ORCID Profile
0000-0003-3096-4161
Current Organisation
Dartmouth College
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Publisher: American Astronomical Society
Date: 20-03-2018
Publisher: American Astronomical Society
Date: 30-11-2015
Publisher: American Astronomical Society
Date: 04-09-2018
Publisher: American Astronomical Society
Date: 24-05-2019
Publisher: American Association for the Advancement of Science (AAAS)
Date: 15-02-2008
Abstract: Searches for extrasolar planets have uncovered an astonishing ersity of planetary systems, yet the frequency of solar system analogs remains unknown. The gravitational microlensing planet search method is potentially sensitive to multiple-planet systems containing analogs of all the solar system planets except Mercury. We report the detection of a multiple-planet system with microlensing. We identify two planets with masses of ∼0.71 and ∼0.27 times the mass of Jupiter and orbital separations of ∼2.3 and ∼4.6 astronomical units orbiting a primary star of mass ∼0.50 solar mass at a distance of ∼1.5 kiloparsecs. This system resembles a scaled version of our solar system in that the mass ratio, separation ratio, and equilibrium temperatures of the planets are similar to those of Jupiter and Saturn. These planets could not have been detected with other techniques their discovery from only six confirmed microlensing planet detections suggests that solar system analogs may be common.
Publisher: Wiley
Date: 12-03-2019
DOI: 10.1111/MAM.12151
Publisher: American Astronomical Society
Date: 02-2021
Abstract: We performed the largest and most homogeneous spectroscopic survey of field RR Lyraes (RRLs). We secured ≈6300 high-resolution (HR, R ∼ 35,000) spectra for 143 RRLs (111 fundamental, RRab 32 first-overtone, RRc). The atmospheric parameters were estimated by using the traditional approach and the iron abundances were measured by using an LTE line analysis. The resulting iron distribution shows a well-defined metal-rich tail approaching solar iron abundance. This suggests that field RRLs experienced a complex chemical enrichment in the early halo formation. We used these data to develop a new calibration of the Δ S method. This diagnostic, based on the equivalent widths of Ca ii K and three Balmer (H δ , γ , β ) lines, traces the metallicity of RRLs. For the first time, the new empirical calibration: (i) includes spectra collected over the entire pulsation cycle (ii) includes RRc variables (iii) relies on spectroscopic calibrators covering more than three dex in iron abundance and (iv) provides independent calibrations based on one/two/three Balmer lines. The new calibrations were applied to a data set of both SEGUE-SDSS and degraded HR spectra totalling 6451 low-resolution ( R ∼ 2000) spectra for 5001 RRLs (3439 RRab, 1562 RRc). This resulted in an iron distribution with a median η = −1.55 ± 0.01 and σ = 0.51 dex, in good agreement with literature values. We also found that RRc are 0.10 dex more metal-poor than RRab variables, and have a distribution with a smoother metal-poor tail. This finding supports theoretical prescriptions suggesting a steady decrease in the RRc number when moving from metal-poor to metal-rich stellar environments.
Publisher: American Astronomical Society
Date: 03-2023
Abstract: We present new empirical infrared period–luminosity–metallicity (PLZ) and period–Wesenheit–metallicity (PWZ) relations for RR Lyae based on the latest Gaia Early Data Release 3 (EDR3) parallaxes. The relations are provided in the Wide-field Infrared Survey Explorer (WISE) W1 and W2 bands, as well as in the W(W1, V − W1) and W(W2, V − W2) Wesenheit magnitudes. The relations are calibrated using a very large s le of Galactic halo field RR Lyrae stars with homogeneous spectroscopic [Fe/H] abundances (over 1000 stars in the W1 band), covering a broad range of metallicities (−2.5 ≲ [Fe/H] ≲ 0.0). We test the performance of our PLZ and PWZ relations by determining the distance moduli of both galactic and extragalactic stellar associations: the Sculptor dwarf spheroidal galaxy in the Local Group (finding μ ¯ 0 = 19.47 ± 0.06 ), the Galactic globular clusters M4 ( μ ¯ 0 = 11.16 ± 0.05 ), and the Reticulum globular cluster in the Large Magellanic Cloud ( μ ¯ 0 = 18.23 ± 0.06 ). The distance moduli determined through all our relations are internally self-consistent (within ≲0.05 mag) but are systematically smaller (by ∼2–3 σ ) than previous literature measurements taken from a variety of methods/anchors. However, a comparison with similar recent RR Lyrae empirical relations anchored with EDR3 likewise shows, to varying extents, a systematically smaller distance modulus for PLZ/PWZ RR Lyrae relations.
Publisher: American Astronomical Society
Date: 26-03-2010
Location: United States of America
No related grants have been discovered for Brian Chaboyer.