Astronomy Science and Technology Research Laboratory

Guangzhou, China

Astronomy Science and Technology Research Laboratory

Guangzhou, China
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Dou L.,Guangzhou University | Dou L.,Astronomy Science and Technology Research Laboratory | Wang T.,Anhui University of Science and Technology | Yan L.,California Institute of Technology | And 5 more authors.
Astrophysical Journal Letters | Year: 2017

We present the mid-infrared (MIR) light curves (LCs) of a tidal disruption event candidate in the center of a nearby ultraluminous infrared galaxy F01004-2237 using archival WISE and NEOWISE data from 2010 to 2016. At the peak of the optical flare, F01004-2237 was IR quiescent. About three years later, its MIR fluxes have shown a steady increase, rising by 1.34 and 1.04 mag in 3.4 and 4.6 μm up to the end of 2016. The host-subtracted MIR peak luminosity is 2-3 ×1044 erg s-1. We interpret the MIR LCs as an infrared echo, i.e., dust reprocessed emission of the optical flare. Fitting the MIR LCs using our dust model, we infer a dust torus of the size of a few parsecs at some inclined angle. The derived dust temperatures range from 590-850 K, and the warm dust mass is ∼7 M o. Such a large mass implies that the dust cannot be newly formed. We also derive the UV luminosity of 4-11 ×1044 erg s-1. The inferred total IR energy is 1-2 ×1052 erg, suggesting a large dust covering factor. Finally, our dust model suggests that the long tail of the optical flare could be due to dust scattering. © 2017. The American Astronomical Society. All rights reserved..


Lin C.,Guangzhou University | Lin C.,Astronomy Science and Technology Research Laboratory | Fan J.-H.,Guangzhou University | Fan J.-H.,Astronomy Science and Technology Research Laboratory | And 2 more authors.
Research in Astronomy and Astrophysics | Year: 2017

The beaming effect is important for understanding the observational properties of blazars. In this work, we collect 91 Fermi blazars with available radio Doppler factors. γ-ray Doppler factors are estimated and compared with radio Doppler factors for some sources. The intrinsic (de-beamed) γ-ray flux density (fγin), intrinsic γ-ray luminosity (Lγin) and intrinsic synchrotron peak frequency (Vin p) are calculated. Then we study the correlations between and redshift and find that they follow the theoretical relation:log f = -2.0 log z + const. When the subclasses are considered, we find that stationary jets are perhaps dominant in low synchrotron peaked blazars. Sixty-three Fermi blazars with both available short variability time scales (ΔT) and Doppler factors are also collected. We find that the intrinsic relationship between Linγ ΔTin and obeys the Elliot & Shapiro and Abramowicz & Nobili relations. Strong positive correlation between(fγin) and Vin P is found, suggesting that synchrotron emissions are highly correlated with γ-ray emissions. © 2017 National Astronomical Observatories, CAS and IOP Publishing Ltd.


Xiong D.,Chinese Academy of Sciences | Bai J.,Chinese Academy of Sciences | Zhang H.,Yunnan Normal University | Fan J.,Guangzhou University | And 4 more authors.
Astrophysical Journal, Supplement Series | Year: 2017

We have monitored the quasar 3C 273 in the optical V, R, and I bands from 2005 to 2016. Intraday variability (IDV) is detected on seven nights. The variability amplitudes on most of the nights are less than 10%, and on four nights, more than 20%. When considering the nights with time spans >4 hr, the duty cycle (DC) is 14.17%. Over the 12 years, the overall magnitude and color index variabilities are , , , and , respectively. The largest clear IDV has an amplitude of 42% over just 5.8 minutes, and the weakest detected IDV is 5.4% over 175 minutes. The BWB (bluer when brighter) chromatic trend is dominant for 3C 273 and appears at different flux levels on intraday timescales. The BWB trend exists for short-term timescales and intermediate-term timescales but different timescales have different correlations. There is no BWB trend for our whole time-series data sets. A significant anticorrelation between the BWB trend and length of timescales is found. Combining with V-band data from previous works, we find a possible quasi-periodicity of =3918 ±1112 days. The possible explanations for the observed variability, BWB chromatic trend, and periodicity are discussed. © 2017. The American Astronomical Society. All rights reserved..


Fan J.H.,Guangzhou University | Fan J.H.,Astronomy Science and Technology Research Laboratory | Kurtanidze O.,Abastumani Observatory | Kurtanidze O.,Kazan Federal University | And 6 more authors.
Astrophysical Journal, Supplement Series | Year: 2014

Variability is one of the most observable characteristics of active galactic nuclei, and it is important when considering the emission mechanism. In this paper, we report optical photometry monitoring of two nearby brightest quasars, PHL 1811 and 3C 273, using the ST-6 camera attached to the Newtonian focus and the Ap6E CCD camera attached to the primary focus of the 70 cm meniscus telescope at the Abastumani Observatory, Georgia. PHL 1811 was monitored during the period from 2002 September to 2012 December, while 3C 273 was monitored during the period from 1998 February to 2008 May. During our monitoring period, the two sources did not show any significant intra-day variability. The largest detected variations are ΔR = 0.112 ± 0.010 mag. for PHL 1811, ΔB = 0.595 ± 0.099 mag, ΔV = 0.369 ± 0.028 mag, ΔR = 0.495 ± 0.076 mag, and ΔI = 0.355 ± 0.009 mag for 3C 273. When the periodicity analysis methods are adopted for the observations of the sources, a period of p = 5.80 ± 1.12 yr is obtained for PHL 1811 in the R light curve in the present work, and periods of p = 21.10 ± 0.14, 10.00 ± 0.14, 7.30 ± 0.09, 13.20 ± 0.09, 2.10 ± 0.06, and 0.68 ± 0.05 yr are obtained for 3C 273 based on the data in the present work combined with historical works. © 2014. The American Astronomical Society. All rights reserved..


Yang J.,University of Science and Arts of Iran | Yang J.,Guangzhou University | Fan J.,Guangzhou University | Fan J.,Astronomy Science and Technology Research Laboratory | And 2 more authors.
Science China: Physics, Mechanics and Astronomy | Year: 2012

In this paper, a sample including 68 blazars (18 BL Lacs and 50 FSRQs) with known Doppler factors and superluminal velocity from our previous papers is presented. Both the Lorentz factors (Γ) and viewing angles (θ) are estimated for the 68 sources. The relationship between BL Lacs and FSRQs is also revisited using the two variables of Γ and θ. The Lorenz factors are in the range of 2.33 to 64.07. The viewing angles are in the range of 0.04 to 24.56. The averaged value of the viewing angle for BL Lacs is slightly larger than that for FSRQs, while the averaged value of the Lorentz factor for BL Lacs is smaller than that for FSRQs. © Science China Press and Springer-Verlag Berlin Heidelberg 2012.


Fan J.-H.,Guangzhou University | Fan J.-H.,Astronomy Science and Technology Research Laboratory | Yang J.-H.,University of Science and Arts of Iran | Liu Y.,Guangzhou University | And 3 more authors.
Research in Astronomy and Astrophysics | Year: 2013

Observations suggest that γ-ray loud blazars are strongly beamed. The Fermi mission has detected many of blazars, which provide us with a good opportunity to investigate the emission mechanism and the beaming effect in the γ-ray region. We compiled the X-ray observations for 138 Fermi blazars (54 flat spectrum radio quasars, 36 low-peaked BL Lacertae objects, and 48 high-peaked BL Lacertae objects) and calculated their Doppler factors, δγ. It is interesting that the calculated Doppler factors, δγ, are strongly correlated with the γ-ray luminosity. © 2013 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd.


Yuan Y.,Guangzhou University | Yuan Y.,Astronomy Science and Technology Research Laboratory | Yuan Y.,Hefei University of Technology
Science China: Physics, Mechanics and Astronomy | Year: 2012

Based on the new data from the database of the University of Michigan Radio Astronomy Observatory (UMRAO), we analyze the spectral index and optical variability of OJ287 and 3C279. The main results show that 1) the time delay among three radio bands (4.8, 8, and 14.5 GHz) shows: τ 8-14.5 = 31 d, τ 4-8.8 = 41 d for OJ287, but no time delay lying in 3C279; 2) strong correlation lies in the polarization and flux density at 8 GHz for OJ287 and at 8, 14.5 GHz for 3C279; 3) the logarithmic brightness temperature log(T B) = 14.1 K for OJ287 is 14.1 K, log(T B) = 15.1 K for 3C279. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.


Fan J.H.,Guangzhou University | Fan J.H.,Astronomy Science and Technology Research Laboratory
Journal of Astrophysics and Astronomy | Year: 2014

In this paper, we describe what we have done with regard to astronomy training for physics students. More and more students are interested in astronomy, they spend their summer holidays and spare time in observations and studying the observation data. Some students are familiar with using the telescope for observations, dealing with absorption line features achieved from the observations. Astronomy was selected as the key subject in Guangzhou city and Guangdong province, the laboratory for astronomy science and technology was selected as the key laboratory of Guangzhou city and that for the education department of Guangdong Province. We also provide a master degree programme for astronomy. © 2014, Indian Academy of Sciences.


Lin C.,Guangzhou University | Fan J.-H.,Astronomy Science and Technology Research Laboratory
Research in Astronomy and Astrophysics | Year: 2016

BL Lacertae objects (BL Lacs) are the dominant population of TeV emitting blazars. In this work, we investigate whether there are any special observational properties associated with TeV sources. To do so, we will compare the observational properties of TeV detected BL Lacs (TeV BLs) with non-TeV detected BL Lac objects (non-TeV BLs). From the 3rd Fermi/LAT source catalog (3FGL), we can obtain 662 BL Lacs, out of which 47 are TeV BLs and 615 are non-TeV BLs. Their multi-wavelength flux densities (F R, F O, F X and F γ), photon spectral indexes (αX ph and αph γ), and effective spectral indexes (αRO and αOX) are compiled from the available literature. Then the luminosities (log vL R, log vL O, log vL X, log vL γ) are calculated. From comparisons, we find that TeV BLs are different from low synchrotron peaked BLs and intermediate synchrotron peaked BLs, but TeV BLs show similar properties to high synchrotron peaked (HSP) BLs. Therefore, we concentrated on a comparison between TeV HSP BLs and non-TeV HSP BLs. Analysis results suggest that TeV HSP BLs and non-TeV HSP BLs exhibit some differences in their αRO and αγ ph, but their other properties are quite similar. © 2016 National Astronomical Observatories, Chinese Academy of Sciences and IOP Publishing Ltd.


Yuan Y.H.,Guangzhou University | Yuan Y.H.,Astronomy Science and Technology Research Laboratory | Fan J.H.,Guangzhou University | Fan J.H.,Astronomy Science and Technology Research Laboratory | Pan H.J.,Chinese Academy of Sciences
Astronomical Journal | Year: 2015

Using the 1.56 m telescope at Shanghai Observatory, China, we present the photometric results of 1ES 1959+650, which cover from 2006 June 11 to 2014 July 31. The maximum variabilities are DmV max = 1.74 ±0.02 ± mag in the V band, ΔmR max = 0.97 ±0.02 ± mag in the R band, and ΔmI max = 1.15 ±0.03 ± mag in the I band. During the monitoring period, we obtain intraday variabilities on 2009 September 2 (JD 2455077) and 2009 September 3 (JD 2455078). On 2009 September 2, the intraday variabilities are ΔmV = 0.36 ±0.08 mag within 1.56 hr, ΔmR= 0.21 ±0.04 mag within 23 minutes, and ΔmI = 0.53 ±0.03mag within 45 minutes. On 2009 September 3, the intraday variabilities are ΔmV = 0.40 ±0.10 mag within 27 minutes, ΔmR = 0.48 ±0.04 mag within 3.24 hr, and ΔmI = 0.68 ±0.06 mag within 3.72 hr. The two intraday variabilities occur in 24 hr, which may occur in the same variable phase. Other results show that (1) no quasi-periodicity is found in the longterm light curve and (2) the correlations between the brightness and the spectrum show obvious anti-correlation, a = -(0.18 ±0.02)FV + (2.33 ±0.12), with the correlation coefficient r = -0.74 and the chance probability p >0.01%. © 2015. The American Astronomical Society. All rights reserved.

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