A temperate exo-Earth around a quiet M dwarf at 3.4 parsec

The combination of high-contrast imaging and high-dispersion spectroscopy, which has successfully been use to detect the atmosphere of a giant planet, is one of the most promising potential probes of the atmosphere of Earth-size worlds. The forthcoming generation of extremely large telescopes (ELTs) may obtain sufficient contrast with this technique to detect O2 in the atmosphere of those worlds that orbit low-mass M dwarfs. This is strong motivation to carry out a census of planets around cool stars for which habitable zones can be resolved by ELTs, i.e. for M dwarfs within ~5 parsec. Our HARPS survey has been a major contributor to that sample of nearby planets. Here we report on our radial velocity observations of Ross 128 (Proxima Virginis, GJ447, HIP 57548), an M4 dwarf just 3.4 parsec away from our Sun. This source hosts an exo-Earth with a projected mass m sini = 1.35 M⊕ and an orbital period of 9.9 days. Ross 128 b receives less than 1.5 times as much flux as Earth from the Sun and its equilibrium ranges in temperature between 269 K for an Earth-like albedo and 213 K for a Venus-like albedo. Recent studies place it close to the inner edge of the conventional habitable zone. An 80-day long light curve from K2 campaign C01 demonstrates that Ross 128 b does not transit. Together with the All Sky Automated Survey (ASAS) photometry and spectroscopic activity indices, the K2 photometry shows that Ross 128 rotates slowly and has weak magnetic activity. In a habitability context, this makes survival of its atmosphere against erosion more likely. Ross 128 b is the second closest known exo-Earth, after Proxima Centauri b (1.3 parsec), and the closest temperate planet known around a quiet star. The 15 mas planet-star angular separation at maximum elongation will be resolved by ELTs (>3λ∕D) in the optical bands of O2.

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The SOPHIE search for northern extrasolar planets

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935019 ◽

2019 ◽

Vol 625 ◽

pp. A17 ◽

Cited By ~ 3

Author(s):

R. F. Díaz ◽

X. Delfosse ◽

M. J. Hobson ◽

I. Boisse ◽

N. Astudillo-Defru ◽

...

Keyword(s):

Extrasolar Planets ◽

Equilibrium Temperature ◽

Current Data ◽

Velocity Variation ◽

High Dispersion ◽

Correlated Noise ◽

Contrast Imaging ◽

High Contrast Imaging ◽

Independent Analysis ◽

Low Mass

Periodic radial velocity variations in the nearby M-dwarf star Gl 411 are reported, based on measurements with the SOPHIE spectrograph. Current data do not allow us to distinguish between a 12.95-day period and its one-day alias at 1.08 days, but favour the former slightly. The velocity variation has an amplitude of 1.6 m s−1, making this the lowest-amplitude signal detected with SOPHIE up to now. We have performed a detailed analysis of the significance of the signal and its origin, including extensive simulations with both uncorrelated and correlated noise, representing the signal induced by stellar activity. The signal is significantly detected, and the results from all tests point to its planetary origin. Additionally, the presence of an additional acceleration in the velocity time series is suggested by the current data. On the other hand, a previously reported signal with a period of 9.9 days, detected in HIRES velocities of this star, is not recovered in the SOPHIE data. An independent analysis of the HIRES dataset also fails to unveil the 9.9-day signal. If the 12.95-day period is the real one, the amplitude of the signal detected with SOPHIE implies the presence of a planet, called Gl 411 b, with a minimum mass of around three Earth masses, orbiting its star at a distance of 0.079 AU. The planet receives about 3.5 times the insolation received by Earth, which implies an equilibrium temperature between 256 and 350 K, and makes it too hot to be in the habitable zone. At a distance of only 2.5 pc, Gl 411 b, is the third closest low-mass planet detected to date. Its proximity to Earth will permit probing its atmosphere with a combination of high-contrast imaging and high-dispersion spectroscopy in the next decade.

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High-fidelity photometry and astrometry of high-contrast imaged companions using LOCI processing.

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313007795 ◽

2013 ◽

Vol 8 (S299) ◽

pp. 44-45

Author(s):

Jérôme Maire ◽

Jonathan Gagné ◽

David Lafrenière ◽

James R. Graham ◽

René Doyon

Keyword(s):

Contrast Ratio ◽

Angular Separation ◽

Speckle Noise ◽

High Contrast ◽

Contrast Imaging ◽

High Contrast Imaging ◽

Suppression Technique ◽

Imaging And Spectroscopy ◽

And Migration ◽

Imaging Performance

RésuméDirect imaging and spectroscopy of exoplanets is a key element for understanding planet formation and migration. Such direct detections and characterizations remains technologically challenging, since a very high contrast ratio and small angular separation are involved, and futhermore speckle noise limits the high-contrast imaging performance. We further discuss a speckle subtraction and suppression technique that fully takes advantage of spectral and time-domain information on quasi-static speckles to measure the highest-fidelity photometry as well as accurate astrometry of detected companions.

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

Geosciences ◽

10.3390/geosciences8080289 ◽

2018 ◽

Vol 8 (8) ◽

pp. 289 ◽

Cited By ~ 1

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.

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The likelihood of detecting young giant planets with high-contrast imaging and interferometry

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2600 ◽

2019 ◽

Vol 490 (1) ◽

pp. 502-512 ◽

Cited By ~ 1

Author(s):

A L Wallace ◽

M J Ireland

Keyword(s):

Radial Velocity ◽

Near Infrared ◽

Giant Planet ◽

Giant Planets ◽

Contrast Imaging ◽

Distribution Models ◽

High Contrast Imaging ◽

Solar Type ◽

Infrared Wavelengths ◽

Core Accretion

ABSTRACT Giant planets are expected to form at orbital radii that are relatively large compared to transit and radial velocity detections (>1 au). As a result, giant planet formation is best observed through direct imaging. By simulating the formation of giant (0.3–5MJ) planets by core accretion, we predict planet magnitude in the near-infrared (2–4 μm) and demonstrate that, once a planet reaches the runaway accretion phase, it is self-luminous and is bright enough to be detected in near-infrared wavelengths. Using planet distribution models consistent with existing radial velocity and imaging constraints, we simulate a large sample of systems with the same stellar and disc properties to determine how many planets can be detected. We find that current large (8–10 m) telescopes have at most a 0.2 per cent chance of detecting a core-accretion giant planet in the L’ band and 2 per cent in the K band for a typical solar-type star. Future instruments such as METIS and VIKiNG have higher sensitivity and are expected to detect exoplanets at a maximum rate of 2 and 8 per cent, respectively.

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Magnetic activity in the HARPS M dwarf sample

Astronomy and Astrophysics ◽

10.1051/0004-6361/201527078 ◽

2017 ◽

Vol 600 ◽

pp. A13 ◽

Cited By ~ 59

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.

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Do Low Luminosity Stars Matter?

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310008185 ◽

2009 ◽

Vol 5 (H15) ◽

pp. 47-60

Author(s):

María Teresa Ruiz

Keyword(s):

White Dwarf ◽

Galactic Plane ◽

M Dwarfs ◽

Low Mass Stars ◽

Missing Mass ◽

Low Mass ◽

Astronomical Research ◽

Red Giant ◽

Large Telescopes ◽

The Universe

AbstractHistorically, low luminosity stars have attracted very little attention, in part because they are difficult to see except with large telescopes, however, by neglecting to study them we are leaving out the vast majority of stars in the Universe. Low mass stars evolve very slowly, it takes them trillions of years to burn their hydrogen, after which, they just turn into a He white dwarf, without ever going through the red giant phase. This lack of observable evolution partly explains the lack of interest in them. The search for the “missing mass” in the galactic plane turned things around and during the 60s and 70s the search for large M/L objects placed M-dwarfs and cool WDs among objects of astrophysical interest. New fields of astronomical research, like BDs and exoplanets appeared as spin-offs from efforts to find the “missing mass”. The search for halo white dwarfs, believed to be responsible for the observed microlensing events, is pursued by several groups. The progress in these last few years has been tremendous, here I present highlights some of the great successes in the field and point to some of the still unsolved issues.

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SPHERE+, Imaging young planets down to the snow line

10.5194/epsc2021-24 ◽

2021 ◽

Author(s):

Anthony Boccaletti ◽

Keyword(s):

Adaptive Optics ◽

Near Infrared ◽

Imaging Spectroscopy ◽

Giant Planet ◽

High Spectral Resolution ◽

Contrast Imaging ◽

High Contrast Imaging ◽

Orbital Periods ◽

Complementary Techniques ◽

Technical Solutions

SPHERE, the high contrast imaging facility at the VLT has contributed significantly to the exploration of planetary systems, by revealing many details in proto-planetary and debris disks, by measuring the atmospheric properties of young giant planets and by deriving constraints on the giant planet population in long orbital periods. Such achievements allow us to provide a better understanding of planetary formation and evolution. The versatility of SPHERE also enables various secondary and sometimes unexpected science cases owing to a large spectral coverage from the visible to the near IR, and the availability of several observing modes as imaging, spectroscopy and polarimetry. Yet the access to the region where planets are expected to form, is not complete and still represents a challenge. To overcome this limitation larger contrasts at shorter separations are definitely required.&#160; The SPHERE+ concept precisely aims to provide the capabilities to primarily access the bulk of the young giant planet population down to the snowline&#160; in order to bridge the gap with complementary techniques. As a second objective, SPHERE+ should be able to observe an increased sample of targets, fainter and redder than those observed in the first survey. Finally, SPHERE+ will provide a higher level of characterization of planet&#8217;s atmospheres. To achieve these goals, SPHERE should be upgraded with a faster Adaptive Optics system to reach&#160; high contrasts at closer angular separations, together with a more sensitive wavefront sensor in the infrared to observe redder targets. Medium and high spectral resolution in the near infrared will be brought by a dedicated IFU spectrograph or taking advantage of the HiRISE project to combined SPHERE and CRIRES+. We will present the science cases and the technical solutions that are foreseen to reach the appropriate performances, and provide potential ways for such an upgrade. &#160;

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Comparison of coronagraphs for high-contrast imaging in the context of extremely large telescopes

Astronomy and Astrophysics ◽

10.1051/0004-6361:200810650 ◽

2008 ◽

Vol 492 (1) ◽

pp. 289-300 ◽

Cited By ~ 18

Author(s):

P. Martinez ◽

A. Boccaletti ◽

M. Kasper ◽

C. Cavarroc ◽

N. Yaitskova ◽

...

Keyword(s):

High Contrast ◽

Contrast Imaging ◽

High Contrast Imaging ◽

Large Telescopes

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A HARPS RV search for planets around young nearby stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936038 ◽

2020 ◽

Vol 633 ◽

pp. A44 ◽

Cited By ~ 3

Author(s):

A. Grandjean ◽

A.-M. Lagrange ◽

M. Keppler ◽

N. Meunier ◽

L. Mignon ◽

...

Keyword(s):

Time Series ◽

Radial Velocity ◽

Spectroscopic Data ◽

Imaging Techniques ◽

Giant Planet ◽

Magnetic Activity ◽

Young Stars ◽

Upper Limits ◽

Nearby Stars ◽

Low Mass

Context. Young nearby stars are good candidates in the search for planets with both radial velocity (RV) and direct imaging techniques. This, in turn, allows for the computation of the giant planet occurrence rates at all separations. The RV search around young stars is a challenge as they are generally faster rotators than older stars of similar spectral types and they exhibit signatures of magnetic activity (spots) or pulsation in their RV time series. Specific analyses are necessary to characterize, and possibly correct for, this activity. Aims. Our aim is to search for planets around young nearby stars and to estimate the giant planet (GP) occurrence rates for periods up to 1000 days. Methods. We used the HARPS spectrograph on the 3.6 m telescope at La Silla Observatory to observe 89 A−M young (<600 Myr) stars. We used our SAFIR (Spectroscopic data via Analysis of the Fourier Interspectrum Radial velocities) software to compute the RV and other spectroscopic observables. Then, we computed the companion occurrence rates on this sample. Results. We confirm the binary nature of HD 177171, HD 181321 and HD 186704. We report the detection of a close low mass stellar companion for HIP 36985. No planetary companion was detected. We obtain upper limits on the GP (<13 MJup) and BD (∈ [13;80] MJup) occurrence rates based on 83 young stars for periods less than 1000 days, which are set, 2−2+3 and 1−1+3%.

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Precision Radial Velocities in the Near Infrared with TEDI

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308026355 ◽

2008 ◽

Vol 4 (S253) ◽

pp. 157-161 ◽

Cited By ~ 1

Author(s):

James P. Lloyd ◽

Agnieszka Czeszumska ◽

Jerry Edelstein ◽

David Erskine ◽

Michael Feuerstein ◽

...

Keyword(s):

Radial Velocity ◽

Near Infrared ◽

Radial Velocities ◽

Velocity Measurements ◽

M Dwarfs ◽

Low Mass Stars ◽

Habitable Zones ◽

Low Mass ◽

Transit Method

AbstractThe TEDI (TripleSpec - Exoplanet Discovery Instrument) is a dedicated instrument for the near-infrared radial velocity search for planetary companions to low-mass stars with the goal of achieving meters-per-second radial velocity precision. Heretofore, such planet searches have been limited almost entirely to the optical band and to stars that are bright in this band. Consequently, knowledge about planetary companions to the populous but visibly faint low-mass stars is limited. In addition to the opportunity afforded by precision radial velocity searches directly for planets around low mass stars, transits around the smallest M dwarfs offer a chance to detect the smallest possible planets in the habitable zones of the parent stars. As has been the the case with followup of planet candidates detected by the transit method requiring radial velocity confirmation, the capability to undertake efficient precision radial velocity measurements of mid-late M dwarfs will be required. TEDI has been commissioned on the Palomar 200” telescope in December 2007, and is currently in a science verification phase.

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