http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
<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
MOA-2011-BLG-293Lb: A TEST OF PURE SURVEY MICROLENSING PLANET DETECTIONS
Yee, J. C.,Shvartzvald, Y.,Gal-Yam, A.,Bond, I. A.,Udalski, A.,Kozłowski, S.,Han, C.,Gould, A.,Skowron, J.,Suzuki, D.,Abe, F.,Bennett, D. P.,Botzler, C. S.,Chote, P.,Freeman, M.,Fukui, A.,Furusawa, K. IOP Publishing 2012 The Astrophysical journal Vol.755 No.2
<P>Because of the development of large-format, wide-field cameras, microlensing surveys are now able to monitor millions of stars with sufficient cadence to detect planets. These new discoveries will span the full range of significance levels including planetary signals too small to be distinguished from the noise. At present, we do not understand where the threshold is for detecting planets. MOA-2011-BLG-293Lb is the first planet to be published from the new surveys, and it also has substantial follow-up observations. This planet is robustly detected in survey+follow-up data (Delta chi(2) similar to 5400). The planet/host mass ratio is q = (5.3 similar to 0.2) x 10(-3). The best-fit projected separation is s = 0.548 +/- 0.005 Einstein radii. However, due to the s <-> s(-1) degeneracy, projected separations of s-1 are only marginally disfavored at Delta chi(2) = 3. A Bayesian estimate of the host mass gives M-L = 0.43(-0.17)(+0.27) M-circle dot, with a sharp upper limit of M-L < 1.2 M-circle dot from upper limits on the lens flux. Hence, the planet mass is m(p) = 2.4(-0.9)(+1.5) M-Jup, and the physical projected separation is either r(perpendicular to) similar or equal to 1.0 AU or r(perpendicular to) similar or equal to 3.4 AU. We show that survey data alone predict this solution and are able to characterize the planet, but the Delta chi(2) is much smaller (Delta chi(2) similar to 500) than with the follow-up data. The Delta chi(2) for the survey data alone is smaller than for any other securely detected planet. This event suggests a means to probe the detection threshold, by analyzing a large sample of events like MOA-2011-BLG-293, which have both follow-up data and high-cadence survey data, to provide a guide for the interpretation of pure survey microlensing data.</P>
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>
OGLE-2011-BLG-0265Lb: A JOVIAN MICROLENSING PLANET ORBITING AN M DWARF
Skowron, J.,Shin, I.-G.,Udalski, A.,Han, C.,Sumi, T.,Shvartzvald, Y.,Gould, A.,Dominis Prester, D.,Street, R. A.,Jørgensen, U. G.,Bennett, D. P.,Bozza, V.,Szymań,ski, M. K.,Kubiak, M.,Pietrzy IOP Publishing 2015 The Astrophysical journal Vol.804 No.1
<P>We report the discovery of a Jupiter-mass planet orbiting an M-dwarf star that gave rise to the microlensing event OGLE-2011-BLG-0265. Such a system is very rare among known planetary systems and thus the discovery is important for theoretical studies of planetary formation and evolution. High-cadence temporal coverage of the planetary signal, combined with extended observations throughout the event, allows us to accurately model the observed light curve. However, the final microlensing solution remains degenerate, yielding two possible configurations of the planet and the host star. In the case of the preferred solution, the mass of the planet is M-p = 0.9 +/- 0.3 M-J, and the planet is orbiting a star with a mass M = 0.22 +/- 0.06 M-circle dot. The second possible configuration (2 sigma away) consists of a planet with M-p = 0.6 +/- 0.3M(J) and host star with M = 0.14 +/- 0.06M(circle dot). The system is located in the Galactic disk 3-4 kpc toward the Galactic bulge. In both cases, with an orbit size of 1.5-2.0 AU, the planet is a 'cold Jupiter'-located well beyond the 'snow line' of the host star. Currently available data make the secure selection of the correct solution difficult, but there are prospects for lifting the degeneracy with additional follow-up observations in the future, when the lens and source star separate.</P>