Abstract We report on the discovery and analysis of the planetary microlensing event OGLE-2019-BLG-1180 with a planet-to-star mass ratio q ∼ 0.003. The event OGLE-2019-BLG-1180 has unambiguous cusp-passing and caustic-crossing anomalies, which were caused by a wide planetary caustic with s ≃ 2, where s is the star–planet separation in units of the angular Einstein radius θ E . Thanks to well-covered anomalies by the Korea Micorolensing Telescope Network (KMTNet), we measure both the angular Einstein radius and the microlens parallax in spite of a relatively short event timescale of t E = 28 days. However, because of a weak constraint on the parallax, we conduct a Bayesian analysis to estimate the physical lens parameters. We find that the lens system is a super-Jupiter-mass planet of M p = 1.75 − 0.51 + 0.53 M J orbiting a late-type star of M h = 0.55 − 0.26 + 0.27 M ⊙ at a distance D L = 6.1 − 1.3 + 0.9 kpc . The projected star–planet separation is a ⊥ = 5.19 − 1.23 + 0.90 au , which means that the planet orbits at about four times the snow line of the host star. Considering the relative lens–source proper motion of μ rel = 6 mas yr −1 , the lens will be separated from the source by 60 mas in 2029. At that time one can measure the lens flux from adaptive optics imaging of Keck or a next-generation 30 m class telescope. OGLE-2019-BLG-1180Lb represents a growing population of wide-orbit planets detected by KMTNet, so we also present a general investigation into prospects for further expanding the sample of such planets.

Jupiter (rocket family)

Star (game theory)

Orbit (dynamics)

Jupiter mass

10.3847/1538-3881/ad0723

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Analysis of the full Spitzer microlensing sample I: Dark remnant candidates and Gaia predictions

arXiv (Cornell University) (2024)

K. Rybicki Yossi Shvartzvald Jennifer C. Yee S. Calchi Novati E. O. Ofek

In the pursuit of understanding the population of stellar remnants within the Milky Way, we analyze the sample of $\sim 950$ microlensing events observed by the Spitzer Space Telescope between 2014 and 2019. In this study we focus on a sub-sample of nine microlensing events, selected based on their long timescales, small microlensing parallaxes and joint observations by the Gaia mission, to increase the probability that the chosen lenses are massive and the mass is measurable. Among the selected events we identify lensing black holes and neutron star candidates, with potential confirmation through forthcoming release of the Gaia time-series astrometry in 2026. Utilizing Bayesian analysis and Galactic models, along with the Gaia Data Release 3 proper motion data, four good candidates for dark remnants were identified: OGLE-2016-BLG-0293, OGLE-2018-BLG-0483, OGLE-2018-BLG-0662, and OGLE-2015-BLG-0149, with lens masses of $2.98^{+1.75}_{-1.28}~M_{\odot}$, $4.65^{+3.12}_{-2.08}~M_{\odot}$, $3.15^{+0.66}_{-0.64}~M_{\odot}$ and $1.4^{+0.75}_{-0.55}~M_{\odot}$, respectively. Notably, the first two candidates are expected to exhibit astrometric microlensing signals detectable by Gaia, offering the prospect of validating the lens masses. The methodologies developed in this work will be applied to the full Spitzer microlensing sample, populating and analyzing the time-scale ($t_{\rm E}$) vs. parallax ($\pi_{\rm E}$) diagram to derive constraints on the population of lenses in general and massive remnants in particular.

Gravitational microlensing

Sample (material)

10.48550/arxiv.2407.13740

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KIC 4739791: A NEW R CMa-TYPE ECLIPSING BINARY WITH A PULSATING COMPONENT

The Astronomical Journal (2016)

Jae Woo Lee Seung‐Lee Kim Kyeongsoo Hong Jae‐Rim Koo Chung‐Uk Lee

The Kepler light curve of KIC 4739791 exhibits partial eclipses, the inverse O'Connell effect, and multiperiodic pulsations. Including a starspot on either of the binary components, the light-curve synthesis indicates that KIC 4739791 is in detached or semi-detached configuration with both a short orbital period and a low mass ratio. Multiple frequency analyses were performed in the light residuals after subtracting the binarity effects from the original Kepler data. We detected 14 frequencies: 6 in the low-frequency region (0.1−2.3 days−1) and 8 in the high-frequency region (18.2−22.0 days−1). Among these, six high frequencies with amplitudes of 0.62−1.97 mmag were almost constant over time for 200 days. Their pulsation periods and pulsation constants are in the ranges of 0.048−0.054 days and 0.025−0.031 days, respectively. In contrast, the other frequencies may arise from the alias effects caused by the orbital frequency or combination frequencies. We propose that KIC 4739791 is a short-period R CMa binary with the lowest mass ratio in the known classical Algols and that its primary component is a δ Sct pulsating star. Only four R CMa stars have been identified, three of which exhibit δ Sct-type oscillations. These findings make KIC 4739791 an attractive target for studies of stellar interior structure and evolution.

Starspot

Mass ratio

Orbital period

Low Mass

Star (game theory)

10.3847/0004-6256/151/2/25

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Citations (15)

ZTF20acozryr/AT2020yxz (GRB 201103B): Flattening of the optical light curve

GRB Coordinates Network (2020)

Gregory S. H. Paek Myungshin Im Joonho Kim Gu Lim Mankeun Jeong

Flattening

Source

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OGLE-2023-BLG-0836L: The sixth microlensing planet in a binary stellar system

arXiv (Cornell University) (2024)

Cheongho Han A. Udalski Youn Kil Jung Andrew Gould Doeon Kim

Light curves of microlensing events occasionally deviate from the smooth and symmetric form of a single-lens single-source event. While most of these anomalous events can be accounted for by employing a binary-lens single-source (2L1S) or a single-lens binary-source (1L2S) framework, it is established that a small fraction of events remain unexplained by either of these interpretations. We carry out a project in which data collected by high-cadence microlensing surveys were reinvestigated with the aim of uncovering the nature of anomalous lensing events with no proposed 2L1S or 1L2S models. From the project, we find that the anomaly appearing in the lensing event OGLE-2023-BLG-0836 cannot be explained by the usual interpretations and conduct a comprehensive analysis of the event. From thorough modeling of the light curve under sophisticated lens-system configurations, we have arrived at the conclusion that a triple-mass lens system is imperative to account for the anomaly features observed in the lensing light curve. From the Bayesian analysis using the measured observables of the event time scale and angular Einstein radius, we determine that the least massive component of the lens has a planetary mass of $4.36^{+2.35}_{-2.18}~M_{\rm J}$. This planet orbits within a stellar binary system composed of two stars with masses $0.71^{+0.38}_{-0.36}~M_\odot$ and $0.56^{+0.30}_{-0.28}~M_\odot$. This lensing event signifies the sixth occurrence of a planetary microlensing system in which a planet belongs to a stellar binary system.

Gravitational microlensing

10.48550/arxiv.2402.08116

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Citations (1)

Systematic KMTNet Planetary Anomaly Search. XI. Complete Sample of 2016 Subprime Field Planets

The Astronomical Journal (2024)

In-Gu Shin Jennifer C. Yee Weicheng Zang Cheongho Han Hongjing Yang

Abstract Following Shin et al. (2023b), which is a part of the “Systematic KMTNet Planetary Anomaly Search” series (i.e., a search for planets in the 2016 KMTNet prime fields), we conduct a systematic search of the 2016 KMTNet subprime fields using a semi-machine-based algorithm to identify hidden anomalous events missed by the conventional by-eye search. We find four new planets and seven planet candidates that were buried in the KMTNet archive. The new planets are OGLE-2016-BLG-1598Lb, OGLE-2016-BLG-1800Lb, MOA-2016-BLG-526Lb, and KMT-2016-BLG-2321Lb, which show typical properties of microlensing planets, i.e., giant planets orbit M-dwarf host stars beyond their snow lines. For the planet candidates, we find planet/binary or 2L1S/1L2S degeneracies, which are an obstacle to firmly claiming planet detections. By combining the results of Shin et al. (2023b) and this work, we find a total of nine hidden planets, which is about half the number of planets discovered by eye in 2016. With this work, we have met the goal of the systematic search series for 2016, which is to build a complete microlensing planet sample. We also show that our systematic searches significantly contribute to completing the planet sample, especially for planet/host mass ratios smaller than 10 −3 , which were incomplete in previous by-eye searches of the KMTNet archive.

Gravitational microlensing

10.3847/1538-3881/ad3ba3

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Citations (1)

WEBT and XMM-Newton observations of 3C 454.3 during the post-outburst phase

Astronomy and Astrophysics (2007)

C. M. Raiteri M. Villata V. M. Larionov T. Pursimo M. Ibrahimov

The blazar 3C 454.3 underwent an unprecedented optical outburst in spring 2005. This was first followed by a mm and then by a cm radio outburst, which peaked in February 2006. We report on follow-up observations by the WEBT to study the multiwavelength emission in the post-outburst phase. XMM-Newton observations on July and December 2006 added information on the X-ray and UV fluxes. The source was in a faint state. The radio flux at the higher frequencies showed a fast decreasing trend, which represents the tail of the big radio outburst. It was followed by a quiescent state, common at all radio frequencies. In contrast, moderate activity characterized the NIR and optical light curves, with a progressive increase of the variability amplitude with increasing wavelength. We ascribe this redder-when-brighter behaviour to the presence of a "little blue bump" due to line emission from the broad line region, which is clearly visible in the source SED during faint states. Moreover, the data from the XMM-Newton OM reveal a rise of the SED in the UV, suggesting the existence of a "big blue bump" due to thermal emission from the accretion disc. The X-ray spectra are well fitted with a power-law model with photoelectric absorption, possibly larger than the Galactic one. However, the comparison with previous X-ray observations would imply that the amount of absorbing matter is variable. Alternatively, the intrinsic X-ray spectrum presents a curvature, which may depend on the X-ray brightness. In this case, two scenarios are possible.

10.1051/0004-6361:20078289

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Citations (93)

Analysis of the Full Spitzer Microlensing Sample. I. Dark Remnant Candidates and Gaia Predictions

The Astrophysical Journal (2024)

K. Rybicki Yossi Shvartzvald Jennifer C. Yee S. Calchi Novati E. O. Ofek

Abstract In the pursuit of understanding the population of stellar remnants within the Milky Way, we analyze the sample of ∼950 microlensing events observed by the Spitzer Space Telescope between 2014 and 2019. In this study we focus on a subsample of nine microlensing events, selected based on their long timescales, small microlensing parallaxes, and joint observations by the Gaia mission, to increase the probability that the chosen lenses are massive and the mass is measurable. Among the selected events we identify lensing black holes and neutron star candidates, with potential confirmation through forthcoming release of the Gaia time-series astrometry in 2026. Utilizing Bayesian analysis and Galactic models, along with the Gaia Data Release 3 proper-motion data, four good candidates for dark remnants were identified: OGLE-2016-BLG-0293, OGLE-2018-BLG-0483, OGLE-2018-BLG-0662, and OGLE-2015-BLG-0149, with lens masses of 3.0 − 1.3 + 1.8 M ⊙ , 4.7 − 2.1 + 3.2 M ⊙ , 3.15 − 0.64 + 0.66 M ⊙ and 1.40 − 0.55 + 0.75 M ⊙ , respectively. Notably, the first two candidates are expected to exhibit astrometric microlensing signals detectable by Gaia, offering the prospect of validating the lens masses. The methodologies developed in this work will be applied to the full Spitzer microlensing sample, populating and analyzing the timescale ( t E ) versus parallax ( π E ) diagram to derive constraints on the population of lenses in general and massive remnants in particular.

Gravitational microlensing

10.3847/1538-4357/ad7bb1

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Earth Hunter - Korean Microlensing Telescope Project

한국천문학회보 (2008)

Byeong-Gon Park Seung-Lee Kim Chung‐Uk Lee Jae Wook Lee Cheongho Han

Gravitational microlensing

Source

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MOA-2010-BLG-523: “FAILED PLANET” = RS CVn STAR

The Astrophysical Journal (2013)

Andrew Gould Jennifer C. Yee I. A. Bond A. Udalski Cheongho Han

The Galactic bulge source MOA-2010-BLG-523S exhibited short-term deviations from a standard microlensing light curve near the peak of an Amax ∼ 265 high-magnification microlensing event. The deviations originally seemed consistent with expectations for a planetary companion to the principal lens. We combine long-term photometric monitoring with a previously published high-resolution spectrum taken near peak to demonstrate that this is an RS CVn variable, so that planetary microlensing is not required to explain the light-curve deviations. This is the first spectroscopically confirmed RS CVn star discovered in the Galactic bulge.

Gravitational microlensing

Star (game theory)

Variable star

10.1088/0004-637x/763/2/141

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Citations (15)