Winston Sweatman

Dr. Winston Sweatman

orcid

Research Focus & Metrics

Academic Career Length

21Years (2006-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 August 2012 in The Astrophysical Journal
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Journal Article
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JYJ. C. Yee
J. C. Yee
YSY. Shvartzvald
Y. Shvartzvald
AGA. Gal-Yam
A. Gal-Yam
IBI. A. Bond
I. A. Bond
AUA. Udalski
A. Udalski
TCthe μFUN Collaboration
the μFUN Collaboration

2 February 2010 in The Astrophysical Journal
Verified
Journal Article
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TST. Sumi
T. Sumi
DBD. P. Bennett
D. P. Bennett
IBI. A. Bond
I. A. Bond
AUA. Udalski
A. Udalski
VBV. Batista
V. Batista
TCThe μFUN Collaboration
The μFUN Collaboration
We present the discovery of a Neptune-mass planet OGLE-2007-BLG-368Lb with a planet-star mass ratio of q=[9.5 +/- 2.1] x 10^{-5} via gravitational microlensing. The planetary deviation was detected in real-time thanks to the high cadence of the MOA survey, real-time light curve monitoring and intensive follow-up observations. A Bayesian analysis returns the stellar mass and distance at M_l = 0.64_{-0.26}^{+0.21} M_\sun and D_l = 5.9_{-1.4}^{+0.9} kpc, respectively, so the mass and separation of the planet are M_p = 20_{-8}^{+7} M_\oplus and a = 3.3_{-0.8}^{+1.4} AU, respectively. This discovery adds another cold Neptune-mass planet to the planetary sample discovered by microlensing, which now comprise four cold Neptune/Super-Earths, five gas giant planets, and another sub-Saturn mass planet whose nature is unclear. The discovery of these ten cold exoplanets by the microlensing method implies that the mass ratio function of cold exoplanets scales as dN_{\rm pl}/d\log q \propto q^{-0.7 +/- 0.2} with a 95% confidence level upper limit of n < -0.35 (where dN_{\rm pl}/d\log q \propto q^n). As microlensing is most sensitive to planets beyond the snow-line, this implies that Neptune-mass planets are at least three times more common than Jupiters in this region at the 95% confidence level.

12 April 2011 in Astronomy & Astrophysics
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VBVictor S Batista
Victor S Batista
AGAndrew Gould
Andrew Gould
SDS Dieters
S Dieters
SDSubo Dong
Subo Dong
IBI A Bond
I A Bond
RSR A Street
R A Street
Aims. We report the discovery of a planet with a high planet-to-star mass ratio in the microlensing event MOA-2009-BLG-387, which exhibited pronounced deviations over a 12-day interval, one of the longest for any planetary event. The host is an M dwarf, with a mass in the range 0.07 M ⊙ < M host < 0.49 M ⊙ at 90% confidence. The planet-star mass ratio q = 0.0132 ± 0.003 has been measured extremely well, so at the best-estimated host mass, the planet mass is m p = 2.6 Jupiter masses for the median host mass, M = 0.19 M ⊙.Methods. The host mass is determined from two “higher order” microlensing parameters. One of these, the angular Einstein radius θ E = 0.31 ± 0.03 mas has been accurately measured, but the other (the microlens parallax π E, which is due to the Earth’s orbital motion) is highly degenerate with the orbital motion of the planet. We statistically resolve the degeneracy between Earth and planet orbital effects by imposing priors from a Galactic model that specifies the positions and velocities of lenses and sources and a Kepler model of orbits.Results. The 90% confidence intervals for the distance, semi-major axis, and period of the planet are 3.5 kpc < D L < 7.9 kpc, 1.1 AU < a < 2.7 AU, and 3.8 yr < P < 7.6 yr, respectively.

4 June 2009 in The Astrophysical Journal
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AGA. Gould
A. Gould
AUA. Udalski
A. Udalski
BMB. Monard
B. Monard
KHK. Horne
K. Horne
SDSubo Dong
Subo Dong
TCThe PLANET Collaboration
The PLANET Collaboration

12 November 2013 in The Astrophysical Journal
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Journal Article
Closed access
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TST. Sumi
T. Sumi
DBD. P. Bennett
D. P. Bennett
IBI. A. Bond
I. A. Bond
FAF. Abe
F. Abe
CBC. S. Botzler
C. S. Botzler
TCThe Moa Collaboratoin
The Moa Collaboratoin

9 April 2024 in Proceedings of the National Academy of Sciences
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Journal Article
Open access
PMPaulo Mateus Martins
Paulo Mateus Martins
MAMarti J. Anderson
Marti J. Anderson
WSWinston Sweatman
Winston Sweatman
APAndrew J. Punnett
Andrew J. Punnett
Changes in climate can alter environmental conditions faster than most species can adapt. A prediction under a warming climate is that species will shift their distributions poleward through time. While many studies focus on range shifts, latitudinal shifts in species’ optima can occur without detectable changes in their range. We quantified shifts in latitudinal optima for 209 North American bird species over the last 55 y. The latitudinal optimum ( m ) for each species in each year was estimated using a bespoke flexible non-linear zero-inflated model of abundance vs. latitude, and the annual shift in m through time was quantified. One-third (70) of the bird species showed a significant shift in their optimum. Overall, mean peak abundances of North American birds have shifted northward, on average, at a rate of 1.5 km per year (±0.58 SE), corresponding to a total distance moved of 82.5 km (±31.9 SE) over the last 55 y. Stronger poleward shifts at the continental scale were linked to key species’ traits, including thermal optimum, habitat specialization, and territoriality. Shifts in the western region were larger and less variable than in the eastern region, and they were linked to species’ thermal optimum, habitat density preference, and habitat specialization. Individual species’ latitudinal shifts were most strongly linked to their estimated thermal optimum, clearly indicating a climate-driven response. Displacement of species from their historically optimal realized niches can have dramatic ecological consequences. Effective conservation must consider within-range abundance shifts. Areas currently deemed “optimal” are unlikely to remain so.