Academia Sinica Institute of Astronomy & Astrophysics
中央研究院天文及天文物理研究所
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The amplitude of the density perturbation grows as it propagates downstream (from left to right) across a C-type shock in a typical environment of star-forming clouds. The growth arises from an unstable mode driven by the ion-neutral drag, i.e., the drag instability, which can lead to a chaotic shock structure.
Chaos in a cosmic shock
Formation of multiple-planet systems in resonant chains around M dwarfs, such as the famous Trappist-1 planetary system. The observed architecture of the orbital resonances depends on the formation time of the planet within the ice line of a protoplanetary disk, which can be used to constrain planet formation models such as pebble accretion and streaming instabilities. This is a work accomplished by an ASIAA summer student Lin Yu-Chia and a postdoc fellow Dr. Yuji Matsumoto in my group.
Harmony in a multiple-planetary system
Numerical simulations of the time evolution of orbital radii of protoplanets, i.e., their dynamical histories. The top panel is the case for protoplanets around a 1 solar mass star, and the bottom panel is that for a 0.056 solar mass star. Around low mass stars, protoplanets experienced more violent dynamical evolution, which even caused ejections of protoplanets.
Earth-sized planet formation around late M dwarfs
A thermal bulge of a hot Jupiter is excited by stellar irradiation against a gravitational bulge, thereby maintaining an asynchronous rotation of the planet and preventing the planet from gravitational contraction (the figure was originally made by Ginny Wei). This research result was highlighted on the MOST GASE webpage at http://trh.gase.most.ntnu.edu.tw/en/article/content/132.
A Hot Jupiter Bloated by a Thermal Bulge
Figure shows an example of a nested-grid mesh refinement (NMR) run carried out by the Antares code for a global protoplanetary disk with an embedded circumplanetary disk surrounding a 0.05-Jupiter-mass planet at 5.2 AU from the star at origin. The simulation has 6 levels of refinement, with the finest resolution of 6.25×10–4 AU, resolving the Hill radius of the planet (0.13 AU at 5.2 AU) with ~200 cells. (Antares code with the CompAS project)
Formation and Evolution of Protoplanetary and Circumplanetary Disks with Antares Three-Dimensional Global Hydrodynamic Simulations
Figure: Example of a nested-grid mesh refinement (NMR) run of a global protoplanetary disk with an embedded circumplanetary disk surrounding a 0.05-Jupiter-mass planet at 5.2 AU from the star at origin. The simulation has 6 levels of refinement, with the finest resolution of 6.25×10–4 AU, resolving the Hill radius of the planet (0.13 AU at 5.2 AU) with ~200 cells.
Formation and Evolution of Protoplanetary and Circumplanetary Disks with Antares Three-Dimensional Global Hydrodynamic Simulations
In the bottom panels, square sections of surface density simulated with <b>Antares</b> are shown centered at the locations of protoplanets. The surface density is obtained by vertical integration over <i>z</i> < 0.0156 AU (the height of the finest level) for protoplanets with masses of 4, 8, and 16 Earth Masses, respectively. The central star is located on the left and the protoplanets are orbiting the central star counterclockwise. On top of each surface density is the corresponding volume density cutting through the plane defined by
Formation of Isothermal Circumplanetary Disks with Three-Dimensional Global Simulations for Sub-Neptune-Mass Protoplanets
Weather map of the transiting hot Jupiter HD 189733b, illustrated by air pressure (color) and wind velocity fields (arrows), as viewed by someone who descends through the planetary atmosphere. The patters are generated primarily by equatorial Rossby waves on the highly irradiated planet. These waves lead to the equatorial super-rotating circulation, which reduces the day-night temperature contrast of this tidally locked exoplanet. The circulation model also explains why the maximum thermal flux from the planet occurs several hours before secondary eclipse, an observational result revealed by the Spitzer Space Telescope (Tsai, Dobbs-Dixon, Gu, ApJ, 2014, 794, 141).
Weather on a Hot Jupiter
Numerical model for the asymmetric distribution of gas (left panel) and dust (right panel) column density maps of a face-on protoplanetary disk. A massive giant planet (0.5% of the mass of the central star) revolves about the central star on a circular orbit. The dust density map is only shown for the outer part of the disk where the disk is eccentric and the black contour indicates the location of the disk pericenter (Hsieh & Gu 2012, Astrophysical Journal, 760, 119).
Numerical model for the asymmetric distribution of gas and dust column density maps of a face-on protoplanetary disk.
Schematic of the theoretical model showing the dipole fields of a proto-star that are misaligned with both the stellar spin axis and the orbital plane of a hot Jupiter. Consequently, the young hot Jupiter experiences time-varying stellar fields and thus induces electric currents, leading to a dissipation torque that can alter the stellar obliquity λ.
Hot Jupiters on Prograde/Retrograde Orbits
Gas (left panel) and dust (right panel) density maps of a face-on protoplanetary disk harboring a gas giant planet of 5 Jupiter masses.
Asymmetric distribution of dust in an eccentric protoplanetary disk
The upper plot illustrates our model, which shows a hot Jupiter orbiting a CTTS in a magnetospheric cavity of a protoplanetary disk. The initial orbit of the planet is set to lie at the 2:1 orbital resonance with the inner edge of the disk. The lower plot shows the orbital evolution through tidal and magnetic interactions between a hot Jupiter and its host star in a magnetospheric cavity. Four cases are presented in terms of different initial masses: 0.7, 1, 1.5, and 2 Jupiter masses (Mj). Each panel has three different tracks by modulating the initial eccentricity. The blue line is the orbital evolution of a planet in a circular orbit; the green line illustrates the case in which the planet of a given initial mass can migrate inward over the longest distance; the red line shows that the planet with a critical eccentricity destructs at the breaking point.
Tidal and Magnetic Interactions Between a Hot Jupiter and its Host Star in the Magnetospheric Cavity of a Protoplanetary Disk
Gu, Pin-Gao
Associate Research Fellow
photo of Gu, Pin-Gao
Office: ASMAB 1212
TEL: +886-2-2366-5397
FAX: +886-2-2367-7849
Email: gu_replace2@_asiaa.sinica.edu.tw

Education and Positions

  • Associate Research Fellow, ASIAA (2013~present)
  • Assistant Research Fellow, ASIAA (2005~2013)
  • Adjunct Assistant Professor, National Taiwan Normal University (2005~2009)
  • Postdoctoral Fellow, ASIAA (2000~2005)
  • Ph.D., Physics, University of Texas at Austin (2000)

Research Interests

My current research interests focus primarily on theoretical aspects of planetary sciences, especially in the context of exoplanetary astronomy. With my collaborators, I have been modeling planet formation and evolution around FGKM dwarfs to interpret the KEPLER results and make predictions. I am also investigating the theory of thermal tides to examine whether the model can explain the anomalously large size of hot Jupiters and how it is related to the weather in these toasted worlds. I have been working closely with radio astronomers to kinematically identify various substructures in protoplanetary disks with the ALMA data, such as gas rings, spiral inflow, pressure bumps, and disk eccentricity. Some of these features may be intimately related to planet formation. Furthermore, I am engaging in a calculation about the origin of nanodust in the present Solar System. Besides planetary sciences, I am also studying shock dynamics in the environments of star-forming clouds. My collaborators and I uncovered a fluid instability (i.e., drag instability) in turbulent molecular clouds.

I enjoy interacting with students (both undergraduate and graduate). If you are interested in my research, please feel free to contact me for research opportunities.

Publications

My Publications from ADS

Journal Papers affiliated with ASIAA

  1. Allart R; Lemée-Joliecoeur PB; Jaziri AY; Lafrenière D; Artigau E; Cook N; Darveau-Bernier A; Dang L; Cadieux C; Boucher A; Bourrier V; Deibert EK; Pelletier S; Radica M; Benneke B; Carmona A; Cloutier R; Cowan NB; Delfosse X; Donati JF; Doyon R; Figueira P; Forveille T; Fouqué P; Gaidos E; Gu PG; Hébrard G; Kiefer F; Kóspál Ñ; Jayawardhana R; Martioli E; Dos Santos LA; Shang H; Turner JD; Vidotto AA, "Homogeneous search for helium in the atmosphere of 11 gas giant exoplanets with SPIRou" , A&A: 677, id.A164 (26 pp), Sep, 2023 [SCI] ( ADS | Fulltext )
  2. Gu P-G; Chen H, "Deuterium Escape on Photoevaporating Sub-Neptunes" , ApJL: 953(2), id.L24, Aug, 2023 [SCI] ( ADS | Fulltext )
  3. Takami M; Gu P-G; Otten G; Delacroix C; Liu S-Y; Wang S-Y; Karr JL, "Semi-analytic calculations for extended mid-infrared emission associated with FU Ori-type objects" , A&A: 679, id.A21 (23pp), Nov, 2023 [SCI] ( ADS | Fulltext )
  4. Gu P-G; Chen C-Y; Shen E; Yen C-C, Lin MK, "Revealing the Drag Instability in One-fluid Nonideal Magnetohydrodynamic Simulations of a 1D Isothermal C-shock" , ApJ: 935(2), id.95 (16pp), Aug, 2022 [SCI] ( ADS | Fulltext )
  5. Kuo IHG; Yen H-W; Gu P-G; Chang T-E, "Kinematical Constraint on Eccentricity in the Protoplanetary Disk MWC 758 with ALMA" , ApJ: 938(1), id.50 (13pp), Oct, 2022 [SCI] ( ADS | Fulltext )
  6. Martioli E; Hébrard G; Fouqué P; Artigau Ù; Donati JF; Cadieux C; Bellotti S; Lecavelier Des Etangs A; Doyon R; Do Nascimento JD; Arnold L; Carmona A; Cook NJ; Cortes-Zuleta P; De Almeida L; Delfosse X; Folsom CP; König PC; Moutou C; Ould-Elhkim M; Petit P; Stassun KG; Vidotto AA; Vandal T; Benneke B; Boisse I; Bonfils X; Boyd P; Brasseur C; Charbonneau D; Cloutier R; Collins K; Cristofari P; Crossfield I; Díaz RF; Fausnaugh M; Figueira P; Forveille T; Furlan E; Girardin E; Gnilka CL; Gomes Da Silva J; Gu PG; Guerra P; Howell SB; Hussain GaJ; Jenkins JM; Kiefer F; Latham DW; Matson RA; Matthews EC; Morin J; Naves R; Ricker G; Seager S; Takami M; Twicken JD; Vanderburg A; Vanderspek R; Winn J, "TOI-1759 b: A transiting sub-Neptune around a low mass star characterized with SPIRou and TESS" , A&A: 660, id.A86 (39 pp), Apr, 2022 [SCI] ( ADS | Fulltext )
  7. Gu PG, "The Drag Instability in a 2D Isothermal C-shock" , ApJ: 914(2), id.87 (20pp), Jun, 2021 [SCI] ( ADS | Fulltext )
  8. Hoang T; Lazarian A; Lee H; Cho K; Gu P-G ; Ng C-H, "Effect of Dust Rotational Disruption by Radiative Torques and Implications for the F-corona Decrease Revealed by the Parker Solar Probe" , ApJ: 919(2), id.91 (14pp), Sep, 2021 [SCI] ( ADS | Fulltext )
  9. Lin Y-C; Matsumoto Y; Gu P-G, "Formation of multiple-planet systems in resonant chains around M dwarfs" , ApJ: 907(2), id.81 (11pp), Feb, 2021 [SCI] ( ADS | Fulltext )
  10. Matsumoto Y; Kokubo E; Gu P-G; Kurosaki K, "Size evolution of close-in super-Earths through giant impacts and photoevaporation" , ApJ: 923(1), id.81 (17pp), Dec, 2021 [SCI] ( ADS | Fulltext )
  11. Gu P-G; Chen C-Y, "The Drag Instability in a 1D Isothermal C-shock" , ApJ: 898(1), id.67 (18pp.), Jul, 2020 [SCI] ( ADS | Fulltext )
  12. Matsumoto Y; Gu P-G; Kokubo E; et al., "Ejection of close-in super-Earths around low-mass stars in the giant impact stage" , A&A: 642, id.A23 (10pp.), Oct, 2020 [SCI] ( ADS | Fulltext )
  13. Yen H-W; Gu P-G, "Kinematical signs of dust trapping and feedback in a local pressure bump in the protoplanetary disk around HD 142527 revealed with ALMA" , ApJ: 905(2), id.89 (16 pp.), Dec, 2020 [SCI] ( ADS | Fulltext )
  14. Gu P-G; Peng D-K; Yen C-C, "Modeling the Thermal Bulge of a Hot Jupiter with the Two-stream Approximation" , ApJ: 887(2), id. 228 (15 pp.), Dec, 2019 [SCI] ( ADS | Fulltext )
  15. Yen H-W; Gu P-G; Hirano N; Koch PM; Lee C-F; Liu HB; Takakuwa S, "HL Tau Disk in HCO+ (3-2) and (1-0) with ALMA: Gas Density, Temperature, Gap, and One-arm Spiral" , ApJ: 880(2), id. 69 (18 pp.), Aug, 2019 [SCI] ( ADS | Fulltext )
  16. Yen H-W; Takakuwa S; Gu P-G; Hirano N; Lee CF; Liu HB; Liu SY; Wu CJ, "Signs of outflow feedback from a nearby young stellar object on the protostellar envelope around HL Tauri" , A&A: 623, id. A96 (20 pp.), Mar, 2019 [SCI] ( ADS | Fulltext )
  17. Tang Y-W*; Guilloteau S; Dutrey A; ...; Gu PG; ...; Ho PTP; ...; Ohashi N; et al., "Planet Formation in AB Aurigae: Imaging of the inner gaseous Spirals observed inside the Dust Cavity" , ApJ: 840(1), 32, May, 2017 [SCI] ( ADS | Fulltext )
  18. Yen H-W; Liu HB; Gu P-G; Hirano N; Lee C-F ; Puspitaningrum E; Takakuwa S, "Gas Gaps in the Protoplanetary Disk around the Young Protostar HL Tau" , ApJL: 820(2), L25, April 1, 2016 [SCI] ( ADS | Fulltext )
  19. Lee W-K; Gu P-G, "The Effect of Vertical Temperature Gradient on the Propagation of Three-dimensional Waves in a Protoplanetary Disk" , ApJ: 814(1), 72, Nov 20, 2015 [SCI] ( ADS | Fulltext )
  20. Takami M; Hasegawa Y; Muto T; ...; Gu P-G; Dong R; Karr JL; ...; Chapillon E; Tang Y-W; et al., "Surface Geometry of Protoplanetary Disks Inferred From Near-Infrared Imaging Polarimetry" , ApJ: 795(1), 71, Nov, 2014 [SCI] ( ADS | Fulltext )
  21. Tsai S-M; Dobbs-Dixon I; Gu P-G, "Three-dimensional Structures of Equatorial Waves and the Resulting Super-rotation in the Atmosphere of a Tidally Locked Hot Jupiter" , ApJ: 793(2), 141, Oct, 2014 [SCI] ( ADS | Fulltext )
  22. Wang H-H; Bu D; Shang H; Gu P-G, "Formation of Isothermal Disks around Protoplanets. I. Introductory Three-Dimensional Global Simulations for Sub-Neptune-Mass Protoplanets" , ApJ: 790(1), 32, July, 2014 [SCI] ( ADS | Fulltext )
  23. Chang Y-L; Bodenheimer PH; Gu P-G, "Coupled Evolutions of the Stellar Obliquity, Orbital Distance, and Planet's Radius due to the Ohmic Dissipation Induced in a Diamagnetic Hot Jupiter around a Magnetic T Tauri Star" , ApJ: 757(2), 118, Oct 1, 2012 [SCI] ( ADS | Fulltext )
  24. Hsieh H-F; Gu P-G, "On the Secular Behavior of Dust Particles in an Eccentric Protoplanetary Disk with an Embedded Massive Gas Giant Planet" , ApJ: 760(2), 119, Dec 1, 2012 [SCI] ( ADS | Fulltext )
  25. Chang SH; Gu PG; Bodenheimer PH, "Tidal and Magnetic Interactions Between a Hot Jupiter and its Host Star in the Magnetospheric Cavity of a Protoplanetary Disk" , ApJ: 708(2), 1692-1702, Jan 10, 2010 [SCI] ( ADS | Fulltext )
  26. Gu PG, "[News & Views] Extrasolar planets: Larger than they ought to be" , Nature: 465(7296), 300-301, May 20, 2010 [SCI] ( ADS | Fulltext )
  27. Gu PG; Ogilvie GI, "Diurnal thermal tides in a non-synchronized hot Jupiter" , MNRAS: 395(1), 422-435, May 1, 2009 [SCI] ( ADS | Fulltext )
  28. Gu PG; Suzuki TK, "Thermal Response of a Solar-like Atmosphere to an Electron Beam from a Hot Jupiter: A Numerical Experiment" , ApJ: 705(2), 1189-1195, Nov 10, 2009 [SCI] ( ADS | Fulltext )
  29. Gu PG; Shkolnik E; Li SL; et al., "Interactions between hot Jupiters and their host stars" , AN: 326(10), 909-912, Dec, 2005 [SCI] ( ADS | Fulltext )
  30. Shkolnik E; Walker GAH; ...; Gu PG; et al, "Hot Jupiters and hot spots: The short- and long-term chromospheric activity on stars with giant planets" , ApJ: 622(2), 1075-1090, Apr 1, 2005 [SCI] ( ADS | Fulltext )
  31. Gu PG; Bodenheimer PH; Lin DNC, "The Internal Structural Adjustment Due to Tidal Heating of Short-Period Inflated Giant Planets" , ApJ: 608(2), 1076-1094, Jun 20, 2004 [SCI] ( ADS | Fulltext )
  32. Gu PG; Lin DNC; Vishniac ET, "Drag Instability" , Ap&SS: 292(1), 261-265, Mar, 2004 [SCI] ( ADS | Fulltext )
  33. Gu PG; Lin DNC; Bodenheimer PH, "The effect of tidal inflation instability on the mass and dynamical evolution of extrasolar planets with ultrashort periods" , ApJ: 588(1), 509-534, May 1, 2003 [SCI] ( ADS | Fulltext )
  34. Gu PG, "Vorticity budget of weak thermal convection in Keplerian disks" , ApJ: 540(1), 404-411, Sep 1, 2000 [SCI] ( ADS | Fulltext )
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