D. J. Christian
A5053844705- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Solar and Space Plasma Dynamics
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Nuclear Physics and Applications
- Adaptive optics and wavefront sensing
- Galaxies: Formation, Evolution, Phenomena
- Ionosphere and magnetosphere dynamics
- Geomagnetism and Paleomagnetism Studies
- Planetary Science and Exploration
- Geophysics and Gravity Measurements
- Atmospheric Ozone and Climate
- Pulsars and Gravitational Waves Research
- Isotope Analysis in Ecology
- CCD and CMOS Imaging Sensors
- Atomic and Molecular Physics
- Calibration and Measurement Techniques
- History and Developments in Astronomy
- Astrophysics and Cosmic Phenomena
- Solar Radiation and Photovoltaics
- Scientific Measurement and Uncertainty Evaluation
California State University, Northridge
2014-2023
Queen's University Belfast
2004-2020
Boise State University
2019
California State University System
2013-2015
Laboratoire d’Études en Géophysique et Océanographie Spatiales
2013
University of Liège
2013
Georgetown University
2012
California Polytechnic State University
2011
Eureka Scientific
1999-2010
Goddard Space Flight Center
1994-2009
The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere collect spectra ≈106 galaxies, 100,000 quasars, 30,000 stars, serendipity targets. In 2001 June, SDSS released to general astronomical community its early data release, roughly 462 deg2 including almost 14 million detected objects 54,008 follow-up spectra. were collected in drift-scan mode five bandpasses (u, g, r, i, z); our 95% completeness...
The SuperWASP cameras are wide‐field imaging systems at the Observatorio del Roque de los Muchachos on island of La Palma in Canary Islands, and Sutherland Station South African Astronomical Observatory. Each instrument has a field view some 482 deg2 with an angular scale 13 7 pixel−1, is capable delivering photometry accuracy better than 1% for objects having V∼7.0–11.5. Lower quality data brighter V∼15.0 stored project archive. systems, while designed to monitor fields high cadence,...
The flow of energy through the solar atmosphere and heating Sun's outer regions are still not understood. Here, we report detection oscillatory phenomena associated with a large bright-point group that is 430,000 square kilometers in area located near disk center. Wavelet analysis reveals full-width half-maximum oscillations periodicities ranging from 126 to 700 seconds originating above bright point significance levels exceeding 99%. These oscillations, 2.6 per second amplitude, coupled...
We report on the discovery of WASP-12b, a new transiting extrasolar planet with $R_{\rm pl}=1.79 \pm 0.09 R_J$ and $M_{\rm pl}=1.41 0.1 M_J$. The host star properties were derived from Monte Carlo Markov Chain analysis transit photometry radial velocity data. Furthermore, by comparing stellar spectrum theoretical spectra evolution models, we determined that is super-solar metallicity ([M/H]$=0.3^{+0.05}_{-0.15}$), late-F (T$_{\rm eff}=6300^{+200}_{-100}$ K) which evolving off zero age main...
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not.The documents may come from teaching institutions in France abroad, public private centers.L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de scientifiques niveau recherche, publiés ou non, émanant des établissements d'enseignement recherche français étrangers, laboratoires publics privés.
We have detected low-amplitude radial-velocity variations in two stars, USNO-B1.0 1219-0005465 (GSC 02265-00107 = WASP-1) and 0964-0543604 00522-01199 WASP-2). Both stars were identified as being likely host of transiting exoplanets the 2004 SuperWASP wide-field transit survey. Using newly-commissioned spectrograph SOPHIE at Observatoire de Haute-Provence, we found that both objects exhibit reflex orbital with amplitudes characteristic planetary-mass companions in-phase photometric orbits....
We report the discovery of WASP-3b, third transiting exoplanet to be discovered by WASP and SOPHIE collaboration. WASP-3b transits its host star USNO-B1.0 1256−0285133 every 1.846 834 ± 0.000 002 d. Our high-precision radial velocity measurements present a variation with amplitude characteristic planetary-mass companion in phase light curve. Adaptive optics imaging shows no evidence for nearby stellar companions, line-bisector analysis excludes faint, unresolved binarity activity as cause...
We present a fast and efficient hybrid algorithm for selecting exoplanetary candidates from wide-field transit surveys. Our method is based on the widely-used SysRem Box Least-Squares (BLS) algorithms. Patterns of systematic error that are common to all stars frame mapped eliminated using algorithm. The remaining errors caused by spatially localised flat-fielding other quantified boxcar-smoothing method. show dimensions search-parameter space can be reduced greatly carrying out an initial...
We report the discovery of WASP-4b, a large transiting gas-giant planet with an orbital period 1.34 days. This is first to be discovered by SuperWASP-South observatory and CORALIE collaboration orbiting star brighter than 16th magnitude in southern hemisphere. A simultaneous fit high-quality light curves precision radial velocity measurements leads planetary mass 1.22+ 0.09−0.08 MJup radius 1.42+ 0.07−0.04 RJup. The host USNO-B1.0 0479–0948995, G7 V visual 12.5. As result short period,...
The HEAO 2 or Einstein solid-state spectrometer (SSS; 0.5-4.5 keV) and monitor proportional counter (MPC; 1.2-20.0 carried out an extensive survey of 49 low-mass X-ray binaries (LMXBs). Simultaneous SSS plus MPC spectra, selected on the basis their intensity, were fitted with a set simple complex spectral models. For all sources, including Eddington-limited bulge bursters, dippers, soft spectrum black hole candidates, few transients in decline, spectra could be acceptably combinations...
Using soft x-ray observations of the bright new comet C/1999 S4 (LINEAR) with Chandra observatory, we have detected line emission created by charge exchange between highly ionized solar wind minor ions and neutral gases in comet's coma. The morphology was symmetrically crescent shaped extended out to 300,000 kilometers from nucleus. spectrum contains 6 lines at 320, 400, 490, 560, 600, 670 electron volts, attributable capture radiative deexcitation species C(+5), C(+6), N(+7), O(+7), O(+8)....
We present optical lightcurves of 428 periodic variable stars coincident with ROSAT X-ray sources, detected using the first run SuperWASP photometric survey. Only 68 these were previously recognised as variables. A further 30 objects are known pre-main sequence stars, for which we detect a modulation period time. Amongst newly identified variables, many appear to be close eclipsing binaries, their emission is presumably result RS CVn type behaviour. Others probably BY Dra and other rapid...
We report the discovery of a 7.3 Mjup exoplanet WASP-14b, one most massive transiting exoplanets observed to date. The planet orbits tenth-magnitude F5V star USNO-B1 11118-0262485 with period 2.243752 days and orbital eccentricity e = 0.09. A simultaneous fit transit light curve radial velocity measurements yields planetary mass 7.3+/-0.5 radius 1.28+/-0.08 Rjup. This leads mean density about 4.6 g/cm^3 making it densest yet found at an less than 3 days. estimate this system be distance...
We present light curves and periods of 53 candidates for short period eclipsing binary stars identified by SuperWASP. These include 48 newly objects with <2x10^4 seconds (~0.23d), as well the shortest known main sequence components (GSC2314-0530 = 1SWASP J022050.85+332047.6) four other previously W UMa (although reported two these are shown to be incorrect). The distribution contact binaries shows a sharp cut-off at lower limit around 0.22d, but until now, very few systems were close this...
Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths using techniques that are impossible with an in situ flyby. We report here such support of the EPOXI spacecraft flyby comet 103P/Hartley 2. The nucleus is small dark, exhibited a very rapidly changing rotation period. Prior to onset activity, period was ∼16.4 hr. Starting 2010 August changed from 16.6 hr near 19 December. With...
We present observational evidence of compressible MHD wave modes propagating from the solar photosphere through to base transition region in a magnetic pore. High cadence images were obtained simultaneously across four wavelength bands using Dunn Solar Telescope. Employing Fourier and wavelet techniques, sausage-mode oscillations displaying significant power detected both intensity area fluctuations. The fluctuations exhibit range periods 181 412 s, with an average period ∼290 consistent...
We use images of high spatial, spectral, and temporal resolution, obtained using both ground- space-based instrumentation, to investigate the coupling between wave phenomena observed at numerous heights in solar atmosphere. Analysis 4170 Å continuum reveals small-scale umbral intensity enhancements, with diameters ∼06, lasting excess 30 minutes. Intensity oscillations ≈3 minutes are encompass these photospheric structures, power least three orders magnitude higher than surrounding umbra....
We have studied over 1600 Am stars at a photometric precision of 1 mmag with SuperWASP data. Contrary to previous belief, we find that around 200 are pulsating delta Sct and gamma Dor stars, low amplitudes been missed in previous, less extensive studies. While the generally low, presence pulsation places strong constraint on atmospheric convection, may require be laminar. some previously found vast majority known pulsate presented this paper. They will form basis future statistical studies...
Spectropolarimetric observations of the extreme-ultraviolet (EUV) source and high-field magnetic white dwarf EUVE J0317—855 ( = RE J0317—853) in wavelength range 4200–7200 Å reveal a strongly structured circular polarization spectrum with peak 8 per cent. The strongest features are attributed to Hα 2s0-3p1, 2s0-3p0 Hβ 2s0-4f-1, 2s0-4f0 2s0-4p1 field 100–300 MG. phase-averaged data modelled using centred off-centred dipole structures, reasonable fit was obtained for strength Bd 450 MG...
Aims.We present results of the analysis cometary X-ray spectra with an extended version our charge exchange emission model (Bodewits et al. 2006). We have applied this to sample 8 comets thus far observed Chandra observatory and acis spectrometer in 300–1000 eV range. The surveyed are C/1999 S4 (linear), T1 (McNaught–Hartley), C/2000 WM1 153P/2002 (Ikeya–Zhang), 2P/2003 (Encke), C/2001 Q4 (neat), 9P/2005 (Tempel 1) 73P/2006-B (Schwassmann–Wachmann 3) observations include a broad variety...
We present the results of a photometric survey rotation rates in Coma Berenices (Melotte 111) open cluster, using data obtained as part SuperWASP exoplanetary transit-search programme. The goal was to measure precise periods for main-sequence F, G and K dwarfs this intermediate-age (∼600 Myr) determine extent which magnetic braking has caused stellar spin converge. find tight, almost linear relationship between period J−K colour with an rms scatter only 2 per cent. relation is similar that...
Some of the first results are reported from RISE – a new fast camera mounted on Liverpool Telescope primarily designed to obtain high time-resolution light curves transiting extrasolar planets for purpose transit timing. A full and partial WASP-3 presented, Markov-Chain Monte Carlo analysis is used update parameters discovery paper. This in planetary radius RJ therefore density , consistent with previous results. The inclination deg, agreement (but significant improvement precision)...