum. These results suggest that the evolution of the corona along with the outburst{\bf /flare} of NS XRB may be traced via looking into a series of embedded type-I bursts by using Insight-HXMT., Comment: published in 2018, ApJL,864, L30

Published
2019
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58. Timing analysis of 2S 1417-624 observed with NICER and Insight-HXMT

Author

Ji, L., Doroshenko, V., Santangelo, A., Gungor, C., Zhang, S., Ducci, L., Zhang, S. -N., Ge, M. -Y., Qu, L. J., Chen, Y. P., Bu, Q. C., Cao, X. L., Chang, Z., Chen, G., Chen, L., Chen, T. X., Chen, Y., Chen, Y. B., Cui, W., Cui, W. W., Deng, J. K., Dong, Y. W., Du, Y. Y., Fu, M. X., Gao, G. H., Gao, H., Gao, M., Gu, Y. D., Guan, J., Guo, C. C., Han, D. W., Hu, W., Huang, Y., Huo, J., Jia, S. M., Jiang, L. H., Jiang, W. C., Jin, J., Jin, Y. J., Kong, L. D., Li, B., Li, C. K., Li, G., Li, M. S., Li, T. P., Li, W., Li, X., Li, X. B., Li, X. F., Li, Y. G., Li, Z. J., Li, Z. W., Liang, X. H., Liao, J. Y., Liu, C. Z., Liu, G. Q., Liu, H. W., Liu, S. Z., Liu, X. J., Liu, Y., Liu, Y. N., Lu, B., Lu, F. J., Lu, X. F., Luo, T., Ma, X., Meng, B., Nang, Y., Nie, J. Y., Ou, G., Sai, N., Song, L. M., Song, X. Y., Sun, L., Tan, Y., Tao, L., Tuo, Y. L., Wang, G. F., Wang, J., Wang, W. S., Wang, Y. S., Wen, X. Y., Wu, B. B., Wu, M., Xiao, G. C., Xiong, S. L., Xu, H., Xu, Y. P., Yang, Y. R., Yang, J. W., Yang, S., Yang, Y. J., Zhang, A. M., Zhang, C. L., Zhang, C. M., Zhang, F., Zhang, H. M., Zhang, J., Zhang, Q., Zhang, T., Zhang, W., Zhang, W. C., Zhang, W. Z., Zhang, Y., Zhang, Y. F., Zhang, Y. J., Zhang, Z., Zhang, Z. L., Zhao, H. S., Zhao, J. L., Zhao, X. F., Zheng, S. J., Zhu, Y., Zhu, Y. X., and Zou, C. L.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We present a study of timing properties of the accreting pulsar 2S 1417-624 observed during its 2018 outburst, based on Swift/BAT, Fermi/GBM, Insight-HXMT and NICER observations. We report a dramatic change of the pulse profiles with luminosity. The morphology of the profile in the range 0.2-10.0keV switches from double to triple peaks at $\sim2.5$ $\rm \times 10^{37}{\it D}_{10}^2\ erg\ s^{-1}$ and from triple to quadruple peaks at $\sim7$ $\rm \times 10^{37}{\it D}_{10}^2\ erg\ s^{-1}$. The profile at high energies (25-100keV) shows significant evolutions as well. We explain this phenomenon according to existing theoretical models. We argue that the first change is related to the transition from the sub to the super-critical accretion regime, while the second to the transition of the accretion disc from the gas-dominated to the radiation pressure-dominated state. Considering the spin-up as well due to the accretion torque, this interpretation allows to estimate the magnetic field self-consistently at $\sim7\times 10^{12}$G., Comment: 7 pages, 4 figures, 1 tables, accepted for publication in MNRAS

Published
2019
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59. Constant cyclotron line energy in Hercules X-1 -- Joint Insight-HXMT and NuSTAR observations

Author

Xiao, G. C., Ji, L., Staubert, R., Ge, M. Y., Zhang, S., Zhang, S. N., Santangelo, A., Ducci, L., Liao, J. Y., Guo, C. C., Li, X. B., Zhang, W., Qu, J. L., Lu, F. J., Li, T. P., Song, L. M., Xu, Y. P., Bu, Q. C., Cai, C., Cao, X. L., Chang, Z., Chen, G., Chen, L., Chen, T. X., Chen, Y. B., Chen, Y., Chen, Y. P., Cui, W., Cui, W. W., Deng, J. K., Dong, Y. W., Du, Y. Y., Fu, M. X., Gao, G. H., Gao, H., Gao, M., Gu, Y. D., Guan, J., Gungor, C., Han, D. W., Huang, Y., Huo, J., Jia, S. M., Jiang, L. H., Jiang, W. C., Jin, J., Kong, L. D., Li, B., Li, C. K., Li, G., Li, M. S., Li, W., Li, X., Li, X. F., Li, Y. G., Li, Z. W., Liang, X. H., Liu, C. Z., Liu, G. Q., Liu, H. W., Liu, X. J., Liu, Y. N., Lu, B., Lu, X. F., Luo, Q., Luo, T., Ma, X., Meng, B., Nang, Y., Nie, J. Y., Ou, G., Sai, N., Song, S. X., Sun, L., Tan, Y., Tao, L., Tuo, Y. L., Wang, C., Wang, G. F., Wang, J., Wang, W. S., Wang, Y. S., Wen, X. Y., Wu, B. B., Wu, B. Y., Wu, M., Xiong, S. L., Yang, J. W., Yang, S., Yang, Y. J., Yin, Q. B., Yin, Q. Q., Zhang, A. M., Zhang, C. M., Zhang, F., Zhang, H. M., Zhang, J., Zhang, T., Zhang, W. C., Zhang, W. Z., Zhang, Y., Zhang, Y. F., Zhang, Y. J., Zhang, Z., Zhang, Z. L., Zhao, H. S., Zhao, X. F., Zheng, S. J., Zhou, J. F., Zhu, Y., and Zhu, Y. X.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

The long-term evolution of the centroid energy of the CRSF in Her X-1 is still a mystery. We report a new measurement from a campaign between {\sl Insight}-HXMT and {\sl NuSTAR} performed in February 2018. Generally, the two satellites show well consistent results of timing and spectral properties. The joint spectral analysis confirms that the previously observed long decay phase has ended, and that the line energy instead keeps constant around 37.5 keV after flux correction.

Published
2019

61. Ecophysiological and anatomical responses of Vallisneria natans to nitrogen and phosphorus enrichment

Author

Wang Y., Gao G., Qin B., and Wang X.

Subjects
nutrient enrichment, photosynthesis, morphological characteristics, anatomical structure, Vallisneria natans, Aquaculture. Fisheries. Angling, SH1-691
Abstract

Here, we describe an experiment using four nitrogen (N) and phosphorus (P) concentrations to investigate the effects of nutrient enrichment on the submersed macrophyte Vallisneria natans (tape grass) grown in a sand culture medium. The objective of this study was to examine the influence of nutrient enrichment in the water column on V. natans, especially with regard to anatomical structures. The results showed both the absolute growth rate (AGR) and intrinsic efficiency of light energy conversion of PSII (Fv/Fm) decreased with increasing nutrient levels. Root morphological characteristics, including the total root length (L), root surface area (SA), projected root area (PA), total root volume (V), average root diameter (AD), total root length per volume (LPV), total tips (T) and total forks (F), also showed a generally negative relationship with increasing nutrient concentrations. The anatomical structures of stolons and leaves also changed with nutrient enrichment. The shrinkage of aerenchyma and disappearance of starches and chloroplasts were the main structural changes leading to poor growth. These phenomena, especially the anatomical changes, might be the mechanism underlying the effect of nutrient enrichment on V. natans growth.

Published
2012
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62. An inverse vulcanized conductive polymer for Li-S battery cathodes

Author

Gao, G, Sun, X, and Wang, LW

Subjects
Macromolecular and Materials Chemistry, Materials Engineering, Interdisciplinary Engineering
Abstract

Polymers with a broad range of properties, structural diversity, and mechanical flexibility have been adopted in all aspects of Li-S batteries. However, currently explored polymers for Li-S cathodes suffer from low conductivity, low S content, and poor cycling performance. In this first-principles study, we theoretically design a new polymer, poly(2-vinyl,1,4-phenylene sulfide), by modifying the conductive poly(1,4-phenylene sulfide) via the vinyl group to enhance its ability to vulcanize with element S. We compare the properties of the experimentally realized sulfur vulcanized polymers via condensation and our designed sulfur vulcanized polymers via crosslinking as Li-S battery cathodes, in terms of gravimetric and specific capacities, as well as structural stability during the lithiation. Overall, we find that our designed polymer possesses better conductivity, higher specific capacity and gravimetric energy density, and better kinetic stability, and restricts the shuttle effect more efficiently than the current experimentally explored one. Also, the cross-linked sulfur compounds can be activated efficiently due to the short transport lengths rather than dissolution in the electrolyte during battery operation. Therefore, we believe our designed polymer cathode is promising for practical applications. This journal is

Published
2020

63. Substantial potential effects on single-atom catalysts for the oxygen evolution reaction simulated via a fixed-potential method

Author

Gao, G and Wang, LW

Subjects
Oxygen evolution reaction, Fixed-potential method, Fixed-charge method, Electrical energy, Chemical energy, Physical Chemistry, Chemical Engineering, Physical Chemistry (incl. Structural)
Abstract

Potential not only governs the direction of electrochemical reactions, but also shapes the electronic properties of single-atom catalysts dramatically. However, it is a challenge to simulate the effects of potential theoretically. Normally, DFT calculations are performed at a constant number of electrons, not a constant voltage. In this work, we apply a new fixed-potential method (grand canonical method) in the DFT simulation to mimic the electrochemical processes, in which the total number of the electron in the system was floated to match the ‘‘applied voltage,’, or the electrode Fermi energy at the atomic level. Here, the single-atom catalysts on two-dimension substrates for the oxygen evolution reaction process are used as examples to test the fixed-potential method. This fixed-potential method changes the rate-determining step and yields an overpotential difference of as much as 0.48 V in comparison with the conventional charge-neutral method. The quantitative error in the overpotential is not as important as the qualitative error in rate-determining steps. These errors can be avoided via the fixed-charge method with the proper charge. We believe our work advances the understanding of the effects of potential on the catalytic process in real electrochemical reactions and offers practical guidance for designing catalysts.

Published
2020

64. Hot disk of the Swift J0243.6+6124 revealed by Insight-HXMT

Author

Doroshenko, V., Zhang, S. N., Santangelo, A., Ji, L., Tsygankov, S., Mushtukov, A., Qu, L. J., Zhang, S., Ge, M. Y., Chen, Y. P., Bu, Q. C., Cao, X. L., Chang, Z., Chen, G., Chen, L., Chen, T. X., Chen, Y., Chen, Y. B., Cui, W., Cui, W. W., Deng, J. K., Dong, Y. W., Du, Y. Y., Fu, M. X., Gao, G. H., Gao, H., Gao, M., Gu, Y. D., Guan, Guo, C. C., Han, D. W., Hu, W., Huang, Y., Huo, J., Jia, S. M., Jiang, L. H., Jiang, W. C., Jin, J., Jin, Y. J., Kong, L. D., Li, B., Li, C. K., Li, G., Li, M. S., Li, T. P., Li, W., Li, X., Li, X. B., Li, X. F., Li, Y. G., Li, Z. J., Li, Z. W., Liang, X. H., Liao, J. Y., Liu, C. Z., Liu, G. Q., Liu, H. W., Liu, S. Z., Liu, X. J., Liu, Y., Liu, Y. N., Lu, B., Lu, F. J., Lu, X. F., Luo, T., Ma, X., Meng, B., Nang, Y., Nie, J. Y., Ou, G., Sai, N., Song, L. M., Song, X. Y., Sun, L., Tan, Y., Tao, L., Tuo, Y. L., Wang, G. F., Wang, J., Wang, W. S., Wang, Y. S., Wen, X. Y., Wu, B. B., Wu, M., Xiao, G. C., Xiong, S. L., Xu, H., Xu, Y. P., Yang, Y. R., Yang, J. W., Yang, S., Yang, Y. J., Zhang, A. M., Zhang, C. L., Zhang, C. M., Zhang, F., Zhang, H. M., Zhang, J., Zhang, Q., Zhang, T., Zhang, W., Zhang, W. C., Zhang, W. Z., Zhang, Y., Zhang, Y. F., Zhang, Y. J., Zhang, Z., Zhang, Z. L., Zhao, H. S., Zhao, J. L., Zhao, X. F., Zheng, S. J., Zhu, Y., Zhu, Y. X., and Zou, C. L.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We report on analysis of observations of the bright transient X-ray pulsar \src obtained during its 2017-2018 giant outburst with Insight-HXMT, \emph{NuSTAR}, and \textit{Swift} observatories. We focus on the discovery of a sharp state transition of the timing and spectral properties of the source at super-Eddington accretion rates, which we associate with the transition of the accretion disk to a radiation pressure dominated (RPD) state, the first ever directly observed for magnetized neutron star. This transition occurs at slightly higher luminosity compared to already reported transition of the source from sub- to super-critical accretion regime associate with onset of an accretion column. We argue that this scenario can only be realized for comparatively weakly magnetized neutron star, not dissimilar to other ultra-luminous X-ray pulsars (ULPs), which accrete at similar rates. Further evidence for this conclusion is provided by the non-detection of the transition to the propeller state in quiescence which strongly implies compact magnetosphere and thus rules out magnetar-like fields., Comment: Submitted to MNRAS

Published
2019
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65. In-orbit demonstration of X-ray pulsar navigation with the Insight-HXMT satellite

Author

Zheng, S. J., Zhang, S. N., Lu, F. J., Wang, W. B., Gao, Y., Li, T. P., Song, L. M., Ge, M. Y., Han, D. W., Chen, Y., Xu, Y. P., Cao, X. L., Liu, C. Z., Zhang, S., Qu, J. L., Chang, Z., Chen, G., Chen, L., Chen, T. X., Chen, Y. B., Chen, Y. P., Cui, W., Cui, W. W., Deng, J. K., Dong, Y. W., Du, Y. Y., Fu, M. X., Gao, G. H., Gao, H., Gao, M., Gu, Y. D., Guan, J., Gungor, C., Guo, C. C., Hu, W., Huang, Y., Huo, J., Ji, J. F., Jia, S. M., Jiang, L. H., Jiang, W. C., Jin, J., Jin, Y. J., Li, B., Li, C. K., Li, G., Li, M. S., Li, W., Li, X., Li, X. B., Li, X. F., Li, Y. G., Li, Z. J., Li, Z. W., Liang, X. H., Liao, J. Y., Liu, G. Q., Liu, H. W., Liu, S. Z., Liu, X. J., Liu, Y., Liu, Y. N., Lu, B., Lu, X. F., Luo, T., Ma, X., Meng, B., Nang, Y., Nie, J. Y., Ou, G, Sai, N., Shang, R. C., Sun, L., Tan, Y., Tao, L., Tao, W., Tuo, Y. L., Wang, G. F., Wang, J., Wang, W. S., Wang, Y. S., Wen, X. Y., Wu, B. B., Wu, M., Xiao, G. C., Xiong, S. L., Xu, H., Yan, L. L., Yang, J. W., Yang, S., Yang, Y. J., Zhang, A. M., Zhang, C. L., Zhang, C. M., Zhang, F., Zhang, H. M., Zhang, J., Zhang, Q., Zhang, T., Zhang, W., Zhang, W. C., Zhang, W. Z., Zhang, Y., Zhang, Y. F., Zhang, Y. J., Zhang, Z., Zhang, Z. L., Zhao, H. S., Zhao, J. L., Zhao, X. F., Zhu, Y., Zhu, Y. X., and Zou, C. L.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

In this work, we report the in-orbit demonstration of X-ray pulsar navigation with Insight-Hard X-ray Modulation Telescope (Insight-HXMT), which was launched on Jun. 15th, 2017. The new pulsar navigation method 'Significance Enhancement of Pulse-profile with Orbit-dynamics' (SEPO) is adopted to determine the orbit with observations of only one pulsar. In this test, the Crab pulsar is chosen and observed by Insight-HXMT from Aug. 31th to Sept. 5th in 2017. Using the 5-day-long observation data, the orbit of Insight-HXMT is determined successfully with the three telescopes onboard - High Energy X-ray Telescope (HE), Medium Energy X-ray Telescope (ME) and Low Energy X-ray Telescope (LE) - respectively. Combining all the data, the position and velocity of the Insight-HXMT are pinpointed to within 10 km (3 sigma) and 10 m/s (3 sigma), respectively., Comment: Accepted by the Astrophysical Journal Supplement

Published
2019
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66. Absence of quantum-confined Stark effect in GaN quantum disks embedded in (Al,Ga)N nanowires grown by molecular beam epitaxy

Author

Sinito, C., Corfdir, P., Pfüller, C., Gao, G., Vílchez, J. Bartolomé, Kölling, S., Doblado, A. Rodil, Jahn, U., Lähnemann, J., Auzelle, T., Zettler, J. K., Flissikowski, T., Koenraad, P., Grahn, H. T., Geelhaar, L., Fernández-Garrido, S., and Brandt, O.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Physics - Applied Physics
Abstract

Several of the key issues of planar (Al,Ga)N-based deep-ultraviolet light emitting diodes could potentially be overcome by utilizing nanowire heterostructures, exhibiting high structural perfection and improved light extraction. Here, we study the spontaneous emission of GaN/(Al,Ga)N nanowire ensembles grown on Si(111) by plasma-assisted molecular beam epitaxy. The nanowires contain single GaN quantum disks embedded in long (Al,Ga)N nanowire segments essential for efficient light extraction. These quantum disks are found to exhibit intense emission at unexpectedly high energies, namely, significantly above the GaN bandgap, and almost independent of the disk thickness. An in-depth investigation of the actual structure and composition of the nanowires reveals a spontaneously formed Al gradient both along and across the nanowire, resulting in a complex core/shell structure with an Al deficient core and an Al rich shell with continuously varying Al content along the entire length of the (Al,Ga)N segment. This compositional change along the nanowire growth axis induces a polarization doping of the shell that results in a degenerate electron gas in the disk, thus screening the built-in electric fields. The high carrier density not only results in the unexpectedly high transition energies, but also in radiative lifetimes depending only weakly on temperature, leading to a comparatively high internal quantum efficiency of the GaN quantum disks up to room temperature., Comment: This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Nano Letters (2019), copyright (C) American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/acs.nanolett.9b01521, the supporting information is available (free of charge) under the same link

Published
2019
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67. Synthesis of two-dimensional van der waals superlattices, heterostructures, and alloys from conversion of sequentially layered sub-nanometer metal films

Author

Motala, M.J., Zhang, X., Kumar, P., Oliveira, E.F., Benton, A., Miesle, P., Rao, R., Stevenson, P.R., Moore, D., Alfieri, A., Lynch, J., Austin, D., Post, S., Gao, G., Ma, S., Zhu, H., Wang, Z., Petrov, I., Stach, E.A., Kennedy, W.J., Vangala, S., Tour, J.M., Galvao, D.S., Jariwala, D., Muratore, C., Snure, M., Ajayan, P.M., and Glavin, N.R.

Published
2023
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69. Solid 3D Li-S Battery Design via Stacking 2D Conductive Microporous Coordination Polymers and Amorphous Li-S Layers

Author

Gao, G, Zheng, F, and Wang, LW

Subjects
Materials, Chemical Sciences, Engineering
Abstract

To make a lithium-sulfur (Li-S) battery practical, not only high gravimetric energy capacity is important, but also high volumetric energy capacity will be required. The currently explored Li-S cathode designs often deploy systems with liquid electrolyte infiltration, hence with relatively low volumetric capacity. In the current study, we theoretically test a compact solid three-dimensional (3D) design (more like a Li-ion battery cathode than a conventional Li-S cathode) consisted of a sandwich structure alternating between the two-dimensional (2D) Mn-hexaaminobenzene-based coordination polymer (2D Mn-HAB-CP) layer and the amorphous Li-S layer. We study the theoretical limits for both its gravimetric and volumetric energy capacity, as well as its structural stability and Li diffusion within the cathode system. To study the Li diffusion within an amorphous system, we also develop a pull-atom molecular dynamics (PA-MD) to calculate the barrier heights of such disordered systems. We reveal the mechanism that determines the Li diffusion in the amorphous layer of the system. Overall, we find such a 3D solid Li-S cathode can be practical, with sufficient large gravimetric and volumetric energy capacity, as well as the Li diffusion constant. It also solves many other common Li-S cathode problems, from Li polysulfide dissolution to electrical insulating, and structure instabilities.

Published
2020

70. Computational screening of transition metal-doped phthalocyanine monolayers for oxygen evolution and reduction

Author

Zhou, Y, Gao, G, Chu, W, and Wang, LW

Abstract

Rationally designing efficient, low-cost and stable catalysts toward the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) is of significant importance to the development of renewable energy technologies. In this work, we have systematically investigated a series of potentially efficient and stable single late transition metal atom doped phthalocyanines (TM@Pcs, TM = Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ir and Pt) as single-atom catalysts (SACs) for applications toward the OER and ORR through a computational screening approach. Our calculations indicate that TM atoms can tightly bind with Pc monolayers with high diffusion energy barriers to prevent the isolated atoms from clustering. The interaction strength between intermediates and TM@Pc governs the catalytic activities for the OER and ORR. Among all the considered TM@Pc catalysts, Ir@Pc and Rh@Pc were found to be efficient OER electrocatalysts with overpotentials ηOER of 0.41 and 0.44 V, respectively, and for the ORR, Rh@Pc exhibits the lowest overpotential ηORR of 0.44 V followed by Ir@Pc (0.55 V), suggesting that Rh@Pc is an efficient bifunctional catalyst for both the OER and ORR. Moreover, it is worth noting that the Rh@Pc catalyst can remain stable against dissolution under the pH = 0 condition. Ab initio molecular dynamic calculations suggest that Rh@Pc could remain stable at 300 K. Our findings highlight a novel family of two-dimensional (2D) materials as efficient and stable SACs and offer a new strategy for catalyst design.

Published
2020

74. Insight-HXMT observations of the New Black Hole Candidate MAXI J1535-571: timing analysis

Author

Huang, Y., Qu, J. L., Zhang, S. N., Bu, Q. C., Chen, Y. P., Tao, L., Zhang, S., Lu, F. J., Li, T. P., Song, L. M., Xu, Y. P., Cao, X. L., Chen, Y., Liu, C. Z., Chang, H. -K., Yu, W. f., Weng, S. S., Hou, X., Kong, A. K. H., Xie, F. G., Zhang, G. B., ZHOU, J. F., Chang, Z., Chen, G., Chen, L., Chen, T. X., Chen, Y. B., Cui, W., Cui, W. W., Deng, J. K., Dong, Y. W., Du, Y. Y., Fu, M. X., Gao, G. H., Gao, H., Gao, M., Ge, M. Y., Gu, Y. D., Guan, J., Gungor, C., Guo, C. C., Han, D. W., Hu, W., Huo, J., Ji, J. F., Jia, S. M., Jiang, L. H., Jiang, W. C., Jin, J., Jin, Y. J., Li, B., Li, C. K., Li, G., Li, M. S., Li, W., Li, X., Li, X. B., Li, X. F., Li, Y. G., Li, Z. J., Li, Z. W., Liang, X. H., Liao, J. Y., Liu, G. Q., Liu, H. W., Liu, S. Z., Liu, X. J., Liu, Y., Liu, Y. N., Lu, B., Lu, X. F., Luo, T., Ma, X., Meng, B., Nang, Y., Nie, J. Y., Ou, G, Sai, N., Shang, R. C., Sun, L., Tan, Y., Tao, W., Tuo, Y. L., Wang, G. F., Wang, H. Y., Wang, J., Wang, W. S., Wang, Y. S., Wen, X. Y., Wu, B. B., Wu, M., Xiao, G. C., Xiong, S. L., Xu, H., Yan, L. L., Yang, J. W., Yang, S., Yang, Y. J., Zhang, A. M., Zhang, C. L., Zhang, C. M., Zhang, F., Zhang, H. M., Zhang, J., Zhang, Q., Zhang, T., Zhang, W., Zhang, W. C., Zhang, W. Z., Zhang, Y., Zhang, Y. F., Zhang, Y. J., Zhang, Z., Zhang, Z. L., Zhao, H. S., Zhao, J. L., Zhao, X. F., Zheng, S. J., Zhu, Y., Zhu, Y. X., and Zou, C. L.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We present the X-ray timing results of the new black hole candidate (BHC) MAXI J1535-571 during its 2017 outburst from Hard X-ray Modulation Telescope (\emph{Insight}-HXMT) observations taken from 2017 September 6 to 23. Following the definitions given by \citet{Belloni2010}, we find that the source exhibits state transitions from Low/Hard state (LHS) to Hard Intermediate state (HIMS) and eventually to Soft Intermediate state (SIMS). Quasi-periodic oscillations (QPOs) are found in the intermediate states, which suggest different types of QPOs. With the large effective area of \emph{Insight}-HXMT at high energies, we are able to present the energy dependence of the QPO amplitude and centroid frequency up to 100 keV which is rarely explored by previous satellites. We also find that the phase lag at the type-C QPOs centroid frequency is negative (soft lags) and strongly correlated with the centroid frequency. By assuming a geometrical origin of type-C QPOs, the source is consistent with being a high inclination system., Comment: 12 pages, 11 figures, Sumbitted to ApJ

Published
2018
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75. Decimetric emission 500$'$ away from a flaring Site: Possible scenarios from ${\textit{GMRT}}$ solar radio observations

Author

Bisoi, Susanta Kumar, Sawant, H. S., Janardhan, P., Yan, Y., Chen, L., Awasthi, Arun Kumar, Srivastava, Shweta, and Gao, G.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

We present a study of decimetric radio activity, using the first high time cadence (0.5 s) images from the ${\textit{Giant Meterwave Radio Telescope}}$ (${\textit{GMRT}}$) at 610 MHz, associated with ${\textit{GOES}}$ C1.4 and M1.0 class solar flares, and a coronal mass ejection (CME) onset that occurred on 20 June 2015. The high spatial resolution images from ${\textit{GMRT}}$ show a strong radio source during the C1.4 flare, located ~500$''$ away from the flaring site with no corresponding bright footpoints or coronal features nearby. In contrast, however, strong radio sources are found near the flaring site during the M1.0 flare and around the CME onset time. Weak radio sources, located near the flaring site, are also found during the maximum of the C1.4 flare activity, which show a temporal association with metric type III bursts identified by the Solar Broadband Radio Spectrometer at Yunnan Astronomical Observatory. Based on a multi-wavelength analysis and magnetic potential field source surface extrapolations, we suggest that the source electrons of ${\textit{GMRT}}$ radio sources and metric type III bursts were originated from a common electron acceleration site. We also show that the strong ${\textit{GMRT}}$ radio source is generated by a coherent emission process and its apparent location far from the flaring site is possibly due to the wave-ducting effect., Comment: 24 Pages, 11 figures, accepted for publication in ApJ

Published
2018
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80. Theoretical Investigation of 2D Conductive Microporous Coordination Polymers as Li–S Battery Cathode with Ultrahigh Energy Density

Author

Gao, G, Zheng, F, Pan, F, and Wang, LW

Subjects
2D hexaaminobenzene-based coordination polymers, cathode materials, Li-S batteries, Macromolecular and Materials Chemistry, Materials Engineering, Interdisciplinary Engineering
Abstract

Even though tremendous achievement has been made experimentally in the performance of lithium–sulfur (Li–S) battery, theoretical studies in this area are lagging behind due to the complexity of the Li–S systems and the effects of solvent. For this purpose, a new methodology is developed for investigating the 2D hexaaminobenzene-based coordination polymers (2D-HAB-CPs) as cathode candidate materials for Li–S batteries via density functional theory calculations in combination with an in-house developed charge polarized solvent model and a genetic algorithm structure global search code. With high ratios of transition metal atoms and two-coordinated nitrogen atoms, excellent electric conductivity, and structural porosity, the 2D-HAB-CP is able to address all of the three main challenges facing Li–S batteries: confining the lithium polysulfides from dissolution, facilitating the electron conductivity and buffering the volumetric expansion during the lithiation process. In addition, the theoretical energy density of this system is as high as 1395 Wh kg−1. These results demonstrate that the 2D-HAB-CP is a promising cathode material for Li–S batteries. The proposed computational framework not only opens a new avenue for understanding the key role played by solution and liquid electrolytes in Li–S batteries, but also can be generally applied to other processes with liquids involved.

Published
2018

81. Computational Electrocatalysis beyond Conventional Hydrogen Electrode Model: CO2Reduction to C2Species on Copper Facilitated by Dynamically Formed Solvent Halide Ions at the Solid-Liquid Interface

Author

Mao, Xin, primary, He, Tianwei, additional, Kour, Gurpreet, additional, Yin, Hanqing, additional, Ling, Chongyi, additional, Gao, G., additional, Jin, Yonggang, additional, Liu, Qingju, additional, O'Mullane, Anthony Peter, additional, and Du, Aijun, additional

Published
2024
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83. 2D MXenes: A New Family of Promising Catalysts for the Hydrogen Evolution Reaction

Author

Gao, G, O'Mullane, AP, and Du, A

Subjects
water splitting, surface Pourbaix diagrams, termination, volcano curve, Gibbs free energy of hydrogen adsorption, functional groups, Inorganic Chemistry, Organic Chemistry, Chemical Engineering
Abstract

Developing highly conductive, stable, and active nonprecious hydrogen evolution reaction (HER) catalysts is a key step for the proposed hydrogen economy. However, few catalysts, except for noble metals, meet all the requirements. By using state-of-the-art density functional calculations, herein we demonstrate that 2D MXenes, like Ti2C, V2C, and Ti3C2, are terminated by a mixture of oxygen atoms and hydroxyl, while Nb2C and Nb4C3O2 are fully terminated by oxygen atoms under standard conditions [pH 0, p(H2) = 1 bar, U = 0 V vs standard hydrogen electrode], findings in good agreement with experimental observation. Furthermore, all these MXenes are conductive under standard conditions, thus allowing high charge transfer kinetics during the HER. Remarkably, the Gibbs free energy for the adsorption of atomic hydrogen (ΔGH∗0) on the terminated O atoms (e.g., Ti2CO2) is close to the ideal value (0 eV). Our results demonstrate terminated oxygens as catalytic active sites for the HER at these materials and highlight a family of promising two-dimensional catalysts for water splitting. (Chemical Equation Presented).

Published
2017

85. HXMT identification of a non-thermal X-ray burst from SGR J1935+2154 and with FRB 200428

Author

Li, C. K., Lin, L., Xiong, S. L., Ge, M. Y., Li, X. B., Li, T. P., Lu, F. J., Zhang, S. N., Tuo, Y. L., Nang, Y., Zhang, B., Xiao, S., Chen, Y., Song, L. M., Xu, Y. P., Liu, C. Z., Jia, S. M., Cao, X. L., Qu, J. L., Zhang, S., Gu, Y. D., Liao, J. Y., Zhao, X. F., Tan, Y., Nie, J. Y., Zhao, H. S., Zheng, S. J., Zheng, Y. G., Luo, Q., Cai, C., Li, B., Xue, W. C., Bu, Q. C., Chang, Z., Chen, G., Chen, L., Chen, T. X., Chen, Y. B., Chen, Y. P., Cui, W., Cui, W. W., Deng, J. K., Dong, Y. W., Du, Y. Y., Fu, M. X., Gao, G. H., Gao, H., Gao, M., Gu, Y. D., Guan, J., Guo, C. C., Han, D. W., Huang, Y., Huo, J., Jiang, L. H., Jiang, W. C., Jin, J., Jin, Y. J., Kong, L. D., Li, G., Li, M. S., Li, W., Li, X., Li, X. F., Li, Y. G., Li, Z. W., Liang, X. H., Liu, B. S., Liu, G. Q., Liu, H. W., Liu, X. J., Liu, Y. N., Lu, B., Lu, X. F., Luo, T., Ma, X., Meng, B., Ou, G., Sai, N., Shang, R. C., Song, X. Y., Sun, L., Tao, L., Wang, C., Wang, G. F., Wang, J., Wang, W. S., Wang, Y. S., Wen, X. Y., Wu, B. B., Wu, B. Y., Wu, M., Xiao, G. C., Xu, H., Yang, J. W., Yang, S., Yang, Y. J., Yang, Yi-Jung, Yi, Q. B., Yin, Q. Q., You, Y., Zhang, A. M., Zhang, C. M., Zhang, F., Zhang, H. M., Zhang, J., Zhang, T., Zhang, W., Zhang, W. C., Zhang, W. Z., Zhang, Y., Zhang, Yue, Zhang, Y. F., Zhang, Y. J., Zhang, Z., Zhang, Zhi, Zhang, Z. L., Zhou, D. K., Zhou, J. F., Zhu, Y., Zhu, Y. X., and Zhuang, R. L.

Published
2021
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86. Examining the thermal conductivity of half-Heusler alloy TiNiSn by first-principles calculations

Author

Ding, Guangqian, Gao, G. Y., and Yao, K. L.

Subjects
Condensed Matter - Materials Science
Abstract

The thermoelectric properties of half-Heusler alloy TiNiSn have been studied for decade, however, theoretical report on its thermal conductivity is still little known, because it is difficult to estimate effectively the lattice thermal conductivity. In this work, we use the ShengBTE code developed recently to examine the lattice thermal conductivity of TiNiSn. The calculated lattice thermal conductivity at room temperature is 7.6 W/mK, which is close to the experimental value of 8 W/mK. We also find that the total and lattice thermal conductivities dependent temperature are in good agreement with available experiments, and the total thermal conductivity is dominated by the lattice contribution. The present work is useful for the theoretical prediction of lattice thermal conductivity and the optimization of thermoelectric performance., Comment: Accepted by J. Phys. D on 14-4-2015

Published
2015
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91. OA21.04 Amivantamab in Patients with Advanced NSCLC and MET Exon 14 Skipping Mutation: Results from the CHRYSALIS Study

Author

Leighl, N., primary, Cho, B.C., additional, Hiret, S., additional, Han, J.-Y., additional, Lee, K.H., additional, Llacer Perez, C., additional, Krebs, M.G., additional, De Braud, F., additional, Haura, E., additional, Sanborn, R.E., additional, Yang, J.C.-H., additional, Shu, C.A., additional, Goto, K., additional, Nishio, M., additional, Zhao, J., additional, Wang, Z., additional, Tomasini, P., additional, Felip, E., additional, Goldman, J.W., additional, Ou, S.-H.I., additional, Boyer, M., additional, Gao, G., additional, Qu, S., additional, Curtin, J.C., additional, Lyu, X., additional, Roshak, A., additional, Schnepp, R.W., additional, Kim, P., additional, Mertz, J., additional, Thayu, M., additional, Shreeve, S.M., additional, Knoblauch, R.E., additional, and Spira, A.I., additional

Published
2023
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96. Heteroepitaxial Growth and Multiferroic Properties of Mn-doped BiFeO3 films on SrTiO3 buffered III-V Semiconductor GaAs

Author

Gao, G. Y., Yang, Z. B., Huang, W., Zeng, H. Z., Wang, Y., Chan, H. L. W., Wu, W. B., and Hao, J. H.

Subjects
Condensed Matter - Materials Science
Abstract

Epitaxial Mn-doped BiFeO3 (MBFO) thin films were grown on GaAs (001) substrate with SrTiO3 (STO) buffer layer by pulsed laser deposition. X-ray diffraction results demonstrate that the films show pure (00l) orientation, and MBFO(100)//STO(100), whereas STO (100)//GaAs (110). Piezoresponse force microscopy images and polarization versus electric field loops indicate that the MBFO films grown on GaAs have an effective ferroelectric switching. The MBFO films exhibit good ferroelectric behavior (2Pr ~ 92 {\mu}C/cm2 and 2EC ~ 372 kV/cm). Ferromagnetic property with saturated magnetization of 6.5 emu/cm3 and coercive field of about 123 Oe is also found in the heterostructure at room temperature., Comment: 19 pages, 4 figures

Published
2013
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99. Bedaquiline and clofazimine resistance in Mycobacterium tuberculosis: an in-vitro and in-silico data analysis

Author

Sonnenkalb, L, Carter, JJ, Spitaleri, A, Iqbal, Z, Hunt, M, Malone, KM, Utpatel, C, Cirillo, DM, Rodrigues, C, Nilgiriwala, KS, Fowler, PW, Merker, M, Niemann, S, Barilar, I, Battaglia, S, Borroni, E, Brandao, AP, Brankin, A, Cabibbe, AM, Carter, J, Claxton, P, Clifton, DA, Cohen, T, Coronel, J, Crook, DW, Dreyer, V, Earle, SG, Escuyer, V, Ferrazoli, L, Fu Gao, G, Gardy, J, Gharbia, S, Ghisi, KT, Ghodousi, A, Gibertoni Cruz, AL, Grandjean, L, Grazian, C, Groenheit, R, Guthrie, JL, He, W, Hoffmann, H, Hoosdally, SJ, Ismail, NA, Jarrett, L, Joseph, L, Jou, R, Kambli, P, Khot, R, Knaggs, J, Koch, A, Kohlerschmidt, D, Kouchaki, S, Lachapelle, AS, Lalvani, A, Grandjean Lapierre, S, Laurenson, IF, Letcher, B, Lin, W-H, Liu, C, Liu, D, Mandal, A, Mansjö, M, Matias, D, Meintjes, G, De Freitas Mendes, F, Mihalic, M, Millard, J, Miotto, P, Mistry, N, Moore, D, Musser, KA, Ngcamu, D, Hoang, NN, Nimmo, C, Okozi, N, Oliveira, RS, Omar, SV, Paton, N, Peto, TEA, Watanabe Pinhata, JM, Plesnik, S, Puyen, ZM, Rabodoarivelo, MS, Rakotosamimanana, N, Rancoita, PMV, Rathod, P, Rodger, G, Rodwell, TC, Roohi, E, Santos-Lazaro, D, Shah, S, Kohl, TA, Smith, G, Solano, W, Supply, P, Surve, U, Tahseen, S, Thuong, NTT, Thwaites, G, Todt, K, Trovato, A, Van Rie, A, Vijay, S, Walker, TM, Walker, SA, Warren, R, Werngren, J, Wijkander, M, Wilkinson, RJ, Wilson, DJ, Wintringer, P, Yu, XX, Yang, Y, Zhao, Y, Yao, S-Y, Zhu, B, and Consortium, Comprehensive Resistance Prediction for Tuberculosis: an International

Subjects
Microbiology (medical), Infectious Diseases, Virology, Microbiology
Abstract

Background Bedaquiline is a core drug for the treatment of multidrug-resistant tuberculosis; however, the understanding of resistance mechanisms is poor, which is hampering rapid molecular diagnostics. Some bedaquiline-resistant mutants are also cross-resistant to clofazimine. To decipher bedaquiline and clofazimine resistance determinants, we combined experimental evolution, protein modelling, genome sequencing, and phenotypic data. Methods For this in-vitro and in-silico data analysis, we used a novel in-vitro evolutionary model using subinhibitory drug concentrations to select bedaquiline-resistant and clofazimine-resistant mutants. We determined bedaquiline and clofazimine minimum inhibitory concentrations and did Illumina and PacBio sequencing to characterise selected mutants and establish a mutation catalogue. This catalogue also includes phenotypic and genotypic data of a global collection of more than 14 000 clinical Mycobacterium tuberculosis complex isolates, and publicly available data. We investigated variants implicated in bedaquiline resistance by protein modelling and dynamic simulations. Findings We discerned 265 genomic variants implicated in bedaquiline resistance, with 250 (94%) variants affecting the transcriptional repressor (Rv0678) of the MmpS5–MmpL5 efflux system. We identified 40 new variants in vitro, and a new bedaquiline resistance mechanism caused by a large-scale genomic rearrangement. Additionally, we identified in vitro 15 (7%) of 208 mutations found in clinical bedaquiline-resistant isolates. From our in-vitro work, we detected 14 (16%) of 88 mutations so far identified as being associated with clofazimine resistance and also seen in clinically resistant strains, and catalogued 35 new mutations. Structural modelling of Rv0678 showed four major mechanisms of bedaquiline resistance: impaired DNA binding, reduction in protein stability, disruption of protein dimerisation, and alteration in affinity for its fatty acid ligand. Interpretation Our findings advance the understanding of drug resistance mechanisms in M tuberculosis complex strains. We have established an extended mutation catalogue, comprising variants implicated in resistance and susceptibility to bedaquiline and clofazimine. Our data emphasise that genotypic testing can delineate clinical isolates with borderline phenotypes, which is essential for the design of effective treatments. Funding Leibniz ScienceCampus Evolutionary Medicine of the Lung, Deutsche Forschungsgemeinschaft, Research Training Group 2501 TransEvo, Rhodes Trust, Stanford University Medical Scientist Training Program, National Institute for Health and Care Research Oxford Biomedical Research Centre, Oxford University Hospitals NHS Foundation Trust, Bill & Melinda Gates Foundation, Wellcome Trust, and Marie Skłodowska-Curie Actions.

Published
2023

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