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HAT-P-3b: Heavy Elements in Transit

The Hungarian Automated Telescope Network (HATNet) is run out of the Harvard-Smithsonian Center for Astrophysics, with primary stations at Mauna Kea (HI) and on Mt. Hopkins (Arizona). Looking at large fields of stars over many consecutive nights, the automated telescopes involved help astronomers identify the periodic dimming that marks a transiting exoplanet. And with other projects like the Trans-Atlantic Exoplanet Survey (TrES), the XO Project in Maui and the Optical Gravitational Lensing Experiment (OGLE) in Chile operational, transit data are piling up.

All of which is useful indeed, for at present we are just nearing 20 transiting planets detected from ground-based observatories. The discovery paper for the most recent HATnet detection makes an interesting point about the size of our sample, declaring it “…still small enough that individual discoveries often advance our understanding of these objects significantly by pushing the limits of parameter space, either in planet mass, radius, or some other property.”

How true, and a corrective to the notion that we can make quick generalizations about the planets thus far found. At a recent cocktail party, I was button-holed by a man who wanted to know whether or not most solar systems are going to be like our own. I had to explain that the data aren’t remotely available to make such a call, that we are beginning to know some things about particular classes of planets, especially those most readily detected by radial-velocity methods (and early in the data gathering process at that), but that due to the nature of our techniques there are planetary regimes we know little about, including outer gas giants and terrestrial planets in habitable zones.

Transits are a particularly useful kind of detection because astronomers can get good information about the mass and size of such planets, as well as having a shot at learning something about their atmospheres. The new HAT find is designated HAT-P-3b, a planet that turns out to be the smallest transiting world found photometrically (the transits of smaller planets have been noted — among them, GJ 436b — but not before their original detection by radial-velocity methods). The star in question is the K dwarf GSC 03466-00819, now called in the paper HAT-P-3.

Its planet, HAT-P-3b, orbits at a scorching 0.03894 AU, and looks to be about 60 percent Jupiter’s mass, with a radius almost 90 percent that of Jupiter. Theory suggests that radius is consistent with a core of heavy metals of about 75 Earth masses, a finding supported by the metal content of the host star. The paper is Torres et al., “HAT P-3b: A Heavy-Element Rich Planet Transiting a K Dwarf Star,” scheduled to appear in Astrophysical Journal Letters, with preprint available.

Comments on this entry are closed.

  • Adam August 14, 2007, 18:51

    Hi Paul

    Did anyone expect such heavy element rich planets prior to their actual discovery? They’re so counter-intuitive to all our early cosmogonies, though of course science-fiction expected such for years – look at Mesklin, which Hal Clement confirmed via a “ret-con” as an oddly formed heavy element planet before his death just like the transiting planets we’re discovering. The planet itself was always envisaged as an odd-ball – 16 Jupiter masses of ices which formed slow enough to be solid.

  • ljk October 3, 2007, 0:08

    HAT-P-4b: A metal-rich low-density transiting hot Jupiter

    Authors: G. Kovacs (1), G. A. Bakos (2,3), G. Torres (2), A. Sozzetti (2,4), D. W. Latham (2), R. W. Noyes (2), R. P. Butler (5), G. W. Marcy (6), D. A. Fischer (7), J. M. Fernandez (2), G. Esquerdo (2), D. D. Sasselov (2), R. P. Stefanik (2), A. Pal (8), J. Lazar (9), I. Papp (9), P. Sari (9) ((1) Konkoly Observatory, (2) CfA, (3) Hubble Fellow, (4) INAF – Osservatorio Astronomico di Torino, (5) Department of Terrestrial Magnetism, Carnegie Institute of Washington DC, (6) Department of Astronomy, University of California, Berkeley (7) Department of Physics & Astronomy, San Francisco State University (8) Department of Astronomy, Eötvös Loránd University, (9) Hungarian Astronomical Association)

    (Submitted on 2 Oct 2007)

    Abstract: We describe the discovery of HAT-P-4b, a low-density extrasolar planet transiting BD+36 2593, a V = 11.2 mag slightly evolved metal-rich late F star. The planet’s orbital period is 3.056536+/-0.000057 d with a mid-transit epoch of 2,454,245.8154 +/- 0.0003 (HJD). Based on high-precision photometric and spectroscopic data, and by using transit light curve modeling, spectrum analysis and evolutionary models, we derive the following planet parameters: Mp= 0.68 +/- 0.04 MJ, Rp= 1.27 +/- 0.05 RJ, rho = 0.41 +/- 0.06 g cm-3 and a = 0.0446 +/- 0.0012 AU. Because of its relatively large radius, together with its assumed high metallicity of that of its parent star, this planet adds to the theoretical challenges to explain inflated extrasolar planets.

    Comments: 5 pages, accepted for publication in ApJL

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0710.0602v1 [astro-ph]

    Submission history

    From: Gaspar Bakos A [view email]

    [v1] Tue, 2 Oct 2007 19:05:36 GMT (76kb)

    http://arxiv.org/abs/0710.0602

  • ljk March 8, 2008, 19:55

    HAT-P-7b: An Extremely Hot Massive Planet Transiting a Bright Star in the Kepler Field

    Authors: A. Pal (1,2), G. A. Bakos (1,3), G. Torres (1), R. W. Noyes (1), D. W. Latham (1), Geza Kovacs (4), G. W. Marcy (5), D. A. Fischer (6), R. P. Butler (7), D. D. Sasselov (1), B. Sipocz (2,1), G. A. Esquerdo (1), Gabor Kovacs (1), R. Stefanik (1), J. Lazar (8), I. Papp (8), P. Sari (8) ((1) CfA, (2) Department of Astronomy, Eotvos Lorand University, (3) NSF Fellow, (4) Konkoly Observatory, (5) Department of Astronomy, UC Berkeley, (6) Department of Physics and Astronomy, San Francisco State University, (7) Department of Terrestrial Magnetism, Carnegie Institute of Washington, (8) Hungarian Astronomical Association)

    (Submitted on 5 Mar 2008)

    Abstract: We report on the latest discovery of the HATNet project; a very hot giant planet orbiting a bright (V = 10.5) star with a small semi-major axis of a = 0.0377 +/- 0.0005 AU. Ephemeris for the system is P = 2.2047299 +/- 0.0000040 days, mid-transit time E = 2,453,790.2593 +/- 0.0010 (BJD). Based on the available spectroscopic data on the host star and photometry of the system, the planet has a mass of Mp = 1.78+/-^{0.08}_{0.05} MJup and radius of Rp = 1.36+/-^{0.20}_{0.09} RJup. The parent star is a slightly evolved F6 star with M = 1.47+/-^{0.08}_{-0.05} Msun,R = 1.84+/-^{0.23}_{0.11} Rsun, Teff = 6350 +/- 80 K, and metallicity [Fe/H] = +0.26 +/- 0.08.

    The relatively hot and large host star, combined with the close orbit of the planet, yield a very high planetary irradiance of (4.71+/-^{1.44}_{0.05}) 10^9 erg cm^{-2}s^{-1}, which places the planet near the top of the pM class of irradiated planets as defined by Fortney et al. (2007). If as predicted by Fortney et al. (2007) the planet re-radiates its absorbed energy before distributing it to the night side, the day-side temperature should be about (2730+/-^{150}_{100}) K. Because the host star is quite bright, measurement of the secondary eclipse should be feasible for ground-based telescopes, providing a good opportunity to compare the predictions of current hot Jupiter atmospheric models with the observations. Moreover, the host star falls in the field of the upcoming Kepler mission; hence extensive space-borne follow-up, including not only primary transit and secondary eclipse observations but also asteroseismology, will be possible.

    Comments: Accepted for publication in ApJ, 8 pages, 2 figures

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0803.0746v1 [astro-ph]

    Submission history

    From: Andras Pal Mr. [view email]

    [v1] Wed, 5 Mar 2008 21:12:22 GMT (138kb)

    http://arxiv.org/abs/0803.0746

  • ljk January 6, 2009, 0:22

    HAT-P-11b: A Super-Neptune Planet Transiting a Bright K Star in the Kepler Field

    Authors: G. Á. Bakos (1,2), G. Torres (1), A. Pál (1,4), J. Hartman (1), Géza Kovács (3), R. W. Noyes (1), D. W. Latham (1), D. D. Sasselov (1), B. Sipőcz (1,4), G. A. Esquerdo (1), D. A. Fischer (5), J. A. Johnson (6), G. W. Marcy (7), R. P. Butler (8), H. Isaacson (5), A. Howard (7), S. Vogt (9), Gábor Kovács (1), J. Fernandez (1), A. Moór (3), R. P. Stefanik (1), J. Lázár (9), I. Papp (9), P. Sári (9), ((1) CfA, (2) NSF Fellow, (3) Konkoly Observatory, (4) ELTE, (5) SFSU, (6) IfA, (7) UC Berkeley, (8) Carnegie Institute of Washington, (9) UC Santa Cruz, (10) Hungarian Astronomical Association)

    (Submitted on 2 Jan 2009)

    Abstract: We report on the discovery of HAT-P-11b, the smallest radius transiting extrasolar planet (TEP), and the first hot Neptune discovered to date by transit searches.

    HAT-P-11b orbits the bright (V=9.59) and metal rich ([Fe=H] = +0.31 +/- 0.05) K4 dwarf star GSC 03561-02092 with P = 4.8878162 +/- 0.0000071 days and produces a transit signal with depth of 4.2 mmag; the shallowest found by transit searches that is due to a confirmed planet.

    We present a global analysis of the available photometric and radial-velocity data that result in stellar and planetary parameters, with simultaneous treatment of systematic variations.

    The planet, like its near-twin GJ 436b, is somewhat larger than Neptune (17 Mearth, 3.8 Rearth) both in mass Mp = 0.081 +/- 0.009 MJup (25.8 +/- 2.9 Mearth) and radius Rp = 0.422 +/- 0.014 RJup (4.73 +/- 0.16 Rearth). HAT-P-11b orbits in an eccentric orbit with e = 0.198 +/- 0.046 and omega = 355.2 +/- 17.3 deg, causing a reflex motion of its parent star with amplitude 11.6 +/- 1.2 m/s, a challenging detection due to the high level of chromospheric activity of the parent star.

    Our ephemeris for the transit events is Tc = 2454605.89132 +/- 0.00032 (BJD), with duration 0.0957 +/- 0.0012 d, and secondary eclipse epoch of 2454608.96 +/- 0.15 d (BJD). The basic stellar parameters of the host star are M* = 0.809 +/- ^0.020_0.027 Msun, R* = 0.752 +/- 0.021 Rsun and Teff = 4780 +/- 50 K.

    Importantly, HAT-P-11 will lie on one of the detectors of the forthcoming Kepler mission; this should make possible fruitful investigations of the detailed physical characteristic of both the planet and its parent star at unprecedented precision.

    Comments: Submitted to ApJ, 23 pages, 14 figures, 5 tables

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0901.0282v1 [astro-ph]

    Submission history

    From: Gaspar Bakos A [view email]

    [v1] Fri, 2 Jan 2009 21:04:22 GMT (1319kb)

    http://arxiv.org/abs/0901.0282