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The Burst Optical Observer and Transient Exploring System (BOOTES) is a world-wide automatic telescope network which aims to repaid follow-up of transient and astrophysical sources in the sky for which the first station was installed in 1998. With the advent in 2015 of the LIGO/Virgo interferometers, as part of the new generation of detectors designed for the detection of the signal of gravitational waves, a new window to explore the Universe has been opened. Here we present the status of the BOOTES network, the related strategies regarding the follow-up of gravitational wave events and the developments in the Gravitational Wave Era. Some preliminary results regarding the BOOTES follow-up observations are presented.

The Lijiang 2.4 m Telescope (LJT) is one of the most important telescopes for general astronomical observations in China. Yunnan Faint Object Spectrograph and Camera (YFOSC) is a widely used instrument mounted on the LJT, which occupies for ∼80% of the observing time of the LJT, and thus instrument health and data quality of the YFOSC are very important for both the telescope maintenance team and users of the LJT. So we develop an automated data analysis system for the quality control (QC) of YFOSC data. This system is also a new function of the observing support of the YFOSC. Based on the system, YFOSC data can be reduced quickly as they are acquired and QC parameters are extracted. Observers can assess the quality of their data and make a possible revision of their observing plan in time. These parameters can also be used to check the health of the YFOSC, which is helpful for the telescope maintenance team to find potential problems. All of these aim at improving the productivity of the LJT.

Polarimetry plays an important role in investigating physical properties for celestial objects. We present a polarimeter named YFPOL for the Cassegrain focus of the Lijiang 2.4 m Telescope (LJT) of Yunnan Observatories, Chinese Academy of Sciences. YFPOL is a traditional single-beam polarimeter with a rotating polarizer. As the focal-reducer instrument Yunnan Faint Object Spectrograph and Camera (YFOSC) is always positioned on the Cassegrain focal plane of LJT, we develop two sets of ultra-thin (thickness 7 ′ field of view, and the systematic uncertainty is below 0.8% for a V = 11.68 target with a 10 s exposure. The instrument polarization angle offset is 2.°6. YFPOL is not only a simple polarimeter, but also a spectropolarimeter with grisms that can be considered in the future.

In order to study the physical properties of the γ-ray emitting narrow-line Seyfert 1 (NLS1) galaxy population, photometric and spectral observations of the γ-ray emitting NLS1 PMN J0948+0022 were made with the Lijiang 2.4 m optical telescope of Yunnan Observatories, Chinese Academy of Sciences. Photometric data in the B and R bands were collected for 50 nights from 2020 January to 2021 December. During the observation epoch, the variability amplitudes are 73.67% in the B band and 79.96% in the R band. Intra-day variability is found in two observation nights, and the duty cycle value is 29% with variability amplitude > 12.9% in the R band, which support the presence of the relativistic jets in the target. The redder-when-brighter (RWB) chromatic trend (or steeper-when-brighter trend) appears on intra-day and long timescales. The RWB trend is dominated by the radiation of accretion disk and jet, and resembles those in flat spectrum radio quasars. When PMN J0948+0022 is brighter than 17.ͫ5 in the R band, there is no color change trend. By analyzing the spectral data of PMN J0948+0022, we obtained the black hole mass of M • = 1.61 × 107 M ⊙ and accretion rate of M ̇ = 93 , and confirmed that PMN J0948+0022 is a super-Eddington accreting NLS1. The redshifts of reverberation mapped super-Eddington accreting active galactic nuclei can be expanded by PMN J0948+0022 up to above 0.5. Super-Eddington accreting NLS1 galaxies were chosen as a new type of cosmological candle in the literature. PMN J0948+0022 may be used as a target for the next step of reverberation mapping monitoring project of super-Eddington accreting massive black holes.

Observing a telluric standard star for correcting the telluric absorption lines of spectrum will take a significant amount of precious telescope time, especially in the long-term spectral monitoring project. Beyond that, it's difficult to select a suitable telluric standard star near in both time and airmass to the scientific object. In this paper, we present a method of correcting the telluric absorption lines by combining the advantages of long slit spectroscopy. By rotating the slit, we observed the scientific object and a nearby comparison star in one exposure, so that the spectra of both objects should have the same telluric transmission spectrum. The telluric transmission spectrum was constructed by dividing the observed spectrum of comparison star by its stellar template, and was used to correct the telluric absorption lines of the scientific object. Using the long slit spectrograph of Lijiang 2.4-meter telescope, we designed a long-term spectroscopic observation strategy, and finished a four-year spectroscopic monitoring for a pair of objects (an active galactic nuclei and an non-varying comparison star). We applied this method to correct the telluric absorption lines of the long-term monitored spectra by Lijiang 2.4-meter telescope, and investigated the variation of the telluric absorptions at Lijiang Observatory. We found that the telluric absorption transparency is mainly modulated by the seasonal variability of the relative humidity, airmass and seeing. Using the scatter of the [O~III] $\lambda$5007 fluxes emitted from the narrow-line region of active galactic nuclei as an indicator, we found that the correction accuracy of the telluric absorption lines is 1%., Comment: 15 pages, 10 figure, accepted for publication in RAA (Research in Astronomy and Astrophysics)

Full list of authors: Gupta, Rahul; Oates, S. R.; Pandey, S. B.; Castro-Tirado, A. J.; Joshi, Jagdish C.; Hu, Y. -D; Valeev, A. F.; Zhang, B. B.; Zhang, Z.; Kumar, Amit; Aryan, A.; Lien, A ; Kumar, B.; Cui, Ch; Wang, Ch; Dimple; Bhattacharya, D.; Sonbas, E.; Bai, J.; Tello, J. C.; Gorosabel, J.; Castro Ceron, J. M.; Porto, J. R. F.; Misra, K.; De Pasquale, M.; Caballero-Garcia, M. D.; Jelinek, M.; Kubanek, P.; Minaev, P.; Cunniffe, R.; Sanchez-Ramirez, R.; Guziy, S.; Jeong, S.; Tiwari, S. N.; Razzaque, S.; Bhalerao, V.; Pintado, V. C.; Sokolov, V. V.; Zhao, X.; Fan, Y.; Xin, Y.

We present the results from a spectroscopic monitoring campaign to obtain reverberation-mapping measurements and investigate the broad-line region kinematics for active galactic nuclei (AGN) of Mrk~817 and NGC~7469. This campaign was undertaken with the Lijiang 2.4-meter telescope, the median spectroscopic sampling is 2.0 days for Mrk~817 and 1.0 days for NGC~7469. We detect time lags of the broad emission lines including H$\beta$, H$\gamma$, He~{\sc ii} and He~{\sc i} for both AGNs, and including Fe~{\sc ii} for Mrk~817 with respect to the varying AGN continuum at 5100~\AA. Investigating the relationship between line widths and time lags of the broad emission lines, we find that the BLR dynamics of Mrk~817 and NGC~7469 are consistent with the virial prediction. We estimate the masses of central supermassive black hole (SMBH) and the accretion rates of both AGNs. Using the data of this campaign, we construct the velocity-resolved lag profiles of the broad H$\gamma$, H$\beta$, and He~{\sc i} lines for Mrk~817, which show almost the same kinematic signatures that the time lags in the red wing are slightly larger than the time lags in the blue wing. For NGC~7469, we only clearly construct the velocity-resolved lag profiles of the broad H$\gamma$ and H$\beta$, which show very similar kinematic signatures to the BLR of Mrk~817. These signatures indicate that the BLR of Keplerian motion in both AGNs seemingly has outflowing components during the monitoring period. We discuss the kinematics of the BLR and the measurements including SMBH mass and accretion rates., Comment: 19 pages, 11 figures, accepted for publication in ApJ

In this paper, we report the new results of spectroscopic observations of $\gamma$-ray blazar S5 0716+714 from 2019 September to 2020 March with the 2.4 m optical telescope at Lijiang Observatory of Yunnan Observatories. The median cadence of observations is $\sim$ 1 day. During the second observation period (Epoch2), the observational data reveal an extremely bright state and a bluer-when-brighter (BWB) chromatism. The BWB trend of Epoch2 differs significantly from that of the first observation period (Epoch1). A significantly brightness-dependent BWB chromatism emerges in the total data of Epoch1 and Epoch2. The BWB trend becomes weaker towards the brighter states, and likely becomes saturated at the highest state. Based on a log-parabolic function, a power-law of synchrotron peak flux and frequency $\nu_{\rm{p}}$, and a power-law of the curvature of synchrotron spectrum and its $\nu_{\rm{p}}$, simulation well reproduces the brightness-dependent BWB trend of S5 0716+714. The BWB trend is seemingly controlled by the shift of $\nu_{\rm{p}}$ with respect to the observational window, and effectively may be dominated by the variations of electron average energy and magnetic field in emitting region., Comment: 16 pages, 5 figures, Accepted for publication in ApJ