scholarly journals Transiting Planets in the Galactic Bulge from SWEEPS Survey and Implications

2008 ◽  
Vol 4 (S253) ◽  
pp. 45-53 ◽  
Author(s):  
Kailash C. Sahu ◽  
Stefano Casertano ◽  
Jeff Valenti ◽  
Howard E. Bond ◽  
Thomas M. Brown ◽  
...  
Keyword(s):  
Extrasolar Planets ◽  
Hubble Space Telescope ◽  
Monitoring Program ◽  
Solar Neighborhood ◽  
Galactic Bulge ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Transiting Planets ◽  
Short Period ◽  
Low Mass

AbstractThe SWEEPS (Sagittarius Window Eclipsing Extrasolar Planet Search) program was aimed at detecting planets around stars in the Galactic bulge, not only to determine their physical properties, but also to determine whether the properties of planets found in the solar neighborhood, such as their frequency and the metallicity dependence, also hold for the planets in the Galactic bulge. We used the Hubble Space Telescope to monitor 180,000 F, G, K, and M dwarfs in the Galactic bulge continuously for 7 days in order to look for transiting planets. We discovered 16 candidate transiting extrasolar planets with periods of 0.6 to 4.2 days, including a possible new class of ultra-short period planets (USPPs) with P < 1 day. The facts that (i) the coverage in the monitoring program is continuous, (ii) most of the stars are at a known distance (in the Galctic bulge), (iii) monitoring was carried out in 2 passbands, and (iv) the images have high spatial resolution, were crucial in minimizing and estimating the false positive rates. We estimate that at least 45% of the candidates are genuine planets. Radial velocity observations of the two brightest host stars further support the planetary nature of the transiting companions. These results suggest that the planet frequency in the Galactic bulge is similar to that in the solar neighborhood. They also suggest that higher metallicity favors planet formation even in the Galactic bulge. The USPPs occur only around low-mass stars which may suggest that close-in planets around higher-mass stars are irradiately evaporated, or that planets are able to migrate to and survive in close-in orbits only around such old and low-mass stars.

scholarly journals The CARMENES search for exoplanets around M dwarfs

2018 ◽  
Vol 620 ◽  
pp. A171 ◽  
Author(s):  
R. Luque ◽  
G. Nowak ◽  
E. Pallé ◽  
D. Kossakowski ◽  
T. Trifonov ◽  
...  
Keyword(s):  
Bimodal Distribution ◽  
Photometric Data ◽  
M Dwarfs ◽  
Visual Channel ◽  
Low Mass Stars ◽  
Short Period ◽  
Low Mass ◽  
Periodic Signals ◽  
M Stars ◽  
Host Stars

We announce the discovery of two planetary companions orbiting around the low-mass stars Ross 1020 (GJ 3779, M4.0V) and LP 819-052 (GJ 1265, M4.5V). The discovery is based on the analysis of CARMENES radial velocity (RV) observations in the visual channel as part of its survey for exoplanets around M dwarfs. In the case of GJ 1265, CARMENES observations were complemented with publicly available Doppler measurements from HARPS. The datasets reveal two planetary companions, one for each star, that share very similar properties: minimum masses of 8.0 ± 0.5 M⊕ and 7.4 ± 0.5 M⊕ in low-eccentricity orbits with periods of 3.023 ± 0.001 d and 3.651 ± 0.001 d for GJ 3779 b and GJ 1265 b, respectively. The periodic signals around 3 d found in the RV data have no counterpart in any spectral activity indicator. Furthermore, we collected available photometric data for the two host stars, which confirm that the additional Doppler variations found at periods of approximately 95 d can be attributed to the rotation of the stars. The addition of these planets to a mass-period diagram of known planets around M dwarfs suggests a bimodal distribution with a lack of short-period low-mass planets in the range of 2–5 M⊕. It also indicates that super-Earths (>5 M⊕) currently detected by RV and transit techniques around M stars are usually found in systems dominated by a single planet.

scholarly journals Magnetic activity in the HARPS M dwarf sample

2017 ◽  
Vol 600 ◽  
pp. A13 ◽  
Author(s):  
N. Astudillo-Defru ◽  
X. Delfosse ◽  
X. Bonfils ◽  
T. Forveille ◽  
C. Lovis ◽  
...  
Keyword(s):  
Monitoring Program ◽  
Rotation Period ◽  
Magnetic Activity ◽  
Spectral Lines ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
The Galaxy ◽  
Low Mass ◽  
M Dwarf ◽  
The Relationship

Context. Atmospheric magnetic fields in stars with convective envelopes heat stellar chromospheres, and thus increase the observed flux in the Ca ii H and K doublet. Starting with the historical Mount Wilson monitoring program, these two spectral lines have been widely used to trace stellar magnetic activity, and as a proxy for rotation period (Prot) and consequently for stellar age. Monitoring stellar activity has also become essential in filtering out false-positives due to magnetic activity in extra-solar planet surveys. The Ca ii emission is traditionally quantified through the R'HK-index, which compares the chromospheric flux in the doublet to the overall bolometric flux of the star. Much work has been done to characterize this index for FGK-dwarfs, but M dwarfs – the most numerous stars of the Galaxy – were left out of these analyses and no calibration of their Ca ii H and K emission to an R'HK exists to date. Aims. We set out to characterize the magnetic activity of the low- and very-low-mass stars by providing a calibration of the R'HK-index that extends to the realm of M dwarfs, and by evaluating the relationship between R'HK and the rotation period. Methods. We calibrated the bolometric and photospheric factors for M dwarfs to properly transform the S-index (which compares the flux in the Ca ii H and K lines to a close spectral continuum) into the R'HK. We monitored magnetic activity through the Ca ii H and K emission lines in the HARPS M dwarf sample. Results. The R'HK index, like the fractional X-ray luminosity LX/Lbol, shows a saturated correlation with rotation, with saturation setting in around a ten days rotation period. Above that period, slower rotators show weaker Ca ii activity, as expected. Under that period, the R'HK index saturates to approximately 10-4. Stellar mass modulates the Ca ii activity, with R'HK showing a constant basal activity above 0.6 M⊙ and then decreasing with mass between 0.6 M⊙ and the fully-convective limit of 0.35 M⊙. Short-term variability of the activity correlates with its mean level and stars with higher R'HK indexes show larger R'HK variability, as previously observed for earlier spectral types.

scholarly journals Doppler Detection of Extrasolar Planets

1999 ◽  
Vol 170 ◽  
pp. 121-130
Author(s):  
G. W. Marcy ◽  
R. Paul Butler ◽  
D. A. Fischer
Keyword(s):  
Main Sequence ◽  
Extrasolar Planets ◽  
Mass Function ◽  
Solar Neighborhood ◽  
Main Sequence Stars ◽  
Low Mass Stars ◽  
Pile Up ◽  
Solar Type ◽  
Low Mass ◽  
M Dwarf

AbstractWe have measured the radial velocities of 540 G and K main sequence stars with a precision of 3−10 ms−1 using the Lick and Keck échelle spectrometers. We had detected 6 companions that have m sin i < 7 MJup. We announce here the discovery of a new planet around Gliese 876, found in our Doppler measurements from both Lick and Keck. This is the first planet found around an M dwarf, which indicates that planets occur around low-mass stars, in addition to solar-type stars. We combine our entire stellar sample with that of Mayor et al. to derive general properties of giant planets within a few AU of these stars. Less than 1% of G and K main sequence stars harbor brown dwarf companions with masses between 5 and 70 MJup. Including Gliese 876b, 8 companions exhibit m sin i < 5 MJup which constitute the best planet candidates to date. Apparently, 4% of stars have planetary companions within the range m sin i = 0.5 to 5 MJup. Planets are distinguished from brown dwarfs by the discontinuous jump in the mass function at 5 MJup. About 2/3 of the planets orbit within just 0.3 AU due in part to their favorable detectability, but also possibly due to a real “pile up” of planets near the star. Inward orbital migration after formation may explain this, but the mechanism to stop the migration remains unclear. Five of eight planets have orbital eccentricities greater than that of our Jupiter, eJup = 0.048, and tidal circularization may explain most of the circular orbits. Thus, eccentric orbits are common and may arise from gravitational interactions with other planets, stars, or the protoplanetary disk. The planet-bearing stars are systematically metal-rich, as is the Sun, compared to the solar neighborhood.

scholarly journals Multiple Sequences of M-dwarfs in NGC 2808 and ω Centauri.

2012 ◽  
Vol 10 (H16) ◽  
pp. 241-242
Author(s):  
A. P. Milone
Keyword(s):  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Wide Field ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Space Telescope ◽  
Low Mass ◽  
Multiple Sequences ◽  
Infrared Channel

AbstractThe infrared channel of the Wide-Field Camera 3 on the Hubble Space Telescope revealed multiple main sequences of very low-mass stars in the globular clusters NGC 2808 and ω Cen. In this paper I summarize the observational facts and provide a possible interpretation.

scholarly journals Hα ACTIVITY OF OLD M DWARFS: STELLAR CYCLES AND MEAN ACTIVITY LEVELS FOR 93 LOW-MASS STARS IN THE SOLAR NEIGHBORHOOD

2013 ◽  
Vol 764 (1) ◽  
pp. 3 ◽  
Author(s):  
Paul Robertson ◽  
Michael Endl ◽  
William D. Cochran ◽  
Sarah E. Dodson-Robinson
Keyword(s):  
Solar Neighborhood ◽  
Activity Levels ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Low Mass

scholarly journals On the mass distribution of stars in the solar neighborhood

2006 ◽  
pp. 17-20 ◽  
Author(s):  
S. Ninkovic ◽  
V. Trajkovska
Keyword(s):  
Mass Distribution ◽  
Main Sequence ◽  
Solar Neighborhood ◽  
The Sun ◽  
Main Sequence Stars ◽  
M Dwarfs ◽  
Solar Mass ◽  
Low Mass Stars ◽  
Low Mass ◽  
The Mean

The present authors analyze samples consisting of Hipparcos stars. Based on the corresponding HR diagrams they estimate masses of Main-Sequence stars from their visual magnitudes. They find that already beyond the heliocentric radius of 10 pc the effects of observational selection against K and M dwarfs become rather strong. For this reason the authors are inclined to think that the results concerning this heliocentric sphere appear as realistic, i. e. the fraction of low-mass stars (under half solar mass) is about 50% and, as a consequence, the mean star mass should be about 0.6 solar masses and Agekyan's factor about 1.2. That stars with masses higher than 5 M? are very rare is confirmed also from the data concerning more remote stars. It seems that white dwarfs near the Sun are not too frequent so that their presence cannot affect the main results of the present work significantly.

scholarly journals Giant planets around AF and M stars

2013 ◽  
Vol 8 (S299) ◽  
pp. 64-65
Author(s):  
Julien Rameau ◽  
Gaël Chauvin ◽  
Anne-Marie Lagrange ◽  
Philippe Delorme ◽  
Justine Lannier
Keyword(s):  
Giant Planets ◽  
Early Type ◽  
Late Type ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Planetary Mass ◽  
Nearby Stars ◽  
Low Mass ◽  
M Stars ◽  
The One

AbstractWe present the results of two three-year surveys of young and nearby stars to search for wide orbit giant planets. On the one hand, we focus on early-type and massive, namely β Pictoris analogs. On the other hand, we observe late type and very low mass stars, i.e., M dwarfs. We report individual detections of new planetary mass objects. According to our deep detection performances, we derive the observed frequency of giant planets between these two classes of parent stars. We find frequency between 6 to 12% but we are not able to assess a/no correlation with the host-mass.

scholarly journals Atmospheres From Very Low-Mass Stars to Extrasolar Planets

2012 ◽  
Vol 57 ◽  
pp. 3-43 ◽  
Author(s):  
F. Allard ◽  
D. Homeier ◽  
B. Freytag ◽  
C.M. Sharp
Keyword(s):  
Extrasolar Planets ◽  
Low Mass Stars ◽  
Low Mass

scholarly journals Multi-Wavelength High-Resolution Spectroscopy for Exoplanet Detection: Motivation, Instrumentation and First Results

Geosciences ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 289 ◽  
Author(s):  
Serena Benatti
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Giant Planet ◽  
High Resolution Spectroscopy ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
First Results ◽  
Multi Wavelength ◽  
Low Mass ◽  
Rocky Planets

Exoplanet research has shown an incessant growth since the first claim of a hot giant planet around a solar-like star in the mid-1990s. Today, the new facilities are working to spot the first habitable rocky planets around low-mass stars as a forerunner for the detection of the long-awaited Sun-Earth analog system. All the achievements in this field would not have been possible without the constant development of the technology and of new methods to detect more and more challenging planets. After the consolidation of a top-level instrumentation for high-resolution spectroscopy in the visible wavelength range, a huge effort is now dedicated to reaching the same precision and accuracy in the near-infrared. Actually, observations in this range present several advantages in the search for exoplanets around M dwarfs, known to be the most favorable targets to detect possible habitable planets. They are also characterized by intense stellar activity, which hampers planet detection, but its impact on the radial velocity modulation is mitigated in the infrared. Simultaneous observations in the visible and near-infrared ranges appear to be an even more powerful technique since they provide combined and complementary information, also useful for many other exoplanetary science cases.

scholarly journals Characterization of rocky exoplanets from their infrared phase curve

2010 ◽  
Vol 6 (S276) ◽  
pp. 485-486
Author(s):  
Anne-Sophie Maurin ◽  
Franck Selsis ◽  
Franck Hersant ◽  
Marco Delbò
Keyword(s):  
Thermal Emission ◽  
Infrared Emission ◽  
Phase Curve ◽  
Low Mass Stars ◽  
Rotation Surface ◽  
Key Population ◽  
Short Period ◽  
Low Mass ◽  
Observation Geometry

AbstractDuring the last few years, observations have yielded an abundant population of short-period planets under 15 Earth masses. Among those, hot terrestrial exoplanets represent a key population to study the survival of dense atmospheres close to their parent star. Thermal emission from exoplanets orbiting low-mass stars will be observable with the next generation of infrared telescopes, in particular the JWST. In order to constrain planetary and atmospheric properties, we have developed models to simulate the variation of the infrared emission along the path of the orbit (IR phase curve) for both airless planets and planets with dense atmospheres. Here, we focus on airless planets and present preliminary results on the influence of orbital elements, planet rotation, surface properties and observation geometry. Then, using simulated noisy phase curves, we test the retrieval of planets' properties and identify the degeneracies.

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