Browsing by Author "Nandakumar, Sangeetha"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    A Pair of Warm Giant Planets near the 2:1 Mean Motion Resonance around the K-dwarf Star TOI-2202*
    (2021) Trifonov, Trifon; Brahm, Rafael; Espinoza, Nestor; Henning, Thomas; Jordan, Andres; Nesvorny, David; Dawson, Rebekah I.; Lissauer, Jack J.; Lee, Man Hoi; Kossakowski, Diana; Rojas, Felipe I.; Hobson, Melissa J.; Sarkis, Paula; Schlecker, Martin; Bitsch, Bertram; Bakos, Gaspar A.; Barbieri, Mauro; Bhatti, W.; Butler, R. Paul; Crane, Jeffrey D.; Nandakumar, Sangeetha; Diaz, Matias R.; Shectman, Stephen; Teske, Johanna; Torres, Pascal; Suc, Vincent; Vines, Jose I.; Wang, Sharon X.; Ricker, George R.; Shporer, Avi; Vanderburg, Andrew; Dragomir, Diana; Vanderspek, Roland; Burke, Christopher J.; Daylan, Tansu; Shiao, Bernie; Jenkins, Jon M.; Wohler, Bill; Seager, Sara; Winn, Joshua N.
    TOI-2202 b is a transiting warm Jovian-mass planet with an orbital period of P = 11.91 days identified from the Full Frame Images data of five different sectors of the TESS mission. Ten TESS transits of TOI-2202 b combined with three follow-up light curves obtained with the CHAT robotic telescope show strong transit timing variations (TTVs) with an amplitude of about 1.2 hr. Radial velocity follow-up with FEROS, HARPS, and PFS confirms the planetary nature of the transiting candidate (a (b) = 0.096 +/- 0.001 au, m (b) = 0.98 +/- 0.06 M (Jup)), and a dynamical analysis of RVs, transit data, and TTVs points to an outer Saturn-mass companion (a (c) = 0.155 +/- 0.002 au, m (c) = 0.37 +/- 0.10 M (Jup)) near the 2:1 mean motion resonance. Our stellar modeling indicates that TOI-2202 is an early K-type star with a mass of 0.82 M (circle dot), a radius of 0.79 R (circle dot), and solar-like metallicity. The TOI-2202 system is very interesting because of the two warm Jovian-mass planets near the 2:1 mean motion resonance, which is a rare configuration, and their formation and dynamical evolution are still not well understood.
  • No Thumbnail Available
    Item
    Precise Transit and Radial-velocity Characterization of a Resonant Pair: The Warm Jupiter TOI-216c and Eccentric Warm Neptune TOI-216b
    (2021) Dawson, Rebekah I.; Huang, Chelsea X.; Brahm, Rafael; Collins, Karen A.; Hobson, Melissa J.; Jordan, Andres; Dong, Jiayin; Korth, Judith; Trifonov, Trifon; Abe, Lyu; Agabi, Abdelkrim; Bruni, Ivan; Butler, R. Paul; Barbieri, Mauro; Collins, Kevin I.; Conti, Dennis M.; Crane, Jeffrey D.; Crouzet, Nicolas; Dransfield, Georgina; Evans, Phil; Espinoza, Nestor; Gan, Tianjun; Guillot, Tristan; Henning, Thomas; Lissauer, Jack J.; Jensen, Eric L. N.; Sainte, Wenceslas Marie; Mekarnia, Djamel; Myers, Gordon; Nandakumar, Sangeetha; Relles, Howard M.; Sarkis, Paula; Torres, Pascal; Shectman, Stephen; Schmider, Francois-Xavier; Shporer, Avi; Stockdale, Chris; Teske, Johanna; Triaud, Amaury H. M. J.; Wang, Sharon Xuesong; Ziegler, Carl; Ricker, G.; Vanderspek, R.; Latham, David W.; Seager, S.; Winn, J.; Jenkins, Jon M.; Bouma, L. G.; Burt, Jennifer A.; Charbonneau, David; Levine, Alan M.; McDermott, Scott; McLean, Brian; Rose, Mark E.; Vanderburg, Andrew; Wohler, Bill
    TOI-216 hosts a pair of warm, large exoplanets discovered by the TESS mission. These planets were found to be in or near the 2:1 resonance, and both of them exhibit transit timing variations (TTVs). Precise characterization of the planets' masses and radii, orbital properties, and resonant behavior can test theories for the origins of planets orbiting close to their stars. Previous characterization of the system using the first six sectors of TESS data suffered from a degeneracy between planet mass and orbital eccentricity. Radial-velocity measurements using HARPS, FEROS, and the Planet Finder Spectrograph break that degeneracy, and an expanded TTV baseline from TESS and an ongoing ground-based transit observing campaign increase the precision of the mass and eccentricity measurements. We determine that TOI-216c is a warm Jupiter, TOI-216b is an eccentric warm Neptune, and that they librate in 2:1 resonance with a moderate libration amplitude of deg, a small but significant free eccentricity of for TOI-216b, and a small but significant mutual inclination of 12-39 (95% confidence interval). The libration amplitude, free eccentricity, and mutual inclination imply a disturbance of TOI-216b before or after resonance capture, perhaps by an undetected third planet.
  • Thumbnail Image
    Item
    The high optical brightness of the BlueWalker 3 satellite
    (2023) Nandakumar, Sangeetha; Eggl, Siegfried; Tregloan-Reed, Jeremy; Adam, Christian; Anderson-Baldwin, Jasmine; Bannister, Michele T.; Battle, Adam; Benkhaldoun, Zouhair; Campbell, Tanner; Colque, J. P.; Damke, Guillermo; Plauchu Frayn, Ilse; Ghachoui, Mourad; Guillén, Pedro F.; Kaeouach, Aziz Ettahar; Krantz, Harrison R.; Langbroek, Marco; Rattenbury, Nicholas; Reddy, Vishnu; Kim, Sam
    Large constellations of bright artificial satellites in low Earth orbit pose significant challenges to ground-based astronomy1. Current orbiting constellation satellites have brightnesses between apparent magnitudes 4 and 6, whereas in the near-infrared Ks band, they can reach magnitude 2 (ref. 2). Satellite operators, astronomers and other users of the night sky are working on brightness mitigation strategies3,4. Radio emissions induce further potential risk to ground-based radio telescopes that also need to be evaluated. Here we report the outcome of an international optical observation campaign of a prototype constellation satellite, AST SpaceMobile’s BlueWalker 3. BlueWalker 3 features a 64.3 m2 phased-array antenna as well as a launch vehicle adaptor (LVA)5. The peak brightness of the satellite reached an apparent magnitude of 0.4. This made the new satellite one of the brightest objects in the night sky. Additionally, the LVA reached an apparent V-band magnitude of 5.5, four times brighter than the current International Astronomical Union recommendation of magnitude 7 (refs. 3,6); it jettisoned on 10 November 2022 (Universal Time), and its orbital ephemeris was not publicly released until 4 days later. The expected build-out of constellations with hundreds of thousands of new bright objects1 will make active satellite tracking and avoidance strategies a necessity for ground-based telescopes.