53,149 research outputs found
Rossiter-McLaughlin Observations of 55 Cnc e
We present Rossiter-McLaughlin observations of the transiting super-Earth 55
Cnc e collected during six transit events between January 2012 and November
2013 with HARPS and HARPS-N. We detect no radial-velocity signal above 35 cm/s
(3-sigma) and confine the stellar v sin i to 0.2 +/- 0.5 km/s. The star appears
to be a very slow rotator, producing a very low amplitude Rossiter-McLaughlin
effect. Given such a low amplitude, the Rossiter-McLaughlin effect of 55 Cnc e
is undetected in our data, and any spin-orbit angle of the system remains
possible. We also performed Doppler tomography and reach a similar conclusion.
Our results offer a glimpse of the capacity of future instrumentation to study
low amplitude Rossiter-McLaughlin effects produced by super-Earths.Comment: Accepted for publication in ApJ Letter
The Rossiter-McLaughlin effect in Exoplanet Research
The Rossiter-McLaughlin effect occurs during a planet's transit. It provides
the main means of measuring the sky-projected spin-orbit angle between a
planet's orbital plane, and its host star's equatorial plane. Observing the
Rossiter-McLaughlin effect is now a near routine procedure. It is an important
element in the orbital characterisation of transiting exoplanets. Measurements
of the spin-orbit angle have revealed a surprising diversity, far from the
placid, Kantian and Laplacian ideals, whereby planets form, and remain, on
orbital planes coincident with their star's equator. This chapter will review a
short history of the Rossiter-McLaughlin effect, how it is modelled, and will
summarise the current state of the field before describing other uses for a
spectroscopic transit, and alternative methods of measuring the spin-orbit
angle.Comment: Review to appear as a chapter in the "Handbook of Exoplanets", ed. H.
Deeg & J.A. Belmont
Prospects for detecting the Rossiter-McLaughlin effect of Earth-like planets: the test case of TRAPPIST-1b and c
The Rossiter-McLaughlin effect is the principal method of determining the
sky-projected spin--orbit angle () of transiting planets. Taking the
example of the recently discovered TRAPPIST-1 system, we explore how ultracool
dwarfs facilitate the measurement of the spin--orbit angle for Earth-sized
planets by creating an effect that can be an order of magnitude more ample than
the Doppler reflex motion caused by the planet if the star is undergoing rapid
rotation. In TRAPPIST-1's case we expect the semi-amplitudes of the
Rossiter-McLaughlin effect to be m/s for the known transiting planets.
Accounting for stellar jitter expected for ultracool dwarfs, instrumental
noise, and assuming radial velocity precisions both demonstrated and
anticipated for upcoming near-infrared spectrographs, we quantify the
observational effort required to measure the planets' masses and spin--orbit
angles. We conclude that if the planetary system is well-aligned then
can be measured to a precision of if the spectrograph is
stable at the level of 2 m/s. We also investigate the measure of , the mutual inclination, when multiple transiting planets are present in
the system. Lastly, we note that the rapid rotation rate of many late M-dwarfs
will amplify the Rossiter-McLaughlin signal to the point where variations in
the chromatic Rossiter-McLaughlin effect from atmospheric absorbers should be
detectable.Comment: 11 pages, 4 figures. Accepted to MNRAS. Comments welcom
Can stellar activity make a planet seem misaligned?
Several studies have shown that the occultation of stellar active regions by
the transiting planet can generate anomalies in the high-precision transit
light curves, and these anomalies may lead to an inaccurate estimate of the
planetary parameters (e.g., the planet radius). Since the physics and geometry
behind the transit light curve and the Rossiter- McLaughlin effect
(spectroscopic transit) are the same, the Rossiter-McLaughlin observations are
expected to be affected by the occultation of stellar active regions in a
similar way. In this paper we perform a fundamental test on the spin-orbit
angles as derived by Rossiter-McLaughlin measurements, and we examine the
impact of the occultation of stellar active regions by the transiting planet on
the spin-orbit angle estimations. Our results show that the inaccurate
estimation on the spin-orbit angle due to stellar activity can be quite
significant (up to 30 degrees), particularly for the edge-on, aligned, and
small transiting planets. Therefore, our results suggest that the aligned
transiting planets are the ones that can be easily misinterpreted as misaligned
owing to the stellar activity. In other words, the biases introduced by
ignoring stellar activity are unlikely to be the culprit for the highly
misaligned systems.Comment: 8 pages, 8 figures, accepted for publication in Astronomy &
Astrophysic
Discovery and Rossiter-McLaughlin Effect of Exoplanet Kepler-8b
We report the discovery and the Rossiter-McLaughlin effect of Kepler-8b, a
transiting planet identified by the NASA Kepler Mission. Kepler photometry and
Keck-HIRES radial velocities yield the radius and mass of the planet around
this F8IV subgiant host star. The planet has a radius RP = 1.419 RJ and a mass,
MP = 0.60 MJ, yielding a density of 0.26 g cm^-3, among the lowest density
planets known. The orbital period is P = 3.523 days and orbital semima jor axis
is 0.0483+0.0006/-0.0012 AU. The star has a large rotational v sin i of 10.5
+/- 0.7 km s^-1 and is relatively faint (V = 13.89 mag), both properties
deleterious to precise Doppler measurements. The velocities are indeed noisy,
with scatter of 30 m s^-1, but exhibit a period and phase consistent with the
planet implied by the photometry. We securely detect the Rossiter-McLaughlin
effect, confirming the planet's existence and establishing its orbit as
prograde. We measure an inclination between the projected planetary orbital
axis and the projected stellar rotation axis of lambda = -26.9 +/- 4.6 deg,
indicating a moderate inclination of the planetary orbit. Rossiter-McLaughlin
measurements of a large sample of transiting planets from Kepler will provide a
statistically robust measure of the true distribution of spin-orbit
orientations for hot jupiters in general.Comment: 26 pages, 8 figures, 2 tables; In preparation for submission to the
Astrophysical Journa
The Doppler Shadow of WASP-3b: A tomographic analysis of Rossiter-McLaughlin observations
Hot-Jupiter planets must form at large separations from their host stars
where the temperatures are cool enough for their cores to condense. They then
migrate inwards to their current observed orbital separations. Different
theories of how this migration occurs lead to varying distributions of orbital
eccentricity and the alignment between the rotation axis of the star and the
orbital axis of the planet. The spin-orbit alignment of a transiting system is
revealed via the Rossiter-McLaughlin effect, which is the anomaly present in
the radial velocity measurements of the rotating star during transit due to the
planet blocking some of the starlight. In this paper we aim to measure the
spin-orbit alignment of the WASP-3 system via a new way of analysing the
Rossiter-McLaughlin observations. We apply a new tomographic method for
analysing the time variable asymmetry of stellar line profiles caused by the
Rossiter-McLaughlin effect. This new method eliminates the systematic error
inherent in previous methods used to analyse the effect. We find a value for
the projected stellar spin rate of v sin i = 13.9 \pm 0.03 km/s which is in
agreement with previous measurements but has a much higher precision. The
system is found to be well aligned which favours an evolutionary history for
WASP-3b involving migration through tidal interactions with a protoplanetary
disc. Using gyrochronology we estimate the age of the star to be ~300 Myr with
an upper limit of 2 Gyr from comparison with isochrones.Comment: Accepted for publication in A&A, 8 pages, 4 figures, 2 table
Detecting the spin-orbit misalignment of the super-Earth 55 Cnc e
We present time-resolved spectroscopy of transits of the super-Earth 55 Cnc e
using HARPS-N observations. We devised an empirical correction for the "color
effect" affecting the radial velocity residuals from the Keplerian fit, which
significantly improves their dispersion with respect to the HARPS-N pipeline
standard data-reduction. Using our correction, we were able to detect the
smallest Rossiter-McLaughlin anomaly amplitude of an exoplanet so far (~60
cm/s). The super-Earth 55 Cnc e is also the smallest exoplanet with a
Rossiter-McLaughlin anomaly detection. We measured the sky-projected obliquity
lambda = 72.4 (+12.7 -11.5 deg), indicating that the planet orbit is prograde,
highly misaligned and nearly polar compared to the stellar equator. The entire
55 Cancri system may have been highly tilted by the presence of a stellar
companion.Comment: 11 pages, 7 figure
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