Search

We describe the photometric calibration of the Lunar-based Ultraviolet Telescope (LUT), the first robotic astronomical telescope working on the lunar surface, for its first six months of operation on the lunar surface. Two spectral datasets (set A and B) from near-ultraviolet (NUV) to the optical band were constructed with 44 International Ultraviolet Explorer (IUE) standards, because of the LUT’s relatively wide wavelength coverage. Set A was obtained by extrapolating the IUE NUV spectra (λ < 3200 A ) to the optical band based upon the theoretical spectra of stellar atmosphere models. Set B was composed of theoretical spectra from 2000 A to 8000 A extracted from the same model grid. In total, seven standards have been observed in 15 observational runs until May 2014. The calibration results show that the photometric performance of LUT is highly stable in its first six months of operation. The magnitude zero points obtained from the two spectral datasets are also consistent with each other, i.e., zp = 17.54 ± 0.09 mag (set A) and zp = 17.52 ± 0.07 mag (set B).

Tsinghua-NAOC (National Astronomical Observatories of China) Telescope (hereafter, TNT) is an 80-cm Cassegrain reflecting telescope located at Xinglong bservatory of NAOC, with main scientific goals of monitoring various transients in the universe such as supernovae, gamma-ray bursts, novae, variable stars, and active galactic nuclei. We present in this paper a systematic test and analysis of the photometric performance of this telescope. Based on the calibration observations on twelve photometric nights, spanning the period from year 2004 to year 2012, we derived an accurate transformation relationship between the instrumental $ubvri$ magnitudes and standard Johnson $UBV$ and Cousins $RI$ magnitudes. In particular, the color terms and the extinction coefficients of different passbands are well determined. With these data, we also obtained the limiting magnitudes and the photometric precision of TNT. It is worthwhile to point out that the sky background at Xinglong Observatory may become gradually worse over the period from year 2005 to year 2012 (e.g., $\sim$21.4 mag vs. $\sim$20.1 mag in the V band)., 12 pages,9 figures, accepted by RAA

The PLATeau Observatory (PLATO) is an automated self-powered astrophysical observatory that was deployed to Dome A, the highest point on the Antarctic plateau, in 2008 January. PLATO consists of a suite of site-testing instruments designed to quantify the benefits of the Dome A site for astronomy, and science instruments designed to take advantage of the unique observing conditions. Instruments include CSTAR, an array of optical telescopes for transient astronomy; Gattini, an instrument to measure the optical sky brightness and cloud cover statistics; DASLE, an experiment to measure the statistics of the meteorological conditions within the near-surface layer; Pre-HEAT, a submillimeter tipping radiometer measuring the atmospheric transmission and water vapor content and performing spectral line imaging of the Galactic plane; and Snodar, an acoustic radar designed to measure turbulence within the near-surface layer. PLATO has run completely unattended and collected data throughout the winter 2008 season. Here we present a detailed description of the PLATO instrument suite and preliminary results obtained from the first season of operation.

87 stars in the NGC 6913 field with both UBV and Vilnius photometry are selected to be the sample. The membership probability of the stars is greater than 50%. The correlation among Vilnius photometry, UBV photometry and reddening in the cluster is reviewed. It is found that the photometry in the Vilnius X, Y and Z bands can be used to make rough spectral classification. The values of E( B-V ) are well correlated with the Vilnius colors of X-Y, Y-Z, Z-V and V-S in NGC 6913. The ratio of ( V-S )/( Y-Z ) of the MPCM (Most Possible Cluster Members) is a constant (1.30 ∼ p0.06), and has no effect on the values of E( B-V ), ( B-V ) 0 and V 0 . Comparing with the observational data of all the stars of NGC 6913 region, we propose that the value of ( V-S )/( Y-Z ) can probably be used to select the preliminary candidates of one open cluster. In addition, 12 variable stars are discovered in the NGC 6913 region, in which star #155 has a variation with an amplitude of 4.25 mag.

For investigating the statistical properties of X-ray selected Active Galactic Nuclei (AGNs), we have carried out a program of optical identification of a selection of X-ray sources from ROSAT All Sky Survey Bright Source Catalogue (RASS-BSC) using the 2.16 m telescope of Beijing Astronomical Observatory (BAO). In the preliminary observations, 23 new AGNs were discovered, of which 9 are quasars, and 14 are Seyfert galaxies.

We present a catalogue including 11,204 spectra for 10,436 early-type emission-line stars from LAMOST DR2, among which 9,752 early-type emission-line spectra are newly discovered. For these early-type emission-line stars, we discuss the morphological and physical properties from their low-resolution spectra. In this spectral sample, the H$\alpha$ emission profiles display a wide variety of shapes. Based on the H$\alpha$ line profiles, these spectra are categorized into five distinct classes: single-peak emission, single-peak emission in absorption, double-peak emission, double-peak emission in absorption, and P-Cygni profiles. To better understand what causes the H$\alpha$ line profiles, we divide these objects into four types from the view of physical classification, which include classical Be stars, Herbig Ae/Be stars, close binaries and spectra contaminated by HII regions. The majority of Herbig Ae/Be stars and classical Be stars are identified and separated using the (H-K, K-W1) color-color diagram. We also discuss thirty one binary systems as listed in SIMBAD on-line catalogue and identify 3,600 spectra contaminated by HII regions after cross matching with positions in the Dubout-Crillon catalogue. A statistical analysis of line profiles versus classifications is then conducted in order to understand the distribution of H$\alpha$ profiles for each type in our sample. Finally, we also provide a table of 172 spectra with FeII emission lines and roughly calculate stellar wind velocities for seven spectra with P-Cygni profiles., Comment: 18 pages, 10 figures and 4 tables