46 research outputs found
The Mass of the Candidate Exoplanet Companion to HD136118 from Hubble Space Telescope Astrometry and High-Precision Radial Velocities
We use Hubble Space Telescope Fine Guidance Sensor astrometry and
high-cadence radial velocities for HD136118 from the HET with archival data
from Lick to determine the complete set of orbital parameters for HD136118b. We
find an orbital inclination for the candidate exoplanet of i_{b} = 163.1 +- 3.0
deg. This establishes the actual mass of the object, M_{b} = 42^{+11}_{-18}
MJup, in contrast to the minimum mass determined from the radial velocity data
only, M_{b}sin{i} ~ 12 MJup. Therefore, the low-mass companion to HD 136118 is
now identified as a likely brown dwarf residing in the "brown dwarf desert".Comment: 35 pages, 12 figures, 10 tables. Accepted for publication in
Astrophysical Journa
The Mass of HD 38529 c from Hubble Space Telescope Astrometry and High-Precision Radial Velocities
(Abridged) Hubble Space Telescope (HST) Fine Guidance Sensor astrometric
observations of the G4 IV star HD 38529 are combined with the results of the
analysis of extensive ground-based radial velocity data to determine the mass
of the outermost of two previously known companions. Our new radial velocities
obtained with the Hobby-Eberly Telescope and velocities from the
Carnegie-California group now span over eleven years. With these data we obtain
improved RV orbital elements for both the inner companion, HD 38529 b and the
outer companion, HD 38529 c. We identify a rotational period of HD 38529
(P_{rot}=31.65 +/- 0.17 d) with FGS photometry. We model the combined
astrometric and RV measurements to obtain the parallax, proper motion,
perturbation period, perturbation inclination, and perturbation size due to HD
38529 c. For HD 38529 c we find P = 2136.1 +/- 0.3 d, perturbation semi-major
axis \alpha =1.05 +/-0.06i_{Jup}) companion at
P~194 days. Additional observations (radial velocities and/or Gaia astrometry)
are required to validate an interpretation of HD 38529 d as a planetary-mass
companion. If confirmed, the resulting HD 38529 planetary system may be an
example of a "Packed Planetary System".Comment: Accepted by The Astronomical Journa
APERO: A PipelinE to Reduce Observations -- Demonstration with SPIRou
With the maturation of near-infrared high-resolution spectroscopy, especially
when used for precision radial velocity, data reduction has faced unprecedented
challenges in terms of how one goes from raw data to calibrated, extracted, and
corrected data with required precisions of thousandths of a pixel. Here we
present APERO (A PipelinE to Reduce Observations), specifically focused on
SPIRou, the near-infrared spectropolarimeter on the Canada--France--Hawaii
Telescope (SPectropolarim\`etre InfraROUge, CFHT). In this paper, we give an
overview of APERO and detail the reduction procedure for SPIRou. APERO delivers
telluric-corrected 2D and 1D spectra as well as polarimetry products. APERO
enables precise stable radial velocity measurements on sky (via the LBL
algorithm), good to at least ~2 m/s over the current 5-year lifetime of SPIRou.Comment: Accepted for publication in PASP. 55 pages, 29 figures, 10 pages of
Appendice
GRACES: Gemini remote access to CFHT ESPaDOnS Spectrograph through the longest astronomical fiber ever made (Experimental phase completed.)
The Gemini Remote Access to CFHT ESPaDONS Spectrograph has achieved first
light of its experimental phase in May 2014. It successfully collected light
from the Gemini North telescope and sent it through two 270 m optical fibers to
the the ESPaDOnS spectrograph at CFHT to deliver high-resolution spectroscopy
across the optical region. The fibers gave an average focal ratio degradation
of 14% on sky, and a maximum transmittance of 85% at 800nm. GRACES achieved
delivering spectra with a resolution power of R = 40,000 and R = 66,000 between
400 and 1,000 nm. It has a ~8% throughput and is sensitive to target fainter
than 21st mag in 1 hour. The average acquisition time of a target is around 10
min. This project is a great example of a productive collaboration between two
observatories on Maunakea that was successful due to the reciprocal involvement
of the Gemini, CFHT, and NRC Herzberg teams, and all the staff involved closely
or indirectly.Comment: Presented at SPIE Astronomical Telescopes + Instrumentation 201
Comprehensive High-resolution Chemical Spectroscopy of Barnard's Star with SPIRou
Determination of fundamental parameters of stars impacts all fields of
astrophysics, from galaxy evolution to constraining the internal structure of
exoplanets. This paper presents a detailed spectroscopic analysis of Barnard's
star that compares an exceptionally high-quality (signal-to-noise ratio of
2500 in the band), high-resolution NIR spectrum taken with CFHT/SPIRou
to PHOENIX-ACES stellar atmosphere models. The observed spectrum shows
thousands of lines not identified in the models with a similar large number of
lines present in the model but not in the observed data. We also identify
several other caveats such as continuum mismatch, unresolved contamination and
spectral lines significantly shifted from their expected wavelengths, all of
these can be a source of bias for abundance determination. Out of
observed lines in the NIR that could be used for chemical spectroscopy, we
identify a short list of a few hundred lines that are reliable. We present a
novel method for determining the effective temperature and overall metallicity
of slowly-rotating M dwarfs that uses several groups of lines as opposed to
bulk spectral fitting methods. With this method, we infer = 3231
21 K for Barnard's star, consistent with the value of 3238 11 K
inferred from the interferometric method. We also provide abundance
measurements of 15 different elements for Barnard's star, including the
abundances of four elements (K, O, Y, Th) never reported before for this star.
This work emphasizes the need to improve current atmosphere models to fully
exploit the NIR domain for chemical spectroscopy analysis.Comment: 24 pages, 18 figures, submitted to Ap
A compositional link between rocky exoplanets and their host stars
Stars and planets both form by accreting material from a surrounding disk.
Because they grow from the same material, theory predicts that there should be
a relationship between their compositions. In this study, we search for a
compositional link between rocky exoplanets and their host stars. We estimate
the iron-mass fraction of rocky exoplanets from their masses and radii and
compare it with the compositions of their host stars, which we assume reflect
the compositions of the protoplanetary disks. We find a correlation (but not a
1:1 relationship) between these two quantities, with a slope of >4, which we
interpret as being attributable to planet formation processes. Super-Earths and
super-Mercuries appear to be distinct populations with differing compositions,
implying differences in their formation processes.Comment: Authors' version of the manuscript. Published in Scienc
CO or no CO? Narrowing the CO abundance constraint and recovering the H2O detection in the atmosphere of WASP-127 b using SPIRou
Precise measurements of chemical abundances in planetary atmospheres are
necessary to constrain the formation histories of exoplanets. A recent study of
WASP-127b, a close-in puffy sub-Saturn orbiting its solar-type host star in 4.2
d, using HST and Spitzer revealed a feature-rich transmission spectrum with
strong excess absorption at 4.5 um. However, the limited spectral resolution
and coverage of these instruments could not distinguish between CO and/or CO2
absorption causing this signal, with both low and high C/O ratio scenarios
being possible. Here we present near-infrared (0.9--2.5 um) transit
observations of WASP-127 b using the high-resolution SPIRou spectrograph, with
the goal to disentangle CO from CO2 through the 2.3 um CO band. With SPIRou, we
detect H2O at a t-test significance of 5.3 sigma and observe a tentative (3
sigma) signal consistent with OH absorption. From a joint SPIRou + HST +
Spitzer retrieval analysis, we rule out a CO-rich scenario by placing an upper
limit on the CO abundance of log10[CO]<-4.0, and estimate a log10[CO2] of
-3.7^(+0.8)_(-0.6), which is the level needed to match the excess absorption
seen at 4.5um. We also set abundance constraints on other major C-, O-, and
N-bearing molecules, with our results favoring low C/O (0.10^(+0.10)_(-0.06)),
disequilibrium chemistry scenarios. We further discuss the implications of our
results in the context of planet formation. Additional observations at high and
low-resolution will be needed to confirm these results and better our
understanding of this unusual world.Comment: 23 pages, 13 figures, Submitted for publication in the Monthly Notice
of the Royal Astronomical Societ
SPLUS J142445.34-254247.1: An R-Process Enhanced, Actinide-Boost, Extremely Metal-Poor star observed with GHOST
We report on the chemo-dynamical analysis of SPLUS J142445.34-254247.1, an
extremely metal-poor halo star enhanced in elements formed by the rapid
neutron-capture process. This star was first selected as a metal-poor candidate
from its narrow-band S-PLUS photometry and followed up spectroscopically in
medium-resolution with Gemini South/GMOS, which confirmed its low-metallicity
status. High-resolution spectroscopy was gathered with GHOST at Gemini South,
allowing for the determination of chemical abundances for 36 elements, from
carbon to thorium. At [Fe/H]=-3.39, SPLUS J1424-2542 is one of the lowest
metallicity stars with measured Th and has the highest logeps(Th/Eu) observed
to date, making it part of the "actinide-boost" category of r-process enhanced
stars. The analysis presented here suggests that the gas cloud from which SPLUS
J1424-2542 was formed must have been enriched by at least two progenitor
populations. The light-element (Z<=30) abundance pattern is consistent with the
yields from a supernova explosion of metal-free stars with 11.3-13.4 Msun, and
the heavy-element (Z>=38) abundance pattern can be reproduced by the yields
from a neutron star merger (1.66Msun and 1.27Msun) event. A kinematical
analysis also reveals that SPLUS J1424-2542 is a low-mass, old halo star with a
likely in-situ origin, not associated with any known early merger events in the
Milky Way.Comment: 26 pages, 11 figures, accepted for publication on Ap
Validating AU Microscopii d with Transit Timing Variations
AU Mic is a young (22 Myr), nearby exoplanetary system that exhibits excess transit timing variations (TTVs) that cannot be accounted for by the two known transiting planets nor stellar activity. We present the statistical âvalidationâ of the tentative planet AU Mic d (even though there are examples of âconfirmedâ planets with ambiguous orbital periods). We add 18 new transits and nine midpoint times in an updated TTV analysis to prior work. We perform the joint modeling of transit light curves using EXOFASTv2 and extract the transit midpoint times. Next, we construct an O â C diagram and use Exo-Striker to model the TTVs. We generate TTV log-likelihood periodograms to explore possible solutions for dâs period, then follow those up with detailed TTV and radial velocity Markov Chain Monte Carlo modeling and stability tests. We find several candidate periods for AU Mic d, all of which are near resonances with AU Mic b and c of varying order. Based on our model comparisons, the most-favored orbital period of AU Mic d is 12.73596 ± 0.00793 days ( T _C _,d = 2458340.55781 ± 0.11641 BJD), which puts the three planets near 4:6:9 mean-motion resonance. The mass for d is 1.053 ± 0.511 M _â , making this planet Earth-like in mass. If confirmed, AU Mic d would be the first known Earth-mass planet orbiting a young star and would provide a valuable opportunity in probing a young terrestrial planetâs atmosphere. Additional TTV observations of the AU Mic system are needed to further constrain the planetary masses, search for possible transits of AU Mic d, and detect possible additional planets beyond AU Mic c