The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
Xiaowei Duan - One of the best experts on this subject based on the ideXlab platform.
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possible evidence of Hydrogen Emission in the first overtone and multimode rr lyrae variables
The Astrophysical Journal, 2021Co-Authors: Xiaowei Duan, Xiaodian Chen, Licai Deng, Fan Yang, Chao Liu, Anupam Bhardwaj, Huawei ZhangAbstract:The nature of shock waves in non-fundamental mode RR Lyrae stars remains a mystery because of limited spectroscopic observations. We apply a pattern recognition algorithm on spectroscopic data from SDSS and LAMOST and report the first evidence of Hydrogen Emission in first-overtone and multi-mode RR Lyrae stars showing the "first apparition", which is the most prominent observational characteristic of shock in RR Lyrae variables. We find ten RRc stars in SDSS, ten RRc stars in LAMOST, and three RRd stars in LAMOST that show blueshifted Balmer Emissions. The Emission features possibly indicate the existence of shock waves. We calculate the radial velocities of the Emission lines, which are related to the physical conditions occurring in the radiative zone of shock waves. Using photometric observations from ZTF, we present a detailed light curve analysis for the frequency components in one of our RRd stars with Hydrogen Emission, RRdl3, for possible modulations. With the enormous volume of upcoming spectral observations of variable stars, our study raises the possibility of connecting the unexplained Blazhko effect to shock waves in non-fundamental mode RR Lyrae stars.
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Possible evidence of Hydrogen Emission in the first-overtone and multi-mode RR Lyrae variables
The Astrophysical Journal, 2021Co-Authors: Xiaowei Duan, Xiaodian Chen, Licai Deng, Fan Yang, Chao Liu, Anupam Bhardwaj, Huawei ZhangAbstract:The nature of shock waves in non-fundamental mode RR Lyrae stars remains a mystery because of limited spectroscopic observations. We apply a pattern recognition algorithm on spectroscopic data from SDSS and LAMOST and report the first evidence of Hydrogen Emission in first-overtone and multi-mode RR Lyrae stars showing the "first apparition", which is the most prominent observational characteristic of shock in RR Lyrae variables. We find ten RRc stars in SDSS, ten RRc stars in LAMOST, and three RRd stars in LAMOST that show blueshifted Balmer Emissions. The Emission features possibly indicate the existence of shock waves. We calculate the radial velocities of the Emission lines, which are related to the physical conditions occurring in the radiative zone of shock waves. Using photometric observations from ZTF, we present a detailed light curve analysis for the frequency components in one of our RRd stars with Hydrogen Emission, RRdl3, for possible modulations. With the enormous volume of upcoming spectral observations of variable stars, our study raises the possibility of connecting the unexplained Blazhko effect to shock waves in non-fundamental mode RR Lyrae stars.
Huawei Zhang - One of the best experts on this subject based on the ideXlab platform.
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possible evidence of Hydrogen Emission in the first overtone and multimode rr lyrae variables
The Astrophysical Journal, 2021Co-Authors: Xiaowei Duan, Xiaodian Chen, Licai Deng, Fan Yang, Chao Liu, Anupam Bhardwaj, Huawei ZhangAbstract:The nature of shock waves in non-fundamental mode RR Lyrae stars remains a mystery because of limited spectroscopic observations. We apply a pattern recognition algorithm on spectroscopic data from SDSS and LAMOST and report the first evidence of Hydrogen Emission in first-overtone and multi-mode RR Lyrae stars showing the "first apparition", which is the most prominent observational characteristic of shock in RR Lyrae variables. We find ten RRc stars in SDSS, ten RRc stars in LAMOST, and three RRd stars in LAMOST that show blueshifted Balmer Emissions. The Emission features possibly indicate the existence of shock waves. We calculate the radial velocities of the Emission lines, which are related to the physical conditions occurring in the radiative zone of shock waves. Using photometric observations from ZTF, we present a detailed light curve analysis for the frequency components in one of our RRd stars with Hydrogen Emission, RRdl3, for possible modulations. With the enormous volume of upcoming spectral observations of variable stars, our study raises the possibility of connecting the unexplained Blazhko effect to shock waves in non-fundamental mode RR Lyrae stars.
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Possible evidence of Hydrogen Emission in the first-overtone and multi-mode RR Lyrae variables
The Astrophysical Journal, 2021Co-Authors: Xiaowei Duan, Xiaodian Chen, Licai Deng, Fan Yang, Chao Liu, Anupam Bhardwaj, Huawei ZhangAbstract:The nature of shock waves in non-fundamental mode RR Lyrae stars remains a mystery because of limited spectroscopic observations. We apply a pattern recognition algorithm on spectroscopic data from SDSS and LAMOST and report the first evidence of Hydrogen Emission in first-overtone and multi-mode RR Lyrae stars showing the "first apparition", which is the most prominent observational characteristic of shock in RR Lyrae variables. We find ten RRc stars in SDSS, ten RRc stars in LAMOST, and three RRd stars in LAMOST that show blueshifted Balmer Emissions. The Emission features possibly indicate the existence of shock waves. We calculate the radial velocities of the Emission lines, which are related to the physical conditions occurring in the radiative zone of shock waves. Using photometric observations from ZTF, we present a detailed light curve analysis for the frequency components in one of our RRd stars with Hydrogen Emission, RRdl3, for possible modulations. With the enormous volume of upcoming spectral observations of variable stars, our study raises the possibility of connecting the unexplained Blazhko effect to shock waves in non-fundamental mode RR Lyrae stars.
Daniel Nadeau - One of the best experts on this subject based on the ideXlab platform.
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Molecular Hydrogen Emission in the Wolf-Rayet Nebula NGC 2359
The Astronomical Journal, 1998Co-Authors: Nicole St-louis, René Doyon, François Chagnon, Daniel NadeauAbstract:We report the first direct detection of molecular Hydrogen Emission in the interstellar medium in the vicinity of a Wolf-Rayet (W-R) star. The spatial distribution of the excited molecular gas associated with NGC 2359 is filamentary and lies mainly on the border of the ionized gas, as traced by optical Emission lines such as Hα or [O III] λ5007. The typical 1–0 S(1) H2 brightness in the filaments is 5 × 10-5 ergs s-1 cm-2 sr-1 and the total 1–0 S(1) H2 luminosity detected is ~4 L☉. The detected line flux in the 1–0 S(1) transition of H2 at λ = 2.122 μm could equally be explained by shock excitation or by fluorescence from the strong ultraviolet flux of the W-R star. The morphological distribution of the H2 filaments is not inconsistent with either mode of excitation. Although the ubiquity of this phenomenon needs to be confirmed, the relatively high level of 1–0 S(1) H2 Emission detected in this W-R nebula indicates that hot stars could potentially contribute a significant fraction of the total H2 Emission of young starburst galaxies.
Xiaodian Chen - One of the best experts on this subject based on the ideXlab platform.
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possible evidence of Hydrogen Emission in the first overtone and multimode rr lyrae variables
The Astrophysical Journal, 2021Co-Authors: Xiaowei Duan, Xiaodian Chen, Licai Deng, Fan Yang, Chao Liu, Anupam Bhardwaj, Huawei ZhangAbstract:The nature of shock waves in non-fundamental mode RR Lyrae stars remains a mystery because of limited spectroscopic observations. We apply a pattern recognition algorithm on spectroscopic data from SDSS and LAMOST and report the first evidence of Hydrogen Emission in first-overtone and multi-mode RR Lyrae stars showing the "first apparition", which is the most prominent observational characteristic of shock in RR Lyrae variables. We find ten RRc stars in SDSS, ten RRc stars in LAMOST, and three RRd stars in LAMOST that show blueshifted Balmer Emissions. The Emission features possibly indicate the existence of shock waves. We calculate the radial velocities of the Emission lines, which are related to the physical conditions occurring in the radiative zone of shock waves. Using photometric observations from ZTF, we present a detailed light curve analysis for the frequency components in one of our RRd stars with Hydrogen Emission, RRdl3, for possible modulations. With the enormous volume of upcoming spectral observations of variable stars, our study raises the possibility of connecting the unexplained Blazhko effect to shock waves in non-fundamental mode RR Lyrae stars.
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Possible evidence of Hydrogen Emission in the first-overtone and multi-mode RR Lyrae variables
The Astrophysical Journal, 2021Co-Authors: Xiaowei Duan, Xiaodian Chen, Licai Deng, Fan Yang, Chao Liu, Anupam Bhardwaj, Huawei ZhangAbstract:The nature of shock waves in non-fundamental mode RR Lyrae stars remains a mystery because of limited spectroscopic observations. We apply a pattern recognition algorithm on spectroscopic data from SDSS and LAMOST and report the first evidence of Hydrogen Emission in first-overtone and multi-mode RR Lyrae stars showing the "first apparition", which is the most prominent observational characteristic of shock in RR Lyrae variables. We find ten RRc stars in SDSS, ten RRc stars in LAMOST, and three RRd stars in LAMOST that show blueshifted Balmer Emissions. The Emission features possibly indicate the existence of shock waves. We calculate the radial velocities of the Emission lines, which are related to the physical conditions occurring in the radiative zone of shock waves. Using photometric observations from ZTF, we present a detailed light curve analysis for the frequency components in one of our RRd stars with Hydrogen Emission, RRdl3, for possible modulations. With the enormous volume of upcoming spectral observations of variable stars, our study raises the possibility of connecting the unexplained Blazhko effect to shock waves in non-fundamental mode RR Lyrae stars.
Varsha P. Kulkarni - One of the best experts on this subject based on the ideXlab platform.
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NICMOS Imaging of Molecular Hydrogen Emission in Seyfert Galaxies
The Astrophysical Journal, 1999Co-Authors: Alice C. Quillen, Marcia J. Rieke, Almudena Alonso-herrero, George H. Rieke, M. Ruiz, Varsha P. KulkarniAbstract:We present near-infrared (NICMOS) imaging of broadband and molecular Hydrogen Emission in Seyfert galaxies. In six of 10 Seyfert galaxies we detect resolved or extended Emission in the 1-0 S(1) 2.121 μm or 1-0 S(3) 1.9570 μm molecular Hydrogen lines. We did not detect Emission in the most distant galaxy or in two Seyfert 1 galaxies because of the luminosity of the nuclear point sources. In NGC 5643, NGC 2110, and Mrk 1066, molecular Hydrogen Emission is detected in the extended narrow-line region on scales of a few hundred parsecs from the nucleus. Emission is coincident with [O III] and Hα + [N II] line Emission. This Emission is also near dust lanes observed in the visible to near-infrared color maps, suggesting that a multiphase medium exists near the ionization cones and that the morphology of the line Emission is dependent on the density of the ambient media. The high 1-0 S(1) or S(3) H2 to Hα flux ratio suggests that shock excitation of molecular Hydrogen (rather than UV fluorescence) is the dominant excitation process in these extended features. In NGC 2992 and NGC 3227 the molecular Hydrogen Emission is from 800 and 100 pc diameter "disks" (respectively) that are not directly associated with [O III] Emission and are near high levels of extinction (AV 10). The molecular Hydrogen Emission in NGC 4945 appears to be from the edge of a 100 pc superbubble. The molecular gas in these three galaxies could be excited by processes associated with local star formation. We confirm previous spectroscopic studies finding that no single mechanism is likely to be responsible for the molecular Hydrogen excitation in Seyfert galaxies.
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NICMOS Imaging of Molecular Hydrogen Emission in Seyfert Galaxies
The Astrophysical Journal, 1999Co-Authors: Alice C. Quillen, Marcia J. Rieke, Almudena Alonso-herrero, George H. Rieke, M. Ruiz, Varsha P. KulkarniAbstract:We present NICMOS imaging of broad band and molecular Hydrogen Emission in Seyfert galaxies. In 6 of 10 Seyferts we detect resolved or extended Emission in the 1-0 S(1) 2.121 or 1-0 S(3) 1.9570 micron molecular Hydrogen lines. We did not detect Emission in the most distant galaxy or in the 2 Seyfert 1 galaxies in our sample because of the luminosity of the nuclear point sources. In NGC 5643, NGC 2110 and MKN 1066, molecular Hydrogen Emission is detected in the extended narrow line region on scales of a few hundred pc from the nucleus. Emission is coincident with [OIII] and H alpha+[NII] line Emission. This Emission is also near dust lanes observed in the visible to near-infrared color maps suggesting that a multiphase medium exists near the ionization cones and that the morphology of the line Emission is dependent on the density of the ambient media. The high 1-0 S(1) or S(3) H2 to H alpha flux ratio suggests that shock excitation of molecular Hydrogen (rather than UV fluorescence) is the dominant excitation process in these extended features. In NGC 2992 and NGC 3227 the molecular Hydrogen Emission is from 800 and 100 pc diameter `disks' (respectively) which are not directly associated with [OIII] Emission and are near high levels of extinction (AV > 10). In NGC 4945 the molecular Hydrogen Emission appears to be from the edge of a 100 pc superbubble. In these 3 galaxies the molecular gas could be excited by processes associated with local star formation. We confirm previous spectroscopic studies finding that no single mechanism is likely to be responsible for the molecular Hydrogen excitation in Seyfert galaxies.
