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5 results on '"J. I. Vines"'

1. Statistical Signatures of Nanoflare Activity. III. Evidence of Enhanced Nanoflaring Rates in Fully Convective stars as Observed by the NGTS

Author

S. D. T. Grant, D. B. Jess, C. J. Dillon, M. Mathioudakis, C. A. Watson, J. A. G. Jackman, D. G. Jackson, P. J. Wheatley, M. R. Goad, S. L. Casewell, D. R. Anderson, M. R. Burleigh, R. G. West, and J. I. Vines

Subjects
Computational methods, Optical flares, Stellar flares, Flare stars, Astrophysics, QB460-466
Abstract

Previous examinations of fully convective M-dwarf stars have highlighted enhanced rates of nanoflare activity on these distant stellar sources. However, the specific role the convective boundary, which is believed to be present for spectral types earlier than M2.5V, plays on the observed nanoflare rates is not yet known. Here, we utilize a combination of statistical and Fourier techniques to examine M-dwarf stellar lightcurves that lie on either side of the convective boundary. We find that fully convective M2.5V (and later subtypes) stars have greatly enhanced nanoflare rates compared with their pre-dynamo mode-transition counterparts. Specifically, we derive a flaring power-law index in the region of 3.00 ± 0.20, alongside a decay timescale of 200 ± 100 s for M2.5V and M3V stars, matching those seen in prior observations of similar stellar subtypes. Interestingly, M4V stars exhibit longer decay timescales of 450 ± 50 s, along with an increased power-law index of 3.10 ± 0.18, suggesting an interplay between the rate of nanoflare occurrence and the intrinsic plasma parameters, e.g., the underlying Lundquist number. In contrast, partially convective (i.e., earlier subtypes from M0V to M2V) M-dwarf stars exhibit very weak nanoflare activity, which is not easily identifiable using statistical or Fourier techniques. This suggests that fully convective stellar atmospheres favor small-scale magnetic reconnection, leading to implications for the flare-energy budgets of these stars. Understanding why small-scale reconnection is enhanced in fully convective atmospheres may help solve questions relating to the dynamo behavior of these stellar sources.

Published
2023
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2. Mass determinations of the three mini-Neptunes transiting TOI-125

Author

L D Nielsen, D Gandolfi, D J Armstrong, J S Jenkins, M Fridlund, N C Santos, F Dai, V Adibekyan, R Luque, J H Steffen, M Esposito, F Meru, S Sabotta, E Bolmont, D Kossakowski, J F Otegi, F Murgas, M Stalport, F Rodler, M R Díaz, N T Kurtovic, G Ricker, R Vanderspek, D W Latham, S Seager, J N Winn, J M Jenkins, R Allart, J M. Almenara, D Barrado, S C C Barros, D Bayliss, Z M Berdiñas, I Boisse, F Bouchy, P Boyd, D J A Brown, E M Bryant, C Burke, W D Cochran, B F Cooke, O D S Demangeon, R F Díaz, J Dittman, C Dorn, X Dumusque, R A García, L González-Cuesta, S Grziwa, I Georgieva, N Guerrero, A P Hatzes, R Helled, C E Henze, S Hojjatpanah, J Korth, K W F Lam, J Lillo-Box, T A Lopez, J Livingston, S Mathur, O Mousis, N Narita, H P Osborn, E Palle, P A Peña Rojas, C M Persson, S N Quinn, H Rauer, S Redfield, A Santerne, L A dos Santos, J V Seidel, S G Sousa, E B Ting, M Turbet, S Udry, A Vanderburg, V Van Eylen, J I Vines, P J Wheatley, and P A Wilson

Published
2020
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3. Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602

Author

L G Bouma, J D Hartman, R Brahm, P Evans, K A Collins, G Zhou, P Sarkis, S N Quinn, J de Leon, J Livingston, C Bergmann, K G Stassun, W Bhatti, J N Winn, G Á Bakos, L Abe, N Crouzet, G Dransfield, T Guillot, W Marie-Sainte, D Mékarnia, A H M J Triaud, C G Tinney, T Henning, N Espinoza, A Jordan, M Barbieri, S Nandakumar, T Trifonov, J I Vines, M Vuckovic, C Ziegler, N Law, A W Mann, G R Ricker, R Vanderspek, S Seager, J M Jenkins, C J Burke, D Dragomir, A M Levine, E V Quintana, J E. Rodriguez, J C Smith, and B Wohler

Subjects
Astronomy
Abstract

We report the discovery of TOI 837b and its validation as a transiting planet. We characterize the system using data from the NASA Transiting Exoplanet Survey Satellite mission, the ESA Gaia mission, ground-based photometry from El Sauce and ASTEP400, and spectroscopy from CHIRON, FEROS, and Veloce. We find that TOI 837 is a T = 9.9 mag G0/F9 dwarf in the southern open cluster IC 2602. The star and planet are therefore 35(sup +11)(sub -5) million years old. Combining the transit photometry with a prior on the stellar parameters derived from the cluster color–magnitude diagram, we find that the planet has an orbital period of 8.3 days and is slightly smaller than Jupiter (R(sub p) = 0.77(sup + 0.09)(sub -0.07) R(sub Jup)). From radial velocity monitoring, we limit M(sub p) sin i to less than 1.20 M(sub Jup) (3σ). The transits either graze or nearly graze the stellar limb. Grazing transits are a cause for concern, as they are often indicative of astrophysical false-positive scenarios. Our follow-up data show that such scenarios are unlikely. Our combined multicolor photometry, high-resolution imaging, and radial velocities rule out hierarchical eclipsing binary scenarios. Background eclipsing binary scenarios, though limited by speckle imaging, remain a 0.2% possibility. TOI 837b is therefore a validated adolescent exoplanet. The planetary nature of the system can be confirmed or refuted through observations of the stellar obliquity and the planetary mass. Such observations may also improve our understanding of how the physical and orbital properties of exoplanets change in time.

Published
2020
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4. Transit timings variations in the three-planet system : TOI-270

Author

Laurel Kaye, Shreyas Vissapragada, Maximilian N Günther, Suzanne Aigrain, Thomas Mikal-Evans, Eric L N Jensen, Hannu Parviainen, Francisco J Pozuelos, Lyu Abe, Jack S Acton, Abdelkrim Agabi, Douglas R Alves, David R Anderson, David J Armstrong, Khalid Barkaoui, Oscar Barragán, Björn Benneke, Patricia T Boyd, Rafael Brahm, Ivan Bruni, Edward M Bryant, Matthew R Burleigh, Sarah L Casewell, David Ciardi, Ryan Cloutier, Karen A Collins, Kevin I Collins, Dennis M Conti, Ian J M Crossfield, Nicolas Crouzet, Tansu Daylan, Diana Dragomir, Georgina Dransfield, Daniel Fabrycky, Michael Fausnaugh, Gábor Fuűrész, Tianjun Gan, Samuel Gill, Michaël Gillon, Michael R Goad, Varoujan Gorjian, Michael Greklek-McKeon, Natalia Guerrero, Tristan Guillot, Emmanuël Jehin, J S Jenkins, Monika Lendl, Jacob Kamler, Stephen R Kane, John F Kielkopf, Michelle Kunimoto, Wenceslas Marie-Sainte, James McCormac, Djamel Mékarnia, Farisa Y Morales, Maximiliano Moyano, Enric Palle, Vivien Parmentier, Howard M Relles, François-Xavier Schmider, Richard P Schwarz, S Seager, Alexis M S Smith, Thiam-Guan Tan, Jake Taylor, Amaury H M J Triaud, Joseph D Twicken, Stephane Udry, J I Vines, Gavin Wang, Peter J Wheatley, and Joshua N Winn

Subjects
Space and Planetary Science, planets and satellites: composition, planets and satellites: formation, Astronomy and Astrophysics, planets and satellites: fundamental parameters, QB
Abstract

We present ground- and space-based photometric observations of TOI-270 (L231-32), a system of three transiting planets consisting of one super-Earth and two sub-Neptunes discovered by TESS around a bright (K-mag = 8.25) M3V dwarf. The planets orbit near low-order mean-motion resonances (5:3 and 2:1) and are thus expected to exhibit large transit timing variations (TTVs). Following an extensive observing campaign using eight different observatories between 2018 and 2020, we now report a clear detection of TTVs for planets c and d, with amplitudes of ∼10 min and a super-period of ∼3 yr, as well as significantly refined estimates of the radii and mean orbital periods of all three planets. Dynamical modelling of the TTVs alone puts strong constraints on the mass ratio of planets c and d and on their eccentricities. When incorporating recently published constraints from radial velocity observations, we obtain masses of $M_{\mathrm{b}}=1.48\pm 0.18\, M_\oplus$, $M_{\mathrm{c}}=6.20\pm 0.31\, M_\oplus$, and $M_{\mathrm{d}}=4.20\pm 0.16\, M_\oplus$ for planets b, c, and d, respectively. We also detect small but significant eccentricities for all three planets : eb = 0.0167 ± 0.0084, ec = 0.0044 ± 0.0006, and ed = 0.0066 ± 0.0020. Our findings imply an Earth-like rocky composition for the inner planet, and Earth-like cores with an additional He/H2O atmosphere for the outer two. TOI-270 is now one of the best constrained systems of small transiting planets, and it remains an excellent target for atmospheric characterization.

Published
2021

5. Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602

Author

L. G., Bouma, J. D., Hartman, R. Brahm P., Evans, K. A., Collins, G., Zhou, P., Sarkis, S. N., Quinn, J. De, Leon, J., Livingston, C., Bergmann, K. G., Stassun, W., Bhatti, J. N., Winn, G. Á., Bakos, L., Abe, N., Crouzet, G., Dransfield, T., Guillot, W., Marie-Sainte, D., Mékarnia, A. H. M. J., Triaud, C. G., Tinney, T., Henning, N., Espinoza, A., Jordán, M., Barbieri, S., Nandakumar, T., Trifonov, J. I., Vines, M., Vuckovic, Ziegler, Camille, N., Law, A. W., Mann, G. R., Ricker, R., Vanderspek, S., Seager, J. M., Jenkins, C. J., Burke, D., Dragomir, A. M., Levine, E. V., Quintana, J. E., Rodriguez, J. C., Smith, B., Wohler, Department of Astrophysical Sciences [Princeton], Princeton University, and Mekarnia, Djamel

Subjects
[SDU] Sciences of the Universe [physics], [SDU]Sciences of the Universe [physics], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2020

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