Year: 2023
Type: article
Abstract: We present the first measurement of the mass function of free-floating planets (FFPs), or very wide orbit planets down to an Earth mass, from the MOA-II microlensing survey in 2006–2014. Six events are likely to be due to planets with Einstein radius crossing times t E < 0.5 days, and the shortest has t E = 0.057 ± 0.016 days and an angular Einstein radius of θ E = 0.90 ± 0.14 μ as. We measure the detection efficiency depending on both t E and θ E with image-level simulations for the first time. These short events are well modeled by a power-law mass function, dN 4 / d log M = ( 2.18 − 1.40 + 0.52 ) × ( M / 8 M ⊕ ) − α 4 dex −1 star −1 with α 4 = 0.96 − 0.27 + 0.47 for M / M ⊙ < 0.02. This implies a total of f = 21 − 13 + 23 FFPs or very wide orbit planets of mass 0.33 < M / M ⊕ < 6660 per star, with a total mass of 80 − 47 + 73 M ⊕ star −1 . The number of FFPs is 19 − 13 + 23
Source: The Astronomical Journal
Authors: Takahiro Sumi, Naoki Koshimoto, David P. Bennett, Nicholas J. Rattenbury, Fumio Abe, Richard Barry, Aparna Bhattacharya, Ian A. Bond, Hirosane Fujii, Akihiko Fukui, Ryusei Hamada, Yuki Hirao, Stela Ishitani Silva, Yoshitaka Itow, Rintaro Kirikawa, Iona Kondo, Yutaka Matsubara, Shota Miyazaki, Yasushi Muraki, Greg Olmschenk, Clément Ranc, Yuki Satoh, Daisuke Suzuki, Mio Tomoyoshi, Paul . J. Tristram, Aikaterini Vandorou, Hibiki Yama, Kansuke Yamashita
Institutions: The University of Osaka, Goddard Space Flight Center, University of Maryland, College Park, University of Auckland, Institute for Space-Earth Environmental Research, Nagoya University, Nagoya University, Massey University, Instituto de Astrofísica de Canarias, The University of Tokyo, Institute of Astronomy, Graduate School of Science, The University of Tokyo, Catholic University of America, Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, Centre National de la Recherche Scientifique, Institut d'Astrophysique de Paris, Sorbonne Université, University of Canterbury
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Awards: 重力マイクロレンズを用いた地球質量の系外惑星、浮遊惑星及びブラックホールの探査, Revealing the Planet Mass Function beyond the Snow Line, Search for free-floating planets by using gravitational microlensing, OUR PROPOSAL INVOLVES FOLLOW-UP OBSERVATIONS OF MORE THAN 60 PLANETARY AND STELLAR BINARY MICRO LENSING EVENTS IN AN ATTEMPT TO IDENTIFY AND MEASURE THE BRIGHTNESS OF THE LENS STARS FOR THESE MICROLENSING EVENTS. THE KECK DATA WILL INCLUDE LASER GUIDE STAR ADAPTIVE OPTICS (AO) IMAGES FROM THE NIRC2 AND OSIRIS INFRARED CAMERAS. THIS PROJECT WILL BE MANAGED BY THE P.L. DAVID BENNETT WHO WILL LEAD THE LIGHT CURVE MODELING EFFORT TO DETERMINE WHICH EVENTS TO OBSERVE AS A FUNCTION OF OBSERVING CONDITIONS. HE WILL BE RESPONSIBLE FOR SELECTING THE TARGETS TO BE OBSERVED AND TO DETERMINE THE OBSERVING PLANS. THE DATA REDUCTION FOR THIS DATA WILL BE THE RESPONSIBILITY OF POSTDOC DR. APAMA BHATTACHARYA WITH THE HELP OF CO-I'S J.-P. BEAULIEU AND JESSICA LU (WHO ARE NOT FUNDED BY THIS PROPOSAL). BOTH BEAULIEU AND LU HAVE EXTENSIVE EXPERIENCE ANALYZING KECK DATA AND THEIR METHODS AND SOFTWARE WILL BE USED FOR BOTH THE OBSERVATIONS AND THE ANALYSIS. WE EXPECT THAT THIS ANALYSIS WILL LEAD TO A LARGE NUMBER OF PAPERS AND WE EXPECT THAT THE INFORMATION PROVIDED IN THESE PAPERS ON THE MAGNITUDES AND RELATIVE PROPER MOTIONS OF THE SOURCE AND LENS STARS WILL BE THE PRIMARY INPUTS FOR FUTURE WORK ON THESE EVENTS. IN ADDITION TO THESE PUBLICATIONS AND ASSOCIATED HIGH LEVEL DATA PRODUCTS WE WILL ALSO PROVIDE CALIBRATED CO-ADDED IMAGES OF EACH TARGET THAT IS OBSERVED WITH A GOOD AO CORRECTION TO THE NASA EXOPLANET ARCHIVE. IN MOST CASES TARGETS WILL BE OBSERVED IN MULTIPLE PASSBANDS AND WE WILL USUALLY OBTAIN DEEP HIGH RESOLUTION IMAGES (WITH THE NIRC-2 NARROW CAMERA) AND SHALLOWER WIDER ANGLE IMAGES (WITH THE NIRC-2 WIDE CAMERA) TO AID IN CALIBRATION TO 2MASS OR VVV STANDARD STARS. WE WILL PROVIDE A SINGLE CO-ADDED IMAGE IN EACH PASSBAND WITH EACH CAMERA THAT WAS USED TO THE NASA EXOPLANET ARCHIVE. THE PUBLICATIONS DESCRIBING THE ANALYSIS OF EACH EVENT WILL PROVIDE DETAILS ON THE LOCATION OF THE SOURCE STAR BASED ON DIFFERENCE IMAGES TAKEN CLOSE TO MAXIMUM MICROLENSING MAGNIFICATION AND IFWE OBTAIN PERMISSION FROM THE MICROLENSING OBSERVING GROUPS THAT OWN THESE DATA WE WILL ALSO ADD THESE TO THE NASA EXOPLANET ARCHIVE. WE PLAN TO SUBMIT THIS DATA TO THE NASA EXOPLANET ARCHIVE ON A ROLLING BASIS AS EACH EVENT IS ANALYZED AND IMAGES FOR ALL THE EVENTS WITH GOOD DATA WILL BE SUBMITTED BY FEBRUARY 28 2021., 近赤外線重力マイクロレンズ観測による冷たい系外惑星・浮遊惑星の形成過程の解明, G5434575043
OpenAlex ID: W4385874293