17,722 results
Search Results
2. EPOCHS Paper V. The dependence of galaxy formation on galaxy structure at z < 7 from JWST observations.
- Author
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Conselice, Christopher J, Basham, Justin T F, Bettaney, Daniel O, Ferreira, Leonardo, Adams, Nathan, Harvey, Thomas, Ormerod, Katherine, Caruana, Joseph, Bluck, Asa F L, Li, Qiong, Roper, William J, Trussler, James, Irodotou, Dimitrios, and Austin, Duncan
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GALAXY formation , *MAIN sequence (Astronomy) , *PHYSICAL cosmology , *DISK galaxies , *STARBURSTS , *SUPERMASSIVE black holes , *STELLAR mass - Abstract
We measure the broad impact of galaxy structure on galaxy formation by examining the ongoing star formation and integrated star formation history as revealed through the stellar masses of galaxies at z < 7 based on JWST CEERS data from the Extended Groth Strip (EGS). Using the morphological catalog of 3965 visually classified JWST galaxies from Ferreira et al. (2023), we investigate the evolution of stars, and when they form, as a function of morphological type as well as galaxies classified as passive and starburst through spectral energy distributions. Although disc galaxies dominate the structures of galaxies at z < 7, we find that these discs are in general either 'passive', or on the main sequence of star formation, and do not contain a large population of starburst galaxies. We also find no significant correlation between morphological type and the star formation rate or colours of galaxies at z < 7. In fact, we find that the morphologically classified 'spheroids' tend to be blue and are not found to be predominately passive systems at z > 1.5. We also find that the stellar mass function for disc galaxies does not evolve significantly during this time, whereas other galaxy types, such as the peculiar population, evolve dramatically, declining at lower redshifts. This indicates that massive peculiars are more common at higher redshifts. We further find that up to z ∼ 7, the specific star formation rate (sSFR) does not vary with visual morphology, but strongly depends on stellar mass and internal galaxy mass density. This demonstrates that at early epochs galaxy assembly is a mass-driven, rather than a morphologically driven process. Quenching of star formation is therefore a mass-dominated process throughout the universe's history, likely due to the presence of supermassive black holes. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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3. EPOCHS Paper – VIII. An insight into MIRI-selected galaxies in SMACS-0723 and the benefits of deep MIRI photometry in revealing AGN and the dusty universe.
- Author
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Li, Qiong, Conselice, Christopher J, Adams, Nathan, Trussler, James A A, Austin, Duncan, Harvey, Thomas, Ferreira, Leonardo, Caruana, Joseph, Ormerod, Katherine, and Juodžbalis, Ignas
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GALAXIES , *GALAXY clusters , *ACTIVE galactic nuclei , *STELLAR mass , *PHOTOMETRY , *REDSHIFT ,UNIVERSE - Abstract
We present the analysis of the stellar population and star formation history of 181 MIRI selected galaxies at z = 0 − 3.5 in the massive galaxy cluster field SMACS J0723.3–7327, commonly referred to as SMACS0723, using the JWST Mid-Infrared Instrument (MIRI). We combine the data with the JWST Near Infrared Camera (NIRCam) catalogue, in conjunction with the Hubble Space Telescope (HST) WFC3/IR and ACS imaging. We find that the MIRI bands capture PAH features and dust emission, significantly enhancing the accuracy of photometric redshift and measurements of the physical properties of these galaxies. The median photo- z 's of galaxies with MIRI data are found to have a small 0.1 per cent difference from spectroscopic redshifts and reducing the error by 20 per cent. With MIRI data included in SED fits, we find that the measured stellar masses are unchanged, while the star formation rate is slightly lower by 0.1 dex. We also fit the median SED of active galactic nuclei (AGNs) and star-forming galaxies (SFG) separately. MIRI data provides tighter constraints on the AGN contribution, reducing the typical AGN contributions by ∼15 per cent. In addition, we also compare the median SED obtained with and without MIRI, and we find that including MIRI data yields steeper optical and UV slopes, indicating bluer colours, lower dust attenuation, and younger stellar populations. In the future, MIRI/MRS will enhance our understanding by providing more detailed spectral information and allowing for the study of specific emission features and diagnostics associated with AGN. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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4. Systematic reanalysis of KMTNet microlensing events, paper I: Updates of the photometry pipeline and a new planet candidate.
- Author
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(杨弘靖), Hongjing Yang, Yee, Jennifer C, Hwang, Kyu-Ha, (钱奇玥), Qiyue Qian, Bond, Ian A, Gould, Andrew, (胡哲程), Zhecheng Hu, (张纪元), Jiyuan Zhang, (毛淑德), Shude Mao, (祝伟), Wei Zhu, Albrow, Michael D, Chung, Sun-Ju, Kim, Seung-Lee, Park, Byeong-Gon, Han, Cheongho, Jung, Youn Kil, Ryu, Yoon-Hyun, Shin, In-Gu, Shvartzvald, Yossi, and Cha, Sang-Mok
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GAS giants , *PHOTOMETRY , *PLANETARY orbits , *NATURAL satellites , *GRAVITATIONAL lenses - Abstract
In this work, we update and develop algorithms for KMTNet tender-love care (TLC) photometry in order to create a new, mostly automated, TLC pipeline. We then start a project to systematically apply the new TLC pipeline to the historic KMTNet microlensing events, and search for buried planetary signals. We report the discovery of such a planet candidate in the microlensing event MOA-2019-BLG-421/KMT-2019-BLG-2991. The anomalous signal can be explained by either a planet around the lens star or the orbital motion of the source star. For the planetary interpretation, despite many degenerate solutions, the planet is most likely to be a Jovian planet orbiting an M or K dwarf, which is a typical microlensing planet. The discovery proves that the project can indeed increase the sensitivity of historic events and find previously undiscovered signals. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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5. Systematic reanalysis of KMTNet microlensing events, paper I: Updates of the photometry pipeline and a new planet candidate
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Yang, Hongjing, primary, Yee, Jennifer C, additional, Hwang, Kyu-Ha, additional, Qian, Qiyue, additional, Bond, Ian A, additional, Gould, Andrew, additional, Hu, Zhecheng, additional, Zhang, Jiyuan, additional, Mao, Shude, additional, Zhu, Wei, additional, Albrow, Michael D, additional, Chung, Sun-Ju, additional, Kim, Seung-Lee, additional, Park, Byeong-Gon, additional, Han, Cheongho, additional, Jung, Youn Kil, additional, Ryu, Yoon-Hyun, additional, Shin, In-Gu, additional, Shvartzvald, Yossi, additional, Cha, Sang-Mok, additional, Kim, Dong-Jin, additional, Kim, Hyoun-Woo, additional, Lee, Chung-Uk, additional, Lee, Dong-Joo, additional, Lee, Yongseok, additional, Pogge, Richard W, additional, Zang, Weicheng, additional, Abe, Fumio, additional, Barry, Richard, additional, Bennett, David P, additional, Bhattacharya, Aparna, additional, Donachie, Martin, additional, Fujii, Hirosane, additional, Fukui, Akihiko, additional, Hirao, Yuki, additional, Itow, Yoshitaka, additional, Kirikawa, Rintaro, additional, Kondo, Iona, additional, Koshimoto, Naoki, additional, Silva, Stela Ishitani, additional, Li, Man Cheung Alex, additional, Matsubara, Yutaka, additional, Muraki, Yasushi, additional, Suzuki, Daisuke, additional, Tristram, Paul J, additional, Yonehara, Atsunori, additional, Ranc, Clément, additional, Miyazaki, Shota, additional, Olmschenk, Greg, additional, Rattenbury, Nicholas J, additional, Satoh, Yuki, additional, Shoji, Hikaru, additional, Sumi, Takahiro, additional, Tanaka, Yuzuru, additional, and Yamawaki, Tsubasa, additional
- Published
- 2023
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6. Numerical modelling of the lobes of radio galaxies – Paper V: universal pressure profile cluster atmospheres.
- Author
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Stimpson, M, Hardcastle, M J, and Krause, M G H
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KELVIN-Helmholtz instability , *SYNCHROTRON radiation , *CORE materials , *ATMOSPHERE , *RADIO galaxies , *ATMOSPHERIC models - Abstract
We present relativistic magnetohydrodynamic modelling of jets running into hydrostatic, spherically symmetric cluster atmospheres. For the first time in a numerical simulation, we present model cluster atmospheres based upon the universal pressure profile (UPP), incorporating a temperature profile for a 'typical' self-similar atmosphere described by only one parameter – M 500. We explore a comprehensive range of realistic atmospheres and jet powers and derive dynamic, energetic, and polarimetric data which provide insight into what we should expect of future high-resolution studies of AGN outflows. From the simulated synchrotron emission maps which include Doppler beaming we find sidedness distributions that agree well with observations. We replicated a number of findings from our previous work, such as higher power jets inflating larger aspect-ratio lobes, and the cluster environment impacting the distribution of energy between the lobe and shocked regions. Comparing UPP and β-profiles we find that the cluster model chosen results in a different morphology for the resultant lobes with the UPP more able to clear lobe material from the core; and that these different atmospheres influence the ratio between the various forms of energy in the fully developed lobes. This work also highlights the key role played by Kelvin–Helmholtz instabilities in the formation of realistic lobe aspect ratios. Our simulations point to the need for additional lobe-widening mechanisms at high jet powers, for example jet precession. Given that the UPP is our most representative general cluster atmosphere, these numerical simulations represent the most realistic models yet for spherically symmetric atmospheres. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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7. Enhanced phase mixing of torsional Alfvén waves in stratified and divergent solar coronal structures – Paper I. Linear solutions
- Author
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David Tsiklauri and Callum Boocock
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Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,FOS: Physical sciences ,Astronomy and Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
We derive a corrected analytical solution for the propagation and enhanced phase mixing of torsional Alfv\'en waves, in a potential magnetic field with exponentially divergent field lines, embedded in a stratified solar corona. Further we develop a code named TAWAS which calculates the analytic solution describing torsional Alfv\'en waves using IDL software language. We then use TAWAS to demonstrate that both our correction to the analytic solution and the inclusion of wave reflection have a significant impact on Alfv\'en wave damping. We continue to utilise TAWAS by performing a parameter study in order to identify the conditions under which enhanced phase mixing is strongest. We find that phase mixing is the strongest for high frequency Alfv\'en waves in magnetic fields with highly divergent field lines and without density stratification. We then present a finite difference solver, Wigglewave, which solves the linearised evolution equations for the system directly. Comparing solutions from TAWAS and Wigglewave we see that our analytical solution is accurate within the limits of the WKB approximation but under-reports the wave damping, caused by enhanced phase mixing, beyond the WKB limit. Both TAWAS and Wigglewave solve the linearised governing equations and not the complete nonlinear MHD equations. Paper II will consider simulations that solve the full MHD equations including important nonlinear effects., Comment: Published version
- Published
- 2021
8. Enhanced phase mixing of torsional Alfvén waves in stratified and divergent solar coronal structures – Paper I. Linear solutions.
- Author
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Boocock, C and Tsiklauri, D
- Subjects
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PLASMA Alfven waves , *MAGNETOHYDRODYNAMIC waves , *TORSIONAL vibration , *WKB approximation , *SOLAR corona , *FINITE differences , *EVOLUTION equations - Abstract
We derive a corrected analytical solution for the propagation and enhanced phase mixing of torsional Alfvén waves, in a potential magnetic field with exponentially divergent field lines, embedded in a stratified solar corona. Further we develop a code named TAWAS that calculates the analytic solution describing torsional Alfvén waves using idl software language. We then use TAWAS to demonstrate that both our correction to the analytic solution and the inclusion of wave reflection have a significant impact on Alfvén wave damping. We continue to utilize TAWAS by performing a parameter study in order to identify the conditions under which enhanced phase mixing is strongest. We find that phase mixing is the strongest for high frequency Alfvén waves in magnetic fields with highly divergent field lines and without density stratification. We then present a finite difference solver, Wigglewave , which solves the linearized evolution equations for the system directly. Comparing solutions from TAWAS and Wigglewave we see that our analytical solution is accurate within the limits of the WKB approximation but under-reports the wave damping, caused by enhanced phase mixing, beyond the WKB limit. Both TAWAS and Wigglewave solve the linearized governing equations and not the complete non-linear magnetohydrodynamics (MHD) equations. Paper II will consider simulations that solve the full MHD equations including important non-linear effects. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
9. Enhanced phase mixing of torsional Alfvén waves in stratified and divergent solar coronal structures – Paper I. Linear solutions
- Author
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Boocock, C, primary and Tsiklauri, D, additional
- Published
- 2021
- Full Text
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10. Hierarchical Bayesian approach for estimating physical properties in nearby galaxies: Age Maps (Paper II)
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Sánchez-Gil, M Carmen, primary, Alfaro, Emilio J, additional, Cerviño, Miguel, additional, Pérez, Enrique, additional, Bland-Hawthorn, Joss, additional, and Jones, D Heath, additional
- Published
- 2018
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11. Hierarchical Bayesian approach for estimating physical properties in nearby galaxies: Age Maps (Paper II).
- Author
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Sánchez-Gil, M Carmen, Alfaro, Emilio J, Cerviño, Miguel, Pérez, Enrique, Bland-Hawthorn, Joss, and Jones, D Heath
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STAR formation , *STARBURSTS , *ASTRONOMICAL observations , *BAYESIAN analysis , *ASTROPHYSICS - Abstract
One of the fundamental goals of modern astrophysics is to estimate the physical parameters of galaxies. We present a hierarchical Bayesian model to compute age maps from images in the H α line (taken with Taurus tunable filter, TTF), ultraviolet band (GALEX far UV, FUV), and infrared bands (Spitzer 24, 70, and 160 |$\mu$| m). We present the burst ages for young stellar populations in a sample of nearby and nearly face-on galaxies. The H α to FUV flux ratio is a good relative indicator of the very recent star formation history (SFH). As a nascent star-forming region evolves, the H α line emission declines earlier than the UV continuum, leading to a decrease in the H α/FUV ratio. Using star-forming galaxy models, sampled with a probabilistic formalism, and allowing for a variable fraction of ionizing photons in the clusters, we obtain the corresponding theoretical ratio H α/FUV to compare with our observed flux ratios, and thus to estimate the ages of the observed regions. We take into account the mean uncertainties and the interrelationships between parameters when computing H α/FUV. We propose a Bayesian hierarchical model where a joint probability distribution is defined to determine the parameters (age, metallicity, IMF) from the observed data (the observed flux ratios H α/FUV). The joint distribution of the parameters is described through independent and identically distributed (i.i.d.) random variables generated through MCMC (Markov Chain Monte Carlo) techniques. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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12. H2O Southern Galactic Plane Survey (HOPS): Paper III - properties of dense molecular gas across the inner Milky Way.
- Author
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Henshaw, J., Walker, D., Barnes, A. T., Moore, T. J. T., Longmore, S. N., Hoare, M. G., Thompson, M. A., Lo, N., Burke, D. J., Walsh, A. J., Purcell, C. R., Breen, S. L., Britton, T., Urquhart, J., Lowe, V., Whiting, M., Green, J. A., Harvey-Smith, L., Indermuehle, B., and Voronkov, M. A.
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MASERS , *ASTRONOMICAL masers , *STAR formation , *STELLAR evolution , *INTERSTELLAR medium - Abstract
The H2O Southern Galactic Plane Survey (HOPS) has mapped 100 deg² of the Galactic plane for water masers and thermal molecular line emission using the 22 m Mopra telescope. We describe the automated spectral-line fitting pipelines used to determine the properties of emission detected in HOPS data cubes, and use these to derive the physical and kinematic properties of gas in the survey. A combination of the angular resolution, sensitivity, velocity resolution and high critical density of lines targeted make the HOPS data cubes ideally suited to finding precursor clouds to the most massive and dense stellar clusters in the Galaxy. We compile a list of the most massive HOPS ammonia regions and investigate whether any may be young massive cluster progenitor gas clouds. HOPS is also ideally suited to trace the flows of dense gas in the Galactic Centre. We find the kinematic structure of gas within the inner 500 pc of the Galaxy is consistent with recent predictions for the dynamical evolution of gas flows in the centre of the Milky Way. We confirm a recent finding that the dense gas in the inner 100 pc has an oscillatory kinematic structure with characteristic length-scale of 20 pc, and also identify similar oscillatory kinematic structure in the gas at radii larger than 100 pc. Finally, we make all of the above fits and the remaining HOPS data cubes across the 100 deg² of the survey available to the community. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
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13. H2O Southern Galactic Plane Survey (HOPS): Paper III – properties of dense molecular gas across the inner Milky Way
- Author
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Longmore, S. N., primary, Walsh, A. J., additional, Purcell, C. R., additional, Burke, D. J., additional, Henshaw, J., additional, Walker, D., additional, Urquhart, J., additional, Barnes, A. T., additional, Whiting, M., additional, Burton, M. G., additional, Breen, S. L., additional, Britton, T., additional, Brooks, K. J., additional, Cunningham, M. R., additional, Green, J. A., additional, Harvey-Smith, L., additional, Hindson, L., additional, Hoare, M. G., additional, Indermuehle, B., additional, Jones, P. A., additional, Lo, N., additional, Lowe, V., additional, Moore, T. J. T., additional, Thompson, M. A., additional, and Voronkov, M. A., additional
- Published
- 2017
- Full Text
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14. A comprehensive long-term study of the radio and X-ray variability of NGC 4051 Paper II
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Jones, S., primary, McHardy, I., additional, and Maccarone, T. J., additional
- Published
- 2016
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15. A comprehensive long-term study of the radio and X-ray variability of NGC 4051 Paper II.
- Author
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Jones, S., McHardy, I., and Maccarone, T. J.
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X-ray binaries , *SEYFERT galaxies , *SPIRAL galaxies , *STELLAR luminosity function , *SOLAR radio emission , *ACTIVE galactic nuclei - Abstract
The origin of the low-luminosity radio emission in radio-quiet active galactic nucleus, is unknown. The detection of a positive correlation between the radio and X-ray emission would imply a jet-like origin, similar to that seen in 'hard-state' X-ray binary systems. In our previous work, we found no believable radio variability in the well-known X-ray bright Seyfert 1 galaxy NGC 4051, despite large amplitude X-ray variability. In this study, we have carefully re-analysed radio and X-ray observations using the same methods as our previous work; we again find no evidence for core radio variability. In direct contrast to our findings, another study claim significant radio variability and a distinctive anticorrelation between radio and X-ray data for the same source. The other study report only integral flux values and do not consider the effect of the changing array on the synthesized beam. In both our studies of NGC 4051, we have taken great care to account for the effect that the changing beam size has on the measured radio flux and as a result we are confident that our method gives more accurate values for the intrinsic core radio flux. However, the lack of radio variability we find is hard to reconcile because radio images of NGC 4051 do show jet-like structure. We suggest that the radio structures observed are likely the result of a previous period of higher radio activity and that the current level of radio emission from a compact nuclear jet is low. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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16. Investigation of chemical differentiation among the NGC 2264 cluster-forming clumps.
- Author
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Taniguchi, Kotomi, Plunkett, Adele, Herbst, Eric, Dobashi, Kazuhito, Shimoikura, Tomomi, Nakamura, Fumitaka, and Saito, Masao
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INDICATORS & test-papers , *RADIO telescopes , *RADIATION chemistry , *ASTRONOMICAL surveys , *INVESTIGATIONS - Abstract
We have carried out mapping observations of molecular emission lines of HC3N and CH3OH toward two massive cluster-forming clumps, NGC 2264-C and NGC 2264-D, using the Nobeyama 45-m radio telescope. We derive an I (HC3N)/ I (CH3OH) integrated intensity ratio map, showing a higher value at clumps including 2MASS (Two Micron All Sky Survey) point sources at the northern part of NGC 2264-D. Possible interpretations of the I (HC3N)/ I (CH3OH) ratio are discussed. We have also observed molecular emission lines from CCS and N2H+ toward five positions in each clump. We investigate the N (N2H+)/ N (CCS) and N (N2H+)/ N (HC3N) column density ratios among the ten positions in order to test whether they can be used as chemical evolutionary indicators in these clumps. The N (N2H+)/ N (CCS) ratio shows a very high value toward a bright embedded IR source (IRS1), whereas the N (N2H+)/ N (HC3N) ratio at IRS1 is comparable with those at the other positions. These results suggest that ultraviolet radiation affects the chemistry around IRS1. We find that there are positive correlations between these column density ratios and the excitation temperatures of N2H+, which implies the chemical evolution of clumps. These chemical evolutionary indicators likely reflect the combination of evolution along the filamentary structure and evolution of each clump. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
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17. Photoelectric radial velocities, Paper XVI 625 ninth-magnitude K0 stars in the six southern Clube Selected Areas
- Author
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R. F. Griffin and A. P. Cornell
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Physics ,Radial velocity ,Stars ,Apparent magnitude ,Space and Planetary Science ,Observatory ,Galactic coordinate system ,Velocity dispersion ,Magnitude (mathematics) ,Astronomy and Astrophysics ,Astrophysics ,Table (information) - Abstract
Paper XIII of this series presented radial velocities for 406 stars in certain of the Clube Selected Areas, a set of areas systematically arranged in Galactic coordinates. We now complete the survey by providing the radial velocities, mostly obtained at the European Southern Observatory (ESO), of 625 stars in the six southernmost Areas. Each star has been measured at least twice; the mean velocities have standard errors typically of 0.2‐0.3 km s −1 . Additional observations made from Haute-Provence of many of the stars that are observable from there have helped to identify, and in some instances to characterize, the ∼70 spectroscopic binaries discovered in this programme. The final results of the programme, complementing those given in table 3 of Paper XIII, are summarized in Table 12, which presents the mean velocities and velocity dispersions in the six southern Areas. It is noted that the difference between Paper XIII and this one as regards the provenance of the radial velocities has led to a small difference in zero-points, which is discussed in Section 3 and needs to be taken into account in any analysis of the combined data.
- Published
- 2006
18. Photoelectric radial velocities, Paper XVII The orbits of 30 spectroscopic binaries in the southern Clube Selected Areas
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R. F. Griffin
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Radial velocity ,Physics ,Space and Planetary Science ,Observatory ,Binary number ,Astronomy ,Astronomy and Astrophysics ,Observable ,Astrophysics ,Photoelectric effect ,Giant star ,Variation (astronomy) - Abstract
Three of the six southern Clube Areas that were mainly observed at the European Southern Observatory and whose principal results are given in Paper XVI are marginally observable from Haute-Provence. Additional measurements obtained on several observing runs there enabled orbits to be determined (in most cases rather poorly, owing to the paucity of data) for 30 of the newly discovered spectroscopic-binary systems; they are presented in this paper. One object, HD 33978, seems to be of such significance that special efforts have been made, largely by Drs J. Andersen and H. Lindgren, to obtain additional radial-velocity measurements. That system is shown to be a double-lined binary with a period of only 10.67 d despite one of its components being a late-type giant. The giant star has a projected rotational velocity of almost 40 km s -1 ; it could be expected to exhibit RS CVn-type photometric variations, which have not yet been observed, in addition to the 'ellipsoidal variation', discovered by Hipparcos, which occasioned its designation as VV Lep.
- Published
- 2006
19. Composite spectra Paper 16: HR 3222, a 2.5-yr binary with a metallic-line secondary
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R. F. Griffin and R. E. M. Griffin
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Physics ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Mass ratio ,Giant star ,Spectral line ,Radial velocity ,Wavelength ,Stars ,Space and Planetary Science ,Astrophysics::Earth and Planetary Astrophysics ,Binary system ,Spectroscopy ,Astrophysics::Galaxy Astrophysics - Abstract
HR 3222 is a late-type giant star that has long been known as a spectroscopic binary. A single-lined orbit is readily found; it has a period of 955 d and an eccentricity of 0.33. The spectrum is noticeably composite, especially at short wavelengths; radial-velocity traces show a weak secondary dip that is broadened by a rotational velocity of 18 km s -1 . We employ high-dispersion spectroscopy and uncover the secondary spectrum by subtracting from the observed composite one the spectrum of the K0 giant β Gem; the residue is a metallic-line star of type kA8hF2mF4, and measurements of its wavelength displacement from the primary spectrum give a more reliable radial velocity for that component than seems achievable from radial-velocity traces. The mass ratio is 1.20 ± 0.03. The stars can both be placed on an evolutionary track corresponding to an age of 1.4 Gyr. The fact that the secondary component is a metallic-line star cannot be attributed to the result of tidal effects in this binary system.
- Published
- 2010
20. Brightest group galaxies: stellar mass and star formation rate (paper I)
- Author
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Gozaliasl, Ghassem, primary, Finoguenov, Alexis, additional, Khosroshahi, Habib G., additional, Mirkazemi, Mohammad, additional, Erfanianfar, Ghazaleh, additional, and Tanaka, Masayuki, additional
- Published
- 2016
- Full Text
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21. Composite spectra Paper 13: 93 Leonis, a chromospherically-active binary
- Author
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R. E. M. Griffin and R. F. Griffin
- Subjects
Red-giant branch ,Physics ,Stars ,Stellar mass ,Space and Planetary Science ,Metallicity ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Stellar classification ,Stellar evolution ,Astronomical spectroscopy ,Orbital inclination - Abstract
We isolate the spectrum of the secondary component of the composite-binary system 93 Leonis by spectrum subtraction, classify it, and measure the mass ratio of the system. An accurate visual orbit and a well-determined parallax provide reliable measurements of orbital inclination and distance, enabling us to determine precisely the individual masses and other stellar parameters. The primary star is of type ∼G7 III, and the secondary is a rapidly rotating star of type A7 IV. Our photographic spectra at 10 A mm−1 are invaluable for accurate spectral classification in such cases. By combining 23 measurements of the secondary's velocity with 102 of the primary's and deriving a double-lined orbit, we determine the mass ratio (q=M1/M2) of 93 Leo to be 1.09 ± 0.04. The same value is derived by cross-correlating high-dispersion spectra of 93 Leo B extracted from opposite nodal phases. That value of q is consonant with previous research, but its precision is considerably improved. We show that random errors arising from the cross-correlation of broad, weak features constitute a natural limit to that precision. The derived masses of M1= 2.2 M⊙, M2= 2.0 M⊙ for the giant and dwarf, respectively, constrain the choice of models for fitting evolutionary tracks in the (log Teff, log L) plane. The giant is almost certainly on its first ascent of the red giant branch, and the dwarf has evolved significantly from the main sequence. The stars fit an isochrone for log(age) = 8.95, about 0.9 Gyr. Metallicity near to solar is suggested by the close correspondence between the component spectra and those of the respective solar-abundance standards. The primary in 93 Leo displays a marked level of chromospheric activity. By combining our high-dispersion spectra we are able to isolate emission in the Ca ii K line. The chromospheric material has a small infall velocity, giving rise to a disc-averaged redshift of about 4 km s−1, and an unchanging velocity profile which can be attributed to a large number of small, active events like prominences across the surface. While we can say that there was no perceptible change in the emission strength over an interval of 4 months, we have not made systematic observations to monitor its long-term stability. We contrast the components of 93 Leo with those of α Equ, whose analysis was the subject of Paper 11 in this series. The primary components are very similar, but the two secondary components are extremely different in nature: whereas 93 Leo B is a broad-lined, apparently normal A star, the secondary of α Equ is a sharp-lined Am star of type ∼kA3hA4mA9. We question why that should be, and recommend that a greater emphasis be placed on extracting accurate stellar parameters from the components of spectroscopic binaries as a means towards a better understanding of the vagaries of stellar evolution. 93 Leo has a 9-mag visual companion which appears to be a physical member of the system and to be a single-lined spectroscopic binary with a period of the order of a century.
- Published
- 2004
22. Composite spectra Paper 14: HR 1129, a long-period binary showing evidence of circumbinary material
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D. J. Stickland, R. F. Griffin, and R. E. M. Griffin
- Subjects
Radial velocity ,Physics ,Orbit ,Stars ,Space and Planetary Science ,Extinction (astronomy) ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Mass ratio ,Circumbinary planet ,Spectral line ,Astronomical spectroscopy - Abstract
HR 1129 is a 4.8-mag star in the constellation Camelopardus, strangely (in view of its brightness) lacking a constellation designation. It has long been known to exhibit a composite spectrum consisting of a late-type primary and an early-type secondary. The radial velocity of the primary is easily measured, and was announced as variable nearly 100 years ago. A preliminary orbit with a period of 6150 d was given for it by one of the present authors in 1990; our new value is 6124 ± 3 d. The system has been resolved by speckle interferometry, but has not been measured systematically by that technique. The spectrum of the primary is found to be very similar to that of a Aqr (G2 Ib), although the parallax shows HR 1129 to be somewhat less luminous. The secondary spectrum has been isolated by subtraction and has proved to be that of a B7 star that is somewhat above the main sequence and may itself already be a giant. We present a comprehensive discussion of the spectra of both stars, and deduce that the system is considerably reddened: E(B - V) ∼ 0.30, A V Ā 0.9 mag. By incorporating 25 measurements of the radial velocity of the secondary, we calculate a double-lined orbit solution which gives the mass ratio for the components as 1.109 ± 0.022; we determine individual masses of 4.8-5.2 M ⊙ (primary) and 4.3-4.7 M ⊙ (secondary). The orbit is viewed at an inclination of ∼ 87°, but there are no eclipses. However, around the phases of conjunction the Mg II doublet near λ2800 A, as seen in IUE spectra, exhibits evidence of two circumstellar absorption systems, which we interpret as a wind from the cool giant and a static shell around it. Substantial 100-μm emission recorded by IRAS points to the presence of warm circumbinary dust enveloping the system, and is likely to have originated in the stellar wind.
- Published
- 2006
23. Photoelectric radial velocities, Paper XVI 625 ninth-magnitude K0 stars in the six southern Clube Selected Areas.
- Author
-
Griffin, R. F. and Cornell, A. P.
- Subjects
- *
GALAXIES , *PHOTOELECTRICITY , *BINARY stars , *ASTRONOMICAL spectroscopy , *DISPERSION (Chemistry) - Abstract
Paper XIII of this series presented radial velocities for 406 stars in certain of the Clube Selected Areas, a set of areas systematically arranged in Galactic coordinates. We now complete the survey by providing the radial velocities, mostly obtained at the European Southern Observatory (ESO), of 625 stars in the six southernmost Areas. Each star has been measured at least twice; the mean velocities have standard errors typically of 0.2–0.3 km s−1. Additional observations made from Haute-Provence of many of the stars that are observable from there have helped to identify, and in some instances to characterize, the ∼70 spectroscopic binaries discovered in this programme. The final results of the programme, complementing those given in table 3 of Paper XIII, are summarized in Table 12 , which presents the mean velocities and velocity dispersions in the six southern Areas. It is noted that the difference between Paper XIII and this one as regards the provenance of the radial velocities has led to a small difference in zero-points, which is discussed in Section 3 and needs to be taken into account in any analysis of the combined data. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
24. Photoelectric radial velocities, Paper XVII The orbits of 30 spectroscopic binaries in the southern Clube Selected Areas.
- Author
-
Griffin, R. F.
- Subjects
- *
BINARY stars , *ASTRONOMICAL spectroscopy , *ORBITS (Astronomy) , *ASTRONOMICAL photometry , *GIANT stars - Abstract
Three of the six southern Clube Areas that were mainly observed at the European Southern Observatory and whose principal results are given in Paper XVI are marginally observable from Haute-Provence. Additional measurements obtained on several observing runs there enabled orbits to be determined (in most cases rather poorly, owing to the paucity of data) for 30 of the newly discovered spectroscopic-binary systems; they are presented in this paper. One object, HD 33978, seems to be of such significance that special efforts have been made, largely by Drs J. Andersen and H. Lindgren, to obtain additional radial-velocity measurements. That system is shown to be a double-lined binary with a period of only 10.67 d despite one of its components being a late-type giant. The giant star has a projected rotational velocity of almost 40 km s−1; it could be expected to exhibit RS CVn-type photometric variations, which have not yet been observed, in addition to the ‘ellipsoidal variation’, discovered by Hipparcos, which occasioned its designation as VV Lep. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
25. Composite spectra Paper 11:Equulei, an astrometric binary with an Am secondary
- Author
-
R. E. M. Griffin and R. F. Griffin
- Subjects
Physics ,Plane (geometry) ,Binary number ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Am star ,Mass ratio ,Spectral line ,Luminosity ,Orbit ,Wavelength ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
The spectrum of the secondary component of the bright composite-binary system α Equ, whose visual orbit is already known accurately, is isolated by the method of spectrum subtraction and classified accurately for the first time. The primary is a normal giant of type ∼G7, while the secondary is an Am star of type ∼kA3hA4mA9. The system's mass ratio, q, is determined to be 1.15±0.03 from measurements of the relative radial-velocity displacements between the components. Random and systematic errors in q are evaluated on the basis of the scatter of results derived from sets of spectra obtained from three different sources, and from tests conducted on independent versions of the secondary's spectrum. A spectroscopic analysis of a composite system such as α Equ is strongly challenged by the blending of a great many lines that are common to both spectra. Even when the primary spectrum is thought to have been subtracted adequately, a seemingly unavoidable ghost spectrum of faint residuals can bias wavelength measurements of the secondary's lines. That blending was the principal cause of a history of puzzling and discrepant measurements of q in α Equ. The derived masses of M1=2.3 M⊙, M2=2.0 M⊙ for the giant and dwarf, respectively, constrain the choice of models for fitting evolutionary tracks in the (log Teff, log L) plane; the stellar points fit a single isochrone (for 0.74 Gyr). Both components are found to be slightly over-luminous compared to normal for their supposed luminosity classes. The giant appears to be commencing its first ascent of the red-giant branch. The dwarf has started to evolve away from the main sequence; its MV is similar to that of a sub-giant.
- Published
- 2002
26. Photoelectric radial velocities, Paper XV The triple system HD 149240
- Author
-
Cornell and Griffin
- Subjects
Physics ,Orbit ,Series (mathematics) ,Space and Planetary Science ,Primary (astronomy) ,Singleton ,Triple system ,Astronomy and Astrophysics ,Astrophysics ,Binary system ,Photoelectric effect ,Star (graph theory) - Abstract
HD 149240, an object discussed inconclusively and in part erroneously in two previous papers in this series, is shown to be a triple system with two components (probably both late-type dwarfs) visible in the spectrum. The primary star is the singleton in the outer orbit, the period of which has already been established as 1040 d; its companion is now shown to be a single-lined binary system with a 51-d period, and a model for the system is proposed.
- Published
- 1998
27. Composite spectra Paper 9: HR 5983
- Author
-
R. F. Griffin and R. E. M. Griffin
- Subjects
Loop (topology) ,Physics ,Space and Planetary Science ,Primary (astronomy) ,Component (thermodynamics) ,Astronomy ,Astronomy and Astrophysics ,Binary system ,Astrophysics ,Circular orbit ,Mass ratio ,Spectral line ,Tidal locking - Abstract
HR 5983 is a sixth-magnitude composite-spectrum binary system. It has a circular orbit and a period of 108 d. We separate the component spectra and show that they are of types ∼G6 IIIa and A2.5 IV, with a mass ratio (giant:dwarf) of ∼1.04. We find that the secondary has a mass close to 2.6 M⊙ and has already evolved somewhat from the main sequence, and that the primary appears to have reached the helium-burning ‘blue loop’ stage and is in synchronous rotation. The system resembles Capella in several respects, and may represent an earlier phase in the evolution of the latter.
- Published
- 2000
28. Composite spectra Paper 8: HD 4615/6
- Author
-
R. F. Griffin and R. E. M. Griffin
- Subjects
Physics ,Space and Planetary Science ,K-type main-sequence star ,Composite number ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,A-type main-sequence star ,O-type main-sequence star ,Spectral line - Published
- 1999
29. Composite spectra Paper 13: 93 Leonis, a chromospherically-active binary.
- Author
-
Griffin, R. E. M. and Griffin, R. F.
- Subjects
- *
STELLAR orbits , *STELLAR dynamics , *STELLAR chromospheres , *STARS , *BINARY stars , *ASTRONOMY - Abstract
We isolate the spectrum of the secondary component of the composite-binary system 93 Leonis by spectrum subtraction, classify it, and measure the mass ratio of the system. An accurate visual orbit and a well-determined parallax provide reliable measurements of orbital inclination and distance, enabling us to determine precisely the individual masses and other stellar parameters. The primary star is of type ∼G7 III, and the secondary is a rapidly rotating star of type A7 IV. Our photographic spectra at 10 Å mm-1 are invaluable for accurate spectral classification in such cases. By combining 23 measurements of the secondary's velocity with 102 of the primary's and deriving a double-lined orbit, we determine the mass ratio (q = M1/M2) of 93 Leo to be 1.09 ± 0.04. The same value is derived by cross-correlating high-dispersion spectra of 93 Leo B extracted from opposite nodal phases. That value of q is consonant with previous research, but its precision is considerably improved. We show that random errors arising from the cross-correlation of broad, weak features constitute a natural limit to that precision. The derived masses of M1 = 2.2 M[This symbol cannot be presented in ASCII format], M2 = 2.0 M[This symbol cannot be presented in ASCII format] for the giant and dwarf, respectively, constrain the choice of models for fitting evolutionary tracks in the (log Teff, log L) plane. The giant is almost certainly on its first ascent of the red giant branch, and the dwarf has evolved significantly from the main sequence. The stars fit an isochrone for log(age) = 8.95, about 0.9 Gyr. Metallicity near to solar is suggested by the close correspondence between the component spectra and those of the respective solar-abundance standards. The primary in 93 Leo displays a marked level of chromospheric activity. By combining our high-dispersion spectra we are able to isolate emission in the Ca II K line. The chromospheric material has a small infall velocity, giving rise to a disc-averaged redshift of about 4 km s-1, and an unchanging velocity profile which can be attributed to a large number of small, active events like prominences across the surface. While we can say that there was no perceptible change in the emission strength over an interval of 4 months, we have not made systematic observations to monitor its long-term stability. We contrast the components of 93 Leo with those of α Equ, whose analysis was the subject of Paper 11 in this series. The primary components are very similar, but the two secondary components are extremely different in nature: whereas 93 Leo B is a broad-lined, apparently normal A star, the secondary of α Equ is a sharp-lined Am star of type ∼kA3hA4mA9. We question why that should be, and recommend that a greater emphasis be placed on extracting accurate stellar parameters from the components of spectroscopic binaries as a means towards a better understanding of the vagaries of stellar evolution. 93 Leo has a 9-mag visual companion which appears to be a physical member of the system and to be a single-lined spectroscopic binary with a period of the order of a century. [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
30. Photoelectric radial velocities, Paper XV The triple system HD 149240
- Author
-
R. F. Griffin and A. P. Cornell
- Subjects
Physics ,Radial velocity ,Orbital elements ,Space and Planetary Science ,Triple system ,Binary star ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Photoelectric effect ,Main sequence - Published
- 1998
31. Composite spectra Paper 7: HD 190361
- Author
-
R. Griffin
- Subjects
Physics ,Optics ,Space and Planetary Science ,business.industry ,Composite number ,Astronomy and Astrophysics ,Atomic physics ,business ,Spectral line - Published
- 1997
32. Composite spectra Paper 6: 9 Cygni
- Author
-
R. R. Griffin and D. W. Beggs
- Subjects
Physics ,Space and Planetary Science ,Composite number ,Astronomy and Astrophysics ,Astrophysics ,Spectral line - Published
- 1994
33. Photoelectric radial velocities, Paper XIV. Variation of the radial velocity of ε Cygni
- Author
-
R. F. Griffin
- Subjects
Physics ,Orbital elements ,Stellar kinematics ,media_common.quotation_subject ,Binary number ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Span (engineering) ,Term (time) ,Radial velocity ,Space and Planetary Science ,Eccentricity (behavior) ,Variation (astronomy) ,media_common - Abstract
McMillan et al. have shown from a large number of very precise measurements that the radial velocity of e Cyg has changed by about 0.3 km s −1 over the past five years. We now discuss, on the basis of observations which, although fewer and far less precise, span nearly a century and include continuous coverage by the photoelectric method over the last 25 years, the behaviour of the velocity over the longer term. The star is clearly a spectroscopic binary; there is an unfortunate gap in the radial-velocity data at a critical time, but it seems likely that the period is about 55 yr. It has been possible to derive preliminary orbital elements, which include a high value (0.9) of the eccentricity
- Published
- 1994
34. Imaging on PAPER: Centaurus A at 148 MHz
- Author
-
Stefan, Irina I., primary, Carilli, Chris L., additional, Green, David A., additional, Ali, Zaki, additional, Aguirre, James E., additional, Bradley, Richard F., additional, DeBoer, David, additional, Dexter, Matthew, additional, Gugliucci, Nicole E., additional, Harris, D. E., additional, Jacobs, Daniel C., additional, Klima, Pat, additional, MacMahon, David, additional, Manley, Jason, additional, Moore, David F., additional, Parsons, Aaron R., additional, Pober, Jonathan C., additional, and Walbrugh, William P., additional
- Published
- 2013
- Full Text
- View/download PDF
35. Composite spectra Paper 16: HR 3222, a 2.5-yr binary with a metallic-line secondary.
- Author
-
Griffin, R. E. M. and Griffin, R. F.
- Subjects
- *
WAVELENGTHS , *STARS , *ORBITS (Astronomy) , *SPEED , *SPECTRUM analysis - Abstract
HR 3222 is a late-type giant star that has long been known as a spectroscopic binary. A single-lined orbit is readily found; it has a period of 955 d and an eccentricity of 0.33. The spectrum is noticeably composite, especially at short wavelengths; radial-velocity traces show a weak secondary dip that is broadened by a rotational velocity of 18 km s−1. We employ high-dispersion spectroscopy and uncover the secondary spectrum by subtracting from the observed composite one the spectrum of the K0 giant β Gem; the residue is a metallic-line star of type kA8hF2mF4, and measurements of its wavelength displacement from the primary spectrum give a more reliable radial velocity for that component than seems achievable from radial-velocity traces. The mass ratio is . The stars can both be placed on an evolutionary track corresponding to an age of 1.4 Gyr. The fact that the secondary component is a metallic-line star cannot be attributed to the result of tidal effects in this binary system. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
36. Composite spectra Paper 15: HD 216572, a triple system containing a short-period, double-lined secondary.
- Author
-
Griffin, R. E. M. and Griffin, R. F.
- Subjects
- *
BINARY stars , *STELLAR mass , *GIANT stars , *B stars , *HR diagrams , *ASTRONOMICAL photometry , *SPECTRUM analysis , *STELLAR chromospheres , *STELLAR spectra - Abstract
We analyse 81 optical spectra of the composite-spectrum binary HD 216572, and show that the primary is a cool giant of type G8 III while the secondary is a double-lined binary consisting of two nearly identical B9 dwarfs in a 1.18-d orbit. The inner system undergoes partial eclipses, whose photometry we model to derive the physical parameters of both secondary stars. The outer system does not eclipse. We isolate the combined spectrum of the secondary by spectral subtraction, and from 48 separate radial-velocity measurements of both secondary components we obtain a triple-lined orbit solution from which we determine the individual masses of all three stars and the inclinations of both the inner and the outer orbits. The period of the outer system is 55 d, which is surprisingly short for a giant star, and our detection of small but non-negligible amounts of variable chromospheric emission in the Ca ii K line is not unlike that detected in other systems with comparably short periods. The secondary components are in a circular orbit and are rotating at about ; although their surface-to-surface separation is only the stars are not noticeably distorted geometrically by such close proximity. All three stars appear to be in synchronous rotation in their respective orbits. We derive fairly accurate Hertzsprung–Russell diagram positions for all three stars and compare them to evolutionary tracks calculated for the respective stellar masses, but cannot reconcile the age of the cool giant with that of the B stars. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
37. Composite spectra Paper 14: HR 1129, a long-period binary showing evidence of circumbinary material.
- Author
-
Griffin, R. E. M., Griffin, R. F., and Stickland, D. J.
- Subjects
- *
CONSTELLATIONS , *BINARY stars , *CIRCUMSTELLAR matter , *INTERFEROMETRY , *SPECTRUM analysis , *STELLAR winds - Abstract
HR 1129 is a 4.8-mag star in the constellation Camelopardus, strangely (in view of its brightness) lacking a constellation designation. It has long been known to exhibit a composite spectrum consisting of a late-type primary and an early-type secondary. The radial velocity of the primary is easily measured, and was announced as variable nearly 100 years ago. A preliminary orbit with a period of 6150 d was given for it by one of the present authors in 1990; our new value is 6124 ± 3 d. The system has been resolved by speckle interferometry, but has not been measured systematically by that technique. The spectrum of the primary is found to be very similar to that of α Aqr (G2 Ib), although the parallax shows HR 1129 to be somewhat less luminous. The secondary spectrum has been isolated by subtraction and has proved to be that of a B7 star that is somewhat above the main sequence and may itself already be a giant. We present a comprehensive discussion of the spectra of both stars, and deduce that the system is considerably reddened: . By incorporating 25 measurements of the radial velocity of the secondary, we calculate a double-lined orbit solution which gives the mass ratio for the components as 1.109 ± 0.022; we determine individual masses of (primary) and (secondary). The orbit is viewed at an inclination of ∼ 87°, but there are no eclipses. However, around the phases of conjunction the Mg ii doublet near λ2800 Å, as seen in IUE spectra, exhibits evidence of two circumstellar absorption systems, which we interpret as a wind from the cool giant and a static shell around it. Substantial 100-μm emission recorded by IRAS points to the presence of warm circumbinary dust enveloping the system, and is likely to have originated in the stellar wind. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
38. Composite spectra Paper 11: α Equulei, an astrometric binary with an Am secondary.
- Author
-
Griffin, R.E.M. and Griffin, R.F.
- Subjects
- *
BINARY stars , *ASTRONOMICAL spectroscopy , *STELLAR spectra - Abstract
The spectrum of the secondary component of the bright composite-binary system α Equ, whose visual orbit is already known accurately, is isolated by the method of spectrum subtraction and classified accurately for the first time. The primary is a normal giant of type ∼G7, while the secondary is an Am star of type ∼kA3hA4mA9. The system's mass ratio, q, is determined to be 1.15±0.03 from measurements of the relative radial-velocity displacements between the components. Random and systematic errors in q are evaluated on the basis of the scatter of results derived from sets of spectra obtained from three different sources, and from tests conducted on independent versions of the secondary's spectrum. A spectroscopic analysis of a composite system such as α Equ is strongly challenged by the blending of a great many lines that are common to both spectra. Even when the primary spectrum is thought to have been subtracted adequately, a seemingly unavoidable ghost spectrum of faint residuals can bias wavelength measurements of the secondary's lines. That blending was the principal cause of a history of puzzling and discrepant measurements of q in α Equ. The derived masses of M[sub 1]=2.3 M[sub ⊙], M[sub 2]=2.0 M[sub ⊙] for the giant and dwarf, respectively, constrain the choice of models for fitting evolutionary tracks in the (log T[sub eff], log L) plane; the stellar points fit a single isochrone (for 0.74 Gyr). Both components are found to be slightly over-luminous compared to normal for their supposed luminosity classes. The giant appears to be commencing its first ascent of the red-giant branch. The dwarf has started to evolve away from the main sequence; its M[sub V] is similar to that of a sub-giant. [ABSTRACT FROM AUTHOR]
- Published
- 2002
- Full Text
- View/download PDF
39. Composite spectra Paper 10: the equal-mass binary HR 2030....
- Author
-
Griffin, R.E.M. and Griffin, R.F.
- Subjects
- *
SPECTRUM analysis , *STARS - Abstract
Investigates the separation of spectra of the individual components of HR 2030. Luminosity derived from spectra; Strength of the interstellar K line; Existence of a major non-uniformity of the surface of the primary star.
- Published
- 2000
- Full Text
- View/download PDF
40. Composite spectra Paper 11:Equulei, an astrometric binary with an Am secondary
- Author
-
Griffin, R. E. M., primary and Griffin, R. F., additional
- Published
- 2002
- Full Text
- View/download PDF
41. Composite spectra Paper 8: HD 4615/6.
- Author
-
Griffin, R. E. M. and Griffin, R. F.
- Subjects
- *
BINARY stars , *STELLAR rotation , *STELLAR spectra - Abstract
ABSTRACTHD 4615/6 is a seventh-magnitude composite-spectrum binary system. It has an orbit of moderate eccentricity (0.43) and a period of 303 d. The system is of course unresolved at the telescope, but we are able to separate the spectra of the component stars and show that they are of types K2 III (HD 4615) and A2.5 V (HD 4616), with a mass ratio (giant:dwarf) of approximately 1.25. The orbital inclination is high, but there are no eclipses. The maximum apparent angular separation is expected to be about 0.009 arcsec. Neither star's rotation is synchronized with the orbital motion. [ABSTRACT FROM AUTHOR]
- Published
- 1999
- Full Text
- View/download PDF
42. Editorial: electronic submission of papers by FTP
- Published
- 2001
- Full Text
- View/download PDF
43. Photoelectric radial velocities, Paper XV The triple system HD 149240
- Author
-
Griffin and Cornell
- Abstract
HD 149240, an object discussed inconclusively and in part erroneously in two previous papers in this series, is shown to be a triple system with two components (probably both late‐type dwarfs) visible in the spectrum. The primary star is the singleton in the outer orbit, the period of which has already been established as 1040 d; its companion is now shown to be a single‐lined binary system with a 51‐d period, and a model for the system is proposed.
- Published
- 1998
- Full Text
- View/download PDF
44. Composite spectra Paper 9: HR 5983
- Author
-
Griffin, R. E. M., primary and Griffin, R. F., additional
- Published
- 2000
- Full Text
- View/download PDF
45. A morphological study of galaxies in ZwCl0024+1652, a galaxy cluster at redshift z ∼ 0.4.
- Author
-
Amado, Zeleke Beyoro, Pović, Mirjana, Sánchez-Portal, Miguel, Tessema, S B, Bongiovanni, Ángel, Cepa, Jordi, Cerviño, Miguel, González-Serrano, J Ignacio, Nadolny, Jakub, Garcia, Ana Maria Pérez, Pérez-Martinez, Ricardo, and Pintos-Castro, Irene
- Subjects
GALAXY clusters ,EMISSION-line galaxies ,GALAXIES ,ELECTRONIC paper ,SUPPORT vector machines - Abstract
The well-known cluster of galaxies ZwCl0024+1652 at z ∼ 0.4 lacks an in-depth morphological classification of its central region. While previous studies provide a visual classification of a patched area, we used the public code called gal axy S upport V ector M achine (galsvm) and HST /ACS data as well as the WFP2 master catalogue to automatically classify all cluster members up to 1 Mpc. galsvm analyses galaxy morphologies through support vector machine (SVM). From the 231 cluster galaxies, we classified 97 as early types (ETs) and 83 as late types (LTs). The remaining 51 stayed unclassified (or undecided). By cross-matching our results with the existing visual classification, we found an agreement of 81 per cent. In addition to previous Zwcl0024 morphological classifications, 121 of our galaxies were classified for the first time in this work. In addition, we tested the location of classified galaxies on the standard morphological diagrams, colour–colour and colour–magnitude diagrams. Out of all cluster members, ∼20 per cent are emission-line galaxies, taking into account previous GLACE results. We have verified that the ET fraction is slightly higher near the cluster core and decreases with the clustercentric distance, while the opposite trend has been observed for LT galaxies. We found a higher fraction of ETs (54 per cent) than LTs (46 per cent) throughout the analysed central region, as expected. In addition, we analysed the correlation between the five morphological parameters (Abraham concentration, Bershady–Concelice concentration, asymmetry, Gini, and M20 moment of light) and the clustercentric distance, without finding a clear trend. Finally, as a result of our work, the morphological catalogue of 231 galaxies containing all the measured parameters and the final classification is available in the electronic form of this paper. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
46. Editorial: submission of accepted papers in TEX/LATEX by FTP
- Published
- 1998
- Full Text
- View/download PDF
47. Composite spectra Paper 7: HD 190361
- Author
-
Griffin, R., primary and Griffin, R., additional
- Published
- 1997
- Full Text
- View/download PDF
48. Composite spectra Paper 6: 9 Cygni
- Author
-
Griffin, R. & R., primary and Beggs, D. W., additional
- Published
- 1994
- Full Text
- View/download PDF
49. Photoelectric radial velocities, Paper XIV. Variation of the radial velocity of ε Cygni
- Author
-
Griffin, R. F., primary
- Published
- 1994
- Full Text
- View/download PDF
50. HSTspatially resolved spectra of the accretion disc and gas stream of the nova‐like variable UX Ursae Majoris[This paper]
- Author
-
Baptista, Raymundo, Horne, Keith, Wade, Richard A., Hubeny, Ivan, Long, Knox S., and Rutten, René G. M.
- Abstract
Time‐resolved eclipse spectroscopy of the nova‐like variable UX UMa obtained with the HST/FOS on 1994 August and November is analysed with eclipse mapping techniques to produce spatially resolved spectra of its accretion disc and gas stream as a function of distance from the disc centre. The inner accretion disc is characterized by a blue continuum filled with absorption bands and lines, which cross over to emission with increasing disc radius, similar to that reported by Rutten et al. at optical wavelengths. The comparison of spatially resolved spectra at different azimuths reveals a significant asymmetry in the disc emission at ultraviolet (UV) wavelengths, with the disc side closest to the secondary star showing pronounced absorption by an ‘iron curtain’ and a Balmer jump in absorption. These results suggest the existence of an absorbing ring of cold gas whose density and/or vertical scale increase with disc radius. The spectrum of the infalling gas stream is noticeably different from the disc spectrum at the same radius suggesting that gas overflows through the impact point at the disc rim and continues along the stream trajectory, producing distinct emission down to 0.1 RL1. The spectrum of the uneclipsed light shows prominent emission lines of Lyα, N vλ 1241, Si ivλ 1400, C ivλ 1550, He iiλ 1640, and Mg iiλ 2800, and a UV continuum rising towards longer wavelengths. The Balmer jump appears clearly in emission indicating that the uneclipsed light has an important contribution from optically thin gas. The lines and optically thin continuum emission are most probably emitted in a vertically extended disc chromosphere + wind. The radial temperature profiles of the continuum maps are well described by a steady‐state disc model in the inner and intermediate disc regions (R≤ 0.3 RL1). There is evidence of an increase in the mass accretion rate from August to November (from M.= 10−8.3 ± 0.1to 10−8.1 ± 0.1M⊙ yr−1), in accordance with the observed increase in brightness. Since the UX UMa disc seems to be in a high mass accretion, high‐viscosity regime in both epochs, this result suggests that the mass transfer rate of UX UMa varies substantially (≃ 50 per cent) on time‐scales of a few months. It is suggested that the reason for the discrepancies between the prediction of the standard disc model and observations is not an inadequate treatment of radiative transfer in the disc atmosphere, but rather the presence of additional important sources of light in the system besides the accretion disc (e.g. optically thin continuum emission from the disc wind and possible absorption by circumstellar cool gas).
- Published
- 1998
- Full Text
- View/download PDF
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