Browsing by Author "Barry RK"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    An Isolated Stellar-mass Black Hole Detected through Astrometric Microlensing
    (IOP Publishing on behalf of the American Astronomical Society, 2022-07-06) Sahu KC; Anderson J; Casertano S; Bond HE; Udalski A; Dominik M; Calamida A; Bellini A; Brown TM; Rejkuba M; Bajaj V; Kains N; Ferguson HC; Fryer CL; Yock P; Mróz P; Kozłowski S; Pietrukowicz P; Poleski R; Skowron J; Soszyński I; Szymański MK; Ulaczyk K; Wyrzykowski Ł; Barry RK; Bennett DP; Bond IA; Hirao Y; Silva SI; Kondo I; Koshimoto N; Ranc C; Rattenbury NJ; Sumi T; Suzuki D; Tristram PJ; Vandorou A; Beaulieu J-P; Marquette J-B; Cole A; Fouqué P; Hill K; Dieters S; Coutures C; Dominis-Prester D; Bennett C; Bachelet E; Menzies J; Albrow M; Pollard K; Gould A; Yee JC; Allen W; Almeida LA; Christie G; Drummond J; Gal-Yam A; Gorbikov E; Jablonski F; Lee C-U; Maoz D; Manulis I; McCormick J; Natusch T; Pogge RW; Shvartzvald Y; Jørgensen UG; Alsubai KA; Andersen MI; Bozza V; Novati SC; Burgdorf M; Hinse TC; Hundertmark M; Husser T-O; Kerins E; Longa-Peña P; Mancini L; Penny M; Rahvar S; Ricci D; Sajadian S; Skottfelt J; Snodgrass C; Southworth J; Tregloan-Reed J; Wambsganss J; Wertz O; Tsapras Y; Street RA; Bramich DM; Horne K; Steele IA
    We report the first unambiguous detection and mass measurement of an isolated stellar-mass black hole (BH). We used the Hubble Space Telescope (HST) to carry out precise astrometry of the source star of the long-duration (t E ≃ 270 days), high-magnification microlensing event MOA-2011-BLG-191/OGLE-2011-BLG-0462 (hereafter designated as MOA-11-191/OGLE-11-462), in the direction of the Galactic bulge. HST imaging, conducted at eight epochs over an interval of 6 yr, reveals a clear relativistic astrometric deflection of the background star's apparent position. Ground-based photometry of MOA-11-191/OGLE-11-462 shows a parallactic signature of the effect of Earth's motion on the microlensing light curve. Combining the HST astrometry with the ground-based light curve and the derived parallax, we obtain a lens mass of 7.1 ± 1.3 M ⊙ and a distance of 1.58 ± 0.18 kpc. We show that the lens emits no detectable light, which, along with having a mass higher than is possible for a white dwarf or neutron star, confirms its BH nature. Our analysis also provides an absolute proper motion for the BH. The proper motion is offset from the mean motion of Galactic disk stars at similar distances by an amount corresponding to a transverse space velocity of �1/445 km s-1, suggesting that the BH received a "natal kick"from its supernova explosion. Previous mass determinations for stellar-mass BHs have come from radial velocity measurements of Galactic X-ray binaries and from gravitational radiation emitted by merging BHs in binary systems in external galaxies. Our mass measurement is the first for an isolated stellar-mass BH using any technique.
  • Thumbnail Image
    Item
    Four sub-Jovian-mass planets detected by high-cadence microlensing surveys
    (EDP Sciences on behalf of the European Southern Observatory, 2022-08-05) Han C; Kim D; Gould A; Udalski A; Bond IA; Bozza V; Jung YK; Albrow MD; Chung S-J; Hwang K-H; Ryu Y-H; Shin I-G; Shvartzvald Y; Yee JC; Zang W; Cha S-M; Kim D-J; Kim S-L; Lee C-U; Lee D-J; Lee Y; Park B-G; Pogge RW; Mróz P; Szymański MK; Skowron J; Poleski R; Soszyński I; Pietrukowicz P; Kozaowski S; Ulaczyk K; Rybicki KA; Iwanek P; Abe F; Barry RK; Bennett DP; Bhattacharya A; Fujii H; Fukui A; Hirao Y; Itow Y; Kirikawa R; Koshimoto N; Kondo I; Matsubara Y; Matsumoto S; Miyazaki S; Muraki Y; Olmschenk G; Okamura A; Ranc C; Rattenbury NJ; Satoh Y; Silva SI; Sumi T; Suzuki D; Toda T; Tristram PJ; Vandorou A; Yama H
    Aims. With the aim of finding short-term planetary signals, we investigated the data collected from current high-cadence microlensing surveys. Methods. From this investigation, we found four planetary systems with low planet-to-host mass ratios, including OGLE-2017-BLG-1691L, KMT-2021-BLG-0320L, KMT-2021-BLG-1303L, and KMT-2021-BLG-1554L. Despite the short durations, ranging from a few hours to a couple of days, the planetary signals were clearly detected by the combined data of the lensing surveys. We found that three of the planetary systems have mass ratios on the order of 10-4 and the other has a mass ratio that is slightly greater than 10-3. Results. The estimated masses indicate that all discovered planets have sub-Jovian masses. The planet masses of KMT-2021-BLG-0320Lb, KMT-2021-BLG-1303Lb, and KMT-2021-BLG-1554Lb correspond to ∼0.10, ∼0.38, and ∼0.12 times the mass of the Jupiter, and the mass of OGLE-2017-BLG-1691Lb corresponds to that of the Uranus. The estimated mass of the planet host KMT-2021-BLG-1554L, Mhost ∼ 0.08 M⊙, corresponds to the boundary between a star and a brown dwarf. Besides this system, the host stars of the other planetary systems are low-mass stars with masses in the range of ∼[0.3-0.6] M⊙. The discoveries of the planets fully demonstrate the capability of the current high-cadence microlensing surveys in detecting low-mass planets.
  • Thumbnail Image
    Item
    KMT-2021-BLG-1077L: The fifth confirmed multiplanetary system detected by microlensing
    (EDP Sciences on behalf of the European Southern Observatory, 2022-06-20) Han C; Gould A; Bond IA; Jung YK; Albrow MD; Chung S-J; Hwang K-H; Ryu Y-H; Shin I-G; Shvartzvald Y; Yee JC; Zang W; Cha S-M; Kim D-J; Kim S-L; Lee C-U; Lee D-J; Lee Y; Park B-G; Pogge RW; Kim D; Abe F; Barry RK; Bennett DP; Bhattacharya A; Fujii H; Fukui A; Hirao Y; Itow Y; Kirikawa R; Koshimoto N; Kondo I; Matsubara Y; Matsumoto S; Miyazaki S; Muraki Y; Olmschenk G; Okamura A; Ranc C; Rattenbury NJ; Satoh Y; Silva SI; Sumi T; Suzuki D; Toda T; Tristram PJ; Vandorou A; Yama H
    Aims. The high-magnification microlensing event KMT-2021-BLG-1077 exhibits a subtle and complex anomaly pattern in the region around the peak. We analyze the lensing light curve of the event with the aim of revealing the nature of the anomaly. Methods. We test various models in combination with several interpretations: that the lens is a binary (2L1S), the source is a binary (1L2S), both the lens and source are binaries (2L2S), or the lens is a triple system (3L1S). We search for the best-fit models under the individual interpretations of the lens and source systems. Results. We find that the anomaly cannot be explained by the usual three-body (2L1S and 1L2S) models. The 2L2S model improves the fit compared to the three-body models, but it still leaves noticeable residuals. On the other hand, the 3L1S interpretation yields a model explaining all the major anomalous features in the lensing light curve. According to the 3L1S interpretation, the estimated mass ratios of the lens companions to the primary are ~1.56 A - 10a- 3 and ~1.75 A - 10a- 3, which correspond to ~1.6 and ~1.8 times the Jupiter/Sun mass ratio, respectively, and therefore the lens is a multiplanetary system containing two giant planets. With the constraints of the event time-scale and angular Einstein radius, it is found that the host of the lens system is a low-mass star of mid-to-late M spectral type with amass of Mh = 0.14a- 0.07+0.19 MI, and it hosts two gas giant planets with masses of Mp1 = 0.22a- 0.12+0.31 MJ and Mp2 = 0.25a- 0.13+0.35. The planets lie beyond the snow line of the host with projected separations of aap1 = 1.26a- 1.08+1.41 AU and aap2 = 0.93a- 0.80+1.05 AU. The planetary system resides in the Galactic bulge at a distance of DL = 8.24a- 1.16+1.02 kpc. The lens of the event is the fifth confirmed multiplanetary system detected by microlensing following OGLE-2006-BLG-109L, OGLE-2012-BLG-0026L, OGLE-2018-BLG-1011L, and OGLE-2019-BLG-0468L.
  • Thumbnail Image
    Item
    MOA-2020-BLG-208Lb: Cool Sub-Saturn-mass Planet within Predicted Desert
    (American Astronomical Society, 2023-03) Olmschenk G; Bennett DP; Bond IA; Zang W; Jung YK; Yee JC; Bachelet E; Abe F; Barry RK; Bhattacharya A; Fujii H; Fukui A; Hirao Y; Silva SI; Itow Y; Kirikawa R; Kondo I; Koshimoto N; Matsubara Y; Matsumoto S; Miyazaki S; Munford B; Muraki Y; Okamura A; Ranc C; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Toda T; Tristram PJ; Vandorou A; Yama H; Albrow MD; Cha S-M; Chung S-J; Gould A; Han C; Hwang K-H; Kim D-J; Kim H-W; Kim S-L; Lee C-U; Lee D-J; Lee Y; Park B-G; Pogge RW; Ryu Y-H; Shin I-G; Shvartzvald Y; Christie G; Cooper T; Drummond J; Green J; Hennerley S; McCormick J; Monard LAG; Natusch T; Porritt I; Tan T-G; Mao S; Maoz D; Penny MT; Zhu W; Bozza V; Cassan A; Dominik M; Hundertmark M; Jaimes RF; Kruszyńska K; Rybicki KA; Street RA; Tsapras Y; Wambsganss J; Wyrzykowski L; Zieliński P; Rau G
    We analyze the MOA-2020-BLG-208 gravitational microlensing event and present the discovery and characterization of a new planet, MOA-2020-BLG-208Lb, with an estimated sub-Saturn mass. With a mass ratio q=3.17-0.26+0.28×10-4, the planet lies near the peak of the mass-ratio function derived by the MOA collaboration and near the edge of expected sample sensitivity. For these estimates we provide results using two mass-law priors: one assuming that all stars have an equal planet-hosting probability, and the other assuming that planets are more likely to orbit around more massive stars. In the first scenario, we estimate that the lens system is likely to be a planet of mass mplanet=46-24+42M⊕ and a host star of mass Mhost=0.43-0.23+0.39M⊙, located at a distance DL=7.49-1.13+0.99kpc . For the second scenario, we estimate mplanet=69-34+37M⊕, Mhost=0.66-0.32+0.35M⊙, and DL=7.81-0.93+0.93kpc . The planet has a projected separation as a fraction of the Einstein ring radius s=1.3807-0.0018+0.0018 . As a cool sub-Saturn-mass planet, this planet adds to a growing collection of evidence for revised planetary formation models
  • Thumbnail Image
    Item
    OGLE-2014-BLG-0319: A Sub-Jupiter-mass Planetary Event Encountered Degeneracy with Different Mass Ratios and Lens-source Relative Proper Motions
    (IOP Publishing on behalf of the American Astronomical Society, 2022-03-01) Miyazaki S; Suzuki D; Udalski A; Koshimoto N; Bennett DP; Sumi T; Rattenbury N; Cheongho H; Abe F; Barry RK; Bhattacharya A; Bond IA; Fukui A; Fujii H; Hirao Y; Silva SI; Itow Y; Kirikawa R; Kondo I; Munford B; Matsubara Y; Matsumoto S; Muraki Y; Okamura A; Olmschenk G; Ranc C; Satoh YK; Toda T; Tristram PJ; Yama H; Yonehara A; Poleski R; Mróz P; Skowron J; Szymański MK; Soszyński I; Pietrukowicz P; Kozłowski S; Ulaczyk K; Wyrzykowski Ł
    We report the discovery of a sub-Jovian-mass planet, OGLE-2014-BLG-0319Lb. The characteristics of this planet will be added into a future extended statistical analysis of the Microlensing Observations in Astrophysics (MOA) collaboration. The planetary anomaly of the light curve is characterized by MOA and OGLE survey observations and results in three degenerate models with different planetary-mass ratios of q = (10.3, 6.6, 4.5) × 10-4. We find that the last two models require unreasonably small lens-source relative proper motions of μ rel ∼1 mas yr-1. Considering Galactic prior probabilities, we rule out these two models from the final result. We conduct a Bayesian analysis to estimate physical properties of the lens system using a Galactic model and find that the lens system is composed of a 0.49-0.27+0.35MJup sub-Jovian planet orbiting a 0.47-0.25+0.33M⊙ M dwarf near the Galactic Bulge. This analysis demonstrates that Galactic priors are useful to resolve this type of model degeneracy. This is important for estimating the mass-ratio function statistically. However, this method would be unlikely successful in shorter timescale events, which are mostly due to low-mass objects, like brown dwarfs or free-floating planets. Therefore, careful treatment is needed for estimating the mass-ratio function of the companions around such low-mass hosts, which only the microlensing can probe.