Search

The identification of meteorite parent bodies provides the context for understanding planetesimal formation and evolution as well as the key Solar System events they have witnessed. However, identifying such links has proven challenging and some appear ambiguous. Here, we identify that the family of asteroid fragments whose largest member is (161) Athor is the unique source of the rare EL enstatite chondrite meteorites, the closest meteorites to Earth in terms of their isotopic ratios. The Athor family was created by the collisional fragmentation of a parent body 3 Gyr ago in the inner main belt. We calculate that the diameter of the Athor family progenitor was 64 km in diameter, much smaller than the putative size of the EL original planetesimal. Therefore, we deduce that the EL planetesimal that accreted in the terrestrial planet region underwent a first catastrophic collision in that region, and one of its fragments suffered a more recent catastrophic collision in the main belt, generating the current source of the EL meteorites.

Introduction: Linking a meteorite type to a specific parent asteroid allows us to gain insight into the composition of the latter as well as the time, and indirectly the heliocentric distance of its formation. Up to now there have been established solid links between the HEDs and the inner main belt asteroid family of (4) Vesta [1] as well as between the ordinary chondrites and asteroids belonging to the so-called spectroscopic S-complex [2]. Here we report on our search for the enstatite chondrites parent body. We base our analysis on two facts: that (i) inner main belt asteroid collisional families are the most favoured to deliver meteorites to Earth, and (ii) enstatite chondrites (divided in EH and EL groups) have reflectance spectra that are within the broad asteroid spectroscopic X-complex [3]. The newly discovered asteroid families of Athor and Zita [4] are the only two families of the inner main belt that belong to the spectroscopic X-complex and thus are promising candidates. Methods and Results: In order to investigate the potential link between the enstatite chondrite meteorites and the aforementioned X-complex asteroid families, we performed near-infrared observations of a statistically significant number of members of Athor and Zita. These were combined with the visible data from the literature and finally each asteroid spectrum was classified using the most common asteroid spectral taxonomy. We showed that the Athor and Zita families are spectroscopically distinct from each other and homogenous among their respective members. Moreover, both families have distinct geometric albedo values, with Athor family being brighter. Focusing on the Athor family, we performed curve matching and absolute reflectance comparison with all the available laboratory meteorite spectra in NASA Reflectance Experiment Laboratory and Planetary Spectrophotometer Facility databases. We will report on our matching and provide a number of further evidence that inner main belt families could indeed deliver enstatite chondrites to Earth. Acknowledgments: We acknowledge support from the ANR ORIGINS (ANR-18-CE31-13-0014). CA was supported by the project “Investissements d’Avenir” UCA-JEDI (ANR-15-IDEX-01) and the European Space Agency, AM acknowledges support from the ERC advanced grant HolyEarth N. 101019380. KJW acknowledges support from the Project ESPRESSO, a NASA SSERVI program at SwRI. This work is based on data provided by the Minor Planet Physical Properties Catalogue (MP3C, mp3c.oca.eu) of the Observatoire de la Côte d'Azur. This research utilises spectra acquired at the NASA RELAB facility at Brown University and at Planetary Spectrophotometer Facility (PSF) at University of Winnipeg.References: [1] Russell C.T. et al. 2012, Science 336, 6082, 684.[2] Reddy V. et al. 2015, Asteroids IV, University of Arizona Press, Tucson, 895, 43-63[3] Vernazza P. et al. 2009. Icarus 202, 2, 477-486.[4] Delbo M. et al. 2019. Astronomy & Astrophysics 624, A69.

Asteroids, along with other small bodies, are what is left over of the original planetesimal disk from the planet-formation era. Therefore, these objects are considered the best tracers for the processes that occurred during the earliest history of our Solar System. However, the majority of asteroids are fragments generated by the collisional breakup of the planetesimals, the first ~100-km sized bodies (Morbidelli et al., 2008, Delbo' et al., 2019) that accreted in the protoplanetary disk of our Sun. Nevertheless, a small fraction of the planetesimal population survived the collisional evolution. In order to study these objects, the first step is to identify these surviving planetesimals among all the other (fragment) asteroids. To do so, we “cleaned” the inner part of the asteroid main belt (2,1 < a < 2,5) from all asteroid collisional family members (using the method of Bolin et al., 2017, Delbo' et al., 2017, 2019), thus revealing those asteroids that are not fragments that formed in the main belt. Thanks to this method, we revealed 64 surviving planetesimals in the inner main belt.We carried out a spectroscopic survey of these identified IMB planetesimals, in order to constrain their composition and mineralogy. In particular, we performed visible and near-infrared spectroscopy using several telescopes such as the 1.82m Copernico Telescopio (Asiago, Italy) for the visible spectroscopy and the 4.2 Lowell Discovery Telescope (Flagstaff, USA); the 3.2 NASA Infrared Telescope Facility (Hawaii, USA) and the Telescopio Nazionale Galileo (La Palma, Spain) for the near-infrared part. To complete our survey, we also used spectra in the visible and near-infrared published in the literature, as well as size and albedo information that we obtained from the Minor Planet Physical Properties Catalog (https://mp3c.oca.eu/). We performed the taxonomic classification following the Bus-DeMeo taxonomy (Bus et al., 2002; DeMeo et al., 2009), and using the M4AST tool (http://m4ast.imcce.fr) (Popescu et al., 2012). A visual inspection to identify the presence of absorption bands characteristic of some classes was performed to check the robustness of the automatic taxonomic classification. In addition, we compute for each planetesimal several spectral parameters, such as spectral slopes, and center, depth and area of absorption bands, when these are present. We also performed calculation of their mass, based on the method of (Carry, 2012). Finally, we used the RELAB database (Pieters, 1983), to look for meteorite analogues of each planetesimal. We found that planetesimals of the Inner Main Belt (IMB) belong mainly to the S-complex (~45%), followed by C-complex (~25%) and X-complex (~17%). Further investigations on S-complex planetesimals showed that, for a majority of them, they are best matched by spectra of ordinary chondrites meteorites. We did not find any correlation with diameters, semimajor axis and the ratio of olivine/pyroxene. Almost 60% of the C-complex planetesimals belong to the Ch/Cgh types, showing spectroscopic features associated with hydrated minerals, and consequently indicating the presence of liquid water in the early formation phases of these objects. We also found that almost 5% of the IMB planetesimals belong to the D/T types with a diameter greater than 25 km. As this taxonomical class, as well as Ch/Cgh types, are likely to have formed in the outer part of the Solar System (at 3-7 au), their presence in the IMB (2,1-2,5 au) can be explained by dynamical models invoking large semimajor axis migration of these objects (e.g., Grand Tack of Walsh et al., 2011; low-mass asteroid belt of Raymond and Izidoro, 2017b for the C-complex and Vokrouhlický et al., 2016 for the D/T types).Here, we will present the spectroscopic, physical and compositional results of our IMB planetesimals survey as well as the implications for planetary formation models.Acknowledgements: We acknowledge support from the ANR ORIGINS (ANR-18-CE31-13-0014).References : Morbidelli A. et al, Physica Scripta, Volume 130, Issue, id 014028 (2008) ; Delbo M. et al., A&A, Volume 624, id. A69 (2019) ; Bolin B. T. et al., Icarus, Volume 282, 2017, Pages 290-312 ; Delbo M. et al., Science, Volume 357, Issue 6355, pages 1026-1029, (2017) ; Bus S. J. et al., Icarus, Volume 158, Issue 1, Pages 146-177 (2002) ; DeMeo F. E. et al., Icarus, Volume 202, Issue 1, Pages 160-180 (2009); Carry, B. Planetary and Space Science, Volume 73, Issue 1, p. 98-118. (2012) ; Popescu M. et al., A&A, Volume 544, id. A130 (2012) ; Pieters, C. M., J. Geophys. Res., Volume 88, pages 9534– 9544 (1983) ; Walsh K. J. et al., Nature, Volume 475, Issue 7355, Pages 206-209 (2011) ; Raymond S. N. et al., Science Advances, Volume 3, Issue 9, Pages e1701138 (2017) ; Vokrouhlický D. et al., The Astronomical Journal, Volume 152, Issue 2, id. 39 (2016).

M dwarfs are favorable targets for exoplanet detection with current instrumentation, but stellar companions can induce false positives and inhibit planet characterization. Knowledge of stellar companions is also critical to our understanding of how binary stars form and evolve. We have therefore conducted a survey of stellar companions around nearby M dwarfs, and here we present our new discoveries. Using the DSSI speckle imager at the 4.3-meter Lowell Discovery Telescope, and the similar NESSI instrument at the 3.5-meter WIYN telescope, we carried out a volume-limited survey of M-dwarf multiplicity to 15 parsecs, with a special emphasis on including the later M dwarfs that were overlooked in previous surveys. Additional brighter targets at larger distances were included for a total sample size of 1070 M dwarfs. Observations of these 1070 targets revealed 26 new companions; 22 of these systems were previously thought to be single. If all new discoveries are confirmed, then the number of known multiples in the sample will increase by 7.6%. Using our observed properties, as well as the parallaxes and 2MASS K magnitudes for these objects, we calculate the projected separation, and estimate the mass ratio and component spectral types, for these systems. We report the discovery of a new M-dwarf companion to the white dwarf Wolf 672 A, which hosts a known M-dwarf companion as well, making the system trinary. We also examine the possibility that the new companion to 2MASS J13092185-2330350 is a brown dwarf. Finally, we discuss initial insights from the POKEMON survey., Comment: 23 pages, 6 figures, 5 tables. Accepted for publication in the Astronomical Journal

Introduction We invite observers to join an international observing campaign and obtain light curve of a selected number of the most ancient asteroids. Analysis of these data will be important to reconstruct the original state of the asteroid belt, which is a crucial problem of planetary science. This original state can be reconstructed through the identification of the oldest asteroid families. Traditional identification methods, like Hierarchical Clustering Methods (Zappala et al., 1990; HCM), have difficulties to recognise Gyr- and older asteroid families, whose members are very dispersed by the Yarkovsky effect. An innovative method, called V-shape search (Bolin et al., 2017), has been demonstrated effective (Deienno et al. 2021) to identify these aforementioned very old collisional families by searching for the signature of the size dependent dispersion of family members operated by the Yarkovsky effect. The method has already successfully identified two primordial families which likely formed before the giant planet orbital instability (Tsiganis et al., 2005) and could be as old as the Solar System and an ancient one that is ~3 Gyr-old (Delbo et al., 2017; 2019). There is evidence from observations and theoretical evolution models that there are more old families to be detected (Delbo et al., 2017; Dermott et al., 2018). However, the reliability of these V-shape families should be independently verified. A very important test of family membership is the anisotropic distribution of spin vectors of the asteroid family member, which is a fingerprint of the Yarkovsky effect evolution (Hanus et al. 2013). Namely, to test the working hypothesis that according to theories of asteroid orbital evolution under the Yarkovsky effect, members of the inward (outward) side of V-shape of a family have a statistical predominance of retrograde (prograde) objects (Fig. 1). This hypothesis has been tested (Hanus, et al., 2013) already for known families, and it is a reliable test for family membership. The observing campaign: Ancient Asteroids For this purpose, an international observing campaign called Ancient Asteroids has been put forward at different observatories worldwide: (University of Athens Observatory (UOAO), Greece, the BSA Observatory and Bigmuskie Observatory, Italy, the Observatoire de la Côte d’Azur (OCA), France, the Lowell Observatory in Arizona, United States, the Astronomical Institute of the Charles University in Prague, Czech Republic, the Aristotle University of Thessaloniki in Thessaloniki, Greece. The main goal of the campaign is to establish an international network of professional and amateur astronomers (Pro-Am collaboration), in order to perform photometric observations of a very specific sample of the most ancient asteroids. A special website (http://users.uoa.gr/~kgaze/research_asteroids_en.html) was developed for the purpose of the campaign, that includes guidelines for the participation, the observations and the image data evaluation and collection. In the frame of Ancient Asteroids campaign, a user-friendly web application was also developed for the target selection and observing plan preparation. The user can easily find the observable asteroids for the campaign based on the location, the time and the equipment limitations. The targets are displayed with a priority rate, in order to perform smart sampling. The user selects the favor target and an observing plan automatically is created. The contribution The obtained lightcurves from all the involved participants will be combined with data available in the literature, as well as with sparse data from space missions (Gaia, TESS, etc) and global sky surveys (PTF, LSST, ATLAS, etc). Thus, the spin state of the asteroids can be revealed. The results will be ingested to the Minor Planet Physical Properties Catalogue (MP3C) program (https://mp3c.oca.eu/catalogue/index.htm), the largest database of asteroid physical properties, which complies with the EU vision for open data. The observing campaign Ancient Asteroids has started to collect photometric observations with the contribution of amateur astronomers from Italy, France and Greece are submitted. The observations will reveal the spin state of the members, which are crucial for the testing the hypothesis of the family membership. This research will potentially lead to a better understanding of the first stages of the evolution of the Solar System, the mechanism at the origin of the formation of the asteroids and the planet formation processes. Acknowledgments This work was also partially supported by the ANR ORIGINS (ANR-18-CE31-0014) and by the French National Program of Planetology (PNP). Here we make use of asteroid physical properties data from Minor Planet Physical Properties Catalog (https://mp3c.oca.eu/). References Bolin, B. T. et al. (2017). Icarus, 282, 290-312. Deienno, R. et al. (2021). Icarus, 357, 114218. Delbo, M. et al. (2019). Astronomy & Astrophysics, 624, A69. Delbo, M. et al. (2017). Science, 357, 6355. Dermott, S. F. et al. (2018). Nature Astronomy, 2, 7. Hanus, J. et al. (2013). Astronomy & Astrophysics, 559. Hanus, J. et al. (2013). Astronomy & Astrophysics, 551. Tsiganis K. et al. (2005). Nature, 435, 7041. Zappala, V. et al. (1990). Astrophysical Journal, 100, 2030-2046.

We present the first results from the POKEMON (Pervasive Overview of Kompanions of Every M-dwarf in Our Neighborhood) survey, the largest speckle survey of stellar multiplicity ever produced forthe objects that comprise over 70% of the stars in our galaxy: the M-dwarfs. We have conducted a volume-limited survey through M9 that inspected, at diffraction-limited resolution, every M-dwarf out to 15pc, with additional brighter targets to 25pc. POKEMON utilized the Differential Speckle Survey Instrument (DSSI) at the 4.3m Lowell Discovery Telescope, along with the NN-Explore Exoplanet Stellar Speckle Imager (NESSI) on the 3.5-m WIYN telescope. We report the discovery of 30+ new companions to these nearby M-dwarfs. Given the priority these targets have for exoplanet studies with TESS, and in the future JWST – and the degree to which initially undetected multiplicity has skewed Kepler results – a comprehensive survey of our nearby low-mass neighbors provides a homogeneous, complete catalog of fundamental utility. Prior knowledge of secondary objects – or robust non-detections, as captured by this survey – immediately clarify the nature of exoplanet transit detections from these current and upcoming missions.

We present a serendipitous discovery of a new stellar companion to TYC 5493-889-1 detected with the Differential Speckle Survey Instrument at the 4.3 m Lowell Discovery Telescope. We also present photometric observations of TYC 5493-889-1, and determine a spectral type of F1V and a photometric distance of roughly 320 parsecs.

International audience; We discuss science cases to support the development of sub-au imaging capabilities to image forming planets in the terrestrial region of nearby proto-planetary disks.

We present a set of {\it Spitzer} 24$\mu$m MIPS time series observations of the M-dwarf eclipsing binary star GU Bo\"otis. Our data cover three secondary eclipses of the system: two consecutive events and an additional eclipse six weeks later. The study's main purpose is the long wavelength (and thus limb darkening-independent) characterization of GU Boo's light curve, allowing for independent verification of the results of previous optical studies. Our results confirm previously obtained system parameters. We further compare GU Boo's measured 24$\mu$m flux density to the value predicted by spectral fitting and find no evidence for circumstellar dust. In addition to GU Boo, we characterize (and show examples of) light curves of other objects in the field of view. Analysis of these light curves serves to characterize the photometric stability and repeatability of {\it Spitzer's} MIPS 24\micron array over short (days) and long (weeks) timescales at flux densities between approximately 300--2,000$\mu$Jy. We find that the light curve root mean square about the median level falls into the 1--4% range for flux densities higher than 1mJy. Finally, we comment on the fluctuations of the 24\micron background on short and long timescales., Comment: ApJ accepted. 10 pages, 12 figures

Using the CHARA Array and the Palomar Testbed Interferometer, the chemically peculiar star $\lambda$ Bo\"{o}tis has been spatially resolved. We have measured the limb darkened angular diameter to be $\theta_{LD} = 0.533\pm0.029$ mas, corresponding to a linear radius of $R_{\star} = 1.70 \pm 0.10 R_\odot$. The measured angular diameter yields an effective temperature for $\lambda$ Boo of $T_{eff} = 8887 \pm 242$ K. Based upon literature surface gravity estimates spanning $\log{(g)} = 4.0-4.2$ $[\rm{cm s}^{-\rm{2}}]$, we have derived a stellar mass range of $M_{\star} = 1.1 - 1.7$ $M_\odot$. For a given surface gravity, the linear radius uncertainty contributes approximately $\sigma(M_\star) = 0.1-0.2 M_\odot$ to the total mass uncertainty. The uncertainty in the mass (i.e., the range of derived masses) is primarily a result of the uncertainty in the surface gravity. The upper bound of our derived mass range ($\log(g)=4.2, M_\star = 1.7\pm0.2 M_\odot$) is consistent with 100-300 MYr solar-metallicity evolutionary models. The mid-range of our derived masses ($\log(g)=4.1, M_\star = 1.3\pm0.2 M_\odot$) is consistent with 2-3 GYr metal-poor evolutionary models. A more definitive surface gravity determination is required to determine a more precise mass for $\lambda$ Boo.

Direct angular size measurements of the G0IV subgiant $\eta$ Boo from the Palomar Testbed Interferometer are presented, with limb-darkened angular size of $\theta_{LD}= 2.1894^{+0.0055}_{-0.0140} $ mas, which indicate a linear radius of $R=2.672 \pm 0.028 R_\odot$. A bolometric flux estimate of $F_{BOL} = 22.1 \pm 0.28\times 10^{-7}$ erg cm$^{-2}$s$^{-1}$ is computed, which indicates an effective temperature of $T_{EFF}=6100 \pm 28$ K and luminosity of $L = 8.89 \pm 0.16 L_\odot$ for this object. Similar data are established for a check star, HD 121860. The $\eta$ Boo results are compared to, and confirm, similar parameters established by the {\it MOST} asteroseismology satellite. In conjunction with the mass estimate from the {\it MOST} investigation, a surface gravity of $\log g=3.817 \pm 0.016$ [cm s$^{-2}$] is established for $\eta$ Boo.

We present four MIPS (24 \micron) and two IRAC (3.6, 4.5, 5.8, and 8.0 \micron) Spitzer observations of the newly discovered Tremendous Outburst Amplitude Dwarf nova (TOAD) Var Her 04 during decline from super-outburst. The four MIPS observations span 271 days and the two IRAC observations span 211 days. Along the line-of-sight to Var Her 04, there is a foreground M-star within 1\arcsec of the variable; as a result, all of the Spitzer photometry presented in this paper is a blend of the foreground M-star and Var Her 04. We estimate the quiescent level of the TOAD to be $\Delta V=4-5$ magnitudes below that of the M-star. Based upon the spectral energy distribution and the 2MASS colors, we find the M-star to be an M3.5V dwarf at a distance of 80-130 pc. Based upon its outburst amplitude and quiescent apparent magnitude, we estimate the distance to Var Her 04 to be 200-400 pc, suggesting that the line-of-sight foreground star is physically unrelated to the cataclysmic variable. All of the Spitzer photometry is consistent with the photospheric emission of the line-of-sight M3.5V star, except for one 24 \micron observation obtained after the variable re-brightened. This 24 \micron flux density is 75 $\mu$Jy ($4\sigma$) above the preceding and following MIPS observations. We tentatively suggest that the mid-infrared brightening of 75 $\mu$Jy may be associated with a dust formation event in the super-outburst ejecta. Assuming a dust temperature of 100-400 K, we have estimated the amount of dust required. We find $10^{-13}-10^{-11}$ M$_\odot$ of dust is needed, consistent with amounts of mass ejection in TOADs expected during super-outburst, and possibly making TOADs important contributors to the recycling of the interstellar medium.

We present the first observations of magnetic cataclysmic variables with the Spitzer Space Telescope. We used the Infrared Array Camera to obtain photometry of the polars EF Eri, GG Leo, V347 Pav, and RX J0154.0-5947 at 3.6, 4.5, 5.8, and 8.0 $\mu$m. In all of our targets, we detect excess mid-infrared emission over that expected from the component stars alone. We explore the origin of this IR excess by examining bremsstrahlung, cyclotron emission, circumbinary dust, and L/T brown dwarf secondary stars. Bremsstrahlung and cyclotron emission appear unlikely to be significant contributors to the observed fluxes. At present, the most likely candidate for the excess emission is dust that is probably located in a circumbinary disk with an inner temperature near 800 K. However, a simple dust disk plus any reasonable low mass or brown dwarf-like secondary star is unable to fully explain the observed flux densities in the 3--8 $\mu$m region., Comment: Accepted to ApJ Letters

We present results from a 5 night wide‐field time‐series photometric survey that detects variable field stars. We find that the fraction of stars whose light curves show variations depends on color and magnitude, reaching 17% for the brightest stars in this survey ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $V\sim 14$ \end{document} ) for which the photometric precision is best. The fraction of stars found to be variable is relatively high at colors bluer than the Sun and relatively low at colors similar to the Sun...

We present infrared interferometric angular size measurements for the A7IV-V star Altair that indicate a noncircular projected disk brightness distribution. Given the known rapid rotation of this star, we model the data as arising from an elongated rigid atmosphere. To first order, an ellipse may be fitted to our interferometric diameter measurements, with major and minor axes of 2a = 3.461 ± 0.038 mas and 2b = 3.037 ± 0.069 mas, respectively, for a difference of 424 ± 79 μas between 2a and 2b, and with an axial ratio of a/b = 1.140 ± 0.029. Assuming that the apparent oblateness of the photosphere is due to the star's rapid rotation, a more rigorous evaluation of the observation data in the context of a rigidly rotating Roche model shows that an estimate of v sin i = 210 ± 13 km s-1 can be derived that is independent of spectroscopic techniques. Also derived are values for the mean effective temperature and the mean linear radius, and an observational constraint upon the relationship between rotation velocity and stellar inclination is established. Altair is the first main-sequence star for which direct observations of an oblate photosphere have been reported and the first star for which v sin i has been established from observations of the star's photospheric geometry.

Reliable prediction of stellar diameters, particularly angular diameters, is a useful and necessary tool for the increasing number of milliarcsecond resolution studies being carried out in the astronomical community. A new and accurate technique of predicting angular sizes is presented for main sequence stars, giant and supergiant stars, and for more evolved sources such as carbon stars and Mira variables. This technique uses observed $K$ and either $V$ or $B$ broad-band photometry to predict V=0 or B=0 zero magnitude angular sizes, which are then readily scaled to the apparent angular sizes with the $V$ or $B$ photometry. The spread in the relationship is 2.2% for main sequence stars; for giant and supergiant stars, 11-12%; and for evolved sources, results are at the 20-26% level. Compared to other simple predictions of angular size, such as linear radius-distance methods or black-body estimates, zero magnitude angular size predictions can provide apparent angular sizes with errors that are 2 to 5 times smaller., Comment: 28 pages, 4 figures, accepted by PASP

Based on CHARA Array measurements, we present the angular diameters of 23 nearby, main- sequence stars, ranging from spectral type A7 to K0, five of which are exoplanet host stars. We derive linear radii, effective temperatures, and absolute luminosities of the stars using HIPPARCOS parallaxes and measured bolometric fluxes. The new data are combined with previously published values to create an Angular Diameter Anthology of measured angular diameters to main-sequence stars (luminosity class V and IV). This compilation consists of 125 stars with diameter uncertainties of less than 5%, ranging in spectral types from A to M. The large quantity of empirical data are used to derive color-temperature relations to an assortment of color indices in the Johnson (BVRIJHK), Cousins (RI), Kron (RI), Sloan (griz), and WISE (W3W4) photometric systems. These relations have an average standard deviation of ~3% and are valid for stars with spectral types A0 to M4. To derive even more accurate relations for Sun-like stars, we also determined these temperature relations omitting early-type stars (Teff > 6750 K) that may have biased luminosity estimates because of rapid rotation; for this subset the dispersion is only ~2.5%. We find effective temperatures in agreement within a couple percent for the interferometrically characterized sample of main sequence stars compared to those derived via the infrared-flux method and spectroscopic analysis., Comment: Accepted for Publication in ApJ

We present interferometric diameter measurements of 21 K- and M- dwarfs made with the CHARA Array. This sample is enhanced by literature radii measurements to form a data set of 33 K-M dwarfs with diameters measured to better than 5%. For all 33 stars, we compute absolute luminosities, linear radii, and effective temperatures (Teff). We develop empirical relations for \simK0 to M4 main- sequence stars between the stellar Teff, radius, and luminosity to broad-band color indices and metallicity. These relations are valid for metallicities between [Fe/H] = -0.5 and +0.1 dex, and are accurate to ~2%, ~5%, and ~4% for Teff, radius, and luminosity, respectively. Our results show that it is necessary to use metallicity dependent transformations to convert colors into stellar Teffs, radii, and luminosities. We find no sensitivity to metallicity on relations between global stellar properties, e.g., Teff-radius and Teff-luminosity. Robust examinations of single star Teffs and radii compared to evolutionary model predictions on the luminosity-Teff and luminosity-radius planes reveals that models overestimate the Teffs of stars with Teff < 5000 K by ~3%, and underestimate the radii of stars with radii < 0.7 R\odot by ~5%. These conclusions additionally suggest that the models overestimate the effects that the stellar metallicity may have on the astrophysical properties of an object. By comparing the interferometrically measured radii for single stars to those of eclipsing binaries, we find that single and binary star radii are consistent. However, the literature Teffs for binary stars are systematically lower compared to Teffs of single stars by ~ 200 to 300 K. Lastly, we present a empirically determined HR diagram for a total of 74 nearby, main-sequence, A- to M-type stars, and define regions of habitability for the potential existence of sub-stellar mass companions in each system. [abridged], 73 pages, 12 Tables, 18 Figures. Accepted for publication in The Astrophysical Journal

We have executed a survey of nearby, main sequence A, F, and G-type stars with the CHARA Array, successfully measuring the angular diameters of fortyfour stars with an average precision of ~ 1.5%. We present new measures of the bolometric flux, which in turn leads to an empirical determination of the effective temperature for the stars observed. In addition, these CHARA-determined temperatures, radii, and luminosities are fit to Yonsei-Yale model isochrones to constrain the masses and ages of the stars. These results are compared to indirect estimates of these quantities obtained by collecting photometry of the stars and applying them to model atmospheres and evolutionary isochrones. We find that for most cases, the models overestimate the effective temperature by ~ 1.5-4%, when compared to our directly measured values. The overestimated temperatures and underestimated radii in these works appear to cause an additional offset in the star's surface gravity measurements, which consequently yield higher masses and younger ages, in particular for stars with masses greater than ~1.3 Msun. Additionally, we compare our measurements to a large sample of eclipsing binary stars, and excellent agreement is seen within both data sets. Finally, we present temperature relations with respect to (B-V) and (V-K) color as well as spectral type showing that calibration of effective temperatures with errors ~ 1% is now possible from interferometric angular diameters of stars., 125 pages, 12 tables, 25 figures, accepted for publication in ApJ

The ESO Very Large Telescope Interferometer (VLTI) offers access to the four 8-m Unit Telescopes (UT) and the four 1.8-m Auxiliary Telescopes (AT) of the Paranal Observatory located in the Atacama Desert in northern Chile. The two VLTI instruments, MIDI and AMBER deliver regular scientific results. In parallel to the operation, the instruments developments are pursued, and new modes are studied and commissioned to offer a wider range of scientific possibilities to the community. New configurations of the ATs array are discussed with the science users of the VLTI and implemented to optimize the scientific return. The monitoring and improvement of the different systems of the VLTI is a continuous work. The PRIMA instrument, bringing astrometry capability to the VLTI and phase referencing to the instruments has been successfully installed and the commissioning is ongoing. The possibility for visiting instruments has been opened to the VLTI facility.

Commission 54 held its business meeting on 11 August 2009 at “Botequim” at Rua Visconde de Caravelas 184/186, Humaitá, Botafogo, Rio de Janeiro. Individual members in attendance reported on activities of relevance to C54.

The Phase-Referenced Imaging and Micro-arcsecond Astrometry (PRIMA) facility is scheduled for installation in the Very Large Telescope Interferometer observatory in Paranal, Chile, in the second half of 2008. Its goal is to provide astrometric accuracy in the micro-arcsecond range. High precision astrometry can be applied to explore the dynamics of the dense stellar cluster. Especially models for the formation of stars near super massive black holes or the fast transfer of short-lived massive stars into the innermost parsec of our galaxy can be tested. By measuring the orbits of stars close to the massive black hole one can probe deviations from a Keplerian motion. Such deviations could be due to a swarm of dark, stellar mass objects that perturb the point mass solution. At the same time the orbits are affected by relativistic corrections which thus can be tested. The ultimate goal is to test the effects of general relativity in the strong gravitational field. The latter can be probed with the near infrared flares of SgrA* which are most likely due to accretion phenomena onto the black hole. We study the expected performance of PRIMA for astrometric measurements in the Galactic Center based on laboratory measurements and discuss possible observing strategies., Presentation at the SPIE 2008 conference "Optical and Infrared Interferometry"

The VLTI's PRIMA (Phase-Referenced Imaging and Microarcsecond Astrometry) instrument is designed to provide tens of microarcseond astrometry and faint-object imaging for the interferometer facility. Astrometry is to be enabled by PRIMA between object pairs that are separated on the sky by one isoplanatic patch (roughly 60 seconds of arc at Cerro Paranal in the K band), with at least one of the two objects being bright ( K

The ESO Very Large Telescope Interferometer (VLTI) offers access to the four 8 m Unit Telescopes (UT) and the four 1.8 m Auxiliary Telescopes (AT) of the Paranal Observatory located in the Atacama Desert in northern Chile. The fourth AT has been delivered to operation in December 2006, increasing the flexibility and simultaneous baselines access of the VLTI. Regular science operations are now carried on with the two VLTI instruments, AMBER and MIDI. The FINITO fringe tracker is now used for both visitor and service observations with ATs and will be offered on UTs in October 2008, bringing thus the fringe tracking facility to VLTI instruments. In parallel to science observations, technical periods are also dedicated to the characterization of the VLTI environment, upgrades of the existing systems, and development of new facilities. We will describe the current status of the VLTI and prospects on future evolution.

The Fringe Sensor Unit (FSU) is the central element of the dual-feed facility PRIMA at the VLT Interferometer (VLTI). Two identical FSU fringe detectors deliver real-time estimates of phase delay, group delay and signal-to-noise ratio for the two observed targets. They serve both as the scientific instrument for astrometry with PRIMA and as sensor for the fringe tracking system of the interferometer. Prior to its installation at the VLTI scheduled for mid-2008, the FSU is going through an extensive laboratory test phase. It is therefore embedded in a semi-realistic environment, involving a VLTI-like control system and a laser metrology. This allows us to probe the system response to atmospheric piston jitter, tip-tilt disturbances and higher order aberrations, as they are expected at the observatory. We report on the system test results, outline the optimisation of the calibration procedure and we evaluate the FSU fringe tracking performance under realistic conditions. Finally, we compare the obtained performances to the scientific and technical requirements.

We present the Gattini project: a multisite campaign to measure the optical sky properties above the two high altitude Antarctic astronomical sites of Dome C and Dome A. The Gattini-DomeC project, part of the IRAIT site testing campaign and ongoing since January 2006, consists of two ca meras for the measurement of optical sky brightness, large area cloud cover and auroral detection above the DomeC site, home of the French-Italian Conc ordia station. The cameras are transit in nature and are virtually identical except for the nature of the lenses. The cameras have operated successfully throughout the past two Antarctic winter seasons and here we present the first results obtained from the returned 2006 dataset. The Gattini-DomeA project will place a similar site testing facility at the highest point on the Antarctic plateau, Dome A, with observations commencing in 2008. The project forms a small part of a much larger venture coordinated by the Polar Research Institute of China as part of the International Polar Year whereby an automated site testing facility called PLATO will be traversed into the DomeA site. The status of this exciting and ambitious project with regards to the Gattini-DomeA cameras will be presented. Keywords: Antarctica, optical sky brightness, site testing cameras, Gattini

The NASA Outrigger Telescope Project is a ground-based component of NASA's Navigator Program. The proposed project would utilize four to six 1.8-meter telescopes with co-rotating domes configured as an interferometer. One of the project’s scientific goals is the detection of exoplanets, which would be accomplished with long baseline narrow-angle astrometry. This astrometry mode would be able to detect Uranus mass planets up to 60 light years away. The requirements of narrow-angle astrometry, both technically and operationally, levy requirements on the telescopes and enclosures, including, for example, wavefront quality, pivot stability, and slew speed. This paper will describe these requirements and how they were achieved in the design. It will also discuss the testing and verification of these requirements. Actual telescope performance as tested at EOS Technologies is presented elsewhere in these proceedings.

The Antarctic Planet Interferometer is an instrument concept designed to detect and characterize extrasolar planets by exploiting the unique potential of the best accessible site on earth for thermal infrared interferometry. High-precision interferometric techniques under development for extrasolar planet detection and characterization (differential phase, nulling and astrometry) all benefit substantially from the slow, low-altitude turbulence, low water vapor content, and low temperature found on the Antarctic plateau. At the best of these locations, such as the Concordia base being developed at Dome C, an interferometer with two-meter diameter class apertures has the potential to deliver unique science for a variety of topics, including extrasolar planets, active galactic nuclei, young stellar objects, and protoplanetary disks.

A key thrust of NASA's Origins program is the development of astronomical interferometers. Pursuing this goal in a cost-effective and expedient manner from the ground has led NASA to develop the Keck Interferometer, which saw first fringes between the twin 10m Keck telescopes in March of 2001. In order to enhance the imaging potential of this facility, and to add astrometric capabilities for the detection of giant planets about nearby stars, four 1.8 m 'outrigger' telescopes may be added to the interferometer. Robust performance of the multi-aperture instrument will require precise alignment of the large number of optical elements found in the six optical beamtrains spread about the observatory site. The requirement for timely and reliable alignments dictated the development of an automatic alignment system for the Keck Interferometer. The autoaligner consists of swing-arm actuators that insert light-emitting diodes on the optical axis at the location of each optical element, which are viewed by a simple fixed-focus CCD camera at the end of the beamtrain. Sub-pixel centroiding is performed upon the slightly out-of-focus target spots using images provided by a frame grabber, providing steering information to the two-axis actuated optical elements. Resulting mirror-to-mirror alignments are good to within 2 arcseconds, and trimming the alignment of a full beamtrain is designed to take place between observations, within a telescope repointing time. The interactions of the autoaligner with the interferometer delay lines and coude trains are discussed in detail. The overall design of the interferometer's autoaligner system is presented, examining the design philosophy, system sequencing, optical element actuation, and subsystem co-alignment, within the context of satisfying performance requirements and cost constraints.

A dedicated program of measuring angular sizes of Mira variables using the Palomar Testbed Interferometer has resulted in more than 13,000 measurements of over 60 stars. With visibility data in five channels across the K band, atmospheric extension and sources of opacity are evident in the dataset. Using multiple-epoch narrow-band data, phase lags between wavelength-dependent angular size cycles indicate spatial extent of molcular atmospheres. A spectral angular diameter classification system is developed, based on the recurring shapes of the spectral traces seen in the dataset, which correlates to spectral type. A period-radius relationship is explored, and a refinement on the estimation of angular sizes is made.

We present observations of several T Tauri stars using long baseline infrared interferometry from the Palomar Testbed Interferometer. The target sources, T Tau N, SU Aur, RY Tau and DR Tau, are all known to be surrounded by dusty circumstellar disks. The observations directly trace the inner regions (

We discuss recent work from the Palomar Testbed Interferometer (PTI), including science results and system improvements. In the past two years PTI has been used to observe a wide range of scientifically interesting sources, including binaries, Cepheids and Miras. In addition PTI has been used to observe departures from spherical symmetry in several stars. Recent system improvements incude a new low read-noise camera based on a HAWAII infrared array, routine opteration in two baselines, and operation in the J band. Future developments include an upgrade to three-aperture combination and closure phase measurements, and double-Fourier interferometry.

Using the Navy Precision Optical Interferometer, we measured the angular diameters of 10 stars that have previously measured solar-like oscillations. Our sample covered a range of evolutionary stages but focused on evolved subgiant and giant stars. We combined our angular diameters with Hipparcos parallaxes to determine the stars' physical radii, and used photometry from the literature to calculate their bolometric fluxes, luminosities, and effective temperatures. We then used our results to test the scaling relations used by asteroseismology groups to calculate radii and found good agreement between the radii measured here and the radii predicted by stellar oscillation studies. The precision of the relations is not as well constrained for giant stars as it is for less evolved stars.

JPL and CARA are building a multi-element, IR interferometer for NASA to be situated at the twin Keck Observatories on Mauna Kea, Hawaii. Initially, the 10-m diameter Keck telescopes will be augmented with four fixed-location 2-m class outrigger telescopes resulting in 15 non-redundant baselines, the longest being approximately equals 110 m or nearly 5 X 107 ((lambda) /2.2micrometers )-1 wavelengths. Fast adaptive optics and tip-tilt corrections will be used to phase up the Keck and outrigger apertures, respectively. The entire array will be co-phased by observing a relatively bright target on the photon rich Keck-Keck (K-K) and Keck- outrigger (K-O) baselines. When fully phased, the projected fringe phaser sensitivity for unresolved targets will be K- 22.0, 20.0 and 17.9 on the K-K, K-O and O-O baselines, respectively. Synthetic imaging capability will be available in the 1.6-10.0 micrometers atmospheric transmission bands at angular resolutions of 4.0 milli-arcseconds. In this article, we briefly outline the adopted methodology, imaging hardware, projected sensitivities and summarize the scientific potential of the instrument as an imaging interferometer.

The Palomar Testbed Interferometer is a long-baseline, near-infrared astronomical interferometer capable of visibility measurement and narrow-angle differential astrometry. In this submission we consider the problem of fringe amplitude calibration as applied to the study of single and binary star systems with PTI. Methodologies for selecting appropriate calibration objects, and performing the calibrations to produce consistent multi-night datasets are considered. Applications of such calibrated datasets to binary orbit determination and stellar diameter measurements will be presented.

A key thrust of NASA's Origins program is the search for and detection of planetary systems about other stars. Pursuing this goal in a cost-effective and expedient manner from the ground has led NASA to begin work on the Keck Interferometer, which will add 4 1.8m 'outrigger' telescopes at the Keck Observatory on Mauna Kea. In addition to the imaging science to be performed by the Keck 10m telescopes with the outriggers, another one of the principal capabilities of the instrument will be the ability for the outriggers to conduct relative astrometry at the 25 microarcsecond level per root hour. Astrometry of this accuracy will enable the array to detect planetary systems composed of Uranus-mass or larger bodies orbiting at 5 AU solar mass stars at a distance of 20 pc; over 300 stars are to be surveyed by the outriggers annually. The astrometric capabilities of the Keck array can also be utilized other astrophysical investigations, such as characterization of spectroscopic binary orbits, and the measurement of the center-of-light shift of MACHO microlensing events, which will allow for a model-independent determinations of lens masses.

The Palomar Testbed Interferometer (PTI) is an infrared, phase-tracking interferometer in operation at Palomar Mountain since July 1995. It was funded by NASA for the purpose of developing techniques and methodologies for doing narrowangle astrometry for the purpose of detecting extrasolar planets. The instrument employs active fringe trackingin the infrared (2.0-2.4 μm) to monitor fringe phase. It is a dual-star interferometer; it is able to measure fringes on two separate stars simultaneously. An end-to-end heterodyne laser metrology system is used to monitor the optical path length of the starlight. Recently completed engineering upgrades have improved the initial instrument performance. These upgrades are:extended wavelength coverage, a single mode fiber for spatial filtering, vacuum pipes to relay the beams, accelerometers on the siderostat mirrors and a new baseline. Results of recent astrometry data indicate the instrument is approaching the astrometric limit as set by the atmosphere.

International audience; The ultimate astronomical observatory would be a formation flying space interferometer, combining sensitivity and stability with high angular resolution. The smallSat revolution offers a new and maturing prototyping platform for space interferometry and we put forward a realistic plan for achieving first stellar fringes in space by 2030.

Cool, evolved stars are the main source of chemical enrichment of the interstellar medium (ISM), and understanding their mass loss and structure offers a unique opportunity to study the cycle of matter in the Universe. Pulsation, convection, and other dynamic processes in cool evolved stars create an atmosphere where molecules and dust can form, including those necessary to the formation of life (e.g.~Carbon-bearing molecules). Understanding the structure and composition of these stars is thus vital to several aspects of stellar astrophysics, ranging from ISM studies to modeling young galaxies and exoplanet research. Recent modeling efforts and increasingly precise observations now reveal that our understanding of cool stars photospheric, chromospheric, and atmospheric structures is limited by inadequate knowledge of the dynamic and chemical processes at work. Here we outline promising scientific opportunities for the next decade. We identify and discuss the following main opportunities: (1) identify and model the physical processes that must be included in current 1D and 3D atmosphere models of cool, evolved stars; (2) refine our understanding of photospheric, chromospheric, and outer atmospheric regions of cool evolved stars, their properties and parameters, through high-resolution spectroscopic observations, and interferometric observations at high angular resolution; (3) include the neglected role of chromospheric activity in the mass loss process of red giant branch and red super giant stars, and understand the role played by their magnetic fields; (4) identify the important shaping mechanisms for planetary nebulae and their relation with the parent asymptotic giant branch stars., Comment: 10 pages, 2 figures, White Paper submitted to the Astronomy and Astrophysics Decadal Survey (Astro2020)

International audience