Populating the brown dwarf and stellar boundary: Five stars with transiting companions near the hydrogen-burning mass limit
Nolan Grieves, François Bouchy, Monika Lendl, Theron Carmichael, Ismael Mireles, Avi Shporer, Kim K. McLeod, Karen A. Collins, Rafael Brahm, Keivan G. Stassun, … 展开作者
Nolan Grieves, François Bouchy, Monika Lendl, Theron Carmichael, Ismael Mireles, Avi Shporer, Kim K. McLeod, Karen A. Collins, Rafael Brahm, Keivan G. Stassun, Sam Gill, Luke G. Bouma, Tristan Guillot, Marion Cointepas, Leonardo A. Dos Santos, Sarah L. Casewell, Jon M. Jenkins, Thomas Henning, Louise D. Nielsen, Angelica Psaridi, Stéphane Udry, Damien Ségransan, Jason D. Eastman, George Zhou, Lyu Abe, Abelkrim Agabi, David Charbonneau, Kevin I. Collins, Knicole D. Colon, Nicolas Crouzet, Georgina Dransfield, Phil Evans, Robert F. Goeke, Rhodes Hart, Jonathan M. Irwin, Eric L. N. Jensen, Andrés Jordán, John F. Kielkopf, David W. Latham, Wenceslas Marie-Sainte, Djamel Mékarnia, Peter Nelson, Samuel N. Quinn, Don J. Radford, David R. Rodriguez, Pamela Rowden, François-Xavier Schmider, Richard P. Schwarz, Jeffrey C. Smith, Chris Stockdale, Olga Suarez, Thiam-Guan Tan, Amaury H. M. J. Triaud, William Waalkes, Geof Wingham
备注：
25 pages, 14 figures, Accepted by Astronomy & Astrophysics
We report the discovery of five transiting companions near the hydrogen-burning mass limit in close orbits around main sequence stars originally identified by the Transiting Exoplanet Survey Satellite (TESS) as TESS Objects of Interest (TOIs): TOI-148, TOI-587, TOI-681, TOI-746, and TOI-1213. Using TESS and ground-based photometry as well as radial velocities from the CORALIE, CHIRON, TRES, and FEROS spectrographs, we found the companions have orbital periods between 4.8 and 27.2 days, masses between 77 and 98 $\mathrm{M_{Jup}}$, and radii between 0.81 and 1.66 $\mathrm{R_{Jup}}$. These targets have masses near the uncertain lower limit of hydrogen core fusion ($\sim$73-96 $\mathrm{M_{Jup}}$), which separates brown dwarfs and low-mass stars. We constrained young ages for TOI-587 (0.2 $\pm$ 0.1 Gyr) and TOI-681 (0.17 $\pm$ 0.03 Gyr) and found them to have relatively larger radii compared to other transiting companions of a similar mass. Conversely we estimated older ages for TOI-148 and TOI-746 and found them to have relatively smaller companion radii. With an effective temperature of 9800 $\pm$ 200 K, TOI-587 is the hottest known main-sequence star to host a transiting brown dwarf or very low-mass star. We found evidence of spin-orbit synchronization for TOI-148 and TOI-746 as well as tidal circularization for TOI-148. These companions add to the population of brown dwarfs and very low-mass stars with well measured parameters ideal to test formation models of these rare objects, the origin of the brown dwarf desert, and the distinction between brown dwarfs and hydrogen-burning main sequence stars.
The Impact of Irradiation on the Radius and Thermal Evolution of Transiting Brown Dwarfs
School of Earth and Space Exploration, Arizona State University（亚利桑那州立大学地球与空间探索学院）；Department of Astronomy and Astrophysics, University of California, Santa Cruz（加州大学圣克鲁兹分校天文学与天体物理系）；Institute for Astronomy, University of Hawai‘i（夏威夷大学天文研究所）；William H. Miller III Department of Physics & Astronomy, Johns Hopkins University（约翰斯·霍普金斯大学威廉·H·米勒三世物理与天文学系）
We are using precise radial velocities from CORALIE together with precision photometry from the Next Generation Transit Survey (NGTS) to follow up stars with single-transit events detected with the Transiting Exoplanet Survey Satellite (TESS). As part of this survey we identified a single transit on the star TIC-320687387, a bright (T=11.6) G-dwarf observed by TESS in Sector 13 and 27. From subsequent monitoring of TIC-320687387 with CORALIE, NGTS, and Lesedi we determined that the companion, TIC-320687387 B,is a very low-mass star with a mass of $96.2 \pm _{2.0}^{1.9} M_J$ and radius of $1.14…
M-dwarf stars -- hydrogen-burning stars that are smaller than 60 per cent of the size of the Sun -- are the most common class of star in our Galaxy and outnumber Sun-like stars by a ratio of 12:1. Recent results have shown that M dwarfs host Earth-sized planets in great numbers: the average number of M-dwarf planets that are between 0.5 to 1.5 times the size of Earth is at least 1.4 per star. The nearest such planets known to transit their star are 39 parsecs away, too distant for detailed follow-up observations to measure the planetary masses or to study their atmospheres. Here we report obse…
In the present paper we show that within all the uncertainties that govern the process of Roche lobe overflow in Case Br type massive binaries, it can not be excluded that a significant fraction of them merge and become single stars. We demonstrate that at least some of them will spend most of their core helium burning phase as hydrogen rich blue stars, populating the massive blue supergiant region and/or the massive Be type star population. The evolutionary simulations let us suspect that these mergers will explode as luminous hydrogen rich stars and it is tempting to link them to at least so…
We report the discovery of TOI 694 b and TIC 220568520 b, two low-mass stellar companions in eccentric orbits around metal-rich Sun-like stars, first detected by the Transiting Exoplanet Survey Satellite (TESS). TOI 694 b has an orbital period of 48.05131$\pm$0.00019 days and eccentricity of 0.51946$\pm$0.00081, and we derive a mass of 89.0$\pm$5.3 $M_J$ (0.0849$\pm$0.0051 $M_\odot$) and radius of 1.111$\pm$0.017 $R_J$ (0.1142$\pm$0.0017 $R_\odot$). TIC 220568520 b has an orbital period of 18.55769$\pm$0.00039 days and eccentricity of 0.0964$\pm$0.0032, and we derive a mass of 107.2$\pm$5.2 $M…
We present the radial-velocity follow-up of two Kepler planetary transiting candidates (KOI-189 and KOI-686) carried out with the SOPHIE spectrograph at the Observatoire de Haute Provence. These data promptly discard these objects as viable planet candidates and show that the transiting objects are in the regime of very low-mass stars, where a strong discrepancy between observations and models persists for the mass and radius parameters. By combining the SOPHIE spectra with the Kepler light curve and photometric measurements found in the literature, we obtain a full characterization of the tra…
We present 2271 radial velocity measurements taken on 118 single-line binary stars, taken over eight years with the CORALIE spectrograph. The binaries consist of F/G/K primaries and M-dwarf secondaries. They were initially discovered photometrically by the WASP planet survey, as their shallow eclipses mimic a hot-Jupiter transit. The observations we present permit a precise characterisation of the binary orbital elements and mass function. With modelling of the primary star this mass function is converted to a mass of the secondary star. In the future, this spectroscopic work will be combined …
TOI-2155 b: A Massive Brown Dwarf or a Very Low-Mass Star?
Sydney Institute for Astronomy, School of Physics, University of Sydney（悉尼大学物理学院天体物理学研究所）；Department of Physics and McDonnell Center for the Space Sciences, Washington University（华盛顿大学物理系与麦克唐纳太空科学中心）；Institute for Astronomy, University of Hawaii at Manoa（夏威夷大学马诺阿分校天文研究所）；School of Physics and Astronomy, University of Leicester（莱斯特大学物理与天文学学院）；Macquarie University Research Fellow (MQRF)（麦考瑞大学研究研究员（MQRF））；Australian Astronomical Optics, Macquarie University（麦考瑞大学澳大利亚天文光学）；Astrophysics and Space Technologies Research Centre, Macquarie University（麦考瑞大学天体物理学与空间技术中心）
We report the detection of a single transit-like signal in the Kepler data of the slightly evolved F star KIC4918810. The transit duration is ~45 hours, and while the orbital period ($P\sim10$ years) is not well constrained, it is one of the longest among companions known to transit. We calculate the size of the transiting object to be $R_P = 0.910$ $R_J$. Objects of this size vary by orders of magnitude in their densities, encompassing masses between that of Saturn ($0.3$ $M_J$) and stars above the hydrogen-burning limit (~80 $M_J$). Radial-velocity observations reveal that the companion is u…
Ultracool dwarfs have emerged as key targets for searches of transiting exoplanets. Precise estimates of the host parameters (including mass, age, and radius) are fundamental to constrain the physical properties of orbiting exoplanets. We have extended our evolutionary code CLES (Code Liégeois d'Evolution Stellaire) to the ultracool dwarf regime. We include relevant equations of state for H, He, as well as C and O elements to cover the temperature-density regime of ultracool dwarf interiors. For various metallicities, we couple the interior models to two sets of model atmospheres as surface bo…
Blue large-amplitude pulsators (BLAPs) form a small group of hot objects pulsating in a fundamental radial mode with periods of the order of 30 minutes. Proposed evolutionary scenarios explain them as evolved low-mass stars: either ~0.3 M$_\odot$ shell-hydrogen-burning objects with a degenerated helium core, or more massive (0.5 - 0.8) M$_\odot$ core-helium-burning stars, or ~0.7 M$_\odot$ surviving companions of type Ia supernovae. Therefore, their origin remains to be established. Using data from Transiting Exoplanet Survey Satellite, we discovered that HD 133729 is a binary consisting of a …
We report the detection of 8.914-hr variability in both optical and ultraviolet light curves of LP 40-365 (also known as GD 492), the prototype for a class of partly burnt runaway stars that have been ejected from a binary due to a thermonuclear supernova event. We first detected this 1.0% amplitude variation in optical photometry collected by the Transiting Exoplanet Survey Satellite. Re-analysis of observations from the Hubble Space Telescope at the TESS period and ephemeris reveal a 5.8% variation in the ultraviolet of this 9800 K stellar remnant. We propose that this 8.914-hr photometric v…
As part of a large investigation with Hubble Space Telescope to study the faintest stars within the globular cluster Omega Centauri, in this work we present early results on the multiplicity of its main sequence (MS) stars, based on deep optical and near-infrared observations. By using appropriate color-magnitude diagrams we have identified, for the first time, the two main stellar populations I, and II along the entire MS, from the turn-off towards the hydrogen-burning limit. We have compared the observations with suitable synthetic spectra of MS stars and conclude that the two MSs are consis…
Pisces-Eridanus (Psc-Eri), a nearby ($d$ $\simeq$ 80-226 pc) stellar stream stretching across $\approx$120 degrees of the sky, was recently discovered with Gaia data. The stream was claimed to be $\approx$1 Gyr old, which would make it an exceptional discovery for stellar astrophysics, as star clusters of that age are rare and tend to be distant, limiting their utility as benchmark samples. We test this old age for Psc-Eri in two ways. First, we compare the rotation periods for 101 low-mass members (measured using time series photometry from the Transiting Exoplanet Survey Satellite, TESS) to …
Measurements of the physical properties of stars at the lower end of the main sequence are scarce. In this context we report masses, radii and surface gravities of ten very-low-mass stars in eclipsing binary systems, with orbital periods of the order of several days. The objects probe the stellar mass-radius relation in the fully convective regime, $M_\star \lesssim 0.35$ M$_\odot$, down to the hydrogen burning mass-limit, $M_{\mathrm{HB}} \sim 0.07$ M$_\odot$. The stars were detected by the WASP survey for transiting extra-solar planets, as low-mass, eclipsing companions orbiting more massive…
Hot subdwarfs are core-helium burning stars that show lower masses and higher temperatures than canonical horizontal branch stars. They are believed to be formed when a red giant suffers an extreme mass-loss episode. Binary interaction is suggested to be the main formation channel, but the high fraction of apparently single hot subdwarfs (up to 30%) has prompted single star formation scenarios to be proposed. If such formation scenarios without interaction were possible, that would also imply the existence of hot subdwarfs in wide binaries that have undergone no interaction. We probe the exist…
About a third of the hot subdwarfs of spectral type B, which are mostly core-helium burning objects on the extreme horizontal branch, are found in close binaries with cool, low-mass stellar, substellar, or white dwarf companions. They can show light variations due to different phenomena. We used light curves from the Transiting Exoplanet Survey Satellite and the \textit{K2} space mission to look for more sdB binaries. Their light curves can be used to study the hot subdwarf primaries and their companions and get orbital, atmospheric, and absolute parameters for those systems. By classifying th…
Dimming and pulsation shock of the coalesced star V838 Monocerotis
University of Minnesota（明尼苏达大学）；University of Tartu（塔尔图大学）；Nordic Optical Telescope（北欧光学望远镜）；Aarhus University（奥胡斯大学）；Leibniz-Institute for Astrophysics Potsdam (AIP)（波茨坦莱布尼茨天体物理研究所）；Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文学中心）
TOI-7154b: A Close-in Massive Brown Dwarf in an Eccentric Orbit
Mizoram University（米佐拉姆大学）；Department of Astronomy, Indiana University（印第安纳大学天文学系）；Sternberg Astronomical Institute Lomonosov Moscow State University（莫斯科国立大学斯滕伯格天文研究所）；Indian Institute of Technology, Gandhinagar（甘地纳加尔印度理工学院）
