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Register a new userA search for starlight reflected from upsilon Ands innermost planet
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Added by
Andrew Collier Cameron
Publication date
2001
fields
Physics
and research's language is
English
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In data from three clear nights of a WHT/UES run in 2000 Oct/Nov, and using improved Doppler tomographic signal-analysis techniques, we have carried out a deep search for starlight reflected from the innermost of upsilon Ands three planets. We place upper limits on the planets radius R_p as functions of its projected orbital velocity K_p ~ 139 sin i km/sec for various assumptions about the wavelength-dependent geometric albedo spectrum p(lambda) of its atmosphere. For a grey albedo p we find R_p sqrt{p} < 0.98 R_Jup with 0.1 percent false-alarm probability (4-sigma). For a Sudarsky et al (2000) Class V model atmosphere, the mean albedo in our 380-676 nm bandpass is <p> ~ 0.42, requiring R_p < 1.51 R_Jup, while an (isolated) Class IV model with <p> ~ 0.19 requires R_p < 2.23 R_Jup. The stars v sin{i} ~ 10 km/sec and estimated rotation period P_{rot} ~ 10 d suggest a high orbital inclination i ~ 70-80 degrees. We also develop methods for assessing the false-alarm probabilities of faint candidate detections, and for extracting information about the albedo spectrum and other planetary parameters from faint reflected-light signals.
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Aims. We attempt to detect starlight reflected from a hot Jupiter, orbiting the main-sequence star HD 75289Ab. We report a revised analysis of observations of this planetary system presented previously by another research group. Methods. We analyse high-precision, high-resolution spectra, collected over four nights using UVES at the VLT/UT2, by way of data synthesis. We try to interpret our data using different atmospheric models for hot Jupiters. Results. We do not find any evidence for reflected light, and, therefore, establish revised upper limits to the planet-to-star flux ratio at the 99.9% significance level. At high orbital inclinations, where the best sensitivity is attained, we can limit the relative reflected radiation to be less than e = 6.7 x 10-5 assuming a grey albedo, and e = 8.3 x 10-5 assuming an Class IV function, respectively. This implies a geometric albedo smaller than p = 0.46 and p = 0.57, for the grey albedo and the Class IV albedo shape, respectively, assuming a planetary radius of 1.2 RJup.
Using improved doppler tomographic signal-analysis techniques we have carried out a deep search for starlight reflected from the giant planet orbiting the star Tau Bootis. We combined echelle spectra secured at the 4.2 m William Herschel telescope in 1998 and 1999 (which yielded a tentative detection of a reflected starlight component from the orbiting companion) with new data obtained in 2000 (which failed to confirm the detection). The combined dataset comprises 893 high resolution spectra with a total integration time of 75 hr 32 min spanning 17 nights. We establish an upper limit on the planets geometric albedo p<0.39 (at the 99.9 % significance level) at the most probable orbital inclination i=36 degrees, assuming a grey albedo, a Venus-like phase function and a planetary radius R_p=1.2 R_Jup. We are able to rule out some combinations of the predicted planetary radius and atmospheric albedo models with high, reflective cloud decks. Although a weak candidate signal appears near to the most probable radial velocity amplitude, its statistical significance is insufficient for us to claim a detection with any confidence.
Doppler spectroscopy has detected 136 planets around nearby stars. A major puzzle is why their orbits are highly eccentric, while all planets in our Solar System are on nearly circular orbits, as expected if they formed by accretion processes in a protostellar disk. Several mechanisms have been proposed to generate large eccentricities after planet formation, but so far there has been little observational evidence to support any particular one. Here we report that the current orbital configuration of the three giant planets around Upsilon Andromedae (ups And) provides evidence for a close dynamical interaction with another planet, now lost from the system. The planets started on nearly circular orbits, but chaotic evolution caused the outer planet (ups And d) to be perturbed suddenly into a higher-eccentricity orbit. The coupled evolution of the system then causes slow periodic variations in the eccentricity of the middle planet (ups And c). Indeed, we show that ups And c periodically returns to a very nearly circular state every 9000 years. Our analysis shows that strong planet-planet scattering, one of several mechanisms previously discussed for increasing orbital eccentricities, must have operated in this system.
We search for the $J^{PC}=0^{--}$ and $1^{+-}$ light tetraquark states with masses up to 2.46~GeV/$c^2$ in $Upsilon(1S)$ and $Upsilon(2S)$ decays with data samples of $(102pm 2)$ million and $(158pm 4)$ million events, respectively, collected with the Belle detector. No significant signals are observed in any of the studied production modes, and 90% credibility level (C.L.) upper limits on their branching fractions in $Upsilon(1S)$ and $Upsilon(2S)$ decays are obtained. The inclusive branching fractions of the $Upsilon(1S)$ and $Upsilon(2S)$ decays into final states with $f_1(1285)$ are measured to be ${cal B}(Upsilon(1S)to f_1(1285)+anything)=(46pm28({rm stat.})pm13({rm syst.}))times 10^{-4}$ and ${cal B}(Upsilon(2S)to f_1(1285)+anything)=(22pm15({rm stat.})pm6.3({rm syst.}))times 10^{-4}$. The measured $chi_{b2} to J/psi + anything$ branching fraction is measured to be $(1.50pm0.34({rm stat.})pm0.22({rm syst.}))times 10^{-3}$, and 90% C.L. upper limits for the $chi_{b0,b1} to J/psi + anything$ branching fractions are found to be $2.3times 10^{-3}$ and $1.1times 10^{-3}$, respectively. For ${cal B}(chi_{b1} to omega + anything)$, the branching fraction is measured to be $(4.9pm1.3({rm stat.})pm0.6({rm syst.}))times 10^{-2}$. %($<3.68times 10^{-2}$ at 90% C.L.). All results reported here are the first measurements for these modes.
We report the first search for the $J^{PC}=0^{--}$ glueball in $Upsilon(1S)$ and $Upsilon(2S)$ decays with data samples of $(102pm2)$ million and $(158pm4)$ million events, respectively, collected with the Belle detector. No significant signals are observed in any of the proposed production modes, and the 90% credibility level upper limits on their branching fractions in $Upsilon(1S)$ and $Upsilon(2S)$ decays are obtained. The inclusive branching fractions of the $Upsilon(1S)$ and $Upsilon(2S)$ decays into final states with a $chi_{c1}$ are measured to be $BR(Upsilon(1S)to chi_{c1}+ anything) = (1.90pm 0.43(stat.)pm 0.14(syst.))times 10^{-4}$ with an improved precision over prior measurements and $BR(Upsilon(2S)to chi_{c1}+ anything) = (2.24pm 0.44(stat.)pm 0.20(syst.))times 10^{-4}$ for the first time.
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