Correcting the Contamination of Second-order Spectra:Improving HαMeasurements in Reverberation Mapping Campaigns

Long-term spectroscopic monitoring campaigns on active galactic nuclei(AGNs)provide a wealth of information about its interior structure and kinematics.However,a number of the observations suffer from the contamination of second-order spectra(SOS)which will introduce some undesirable uncertainties at the red side of the spectra.In this paper,we test the effect of SOS and propose a method to correct it in the time domain spectroscopic data using the simultaneously observed comparison stars.Based on the reverberation mapping(RM)data of NGC 5548 in2019,one of the most intensively monitored AGNs by the Lijiang 2.4 m telescope,we find that the scientific object,comparison star,and spectrophotometric standard star can jointly introduce up to~30%SOS for Grism 14.This irregular but smooth SOS significantly affects the flux density and profile of the emission line,while having little effect on the light curve.After applying our method to each spectrum,we find that the SOS can be corrected effectively.The deviation between corrected and intrinsic spectra is~2%,and the impact of SOS on time lag is very minor.This method makes it possible to obtain the HαRM measurements from archival data provided that the spectral shape of the AGN under investigation does not have a large change.

Quality Control of YFOSC Data I. The On-site Quick Analysis System

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.

Rapid instrument exchanging system for the Cassegrain focus of the Lijiang 2.4-m Telescope

As a facility used for astronomical research, the Lijiang 2.4-m telescope of Yunnan Astronomical Observatories, requires the ability to change one auxiliary instrument with another in as short a time as possible. This arises from the need to quickly respond to scientific programs(e.g. transient observation, time domain studies) and changes in observation conditions(e.g. seeing and weather conditions). In this paper, we describe the design, construction and test of hardware and software in the rapid instrument exchange system(RIES) for the Cassegrain focal station of this telescope, which enables instruments to be quickly changed at night without much loss of observing time. Tests in the laboratory and at the telescope show that the image quality and pointing accuracy of RIES are satisfactory.With RIES, we observed the same Landolt standard stars almost at the same time with the Princeton Instruments VersA rray 1300 B Camera(PICCD) and the Yunnan Faint Object Spectrograph and Camera(YFOSC), while both were mounted at the Cassegrain focus. A quasi-simultaneous comparison shows that the image quality of the optical system inside the YFOSC is comparable with that provided by the PICCD.

Statistical Properties of a Blazar Sample and Comparison of HBLs, LBLs and FSRQs

Making use of the 2MASS Data Release, we have searched for nearinfrared (JHK) counterparts to 268 blazars from Donato et al. and obtained 238counterparts within 5' in the area covered by 2MASS. It provides us a sample with infrared data several times larger than the previous one of the same kind.Based on our sample and the sample by Donato et al., we have compared in detail the properties of HBLs, LBLs and FSRQs from five aspects and found that HBLs are significantly different from LBLs and FSRQs while LBLs are not obviously different from FSRQs. Our results strongly support the division of BL Lac objects into the high-frequency peaked (HBL) and low-frequency peaked (LBL) objects introduced by Padovani & Giommi and show that HBLs and LBLs are two kinds of blazar having different physical properties.

Lijiang 2.4-meter Telescope and its instruments

The Lijiang 2.4-meter Telescope(LJT), the largest common-purpose optical telescope in China,has been available to the worldwide astronomical community since 2008. It is located at the Gaomeigu site,Lijiang Observatory(LJO), in the southwest of China. The site has very good observational conditions.During its 10-year operation, several instruments have been equipped on the LJT. Astronomers can perform both photometric and spectral observations. The main scientific goals of LJT include recording photometric and spectral evolution of supernovae, reverberation mapping of active galactic nuclei, investigating the physical properties of binary stars and near-earth objects(comets and asteroids), and identification of exoplanets and all kinds of transients. Until now, the masses of 41 high accretion rate black holes have been measured, and more than 168 supernovae have been identified by the LJT. More than 190 papers related to the LJT have been published. In this paper, the general observation conditions of the Gaomeigu site is introduced at first. Then, the structure of the LJT is described in detail, including the optical, mechanical, motion and control system. The specification of all the instruments and some detailed parameters of the YFOSC is also presented. Finally, some important scientific results and future expectations are summarized.

经尿道HoLEP对患者勃起功能的影响

目的探讨保留精阜近端尿道黏膜在经尿道前列腺钬激光剜除术(HoLEP)中对患者勃起功能的影响。方法将2016年6月—2017年6月于江苏省盐城市第一人民医院收治的50例前列腺增生(BPH)患者随机分为两组,分别采用传统HoLEP和改良的HoLEP。检测其手术前后勃起功能的变化。结果两组患者术后勃起功能障碍(ED)发生率比较,差异有统计学意义(P<0.05)。结论改良的保留精阜近端尿道粘膜的HoLEP能够降低患者术后的ED发生率。

Astronomical Site Monitoring System at Lijiang Observatory

We installed two sets of Astronomical Site Monitoring Systems(ASMSs)at Lijiang Observatory(GMG),for the running of the 2.4-meter Lijiang optical telescope(LJT)and the 1.6-meter Multi-channel Photometric Survey Telescope(Mephisto).The Mephisto is under construction.The ASMS has been running on robotic mode since 2017.The core instruments:Cloud Sensor,All-Sky Camera and AutonomousDIMM that are developed by our group,together with the commercial Meteorological Station and Sky Quality Meter,are combined into the astronomical optical site monitoring system.The new Cloud Sensor's Cloud-Clear Relationship is presented for the first time,which is used to calculate the All-Sky cloud cover.We designed the Autonomous-DIMM located on a tower,with the same height as LJT.The seeing data have been observed for a full year.ASMS's data for the year 2019 are also analysed in detail,which are valuable to observers.

Possible γ-ray emission of radio intermediate AGN Ⅲ Zw 2 and its implication on the evolution of jets in AGNs

AGNs with hard γ-ray emission identified so far are radio-loud.III Zw 2 is a radio intermediate AGN with a relativistic jet.We study its spectral energy distribution (SED) and find that the broad band emissions are dominated by the non-thermal emissions from the jet.We model its SED through a synchrotron + inverse Compton (IC) model.The results show that the IC component of III Zw 2 peaks at a few MeV, and the flux density drops rapidly at higher energy with photon index Γ≈3.3 above 0.1GeV.The predicted flux is slightly over the sensitivity of Fermi/LAT, but it was not included in the first Fermi/LAT AGN catalog.The reason for this may be:1) that the IC peak is low and the spectrum is very steep above 0.1 GeV, 2) that III Zw 2 is in the low state during the period of the Fermi/LAT operation.We also find that III Zw 2 follows similar jet processes as those in γ-ray AGNs, e.g., the relation between jet power and radiation power, which is called the blazar sequence.We suggest that III Zw 2 may be a young source at an earlier stage of jet activity.

What determines the observational differences of blazars？

We examine the scenario that the Doppler factor determines the observational differences of blazars. Significantly negative correlations are found between the observational synchrotron peak frequency and the Doppler factor. After correcting the Doppler boosting, the intrinsic peak frequency has a tight linear relation with the Doppler factor. It is interesting that this relation is consistent with the scenario that the black hole mass governs both the bulk Lorentz factor and the synchrotron peak frequency. In addition, the distinction between the kinetic jet powers of BL Lac objects and flat spectrum radio quasars disappears after the boosting factor δ~2 is considered. The negative correlation between the peak frequency and the observational isotropic luminosity, known as the blazar sequence, also disappears after the Doppler boosting is corrected. We also find that the correlation between the Compton dominance and the Doppler factor exists for all types of blazars. Therefore, this correlation is unsuitable for examining the external Compton emission dominance.

A correction method for the telluric absorptions and application to Lijiang Observatory

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 is 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 the 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 the 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 nucleus and a non-varying comparison star).We applied this method to correct the telluric absorption lines of the long-term monitored spectra by the 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] λ5007 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%.

An explanation for 13 consecutive day activities of Mrk 421

It is surprising to find an instance of migration in the peak positions of synchrotron spectral energy distribution components during the activity epochs of Markarian 421(Mrk 421),accompanying an orphan flare at the X-ray and GeV-TeVγ-ray bands.A geometric interpretation and standard shock or stochastic acceleration models of blazar emission have difficulty reproducing these observed behaviors.The present paper introduces a linear acceleration by integrating the reconnection electric field into the particle transport model for the observed behaviors of Mrk 421.We note that strong evidence for evolution in characteristic of multi-wavelength spectral energy distribution including shifting the peak frequency,accompanying an orphan flare at the X-ray and GeV-TeVγ-ray bands provides an important electrostatic acceleration diagnostic in a blazar jet.Assuming suitable model parameters,we apply the results of the simulation to the 13-day flaring event in March 2010 of Mrk 421,concentrating on the evolution of multiwavelength spectral energy distribution characteristic by shifting the peak frequency.It is clear that the ratio of the electric field and magnetic field strength plays an important role in temporal evolution of the peak frequency of synchrotron spectral energy distribution component.We suggest it is reasonable that the electrostatic acceleration is responsible for the evolution of multi-wavelength spectral energy distribution characteristic by shifting the peak frequency.Based on the model results,we assert that the peak frequency of the synchrotron spectral energy distribution component may signify a temporary characteristic of blazars,rather than a permanent one.

Optical multi-color monitoring of OJ 287 from 2006 to 2012

We present our optical multi-color monitoring of the BL Lac object OJ 287 from January 2006to December 2012 in the V,R and I bands.A relatively active state in OJ 287 has been found over all monitored epochs,among which the variations of average magnitude in V/R/I bands were measured with ?V=1.956 mag,?R=2.067 mag and ?I=2.115 mag,respectively.No reliable intraday variability is detected,but possible variability is detected on 16 nights.Their relative variation amplitudes fall into the range between 1% and 8%,with the majority between 2% and 4%.No time lags have been detected,but strong correlations exist among light curves in the three wavebands.The bluer-when-brighter trend is dominant over intraday timescales,which supports the shock-in-jet model.When combining with additional V/R band data obtained from SMARTS and the Steward Observatory,we also find a bluer-when-brighter trend over a long-term timescale.Some possible periods of 513,176,36,30,26,17 and 14 d are found in all time-series data sets from 2006 to 2017.Possible explanations about these periods are given.

The photometric monitoring of γ-ray-loud narrow-line Seyfert 1 galaxy 1H0323+342 from 2006 to 2010

1H 0323+342 is a γ-ray-loud narrow-line Seyfert 1 galaxy(NLS1). The variability mechanism of γ-ray-loud NLS1 s remains unclear. We have observed 1H 0323+342 photometrically from 2006 to2010 with a total of 41 nights of observations in order to constrain the variability mechanism. Intraday variabilities(IDVs) are detected on four nights. When considering the nights with time spans > 2 hours,the duty cycle is 28.3%. The average variability amplitude is 10.8% for IDVs and possibly variable nights. In the color-magnitude diagram, there are bluer-when-brighter chromatic trends for intraday and long-term timescales, which could be explained by the shock-in-jet model, and also could possibly be due to two distinct components or an accretion disk model.

Kinematic properties of the dual AGN system J0038+4128 based on long-slit spectroscopy

The study of kiloparsec-scale dual active galactic nuclei(AGN) provides important clues for understanding the co-evolution between host galaxies and their central supermassive black holes undergoing a merging process. We present long-slit spectroscopy of J0038+4128, a kiloparsec-scale dual AGN candidate,discovered recently by Huang et al., using the Yunnan Faint Object Spectrograph and Camera(YFOSC)mounted on the Lijiang 2.4-m telescope administered by Yunnan Observatories. From the long-slit spectra, we find that the average relative line-of-sight(LOS) velocity between the two nuclei(J0038+4128N and J0038+4128S) is about 150 km s^(-1). The LOS velocities of the emission lines from the gas ionized by the nuclei activities and of the absorption lines from stars governed by the host galaxies for different regions of J0038+4128 exhibit the same trend. The same trend in velocities indicates that the gaseous disks are co-rotating with the stellar disks in this ongoing merging system. We also find several knots/giant H_Ⅱ regions scattered around the two nuclei with strong star formation revealed by the observed line ratios from the spectra. Those regions are also clearly detected in images from HST F 336W/U-band and HST F 555W/V-band.

Is BZB J1450+5201 the most distant gamma-ray BL Lacertae object?

BL Lacertae(BL Lac) objects at high redshifts(z ≥ 2) are rarely detected.Through careful analysis of its Sloan Digital Sky Survey spectrum, BZB J1450+5201is confirmed to be a high-z BL Lac object with z ≥ 2.471 by identifying the Lyα 1216 and CIV 1548/1550 absorption lines. This indicates that BZB J1450+5201 is the most distant BL Lac object discovered to date. Careful analysis of the five-year Fermi-LAT data of 2FGL J1451.0+5159 shows that its γ-ray emission is robust with a confidence level of 6.2σ at 1–3 Ge V and 6.7σ at 3–10 Ge V. This analysis with the five-year data overcomes confusion with its bright neighbor, which is a problem when analyzing the two-year data. In addition, 2FGL J1451.0+5159 is confirmed to be associated with BZB J1450+5201 using the five-year data. The analysis of multiwavelength data, from radio to γ-ray energies, indicates that BZB J1450+5201 is an intermediate synchrotron peaked(ISP) source. Its multiwavelength properties are consistent with distributions of other ISP sources at lower redshifts in the second Fermi-LAT AGN catalog. The pure synchrotron self-Compton(SSC) model seems to be disfavored, but the scattering of weak external emission plus the SSC process can provide a satisfactory description of the broadband emission.

The connection between radio and γ-ray emission in Fermi/LAT blazars

We collect the second Large Area Telescope AGN catalog (2LAC) and Monitor of Jets in AGN with VLBA Equipment (MOJAVE) quasi-simultaneous data to investigate the radio-γ connection of blazars. The cross sample contains 166 sources. The statistical analysis based on this sample confirms positive correlations between these two bands, but the correlations become weaker as the γ-ray energy increases. The statistical results between various parameters show negative correlations of γ-ray photon spectral index with γ-ray loudness for both Flat Spectrum Radio Quasars (FSRQs) and BL Lacertae objects, positive correlations of γ-ray variability index with the γ-ray loudness for FSRQs, a negative correlation of the γ-ray variability index with the γ-ray photon spectral index for FSRQs, and negative correlations of γ-ray photon spectral index with γ-ray luminosity for FSRQs. These results suggest that the γ-ray variability may be due to changes inside the γ-ray emission region like the injected power, rather than changes in the photon density of the external radiation fields, and the variability amplitude tends to be larger as the γ-rays are closer to the high energy peak of the spectral energy distribution (SED). No correlation of variability index found for BL Lacertae objects implies that variability behavior may differ below and above the peak energy.

R-band host galaxy contamination of TeV γ-ray blazar Mrk 501： effects of aperture size and seeing

We simulated the R-band contribution of the host galaxy of TeV γ-ray BL Lac object Mrk 501 in different aperture sizes and seeing conditions. An intensive set of observations was acquired with the 1.02 m optical telescope, managed by Yunnan Observatories, from 2010 May 15 to 18. Based on the host subtraction data usually used in the literature, the subtraction of host galaxy contamination results in significant seeing-brightness correlations. These correlations would lead to illusive large amplitude variations at short timescales, which will mask the intrinsic microvariability, thus giving rise to difficulty in detecting the intrinsic microvariability. Both aperture size and seeing condition influence the flux measurements, but the aperture size impacts the result more significantly. Based on the parameters of an elliptical galaxy provided in the literature, we simulated the host contributions of Mrk 501 in different aperture sizes and seeing conditions. Our simulation data of the host galaxy obviously weaken these significant seeing-brightness correlations for the host-subtracted brightness of Mrk 501, and can help us discover the intrinsic short timescale microvariability. The pure nuclear flux is ~8.0 m Jy in the R band,i.e., the AGN has a magnitude of R ~13.96 mag.

YFPOL: A Linear Polarimeter of Lijiang 2.4 m Telescope

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 <12 mm) polarizer rotation control systems with wireless charging and control functions, which are suitable for mounting on the two front-wheels of YFOSC. One set is used as the polarimetric calibration unit, and the other is for the polarimetric modulation unit. Both of the polarizers have an ultra-high contrast ratio of 1,000,000:1 in the optical band. We investigate the instrumental polarization characteristics(IPCs) in the full field of view that is transferred from YFOSC. Furthermore, we identify that the IPCs change when the Cassegrain axis rotates. The spurious polarization from the IPCs can be effectively minimized by flat-fielding using the unpolarized domeflat, when the Cassegrain rotation angle is the same or nearest to that of the polarization observation. We develop a quasiautomatic pipeline for YFPOL and its effectiveness has been verified by tests of the polarimetric observation with blazar S5 0716+714. The calibration is performed by observing the zero-polarized and highly-polarized standard stars. We successfully reach high precision polarization in the 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.

Multicolor Optical Monitoring of the γ-Ray Emitting Narrow-line Seyfert 1 Galaxy PMN J0948+0022 from 2020 to 2021

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 Lijiang2.4 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.=1.61×10^(7) Mand 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.

Time Lags between the 22 and 37 GHz Bursts of 48 Radio-loud AGNs

从监视节目的 Metsahovi 在 22 和 37 GHz 基于轻曲线，我们调查时间为 48 收音机大声的 AGN 在二个收音机乐队之间落后。DCF 和 ZDCF 分析被用于数据。我们的结果证明在为所有来源的二收音机频率之间有强壮的关联，与在在一般来说带在 22 GHz 的 37 GHz 的轻曲线的变化。关于时间不同亚纲 AGN 之间没有明显的差别落后。在二来源，在更低的频率的爆炸在更高的频率带，这被发现。一可能的解释是电子加速统治轻曲线直到放射到达最大值。一些来源，例如 3C 273， 3C 279， 3C 345 并且 3C 454.3，有足够好的数据，我们能因此计算他们的 lags burst-by-burst。我们不同爆发举办的计算表演不同落后。一些爆炸有积极落后，大多数爆炸有不清楚落后，并且一些否定落后。这结果意味着不同爆炸被不同机制触发，并且为结果的解释包含两个一内在并且几何机制。积极落后与吃惊模型很好一致，并且我们使用这些落后计算放射的区域的典型磁场力量。