Spitzer Microlensing Parallax for OGLE-2016-BLG-1067: A Sub-Jupiter Orbiting an M Dwarf in the Disk
TL;DR: In this article, the authors reported the discovery of a sub-Jupiter mass planet orbiting beyond the snow line of an M-dwarf most likely in the Galactic disk as part of the joint Spitzer and ground-based monitoring of microlensing planetary anomalies toward the Galactic bulge.
Abstract: We report the discovery of a sub-Jupiter mass planet orbiting beyond the snow line of an M-dwarf most likely in the Galactic disk as part of the joint Spitzer and ground-based monitoring of microlensing planetary anomalies toward the Galactic bulge. The microlensing parameters are strongly constrained by the light curve modeling and in particular by the Spitzer-based measurement of the microlens parallax, $\\pi_\\mathrm{E}$. However, in contrast to many planetary microlensing events, there are no caustic crossings, so the angular Einstein radius, $\\theta_\\mathrm{E}$ has only an upper limit based on the light curve modeling alone. Additionally, the analysis leads us to identify 8 degenerate configurations: the four-fold microlensing parallax degeneracy being doubled by a degeneracy in the caustic structure present at the level of the ground-based solutions. To pinpoint the physical parameters, and at the same time to break the parallax degeneracy, we make use of a series of arguments: the $\\chi^2$ hierarchy, the Rich argument, and a prior Galactic model. The preferred configuration is for a host at $D_L=3.73_{-0.67}^{+0.66}~\\mathrm{kpc}$ with mass $M_\\mathrm{L}=0.30_{-0.12}^{+0.15}~\\mathrm{M_\\odot}$, orbited by a Saturn-like planet with $M_\\mathrm{planet}=0.43_{-0.17}^{+0.21}~\\mathrm{M_\\mathrm{Jup}}$ at projected separation $a_\\perp = 1.70_{-0.39}^{+0.38}~\\mathrm{au}$, about 2.1 times beyond the system snow line. Therefore, it adds to the growing population of sub-Jupiter planets orbiting near or beyond the snow line of M-dwarfs discovered by microlensing. Based on the rules of the real-time protocol for the selection of events to be followed up with Spitzer, this planet will not enter the sample for measuring the Galactic distribution of planets.
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TL;DR: In this paper, a photometry algorithm that is optimized for $Spitzer$ time series in crowded fields and that is particularly adapted to faint and/or heavily blended targets is developed. But this algorithm is limited to two difficult cases, one very faint and the other very crowded.
Abstract: We develop a new photometry algorithm that is optimized for $Spitzer$ time series in crowded fields and that is particularly adapted to faint and/or heavily blended targets. We apply this to the 170 targets from the 2015 $Spitzer$ microlensing campaign and present the results of three variants of this algorithm in an online catalog. We present detailed accounts of the application of this algorithm to two difficult cases, one very faint and the other very crowded. Several of $Spitzer$'s instrumental characteristics that drive the specific features of this algorithm are shared by $Kepler$ and $WFIRST$, implying that these features may prove to be a useful starting point for algorithms designed for microlensing campaigns by these other missions.
38 citations
University of Canterbury1, University of Warsaw2, Max Planck Society3, Ohio State University4, Korea Astronomy and Space Science Institute5, Harvard University6, Korea University of Science and Technology7, Chungbuk National University8, Weizmann Institute of Science9, Tsinghua University10, Kyung Hee University11, California Institute of Technology12
TL;DR: In this article, a small feature in the light curve of the OGLE-2018-BLG-0677 microlensing event leads to the discovery that the lens is a star-planet system.
Abstract: We report the analysis of the microlensing event OGLE-2018-BLG-0677. A small feature in the light curve of the event leads to the discovery that the lens is a star–planet system. Although there are two degenerate solutions that could not be distinguished for this event, both lead to a similar planet-host mass ratio. We perform a Bayesian analysis based on a Galactic model to obtain the properties of the system and find that the planet corresponds to a super-Earth/sub-Neptune with a mass of M_(planet) = 3.96^(+5.88)_(−2.66) M⊕. The host star has a mass of M_(host) = 0.12^(+0.14)_(−0.08) M⊙. The projected separation for the inner and outer solutions are 0.63^(+0.20)_(−0.17) au and 0.72^(+0.23)_(−0.19) au respectively. At Δχ² = χ² (1L1S) –χ ²(2L1S) = 46, this is by far the lowest Δχ² for any securely detected microlensing planet to date, a feature that is closely connected to the fact that it is detected primarily via a "dip" rather than a "bump."
23 citations
TL;DR: Spitzer was the first facility to detect thermal emission from a hot Jupiter-sized planet, and the range of its exoplanetary investigations grew to encompass transiting planets, microlensing, brown dwarfs, and direct imaging searches and astrometry as discussed by the authors.
Abstract: Observations of extrasolar planets were not projected to be a substantial part of the Spitzer Space Telescope’s mission when it was conceived and designed. Nevertheless, Spitzer was the first facility to detect thermal emission from a hot Jupiter-sized planet, and the range of its exoplanetary investigations grew to encompass transiting planets, microlensing, brown dwarfs, and direct imaging searches and astrometry. Spitzer used phase curves to measure the longitudinal distribution of heat as well as time-dependent heating on hot Jupiters. Its secondary eclipse observations strongly constrained the dayside thermal emission spectra and corresponding atmospheric compositions of hot Jupiters, and the timings of eclipses were used for studies of orbital dynamics. Spitzer’s sensitivity to carbon-based molecules such as methane and carbon monoxide was key to atmospheric composition studies of transiting exoplanets as well as imaging spectroscopy of brown dwarfs, and complemented Hubble Space Telescope spectroscopy at shorter wavelengths. Its capability for long continuous observing sequences enabled searches for new transiting planets around cool stars and helped to define the architectures of planetary systems such as TRAPPIST-1. Spitzer measured masses for small planets at large orbital distances using microlensing parallax. Spitzer observations of brown dwarfs probed their temperatures, masses and weather patterns. Imaging and astrometry from Spitzer was used to discover new planetary-mass brown dwarfs and to measure distances and space densities of many others. The Spitzer Space Telescope launched when the study of exoplanets was in its infancy, and yet it was remarkably successful in characterizing both exoplanet and brown dwarf systems through their mid-infrared emissions. This Review collates the highlights of Spitzer-based research in these fields.
23 citations
20 citations
TL;DR: Zhang et al. as discussed by the authors applied the automated anomaly-finder algorithm to 2018-2019 light curves from the KMTNet prime fields, with cadences ofGamma \geq 2\,{\rm hr}^{-1} .
Abstract: We apply the automated AnomalyFinder algorithm of Paper I (Zang et al. 2021b) to 2018-2019 light curves from the $\simeq 13\,{\rm deg}^2$ covered by the six KMTNet prime fields, with cadences $\Gamma \geq 2\,{\rm hr}^{-1}$. We find a total of 11 planets with mass ratios $q<2\times 10^{-4}$, including six newly discovered planets, one planet that was reported in Paper I, and recovery of four previously discovered planets. One of the new planets, OGLE-2018-BLG-0977Lb, is in a planetary-caustic event, while the other five (OGLE-2018-BLG-0506Lb, OGLE-2018-BLG-0516Lb, OGLE-2019-BLG-1492Lb, KMT-2019-BLG-0253, and KMT-2019-BLG-0953) are revealed by a "dip" in the light curve as the source crosses the host-planet axis on the opposite side of the planet. These subtle signals were missed in previous by-eye searches. The planet-host separations (scaled to the Einstein radius), $s$, and planet-host mass ratios, $q$, are, respectively, $(s,q\times 10^5) = (0.88, 4.1)$, $(0.96\pm 0.10, 8.3)$, $(0.94\pm 0.07, 13)$, $(0.97\pm 0.07, 18)$, $(0.97\pm0.04,4.1)$, and $(0.74,18)$, where the "$\pm$" indicates a discrete degeneracy. The 11 planets are spread out over the range $-5<\log q < -3.7$. Together with the two planets previously reported with $q\sim 10^{-5}$ from the 2018-2019 non-prime KMT fields, this result suggests that planets toward the bottom of this mass-ratio range may be more common than previously believed.
19 citations
References
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TL;DR: In this paper, the uncertainty inherent in any observational estimate of the IMF is investigated by studying the scatter introduced by Poisson noise and the dynamical evolution of star clusters, and it is found that this apparent scatter reproduces quite well the observed scatter in power-law index determinations, thus defining the fundamental limit within which any true variation becomes undetectable.
Abstract: A universal initial mass function (IMF) is not intuitive, but so far no convincing evidence for a variable IMF exists. The detection of systematic variations of the IMF with star-forming conditions would be the Rosetta Stone for star formation.
In this contribution an average or Galactic-field IMF is defined, stressing that there is evidence for a change in the power-law index at only two masses: near 0.5 M⊙ and near 0.08 M⊙. Using this supposed universal IMF, the uncertainty inherent in any observational estimate of the IMF is investigated by studying the scatter introduced by Poisson noise and the dynamical evolution of star clusters. It is found that this apparent scatter reproduces quite well the observed scatter in power-law index determinations, thus defining the fundamental limit within which any true variation becomes undetectable. The absence of evidence for a variable IMF means that any true variation of the IMF in well-studied populations must be smaller than this scatter.
Determinations of the power-law indices α are subject to systematic errors arising mostly from unresolved binaries. The systematic bias is quantified here, with the result that the single-star IMFs for young star clusters are systematically steeper by Δα≈0.5 between 0.1 and 1 M⊙ than the Galactic-field IMF, which is populated by, on average, about 5-Gyr-old stars. The MFs in globular clusters appear to be, on average, systematically flatter than the Galactic-field IMF (Piotto & Zoccali; Paresce & De Marchi), and the recent detection of ancient white-dwarf candidates in the Galactic halo and the absence of associated low-mass stars (Ibata et al.; Mendez & Minniti) suggest a radically different IMF for this ancient population. Star formation in higher metallicity environments thus appears to produce relatively more low-mass stars. While still tentative, this is an interesting trend, being consistent with a systematic variation of the IMF as expected from theoretical arguments.
6,784 citations
"Spitzer Microlensing Parallax for O..." refers methods in this paper
...For each simulated event, we draw a mass randomly from a Kroupa (2001) mass function....
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TL;DR: The Infrared Array Camera (IRAC) is one of the three focal plane instruments in the Spitzer Space Telescope as discussed by the authors, which is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 microns.
Abstract: The Infrared Array Camera (IRAC) is one of three focal plane instruments in the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 microns. Two nearly adjacent 5.2x5.2 arcmin fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 microns; 4.5 and 8 microns). All four detector arrays in the camera are 256x256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.
3,696 citations
TL;DR: The Infrared Array Camera (IRAC) is one of three focal plane instruments on the Spitzer Space Telescope as mentioned in this paper, which is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 m.
Abstract: The Infrared Array Camera (IRAC) is one of three focal plane instruments on the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 � m. Two nearly adjacent 5A2 ; 5A2 fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 � m; 4.5 and 8 � m). All four detector arrays in the camera are 256 ; 256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.
3,567 citations
TL;DR: In this paper, the relations between colors of the JHKL systems of several observatories are examined, and linear relations are derived for transformation between the (J-K), (H, K, H, and L) colors in the different systems.
Abstract: The relations between colors of the JHKL systems of several observatories are examined, and linear relations are derived for transformation between the (J-K), (J-H), (H-K), and (K-L) colors in the different systems. A homogenized system is proposed, based on the systems of Glass (1984) and Johnson et al. (1966). The homogenized data sets are used to derive intrinsic colors for a number of giants and dwarfs. The passbands of several IR systems are estimated and the synthetic colors of the systems are compared using blackbody and stellar fluxes. The passbands were adjusted in wavelength to produce agreement with observed relations between different systems, making it possible to estimate the effective wavelengths of the different natural systems.
2,213 citations
"Spitzer Microlensing Parallax for O..." refers methods in this paper
...Combining these results, moving from (V−I, I) to (V−K,K) by means of standard color relations (Bessell & Brett 1988) and using the relation between color and surface brightness (Kervella et al. 2004), we can finally estimate θ∗, which spans the range of values 0.81 − 0.86µas for the different…...
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TL;DR: A simple model of microlensing by massive objects that might be present in the halo of the Galaxy is presented in this article, where it is shown that in any nearby galaxy one star out of a million is strongly microlensed by a "dark" object located in the Galactic halo, if the hale is made up of objects more massive than about 10 to the -8th solar mass.
Abstract: A simple model of microlensing by massive objects that might be present in the halo of the Galaxy is presented. It is shown that in any nearby galaxy one star out of a million is strongly microlensed by a 'dark' object located in the Galactic halo, if the halo is made up of objects more massive than about 10 to the -8th solar mass. Monitoring the brightness of a few million stars in the Magellanic Clouds over a time scale between two hours and two years may lead to a discovery of 'dark halo' objects between 10 to the -6th and 10 to the -2nd solar mass, or it may put strong upper limits on the number of such objects.
1,437 citations
"Spitzer Microlensing Parallax for O..." refers background in this paper
...The microlensing magnification A(t) for a single lens is, in the standard Paczyński (1986) form, a function of three parameters: the time of maximum magnification, t0, the impact parameter, u0, and the Einstein time, tE....
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