H. Zinnecker

NASA, Вашингтон, West Virginia, United States

Are you H. Zinnecker?

Claim your profile

Publications (409)722.31 Total impact

  • Source
    Preview · Article · May 2016 · Astronomy and Astrophysics
  • [Show abstract] [Hide abstract] ABSTRACT: Context. Theoretical scenarios propose that high-mass stars are formed by disk-mediated accretion. Aims. To test the theoretical predictions on the formation of massive stars, we wish to make a thorough study at high-angular resolution of the structure and kinematics of the dust and gas emission toward the high-mass star-forming region G35.03+0.35, which harbors a disk candidate around a B-type (proto)star. Methods. We carried out ALMA Cycle 0 observations at 870 μm of dust of typical high-density, molecular outflow, and cloud tracers with resolutions of 10^7 cm^(-3), and masses in the range 1–5 M_⊙, and they are subcritical. Core A, which is associated with a hypercompact Hii region and could be the driving source of the molecular outflow observed in the region, is the most chemically rich source in G35.03+0.35 with strong emission of typical hot core tracers such as CH_3CN. Tracers of high density and excitation show a clear velocity gradient along the major axis of the core, which is consistent with a disk rotating about the axis of the associated outflow. The PV plots along the SE–NW direction of the velocity gradient show clear signatures of Keplerian rotation, although infall could also be present, and they are consistent with the pattern of an edge-on Keplerian disk rotating about a star with a mass in the range 5–13 M_⊙. The high t_(ff)/t_(rot) ratio for core A suggests that the structure rotates fast and that the accreting material has time to settle into a centrifugally supported disk. Conclusions. G35.03+0.35 is one of the most convincing examples of Keplerian disks rotating about high-mass (proto)stars. This supports theoretical scenarios according to which high-mass stars, at least B-type stars, would form through disk-mediated accretion.
    No preview · Article · Nov 2014 · Astronomy and Astrophysics
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: Multiplicity is one of the most fundamental observable properties of massive O-type stars and offers a promising way to discriminate between massive star formation theories. Nevertheless, companions at separations between 1 and 100 mas remain mostly unknown due to intrinsic observational limitations. [...] The Southern MAssive Stars at High angular resolution survey (SMASH+) was designed to fill this gap by providing the first systematic interferometric survey of Galactic massive stars. We observed 117 O-type stars with VLTI/PIONIER and 162 O-type stars with NACO/SAM, respectively probing the separation ranges 1-45 and 30-250mas and brightness contrasts of Delta H < 4 and Delta H < 5. Taking advantage of NACO's field-of-view, we further uniformly searched for visual companions in an 8''-radius down to Delta H = 8. This paper describes the observations and data analysis, reports the discovery of almost 200 new companions in the separation range from 1mas to 8'' and presents the catalog of detections, including the first resolved measurements of over a dozen known long-period spectroscopic binaries. Excluding known runaway stars for which no companions are detected, 96 objects in our main sample (DEC < 0 deg; H<7.5) were observed both with PIONIER and NACO/SAM. The fraction of these stars with at least one resolved companion within 200mas is 0.53. Accounting for known but unresolved spectroscopic or eclipsing companions, the multiplicity fraction at separation < 8'' increases to f_m = 0.91 +/- 0.03. The fraction of luminosity class V stars that have a bound companion reaches 100% at 30mas while their average number of physically connected companions within 8'' is f_c = 2.2 +/- 0.3. This demonstrates that massive stars form nearly exclusively in multiple systems. Additionally, the nine non-thermal (NT) radio emitters observed by SMASH+ are all resolved [...]
    Full-text · Article · Sep 2014 · The Astrophysical Journal Supplement Series
  • [Show abstract] [Hide abstract] ABSTRACT: SOFIA is a joint project between NASA and DLR, the German Aerospace Center, to provide the worldwide astronomical community with an observatory that offers unique capabilities from visible to far-infrared wavelengths. SOFIA consists of a 2.7-m telescope mounted in a highly modified Boeing 747-SP aircraft, a suite of instruments, and the scientific and operational infrastructure to support the observing program. This paper describes the current status of the observatory and details the General Investigator program. The observatory has recently completed major development activities, and it has transitioned into full operational status. Under the General Investigator program, astronomers submit proposals that are peer reviewed for observation on the facility. We describe the results from the first two cycles of the General Investigator program. We also describe some of the new observational capabilities that will be available for Cycle 3, which will begin in 2015.
    No preview · Conference Paper · Jul 2014
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: Context. The formation process of high-mass stars (with masses >8 M_⊙) is still poorly understood, and represents a challenge from both the theoretical and observational points of view. The advent of the Atacama Large Millimeter Array (ALMA) is expected to provide observational evidence to better constrain the theoretical scenarios. Aims. The present study aims at characterizing the high-mass star forming region G35.20−0.74 N, which is found associated with at least one massive outflow and contains multiple dense cores, one of them recently found associated with a Keplerian rotating disk. Methods. We used the radio-interferometer ALMA to observe the G35.20−0.74 N region in the submillimeter continuum and line emission at 350 GHz. The observed frequency range covers tracers of dense gas (e.g., H^(13)CO^+, C^(17)O), molecular outflows (e.g., SiO), and hot cores (e.g., CH_3CN, CH_3OH). These observations were complemented with infrared and centimeter data. Results. The ALMA 870 μm continuum emission map reveals an elongated dust structure (~0.15 pc long and ~0.013 pc wide; full width at half maximum) perpendicular to the large-scale molecular outflow detected in the region, and fragmented into a number of cores with masses ~1–10 M_⊙ and sizes ~1600 AU (spatial resolution ~960 AU). The cores appear regularly spaced with a separation of ~0.023 pc. The emission of dense gas tracers such as H^(13)CO^+ or C^(17)O is extended and coincident with the dust elongated structure. The three strongest dust cores show emission of complex organic molecules characteristic of hot cores, with temperatures around 200 K, and relative abundances 0.2–2 × 10^(-8) for CH_3CN and 0.6–5 × 10^(-6) for CH_3OH. The two cores with highest mass (cores A and B) show coherent velocity fields, with gradients almost aligned with the dust elongated structure. Those velocity gradients are consistent with Keplerian disks rotating about central masses of 4–18 M_⊙. Perpendicular to the velocity gradients we have identified a large-scale precessing jet/outflow associated with core B, and hints of an east-west jet/outflow associated with core A. Conclusions. The elongated dust structure in G35.20−0.74 N is fragmented into a number of dense cores that may form high-mass stars. Based on the velocity field of the dense gas, the orientation of the magnetic field, and the regularly spaced fragmentation, we interpret this elongated structure as the densest part of a 1D filament fragmenting and forming high-mass stars.
    Full-text · Article · Jun 2014 · Astronomy and Astrophysics
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: The Stratospheric Observatory for Infrared Astronomy (SOFIA) has recently concluded a set of engineering flights for Observatory performance evaluation. These in-flight opportunities are viewed as a first comprehensive assessment of the Observatory's performance and are used to guide future development activities, as well as to identify additional Observatory upgrades. Pointing stability was evaluated, including the image motion due to rigid-body and flexible-body telescope modes as well as possible aero-optical image motion. We report on recent improvements in pointing stability by using an active mass damper system installed on the telescope. Measurements and characterization of the shear layer and cavity seeing, as well as image quality evaluation as a function of wavelength have also been performed. Additional tests targeted basic Observatory capabilities and requirements, including pointing accuracy, chopper evaluation and imager sensitivity. This paper reports on the data collected during these flights and presents current SOFIA Observatory performance and characterization.
    Full-text · Article · May 2014 · The Astrophysical Journal Supplement Series
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: Observations from optical to centimeter wavelengths have demonstrated that multiple systems of two or more bodies is the norm at all stellar evolutionary stages. Multiple systems are widely agreed to result from the collapse and fragmentation of cloud cores, despite the inhibiting influence of magnetic fields. Surveys of Class 0 protostars with mm interferometers have revealed a very high multiplicity frequency of about 2/3, even though there are observational difficulties in resolving close protobinaries, thus supporting the possibility that all stars could be born in multiple systems. Near-infrared adaptive optics observations of Class I protostars show a lower binary frequency relative to the Class 0 phase, a declining trend that continues through the Class II/III stages to the field population. This loss of companions is a natural consequence of dynamical interplay in small multiple systems, leading to ejection of members. We discuss observational consequences of this dynamical evolution, and its influence on circumstellar disks, and we review the evolution of circumbinary disks and their role in defining binary mass ratios. Special attention is paid to eclipsing PMS binaries, which allow for observational tests of evolutionary models of early stellar evolution. Many stars are born in clusters and small groups, and we discuss how interactions in dense stellar environments can significantly alter the distribution of binary separations through dissolution of wider binaries. The binaries and multiples we find in the field are the survivors of these internal and external destructive processes, and we provide a detailed overview of the multiplicity statistics of the field, which form a boundary condition for all models of binary evolution. Finally we discuss various formation mechanisms for massive binaries, and the properties of massive trapezia.
    Full-text · Article · Mar 2014
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: We aim to characterize the distribution and composition of circumstellar material around young massive stars, and to investigate exactly which physical structures in these objects are probed by long-baseline mid-infrared interferometric observations. We used the two-telescope interferometric instrument MIDI of the Very Large Telescope Interferometer of the European Southern Observatory to observe a sample of 24 intermediate- and high-mass young stellar objects in the N band (8-13 micron). We had successful fringe detections for 20 objects, and present spectrally-resolved correlated fluxes and visibility levels for projected baselines of up to 128 m. We fit the visibilities with geometric models to derive the sizes of the emitting regions, as well as the orientation and elongation of the circumstellar material. Fourteen objects in the sample show the 10 micron silicate feature in absorption in the total and correlated flux spectra. For 13 of these objects, we were able to fit the correlated flux spectra with a simple absorption model, allowing us to constrain the composition and absorptive properties of the circumstellar material. Nearly all of the massive young stellar objects observed show significant deviations from spherical symmetry at mid-infrared wavelengths. In general, the mid-infrared emission can trace both disks and outflows, and in many cases it may be difficult to disentangle these components on the basis of interferometric data alone, because of the sparse spatial frequency coverage normally provided by current long-baseline interferometers. For the majority of the objects in this sample, the absorption occurs on spatial scales larger than those probed by MIDI. Finally, the physical extent of the mid-infrared emission around these sources is correlated with the total luminosity, albeit with significant scatter.
    Preview · Article · Aug 2013 · Astronomy and Astrophysics
  • [Show abstract] [Hide abstract] ABSTRACT: We provide the complete set of reduced, spectrally-resolved MIDI visibilities and differential phases for the 20 objects observed as part of the survey presented in the above publication. These interferometric data are provided in FITS format, and, more specifically, conform to the OIFITS standard (see Pauls et al., 2005PASP..117.1255P). Additionally, besides the standard OIFITS columns, the OI_VIS tables in each of the FITS files contain the columns 'CFLUX' and 'CFLUXERR', which contain the calibrated correlated flux and its estimated uncertainty (measured in Jy). (2 data files).
    No preview · Article · Aug 2013
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: Our general understanding of multiple star and planet formation is primarily based on observations of young multiple systems in low density regions like Tau-Aur and Oph. Since many, if not most, of the stars are born in clusters, observational constraints from young binaries in those environments are fundamental for understanding both the formation of multiple systems and planets in multiple systems throughout the Galaxy. We build upon the largest survey for young binaries in the Orion Nebula Cluster (ONC) which is based on Hubble Space Telescope observations to derive both stellar and circumstellar properties of newborn binary systems in this cluster environment. We present Adaptive Optics spatially-resolved JHKL'-band photometry and K-band R$\sim$\,5000 spectra for a sample of 8 ONC binary systems from this database. We characterize the stellar properties of binary components and obtain a census of protoplanetary disks through K-L' color excess. For a combined sample of ONC binaries including 7 additional systems with NIR spectroscopy from the literature, we derive mass ratio and relative age distributions. We compare the stellar and circumstellar properties of binaries in ONC with those in Tau-Aur and Oph from samples of binaries with stellar properties derived for each component from spectra and/or visual photometry and with a disk census obtained through K-L color excess. The mass ratio distribution of ONC binaries is found to be indistinguishable from that of Tau-Aur and, to some extent, to that of Oph in the separation range 85-560\,AU and for primary mass in the range 0.15 to 0.8\,M$_{\sun}$.A trend toward a lower mass ratio with larger separation is suggested in ONC binaries which is not seen in Tau-Aur binaries.The components of ONC binaries are found to be significantly more coeval than the overall ONC population and as coeval as components of binaries in Tau-Aur and Oph[...]
    Full-text · Article · Jul 2013 · Astronomy and Astrophysics
  • [Show abstract] [Hide abstract] ABSTRACT: Galactic starburst clusters represent the most extreme mode of present-day star formation in the Milky Way, and are ideal laboratories for studies over the entire stellar mass range from less then 0.1 to more than 120 solar masses. We report on the results of our adaptive optics and HST high angular resolution studies comprising both multi-epoch astrometric monitoring of the cluster's internal and external dynamics, and the photometric and spectroscopic characterization of their stellar populations. Among the most surprising results are i) the distinct motions of Galactic Center starburst clusters with respect to the field, ii) the strict coevality of star formation in the spiral arm clusters NGC 3603 YC and Westerlund 1, and iii) the close agreement between dynamical and photometric mass estimates for each of the clusters (indicating that the clusters are dynamically stable and could survive for extended periods of time).
    No preview · Article · Jul 2013
  • Source
    H. Zinnecker
    [Show abstract] [Hide abstract] ABSTRACT: SOFIA, the Stratospheric Observatory for Infrared Astronomy, is a joint project between NASA and the German Aerospace Agency (DLR) to develop and operate a 2.5 m airborne telescope in a highly modified Boeing 747SP aircraft that can fly as high as 45 000 feet (13.7 km). This is above 99.8 % of the precipitable water vapor which blocks much of the mid- and far-infrared radiation from reaching ground-based telescopes. In this review, we briefly discuss the characteristics of the Observatory and present a number of early science highlights obtained with the FORCAST camera in 5-40 micron spectral region and with the GREAT heterodyne spectrometer in the 130-240 micron spectral region. The FORCAST images in Orion show the discovery of a new high-mass protostar (IRc4), while GREAT observations at 1 km s-1 velocity resolution detected velocity-resolved, redshifted ammonia spectra at 1.81 THz in absorption against several strong far-infrared dust continuum sources, clear evidence of substantial protostellar infall onto massive (non-ionizing) protostars. These powerful new data allow us to determine how massive stars form in our Galaxy. Another highlight is the stunning image taken by FORCAST that reveals the transient circumnuclear 1.5 pc radius (dust) ring around our Galactic center, heated by hundreds of massive stars in the young nuclear star cluster. The GREAT heterodyne spectrometer also observed the circumnuclear ring in highly excited CO rotational lines, indicative of emission from warm dense molecular gas with broad velocity structure, perhaps due to local shock heating. GREAT also made superb mapping observations of the [C II] fine structure cooling line at 158 microns, for example in M17-SW molecular cloud-star cluster interface, observations which disprove the simple canonical photodissociation models. The much better baseline stability of the GREAT receivers (compared to Herschel HIFI) allows efficient on-the-fly mapping of extended [C II] emission in our galaxy and also in other nearby spiral galaxies. Of particular note is the GREAT discovery of two new molecules outside the solar system: OD (the deuterated OH hydroxyl radical) as well as mercapto radical SH, both in absorption near 1.4 THz, a frequency gap where Herschel was blind. A special highlight was the 2011 June 23 UT stellar occultation by Pluto using the HIPO high speed photometer and the FDC fast diagnostic camera. This difficult but successful observation, which was both space-critical (within 100 km) and time-critical (within 1 min), proved that SOFIA can be in the right place at the right time, when important transient events occur.
    Preview · Article · Jul 2013 · Astronomische Nachrichten
  • [Show abstract] [Hide abstract] ABSTRACT: Binaries are the most common outcome of star formation. However, the impact of binarity on the evolution of primordial circumstellar disks, which are the birthplaces of planets, is currently only little constrained by theory and observations. Consequently, star and planet formation in binary systems may be significantly different from that in single stars. We present results from the largest coherent study of the evolution of circumstellar disks around the components of binary stars to date. 52 binaries were observed in the Orion Nebula Cluster and Chamaeleon I star-forming regions with near-infrared photometry and spectroscopy. We quantify the presence of circumstellar accretion and dust disks around the individual components of low-mass binary stars with respect to their inferred stellar (e.g. mass, luminosity, Teff), binary (binary separation, mass ratio), and cluster parameters (age, stellar density, presence of strong ionizing sources, star formation history). The results imply significantly reduced disk lifetimes when close, <100AU, stellar companions are present. This effect appears most pronounced for the less massive component of a stellar binary. At the same time, the measured mass accretion rates are of similar magnitude as those of single stars in the same cluster and other star forming regions - a counter-intuitive result because disk masses are typically smaller than around single stars and disk life-times do not appear to be shorter by the same amount. Since the studied individual components' circumstellar disks are potential birth places of planets, these results help to explain the peculiarities of the growing population of planets found in orbit around components of stellar multiples.
    No preview · Article · Jul 2013
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: We have made the first detection of a near-infrared counterpart associated with the disk around Radio Source "I," a massive protostar in the Kleinmann-Low Nebula in Orion using imaging with laser guide star adaptive optics on the Keck II telescope. The infrared emission is evident in images acquired using L' (3.8 microns) and Ms (4.7 microns) filters and is not detectable at K' (2.1 microns). The observed morphology strongly suggests that we are seeing some combination of scattered and thermal light emanating from the disk. The disk is also manifest in the L'/Ms flux ratio image. We interpret the near-infrared emission as the illuminated surface of a nearly edge-on disk, oriented so that only the northern face is visible; the opposite surface remains hidden by the disk. We do not see infrared radiation associated directly with the star proposed to be associated with Source "I." The data also suggest that there is a cavity above and below the disk that is oriented perpendicular to the disk, and is sculpted by the known, strong outflow from the inner disk of Source I. We compare our data to models of a protostar with a surrounding disk, envelope, and wind-blown cavity in order to elucidate the nature of the disk around Radio Source I.
    Full-text · Article · Apr 2013 · The Astrophysical Journal
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: We report on ALMA observations of continuum and molecular line emission with 0.4" resolution towards the high-mass star forming region G35.20-0.74 N. Two dense cores are detected in typical hot-core tracers, such as CH3CN, which reveal velocity gradients. In one of these cores, the velocity field can be fitted with an almost edge-on Keplerian disk rotating about a central mass of 18 Msun. This finding is consistent with the results of a recent study of the CO first overtone bandhead emission at 2.3mum towards G35.20-0.74 N. The disk radius and mass are >2500 au and 3 Msun. To reconcile the observed bolometric luminosity (3x10^4 Lsun) with the estimated stellar mass of 18 Msun, we propose that the latter is the total mass of a binary system.
    Preview · Article · Apr 2013 · Astronomy and Astrophysics
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: The characterization of multiple stellar systems is an important ingredient for testing current star formation models. Stars are more often found in multiple systems, the more massive they are. A complete knowledge of the multiplicity of high-mass stars over the full range of orbit separations is thus essential to understand their still debated formation process. Observations of the Orion Nebula Cluster can help to answer the question about the origin and evolution of multiple stars. Earlier studies provide a good knowledge about the multiplicity of the stars at very small (spectroscopic) and large separations (AO, speckle) and thus make the ONC a good target for such a project. We used the NIR interferometric instrument AMBER at VLTI to observe a sample of bright stars in the ONC. We complement our data set by archival NACO observations of \theta 1 Ori A to obtain more information about the orbit of the close visual companion. Our observations resolve the known multiple systems \theta 1 Ori C and \theta 1 Ori A and provide new orbit points, which confirm the predicted orbit and the determined stellar parameters for \theta 1 Ori C. Combining AMBER and NACO data for \theta 1 Ori A we were able to follow the motion of the companion from 2003 to 2011. We furthermore find hints for a companion around \theta 1 Ori D and a previously unknown companion to NU Ori. With a probability of ~90% we can exclude further companions with masses of > 3 Msun around our sample stars for separations between ~2 mas and ~110 mas. We conclude that the companion around \theta 1 Ori A is most likely physically related to the primary star. The newly discovered possible companions further increase the multiplicity in the ONC. For our sample of two O and three B-type stars we find on average 2.5 known companions per primary, which is around five times more than for low-mass stars.
    Full-text · Article · Jan 2013 · Astronomy and Astrophysics
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: The Carina Nebula represents one of the largest and most active star forming regions known in our Galaxy with numerous very massive stars.Our recently obtained Herschel PACS & SPIRE far-infrared maps cover the full area (about 8.7 deg^2) of the Carina Nebula complex and reveal the population of deeply embedded young stellar objects, most of which are not yet visible in the mid- or near-infrared.We study the properties of the 642 objects that are independently detected as point-like sources in at least two of the five Herschel bands.For those objects that can be identified with apparently single Spitzer counterparts, we use radiative transfer models to derive information about the basic stellar and circumstellar parameters.We find that about 75% of the Herschel-detected YSOs are Class 0 protostars.The luminosities of the Herschel-detected YSOs with SED fits are restricted to values of <=5400 Lsun, their masses (estimated from the radiative transfer modeling) range from about 1 Msun to 10 Msun.Taking the observational limits into account and extrapolating the observed number of Herschel-detected protostars over the IMF suggest that the star formation rate of the CNC is about 0.017 Msun/yr.The spatial distribution of the Herschel YSO candidates is highly inhomogeneous and does not follow the distribution of cloud mass.Most Herschel YSO candidates are found at the irradiated edges of clouds and pillars.This provides support to the picture that the formation of this latest stellar generation is triggered by the advancing ionization fronts.The currently ongoing star formation process forms only low-mass and intermediate-mass stars, but no massive stars.The far-infrared fluxes of the famous object EtaCar are about a factor of two lower than expected from observations with the ISO obtained 15 years ago; this may be due to dynamical changes in the circumstellar dust in the Homunculus Nebula.
    Preview · Article · Nov 2012 · Astronomy and Astrophysics
  • [Show abstract] [Hide abstract] ABSTRACT: The Carina Nebula complex was observed by the Herschel satellite on December 26th, 2010. (4 data files).
    No preview · Article · Nov 2012
  • [Show abstract] [Hide abstract] ABSTRACT: SOFIA, the Stratospheric Observatory for Infrared Astronomy, is an airborne observatory with a 2.7-m telescope that is under development by NASA and the German Aerospace Center DLR. From late 2010 and through the end of 2011, SOFIA conducted a series of science demonstration flights, Early Science, using FORCAST (the Faint Object InfraRed Camera for the SOFIA Telescope), HIPO (the High-speed Imaging Photometer for Occultations), and GREAT (the German REceiver for Astronomy at Terahertz frequencies). Flying at altitudes as high as 13.7 km (45,000 ft), SOFIA operates above more than 99.8% of the water vapor in the Earth’s atmosphere, opening up most of the far-infrared and sub-millimeter parts of the spectrum. During Early Science, 30 science missions were flown with results in solar system astronomy, star formation, the interstellar medium, the Galactic Center, and extragalactic studies. Many of these investigations were conducted by the first group of SOFIA General Investigators, demonstrating the operation of SOFIA as a facility for the astronomical community. This paper presents some recent highlights from Early Science.
    No preview · Article · Sep 2012 · Proceedings of SPIE - The International Society for Optical Engineering
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: This study aims to determine the impact of stellar binary companions on the lifetime and evolution of circumstellar disks in the Chamaeleon I (Cha I) star-forming region by measuring the frequency and strength of accretion and circumstellar dust signatures around the individual components of T Tauri binary stars. We used high-angular resolution adaptive optics JHKL'-band photometry and 1.5-2.5mu spectroscopy of 19 visual binary and 7 triple stars in Cha I - including one newly discovered tertiary component - with separations between ~25 and ~1000au. The data allowed us to infer stellar component masses and ages and, from the detection of near-infrared excess emission and the strength of Brackett-gamma emission, the presence of ongoing accretion and hot circumstellar dust of the individual stellar component of each binary. Of all the stellar components in close binaries with separations of 25-100au, 10(+15-5)% show signs of accretion. This is less than half of the accretor fraction found in wider binaries, which itself appears significantly reduced (~44%) compared with previous measurements of single stars in Cha I. Hot dust was found around 50(+30-15)% of the target components, a value that is indistinguishable from that of Cha I single stars. Only the closest binaries (<25au) were inferred to have a significantly reduced fraction (<~25%) of components that harbor hot dust. Accretors were exclusively found in binary systems with unequal component masses M_secondary/M_primary < 0.8, implying that the detected accelerated disk dispersal is a function of mass-ratio. This agrees with the finding that only one accreting secondary star was found, which is also the weakest accretor in the sample. The results imply that disk dispersal is more accelerated the stronger the dynamical disk truncation, i.e., the smaller the inferred radius of the disk. (abridged)
    Full-text · Article · Jun 2012 · Astronomy and Astrophysics

Publication Stats

5k Citations
722.31 Total Impact Points


  • 2012-2014
    • NASA
      Вашингтон, West Virginia, United States
  • 2011-2013
    • Universität Stuttgart
      Stuttgart, Baden-Württemberg, Germany
    • Fisk University
      • Department of Physics
      Nashville, Tennessee, United States
    • University of Toronto
      • Department of Astronomy and Astrophysics
      Toronto, Ontario, Canada
  • 2007
    • University of Illinois, Urbana-Champaign
      Urbana, Illinois, United States
  • 2006
    • University of Florence
      Florens, Tuscany, Italy
    • Universität Potsdam
      Potsdam, Brandenburg, Germany
  • 2005
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 2000-2005
    • Max Planck Institute for Radio Astronomy
      Bonn, North Rhine-Westphalia, Germany
    • University of Wisconsin–Madison
      Madison, Wisconsin, United States
    • Friedrich-Schiller-University Jena
      Jena, Thuringia, Germany
  • 2003
    • University of California, Berkeley
      • Department of Astronomy
      Berkeley, California, United States
  • 2001-2003
    • Cornell University
      • Department of Astronomy
      Итак, New York, United States
    • National Radio Astronomy Observatory
      Charlottesville, Virginia, United States
    • University of Lisbon
      Lisboa, Lisbon, Portugal
  • 2001-2002
    • Russian Academy of Sciences
      • Institute of Astronomy
      Moskva, Moscow, Russia
  • 1997
    • Honolulu University
      Honolulu, Hawaii, United States
  • 1995-1997
    • Max Planck Institute for Extraterrestrial Physics
      Arching, Bavaria, Germany
  • 1990-1997
    • University of Wuerzburg
      Würzburg, Bavaria, Germany
    • Max Planck Institute for Astronomy
      Heidelburg, Baden-Württemberg, Germany
  • 1994
    • University of Leicester
      Leiscester, England, United Kingdom
  • 1991
    • University of Santiago, Chile
      CiudadSantiago, Santiago Metropolitan, Chile
  • 1989
    • University of Wollongong
      City of Greater Wollongong, New South Wales, Australia
    • Dublin Institute for Advanced Studies
      Dublin, Leinster, Ireland