627 research outputs found
Exoplanetary Transit Constraints Based Upon Secondary Eclipse Observations
Transiting extrasolar planets provide an opportunity to study the mass-radius
relation of planets as well as their internal structure. The existence of a
secondary eclipse enables further study of the thermal properties of the the
planet by observing at infrared wavelengths. The probability of an observable
secondary eclipse depends upon the orbital parameters of the planet,
particularly eccentricity and argument of periastron. Here we provide
analytical expressions for these probabilities, investigate their properties,
and calculate their values for the known extrasolar planets. We furthermore
quantitatively discuss constraints on existence and observability of primary
transits if a secondary eclipse is observed. Finally, we calculate the
a-posteriori transit probabilities of the known extrasolar planets, and we
present several case studies in which orbital constraints resulting from the
presence of a secondary eclipse may be applied in observing campaigns.Comment: 7 pages, 5 figures, 1 table; accepted for publication in PAS
Constraints on Secondary Eclipse Probabilities of Long-Period Exoplanets from Orbital Elements
Long-period transiting exoplanets provide an opportunity to study the
mass-radius relation and internal structure of extrasolar planets. Their
studies grant insights into planetary evolution akin to the Solar System
planets, which, in contrast to hot Jupiters, are not constantly exposed to the
intense radiation of their parent stars. Observations of secondary eclipses
allow investigations of exoplanet temperatures and large-scale exo-atmospheric
properties. In this short paper, we elaborate on, and calculate, probabilities
of secondary eclipses for given orbital parameters, both in the presence and
absence of detected primary transits, and tabulate these values for the forty
planets with the highest primary transit probabilities.Comment: 3 pages, 1 figure, 1 table; to appear in ASP Conf. Proceedings:
"Pathways Towards Habitable Planets" 2009, Barcelona, Spain (eds.: D. Gelino,
V. Coude du Foresto, I. Ribas
Observational Window Functions in Planet Transit Surveys
The probability that an existing planetary transit is detectable in one's
data is sensitively dependent upon the window function of the observations. We
quantitatively characterize and provide visualizations of the dependence of
this probability as a function of orbital period upon several observing
strategy and astrophysical parameters, such as length of observing run,
observing cadence, length of night, transit duration and depth, and the minimum
number of sampled transits. The ability to detect a transit is directly related
to the intrinsic noise of the observations. In our simulations of observational
window functions, we explicitly address non-correlated (gaussian or white)
noise and correlated (red) noise and discuss how these two noise components
affect transit detectability in fundamentally different manners, especially for
long periods and/or small transit depths. We furthermore discuss the
consequence of competing effects on transit detectability, elaborate on
measures of observing strategies, and examine the projected efficiency of
different transit survey scenarios with respect to certain regions of parameter
space.Comment: 16 pages, 11 figures, 8 tables; accepted for publication in Ap
Refining Exoplanet Ephemerides and Transit Observing Strategies
Transiting planet discoveries have yielded a plethora of information
regarding the internal structure and atmospheres of extra-solar planets. These
discoveries have been restricted to the low-periastron distance regime due to
the bias inherent in the geometric transit probability. Monitoring known radial
velocity planets at predicted transit times is a proven method of detecting
transits, and presents an avenue through which to explore the mass-radius
relationship of exoplanets in new regions of period/periastron space. Here we
describe transit window calculations for known radial velocity planets,
techniques for refining their transit ephemerides, target selection criteria,
and observational methods for obtaining maximum coverage of transit windows.
These methods are currently being implemented by the Transit Ephemeris
Refinement and Monitoring Survey (TERMS).Comment: 8 pages, 6 figures, accepted for publication in PAS
System Geometries and Transit / Eclipse Probabilities
Transiting exoplanets provide access to data to study the mass-radius
relation and internal structure of extrasolar planets. Long-period transiting
planets allow insight into planetary environments similar to the Solar System
where, in contrast to hot Jupiters, planets are not constantly exposed to the
intense radiation of their parent stars. Observations of secondary eclipses
additionally permit studies of exoplanet temperatures and large-scale
exo-atmospheric properties. We show how transit and eclipse probabilities are
related to planet-star system geometries, particularly for long-period,
eccentric orbits. The resulting target selection and observational strategies
represent the principal ingredients of our photometric survey of known
radial-velocity planets with the aim of detecting transit signatures (TERMS).Comment: 3 pages, 2 figures. Comments: To appear in the ASP Conference
Proceedings: Detection and Dynamics of Transiting Exoplanets; Proceedings of
Haute Provence Observatory Colloquium (23-27 August 2010); Edited by F.
Bouchy, R. F. Diaz, and C. Mouto
Transit Detection of Radial Velocity Planets
The orbital parameters of extra-solar planets have a significant impact on
the probability that the planet will transit the host star. This was recently
demonstrated by the transit detection of HD 17156b whose favourable
eccentricity and argument of periastron dramatically increased its transit
likelihood. We present a study which provides a quantitative analysis of how
these two orbital parameters effect the geometric transit probability as a
function of period. Further, we apply these results to known radial velocity
planets and show that there are unexpectedly high transit probabilities for
planets at relatively long periods. For a photometric monitoring campaign which
aims to determine if the planet indeed transits, we calculate the significance
of a null result and the subsequent constraints that may be applied to orbital
parameters.Comment: To appear in the Proceedings of the 253rd IAU Symposium: "Transiting
Planets", May 2008, Cambridge, MA. 4 pages, 4 figure
Constraining Orbital Parameters Through Planetary Transit Monitoring
The orbital parameters of extra-solar planets have a significant impact on
the probability that the planet will transit the host star. This was recently
demonstrated by the transit detection of HD 17156b whose favourable
eccentricity and argument of periastron dramatically increased its transit
likelihood. We present a study which provides a quantitative analysis of how
these two orbital parameters affect the geometric transit probability as a
function of period. Further, we apply these results to known radial velocity
planets and show that there are unexpectedly high transit probabilities for
planets at relatively long periods. For a photometric monitoring campaign which
aims to determine if the planet indeed transits, we calculate the expected
transiting planet yield and the significance of a potential null result, as
well as the subsequent constraints that may be applied to orbital parameters.Comment: 7 pages, 9 figures, accepted for publication in Ap
The Discovery of a Spatially-Resolved Supernova Remnant in M31 with Chandra
Chandra observations of M31 allow the first spatially resolved X-ray image of
a supernova remnant (SNR) in an external spiral galaxy. CXOM31 J004327.7+411829
is a slightly elongated ring-shaped object with a diameter of ~11'' (42 pc). In
addition, the X-ray image hints that the chemical composition of the SNR is
spatial dependent. The X-ray spectrum of the SNR can be well fitted with a
Raymond-Smith model or a non-equilibrium ionization model. Depending on the
spectral model, the 0.3-7 keV luminosity is between 3.2x10^36 erg/s and
4.5x10^37 erg/s. The age of the SNR is estimated to be 3210-22300 years and the
number density of ambient gas is ~0.003-0.3 cm^-3. This suggests that the local
interstellar medium around the SNR is low.Comment: 5 pages, 3 figures; accepted for publication in ApJ
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