On planetary companions to the MACHO 98-BLG-35 microlens star

被引:95
作者
Rhie, SH [1 ]
Bennett, DP
Becker, AC
Peterson, BA
Fragile, PC
Johnson, BR
Quinn, JL
Crouch, A
Gray, J
King, L
Messenger, B
Thomson, S
Bond, IA
Abe, F
Carter, BS
Dodd, RJ
Hearnshaw, JB
Honda, M
Jugaku, J
Kabe, S
Kilmartin, PM
Koribalski, BS
Masuda, K
Matsubara, Y
Muraki, Y
Nakamura, T
Nankivell, GR
Noda, S
Rattenbury, NJ
Reid, M
Rumsey, NJ
Saito, T
Sato, H
Sato, S
Sekiguchi, M
Sullivan, DJ
Sumi, T
Watase, Y
Yanagisawa, T
Yock, PCM
Yoshizawa, M
机构
[1] Univ Notre Dame, Dept Phys, Notre Dame, IN 46556 USA
[2] Univ Calif Berkeley, Ctr Particle Astrophys, Berkeley, CA 94720 USA
[3] Univ Washington, Dept Astron, Seattle, WA 98195 USA
[4] Univ Washington, Dept Phys, Seattle, WA 98195 USA
[5] Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia
[6] Univ Minnesota, Tate Lab Phys, Minneapolis, MN 55455 USA
[7] Monash Univ, Dept Math & Stat, Clayton, Vic 3168, Australia
[8] Univ Auckland, Fac Sci, Auckland 1, New Zealand
[9] Univ Canterbury, Dept Phys & Astron, Christchurch 1, New Zealand
[10] Nagoya Univ, STE Lab, Nagoya, Aichi 464, Japan
[11] Carter Natl Observ, Wellington, New Zealand
[12] Univ Victoria, Sch Chem & Phys Sci, Wellington, New Zealand
[13] Univ Tokyo, Inst Cosm Ray Res, Tanashi, Tokyo 188, Japan
[14] Res Inst Civilizat, Tama 206, Japan
[15] KEK Lab, Tsukuba, Ibaraki 305, Japan
[16] CSIRO, Australia Telescope Natl Facil, Epping, NSW 2121, Australia
[17] Kyoto Univ, Dept Phys, Kyoto 606, Japan
[18] Tokyo Metropolitan Coll Aeronaut, Tokyo 116, Japan
[19] Nagoya Univ, Dept Phys, Nagoya, Aichi 464, Japan
[20] Natl Astron Observ, Mitaka, Tokyo 181, Japan
关键词
gravitational lensing; planetary systems; stars; low-mass; brown dwarfs;
D O I
10.1086/308634
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present observations of the microlensing event MACHO 98-BLG-35, which reached a peak magnification factor of almost 80. These observations by the Microlensing Planet Search (MPS) and MOA collaborations place strong constraints on the possible planetary system of the lens star and show intriguing evidence for a low-mass planet with a mass fraction 4 x 10(-5) less than or equal to epsilon less than or equal to 2 x 10(-4). A giant planet with epsilon = 10(-3) is excluded from 95% of the region between 0.4 and 2.5 R-E from the lens star, where R-E is the Einstein ring radius of the lens. This exclusion region is more extensive than the generic "lensing zone," which is 0.6-1.6 R-E. For smaller mass planets, we can exclude 57% of the "lensing zone" for epsilon=10(-4) and 14% of the lensing zone for epsilon=10(-5). The mass fraction epsilon=10(-5) corresponds to an Earth-mass planet for a lensing star of mass similar to 0.3 M.. A number of similar events will provide statistically significant constraints on the prevalence of Earth-mass planets. In order to put our limits in more familiar terms, we have compared our results to those expected for a solar system clone, averaging over possible lens system distances and orientations. We End that such a system is ruled out at the 90% confidence level. A copy of the solar system with Jupiter replaced by a second Saturn-mass planet can be ruled out at 70% confidence. Our low-mass planetary signal (few Earth masses to Neptune mass) is significant at the 4.5 sigma confidence level. If this planetary interpretation is correct, the MACHO 98-BLG-35 lens system constitutes the first detection of a low-mass planet orbiting an ordinary star without gas giant planets.(20)
引用
收藏
页码:378 / 391
页数:14
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