scholarly journals New Pulse Timing Measurements of the sdBV Star CS 1246

2017 ◽  
Vol 26 (1) ◽  
Author(s):  
Zackary L. Hutchens ◽  
Brad N. Barlow ◽  
Alan Vasquez Soto ◽  
Dan E. Reichart ◽  
Josh B. Haislip ◽  
...  
Keyword(s):  
Radial Pulsation ◽  
Minimum Mass ◽  
Velocity Measurements ◽  
Pulse Timing ◽  
Gravitational Influence ◽  
Low Mass ◽  
Robotic Telescope ◽  
M Dwarf ◽  
Long Term Trend

AbstractCS 1246 is a hot subdwarf B star discovered in 2009 to exhibit a single, large-amplitude radial pulsation. An O-C diagram constructed from this mode revealed reflex motion due to the presence of a low-mass M dwarf, as well as a long-term trend consistent with a decrease in the pulsational period. The orbital reflex motion was later confirmed with radial velocity measurements. Using eight years of data collected with the Skynet Robotic Telescope Network, we show that the pulsation amplitude of CS 1246 is decaying nonlinearly. We also present an updated O-C diagram, which might now indicate a positive Ṗ and a new 2.09 ± 0.05 yr oscillation consistent with orbital reflex motion of the entire inner sdB+dM binary, possibly due to the gravitational influence of a circumbinary planet with minimum mass

scholarly journals The mass balance of McCall Glacier, Brooks Range, Alaska, U.S.A.; its regional relevance and implications for climate change in the Arctic

1998 ◽  
Vol 44 (147) ◽  
pp. 333-351 ◽  
Author(s):  
B.T. Rabus ◽  
K. A. Echelmeyer
Keyword(s):  
Mass Balance ◽  
The Arctic ◽  
Balance Model ◽  
Mass Balances ◽  
Arctic Alaska ◽  
Low Mass ◽  
Length Changes ◽  
Arctic Glacier ◽  
Long Term Trend

AbstractMcCall Glacier has the only long-term mass-balance record in Arctic-Alaska. Average annual balances over the periods 1958–72 and 1972–93 were –15 and –33cm, respectively; recent annual balances (1993–96) are about –60 cm, and the mass-balance gradient has increased. For an Arctic glacier, with its low mass-exchange rate, this marks a significant negative trend.Recently acquired elevation profiles of McCall Glacier and ten other glaciers within a 30 km radius were compared with topographic maps made in 1956 or 1973. Most of these glaciers had average annual mass balances between –25 and –33 cm, while McCall Glacier averaged –28 cm for 1956–93, indicating that it is representative of the region. In contrast, changes in terminus position for the different glaciers vary markedly. Thus, mass-balance trends in this region cannot be estimated from fractional length changes at time-scales of a few decades.We developed a simple degree-day/accumulation mass-balance model for McCall Glacier. The model was tested using precipitation and radiosonde temperatures from weather stations at Inuvik, Canada, and Barrow, Kaktovik and Fairbanks, Alaska, and was calibrated with the measured balances. The Inuvik data reproduce all measured mass balances of McCall Glacier well and also reproduce the long-term trend towards more negative balances. Data from the other stations do not produce satisfactory model results. We speculate that the Arctic Front, oriented east–west in this region, causes the differences in model results.

scholarly journals Determining the mass of the planetary candidate HD 114762 b using Gaia

2019 ◽  
Vol 632 ◽  
pp. L9 ◽  
Author(s):  
Flavien Kiefer
Keyword(s):  
Spectral Analysis ◽  
Preceding Paper ◽  
Brown Dwarfs ◽  
Excess Noise ◽  
The Sun ◽  
Minimum Mass ◽  
Brown Dwarf ◽  
Data Release ◽  
Low Mass ◽  
M Dwarf

The first planetary candidate discovered by Latham et al. (1989, Nature, 339, 38) with radial velocities around a solar-like star other than the Sun, HD 114762 b, was detected with a minimum mass of 11 MJ. The small v sin i ∼ 0 km s−1 that is otherwise measured by spectral analysis indicated that this companion of a late-F subgiant star better corresponds to a massive brown dwarf (BD) or even a low-mass M-dwarf seen nearly face-on. To our knowledge, the nature of HD 114762 b is still undetermined. The astrometric noise measured for this system in the first data release, DR1, of the Gaia mission allows us to derive new constraints on the astrometric motion of HD 114762 and on the mass of its companion. We use the method GASTON, introduced in a preceding paper, which can simulate Gaia data and determine the distribution of inclinations that are compatible with the astrometric excess noise. With an inclination of 6.26.2+1.9−1.3 degree, the mass of the companion is constrained to Mb = 108+31−26 MJ. HD 114762 b thus indeed belongs to the M-dwarf domain, down to brown dwarfs, with Mb >  13.5 MJ at the 3σ level, and is not a planet.

scholarly journals 2MASS J15460752−6258042: a mid-M dwarf hosting a prolonged accretion disc

2020 ◽  
Vol 494 (1) ◽  
pp. 62-68 ◽  
Author(s):  
Jinhee Lee ◽  
Inseok Song ◽  
Simon Murphy
Keyword(s):  
Accretion Rate ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Velocity Measurements ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Infrared Excess ◽  
Low Mass ◽  
M Dwarf ◽  
Gaia Dr2

ABSTRACT We report the discovery of the oldest (∼55 Myr) mid-M type star known to host ongoing accretion. 2MASS J15460752–6258042 (2M1546, spectral type M5, 59.2 pc) shows spectroscopic signs of accretion such as strong H α, He i, and [O i] emission lines, from which we estimate an accretion rate of ∼10−10 M⊙ yr−1. Considering the clearly detected infrared excess in all WISE bands, the shape of its spectral energy distribution (SED) and its age, we believe that the star is surrounded by a transitional disc, clearly with some gas still present at inner radii. The position and kinematics of the star from Gaia DR2 and our own radial-velocity measurements suggest membership in the nearby ∼55 Myr-old Argus moving group. At only 59 pc from Earth, 2M1546 is one of the nearest accreting mid-M dwarfs, making it an ideal target for studying the upper limit on the lifetimes of gas-rich discs around low-mass stars.

scholarly journals The SOPHIE search for northern extrasolar planets

2019 ◽  
Vol 625 ◽  
pp. A18 ◽  
Author(s):  
M. J. Hobson ◽  
X. Delfosse ◽  
N. Astudillo-Defru ◽  
I. Boisse ◽  
R. F. Díaz ◽  
...  
Keyword(s):  
Evolutionary History ◽  
Extrasolar Planets ◽  
Lower Boundary ◽  
Minimum Mass ◽  
Velocity Measurements ◽  
M Dwarfs ◽  
High Eccentricity ◽  
Solar Metallicity ◽  
History Of ◽  
M Dwarf

We present the detection of a warm Neptune orbiting the M dwarf Gl 378, using radial velocity measurements obtained with the SOPHIE spectrograph at the Observatoire de Haute-Provence. The star was observed in the context of the SOPHIE exoplanet consortium’s sub-programme dedicated to finding planets around M dwarfs. Gl 378 is an M1 star, of solar metallicity, at a distance of 14.96 pc. The single planet detected, Gl 378 b, has a minimum mass of 13.02 MEarth and an orbital period of 3.82 days, which place it at the lower boundary of the hot Neptune desert. As one of only a few such planets around M dwarfs, Gl 378 b provides important clues to the evolutionary history of these close-in planets. In particular, the eccentricity of 0.1 may point to a high-eccentricity migration. The planet may also have lost part of its envelope due to irradiation.

scholarly journals SCExAO/CHARIS Direct Imaging of A Low-mass Companion At A Saturn-like Separation from an Accelerating Young A7 Star

2021 ◽  
Vol 162 (6) ◽  
pp. 251
Author(s):  
Jeffrey Chilcote ◽  
Taylor Tobin ◽  
Thayne Currie ◽  
Timothy D. Brandt ◽  
Tyler D. Groff ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Semimajor Axis ◽  
Velocity Data ◽  
Direct Imaging ◽  
Dynamical Mass ◽  
Low Mass ◽  
M Dwarf ◽  
Radial Velocity Data

Abstract We present the SCExAO direct imaging discovery and characterization of a low-mass companion to the nearby young A7IV star, HD 91312. SCExAO/CHARIS JHK (1.1–2.4 μm) spectra and SCExAO/HiCIAO H-band imaging identify the companion over a two year baseline in a highly inclined orbit with a maximum projected separation of 8 au. The companion, HD 91312 B, induces an 8.8σ astrometric acceleration on the star as seen with the Gaia & Hipparcos satellites and a long-term radial-velocity trend as previously identified by Borgniet et al. HD 91312 B’s spectrum is consistent with that of an early-to-mid M dwarf. Hipparcos and Gaia absolute astrometry, radial-velocity data, and SCExAO/CHARIS astrometry constrain its dynamical mass to be 0.337 − 0.044 + 0.042 M ⊙, consistent with - but far more precise than - masses derived from spectroscopy, and favors a nearly edge-on orbit with a semimajor axis of ∼9.7 au. This work is an example of precisely characterizing properties of low-mass companions at solar system-like scales from a combination of direct imaging, astrometry, and radial-velocity methods.

scholarly journals The SOPHIE search for northern extrasolar planets

2018 ◽  
Vol 618 ◽  
pp. A103 ◽  
Author(s):  
M. J. Hobson ◽  
R. F. Díaz ◽  
X. Delfosse ◽  
N. Astudillo-Defru ◽  
I. Boisse ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Extrasolar Planets ◽  
Habitable Zone ◽  
Minimum Mass ◽  
Velocity Measurements ◽  
High Eccentricity ◽  
Dwarf Stars ◽  
M Stars ◽  
M Dwarf Stars ◽  
M Dwarf

We report the detection of two exoplanets and a further tentative candidate around the M-dwarf stars Gl96 and Gl617A, based on radial velocity measurements obtained with the SOPHIE spectrograph at the Observatoire de Haute-Provence. Both stars were observed in the context of the SOPHIE exoplanet consortium’s dedicated M-dwarf subprogramme, which aims to detect exoplanets around nearby M-dwarf stars through a systematic survey. For Gl96 we present the discovery of a new exoplanet at 73.9 d with a minimum mass of 19.66 earth masses. Gl96 b has an eccentricity of 0.44, placing it among the most eccentric planets orbiting M stars. For Gl617A we independently confirm a recently reported exoplanet at 86.7 d with a minimum mass of 31.29 earth masses. Both Gl96 b and Gl617A b are potentially within the habitable zone, although the high eccentricity of Gl96 b may take it too close to the star at periapsis.

scholarly journals The mass balance of McCall Glacier, Brooks Range, Alaska, U.S.A.; its regional relevance and implications for climate change in the Arctic

1998 ◽  
Vol 44 (147) ◽  
pp. 333-351 ◽  
Author(s):  
B.T. Rabus ◽  
K. A. Echelmeyer
Keyword(s):  
Mass Balance ◽  
The Arctic ◽  
Balance Model ◽  
Mass Balances ◽  
Arctic Alaska ◽  
Low Mass ◽  
Length Changes ◽  
Arctic Glacier ◽  
Long Term Trend

AbstractMcCall Glacier has the only long-term mass-balance record in Arctic-Alaska. Average annual balances over the periods 1958–72 and 1972–93 were –15 and –33cm, respectively; recent annual balances (1993–96) are about –60 cm, and the mass-balance gradient has increased. For an Arctic glacier, with its low mass-exchange rate, this marks a significant negative trend.Recently acquired elevation profiles of McCall Glacier and ten other glaciers within a 30 km radius were compared with topographic maps made in 1956 or 1973. Most of these glaciers had average annual mass balances between –25 and –33 cm, while McCall Glacier averaged –28 cm for 1956–93, indicating that it is representative of the region. In contrast, changes in terminus position for the different glaciers vary markedly. Thus, mass-balance trends in this region cannot be estimated from fractional length changes at time-scales of a few decades.We developed a simple degree-day/accumulation mass-balance model for McCall Glacier. The model was tested using precipitation and radiosonde temperatures from weather stations at Inuvik, Canada, and Barrow, Kaktovik and Fairbanks, Alaska, and was calibrated with the measured balances. The Inuvik data reproduce all measured mass balances of McCall Glacier well and also reproduce the long-term trend towards more negative balances. Data from the other stations do not produce satisfactory model results. We speculate that the Arctic Front, oriented east–west in this region, causes the differences in model results.

scholarly journals The BEBOP radial-velocity survey for circumbinary planets

2019 ◽  
Vol 624 ◽  
pp. A68 ◽  
Author(s):  
David V. Martin ◽  
Amaury H. M. J. Triaud ◽  
Stéphane Udry ◽  
Maxime Marmier ◽  
Pierre F. L. Maxted ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Eclipsing Binaries ◽  
Velocity Measurements ◽  
Planetary Mass ◽  
Low Mass ◽  
Initial Survey ◽  
M Dwarf ◽  
Circumbinary Planets

We introduce the BEBOP radial velocity survey for circumbinary planets. We initiated this survey using the CORALIE spectrograph on the Swiss Euler Telescope at La Silla, Chile. An intensive four-year observation campaign commenced in 2013, targeting 47 single-lined eclipsing binaries drawn from the EBLM survey for low mass eclipsing binaries. Our specific use of binaries with faint M dwarf companions avoids spectral contamination, providing observing conditions akin to single stars. By combining new BEBOP observations with existing ones from the EBLM programme, we report on the results of 1519 radial velocity measurements over timespans as long as eight years. For the best targets we are sensitive to planets down to 0.1 MJup, and our median sensitivity is 0.4 MJup. In this initial survey we do not detect any planetary mass companions. Nonetheless, we present the first constraints on the abundance of circumbinary companions, as a function of mass and period. A comparison of our results to Kepler’s detections indicates a dispersion of planetary orbital inclinations less than ~10°.

NAEP Trends: Main NAEP vs. Long-Term Trend

2010 ◽  
Author(s):  
Albert E. Beaton ◽  
James R. Chromy
Keyword(s):  
Term Trend ◽  
Long Term Trend
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