Digitization technologies applied to historical newspapers have changed the research landscape historians were used to. An Eldorado? Despite unquestionable merits, the new digital affordance of ...historical newspapers also brings drawbacks and possible pitfalls which need to be carefully assessed.
ABSTRACT The Chinese Small Telescope Array (CSTAR) carried out high-cadence time-series observations of ∼20.1 square degrees centered on the South Celestial Pole during the 2008, 2009, and 2010 ...winter seasons from Dome A in Antarctica. The nearly continuous six months of dark conditions during each observing season allowed for > 10 6 images to be collected through gri and clear filters, resulting in the detection of > 10 4 sources over the course of three years of operation. The nearly space-like conditions in the Antarctic plateau are an ideal testbed for the suitability of very small-aperture ( < 20 cm) telescopes to detect transient events, variable stars, and stellar flares. We present the results of a robust search for such objects using difference image analysis of the data obtained during the 2009 and 2010 winter seasons. While no transients were found, we detected 29 flaring events and find a normalized flaring rate of 5 4 × 10−7 flare hr−1 for late-K dwarfs, 1 1 × 10−6 flare hr−1 for M dwarfs and 7 1 × 10−7 flare hr−1 for all other stars in our sample. We suggest future small-aperture telescopes planned for deployment at Dome A would benefit from a tracking mechanism, to help alleviate effects from ghosting, and a finer pixel scale, to increase the telescope's sensitivity to faint objects. We find that the light curves of non-transient sources have excellent photometric qualities once corrected for systematics, and are limited only by photon noise and atmospheric scintillation.
Precise astronomical spectroscopic analyses routinely assume that individual pixels in charge-coupled devices (CCDs) have uniform sensitivity to photons. Intra-pixel sensitivity (IPS) variations may ...already cause small systematic errors in, for example, studies of extra-solar planets via stellar radial velocities and cosmological variability in fundamental constants via quasar spectroscopy, but future experiments requiring velocity precisions approaching ∼1 cm s−1 will be more strongly affected. Laser frequency combs have been shown to provide highly precise wavelength calibration for astronomical spectrographs, but here we show that they can also be used to measure IPS variations in astronomical CCDs in situ. We successfully tested a laser frequency comb system on the Ultra-High-Resolution Facility spectrograph at the Anglo-Australian Telescope. By modelling the two-dimensional comb signal recorded in a single CCD exposure, we find that the average IPS deviates by <8 per cent if it is assumed to vary symmetrically about the pixel centre. We also demonstrate that a series of comb exposures with absolutely known offsets between them can yield tighter constraints on symmetric IPS variations from ∼100 pixels. We discuss measurement of asymmetric IPS variations and absolute wavelength calibration of astronomical spectrographs and CCDs using frequency combs.
ABSTRACT We report the discovery of low-amplitude oscillations in the star HD 92277 from long, continuous observations in the r and g bands using the CSTAR telescopes in Antarctica. A total of more ...than 1950 hours of high-quality light curves were used to categorize HD 92277 as a new member of the δ Scuti class. We have detected 21 (20 frequencies are independent and one is the linear combination) and 14 (13 frequencies are independent and one is the linear combination) pulsation frequencies in the r and g bands, respectively, indicating a multi-periodic pulsation behavior. The primary frequency f1 = 10.810 days−1 corresponds to a period of 0.0925 days and is an l = 1 mode. We estimate a B − V index of 0.39 and derive an effective temperature of 6800 K for HD 92277. We conclude that long, continuous and uninterrupted time-series photometry can be performed from Dome A, Antarctica, and that this is especially valuable for asteroseismology where multi-color observations (often not available from space-based telescopes) assist with mode identification.
We analyse the near-infrared interline sky background, OH and O2 emission in 19 h of H-band observations with the GNOSIS OH-suppression unit and the IRIS2 spectrograph at the 3.9-m Anglo-Australian ...Telescope. We find that the long-term behaviour of OH emission is best described by a gradual decrease during the first half of the night followed by a gradual increase during the second half of the night following the behaviour of the solar elevation angle. We measure the interline background at 1.520 μm where the instrumental thermal background is very low and study its variation with zenith distance, time after sunset, ecliptic latitude, lunar zenith distance and lunar distance to determine the presence of non-thermal atmospheric emission, zodiacal scattered light and scattered moonlight. Zodiacal scattered light is too faint to be detected in the summed observations. Scattered moonlight due to Mie scattering by atmospheric aerosols is seen at small lunar distances (ρ 11°), but is otherwise too faint to detect. Except at very small lunar distances the interline background at a resolving power of R 2400 when using OH-suppression fibres is dominated by a non-thermal atmospheric source with a temporal behaviour that resembles atmospheric OH emission, suggesting that the interline background contains instrumentally scattered OH. However, the interline background dims more rapidly than OH early in the night, suggesting contributions from rapid dimming molecules. The absolute interline background is 560 ± 120 photons s−1 m−2 μm− 1 arcsec−2 under dark conditions. This value is similar to previous measurements without OH suppression, suggesting that non-suppressed atmospheric emission is responsible for the interline background level. Future OH-suppression fibre designs may address this by the suppression of more sky lines using more accurate sky-line measurements taken from high-resolution spectra.
In common with many strongly correlated electron systems, intermediate valence compounds are believed to display a crossover from a high-temperature regime of incoherently fluctuating local moments ...to a low-temperature regime of coherent hybridized bands. We show that inelastic neutron scattering measurements of the dynamic magnetic susceptibility of CePd
provides a benchmark for ab initio calculations based on dynamical mean field theory. The magnetic response is strongly momentum dependent thanks to the formation of coherent f-electron bands at low temperature, with an amplitude that is strongly enhanced by local particle-hole interactions. The agreement between experiment and theory shows that we have a robust first-principles understanding of the temperature dependence of f-electron coherence.
Anyone who attempts to understand and reverse the major defeat suffered by Labour in the December 2019 general election needs first to appreciate why comparisons with the defeats of the 1980s are so ...unhelpful. In 1983 Labour was all but wiped out across southern England, but held on comfortably across the ‘red wall’. By contrast, in 2019 Labour did well in cities and university towns across the south, and appears to have solved its historic problem with the southern, educated middle class. However, this has been at the expense of alienating working class voters across the country, not just in its former industrial heartlands. But this is not inevitable. A reanalysis of testimony from hundreds of interviews with working people across England from the 1940s onwards allows insights into attitudes and values that are often obscured by survey techniques. Crucially, it points to a broad‐based vernacular liberalism at odds with the culture wars model of a terminal crisis for social democracy.
We present results from a season of observations with the Chinese Small Telescope ARray, obtained over 183 days of the 2010 Antarctic winter. We carried out high-cadence time-series aperture ...photometry of 9125 stars with i lap 15.3 mag located in a 23 deg super(2) region centered on the south celestial pole. We identified 188 variable stars, including 67 new objects relative to our 2008 observations, thanks to broader synoptic coverage, a deeper magnitude limit, and a larger field of view. We used the photometric data set to derive site statistics from Dome A. Based on two years of observations, we find that extinction due to clouds at this site is less than 0.1 and 0.4 mag during 45% and 75% of the dark time, respectively.
We present the first scientific results from the Sydney-AAO Multi-Object IFS (SAMI) at the Anglo-Australian Telescope. This unique instrument deploys 13 fused fiber bundles (hexabundles) across a ...one-degree field of view allowing simultaneous spatially resolved spectroscopy of 13 galaxies. During the first SAMI commissioning run, targeting a single galaxy field, one object (ESO 185-G031) was found to have extended minor axis emission with ionization and kinematic properties consistent with a large-scale galactic wind. The importance of this result is twofold: (1) fiber bundle spectrographs are able to identify low surface brightness emission arising from extranuclear activity and (2) such activity may be more common than presently assumed because conventional multi-object spectrographs use single-aperture fibers and spectra from these are nearly always dominated by nuclear emission. These early results demonstrate the extraordinary potential of multi-object hexabundle spectroscopy in future galaxy surveys.
Dome A on the Antarctic plateau is likely one of the best observing sites on Earth thanks to the excellent atmospheric conditions present at the site during the long polar winter night. We present ...high-cadence time-series aperture photometry of 10,000 stars with i < 14.5 mag located in a 23 deg2 region centered on the south celestial pole. The photometry was obtained with one of the CSTAR telescopes during 128 days of the 2008 Antarctic winter. We used this photometric data set to derive site statistics for Dome A and to search for variable stars. Thanks to the nearly uninterrupted synoptic coverage, we found six times as many variables as previous surveys with similar magnitude limits. We detected 157 variable stars, of which 55% were unclassified, 27% were likely binaries, and 17% were likely pulsating stars. The latter category includes Delta *d Scuti, Delta *g Doradus, and RR Lyrae variables. One variable may be a transiting exoplanet.