To the Revd. E. M. Walker (14 November 1922)

Hardy, Thomas

doi:10.1093/oseo/instance.00224858

Cited by 19 publications

(21 citation statements)

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“…However, in case of EROS BLG-2000-5, the second caustic crossing lasted four days, and therefore daily modulations of magnifications due to the Earth's rotation, offset according to the geographic position of each observatory, may become important, depending on the actual magnitude of the effect (See also Honma 1999 for a similar discussion on the short time scale magnification modulation observed from an Earth-orbiting satellite). Hardy & Walker (1995) and Gould & Andronov (1999) investigated effects of the terrestrial baseline parallax, for fold-caustic crossing microlensing events mainly focused on the instantaneous offsets due to the separation between observers. They argued that the timing difference of the trailing limb crossing for observations made from two different continents could be of the order of tens of seconds to a minute (Hardy & Walker 1995) and the magnifications near the end of exit-type caustic crossings could differ by as much as a few percent (Gould & Andronov 1999).…”

Section: Terrestrial Baseline Parallaxmentioning

confidence: 99%

“…Hardy & Walker (1995) and Gould & Andronov (1999) investigated effects of the terrestrial baseline parallax, for fold-caustic crossing microlensing events mainly focused on the instantaneous offsets due to the separation between observers. They argued that the timing difference of the trailing limb crossing for observations made from two different continents could be of the order of tens of seconds to a minute (Hardy & Walker 1995) and the magnifications near the end of exit-type caustic crossings could differ by as much as a few percent (Gould & Andronov 1999). Suppose that φ 2 is the angle at which the source crosses the caustic, A max is the magnification at the peak of the crossing, and A cc is the magnification right after the end of the crossing.…”

Section: Terrestrial Baseline Parallaxmentioning

confidence: 99%

“…All ideas proposed to measure rE are based on the detection of parallax effects (Refsdal 1966;Grieger, Kayser, & Refsdal 1986;Gould 1992Gould , 1995Gould, Miralda-Escudé, & Bahcall 1994;Hardy & Walker 1995;Holz & Wald 1996;Honma 1999;: either measuring the difference in the event as observed simultaneously from two or more locations, or observing the source from a frame that accelerates substantially during the course of the event. The prime example of the latter is the Earth's orbital motion (annual parallax).…”

Section: Introductionmentioning

confidence: 99%

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First Microlens Mass Measurement: PLANET Photometry of EROS BLG‐2000‐5

Albrow

Beaulieu

et al. 2002

ApJ

186

114

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We analyze PLANET photometric observations of the caustic-crossing binary-lens microlensing event, EROS BLG-2000-5, and find that modeling the observed light curve requires incorporation of the microlens parallax and the binary orbital motion. The projected Einstein radius (r E = 3.61 ± 0.11 AU) is derived from the measurement of the microlens parallax, and we are also able to infer the angular Einstein radius (θ E = 1.38 ± 0.12 mas) from the finite source effect on the light curve, combined with an estimate of the angular size of the source given by the source position in a color-magnitude diagram. The lens mass, M = 0.612 ± 0.057 M ⊙ , is found by combining these two quantities. This is the first time that parallax effects are detected for a caustic-crossing event and also the first time that the lens mass degeneracy has been completely broken through photometric monitoring alone. The combination ofr E and θ E also allows us to conclude that the lens lies in the near side of the disk, within 2.6 kpc of the Sun, while the radial velocity measurement indicates that the source is a Galactic bulge giant.

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Section: Terrestrial Baseline Parallaxmentioning

confidence: 99%

Section: Terrestrial Baseline Parallaxmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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First Microlens Mass Measurement: PLANET Photometry of EROS BLG‐2000‐5

Albrow

Beaulieu

et al. 2002

ApJ

186

114

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“…Also, these triple lens models are relevant for the consideration of a microlensing parallax signal. While the MOA-2009-BLG-319 Einstein radius crossing time is too short to expect a microlensing parallax signal due to the orbital motion of the Earth, the dense coverage of the light curve peak by widely separated observatories suggests the possibility of a terrestrial microlensing parallax signal (Hardy & Walker 1995;Holz & Wald 1996;Gould et al 2009), as pointed out by Miyake et al (2011). However, the triple lens models will effect the same part of the light curve.…”

Section: New Light Curve Modelmentioning

confidence: 94%

MOA-2009-BLG-319Lb: A Sub-Saturn Planet Inside the Predicted Mass Desert

Terry,

Bhattacharya,

Bennett

et al. 2020

Preprint

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We present an adaptive optics (AO) analysis of images from the Keck-II telescope NIRC2 instrument of the planetary microlensing event MOA-2009-BLG-319. The ∼10 year baseline between the event and the Keck observations allows the planetary host star to be detected at a separation of 66.5 ± 1.7 mas from the source star, consistent with the light curve model prediction. The combination of the host star brightness and light curve parameters yield host star and planet masses of M host = 0.514 ± 0.063M and mp = 66.0 ± 8.1M⊕ at a distance of DL = 7.0 ± 0.7 kpc. The star-planet projected separation is 2.03 ± 0.21 AU. The planet-star mass ratio of this system, q = (3.857 ± 0.029) × 10 −4 , places it in the predicted "planet desert" at 10 −4 < q < 4 × 10 −4 according to the runaway gas accretion scenario of the core accretion theory. Seven of the 30 planets in the Suzuki et al. ( 2016) sample fall in this mass ratio range, and this is the third with a measured host mass. All three of these host stars have masses of 0.5 ≤ M host /M ≤ 0.7, which implies that this predicted mass ratio gap is filled with planets that have host stars within a factor of two of 1M . This suggests that runaway gas accretion does not play a major role in determining giant planet masses for stars somewhat less massive than the Sun. Our analysis has been accomplished with a modified DAOPHOT code that has been designed to measure the brightness and positions of closely blended stars. This will aid in the development of the primary method that the Nancy Grace Roman Space Telescope mission will use to determine the masses of microlens planets and their hosts.

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“…Terrestrial parallax occurs when a microlensing event is observed from two separate observatories on Earth. If the separation between the sites is large enough and the event is observed at high cadence, it is possible to see that the time of the peak and impact parameter differs between sites (Hardy & Walker 1995;Holz & Wald 1996;Gould et al 2009). Space parallax is similar to the terrestrial one, but one of the observatories is located in space (Refsdal 1966).…”

Section: Introductionmentioning

confidence: 99%

Lens parameters for Gaia18cbf -- a long gravitational microlensing event in the Galactic plane

Kruszyńska,

Wyrzykowski,

Rybicki

et al. 2021

Preprint

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Context. The size of the Einstein Radius in a microlensing event scales as a square root of the mass of the lens. Therefore, long-lasting microlensing events are the best candidates for massive lenses, including black holes. Aims. Here we present the analysis of the Gaia18cbf microlensing event reported by the Gaia Science Alerts system. It has exhibited a long timescale and features characteristic to the annual microlensing parallax effect. We deduce the parameters of the lens based on the derived best fitting model. Methods. We used photometric data collected by the Gaia satellite as well as the follow-up data gathered by the ground-based observatories. We investigate the range of microlensing models and use them to derive the most probable mass and distance to the lens using a Galactic model as a prior. Using known mass-brightness relation we determined how likely it is that the lens is a main sequence star. Results. This event is one of the longest ever detected, with the Einstein timescale of t E = 491.41 +128.31 −84.94 days for the best solution and t E = 453.74 +178.69 −105.74 days for the second-best. This translates to a lens mass of M L = 2.91 +6.02 −1.70 M and M L = 1.88 +4.40 −1.19 M respectively. The limits on the blended light suggest that this event was most likely not caused by a main sequence star, but rather by a dark remnant of stellar evolution.

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To the Revd. E. M. Walker (14 November 1922)

Cited by 19 publications

References 0 publications

First Microlens Mass Measurement: PLANET Photometry of EROS BLG‐2000‐5

First Microlens Mass Measurement: PLANET Photometry of EROS BLG‐2000‐5

MOA-2009-BLG-319Lb: A Sub-Saturn Planet Inside the Predicted Mass Desert

Lens parameters for Gaia18cbf -- a long gravitational microlensing event in the Galactic plane

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