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E T Young - One of the best experts on this subject based on the ideXlab platform.

  • Outflows from the high-mass protostars NGC 7538 IRS1/2 observed with bispectrum Speckle Interferometry. Signatures of flow precession
    'EDP Sciences', 2018
    Co-Authors: Kraus S, Balega Y, Elitzur M, Hofmann K-h, Preibisch T, Rosen A, Schertl D, Weigelt G, E T Young
    Abstract:

    This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this record.Context. NGC 7538 IRS1 is a high-mass (30 M) protostar with a CO outflow, an associated ultracompact H region, and a linear methanol maser structure, which might trace a Keplerian-rotating circumstellar disk. The directions of the various associated axes are misaligned with each other. Aims. We investigate the near-infrared morphology of the source to clarify the relations among the various axes. Methods. K -band bispectrum Speckle Interferometry was performed at two 6-meter-class telescopes – the BTA 6 m telescope and the 6.5 m MMT. Complementary IRAC images from the Spitzer Space Telescope Archive were used to relate the structures detected with the outflow at larger scales. Results. High-dynamic range images show fan-shaped outflow structure in which we detect 18 stars and several blobs of diffuse emission. We interpret the misalignment of various outflow axes in the context of a disk precession model, including numerical hydrodynamic simulations of the molecular emission. The precession period is ∼280 years and its half-opening angle is ∼40◦. A possible triggering mechanism is non-coplanar tidal interaction of an (undiscovered) close companion with the circumbinary protostellar disk. Our observations resolve the nearby massive protostar NGC 7538 IRS2 as a close binary with separation of 195 mas. We find indications for shock interaction between the outflow activities in IRS1 and IRS2. Finally, we find prominent sites of star formation at the interface between two bubble-like structures in NGC 7538, suggestive of a triggered star formation scenario. Conclusions. Indications of outflow precession have been discovered to date in a number of massive protostars, all with large precession angles (∼20–45◦). This might explain the difference between the outflow widths in low- and high-mass stars and add support to a common collimation mechanism

  • outflows from the high mass protostars ngc 7538 irs1 2 observed with bispectrum Speckle Interferometry signatures of flow precession
    Astronomy and Astrophysics, 2006
    Co-Authors: Stefan Kraus, Yu Yu Balega, Moshe Elitzur, Karlheinz Hofmann, Th Preibisch, A Rosen, D Schertl, G Weigelt, E T Young
    Abstract:

    Context. NGC 7538 IRS1 is a high-mass (30 M⊙) protostar with a CO outflow, an associated ultracompact H II region, and a linear methanol maser structure, which might trace a Keplerian-rotating circumstellar disk. The directions of the various associated axes are misaligned with each other. Aims. We investigate the near-infrared morphology of the source to clarify the relations among the various axes. Methods. K’ -band bispectrum Speckle Interferometry was performed at two 6-meter-class telescopes—the BTA 6m telescope and the 6.5m MMT. Complementary IRAC images from theSpitzer Space Telescope Archive were used to relate the structures detected with the outflow at larger scales. Results. High-dynamic range images show fan-shaped outflow structur e in which we detect 18 stars and several blobs of diffuse emission. We interpret the misalignment of various outflow axes in the con text of a disk precession model, including numerical hydrodynamic simulations of the molecular emission. The precession period is∼ 280 years and its half-opening angle is∼ 40 ◦ . A possible triggering mechanism is noncoplanar tidal interaction of an (undiscovered) close companion with the circumbinary protostellar disk. Our observations resolve the nearby massive protostar NGC 7538 IRS2 as a close binary with separation of 195 mas. We find indications for shock interaction bet ween the outflow activities in IRS1 and IRS2. Finally, we find prominent sites of star formation at the interface between two bubble-like structures in NGC 7538, suggestive of a triggered star formation scenario. Conclusions. Indications of outflow precession have been discovered to da te in a number of massive protostars, all with large precessi on angles (∼ 20‐45 ◦ ). This might explain the difference between the outflow widt hs in low- and high-mass stars and add support to a common collimation mechanism.

  • outflows from the high mass protostars ngc 7538 irs1 2 observed with bispectrum Speckle Interferometry signatures of flow precession
    arXiv: Astrophysics, 2006
    Co-Authors: Stefan Kraus, Yu Yu Balega, Moshe Elitzur, Karlheinz Hofmann, Th Preibisch, A Rosen, D Schertl, G Weigelt, E T Young
    Abstract:

    NGC 7538 IRS1 is a high-mass (approx. 30 M_sun) protostar with a CO outflow, an associated UCHII region, and a linear methanol maser structure, which might trace a Keplerian-rotating circumstellar disk. The directions of the various associated axes are misaligned with each other. We investigate the near-infrared morphology of the source to clarify the relations among the various axes. K'-band bispectrum Speckle Interferometry was performed at two 6-meter-class telescopes -- the BTA 6m telescope and the 6.5m MMT. Complementary IRAC images from the Spitzer Space Telescope Archive were used to relate the structures detected with the outflow at larger scales. High-dynamic range images show fan-shaped outflow structure in which we detect 18 stars and several blobs of diffuse emission. We interpret the misalignment of various outflow axes in the context of a disk precession model, including numerical hydrodynamic simulations of the molecular emission. The precession period is approx. 280 years and its half-opening angle is 40 degrees. A possible triggering mechanism is non-coplanar tidal interaction of an (undiscovered) close companion with the circumbinary protostellar disk. Our observations resolve the nearby massive protostar NGC 7538 IRS2 as a close binary with separation of 195 mas. We find indications for shock interaction between the outflow activities in IRS1 and IRS2. Indications of outflow precession have been discovered to date in a number of massive protostars, all with large precession angles 20--45 degrees. This might explain the difference between the outflow widths in low- and high-mass stars and add support to a common collimation mechanism.

Stefan Kraus - One of the best experts on this subject based on the ideXlab platform.

  • outflows from the high mass protostars ngc 7538 irs1 2 observed with bispectrum Speckle Interferometry signatures of flow precession
    Astronomy and Astrophysics, 2006
    Co-Authors: Stefan Kraus, Yu Yu Balega, Moshe Elitzur, Karlheinz Hofmann, Th Preibisch, A Rosen, D Schertl, G Weigelt, E T Young
    Abstract:

    Context. NGC 7538 IRS1 is a high-mass (30 M⊙) protostar with a CO outflow, an associated ultracompact H II region, and a linear methanol maser structure, which might trace a Keplerian-rotating circumstellar disk. The directions of the various associated axes are misaligned with each other. Aims. We investigate the near-infrared morphology of the source to clarify the relations among the various axes. Methods. K’ -band bispectrum Speckle Interferometry was performed at two 6-meter-class telescopes—the BTA 6m telescope and the 6.5m MMT. Complementary IRAC images from theSpitzer Space Telescope Archive were used to relate the structures detected with the outflow at larger scales. Results. High-dynamic range images show fan-shaped outflow structur e in which we detect 18 stars and several blobs of diffuse emission. We interpret the misalignment of various outflow axes in the con text of a disk precession model, including numerical hydrodynamic simulations of the molecular emission. The precession period is∼ 280 years and its half-opening angle is∼ 40 ◦ . A possible triggering mechanism is noncoplanar tidal interaction of an (undiscovered) close companion with the circumbinary protostellar disk. Our observations resolve the nearby massive protostar NGC 7538 IRS2 as a close binary with separation of 195 mas. We find indications for shock interaction bet ween the outflow activities in IRS1 and IRS2. Finally, we find prominent sites of star formation at the interface between two bubble-like structures in NGC 7538, suggestive of a triggered star formation scenario. Conclusions. Indications of outflow precession have been discovered to da te in a number of massive protostars, all with large precessi on angles (∼ 20‐45 ◦ ). This might explain the difference between the outflow widt hs in low- and high-mass stars and add support to a common collimation mechanism.

  • outflows from the high mass protostars ngc 7538 irs1 2 observed with bispectrum Speckle Interferometry signatures of flow precession
    arXiv: Astrophysics, 2006
    Co-Authors: Stefan Kraus, Yu Yu Balega, Moshe Elitzur, Karlheinz Hofmann, Th Preibisch, A Rosen, D Schertl, G Weigelt, E T Young
    Abstract:

    NGC 7538 IRS1 is a high-mass (approx. 30 M_sun) protostar with a CO outflow, an associated UCHII region, and a linear methanol maser structure, which might trace a Keplerian-rotating circumstellar disk. The directions of the various associated axes are misaligned with each other. We investigate the near-infrared morphology of the source to clarify the relations among the various axes. K'-band bispectrum Speckle Interferometry was performed at two 6-meter-class telescopes -- the BTA 6m telescope and the 6.5m MMT. Complementary IRAC images from the Spitzer Space Telescope Archive were used to relate the structures detected with the outflow at larger scales. High-dynamic range images show fan-shaped outflow structure in which we detect 18 stars and several blobs of diffuse emission. We interpret the misalignment of various outflow axes in the context of a disk precession model, including numerical hydrodynamic simulations of the molecular emission. The precession period is approx. 280 years and its half-opening angle is 40 degrees. A possible triggering mechanism is non-coplanar tidal interaction of an (undiscovered) close companion with the circumbinary protostellar disk. Our observations resolve the nearby massive protostar NGC 7538 IRS2 as a close binary with separation of 195 mas. We find indications for shock interaction between the outflow activities in IRS1 and IRS2. Indications of outflow precession have been discovered to date in a number of massive protostars, all with large precession angles 20--45 degrees. This might explain the difference between the outflow widths in low- and high-mass stars and add support to a common collimation mechanism.

Michael J Ireland - One of the best experts on this subject based on the ideXlab platform.

  • validation of the exoplanet kepler 21b using pavo chara long baseline Interferometry
    Monthly Notices of the Royal Astronomical Society: Letters, 2012
    Co-Authors: A Merand, Vicente Maestro, Steve B Howell, Michael J Ireland, T R Bedding, Daniel Huber, P G Tuthill
    Abstract:

    We present long-baseline Interferometry of theKepler exoplanet host star HD 179070 (Kepler21) using the Precision Astronomical Visible Observations (PAVO) beam combiner at the Center for High Angular Resolution Astronomy (CHARA) Array. The visibility data are consistent with a single star and exclude stellar companions at separations ∼1–1000 mas (∼0.1–113 au) and contrasts <3.5 mag. This result supports the validation of the 1.6 R⊕ exoplanet Kepler-21b by Howell et al. and complements the constraints set by adaptive optics imaging, Speckle Interferometry and radial-velocity observations to rule out false positives due to stellar companions. We conclude that long-baseline Interferometry has strong potential to validate transiting extrasolar planets, particularly for future projects aimed at brighter stars and for host stars where radial-velocity follow-up is not available.

  • validation of the exoplanet kepler 21b using pavo chara long baseline Interferometry
    arXiv: Solar and Stellar Astrophysics, 2012
    Co-Authors: A Merand, Vicente Maestro, Steve B Howell, Michael J Ireland, T R Bedding, Daniel Huber, P G Tuthill
    Abstract:

    We present long-baseline Interferometry of the Kepler exoplanet host star HD179070 (Kepler-21) using the PAVO beam combiner at the CHARA Array. The visibility data are consistent with a single star and exclude stellar companions at separations ~1-1000 mas (~ 0.1-113 AU) and contrasts < 3.5 magnitudes. This result supports the validation of the 1.6 R_{earth} exoplanet Kepler-21b by Howell et al. (2012) and complements the constraints set by adaptive optics imaging, Speckle Interferometry, and radial velocity observations to rule out false-positives due to stellar companions. We conclude that long-baseline Interferometry has strong potential to validate transiting extrasolar planets, particularly for future projects aimed at brighter stars and for host stars where radial velocity follow-up is not available.

Daniel Huber - One of the best experts on this subject based on the ideXlab platform.

  • validation of the exoplanet kepler 21b using pavo chara long baseline Interferometry
    Monthly Notices of the Royal Astronomical Society: Letters, 2012
    Co-Authors: A Merand, Vicente Maestro, Steve B Howell, Michael J Ireland, T R Bedding, Daniel Huber, P G Tuthill
    Abstract:

    We present long-baseline Interferometry of theKepler exoplanet host star HD 179070 (Kepler21) using the Precision Astronomical Visible Observations (PAVO) beam combiner at the Center for High Angular Resolution Astronomy (CHARA) Array. The visibility data are consistent with a single star and exclude stellar companions at separations ∼1–1000 mas (∼0.1–113 au) and contrasts <3.5 mag. This result supports the validation of the 1.6 R⊕ exoplanet Kepler-21b by Howell et al. and complements the constraints set by adaptive optics imaging, Speckle Interferometry and radial-velocity observations to rule out false positives due to stellar companions. We conclude that long-baseline Interferometry has strong potential to validate transiting extrasolar planets, particularly for future projects aimed at brighter stars and for host stars where radial-velocity follow-up is not available.

  • validation of the exoplanet kepler 21b using pavo chara long baseline Interferometry
    arXiv: Solar and Stellar Astrophysics, 2012
    Co-Authors: A Merand, Vicente Maestro, Steve B Howell, Michael J Ireland, T R Bedding, Daniel Huber, P G Tuthill
    Abstract:

    We present long-baseline Interferometry of the Kepler exoplanet host star HD179070 (Kepler-21) using the PAVO beam combiner at the CHARA Array. The visibility data are consistent with a single star and exclude stellar companions at separations ~1-1000 mas (~ 0.1-113 AU) and contrasts < 3.5 magnitudes. This result supports the validation of the 1.6 R_{earth} exoplanet Kepler-21b by Howell et al. (2012) and complements the constraints set by adaptive optics imaging, Speckle Interferometry, and radial velocity observations to rule out false-positives due to stellar companions. We conclude that long-baseline Interferometry has strong potential to validate transiting extrasolar planets, particularly for future projects aimed at brighter stars and for host stars where radial velocity follow-up is not available.

Yu Yu Balega - One of the best experts on this subject based on the ideXlab platform.

  • A new spectroscopic and interferometric study of the young stellar object V645 Cygni
    2020
    Co-Authors: A S Miroshnichenko, Yu Yu Balega, D Schertl, G Weigelt, K.-h Hofmann, S Kraus, N Manset, L Albert, V G Klochkova, R J Rudy
    Abstract:

    Abstract: Aims. We present the results of high-resolution optical spectroscopy, low-resolution near-IR spectroscopy and near-infrared Speckle Interferometry of the massive young stellar object candidate V645 Cyg, acquired to refine its fundamental parameters and the proper-ties of its circumstellar envelope. Methods. Speckle Interferometry in the H-and K-bands and an optical spectrum in the range 5200-6680 Å with a spectral resolving power of R = 60 000 were obtained at the 6 m telescope of the Russian Academy of Sciences. Another optical spectrum in the range 4300-10 500 Å with R = 79 000 was obtained at the 3.6 m CFHT. Low-resolution spectra in the ranges 0.46-1.4μm and 1.4-2.5μm with R ~ 800 and ~700, respectively, were obtained at the 3 m Shane telescope of the Lick Observatory. Results. Using a novel kinematical method based on the non-linear modeling of the neutral hydrogen density profile in the direction toward the object, we propose a distance of D = 4.2 ± 0.2 kpc. We also suggest a revised estimate of the star's effective temperature, T eff ~25 000 K. We resolved the object in both H-and K-bands. Using a two-component ring fit, we derived a compact component size of 14 mas and 12 mas in the H-and K-band, respectively, which correspond to 29 and 26 AU at the revised distance. Analysis of our own and previously published data indicates a ~2 mag decrease in the near-infrared brightness of V645 Cyg at the beginning of the 1980's. At the same time, the cometary nebular condensation N1 appears to fade in this wavelength range with respect to the N0 object, representing the star with a nearly pole-on optically-thick disk and an optically-thin envelope. Conclusions. We conclude that V645 Cyg is a young, massive, main-sequence star, which recently emerged from its cocoon and has already experienced its protostellar accretion stage. The presence of accretion is not necessary to account for the high observed luminosity of (2-6) x 10 4 M⨀ yr-1. The receding part of a strong, mostly uniform outflow with a terminal velocity of -800 km s-1 is only blocked from view far from the star, where forbidden lines form. The near-infrared size of the source is consistent with the dust sublimation distance close to this hot and luminous star and is the largest among all young stellar objects observed interferometrically to-date

  • outflows from the high mass protostars ngc 7538 irs1 2 observed with bispectrum Speckle Interferometry signatures of flow precession
    Astronomy and Astrophysics, 2006
    Co-Authors: Stefan Kraus, Yu Yu Balega, Moshe Elitzur, Karlheinz Hofmann, Th Preibisch, A Rosen, D Schertl, G Weigelt, E T Young
    Abstract:

    Context. NGC 7538 IRS1 is a high-mass (30 M⊙) protostar with a CO outflow, an associated ultracompact H II region, and a linear methanol maser structure, which might trace a Keplerian-rotating circumstellar disk. The directions of the various associated axes are misaligned with each other. Aims. We investigate the near-infrared morphology of the source to clarify the relations among the various axes. Methods. K’ -band bispectrum Speckle Interferometry was performed at two 6-meter-class telescopes—the BTA 6m telescope and the 6.5m MMT. Complementary IRAC images from theSpitzer Space Telescope Archive were used to relate the structures detected with the outflow at larger scales. Results. High-dynamic range images show fan-shaped outflow structur e in which we detect 18 stars and several blobs of diffuse emission. We interpret the misalignment of various outflow axes in the con text of a disk precession model, including numerical hydrodynamic simulations of the molecular emission. The precession period is∼ 280 years and its half-opening angle is∼ 40 ◦ . A possible triggering mechanism is noncoplanar tidal interaction of an (undiscovered) close companion with the circumbinary protostellar disk. Our observations resolve the nearby massive protostar NGC 7538 IRS2 as a close binary with separation of 195 mas. We find indications for shock interaction bet ween the outflow activities in IRS1 and IRS2. Finally, we find prominent sites of star formation at the interface between two bubble-like structures in NGC 7538, suggestive of a triggered star formation scenario. Conclusions. Indications of outflow precession have been discovered to da te in a number of massive protostars, all with large precessi on angles (∼ 20‐45 ◦ ). This might explain the difference between the outflow widt hs in low- and high-mass stars and add support to a common collimation mechanism.

  • outflows from the high mass protostars ngc 7538 irs1 2 observed with bispectrum Speckle Interferometry signatures of flow precession
    arXiv: Astrophysics, 2006
    Co-Authors: Stefan Kraus, Yu Yu Balega, Moshe Elitzur, Karlheinz Hofmann, Th Preibisch, A Rosen, D Schertl, G Weigelt, E T Young
    Abstract:

    NGC 7538 IRS1 is a high-mass (approx. 30 M_sun) protostar with a CO outflow, an associated UCHII region, and a linear methanol maser structure, which might trace a Keplerian-rotating circumstellar disk. The directions of the various associated axes are misaligned with each other. We investigate the near-infrared morphology of the source to clarify the relations among the various axes. K'-band bispectrum Speckle Interferometry was performed at two 6-meter-class telescopes -- the BTA 6m telescope and the 6.5m MMT. Complementary IRAC images from the Spitzer Space Telescope Archive were used to relate the structures detected with the outflow at larger scales. High-dynamic range images show fan-shaped outflow structure in which we detect 18 stars and several blobs of diffuse emission. We interpret the misalignment of various outflow axes in the context of a disk precession model, including numerical hydrodynamic simulations of the molecular emission. The precession period is approx. 280 years and its half-opening angle is 40 degrees. A possible triggering mechanism is non-coplanar tidal interaction of an (undiscovered) close companion with the circumbinary protostellar disk. Our observations resolve the nearby massive protostar NGC 7538 IRS2 as a close binary with separation of 195 mas. We find indications for shock interaction between the outflow activities in IRS1 and IRS2. Indications of outflow precession have been discovered to date in a number of massive protostars, all with large precession angles 20--45 degrees. This might explain the difference between the outflow widths in low- and high-mass stars and add support to a common collimation mechanism.