Telescope In China Research Articles

A Light Redback Companion of PSR J1622–0315 and Irradiation Power in Spider Systems

We report optical observations of the millisecond pulsar binary system PSR J1622–0315 with the Lulin 1 m telescope in Taiwan and the Lijiang 2.4 m telescope in China between 2019 and 2021. The companion of the pulsar, which is of V ∼ 19 mag, showed ellipsoidal-distorted orbital variations in its light curves. The best-fit model to the light curves, with the binary code PHOEBE, gives a companion mass of 0.122 ± 0.006 M ⊙. This places PSR J1622–0315 in the spider-system subclass. We compared the properties of PSR J1622–0315 with other spider pulsar binaries for the scalings between the spin-down luminosity derived for the pulsar, irradiation luminosity of the companion, and X-ray luminosity of the binary. We find that pulsar irradiation in PSR J1622–0315 is insignificant and the irradiation luminosity of the transitional millisecond pulsars PSR J1023+0038 and PSR J1227–4853 are the highest among the redback systems.

Spectroscopic and photometric studies on four solar-type short-period contact binaries in the triple stellar systems

ABSTRACT We reported new spectroscopy and photometry for four short-period binaries, which were acquired by several small telescopes in China from 2020 to 2022. From new spectrum and Large Sky Area Multiobject Fiber Spectroscopic Telescope data, we determined their spectral types of G8V for PZ UMa, G7 for MM Com, and V0685 Peg and G3 for V1055 Her. When compared to the Transiting Exoplanet Survey Satellite (TESS) light curve (LC) with a 2-min cadence, the difference between two light maxima for V1055 Her displays a 29.7-d oscillation. Utilizing the Wilson–Devinney program, we deduced 10 photometric solutions from our new and TESS data. Four binaries are W-type ones with variable O’Connell effects. For LC2022.1 (MM Com) and LC2022.9 (V1055 Her), Δmmax=Max.I–Max.II is as large as $15{{\ \rm per\ cent}}$ of variable light amplitude, which may be attributed to the spot’s migration and evolution. From the mass-luminosity diagram, the more massive components aref somewhat evolved main-sequence stars, whereas the less massive ones are overluminous as a result of energy exchange. Based on all eclipse timing residuals, the orbital period variations are preferably described by the light-travel time effects via the presence of additional companions. Their modulation periods range from 10 to 20 yr for four binaries, corresponding the companion’s mass ranging from M3 = 0.11 to 0.34 M⊙. Therefore, four solar-type short-period contact binaries (i.e. MM Com, PZ UMa, V0685 Peg, and V1055 Her) may be triple stellar systems.

Magnetic Activity on Four Short-period Contact Binaries: V0576 Peg, KW Psc, V0873 Per, and FY Boo

We presented new photometry for four short-period late-type binaries, observed by three small telescopes in China from 2020 September to 2021 December. Seven sets of light curves (including the TESS data for FY Boo) were analyzed by using the W-D method. Three binaries (V0576 Peg, V0873 Per, and FY Boo) are W-type binaries with q ≃ 2.5, while KW Psc is an A-type binary with q ≃ 0.43. Max.I−Max.II is up to 10% of variable light amplitude for the asymmetric light curves, which are modeled by a dark spot on the surface of the more massive component. Photometric results imply the existence of movement and evolution of the cool spot. From the temperature−luminosity and mass–luminosity diagrams, the more massive components are a bit evolved main-sequence stars, while the less massive ones are oversized and overluminous owing to energy exchange. Orbital period analyses indicate that the cyclic oscillations occur in the (O − C) curves. Their modulated periods approach 11 yr, which may preferably result from the magnetic activity cycle for four late-type contact binaries. With angular momentum loss through magnetic braking, these short-period contact binaries may evolve into deep-contact configurations.

The astrometric results of observations of fast-moving NEAs during close approach to the Earth

Current investigation is devoted to ongoing follow-up observations of fast-moving near-Earth asteroids (NEAs) carried out with Rotating-drift-scan CCD technique on small-aperture telescopes in China and Ukraine. The observations were obtained during closest approach (CA) to the Earth in order to get more observational points and extend observational arc. It is especially important for newly discovered NEAs when high-precision astrometry is required to determine and improve the orbital elements making them recoverable in next apparitions. The latest astrometric results of NEAs observations, particularly for newly discovered ones, are presented and analyzed in order to refine their orbits and estimate possible recovery in next CA. The comparative analysis of astrometric positions and orbital elements were done regarding to International Astronomical Union Minor Planet Center database and JPL's HORIZONS ephemerides system. The residual differences (O – C) often show high values for newly discovered NEAs during observation date which explained by lack of available observations for reliable calculations of ephemerid positions. The data for such NEAs is presented and orbital calculations are done.

A Beacon in the Galaxy: Updated Arecibo Message for Potential FAST and SETI Projects

An updated, binary-coded message has been developed for transmission to extraterrestrial intelligences in the Milky Way galaxy. The proposed message includes basic mathematical and physical concepts to establish a universal means of communication followed by information on the biochemical composition of life on Earth, the Solar System’s time-stamped position in the Milky Way relative to known globular clusters, as well as digitized depictions of the Solar System, and Earth’s surface. The message concludes with digitized images of the human form, along with an invitation for any receiving intelligences to respond. Calculation of the optimal timing during a given calendar year is specified for potential future transmission from both the Five-hundred-meter Aperture Spherical radio Telescope in China and the SETI Institute’s Allen Telescope Array in northern California to a selected region of the Milky Way which has been proposed as the most likely location for life to have developed. These powerful new beacons, the successors to the Arecibo radio telescope which transmitted the 1974 message upon which this expanded communication is in part based, can carry forward Arecibo’s legacy into the 21st century with this equally well-constructed communication from Earth’s technological civilization.

New photometric studies for two deep, low-mass ratio overcontact binaries: Y Sex and V1363 Ori

We present new photometry for two contact binaries, Y Sex and V1363 Ori, which were observed by three small telescopes in China. By using the W-D method, the absolute parameters are updated from new BVR light curves and previous radial velocity curves. Results identify that two binaries are deep, low-mass ratio (DLMR) overcontact binaries with q ⩽ 0.25 and f ⩾ 50%. From the temperature-luminosity diagram, the primary components are slightly evolved main-sequence stars, whose evolutionary ages are ∼2.51 Gyr for Y Sex and ∼3.56 Gyr for V 1363 Ori, respectively. From the (O − C) curves, it is found that the orbital periods may be undergoing secular increase with cyclic variations, which may be interpreted either by magnetic activity cycles or by the light-time orbit effect. With period increasing, this kind of DLMR overcontact binaries, such as Y Sex and V1363 Ori, will evolve into the rapid-rotating single stars.

The Operation of Multi-beam Receiver of Delingha 13.7 m Telescope

Delingha 13.7m telescope is one of the most important radio telescopes in China. Since installing the superconducting spectroscopic array receiver (SSAR) and adopting the On The Fly (OTF) observation mode, the telescope has operated for nearly 10 years. During this period, a large number of astronomical observation projects have been carried out and completed, a large amount of astronomical data have been accumulated, and a series of important scientific results have been achieved. This paper introduces the operating status of SSAR in astronomical observations, the problems in operations, as well as the fault phenomena and solutions. The performance test and performance analysis of SSAR are described in detail, including the receiver noise temperature and telescope system noise temperature, image rejection ratio (IRR), receiver stability, beam performance and so on. The updating and development of SSAR are listed, including the automatic adjustment of LO (Local Oscillator) power, the updating of pre-amplification circuits of the sideband separation superconducting mixer, and the optimization of control program, etc. This paper summarizes the experiences and rules, and connects the past with the future, for applying the experiences of the maintenance and operation of SSAR to the next-generation large-scale receiver system.

East Asian VLBI Network observations of active galactic nuclei jets: imaging with KaVA+Tianma+Nanshan

The East Asian Very Long Baseline Interferometry (VLBI) Network (EAVN) is a rapidly evolving international VLBI array that is currently promoted under joint efforts among China, Japan and Korea. EAVN aims at forming a joint VLBI Network by combining a large number of radio telescopes distributed over East Asian regions. After the combination of the Korean VLBI Network (KVN) and the VLBI Exploration of Radio Astrometry (VERA) into KaVA, further expansion with the joint array in East Asia is actively promoted. Here we report the first imaging results (at 22 and 43 GHz) of bright radio sources obtained with KaVA connected to Tianma 65-m and Nanshan 26-m Radio Telescopes in China. To test the EAVN imaging performance for different sources, we observed four active galactic nuclei (AGN) having different brightness and morphology. As a result, we confirmed that the Tianma 65-m Radio Telescope (TMRT) significantly enhances the overall array sensitivity, a factor of 4 improvement in baseline sensitivity and 2 in image dynamic range compared to the case of KaVA only. The addition of the Nanshan 26-m Radio Telescope (NSRT) further doubled the east-west angular resolution. With the resulting high-dynamic-range, high-resolution images with EAVN (KaVA+TMRT+NSRT), various fine-scale structures in our targets, such as the counter-jet in M87, a kink-like morphology of the 3C 273 jet and the weak emission in other sources are successfully detected. This demonstrates the powerful capability of EAVN to study AGN jets and to achieve other science goals in general. Ongoing expansion of EAVN will further enhance the angular resolution, detection sensitivity and frequency coverage of the network.

Modeling and experiment validation of thermal control for the heat-stop of the Chinese Large Solar Telescope

Thermal control system is one of the most important components of large ground-based solar telescope. Heat-stop is one of the key components for controlling thermal effects for a large solar telescope, which reflects over 95% of solar radiation protecting the relay optics and post-focus instruments. Meanwhile, a part of solar radiation has also converted into thermal energy, which will lead to internal seeing effect. Thus, the thermal control for heat-stop is a necessary work. We deduce a mathematical model to express the relationship between thermal response of heat-stop and its structure design, ambient environment, and coolant input. We also experimentally validate the feasibility of the proposed method based on the Chinese Large Solar Telescope, which is the largest solar telescope in China. The experimental results show that the temperature difference between the experimental results and calculated results based the proposed model is <2 ° C. Moreover, the temperature difference between the surface temperature of the heat-stop and the ambient temperature can satisfy thermal control requirement of ±5 ° C. Therefore, it can be verified that our model is correct and consistent with the actual situation.

LHAASO discovery of highest-energy photons towards new physics

Ultrahigh-energy photons up to 1.4 peta-electronvolts have been observed by new cosmic-ray telescope in China -- a hint that Lorentz invariance might break down at the Planck-scale level.

Scanning the Milky Way for 10 years: Discoveries from the Sino-German 6 cm polarization survey of the Galactic plane

<p indent=0mm>Radio continuum polarization observation is a powerful tool to study the properties of the Galactic interstellar medium. By using the 25-m radio telescope of Xinjiang Astronomical Observatories of Chinese Academy of Sciences the Sino-German 6 cm polarization survey of the Galactic plane was carried out by the National Astronomical Observatories of Chinese Academy of Sciences and the Max-Planck-Institute for Radio Astronomy. The observed sky coverage is the Galactic plane in the region from 10° to 230° in the Galactic longitude and within ±5° in the Galactic latitude. The survey is by far at the highest frequency for a Galactic plane polarization survey conducted by a ground-based radio telescope. Through the ten-year efforts by the Chinese and German scientists, the survey revealed the distribution of the total intensity emission and the orientation in the sky plane of the Galactic magnetic fields, which allows us to paint a scroll of the Galaxy with the data obtained with a telescope in China. At such a higher frequency than that of other surveys over the world, the <sc>6 cm</sc> observations experience less Faraday rotations, and are thus able to detect the polarized emission from a further distance. Based on the survey data, we have obtained a series of results on Galactic supernova remnants (SNRs), HII regions and Faraday screens with high rotation measures. Four new Galactic SNRs have been discovered, among which G178.2–4.2 and G25.1–2.3 published in 2011 are the first discovery of Galactic SNRs by a Chinese radio telescope using the first-hand data. Measurements of flux densities, polarization and spectra were performed for more than 70 known SNRs. The polarized emission is observed, for the first time, for the SNRs G16.2–2.7, G69.7+1.0, G84.2–0.8, G85.9–0.6, G205.5+0.5 and G206.9+2.3. The accurate measurements of the <sc>6 cm</sc> flux densities are crucial to determine the spectra of 20 SNRs. Measurements and statistic studies were made for 401 HII regions toward which the flux densities can be precisely estimated. The result complemented the WISE HII region catalog with regards on the extended sources and fixed the mistakes in the commonly used radio HII region catalog. For the diffuse polarized emission, we have detected many new intriguing structures with high Faraday rotation measures which cannot be observed at low radio frequencies because of severe depolarization. These structures, referred to as Faraday screens, do not have total intensity correspondents, indicating the necessity of polarization observations in understanding the Galactic interstellar medium. The <sc>6 cm</sc> survey data have been made public and the results have already generated high impacts on relevant research fields. The project has demonstrated that a medium size telescope such as the <sc>25 m</sc> dish used for the survey is also capable of achieving great science, and the key is to find the niche in this case which is the polarization survey of the Galactic plane. The survey not only produced exciting results on the polarized emission from the Galaxy but also trained next generation radio astronomers who are now active for large facilities such as the Five-hundred-meter Aperture Spherical radio Telescope (FAST) and the Square Kilometre Array (SKA).

Automatic Classification of NVST Short-exposure Data Based on Deep Learning

The New Vacuum Solar Telescope is one of the most important solar telescopes in China. However, in the process of reconstructing high-resolution solar data, the data may be distorted by thin film interference fringes. In this paper, an automatic classification method based on deep learning is proposed to distinguish fringe-contained data and fringe-free data, employing the Adaptive Wavelet Transform to construct the sample data set while transfer learning is utilized to train the classification model. The experimental results show that classification accuracy of the proposed method can reach up to 99.3%. This proposed method can make the high-resolution reconstruction pipeline run automatically whether the solar data contains fringes or not.

High-resolution Chromospheric Observations of a Solar Minifilament: Formation and Destabilization

Abstract Using H α line core and off-band imaging data from the New Vacuum Solar Telescope in China, we present a high-resolution observation on the entire life cycle of a solar minifilament from its birth to its final eruption. We find that the minifilament originates from a series of cascade-like reconfigurations of chromospheric fine structures. During which, owing to strong photospheric shearing and converging flows near its polarity inversion line, basic short chromospheric fibrils first slowly coalesce to elongated dark threads, and then further create a longer filament channel in a “head-to-tail” linkage scenario. In this course, obvious magnetic flux cancelation simultaneously proceeds below it, and further facilitates its destabilization. In its onset phase, clear clues indicate that the minifilament first starts to rise without brightening signals; instead, after a slow-to-fast acceleration, obvious runaway reconnection soon takes over its final jet-like eruption. Besides, off-band observations further reveal that the formed minifilament has a possible flux-rope configuration, and chromospheric upflows that detected in its early forming phase persistently supplies cool plasma into its channel. This observation is consistent with earlier observations and supports the view that both miniature and large-scale filaments may share analogous formation and destabilization mechanisms.

Preface: Site testing campaign for the Large Optical/infrared Telescope of China

The Large Optical/infrared Telescope of China is a 12 meter diameter ground-based optical/infrared telescope which is proposed to be constructed in the western part of China in favor of its arid climate, and clear, dark nights. A site testing campaign was initiated between November 2016 and March 2019 in order to investigate long term astronomical weather conditions in the western part of China, specifically, at three sites: Ali in Tibet, Daocheng in Sichuan and Muztagh-ata in Xinjiang. This is the first attempt to evaluate long term performances of three candidate sites with uniformly calibrated instruments and data collecting/processing methods for a two-year span in China. In this special issue, we present nine papers that describe the whole site testing campaign, including preparation, data collecting/processing methods, instrument set up at three candidate sites as well as detailed statistics for the measurement results from March 2017 to March 2019.

Site testing campaign for the Large Optical/infrared Telescope of China: overview

The Large Optical/infrared Telescope (LOT) is a ground-based 12 m diameter optical/infrared telescope which is proposed to be built in the western part of China in the next decade. Based on satellite remote sensing data, along with geographical, logistical and political considerations, three candidate sites were chosen for ground-based astronomical performance monitoring. These sites include: Ali in Tibet, Daocheng in Sichuan and Muztagh-ata in Xinjiang. Up until now, all three sites have continuously collected data for two years. In this paper, we will introduce this site testing campaign, and present its monitoring results obtained during the period between March 2017 and March 2019.

A Detailed Investigation on the Infrared-excess Binary EG Cassiopeiae

In this study, new data concerning the EB-type eclipsing binary EG Cas are presented as observed using three telescopes in China. A spectral type of F0V was determined from the low-precision spectrum. By solving the radial velocity and BV light curves, the absolute parameters of this system are preliminarily deduced. The results imply that EG Cas is a semi-detached binary with the secondary star filling its Roche lobe. An unequal height between the light maxima (i.e., ≲0.02 mag) of the light curves is modeled with the addition of a magnetic dark spot on the surface of the less-massive component. Analyzing the O − C curve a secular decrease at is identified in the orbital period, which corresponds to a mass-loss rate of in the case of non-conserved evolution of the binary. From the spectral energy distribution, an excess in the infrared occurs in the WISE W4 band, which may be attributed to the circumstellar envelope due to mass loss via the stellar magnetic wind. With the ongoing mass transfer and loss, this kind of F-type near-contact binary will eventually evolve into an A-subtype contact binary, as predicted by the thermal relaxation oscillation theory.

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.

IU Cancri: a solar-type contact binary with mass transfer

We present new CCD photometry of the solar-type contact binary IU Cnc, which was observed from November 2017 to March 2018 with three small telescopes in China. BV light curves imply that IU Cnc is a W-type contact binary with total eclipses. The photometric solution indicates that the mass ratio and fill-out factor are q = 4.104 ± 0.004 and f = 30.2% ± 0.3%, respectively. From all available light minimum times, the orbital period may increase at a rate of dP/dt = +6.93(4) × 10−7 d yr−1, which may result from mass transfer from the secondary component to the primary one. With mass transferring, IU Cnc may evolve from a contact configuration into a semi-detached configuration.

POST—prototype for the Chinese Large Solar Telescope

For a better understanding of small-scale solar activities, the Chinese Large Solar Telescope (CLST) with a 1.8-m aperture was proposed in 2011. As the first open solar telescope in China, it has some technical challenges that need to be addressed (e.g., thermal controlling for the primary mirror, cooling for the heat stop, system assembly, etc.). To support the design of CLST, a prototype of an open solar telescope (POST) with a 600-mm aperture was designed and fabricated from 2014 to 2017. A series of experiments for technical verifications were carried out based on the POST. The design, integration, and experiments done with the POST are reviewed. The solar observation results during its first commissioning phase are also presented.

Blind search for 21-cm absorption systems using a new generation of Chinese radio telescopes

Neutral hydrogen clouds are known to exist in the Universe, however their spatial distributions and physical properties are poorly understood. Such missing information can be studied by the new generation of Chinese radio telescopes through a blind search of 21-cm absorption systems. We forecast the capabilities of surveys of 21-cm absorption systems by two representative radio telescopes in China –the Five-hundred-meter Aperture Spherical radio Telescope (FAST) and Tianlai 21-cm cosmology experiment (Tianlai). Facilitated by either the high sensitivity (FAST) or wide field of view (Tianlai) of these telescopes, more than a thousand 21-cm absorption systems can be discovered in a few years, representing orders of magnitude improvement over the cumulative discoveries in the past half a century.