OGLE-2015-BLG-0845L: A low-mass M dwarf from the microlensing parallax and xallarap effects

Zhecheng Hu; Wei Zhu; Andrew Gould; Andrzej Udalski; Takahiro Sumi; Ping Chen; Sebastiano Calchi Novati; Jennifer C. Yee; Charles A. Beichman; Geoffery Bryden; Sean Carey; Michael Fausnaugh; B. Scott Gaudi; Calen B. Henderson; Yossi Shvartzvald; Benjamin Wibking; Przemek Mróz; Jan Skowron; Radoslaw Poleski; Michaeł K. Szymański; Igor Soszynśki; Paweł Pietrukowicz; Szymon Kozłowski; Krzysztof Ulaczyk; Krzysztof A. Rybicki; Patryk Iwanek; Marcin Wrona; Mariusz Gromadzki; Fumio Abe; Richard Barry; David P. Bennett; Aparna Bhattacharya; Ian A. Bond; Hirosane Fujii; Akihiko Fukui; Ryusei Hamada; Yuki Hirao; Stela Ishitani Silva; Yoshitaka Itow; Rintaro Kirikawa; Naoki Koshimoto; Yutaka Matsubara; Shota Miyazaki; Yasushi Muraki; Greg Olmschenk; Clément Ranc; Nicholas J. Rattenbury; Yuki Satoh; Daisuke Suzuki; Mio Tomoyoshi; Paul. J. Tristram; Aikaterini Vandorou; Hibiki Yama; Kansuke Yamashita

AI summary · arXiv: 2404.13031v1 · astro-ph.SR

OGLE-2015-BLG-0845L: A low-mass M dwarf from the microlensing parallax and xallarap effects

Zhecheng Hu, Wei Zhu, Andrew Gould, Andrzej Udalski, Takahiro Sumi, Ping Chen, Sebastiano Calchi Novati, Jennifer C. Yee,

and 46 more authors

Charles A. Beichman, Geoffery Bryden, Sean Carey, Michael Fausnaugh, B. Scott Gaudi, Calen B. Henderson, Yossi Shvartzvald, Benjamin Wibking, Przemek Mróz, Jan Skowron, Radoslaw Poleski, Michaeł K. Szymański, Igor Soszynśki, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof Ulaczyk, Krzysztof A. Rybicki, Patryk Iwanek, Marcin Wrona, Mariusz Gromadzki, Fumio Abe, Richard Barry, David P. Bennett, Aparna Bhattacharya, Ian A. Bond, Hirosane Fujii, Akihiko Fukui, Ryusei Hamada, Yuki Hirao, Stela Ishitani Silva, Yoshitaka Itow, Rintaro Kirikawa, Naoki Koshimoto, Yutaka Matsubara, Shota Miyazaki, Yasushi Muraki, Greg Olmschenk, Clément Ranc, Nicholas J. Rattenbury, Yuki Satoh, Daisuke Suzuki, Mio Tomoyoshi, Paul. J. Tristram, Aikaterini Vandorou, Hibiki Yama, Kansuke Yamashita

Original paper Submitted to arXiv on 19 Apr. 2024 13 pages, 10 figures. Submitted to Monthly Notices of the Royal Astronomical Society License: CC BY 4.0

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The essentials

Microlensing event OGLE-2015-BLG-0845 revealed microlensing parallax and xallarap effects
Direct measurement of lens object's mass: low-mass M-dwarf with a mass of $0.14 \pm 0.05 M_{\odot}$ located at $7.6 \pm 1.0$ kpc from Earth
Source binary system: late F-type subgiant and K-type dwarf weighing $\sim1.2 M_{\odot}$ and $\sim 0.9 M_{\odot}$ respectively, orbital period of $70 \pm 10$ days
Significance of binary systems in microlensing studies highlighted by this event
Xallarap effect application in accurately determining masses of microlenses may not be as rare as previously thought

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Original abstract

, , , , In the analysis of the microlensing event OGLE-2015-BLG-0845, researchers detected both the microlensing parallax and xallarap effects. The former was observed through simultaneous ground and Spitzer observations, while the latter was attributed to the orbital motion of the source star in a nearby binary system. These combined effects allowed for a direct measurement of the lens object's mass, revealing a low-mass M-dwarf with a mass of $0.14 \pm 0.05 M_{\odot}$ located at a distance of $7.6 \pm 1.0$ kpc from Earth. The source binary comprises a late F-type subgiant and a K-type dwarf weighing approximately $\sim1.2 M_{\odot}$ and $\sim 0.9 M_{\odot}$ respectively, with an orbital period of $70 \pm 10$ days. Notably, OGLE-2015-BLG-0845 stands out as the first single-lens event where the lens mass was determined through the binarity of the source star, underscoring the potential significance of binary systems in microlensing studies. Furthermore, this study sheds light on the application of the xallarap effect in accurately determining masses of microlenses, suggesting that this phenomenon may not be as rare as previously thought. The methodology employed here could also prove valuable in identifying isolated dark lenses in future observations. Overall, these findings contribute to our understanding of gravitational microlensing events and highlight new avenues for studying celestial objects through their gravitational interactions.

Introduction

In the world of astrophysics, gravitational microlensing has emerged as a powerful tool for studying celestial objects. This phenomenon occurs when a massive object, such as a star or planet, passes in front of a more distant light source. The gravity of the foreground object bends and magnifies the light from the background source, creating a temporary increase in brightness that can be observed by telescopes on Earth.

One particular microlensing event, OGLE-2015-BLG-0845, caught the attention of researchers due to its unique characteristics.

The Microlensing Parallax Effect

The first aspect that stood out to researchers was the detection of both microlensing parallax and xallarap effects in OGLE-2015-BLG-0845. The former is an effect where observers on Earth see different magnification patterns depending on their location relative to the lensing event. This allows for precise measurements of both the distance and mass of the lens object.

To detect this effect, simultaneous observations were conducted using ground-based telescopes and NASA's Spitzer Space Telescope. By combining these data sets, researchers were able to accurately measure not only the distance but also the mass of the lens object.

The Lens Object

This finding is significant because it is one of the few microlensing events where the lens mass was directly measured through the microlensing parallax effect.

Furthermore, this M-dwarf is located at a distance of $7.6 \pm 1.0$ kpc from Earth, making it one of the most distant microlenses ever observed. This adds to our understanding of the distribution and properties of low-mass stars in our galaxy.

The Xallarap Effect

The second aspect that researchers were able to detect in OGLE-2015-BLG-0845 was the xallarap effect. This phenomenon occurs when the source star is part of a binary system and its orbital motion causes additional changes in magnification patterns during a microlensing event.

Through their analysis, they determined that this binary comprises a late F-type subgiant and a K-type dwarf with masses estimated at $\sim1.2 M_{\odot}$ and $\sim 0.9 M_{\odot}$ respectively.

Implications for Future Studies

One significant implication of this study is that it highlights how important binary systems can be in microlensing studies. In previous cases, researchers have often assumed that single-lens events are caused by isolated objects without considering potential binarity effects on their observations.

However, OGLE-2015-BLG-0845 stands out as an example where binarity played a crucial role in accurately determining both distance and mass measurements for the lens object. This suggests that future studies should consider binarity as a factor when analyzing microlensing events.

This phenomenon may not be as rare as previously thought, and the methodology employed in this study could prove valuable in identifying isolated dark lenses in future observations.

Conclusion

Through their detection of both the microlensing parallax and xallarap effects, they were able to accurately measure the distance and mass of the lens object, revealing a low-mass M-dwarf located at a significant distance from Earth.

Furthermore, this study highlights the importance of considering binarity in microlensing studies and suggests that xallarap effects may be more common than previously thought. Overall, these findings contribute to our understanding of celestial objects through their gravitational interactions and open up new avenues for future research in this field.

Created on 22 Apr. 2024

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OGLE-2015-BLG-0845L: A low-mass M dwarf from the microlensing parallax and xallarap effects

The essentials

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Definitions

Introduction

The Microlensing Parallax Effect

The Lens Object

The Xallarap Effect

Implications for Future Studies

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