skip to main content

Title: Independent Validation of the Temperate Super-Earth HD 79211 b using HARPS-N

We present high-precision radial velocities (RVs) from the HARPS-N spectrograph for HD 79210 and HD 79211, two M0V members of a gravitationally bound binary system. We detect a planet candidate with a period of24.4210.017+0.016days around HD 79211 in these HARPS-N RVs, validating the planet candidate originally identified in CARMENES RV data alone. Using HARPS-N, CARMENES, and RVs spanning a total of 25 yr, we further refine the planet candidate parameters toP= 24.422 ± 0.014 days,K= 3.19 ± 0.27 m s−1,Msini= 10.6 ± 1.2M, anda= 0.142 ± 0.005 au. We do not find any additional planet candidate signals in the data of HD 79211, nor do we find any planet candidate signals in HD 79210. This system adds to the number of exoplanets detected in binaries with M-dwarf members and serves as a case study for planet formation in stellar binaries.

; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more » ; ; ; ; ; ; ; ; ; ; ; « less
Publication Date:
Journal Name:
The Astronomical Journal
Page Range or eLocation-ID:
Article No. 38
DOI PREFIX: 10.3847
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    We present a chemodynamical study of the Grus I ultra-faint dwarf galaxy (UFD) from medium-resolution (R∼ 11,000) Magellan/IMACS spectra of its individual member stars. We identify eight confirmed members of Grus I, based on their low metallicities and coherent radial velocities, and four candidate members for which only velocities are derived. In contrast to previous work, we find that Grus I has a very low mean metallicity of 〈[Fe/H]〉 = −2.62 ± 0.11 dex, making it one of the most metal-poor UFDs. Grus I has a systemic radial velocity of −143.5 ± 1.2 km s−1and a velocity dispersion ofσrv=2.50.8+1.3km s−1, which results in a dynamical mass ofM1/2(rh)=84+12×105Mand a mass-to-light ratio ofM/LV=440250+650M/L. Under the assumption of dynamical equilibrium, our analysis confirms that Grus I is a dark-matter-dominated UFD (M/L> 80M/L). However, we do not resolve a metallicity dispersion (σ[Fe/H]< 0.44 dex). Our results indicate that Grus I is a fairly typical UFD with parameters that agree with mass–metallicity and metallicity-luminosity trends for faint galaxies. This agreement suggests that Grus I has not lost an especially significant amount of mass from tidal encounters with the Milky Way, in linemore »with its orbital parameters. Intriguingly, Grus I has among the lowest central densities (ρ1/23.52.1+5.7×107Mkpc−3) of the UFDs that are not known to be tidally disrupting. Models of the formation and evolution of UFDs will need to explain the diversity of these central densities, in addition to any diversity in the outer regions of these relic galaxies.

    « less
  2. Abstract

    We detail the follow-up and characterization of a transiting exo-Venus identified by TESS, GJ 3929b (TOI-2013b), and its nontransiting companion planet, GJ 3929c (TOI-2013c). GJ 3929b is an Earth-sized exoplanet in its star’s Venus zone (Pb= 2.616272 ± 0.000005 days; Sb=17.30.7+0.8S) orbiting a nearby M dwarf. GJ 3929c is most likely a nontransiting sub-Neptune. Using the new, ultraprecise NEID spectrometer on the WIYN 3.5 m Telescope at Kitt Peak National Observatory, we are able to modify the mass constraints of planet b reported in previous works and consequently improve the significance of the mass measurement to almost 4σconfidence (Mb= 1.75 ± 0.45M). We further adjust the orbital period of planet c from its alias at 14.30 ± 0.03 days to the likely true period of 15.04 ± 0.03 days, and we adjust its minimum mass tomsini= 5.71 ± 0.92M. Using the diffuser-assisted ARCTIC imager on the ARC 3.5 m telescope at Apache Point Observatory, in addition to publicly available TESS and LCOGT photometry, we are able to constrain the radius of planet b toRp= 1.09 ± 0.04R. GJ 3929b is a top candidate for transmission spectroscopy in its size regime (TSM = 14more »± 4), and future atmospheric studies of GJ 3929b stand to shed light on the nature of small planets orbiting M dwarfs.

    « less
  3. Abstract

    Populating the exoplanet mass–radius diagram in order to identify the underlying relationship that governs planet composition is driving an interdisciplinary effort within the exoplanet community. The discovery of hot super-Earths—a high-temperature, short-period subset of the super-Earth planet population—has presented many unresolved questions concerning the formation, evolution, and composition of rocky planets. We report the discovery of a transiting, ultra-short-period hot super-Earth orbitingTOI-1075(TIC351601843), a nearby (d= 61.4 pc) late-K/early-M-dwarf star, using data from the Transiting Exoplanet Survey Satellite. The newly discovered planet has a radius of 1.7910.081+0.116Rand an orbital period of 0.605 day (14.5 hr). We precisely measure the planet mass to be 9.951.30+1.36Musing radial velocity measurements obtained with the Planet Finder Spectrograph mounted on the Magellan II telescope. Our radial velocity data also show a long-term trend, suggesting an additional planet in the system. While TOI-1075 b is expected to have a substantial H/He atmosphere given its size relative to the radius gap, its high density (9.321.85+2.05g cm−3) is likely inconsistent with this possibility. We explore TOI-1075 b’s location relative to the M-dwarf radius valley, evaluate the planet’s prospects for atmospheric characterization, andmore »discuss potential planet formation mechanisms. Studying the TOI-1075 system in the broader context of ultra-short-period planetary systems is necessary for testing planet formation and evolution theories and density-enhancing mechanisms and for future atmospheric and surface characterization studies via emission spectroscopy with the JWST.

    « less
  4. Abstract

    We present a measurement of the intrinsic space density of intermediate-redshift (z∼ 0.5), massive (M*∼ 1011M), compact (Re∼ 100 pc) starburst (ΣSFR∼ 1000Myr−1kpc−1) galaxies with tidal features indicative of them having undergone recent major mergers. A subset of them host kiloparsec-scale, > 1000 km s−1outflows and have little indication of AGN activity, suggesting that extreme star formation can be a primary driver of large-scale feedback. The aim for this paper is to calculate their space density so we can place them in a better cosmological context. We do this by empirically modeling the stellar populations of massive, compact starburst galaxies. We determine the average timescale on which galaxies that have recently undergone an extreme nuclear starburst would be targeted and included in our spectroscopically selected sample. We find that massive, compact starburst galaxies targeted by our criteria would be selectable for14824+27Myr and have an intrinsic space densitynCS(1.10.3+0.5)×106Mpc3. This space density is broadly consistent with ourz∼ 0.5 compact starbursts being the most extremely compact and star-forming low-redshift analogs of the compact star-forming galaxies in the early universe, as well as them being the progenitors to a fraction of intermediate-redshift, post-starburst, andmore »compact quiescent galaxies.

    « less
  5. Abstract

    We report the discovery of MAGAZ3NE J095924+022537, a spectroscopically confirmed protocluster atz=3.36650.0012+0.0009around a spectroscopically confirmedUVJ-quiescent ultramassive galaxy (UMG;M=2.340.34+0.23×1011M) in the COSMOS UltraVISTA field. We present a total of 38 protocluster members (14 spectroscopic and 24 photometric), including the UMG. Notably, and in marked contrast to protoclusters previously reported at this epoch that have been found to contain predominantly star-forming members, we measure an elevated fraction of quiescent galaxies relative to the coeval field (73.316.9+26.7%versus11.64.9+7.1%for galaxies with stellar massM≥ 1011M). This high quenched fraction provides a striking and important counterexample to the seeming ubiquitousness of star-forming galaxies in protoclusters atz> 2 and suggests, rather, that protoclusters exist in a diversity of evolutionary states in the early universe. We discuss the possibility that we might be observing either “early mass quenching” or nonclassical “environmental quenching.” We also present the discovery of MAGAZ3NE J100028+023349, a second spectroscopically confirmed protocluster, at a very similar redshift ofz=3.38010.0281+0.0213. We present a total of 20 protocluster members, 12 of which are photometric and eight spectroscopic including a poststarburst UMG (M=2.950.20+0.21×1011M). Protoclusters MAGAZ3NE J0959more »and MAGAZ3NE J1000 are separated by 18′ on the sky (35 comoving Mpc), in good agreement with predictions from simulations for the size of “Coma”-type cluster progenitors at this epoch. It is highly likely that the two UMGs are the progenitors of Brightest Cluster Galaxies seen in massive virialized clusters at lower redshift.

    « less