Search

We report our search for infrared excesses in the Spitzer/Infrared Array Camera survey of the Kepler field at 3.6 and 4.5 μ m. The Spitzer Kepler Survey contains ∼190,000 targets, which we reduce to ∼117,000 targets after applying multiple filters to arrive at a high-quality sample for spectral energy distribution fitting. Of the ∼117,000, we find 11 Sun-like stars ( T _eff ∼ 6000 K) with infrared excesses of high significance (>4 σ ) ranging from 10% to 40% above the photosphere at 4.5 μ m, which is characteristic of debris disk systems. Blackbody fits of the infrared excesses for the 11 debris disk candidates suggest dust temperatures of 400–1400 K. None of the candidates have reported exoplanet detections. High-quality 1–5 μ m or longer spectra or photometry would be necessary to confirm the candidates as debris disk systems.

We present reverberation mapping measurements for the prominent ultraviolet broad emission lines of the active galactic nucleus Mrk 817 using 165 spectra obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope. Our ultraviolet observations are accompanied by X-ray, optical, and near-infrared observations as part of the AGN Space Telescope and Optical Reverberation Mapping Program 2 (AGN STORM 2). Using the cross-correlation lag analysis method, we find significant correlated variations in the continuum and emission-line light curves. We measure rest-frame delayed responses between the far-ultraviolet continuum at 1180 Å and Ly α λ 1215 Å ( ${10.4}_{-1.4}^{+1.6}$ days), N v λ 1240 Å ( ${15.5}_{-4.8}^{+1.0}$ days), Si iv + ]O iv λ 1397 Å ( ${8.2}_{-1.4}^{+1.4}$ days), C iv λ 1549 Å ( ${11.8}_{-2.8}^{+3.0}$ days), and He ii λ 1640 Å ( ${9.0}_{-1.9}^{+4.5}$ days) using segments of the emission-line profile that are unaffected by absorption and blending, which results in sampling different velocity ranges for each line. However, we find that the emission-line responses to continuum variations are more complex than a simple smoothed, shifted, and scaled version of the continuum light curve. We also measure velocity-resolved lags for the Ly α and C iv emission lines. The lag profile in the blue wing of Ly α is consistent with virial motion, with longer lags dominating at lower velocities, and shorter lags at higher velocities. The C iv lag profile shows the signature of a thick rotating disk, with the shortest lags in the wings, local peaks at ±1500 km s ^−1 , and a local minimum at the line center. The other emission lines are dominated by broad absorption lines and blending with adjacent emission lines. These require detailed models, and will be presented in future work.

We validate the presence of a two-planet system orbiting the 0.15–1.4 Gyr K4 dwarf TOI 560 (HD 73583). The system consists of an inner moderately eccentric transiting mini-Neptune (TOI 560 b, $P={6.3980661}_{-0.0000097}^{+0.0000095}$ days, $e={0.294}_{-0.062}^{+0.13}$ , $M={0.94}_{-0.23}^{+0.31}{M}_{\mathrm{Nep}}$ ) initially discovered in the Sector 8 Transiting Exoplanet Survey Satellite (TESS) mission observations, and a transiting mini-Neptune (TOI 560 c, $P={18.8805}_{-0.0011}^{+0.0024}$ days, $M={1.32}_{-0.32}^{+0.29}{M}_{\mathrm{Nep}}$ ) discovered in the Sector 34 observations, in a rare near-1:3 orbital resonance. We utilize photometric data from TESS Spitzer, and ground-based follow-up observations to confirm the ephemerides and period of the transiting planets, vet false-positive scenarios, and detect the photoeccentric effect for TOI 560 b. We obtain follow-up spectroscopy and corresponding precise radial velocities (RVs) with the iSHELL spectrograph at the NASA Infrared Telescope Facility and the HIRES Spectrograph at Keck Observatory to validate the planetary nature of these signals, which we combine with published Planet Finder Spectrograph RVs from the Magellan Observatory. We detect the masses of both planets at >3 σ significance. We apply a Gaussian process (GP) model to the TESS light curves to place priors on a chromatic RV GP model to constrain the stellar activity of the TOI 560 host star, and confirm a strong wavelength dependence for the stellar activity demonstrating the ability of near-IR RVs to mitigate stellar activity for young K dwarfs. TOI 560 is a nearby moderately young multiplanet system with two planets suitable for atmospheric characterization with the James Webb Space Telescope and other upcoming missions. In particular, it will undergo six transit pairs separated by

Studies of the atmospheres of hot Jupiters reveal a diversity of atmospheric composition and haze properties. Similar studies on individual smaller, temperate planets are rare owing to the inherent difficulty of the observations and also to the average faintness of their host stars. To investigate their ensemble atmospheric properties, we construct a sample of 28 similar planets, all of which possess equilibrium temperature within 300–500 K, have similar size (1–3 R⊕), and orbit early M dwarfs and late K dwarfs with effective temperatures within a few hundred kelvin of one another. In addition, NASA’s Kepler/K2 and Spitzer missions gathered transit observations of each planet, producing a uniform transit data set in both wavelength and coarse planetary type. With the transits measured in Kepler’s broad optical bandpass and Spitzer’s 4.5 μm wavelength bandpass, we measure the transmission spectral slope, Δz/H, for the entire sample. While this measurement is too uncertain in nearly all cases to infer the properties of any individual planet, the distribution of Δz/H among several dozen similar planets encodes a key trend. We find that the distribution of Δz/H is not well described by a single Gaussian distribution. Rather, a ratio of the Bayesian evidences between the likeliest one-component and two-component Gaussian models favors the latter by a ratio of 100:3. In the best-fit two-component Gaussian model, one Gaussian is centered around an average Δz/H = −0.1 with a standard deviation of 8.2, while a smaller but significant second population (20% ± 10% of all) is located at significantly higher Δz/H center values with higher uncertainty. Although the exact shape and locations of the Gaussian models are sensitive to our assumptions in mean molecular weight, we can conclude that (1) there exist two populations of small and temperate planets regarding their effective radius variations between the Kepler bandpass and Spitzer bandpass and (2) atmospheres of this kind of planets are far from uniformly flat, and a fraction of them may be particularly favorable for follow-up observations from space-based platforms like the Hubble Space Telescope and the James Webb Space Telescope. [ABSTRACT FROM AUTHOR]

Several recent studies have reported different intrinsic correlations between the active galactic nucleus (AGN) mid-IR luminosity () and the rest-frame 2–10 keV luminosity (LX) for luminous quasars. To understand the origin of the difference in the observed relations, we study a sample of 3247 spectroscopically confirmed type 1 AGNs collected from Boötes, XMM-COSMOS, XMM-XXL-North, and the Sloan Digital Sky Survey quasars in the Swift/XRT footprint spanning over four orders of magnitude in luminosity. We carefully examine how different observational constraints impact the observed relations, including the inclusion of X-ray-nondetected objects, possible X-ray absorption in type 1 AGNs, X-ray flux limits, and star formation contamination. We find that the primary factor driving the different relations reported in the literature is the X-ray flux limits for different studies. When taking these effects into account, we find that the X-ray luminosity and mid-IR luminosity (measured at rest-frame , or ) of our sample of type 1 AGNs follow a bilinear relation in the log–log plane: erg s−1 + (44.60 ± 0.01) for erg s−1, and erg s−1 + (44.51 ± 0.01) for erg s−1. This suggests that the luminous type 1 quasars have a shallower correlation than the approximately linear relations found in local Seyfert galaxies. This result is consistent with previous studies reporting a luminosity-dependent relation and implies that assuming a linear relation to infer the neutral gas column density for X-ray absorption might overestimate the column densities in luminous quasars. [ABSTRACT FROM AUTHOR]

The recent detections of two transit events attributed to the super-Earth candidate K2-18b have provided the unprecedented prospect of spectroscopically studying a habitable-zone planet outside the solar system. Orbiting a nearby M2.5 dwarf and receiving virtually the same stellar insolation as Earth, K2-18b would be a prime candidate for the first detailed atmospheric characterization of a habitable-zone exoplanet using the Hubble Space Telescope (HST)and James Webb Space Telescope (JWST). Here, we report the detection of a third transit of K2-18b near the predicted transit time using the Spitzer Space Telescope. The Spitzer detection demonstrates the periodic nature of the two transit events discovered by K2, confirming that K2-18 is indeed orbited by a super-Earth in a 33 day orbit, ruling out the alternative scenario of two similarly sized, long-period planets transiting only once within the 75 day Kepler Space Telescope (K2) observation. We also find, however, that the transit event detected by Spitzer occurred 1.85 hr () before the predicted transit time. Our joint analysis of the Spitzer and K2 photometry reveals that this early occurrence of the transit is not caused by transit timing variations, but the result of an inaccurate ephemeris due to a previously undetected data anomaly in the K2 photometry. We refit the ephemeris and find that K2-18b would have been lost for future atmospheric characterizations with HST and JWST if we had not secured its ephemeris shortly after the discovery. We caution that immediate follow-up observations as presented here will also be critical for confirming and securing future planets discovered by the Transiting Exoplanet Survey Satellite (TESS), in particular if only two transit events are covered by the relatively short 27-day TESS campaigns. [ABSTRACT FROM AUTHOR]

We have used the Spitzer Space Telescope to observe two transiting planetary systems orbiting low-mass stars discovered in the Kepler K2 mission. The system K2-3 (EPIC 201367065) hosts three planets, while K2-26 (EPIC 202083828) hosts a single planet. Observations of all four objects in these two systems confirm and refine the orbital and physical parameters of the planets. The refined orbital information and more precise planet radii possible with Spitzer will be critical for future observations of these and other K2 targets. For K2-3b we find marginally significant evidence for a transit timing variation between the K2 and Spitzer epochs. [ABSTRACT FROM AUTHOR]

We present a measurement of the star formation properties of a uniform sample of mid-IR-selected, optically unobscured, and obscured quasars (QSO1s and QSO2s) in the Boötes survey region. We use a spectral energy distribution analysis for photometric data spanning optical to far-IR wavelengths to separate the active galactic nucleus (AGN) and host galaxy components. We find that when compared to a matched sample of QSO1s, the QSO2s have roughly twice the far-IR detection fractions, far-IR fluxes, and infrared star formation luminosities (). Correspondingly, we show that the AGN obscured fraction rises from 0.3 to 0.7 between (4–40) × . We also find evidence associating X-ray absorption with the presence of far-IR-emitting dust. Overall, these results are consistent with galaxy evolution models in which quasar obscuration is associated with dust-enshrouded starburst galaxies. [ABSTRACT FROM AUTHOR]