ABSTRACT We obtained J-, H-, and JH-band photometry of known extrasolar planet transiting systems at the 2.1 m Kitt Peak National Observatory Telescope using the FLAMINGOS infrared camera between ...2008 October and 2011 October. From the derived light curves we have extracted the midtransit times, transit depths and transit durations for these events. The precise midtransit times obtained help improve the orbital periods and also constrain transit-time variations of the systems. For most cases the published system parameters successfully accounted for our observed light curves, but in some instances we derive improved planetary radii and orbital periods. We complemented our 2.1 m infrared observations using CCD z′-band and B-band photometry (plus two Hα filter observations) obtained with the Kitt Peak Visitor Center Telescope, and with four H-band transits observed in 2007 October with the NSO's 1.6 m McMath-Pierce Solar Telescope. The principal highlights of our results are (1) Our ensemble of J-band planetary radii agree with optical radii, with the best-fit relation being (Rp/R∗)J = 0.0017 + 0.979(Rp/R∗)vis. (2) We observe starspot crossings during the transit of WASP-11/HAT-P-10. (3) We detect starspot crossings by HAT-P-11b (Kepler-3b), thus confirming that the magnetic evolution of the stellar active regions can be monitored even after the Kepler mission has ended. (4) We confirm a grazing transit for HAT-P-27/WASP-40. In total, we present 57 individual transits of 32 known exoplanet systems.
From 2004 to 2017, the Cassini spacecraft orbited Saturn, completing 127 close flybys of its largest moon, Titan. Cassini's Composite Infrared Spectrometer (CIRS), one of 12 instruments carried on ...board, profiled Titan in the thermal infrared (7-1000 m) throughout the entire 13 yr mission. CIRS observed on both targeted encounters (flybys) and more distant opportunities, collecting 8.4 million spectra from 837 individual Titan observations over 3633 hr. Observations of multiple types were made throughout the mission, building up a vast mosaic picture of Titan's atmospheric state across spatial and temporal domains. This paper provides a guide to these observations, describing each type and chronicling its occurrences and global-seasonal coverage. The purpose is to provide a resource for future users of the CIRS data set, as well as those seeking to put existing CIRS publications into the overall context of the mission, and to facilitate future intercomparison of CIRS results with those of other Cassini instruments and ground-based observations.
•First spectral analysis of Nix, Hydra and Kerberos.•Crystalline water ice found on all three.•2.21 µm band seen on Nix and Hydra indicating an ammoniated species.•Disk resolved spectroscopy of ...Nix.•Temperature and crystalline H2O-ice fraction estimated for Nix and Hydra.
On July 14, 2015, NASA’s New Horizons spacecraft encountered the Pluto-system. Using the near-infrared spectral imager, New Horizons obtained the first spectra of Nix, Hydra, and Kerberos and detected the 1.5 and 2.0 µm bands of H2O-ice on all three satellites. On Nix and Hydra, New Horizons also detected bands at 1.65 and 2.21 µm that indicate crystalline H2O-ice and an ammoniated species, respectively. A similar band linked to NH3-hydrate has been detected on Charon previously. However, we do not detect the 1.99 µm band of NH3-hydrate. We consider NH4Cl (ammonium chloride), NH4NO3 (ammonium nitrate) and (NH4)2CO3 (ammonium carbonate) as potential candidates, but lack sufficient laboratory measurements of these and other ammoniated species to make a definitive conclusion. We use the observations of Nix and Hydra to estimate the surface temperature and crystalline H2O-ice fraction. We find surface temperatures < 20 K ( <70 K with 1-σ error) and 23 K ( < 150 K with 1-σ error) for Nix and Hydra, respectively. We find crystalline H2O-ice fractions of 78−22+12% and > 30% for Nix an Hydra, respectively. New Horizons observed Nix and Hydra twice, about 2–3 hours apart, or 5 and 25% of their respective rotation periods. We find no evidence for rotational differences in the disk-averaged spectra between the two observations of Nix or Hydra. We perform a pixel-by-pixel analysis of Nix’s disk-resolved spectra and find that the surface is consistent with a uniform crystalline H2O-ice fraction, and a ∼ 50% variation in the normalized band area of the 2.21 µm band with a minimum associated with the red blotch seen in color images of Nix. Finally, we find evidence for bands on Nix and Hydra at 2.42 and possibly 2.45 µm, which we cannot identify, and, if real, do not appear to be associated with the ammoniated species. We do not detect other ices, such as CO2, CH3OH and HCN.
•Applying PC-SAFT, CRYOCHEM can predict the properties of Titan’s fluids.•Titan’s liquids have densities that exhibit exotic behavior.•The pattern of Titan’s fluid global circulation is different ...from that on Earth.
Based on a validated model for cryogenic chemical systems, referred to as CRYOCHEM (“Cryogenic Chemistry Model”), surface liquids on Titan are shown to exhibit exotic behavior of density increase with temperature but decrease with pressure, unless the temperature falls below 89.8K. It is also the case for the atmospheric liquid condensates below an altitude where the liquid density is minimum. The exotic behavior is of compositional origin, which does not have an analog in the atmosphere and liquid water on Earth. As the latitudinal and seasonal variations of surface temperature are known, it is possible to map out the global liquid and vapor density variations as well as the equilibrium phase compositions, which will be useful as inputs for atmospheric general circulation models (GCMs) and investigations of Titan’s methane-equivalent of Earth’s hydrological cycle, local subsurface alkanology (equivalent to hydrology on Earth), lake convection, and clastic and chemical sedimentation in the lakes. Further, the density variations can be used to derive a general idea about global fluid circulation in the upper crust based on averaged conditions on Titan. The surface liquid should tend to flow toward the hottest spot on Titan and a return flow occurs beneath the surface, thus providing analogies with thermohaline circulation in Earth’s oceans. The vapor phase, on the other hand, has ordinary properties that make the global atmospheric circulation similar to the Hadley cell on Earth, but Titan’s cycle reaches the polar regions. The calculated compositions of surface liquids are more methane-rich than other models indicated, thus qualitatively in the right direction to satisfy polar-lake compositions deduced from loss tangents. However, quantitatively there remains a need to find yet more accurate liquid compositions and an optimum equilibrium within constraints of the atmospheric measurements.
•We infer the thermal and chemical evolution of Titan’s stratosphere (2010–2014).•We find different behavior for mid and high northern and southern latitudes.•The temperature decrease from 2010 to ...2014 near the south pole reaches 40K.•The abundances of some species have increased dramatically since 2012 at 70°S.•We bracket the time frame when the atmospheric flow reverses from S to N and N to S.
We analyze spectra acquired by the Cassini/Composite Infrared Spectrometer (CIRS) at high resolution from October 2010 until September 2014 in nadir mode. Up until mid 2012, Titan’s Northern atmosphere exhibited the enriched chemical content found since the Voyager days (November 1980), with a peak around the Northern Spring Equinox (NSE) in 2009. Since then, we have observed the appearance at Titan’s south pole of several trace species for the first time, such as HC3N and C6H6, observed only at high northern latitudes before equinox. We investigate here latitudes poleward of 50°S and 50°N from 2010 (after the Southern Autumnal Equinox) until 2014. For some of the most abundant and longest-lived hydrocarbons (C2H2, C2H6 and C3H8) and CO2, the evolution in the past 4years at a given latitude is not very significant within error bars especially until mid-2013. In more recent dates, these molecules show a trend for increase in the south. This trend is dramatically more pronounced for the other trace species, especially in 2013–2014, and at 70°S relative to 50°S. These two regions then demonstrate that they are subject to different dynamical processes in and out of the polar vortex region. For most species, we find higher abundances at 50°N compared to 50°S, with the exception of C3H8, CO2, C6H6 and HC3N, which arrive at similar mixing ratios after mid-2013. While the 70°N data show generally no change with a trend rather to a small decrease for most species within 2014, the 70°S results indicate a strong enhancement in trace stratospheric gases after 2012. The 663cm−1 HC3N and the C6H6 674cm−1 emission bands appeared in late 2011/early 2012 in the south polar regions and have since then exhibited a dramatic increase in their abundances. At 70°S HC3N, HCN and C6H6 have increased by 3 orders of magnitude over the past 3–4years while other molecules, including C2H4, C3H4 and C4H2, have increased less sharply (by 1–2 orders of magnitude). This is a strong indication of the rapid and sudden buildup of the gaseous inventory in the southern stratosphere during 2013–2014, as expected as the pole moves deeper into winter shadow. Subsidence gases that accumulate in the absence of ultraviolet sunlight, evidently increased quickly since 2012 and some of them may be responsible also for the reported haze decrease in the north and its appearance in the south at the same time.
Objective Arteriovenous fistulas (AVFs) are the preferred choice for hemodialysis vascular access (AV access); however, there is debate over the utility of AVFs in older patients, particularly ...concerning access maturation and functionality. We reviewed our AV access experience in patients ≥65 years of age. Methods We analyzed consecutive AV access patients ≥65 years old with access operations between March 2003 and December 2009. All patients had ultrasound vessel mapping. In addition to overall outcomes review, the data for patients ≥65 years old were stratified into three 10-year increments by age for further analysis. We compared functional patency data for our older patients with those of our non-elderly patients aged 21 to 64 years treated during the same time period. Results Four hundred sixty-one consecutive AV access patients new to our practice were included in this study. Ages were 65 to 94 years (mean, 73 years). Two hundred thirty-six (51.2%) were female, 276 (59.9%) patients were diabetic, and 103 (22.3%) were obese. One hundred seven (23.2%) patients had previous access operations. Radiocephalic AVFs were constructed in 29 (6.3%) patients, 99 (21.5%) patients had brachial artery inflow AVFs, 330 (71.6%) had proximal radial artery AVFs, and three were based on the femoral artery. Transposition AVFs were used in 124 (26.9%) patients. No grafts were used for AV access in any patient during the study period. Time to AVF use was 0.5 to 6 months (mean, 1.5 months). Primary, primary assisted, and cumulative patency for patients aged 65 to 94 years were 59.9%, 93.7%, and 96.9% at 12 months and 45.3%, 90.1%, and 94.6% at 24 months, respectively. Follow-up was 1.5 to 77 months (mean, 17.0 months). Subgroup age stratification (65-74 n = 268, 75-84 n = 167, 85-94 n = 26 years) found no statistical difference in functional access outcomes. Primary, primary assisted, and cumulative patency rates were not statistically different in the elderly and non-elderly populations ( P = .29, .27, and .37, respectively). One hundred fifty-six patients died during the study period, 1.3 to 61 months (mean, 20 months) after access creation. No deaths were related to access operations. Conclusions AVFs are feasible and offer functional and timely AV access in older patients. There was no difference in functional access outcomes for older patients with subgroup age stratification. AVF patency rates were not statistically different in the elderly and non-elderly populations. Cumulative AVF patency for patients ≥65 years of age was 96.9% at 12 months and 94.6% at 24 months.
We have analyzed data recorded by the Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft during the Titan flybys T0–T10 (July 2004–January 2006). The spectra characterize various ...regions on Titan from 70° S to 70° N with a variety of emission angles. We study the molecular signatures observed in the mid-infrared CIRS detector arrays (FP3 and FP4, covering roughly the 600–1500 cm
−1 spectral range with apodized resolutions of 2.54 or 0.53 cm
−1). The composite spectrum shows several molecular signatures: hydrocarbons, nitriles and CO
2. A firm detection of benzene (C
6H
6) is provided by CIRS at levels of about
3.5
×
10
−9
around 70° N. We have used temperature profiles retrieved from the inversion of the emission observed in the methane
ν
4
band at 1304 cm
−1 and a line-by-line radiative transfer code to infer the abundances of the trace constituents and some of their isotopes in Titan's stratosphere. No longitudinal variations were found for these gases. Little or no change is observed generally in their abundances from the south to the equator. On the other hand, meridional variations retrieved for these trace constituents from the equator to the North ranged from almost zero (no or very little meridional variations) for C
2H
2, C
2H
6, C
3H
8, C
2H
4 and CO
2 to a significant enhancement at high northern (early winter) latitudes for HCN, HC
3N, C
4H
2, C
3H
4 and C
6H
6. For the more important increases in the northern latitudes, the transition occurs roughly between 30 and 50 degrees north latitude, depending on the molecule. Note however that the very high-northern latitude results from tours TB–T10 bear large uncertainties due to few available data and problems with latitude smearing effects. The observed variations are consistent with some, but not all, of the predictions from dynamical-photochemical models. Constraints are set on the vertical distribution of C
2H
2, found to be compatible with 2-D equatorial predictions by global circulation models. The D/H ratio in the methane on Titan has been determined from the CH
3D band at 1156 cm
−1 and found to be
1.17
−0.28
+0.23
×
10
−4
. Implications of this deuterium enrichment, with respect to the protosolar abundance on the origin of Titan, are discussed. We compare our results with values retrieved by Voyager IRIS observations taken in 1980, as well as with more recent (1997) disk-averaged Infrared Space Observatory (ISO) results and with the latest Cassini–Huygens inferences from other instruments in an attempt to better comprehend the physical phenomena on Titan.
The Cassini Composite Infrared Spectrometer (CIRS) observed thermal emission in the far- and mid-infrared (from 10 to 1500 cm−1), enabling spatiotemporal studies of ethane on Titan across the span of ...the Cassini mission from 2004 through 2017. Many previous measurements of ethane on Titan have relied on modeling the molecule's mid-infrared 12 band, centered on 822 cm−1. Other bands of ethane at shorter and longer wavelengths were seen, but have not been modeled to measure ethane abundance. Spectral line lists of the far-infrared 4 torsional band at 289 cm−1 and the mid-infrared 8 band centered at 1468 cm−1 have recently been studied in the laboratory. We model CIRS observations of each of these bands (along with the 12 band) separately and compare the retrieved mixing ratios from each spectral region. Nadir observations of the 4 band probe the low stratosphere below 100 km. Our equatorial measurements at 289 cm−1 show an abundance of (1.0 0.4) × 10−5 at 88 km from 2007 to 2017. This mixing ratio is consistent with measurements at higher altitudes, in contrast to the depletion that many photochemical models predict. Measurements from the 12 and 8 bands are comparable to each other, with the 12 band probing an altitude range that extends deeper in the atmosphere. We suggest that future studies of planetary atmospheres may observe the 8 band, enabling shorter wavelength studies of ethane. There may also be an advantage to observing both the ethane 8 band and nearby methane 4 band in the same spectral window.
We analyze 26 archival Kepler transits of the exo-Neptune HAT-P-11b, supplemented by ground-based transits observed in the blue (B band) and near-IR (J band). Both the planet and host star are ...smaller than previously believed; our analysis yields Rp = 4.31 R {circled plus} ? 0.06 R {circled plus} and Rs = 0.683 R ? 0.009 R , both about 3 Delta *s smaller than the discovery values. Our ground-based transit data at wavelengths bracketing the Kepler bandpass serve to check the wavelength dependence of stellar limb darkening, and the J-band transit provides a precise and independent constraint on the transit duration. Both the limb darkening and transit duration from our ground-based data are consistent with the new Kepler values for the system parameters. Our smaller radius for the planet implies that its gaseous envelope can be less extensive than previously believed, being very similar to the H-He envelope of GJ 436b and Kepler-4b. HAT-P-11 is an active star, and signatures of star spot crossings are ubiquitous in the Kepler transit data. We develop and apply a methodology to correct the planetary radius for the presence of both crossed and uncrossed star spots. Star spot crossings are concentrated at phases --0.002 and +0.006. This is consistent with inferences from Rossiter-McLaughlin measurements that the planet transits nearly perpendicular to the stellar equator. We identify the dominant phases of star spot crossings with active latitudes on the star, and infer that the stellar rotational pole is inclined at about 12? ? 5? to the plane of the sky. We point out that precise transit measurements over long durations could in principle allow us to construct a stellar Butterfly diagram to probe the cyclic evolution of magnetic activity on this active K-dwarf star.
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