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<i>SPITZER</i>MICROLENS MEASUREMENT OF A MASSIVE REMNANT IN A WELL-SEPARATED BINARY
Shvartzvald, Y.,Udalski, A.,Gould, A.,Han, C.,Bozza, V.,Friedmann, M.,Hundertmark, M.,Beichman, C.,Bryden, G.,Novati, S. Calchi,Carey, S.,Fausnaugh, M.,Gaudi, B. S.,Henderson, C. B.,Kerr, T.,Pogge, R. IOP Publishing 2015 The Astrophysical journal Vol.814 No.2
<P>We report the detection and mass measurement of a binary lens OGLE-2015-BLG-1285La, b, with the more massive component having M-1 > 1.35M(circle dot) (80% probability). A main-sequence star in this mass range is ruled out by limits on blue light, meaning that a primary in this mass range must be a neutron star (NS) or black hole (BH). The system has a projected separation r(perpendicular to) = 6.1 +/- 0.4 AU and lies in the Galactic bulge. These measurements are based on the 'microlens parallax' effect, i.e., comparing the microlensing light curve as seen from Spitzer, which lay at 1.25 AU projected from Earth, to the light curves from four ground-based surveys, three in the optical and one in the near-infrared. Future adaptive optics imaging of the companion by 30 m class telescopes will yield a much more accurate measurement of the primary mass. This discovery both opens the path and defines the challenges to detecting and characterizing BHs and NSs in wide binaries, with either dark or luminous companions. In particular, we discuss lessons that can be applied to future Spitzer and Kepler K2 microlensing parallax observations.</P>
MOA-2011-BLG-322Lb: a 'second generation survey' microlensing planet
Shvartzvald, Y.,Maoz, D.,Kaspi, S.,Sumi, T.,Udalski, A.,Gould, A.,Bennett, D. P.,Han, C.,Abe, F.,Bond, I. A.,Botzler, C. S.,Freeman, M.,Fukui, A.,Fukunaga, D.,Itow, Y.,Koshimoto, N.,Ling, C. H.,Masuda Oxford University Press 2014 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.439 No.1
Shvartzvald, Y.,Bryden, G.,Gould, A.,Henderson, C. B.,Howell, S. B.,Beichman, C. American Institute of Physics 2017 The Astronomical journal Vol.153 No.2
<P>Optical microlensing surveys are restricted from detecting events near the Galactic plane and center, where the event rate is thought to be the highest due to the high optical extinction of these fields. In the near-infrared (NIR), however, the lower extinction leads to a corresponding increase in event detections and is a primary driver for the wavelength coverage of the WFIRST microlensing survey. During the 2015 and 2016 bulge observing seasons, we conducted NIR microlensing surveys with UKIRT in conjunction with and in support of the Spitzer and Kepler microlensing campaigns. Here, we report on five highly extinguished (A(H) = 0.81-1.97), low-Galactic latitude (-0.98 <= b <= -0.36) microlensing events discovered from our 2016 survey. Four of them were monitored with an hourly cadence by optical surveys but were not reported as discoveries, likely due to the high extinction. Our UKIRT surveys and suggested future NIR surveys enable the first measurement of the microlensing event rate in the NIR. This wavelength regime overlaps with the bandpass of the filter in which the WFIRST microlensing survey will conduct its highest-cadence observations, making this event rate derivation critically important for optimizing its yield.</P>
Shvartzvald, Y.,Li, Z.,Udalski, A.,Gould, A.,Sumi, T.,Street, R. A.,Novati, S. Calchi,Hundertmark, M.,Bozza, V.,Beichman, C.,Bryden, G.,Carey, S.,Drummond, J.,Fausnaugh, M.,Gaudi, B. S.,Henderson, C. American Astronomical Society 2016 The Astrophysical journal Vol.831 No.2
<P>Simultaneous observations of microlensing events from multiple locations allow for the breaking of degeneracies between the physical properties of the lensing system, specifically by exploring different regions of the lens plane and by directly measuring the 'microlens parallax.' We report the discovery of a 30-65M(J) brown dwarf orbiting a K dwarf in the microlensing event OGLE-2015-BLG-1319. The system is located at a distance of similar to 5 kpc toward the Galactic Bulge. The event was observed by several ground-based groups as well as by Spitzer and Swift, allowing a measurement of the physical properties. However, the event is still subject to an eight-fold degeneracy, in particular the well-known close-wide degeneracy, and thus the projected separation between the two lens components is either similar to 0.25 au or similar to 45 au. This is the first microlensing event observed by Swift, with the UVOT camera. We study the region of microlensing parameter space to which Swift is sensitive, finding that though Swift could not measure the microlens parallax with respect to ground-based observations for this event, it can be important for other events. Specifically, it is important for detecting nearby brown dwarfs and free-floating planets in high magnification events.</P>
An Earth-mass Planet in a 1 au Orbit around an Ultracool Dwarf
Shvartzvald, Y.,Yee, J. C.,Novati, S. Calchi,Gould, A.,Lee, C.-U.,Beichman, C.,Bryden, G.,Carey, S.,Gaudi, B. S.,Henderson, C. B.,Zhu, W.,Albrow, M. D.,Cha, S.-M.,Chung, S.-J.,Han, C.,Hwang, K.-H.,Jun American Astronomical Society 2017 ASTROPHYSICAL JOURNAL LETTERS - Vol.840 No.1
OGLE-2016-BLG-1190Lb: The First<i>Spitzer</i>Bulge Planet Lies Near the Planet/Brown-dwarf Boundary
Ryu, Y.-H.,Yee, J. C.,Udalski, A.,Bond, I. A.,Shvartzvald, Y.,Zang, W.,Jaimes, R. Figuera,Jørgensen, U. G.,Zhu, W.,Huang, C. X.,Jung, Y. K.,Albrow, M. D.,Chung, S.-J.,Gould, A.,Han, C.,Hwang, K.-H.,Sh American Astronomical Society 2018 The Astronomical journal Vol.155 No.1
<P>We report the discovery of OGLE-2016-BLG-1190Lb, which is likely to be the first Spitzer microlensing planet in the Galactic bulge/ bar, an assignation that can be confirmed by two epochs of high-resolution imaging of the combined source-lens baseline object. The planet's mass, M-p = 13.4 +/- 0.9 M-J, places it right at the deuteriumburning limit, i. e., the conventional boundary between 'planets' and 'brown dwarfs.' Its existence raises the question of whether such objects are really ' planets' (formed within the disks of their hosts) or 'failed stars' (lowmass objects formed by gas fragmentation). This question may ultimately be addressed by comparing disk and bulge/bar planets, which is a goal of the Spitzer microlens program. The host is a G dwarf, M-host = 0.89. +/- 0.07 M-circle dot, and the planet has a semimajor axis a similar to 2.0 au. We use Kepler K2 Campaign 9 microlensing data to break the lens-mass degeneracy that generically impacts parallax solutions from Earth-Spitzer observations alone, which is the first successful application of this approach. The microlensing data, derived primarily from near-continuous, ultradense survey observations from OGLE, MOA, and three KMTNet telescopes, contain more orbital information than for any previous microlensing planet, but not quite enough to accurately specify the full orbit. However, these data do permit the first rigorous test of microlensing orbital-motion measurements, which are typically derived from data taken over < 1% of an orbital period.</P>
OGLE-2017-BLG-0039: Microlensing Event with Light from a Lens Identified from Mass Measurement
Han, C.,Jung, Y. K.,Udalski, A.,Bond, I.,Bozza, V.,Albrow, M. D.,Chung, S.-J.,Gould, A.,Hwang, K.-H.,Kim, D.,Lee, C.-U.,Kim, H.-W.,Ryu, Y.-H.,Shin, I.-G.,Yee, J. C.,Shvartzvald, Y.,Cha, S.-M.,Kim, S.- American Astronomical Society 2018 The Astrophysical journal Vol.867 No.2
Two Jupiter-mass Planets Discovered by the KMTNet Survey in 2017
Shin, I.-G.,Ryu, Y.-H.,Yee, J. C.,Gould, A.,Albrow, M. D.,Chung, S.-J.,Han, C.,Hwang, K.-H.,Jung, Y. K.,Shvartzvald, Y.,Zang, W.,Lee, C.-U.,Cha, S.-M.,Kim, D.-J.,Kim, H.-W.,Kim, S.-L.,Lee, Y.,Lee, D.- American Astronomical Society 2019 The Astronomical journal Vol.157 No.4
OGLE-2017-BLG-0173Lb: Low-mass-ratio Planet in a “Hollywood” Microlensing Event
Hwang, K.-H.,Udalski, A.,Shvartzvald, Y.,Ryu, Y.-H.,Albrow, M. D.,Chung, S.-J.,Gould, A.,Han, C.,Jung, Y. K.,Shin, I.-G.,Yee, J. C.,Zhu, W.,Cha, S.-M.,Kim, D.-J.,Kim, H.-W.,Kim, S.-L.,Lee, C.-U.,Lee, American Astronomical Society 2018 The Astronomical journal Vol.155 No.1
<P>We present microlensing planet OGLE-2017-BLG-0173Lb, with planet-host mass ratio of either q similar or equal to 2.5 x 10(-5) or q similar or equal to 6.5 x 10(-5), the lowest or among the lowest ever detected. The planetary perturbation is strongly detected, Delta chi(2) similar to 10000, because it arises from a bright (therefore, large) source passing over and enveloping the planetary caustic: a so-called 'Hollywood' event. The factor similar to 2.5 offset in q arises because of a previously unrecognized discrete degeneracy between Hollywood events in which the caustic is fully enveloped and those in which only one flank is enveloped, which we dub 'Cannae' and 'von Schlieffen,' respectively. This degeneracy is 'accidental' in that it arises from gaps in the data. Nevertheless, the fact that it appears in a Delta chi(2) = 10000 planetary anomaly is striking. We present a simple formalism to estimate the sensitivity of other Hollywood events to planets and show that they can lead to detections close to, but perhaps not quite reaching, the Earth/Sun mass ratio of 3 x 10(-6). This formalism also enables an analytic understanding of the factor similar to 2.5 offset in q between the Cannae and von Schlieffen solutions. The Bayesian estimates for the host mass, system distance, and planet-host projected separation are M = 0.39(-0.24)(+0.40) M circle dot, D-L = 4.8(-1.8)(+1.5) kpc, and a(perpendicular to) = 3.8 +/- 1.6 au, respectively. The two estimates of the planet mass are m(p) = 3.3(2.1)(+3.8) M circle plus and m(p) = 8(6)(+11) M circle plus. The measured lens-source relative proper motion mu = 6 mas yr(-1) will permit imaging of the lens in about 15 years or at first light on adaptive-optics imagers on next-generation telescopes. These will allow one to measure the host mass but probably will not be able to resolve the planet-host mass-ratio degeneracy.</P>