OGLE-2017-BLG-1130: The First Binary Gravitational Microlens Detected from Spitzer Only

Novati, S. Calchi; Udalski, A.; Gould, Andrew; Mao, Shude; Zang, Weicheng; Beichman, Charles; Bryden, G.; Carey, Sean; Gaudi, B. Scott; Henderson, Calen B.; Shvartzvald, Yossi; Yee, Jennifer C.; Team, Spitzer; Mróz, P.; Poleski, R.; Skowron, J.; Szymański, M. K.; Soszyński, I.; Kozłowski, S.; Ulaczyk, K.; Pawlak, M.; Albrow, M. D.; Chung, Sun-Ju; Han, Cheongho; Hwang, Kyu-Ha; Jung, Youn Kil; Ryu, Yoon-Hyun; Shin, In-Gu; Zhu, Wei; Cha, Sang-Mok; Kim, Dong-Jin; Kim, S.-L.; Lee, C.-U.; Lee, D.-J.; Lee, Y.; Park, B.-G.; Pogge, Richard W.

doi:10.3847/1538-4357/aabcd2

Cited by 11 publications

(9 citation statements)

References 35 publications

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“…The latter is possible in principle since the ground-based and space-based observatories probe different parts of the Einstein ring (Gould & Horne 2013). For example, the binary anomaly of OGLE-2018-BLG-1130 was only detected by Spitzer while showing no binarity in the ground-based observations (Wang et al 2018).…”

Section: Ogle-2015-blg-0448mentioning

confidence: 99%

“…PID 10036, 11006, 12013, 12015, 13005, 14012, PI: S. Dong; PID: 13250, PI: S. Carey; PID 14121). Following the successful 2014 pilot program, Spitzer took on a new role as a 'microlens parallax satellite' with the primary objective of measuring the Galactic distribution of exoplanets towards the bulge (Calchi Novati et al 2015a,b, 2018Shvartzvald et al 2015Shvartzvald et al , 2016Shvartzvald et al , 2017Shvartzvald et al , 2019Udalski et al 2015bUdalski et al , 2018Yee et al 2015a,b;Zhu et al 2015aZhu et al ,b, 2016Zhu et al , 2017bBozza et al 2016;Han et al 2016Han et al , 2017Han et al , 2018Poleski et al 2016;Street et al 2016;Chung et al 2017Chung et al , 2019Shin et al 2017Shin et al , 2018Albrow et al 2018;Ryu et al 2018;Wang et al 2018;Jung et al 2019;Li et al 2019;Shan et al 2019;Zang et al 2019Zang et al , 2020Gould et al 2020;Hirao et al 2020).…”

Section: Introductionmentioning

confidence: 99%

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Pixel level decorrelation in service of the Spitzer microlens parallax survey

Dang

Novati

Carey

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Microlens parallax measurements combining space-based and ground-based observatories can be used to study planetary demographics. In recent years, the Spitzer Space Telescope was used as a microlens parallax satellite. Meanwhile, Spitzer IRAC has been employed to study short-period exoplanets and their atmospheres. As these investigations require exquisite photometry, they motivated the development of numerous self-calibration techniques now widely used in the exoplanet atmosphere community. Specifically, Pixel Level Decorrelation (PLD) was developed for starring-mode observations in uncrowded fields. We adapt and extend PLD to make it suitable for observations obtained as part of the Spitzer Microlens Parallax Campaign. We apply our method to two previously published microlensing events, OGLE-2017-BLG-1140 and OGLE-2015-BLG-0448, and compare its performance to the state-of-the-art pipeline used to analyses Spitzer microlensing observation. We find that our method yields photometry 1.5–6 times as precise as previously published. In addition to being useful for Spitzer, a similar approach could improve microlensing photometry with the Nancy Grace Roman Space Telescope.

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Section: Ogle-2015-blg-0448mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Pixel level decorrelation in service of the Spitzer microlens parallax survey

Dang

Novati

Carey

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…For microlensing events, it is possible that the source passed close to a component of the lens system as seen by K2, but the trajectory seen from the ground did not pass this component closely (Gould & Horne 2013;Poleski et al 2016;Wang et al 2018). Identifying such events may be problematic in photometric methods that depend on an assumed astrophysical model.…”

Section: Limitationsmentioning

confidence: 99%

Photometry of K2 Campaign 9 bulge data

Poleski

Penny

Gaudi

et al. 2019

A&A

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K2 in its Campaign 9 observed dense Galactic bulge regions in order to constrain the microlensing parallaxes and probe for free-floating planets. Photometric reduction of the K2 bulge data poses a significant challenge due to very high stellar density, large camera pixels, and unstable pointing of the spacecraft. Here we present a new method for K2 photometry extraction. We extend Causal Pixel Model developed for less-crowded fields by: using the pixel response function together with accurate astrometric grids, combining signals from a few pixels, and fully including the astrophysical model. We test the method on two microlensing events and a long-period eclipsing binary.

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“…The last argument is the Bayesian inference. Because the lens distance and velocity are calculated in each solution, we can statistically estimate the lens location for each solution by conducting a Bayesian analysis with a typical Galactic model (Zhu et al 2017;Wang et al 2018). In practice, we estimate the probabilities that the lens lies in the bulge or the disc separately in each solution.…”

Section: Locationmentioning

confidence: 99%

OGLE-2017-BLG-1186: first application of asteroseismology and Gaussian processes to microlensing

Li¹,

Zang²,

Udalski³

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Abstract We present the analysis of the event OGLE-2017-BLG-1186 from the 2017 Spitzer microlensing campaign. This is a remarkable microlensing event because its source is photometrically bright and variable, which makes it possible to perform an asteroseismic analysis using ground-based data. We find that the source star is an oscillating red giant with average time-scale of ∼9 d. The asteroseismic analysis also provides us source properties including the source angular size (∼27 $\mu$as) and distance (∼11.5 kpc), which are essential for inferring the properties of the lens. When fitting the light curve, we test the feasibility of Gaussian processes (GPs) in handling the correlated noise caused by the variable source. We find that the parameters from the GP model are generally more loosely constrained than those from the traditional χ2 minimization method. We note that this event is the first microlensing system for which asteroseismology and GPs have been used to account for the variable source. With both finite-source effect and microlens parallax measured, we find that the lens is likely a ∼0.045 M⊙ brown dwarf at distance ∼9.0 kpc, or a ∼0.073 M⊙ ultracool dwarf at distance ∼9.8 kpc. Combining the estimated lens properties with a Bayesian analysis using a Galactic model, we find a $\sim 35{{\ \rm per\ cent}}$ probability for the lens to be a bulge object and $\sim 65{{\ \rm per\ cent}}$ to be a background disc object.

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OGLE-2017-BLG-1130: The First Binary Gravitational Microlens Detected from Spitzer Only

Cited by 11 publications

References 35 publications

Pixel level decorrelation in service of the Spitzer microlens parallax survey

Pixel level decorrelation in service of the Spitzer microlens parallax survey

Photometry of K2 Campaign 9 bulge data

OGLE-2017-BLG-1186: first application of asteroseismology and Gaussian processes to microlensing

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