<i>Hubble Space Telescope</i>Search for M Subdwarf Binaries

Riaz, B.; Gizis, John E.; Samaddar, Debasmita

doi:10.1086/523931

Cited by 27 publications

(41 citation statements)

References 37 publications

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“…The binary rate from the combined samples of Gizis & Reid (2000), Lépine et al (2007), Riaz et al (2008), and Dahn et al (2008), which had no stars in common, is only 6% (3/49). Gelino's work yields a higher binary rate of 13%, but the sample is a mixture of G-, K-and M-type subdwarfs, so the results are not immediately comparable to the other surveys.…”

Section: Multiplicity Comparison With Similar Surveysmentioning

confidence: 99%

“…for LHS 169 indicates a large V r variation observed in Dawson & De Robertis (2005), and this system needs to be re-observed. "A" and "W" in Column 8 indicates targets have also been observed by HST/ACS and HST/WFPC2 in Riaz et al (2008) and Gizis & Reid (2000). a Observed with a wider filter (Johnson V: 545 ± 85 nm) and a lower microscope objective due to the character of target.…”

Section: Observations and Calibrations Of Speckle Interferometrymentioning

confidence: 99%

“…In Table 1, Columns 1-3 are coordinates and star identifiers, Column 4 indicates the observing run (run epochs are given in the table notes), and Columns 5-9 give details of multiplicity. Seven targets have also been observed by Gizis & Reid (2000) using the Hubble Space Telescope (HST)/ Wide-Field Planetary Camera 2 (WFPC2) and by Riaz et al (2008) using the HST/Advanced Camera for Surveys (ACS); these are noted as "W" = WFPC2 or "A" = ACS in Column 9 for the HST instruments used to make the observations.…”

Section: Observations and Calibrations Of Speckle Interferometrymentioning

confidence: 99%

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Cool Subdwarf Investigations. Ii. Multiplicity

Jao

Mason

Hartkopf

et al. 2009

The Astronomical Journal

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Cool subdwarfs of types K and M are the fainter counterparts of cool main-sequence dwarfs that dominate the Galactic population. In this paper, we present the results of an optical speckle survey of 62 confirmed cool subdwarf systems within 60 pc. We have resolved two new companions and confirmed two previously known companions with separations 0. 13-3. 29. After including previously known wide companions and all known spectroscopic binaries, we determine the multiplicity rate of cool subdwarfs to be 26% ± 6%, which is somewhat lower than comparable main-sequence stars that have a multiplicity rate of 37% ± 5%. We find that only 3% of the cool subdwarfs surveyed have companions within 10 AU, 3% have companions between 10 and 100 AU, and 14% have companions beyond 100 AU. The other 6% of cool subdwarfs are spectroscopic binaries. This is very different from K/M dwarfs that have most companions (13%) at separations closer than 10 AU. However, because a search for close binaries among a large sample of nearby cool subdwarfs remains elusive, it is not yet settled whether or not the multiplicity rates are significantly different. Nonetheless, several different observational results and theories pointing to a possible dearth of subdwarf multiples are discussed.

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Section: Multiplicity Comparison With Similar Surveysmentioning

confidence: 99%

Section: Observations and Calibrations Of Speckle Interferometrymentioning

confidence: 99%

Section: Observations and Calibrations Of Speckle Interferometrymentioning

confidence: 99%

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Cool Subdwarf Investigations. Ii. Multiplicity

Jao

Mason

Hartkopf

et al. 2009

The Astronomical Journal

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“…In addition, J12025+084 (M1.5 V; ζ = 0.898 -LHS 320) was classified by Gizis (1997) as an sdM2.0 star and was investigated extensively afterwards with high-resolution imagers (Gizis & Reid 2000;Riaz et al 2008;Jao et al 2009;Lodieu et al 2009). However, we failed to detect any subdwarf signpost in our high signal-to-noise spectrum, which is partly consistent with the metallicity [Fe/H] = −0.6±0.3 measured by Rajpurohit et al (2014).…”

Section: Metallicitymentioning

confidence: 99%

CARMENES input catalogue of M dwarfs

Alonso-Floriano¹,

Morales²,

Caballero³

et al. 2015

A&A

195

178

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Context. CARMENES is a stabilised, high-resolution, double-channel spectrograph at the 3.5 m Calar Alto telescope. It is optimally designed for radial-velocity surveys of M dwarfs with potentially habitable Earth-mass planets. Aims. We prepare a list of the brightest, single M dwarfs in each spectral subtype observable from the northern hemisphere, from which we will select the best planet-hunting targets for CARMENES. Methods. In this first paper on the preparation of our input catalogue, we compiled a large amount of public data and collected lowresolution optical spectroscopy with CAFOS at the 2.2 m Calar Alto telescope for 753 stars. We derived accurate spectral types using a dense grid of standard stars, a double least-squares minimisation technique, and 31 spectral indices previously defined by other authors. Additionally, we quantified surface gravity, metallicity, and chromospheric activity for all the stars in our sample. Results. We calculated spectral types for all 753 stars, of which 305 are new and 448 are revised. We measured pseudo-equivalent widths of Hα for all the stars in our sample, concluded that chromospheric activity does not affect spectral typing from our indices, and tabulated 49 stars that had been reported to be young stars in open clusters, moving groups, and stellar associations. Of the 753 stars, two are new subdwarf candidates, three are T Tauri stars, 25 are giants, 44 are K dwarfs, and 679 are M dwarfs. Many of the 261 investigated dwarfs in the range M4.0-8.0 V are among the brightest stars known in their spectral subtype. Conclusions. This collection of low-resolution spectroscopic data serves as a candidate target list for the CARMENES survey and can be highly valuable for other radial-velocity surveys of M dwarfs and for studies of cool dwarfs in the solar neighbourhood.

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“…In the M dwarf regime, the sample imaged at high resolution is much smaller. Riaz et al (2008) expanded the Hubble Space Telescope (HST) high-resolution imaging by Gizis & Reid (2000) and derived an upper limit on the binary frequency of 7% (3.6 ± 3.6%; 1σ limit) from a sample of 28 M subdwarfs. An independant sample of Article published by EDP Sciences 18 sdM were observed with the Lick adaptive optics Laser Guide Star system by Lépine et al (2007b) and one sdK7.5, LHS 1589, was resolved into a close binary system, yielding a binary fraction of 5.6 ± 5.6%.…”

Section: Introductionmentioning

confidence: 99%

Lucky Imaging of M subdwarfs

Lodieu

Osorio

Martín

2009

A&A

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Context. The knowledge of the binary properties of metal-poor and solar-metallicity stars can shed light on the potential differences between the formation processes responsible for both types of objects. Aims. The aim of the project is to determine the binary properties (separation, mass ratio, frequency of companions) for M subdwarfs, the low-metallicity counterparts of field M dwarfs, and investigate any potential differences between both populations. Methods. We have obtained high-resolution imaging in the optical for a sample of 24 early-M subdwarfs and nine extreme subdwarfs with the "Lucky Imaging" technique using the AstraLux instrument on the Calar Alto 2.2-m telescope. Results. We are sensitive to companions at separations larger than 0.1 arcsec and differences of ∼2 mag at 0.1 arcsec and ∼5 mag at 1 arcsec. We have found no companion around the 24 subdwarfs under study and one close binary out of nine extreme subdwarfs. A second image of LHS 182 taken three months later with the same instrument confirms the common proper motion of the binary separated by about 0.7 arcsec. Moreover, we do not confirm the common proper motion of the faint source reported by Riaz and collaborators at ∼2 arcsec from LHS 1074. Conclusions. We derive a binary frequency of 3 ± 3% for M subdwarfs from our sample of 33 objects for separations larger than about five astronomical units. Adding to our sample the additional 28 metal-poor early-M dwarfs observed with the Hubble Space Telescope by Riaz and collaborators, we infer a binary fraction of 3.7 ± 2.6% (with a 1σ confidence limit), significantly lower than the fraction of resolved binary M dwarfs (∼20%) over the same mass and separation ranges. This result suggests a sharp cut-off in the multiplicity fraction from G to M subdwarfs, indicating that the metallicity plays a role at lower masses and/or an environmental effect governing the formation of metal-poor M dwarfs compared to their metallicity counterparts.

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Hubble Space TelescopeSearch for M Subdwarf Binaries

Cited by 27 publications

References 37 publications

Cool Subdwarf Investigations. Ii. Multiplicity

Cool Subdwarf Investigations. Ii. Multiplicity

CARMENES input catalogue of M dwarfs

Lucky Imaging of M subdwarfs

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