orbitize! is an open-source, object-oriented software package for fitting the orbits of directly imaged objects. It packages the Orbits for the Impatient (OFTI) algorithm and a parallel-tempered ...Markov Chain Monte Carlo (MCMC) algorithm into a consistent and intuitive Python API. orbitize! makes it easy to run standard astrometric orbit fits; in less than 10 lines of code, users can read in data, perform one fit using OFTI and another using MCMC, and make two publication-ready figures. Extensive pedagogical tutorials, intended to be navigable by both orbit-fitting novices and seasoned experts, are available on our documentation page. We have designed the orbitize! API to be flexible and easy to use/modify for unique cases. orbitize! was designed by members of the exoplanet imaging community to be a central repository for algorithms, techniques, and know-how developed by this community. We intend for it to continue to expand and change as the field progresses and new techniques are developed, and call for community involvement in this process. Complete and up-to-date documentation is available at orbitize.info, and the source code is available at github.com/sblunt/orbitize.
► We construct a steady-state NEO orbital distribution model. ► This model has larger statistics than the previous models. ► We highlight two previously little discussed NEO populations. ► These ...populations are NEAs decoupled from Venus and retrograde NEAs. ► We compute impact rates and impact speeds onto the terrestrial planets.
Canada’s Near-Earth Object Surveillance Satellite (NEOSSat), set to launch in early 2012, will search for and track Near-Earth Objects (NEOs), tuning its search to best detect objects with
a
<
1.0
AU. In order to construct an optimal pointing strategy for NEOSSat, we needed more detailed information in the
a
<
1.0
AU region than the best current model (Bottke, W.F., Morbidelli, A., Jedicke, R., Petit, J.M., Levison, H.F., Michel, P., Metcalfe, T.S. 2002. Icarus 156, 399–433) provides. We present here the NEOSSat-1.0 NEO orbital distribution model with larger statistics that permit finer resolution and less uncertainty, especially in the
a
<
1.0
AU region. We find that Amors
=
30.1
±
0.8%, Apollos
=
63.3
±
0.4%, Atens
=
5.0
±
0.3%, Atiras (0.718
<
Q
<
0.983
AU)
=
1.38
±
0.04%, and Vatiras (0.307
<
Q
<
0.718
AU)
=
0.22
±
0.03% of the steady-state NEO population. Vatiras are a previously undiscussed NEO population clearly defined in our integrations, whose orbits lie completely interior to that of Venus. Our integrations also uncovered the unexpected production of retrograde orbits from main-belt asteroid sources; this retrograde NEA population makes up ≃0.1% of the steady-state NEO population. The relative NEO impact rate onto Mercury, Venus, and Earth, as well as the normalized distribution of impact speeds, was calculated from the NEOSSat-1.0 orbital model under the assumption of a steady-state. The new model predicts a slightly higher Mercury impact flux.
In this paper we search for distant massive companions to known transiting gas giant planets that may have influenced the dynamical evolution of these systems. We present new radial velocity ...observations for a sample of 51 planets obtained using the Keck HIRES instrument, and find statistically significant accelerations in fifteen systems. Six of these systems have no previously reported accelerations in the published literature: HAT-P-10, HAT-P-22, HAT-P-29, HAT-P-32, WASP-10, and XO-2. We combine our radial velocity fits with Keck NIRC2 adaptive optics (AO) imaging data to place constraints on the allowed masses and orbital periods of the companions responsible for the detected accelerations. The estimated masses of the companions range between 1-500 M sub(Jup), with orbital semi-major axes typically between 1-75 AU. A significant majority of the companions detected by our survey are constrained to have minimum masses comparable to or larger than those of the transiting planets in these systems, making them candidates for influencing the orbital evolution of the inner gas giant. We estimate a total occurrence rate of 51% + or - 10% for companions with masses between 1-13 M sub(Jup) and orbital semi-major axes between 1-20 AU in our sample. We find no statistically significant difference between the frequency of companions to transiting planets with misaligned or eccentric orbits and those with well-aligned, circular orbits. We combine our expanded sample of radial velocity measurements with constraints from transit and secondary eclipse observations to provide improved measurements of the physical and orbital characteristics of all of the planets included in our survey.
ABSTRACT Stellar companions can influence the formation and evolution of planetary systems, but there are currently few observational constraints on the properties of planet-hosting binary star ...systems. We search for stellar companions around 77 transiting hot Jupiter systems to explore the statistical properties of this population of companions as compared to field stars of similar spectral type. After correcting for survey incompleteness, we find that of hot Jupiter systems have stellar companions with semimajor axes between 50 and 2000 au. This is 2.9 times larger than the field star companion fraction in this separation range, with a significance of . In the 1-50 au range, only of hot Jupiters host stellar companions, compared to the field star value of , which is a difference. We find that the distribution of mass ratios for stellar companions to hot Jupiter systems peaks at small values and therefore differs from that of field star binaries which tend to be uniformly distributed across all mass ratios. We conclude that either wide separation stellar binaries are more favorable sites for gas giant planet formation at all separations, or that the presence of stellar companions preferentially causes the inward migration of gas giant planets that formed farther out in the disk via dynamical processes such as Kozai-Lidov oscillations. We determine that less than 20% of hot Jupiters have stellar companions capable of inducing Kozai-Lidov oscillations assuming initial semimajor axes between 1 and 5 au, implying that the enhanced companion occurrence is likely correlated with environments where gas giants can form efficiently.
We place the first constraints on the obliquity of a planetary-mass companion outside of the solar system. Our target is the directly imaged system 2MASS J01225093-2439505 (2M0122), which consists of ...a 120 Myr 0.4 M star hosting a 12-27 MJ companion at 50 au. We constrain all three of the system's angular-momentum vectors: how the companion spin axis, the stellar spin axis, and the orbit normal are inclined relative to our line of sight. To accomplish this, we measure projected rotation rates (v sin i) for both the star and the companion using new near-infrared high-resolution spectra with NIRSPEC at Keck Observatory. We combine these with a new stellar photometric rotation period from TESS and a published companion rotation period from Hubble Space Telescope to obtain spin-axis inclinations for both objects. We also fitted multiple epochs of astrometry, including a new observation with NIRC2/Keck, to measure 2M0122b's orbital inclination. The three line-of-sight inclinations place limits on the true de-projected companion obliquity and stellar obliquity. We find that while the stellar obliquity marginally prefers alignment, the companion obliquity tentatively favors misalignment. We evaluate possible origin scenarios. While collisions, secular spin-orbit resonances, and Kozai-Lidov oscillations are unlikely, formation by gravitational instability in a gravito-turbulent disk-the scenario favored for brown dwarf companions to stars-appears promising.
The NIRC2 vortex coronagraph is an instrument on Keck II designed to directly image exoplanets and circumstellar disks at mid-infrared bands L′ (3.4-4.1 m) and Ms (4.55-4.8 m). We analyze imaging ...data and corresponding adaptive optics telemetry, observing conditions, and other metadata over a three-year time period to characterize the performance of the instrument and predict the detection limits of future observations. We systematically process images from 359 observations of 304 unique stars to subtract residual starlight (i.e., the coronagraphic point-spread function) of the target star using two methods: angular differential imaging (ADI) and reference star differential imaging (RDI). We find that for the typical parallactic angle (PA) rotation of our data set (∼10°), RDI provides gains over ADI for angular separations smaller than 0 25. Furthermore, we find a power-law relation between the angular separation from the host star and the minimum PA rotation required for ADI to outperform RDI, with a power-law index of −1.18 0.08. Finally, we use random forest models to estimate ADI and RDI post-processed detection limits a priori. These models, which we provide publicly on a website, explain 70%-80% of the variance in ADI detection limits and 30%-50% of the variance in RDI detection limits. Averaged over a range of angular separations, our models predict both ADI and RDI contrast to within a factor of 2. These results illuminate important factors in high-contrast imaging observations with the NIRC2 vortex coronagraph, help improve observing strategies, and inform future upgrades to the hardware.
The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) has made 1 deg2, deep, confusion-limited maps at three different bands, centered on the Great Observatories Origins Deep Survey South ...Field. By calculating the covariance of these maps with catalogs of 24 Delta *mm sources from the Far-Infrared Deep Extragalactic Legacy Survey, we have determined that the total submillimeter intensities are 8.60 +/- 0.59, 4.93 +/- 0.34, and 2.27 +/- 0.20 nW m-2 sr-1 at 250, 350, and 500 Delta *mm, respectively. These numbers are more precise than previous estimates of the cosmic infrared background (CIB) and are consistent with 24 Delta *mm-selected galaxies generating the full intensity of the CIB. We find that the fraction of the CIB that originates from sources at z >= 1.2 increases with wavelength, with 60% from high-redshift sources at 500 Delta *mm. At all BLAST wavelengths, the relative intensity of high-z sources is higher for 24 Delta *mm-faint sources than that for 24 Delta *mm-bright sources. Galaxies identified as active galactic nuclei (AGNs) by their Infrared Array Camera colors are 1.6-2.6 times brighter than the average population at 250-500 Delta *mm, consistent with what is found for X-ray-selected AGNs. BzK-selected galaxies are found to be moderately brighter than typical 24 Delta *mm-selected galaxies in the BLAST bands. These data provide high-precision constraints for models of the evolution of the number density and intensity of star-forming galaxies at high redshift.
Submillimetre surveys during the past decade have discovered a population of luminous, high-redshift, dusty starburst galaxies. In the redshift range 1 ≤ z ≤ 4, these massive submillimetre galaxies ...go through a phase characterized by optically obscured star formation at rates several hundred times that in the local Universe. Half of the starlight from this highly energetic process is absorbed and thermally re-radiated by clouds of dust at temperatures near 30 K with spectral energy distributions peaking at 100 m in the rest frame. At 1 ≤ z ≤ 4, the peak is redshifted to wavelengths between 200 and 500 m. The cumulative effect of these galaxies is to yield extragalactic optical and far-infrared backgrounds with approximately equal energy densities. Since the initial detection of the far-infrared background (FIRB), higher-resolution experiments have sought to decompose this integrated radiation into the contributions from individual galaxies. Here we report the results of an extragalactic survey at 250, 350 and 500 m. Combining our results at 500 m with those at 24 m, we determine that all of the FIRB comes from individual galaxies, with galaxies at z ≥ 1.2 accounting for 70% of it. As expected, at the longest wavelengths the signal is dominated by ultraluminous galaxies at z > 1.
We demonstrate dynamical pathways from main-belt asteroid and Centaur orbits to those in co-orbital motion with Jupiter, including the retrograde (inclination i > 90°) state. We estimate that, at any ...given time, there should be ∼1 km-scale or larger escaped asteroid in a transient direct (prograde) orbit with semimajor axis near that of Jupiter's (a aJ), with proportionally more smaller objects as determined by their size distribution. Most of these objects would be in the horseshoe dynamical state, and are hard to detect due to their moderate eccentricities (spending most of their time beyond 5 au) and longitudes relative to Jupiter being spread nearly all over the sky. We also show that 1% of the transient asteroid co-orbital population is on retrograde orbits with Jupiter. This population, like the recently identified asteroid (514107) 2015 BZ509, can spend millions of years with a aJ including tens or hundreds of thousands of years formally in the retrograde 1:-1 co-orbital resonance. Escaping near-Earth asteroids (NEAs) are thus likely the precursors of the handful of known high-inclination objects with a aJ. We compare the production of Jovian co-orbitals from escaping NEAs with those from incoming Centaurs. We find that temporary direct co-orbitals are likely dominated by Centaur capture, but we only find production of (temporary) retrograde Jovian co-orbitals (including very long-lived ones) from the NEA source. We postulate that the primordial elimination of the inner solar system's planetesimal population could provide a supply route for a metastable outer solar system reservoir for the high-inclination Centaurs.
We directly measure redshift evolution in the mean physical properties (far-infrared luminosity, temperature, and mass) of the galaxies that produce the cosmic infrared background (CIB), using ...measurements from the Balloon-borne Large Aperture Submillimeter Telescope (BLAST), and Spitzer which constrain the CIB emission peak. This sample is known to produce a surface brightness in the BLAST bands consistent with the full CIB, and photometric redshifts are identified for all of the objects. We find that most of the 70 Delta *mm background is generated at z 1 and the 500 Delta *mm background generated at z 1. A significant growth is observed in the mean luminosity from ~109-1012 L, and in the mean temperature by 10 K, from redshifts 0 < z < 3. However, there is only weak positive evolution in the comoving dust mass in these galaxies across the same redshift range. We also measure the evolution of the far-infrared luminosity density, and the star formation rate history for these objects, finding good agreement with other infrared studies up to z ~ 1, exceeding the contribution attributed to optically selected galaxies.
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