9 research outputs found
The Transit Light Curve Project. V. System Parameters and Stellar Rotation Period of HD 189733
We present photometry of HD 189733 during eight transits of its close-in
giant planet, and out-of-transit photometry spanning two years. Using the
transit photometry, we determine the stellar and planetary radii and the
photometric ephemeris. Outside of transits, there are quasiperiodic flux
variations with a 13.4 day period that we attribute to stellar rotation. In
combination with previous results, we derive upper limits on the orbital
eccentricity, and on the true angle between the stellar rotation axis and
planetary orbit (as opposed to the angle between the projections of those axes
on the sky).Comment: Accepted for publication in AJ [21 pages]; minor change
TrES-2: The First Transiting Planet in the Kepler Field
We announce the discovery of the second transiting hot Jupiter discovered by
the Trans-atlantic Exoplanet Survey. The planet, which we dub TrES-2, orbits
the nearby star GSC 03549-02811 every 2.47063 days. From high-resolution
spectra, we determine that the star has T_eff = 5960 +/- 100 K and log(g) = 4.4
+/- 0.2, implying a spectral type of G0V and a mass of 1.08 +0.11/-0.05 M_sun.
High-precision radial-velocity measurements confirm a sinusoidal variation with
the period and phase predicted by the photometry, and rule out the presence of
line-bisector variations that would indicate that the spectroscopic orbit is
spurious. We estimate a planetary mass of 1.28 +0.09/-0.04 M_Jup. We model B,
r, R, and I photometric timeseries of the 1.4%-deep transits and find a
planetary radius of 1.24 +0.09/-0.06 R_Jup. This planet lies within the field
of view of the NASA Kepler mission, ensuring that hundreds of upcoming transits
will be monitored with exquisite precision and permitting a host of
unprecedented investigations.Comment: Accepted for publication in ApJL. 15 pages, 2 figure
Measurement of the Spin-Orbit Alignment in the Exoplanetary System HD 189733
We present spectroscopy of a transit of the exoplanet HD 189733b. By modeling
the Rossiter-McLaughlin effect (the anomalous Doppler shift due to the partial
eclipse of the rotating stellar surface), we find the angle between the sky
projections of the stellar spin axis and orbit normal to be lambda = -1.4 +/-
1.1 deg. This is the third case of a ``hot Jupiter'' for which lambda has been
measured. In all three cases lambda is small, ruling out random orientations
with 99.96% confidence, and suggesting that the inward migration of hot
Jupiters generally preserves spin-orbit alignment.Comment: ApJ Letters, in pres
CfA3: 185 Type Ia Supernova Light Curves from the CfA
We present multi-band photometry of 185 type-Ia supernovae (SN Ia), with over
11500 observations. These were acquired between 2001 and 2008 at the F. L.
Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics (CfA).
This sample contains the largest number of homogeneously-observed and reduced
nearby SN Ia (z < 0.08) published to date. It more than doubles the nearby
sample, bringing SN Ia cosmology to the point where systematic uncertainties
dominate. Our natural system photometry has a precision of 0.02 mag or better
in BVRIr'i' and roughly 0.04 mag in U for points brighter than 17.5 mag. We
also estimate a systematic uncertainty of 0.03 mag in our SN Ia standard system
BVRIr'i' photometry and 0.07 mag for U. Comparisons of our standard system
photometry with published SN Ia light curves and comparison stars, where
available for the same SN, reveal agreement at the level of a few hundredths
mag in most cases. We find that 1991bg-like SN Ia are sufficiently distinct
from other SN Ia in their color and light-curve-shape/luminosity relation that
they should be treated separately in light-curve/distance fitter training
samples. The CfA3 sample will contribute to the development of better
light-curve/distance fitters, particularly in the few dozen cases where
near-infrared photometry has been obtained and, together, can help disentangle
host-galaxy reddening from intrinsic supernova color, reducing the systematic
uncertainty in SN Ia distances due to dust.Comment: Accepted to the Astrophysical Journal. Minor changes from last
version. Light curves, comparison star photometry, and passband tables are
available at http://www.cfa.harvard.edu/supernova/CfA3
The Transit Light Curve Project. V. System Parameters and Stellar Rotation Period of HD 189733
We present photometry of HD 189733 during eight transits of its close-in giant planet, and out-of-transit photometry spanning 2 yr. Using the transit photometry, we determine the stellar and planetary radii and the photometric ephemeris. Outside of transits, there are quasi-periodic flux variations with a 13.4 day period that we attribute to stellar rotation. In combination with previous results, we derive upper limits on the orbital eccentricity and on the true angle between the stellar rotation axis and planetary orbit (as opposed to the angle between the projections of those axes on the sky)
� 2006. The American Astronomical Society. All rights reserved. Printed in U.S.A. MEASUREMENT OF THE SPIN-ORBIT ALIGNMENT IN THE EXOPLANETARY SYSTEM HD 189733 1
We present spectroscopy of a transit of the exoplanet HD 189733b. By modeling the Rossiter-McLaughlin effect (the anomalous Doppler shift due to the partial eclipse of the rotating stellar surface), we find the angle between the sky projections of the stellar spin axis and orbit normal to be l p �1�.4 � 1�.1. This is the third case of a “hot Jupiter ” for which l has been measured. In all three cases l is small, ruling out random orientations with 99.96% confidence, and suggesting that the inward migration of hot Jupiters generally preserves spin-orbit alignment