 Subjects -> ASTRONOMY (Total: 94 journals)
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- The local and global properties of different types of supernova host
galaxies- Authors: Li Zhou; Yan-Chun Liang, Jun-Qiang Ge, Yi-Nan Zhu, Xu Shao, Hong Wu, Wei-Bin Shi Li-Cai Deng
First page: 169
Abstract: By using Data Analysis Pipeline (DAP) products of Mapping Nearby Galaxies at Apache Point
Observatory (MaNGA), which are publicly available from the SDSS Data Release 15, we analyze the
local properties at the SN explosion sites and global properties of different types of SN host
galaxies to explore the explosion environments of different types of SNe. In our sample, there are
67 SN host galaxies in the field of view of MaNGA, including 32 Type Ia, 29 core collapse SNe
(CCSNe), 1 superluminous SN (SLSN), 1 Type I and 4 unclassified type of SNe, with which we can apply
the K-S test for analysis and derive statistically robust results. Due to the limited sample size,
we could not remove the mass dependence in this work, which is likely the true driver of the trends
for the properties presented in this work. The global star formation rate (SFR) and EW(H α ) for SN
Ia hosts are slightly lower than those for CCSN hosts on average. SN Ia host galaxies are ∼0.3 dex
more massive th...
Citation: Research in Astronomy and Astrophysics
PubDate: 2020-11-25T00:00:00Z
DOI: 10.1088/1674-4527/20/11/169
Issue No: Vol. 20, No. 11 (2020)
- Solar image deconvolution by generative adversarial network
- Authors: Long Xu; Wen-Qing Sun, Yi-Hua Yan Wei-Qiang Zhang
First page: 170
Abstract: With aperture synthesis (AS) technique, a number of small antennas can be assembled to form a large
telescope whose spatial resolution is determined by the distance of two farthest antennas instead of
the diameter of a single-dish antenna. In contrast from a direct imaging system, an AS telescope
captures the Fourier coefficients of a spatial object, and then implement inverse Fourier transform
to reconstruct the spatial image. Due to the limited number of antennas, the Fourier coefficients
are extremely sparse in practice, resulting in a very blurry image. To remove/reduce blur, “CLEAN”
deconvolution has been widely used in the literature. However, it was initially designed for a point
source. For an extended source, like the Sun, its efficiency is unsatisfactory. In this study, a
deep neural network, referring to Generative Adversarial Network (GAN), is proposed for solar image
deconvolution. The experimental results demonstrate that the proposed model is markedly better than
...
Citation: Research in Astronomy and Astrophysics
PubDate: 2020-11-25T00:00:00Z
DOI: 10.1088/1674-4527/20/11/170
Issue No: Vol. 20, No. 11 (2020)
- A new correction method for quasi-Keplerian orbits
- Authors: Yue Chen; Da-Zhu Ma Fang Xia
First page: 171
Abstract: A pure two-body problem has seven integrals including the Kepler energy, the Laplace vector and the
angular momentum vector. However, only five of them are independent. When the five independent
integrals are preserved, the two other dependent integrals are naturally preserved from a
theoretical viewpoint; but they may not necessarily be from a numerical computational viewpoint.
Because of this, we use seven scale factors to adjust the integrated positions and velocities so
that the adjusted solutions strictly satisfy the seven constraints. Noticing the existence of the
two dependent integrals, we adopt the Newton iterative method combined with singular value
decomposition to calculate these factors. This correction scheme can be applied to perturbed
two-body and N -body problems in the solar system. In this case, the seven quantities associated
with each planet slowly vary with time. More accurate values can be given to the seven
slowly-varying quantities by integrating t...
Citation: Research in Astronomy and Astrophysics
PubDate: 2020-11-25T00:00:00Z
DOI: 10.1088/1674-4527/20/11/171
Issue No: Vol. 20, No. 11 (2020)
- The correlations among variability, optical peak time and spectral time
lag of long gamma-ray bursts- Authors: Bin Liao; Yuan-Chuan Zou, Fei-Fei Wang, Yu Liu Wei-Hua Lei
First page: 172
Abstract: Statistical relations are useful tools to comprehend the intrinsic physics processes of gamma-ray
bursts (GRBs). In this work we collect spectral lag ( τ ), variability ( V ) and optical peak time (
t p,o ). We find that there is a correlation between variabilities and spectral lags, reading as V =
−0.0075 (±0.0007) × log 10 τ + 0.0351 (±0.0024). There may also exist a relatively weak positive
tendency between GRBs optical band peak times and their spectral time lags. Its Pearson coefficient
is 0.398, which indicates a weak linear correlation. If we contain some “negative spectral lag”
samples, then the latter relation would be worse due to two outlying points. The τ - V relation is
consistent with previous studies, and the positive trend between τ and t p,o indicates the spectral
lag of GRB might be caused by the curvature effect, but this conclusion is not significant.
Citation: Research in Astronomy and Astrophysics
PubDate: 2020-11-25T00:00:00Z
DOI: 10.1088/1674-4527/20/11/172
Issue No: Vol. 20, No. 11 (2020)
- The effect of hydrodynamics alone on the subhalo population in a ΛCDM
rich cluster sized dark matter
halo- Authors: Jun-Yi Jia; Liang Gao Yan Qu
First page: 174
Abstract: We perform a set of non-radiative hydro-dynamical (NHD) simulations of a rich cluster sized dark
matter halo from the Phoenix Project with three different numerical resolutions, to investigate the
effect of hydrodynamics alone on the subhalo population in the halo. Compared to dark matter only
(DMO) simulations of the same halo, subhaloes are less abundant for relatively massive subhaloes ( M
sub> 2.5 × 10 9 h −1 M ⊙ , or V max> 70 km s −1 ) but more abundant for less massive subhaloes in
the NHD simulations. This results in different shapes in the subhalo mass/ V max function in two
different sets of simulations. At given subhalo mass, the subhaloes less massive than 10 10 h −1 M ⊙
have larger V max in the NHD than DMO simulations, while V max is similar for the subhaloes more
massive ...
Citation: Research in Astronomy and Astrophysics
PubDate: 2020-11-25T00:00:00Z
DOI: 10.1088/1674-4527/20/11/174
Issue No: Vol. 20, No. 11 (2020)
- Accretion flow properties of XTE J1118+480 during its 2005 outburst
- Authors: Dipak Debnath; Debjit Chatterjee, Arghajit Jana, Sandip K. Chakrabarti Kaushik Chatterjee
First page: 175
Abstract: We study spectral and temporal properties of Galactic short orbital period transient black hole XTE
J1118+480 during its 2005 outburst using archival data of RXTE PCA and HEXTE instruments in the
combined energy range of 3 – 100 keV. Spectral analysis with the physical two component advective
flow (TCAF) model allows us to understand the accretion flow properties of the source. We found that
this outburst of XTE J1118+480 is an unconventional outburst as the source was only in the hard
state (HS). Our spectral analysis suggests that during the entire outburst, the source was highly
dominated by the low angular momentum sub-Keplerian halo rate. Since the source was active in radio
throughout the outburst, we make an effort to estimate X-ray contribution of jets to total observed
X-ray emissions from the spectral analysis with the TCAF model. The total X-ray intensity shows a
similar nature of evolution as that of radio and jet X-ray fluxes. This allowed us to define this
‘outburs...
Citation: Research in Astronomy and Astrophysics
PubDate: 2020-11-25T00:00:00Z
DOI: 10.1088/1674-4527/20/11/175
Issue No: Vol. 20, No. 11 (2020)
- The first results of observations of lunar occultations in different
spectral ranges at the 6-m
telescope of the SAO RAS- Authors: Ekaterina Shmaylova; Vladimir Dyachenko, Andrea Richichi, Anatoly Beskakotov, Aleksandr Maksimov, Arina Mitrofanova Yuri Balega
First page: 176
Abstract: Observations by the method of lunar occultations at the 6-m telescope of the SAO RAS reach a
resolution limit better than 1 mas. We have devised a new method of observation, which allows
obtaining the curves of lunar occultations simultaneously in different ranges of the visible part of
the spectrum, and conducted the first observations using a modified optical system. In January 2019,
applying the new method, the magnitude differences of the components of the binary star HD 36524 in
the R and I bands were measured, which were 1.5 and 1.3 mag, respectively, in good agreement with
values calculated from the Gaia mission. According to the obtained data, it was determined that with
this method it is possible to reach a signal-to-noise ratio of about 5–10 for stars of 10th
magnitude. We discuss the applicability of the proposed optical scheme for the study of binary
stars.
Citation: Research in Astronomy and Astrophysics
PubDate: 2020-11-25T00:00:00Z
DOI: 10.1088/1674-4527/20/11/176
Issue No: Vol. 20, No. 11 (2020)
- Carbon star CGCS 673 identified as a semi-regular variable star
- Authors: Stephen M. Brincat; Charles Galdies Kevin Hills
First page: 177
Abstract: This study reports that the carbon star CGCS 673 is a semi-regular (SR) variable star with a period
of 135 d and an amplitude of 0.18 mag in the V -band. The light curve obtained by this study
correlates well with the SR classification as the photometric data obtained show noticeable
periodicity in the light changes of CGCS 673 that is occasionally interrupted by a period of
irregular variability. The derived period and colour index obtained from our data and those from
professional databases indicate that the attributes of this star fall within the parameters of the
SR class of variable stars. Following our notification of the discovery that this star is a variable
source, CGCS 673 has received the AAVSO Unique Identifier of (AAVSO UID) 000-BMZ-492.
Citation: Research in Astronomy and Astrophysics
PubDate: 2020-11-25T00:00:00Z
DOI: 10.1088/1674-4527/20/11/177
Issue No: Vol. 20, No. 11 (2020)
- Statistical properties of radio flux densities of solar flares
- Authors: Lu Wang; Si-Ming Liu Zong-Jun Ning
First page: 178
Abstract: Short timescale flux variations are closely related to the energy release process of magnetic
reconnection during solar flares. Radio light curves at 1, 2, 3.75, 9.4, and 17 GHz of 209 flares
observed by the Nobeyama Radio Polarimeter from 2000 to 2010 are analyzed with a running smooth
technique. We find that the impulsive component (with a variation timescale shorter than 1 s) of 1
GHz emission of most flares peaks at a few tens of solar flux unit and lasts for about 1 minute and
the impulsive component of 2 GHz emission lasts a shorter period and peaks at a lower flux level,
while at the three high frequency channels the occurrence frequency of flares increases with the
decrease of the flux density up to the noise level of the corresponding background. However, the
gradual components of these emissions have similar duration and peak flux density distributions. We
also derive the power spectrum on different timescales and a normalized wavelet analysis is used to
confirm featur...
Citation: Research in Astronomy and Astrophysics
PubDate: 2020-11-25T00:00:00Z
DOI: 10.1088/1674-4527/20/11/178
Issue No: Vol. 20, No. 11 (2020)
- The first photometric investigation of the contact binary OQ Cam
- Authors: Ya-Ni Guo; Kai Li, Qi-Qi Xia, Xing Gao, Lin-Qiao Jiang Yuan Liu
First page: 179
Abstract: The first charge-coupled device photometric light curves in B , V , R c , and I c bands of the
short-period contact binary star OQ Cam are presented. Through analyzing the light curves with the
Wilson-Devinney code, it is found that OQ Cam is a W-type shallow contact binary star with a contact
degree of f = 20.2%. Based on the O – C analyzing, the orbit period displays a long term increasing
with a rate of dP / dt = 4.40 × 10 −7 d yr −1 . The increasing in orbit period can be interpreted by
mass transfer from the less massive component to the more massive one. As the orbit period
increases, OQ Cam would evolve from the present shallow contact configuration to a non-contact
stage. So it may be a potential candidate to confirm the thermal relaxation oscillation theory.
Citation: Research in Astronomy and Astrophysics
PubDate: 2020-11-25T00:00:00Z
DOI: 10.1088/1674-4527/20/11/179
Issue No: Vol. 20, No. 11 (2020)
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