Browsing by Subject "radial-velocity"

Now showing 1 - 6 of 6

The California Planet Survey. I. Four New Giant Exoplanets
(2010-10) Howard, Andrew W.; Johnson, John A.; Marcy, Geoffrey W.; Fischer, Debra A.; Wright, Jason T.; Bernat, David; Henry, Gregory W.; Peek, Kathryn M. G.; Isaacson, Howard; Apps, Kevin; Endl, Michael; Cochran, William D.; Valenti, Jeff A.; Anderson, Jay; Piskunov, Nikolai E.; Endl, Michael; Cochran, William D.
We present precise Doppler measurements of four stars obtained during the past decade at Keck Observatory by the California Planet Survey (CPS). These stars, namely, HD 34445, HD 126614, HD 13931, and Gl 179, all show evidence for a single planet in Keplerian motion. We also present Doppler measurements from the Hobby-Eberly Telescope (HET) for two of the stars, HD 34445 and Gl 179, that confirm the Keck detections and significantly refine the orbital parameters. These planets add to the statistical properties of giant planets orbiting near or beyond the ice line, and merit follow-up by astrometry, imaging, and space-borne spectroscopy. Their orbital parameters span wide ranges of planetary minimum mass (M sin i = 0.38-1.9 M(Jup)), orbital period (P = 2.87-11.5 yr), semimajor axis (a = 2.1-5.2 AU), and eccentricity (e = 0.02-0.41). HD 34445 b (P = 2.87 yr, M sin i = 0.79 MJup, e = 0.27) is a massive planet orbiting an old, G-type star. We announce a planet, HD 126614 Ab, and an M dwarf, HD 126614 B, orbiting the metal-rich star HD 126614 (which we now refer to as HD 126614 A). The planet, HD 126614 Ab, has minimum mass M sin i = 0.38 MJup and orbits the stellar primary with period P = 3.41 yr and orbital separation a = 2.3 AU. The faint M dwarf companion, HD 126614 B, is separated from the stellar primary by 489 mas (33 AU) and was discovered with direct observations using adaptive optics and the PHARO camera at Palomar Observatory. The stellar primary in this new system, HD 126614 A, has the highest measured metallicity ([ Fe/ H] = + 0.56) of any known planet-bearing star. HD 13931 b (P = 11.5 yr, M sin i = 1.88 MJup, e = 0.02) is a Jupiter analog orbiting a near solar twin. Gl 179 b (P = 6.3 yr, M sin i = 0.82 M(Jup), e = 0.21) is a massive planet orbiting a faint M dwarf. The high metallicity of Gl 179 is consistent with the planet-metallicity correlation among M dwarfs, as documented recently by Johnson & Apps.
Characterizing The Cool KOIs. VII. Refined Physical Properties Of The Transiting Brown Dwarf LHS 6343 C
(2015-02) Montet, Benjamin T.; Johnson, John A.; Muirhead, Phillip S.; Villar, Ashley; Vassallo, Corinne; Baranec, Christoph; Law, Nicholas M.; Riddle, Reed; Marcy, Geoffrey W.; Howard, Andrew W.; Isaacson, Howard; Vassallo, Corinne
We present an updated analysis of LHS 6343, a triple system in the Kepler field which consists of a brown dwarf transiting one member of a widely separated M+M binary system. By analyzing the full Kepler data set and 34 Keck/HIgh Resolution Echelle Spectrometer radial velocity observations, we measure both the observed transit depth and Doppler semiamplitude to 0.5% precision. With Robo-AO and Palomar/PHARO adaptive optics imaging as well as TripleSpec spectroscopy, we measure a model-dependent mass for LHS 6343 C of 62.1 +/- 1.2 M-Jup and a radius of 0.783 +/- 0.011 R-Jup. We detect the secondary eclipse in the Kepler data at 3.5 sigma, measuring e cos omega = 0.0228 +/- 0.0008. We also derive a method to measure the mass and radius of a star and transiting companion directly, without any direct reliance on stellar models. The mass and radius of both objects depend only on the orbital period, stellar density, reduced semimajor axis, Doppler semiamplitude, eccentricity, and inclination, as well as the knowledge that the primary star falls on the main sequence. With this method, we calculate a mass and radius for LHS 6343 C to a precision of 3% and 2%, respectively.
Cousins Photometry and Temperatures for the Hyades, Coma, NGC 752, Praesepe, and M67
(2008-05) Taylor, B. J.; Joner, M. D.; Jeffery, E. J.; Jeffery, E. J.
In this paper, new Cousins VRI data are presented for NGC 752 and Praesepe, and new and extant data are combined into an augmented database for M67. For those three clusters, catalogs containing Cousins VRI photometry, reddening-corrected values of (V -K)(J), and temperatures are produced. The same is done for Coma by using both previously published and newly derived Cousins photometry. An extant set of catalogs for the Hyades is updated to include V magnitudes and values of (R -I)(C) that were published after the original catalogs appeared. Finally, M67 V magnitudes published previously by Sandquist are corrected for an effect that depends on location on the face of the cluster. The corrected data and values of (V -I)(C) given by Sandquist are then set out in a supplementary catalog. Data files containing all of these catalogs are deposited in the CDS archives. To assess the quality of the data in the catalogs, the consistency of extant Cousins VRI databases is tested by performing analyses with the following features: (1) quantities as small as a few millimags are regarded as meaningful; (2) statistical analysis is applied; (3) no use is made of data other than VRI measurements and comparable results; (4) no inferences are drawn from color-magnitude comparisons; (5) pertinent data that have not been included previously are analyzed; and (6) results based on direct comparisons of stellar groups at the telescope are featured. In this way, it is found that our updated M67 color data and those of Sandquist are on the E region zero point. In contrast, values of (V -I)(C) from Montgomery and collaborators are found to be too red by 27 +/- 3 mmag, with an even larger offset being likely for unpublished data from Richer and his collaborators. Zero-point tests of our Cousins VRI colors for Coma, Praesepe, and NGC 752 are also satisfactory. Scale factor tests of the M67 colors are performed, and a likely scale factor error in the Montgomery et al. colors is found. However, it appears at present that the scale factors of our M67 colors and those of Sandquist are satisfactory. For the most part, zero-point tests of the assembled V magnitudes are also satisfactory, although it is found that further work on the V magnitudes for Praesepe and M67 would be useful. To put these results in perspective, it is pointed out that photometric tests that are satisfactory at the few-millimag level have been published for some two decades and so are not appearing for the first time in this paper.
The Hot R Coronae Borealis Star DY Centauri is a Binary
(2012-11) Rao, N. Kameswara; Lambert, David L.; Garcia-Hernandez, D. A.; Jeffery, C. Simon; Woolf, Vincent M.; McArthur, Barbara; Rao, N. Kameswara; Lambert, David L.; McArthur, Barbara
The remarkable hot R Coronae Borealis (RCB) star DY Cen is revealed to be the first and only binary system to be found among the RCB stars and their likely relatives, including the extreme helium stars and the hydrogen-deficient carbon stars. Radial velocity determinations from 1982 to 2010 have shown that DY Cen is a single-lined spectroscopic binary in an eccentric orbit with a period of 39.67 days. It is also one of the hottest and most H-rich member of the class of RCB stars. The system may have evolved from a common envelope to its current form.
On The Binary Helium Star DY Centauri: Chemical Composition And Evolutionary State
(2014-10) Pandey, Gajendra; Rao, N. Kameswara; Jeffery, C. Simon; Lambert, David L.; Lambert, David L.
DY Cen has shown a steady fading of its visual light by about one magnitude in the last 40 yr, suggesting a secular increase in its effective temperature. We have conducted non-local thermodynamic equilibrium (LTE) and LTE abundance analyses to determine the star's effective temperature, surface gravity, and chemical composition using high-resolution spectra obtained over two decades. The derived stellar parameters for three epochs suggest that DY Cen has evolved at a constant luminosity and has become hotter by about 5000 K in 23 yr. We show that the derived abundances remain unchanged for the three epochs. The derived abundances of the key elements, including F and Ne, are as observed for the extreme helium stars resulting from a merger of a He white dwarf with a C-O white dwarf. Thus DY Cen by chemical composition appears to also be a product of a merger of two white dwarfs. This appearance seems to be at odds with the recent suggestion that DY Cen is a single-lined spectroscopic binary.
Three Red Giants With Substellar-Mass Companions
(2015-04) Niedzielski, A.; Wolszczan, A.; Nowak, G.; Adamow, M.; Kowalik, K.; Maciejewski, G.; Deka-Szymankiewicz, B.; Adamczyk, M.; Adamow, M.
We present three giant stars from the ongoing Penn State-Torun Planet Search with the Hobby-Eberly Telescope, which exhibit radial velocity ( RV) variations that point to the presence of planetary-mass companions around them. BD + 49 828 is a M 1.52 +/- 0.22 M-circle dot K0 giant with a m sin i = 1.6(-0.2)(+0.4) M-J minimum mass companion in a = 4.2(-0.2)(+0.32) AU (2590(-180)(+300)d), e = 0.35(-0.10)(+0.24) orbit. HD 95127, a logL/L-circle dot = 2.28 +/- 0.38, R = 20 +/- 9 R-circle dot, M = 1.20 +/- 0.22 M-circle dot K0 giant, has a m sin i = 5.01(-0.44)(+0.61) M-J minimum mass companion in a = 1.28(-0.01)(+0.01) AU (482(-5)(+5)d), e = 0.11(-0.06)(+0.15) orbit. Finally, HD 216536 is a M = 1.36 +/- 0.38 M-circle dot K0 giant with a m sin i = 1.47(-0.20)(+0.12) M-J minimum mass companion in a = 0.609(-0.002)(+0.002) AU (148.6(-0.7)(+0.7)d), e = 0.38(-0.10)(+0.12) orbit. Both. HD 95127 b and HD 216536 b in their compact orbits. are very close to the engulfment zone and hence prone to ingestion in the near future. BD+49 828 b is among the longest-period planets detected with the RV technique until now and it will remain unaffected by stellar evolution up to a very late stage of its host. We discuss general properties of planetary systems around evolved stars and planet survivability using existing data on exoplanets in more detail.