The M Dwarf GJ 436 and its Neptune‐Mass Planet

Maness, H.; Marcy, Geoffrey W.; Ford, Eric B.; Hauschildt, P. H.; Shreve, Alexander T.; Basri, Gibor; Butler, R. Paul; Vogt, Steven S.

doi:10.1086/510689

Cited by 143 publications

(98 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One is GJ 436 b, a Neptune-mass planet initially detected with Doppler measurements (Butler et al 2006;Maness et al 2007) and subsequently seen in transit (Gillon et al 2007b). Finding that GJ 436 b undergoes transits has enabled a wealth of detailed studies such as the determinations of the planet's true mass and radius and measurements of its effective temperature and orbital eccentricity (Gillon et al 2007a;Demory et al 2007;Deming et al 2007).…”

Section: Introductionmentioning

confidence: 99%

The HARPS search for southern extra-solar planets

Bonfils

Delfosse

Udry

et al. 2013

A&A

655

760

View full text Add to dashboard Cite

Context. Searching for planets around stars with different masses probes the outcome of planetary formation for different initial conditions. The low-mass M dwarfs are also the most frequent stars in our Galaxy and potentially therefore, the most frequent planet hosts. Aims. This drives observations of a sample of 102 southern nearby M dwarfs, using a fraction of our guaranteed time on the ESO/HARPS spectrograph. We observed 460 hours and gathered 1965 precise (∼ 1 − 3 m/s) radial velocities, spanning the period from Feb. 11th, 2003 to Apr. 1st 2009. Methods. This paper makes available the sample's time series, presents their precision and variability. We apply systematic searches for long-term trends, periodic signals and Keplerian orbits (from 1 to 4 planets). We analyze the subset of stars with detected signals and apply several diagnostics to discriminate whether the observed Doppler shifts are caused by stellar surface inhomogeneities or by the radial pull of orbiting planets. To prepare for the statistical view of our survey we also compute the limits on possible unseen signals, and derive a first estimate of the frequency of planets orbiting M dwarfs. Results. We recover the planetary signals corresponding to 9 planets already announced by our group (Gl 176 b, Gl 581 b, c, d & e, Gl 674 b, Gl 433 b, Gl 667C b and Gl 667C c). We present radial velocities that confirm GJ 849 hosts a Jupiter-mass planet, plus a long-term radial-velocity variation. We also present RVs that precise the planetary mass and period of Gl 832b. We detect longterm RV changes for Gl 367, Gl 680 and Gl 880 betraying yet unknown long-period companions. We identify candidate signals in the radial-velocity time series of 11 other M dwarfs. Spectral diagnostics and/or photometric observations demonstrate however that they are most probably caused by stellar surface inhomogeneities. Finally, we find our survey sensitive to few Earth-mass planets for periods up to several hundred days. We derive a first estimate of the occurrence of M-dwarf planets as a function of their minimum mass and orbital period. In particular, we find that giant planets (m sin i = 100 − 1, 000 M ⊕ ) have a low frequency (e.g. f 1% for P = 1 − 10 d and f = 0.02 +0.03 −0.01 for P = 10 − 100 d), whereas super-Earths (m sin i = 1 − 10 M ⊕ ) are likely very abundant ( f = 0.36 +0.25 −0.10 for P = 1 − 10 d and f = 0.35 +0.45 −0.11 for P = 10 − 100 d). We also obtained η ⊕ = 0.41 +0.54 −0.13 , the frequency of habitable planets orbiting M dwarfs (1 ≤ m sin i ≤ 10 M ⊕ ). For the first time, η ⊕ is a direct measure and not a number extrapolated from the statistic of more massive and/or shorter-period planets.

show abstract

Section: Introductionmentioning

confidence: 99%

The HARPS search for southern extra-solar planets

Bonfils

Delfosse

Udry

et al. 2013

A&A

655

760

View full text Add to dashboard Cite

show abstract

“…Large samples of M dwarfs have been characterised by means of near-infrared indices in the recent works by Newton et al (2014) and Gaidos et al (2014). On the other hand, spectral synthesis has been tested in several works, usually on small numbers of stars and mainly focusing on strong atomic lines or on spectral windows known to be less affected by molecular lines (Woolf & Wallerstein 2005;Bean et al 2006;Maness et al 2007;Önehag et al 2012;Rajpurohit et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Stellar parameters of early-M dwarfs from ratios of spectral features at optical wavelengths

Maldonado

Affer

Micela

et al. 2015

A&A

View full text Add to dashboard Cite

Context. Low-mass stars have been recognised as promising targets in the search for rocky, small planets with the potential of supporting life. As a consequence, Doppler search programmes using high-resolution spectrographs like HARPS or HARPS-N are providing huge quantities of optical spectra of M dwarfs. However, determining the stellar parameters of M dwarfs using optical spectra has proven to be challenging. Aims. We aim to calibrate empirical relationships to determine accurate stellar parameters for early-M dwarfs (spectral types M0-M4.5) using the same spectra as those that are used for radial velocity determinations, without the necessity of acquiring IR spectra or relying on atmospheric models and/or photometric calibrations. Methods. Our methodology consists of using ratios of pseudo-equivalent widths of spectral features as a temperature diagnostic, a technique frequently used in solar-type stars. Stars with effective temperatures obtained from interferometric estimates of their radii are used as calibrators. Empirical calibrations for the spectral type are also provided. Combinations of features and ratios of features are used to derive calibrations for the stellar metallicity. Our methods are then applied to a large sample of M dwarfs that are currently being observed in the framework of the HARPS GTO search for extrasolar planets. The derived temperatures and metallicities are used together with photometric estimates of mass, radius, and surface gravity to calibrate empirical relationships for these parameters. Results. A long list of spectral features in the optical spectra of early-M dwarfs was identified. This list shows that the pseudoequivalent width of roughly 43% of the features is strongly anticorrelated with the effective temperature. The correlation with the stellar metallicity is weaker. A total of 112 temperature sensitive ratios were identified and calibrated over the range 3100−3950 K, providing effective temperatures with typical uncertainties of about 70 K. Eighty-two ratios of pseudo-equivalent widths of features were calibrated to derive spectral types within 0.5 subtypes for stars with spectral types between K7V and M4.5V. We calibrated 696 combinations of the pseudo-equivalent widths of individual features and temperature-sensitive ratios for the stellar metallicity over a metallicity range from −0.54 to +0.24 dex, with estimated uncertainties in the range of 0.07−0.10 dex. We provide our own empirical calibrations for stellar mass, radius, and surface gravity. These parameters depend on the stellar metallicity. For a given effective temperature, lower metallicities predict lower masses and radii as well as higher gravities.

show abstract

“…This exoplanet is even more interesting because it shows a significant eccentricity that appears to disagree with tidal circularisation timescales and with the age of the system for an isolated planet (e.g., Demory et al 2007). Different authors tried to explain this with different mechanisms, usually with the presence of a companion (e.g., Maness et al 2007;Deming et al 2007;Alonso et al 2008;Ribas et al 2008Ribas et al , 2009Cáceres et al 2009). Beust et al (2012) summarise those different explanations and propose an original solution based on a Kozai mechanism (Kozai 1962) assuming a distant disruptive body.…”

Section: Introductionmentioning

confidence: 99%

A global analysis ofSpitzerand new HARPS data confirms the loneliness and metal-richness of GJ 436 b

Lanotte

Gillon

Demory

et al. 2014

A&A

130

135

View full text Add to dashboard Cite

Context. GJ 436b is one of the few transiting warm Neptunes for which a detailed characterisation of the atmosphere is possible, whereas its non-negligible orbital eccentricity calls for further investigation. Independent analyses of several individual datasets obtained with Spitzer have led to contradicting results attributed to the different techniques used to treat the instrumental effects. Aims. We aim at investigating these previous controversial results and developing our knowledge of the system based on the full Spitzer photometry dataset combined with new Doppler measurements obtained with the HARPS spectrograph. We also want to search for additional planets. Methods. We optimise aperture photometry techniques and the photometric deconvolution algorithm DECPHOT to improve the data reduction of the Spitzer photometry spanning wavelengths from 3-24 µm. Adding the high-precision HARPS radial velocity data, we undertake a Bayesian global analysis of the system considering both instrumental and stellar effects on the flux variation.Results. We present a refined radius estimate of R P = 4.10 ± 0.16 R ⊕ , mass M P = 25.4 ± 2.1 M ⊕ , and eccentricity e = 0.162 ± 0.004 for GJ 436b. Our measured transit depths remain constant in time and wavelength, in disagreement with the results of previous studies. In addition, we find that the post-occultation flare-like structure at 3.6 µm that led to divergent results on the occultation depth measurement is spurious. We obtain occultation depths at 3.6, 5.8, and 8.0 µm that are shallower than in previous works, in particular at 3.6 µm. However, these depths still appear consistent with a metal-rich atmosphere depleted in methane and enhanced in CO/CO 2 , although perhaps less than previously thought. We could not detect a significant orbital modulation in the 8 µm phase curve. We find no evidence of a potential planetary companion, stellar activity, or a stellar spin-orbit misalignment. Conclusions. Recent theoretical models invoking high-metallicity atmospheres for warm Neptunes are a reasonable match to our results, but we encourage new modelling efforts based on our revised data. Future observations covering a wide wavelength range of GJ 436b and other Neptune-class exoplanets will further illuminate their atmosphere properties, whilst future accurate radial velocity measurements might explain the eccentricity.

show abstract

The M Dwarf GJ 436 and its Neptune‐Mass Planet

Cited by 143 publications

References 44 publications

The HARPS search for southern extra-solar planets

The HARPS search for southern extra-solar planets

Stellar parameters of early-M dwarfs from ratios of spectral features at optical wavelengths

A global analysis ofSpitzerand new HARPS data confirms the loneliness and metal-richness of GJ 436 b

Contact Info

Product

Resources

About