المؤلفون: Lam, Rex, Sandquist, Eric L., Schaefer, Gail H., Farrington, Christopher D., Monnier, John D., Anugu, Narsireddy, Lanthermann, Cyprien, Klement, Robert, Ennis, Jacob, Setterholm, Benjamin R., Gardner, Tyler, Kraus, Stefan, Davies, Claire L., Orosz, Jerome A.

مصطلحات موضوعية: Astrophysics - Solar and Stellar Astrophysics

الوصف: We present measurements of the interferometrically-resolved binary star system 12 Com and the single giant star 31 Com in the cluster Coma Berenices. 12 Com is a double-lined spectroscopic binary system consisting of a G7 giant and an A3 dwarf at the cluster turnoff. Using an extensive radial velocity dataset and interferometric measurements from PTI and the CHARA array, we measured masses $M_1 =2.64 \pm 0.07 M_\odot$ and $M_2 =2.10 \pm 0.03 M_\odot$. Interferometry also allows us to resolve the giant, and measure its size as $R_1 = 9.12 \pm 0.12 \pm 0.01 R_\odot$. With the measured masses and radii, we find an age of $533 \pm 41 \pm 42$ Myr. For comparison, we measure the radius of 31 Com to be $8.36 \pm 0.15 R_\odot$. Based on the photometry and radius measurements, 12 Com A is likely the most evolved bright star in the cluster, large enough to be in the red giant phase, but too small to have core helium burning. Simultaneous knowledge of 12 Com A's mass and photometry puts strong constraints on convective core overshooting during the main sequence phase, which in turn reduces systematic uncertainties in the age. Increased precision in measuring this system also improves our knowledge of the progenitor of the cluster white dwarf WD1216+260.

الوصول الحر: http://arxiv.org/abs/2304.07397Test

المؤلفون: Sandquist, Eric L., Buckner, Andrew J., Shetrone, Matthew D., Barden, Samuel C., Pilachowski, Catherine A., Deliyannis, Constantine P., Harmer, Dianne, Mathieu, Robert, Meibom, Soren, Frandsen, Soren, Orosz, Jerome A.

مصطلحات موضوعية: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies

الوصف: We present analyses of improved photometric and spectroscopic observations for two detached eclipsing binaries at the turnoff of the open cluster NGC 752: the 1.01 day binary DS And and the 15.53 d BD $+$37 410. For DS And, we find $M_1 = 1.692\pm0.004\pm0.010 M_\odot$, $R_1 = 2.185\pm0.004\pm0.008 R_\odot$, $M_2 = 1.184\pm0.001\pm0.003 M_\odot$, and $R_2 = 1.200\pm0.003\pm0.005 R_\odot$. We either confirm or newly identify unusual characteristics of both stars in the binary: the primary star is found to be slightly hotter than the main sequence turn off and there is a more substantial discrepancy in its luminosity compared to models (model luminosities are too large by about 40%), while the secondary star is oversized and cooler compared to other main sequence stars in the same cluster. The evidence points to non-standard evolution for both stars, but most plausible paths cannot explain the low luminosity of the primary star. BD $+$37 410 only has one eclipse per cycle, but extensive spectroscopic observations and the TESS light curve constrain the stellar masses well: $M_1 = 1.717\pm0.011 M_\odot$ and $M_2 = 1.175\pm0.005 M_\odot$. The radius of the main sequence primary star near $2.9R_\odot$ definitively requires large convective core overshooting ($> 0.2$ pressure scale heights) in models for its mass, and multiple lines of evidence point toward an age of $1.61\pm0.03\pm0.05$ Gyr (statistical and systematic uncertainties). Because NGC 752 is currently undergoing the transition from non-degenerate to degenerate He ignition of its red clump stars, BD $+$37 410 A directly constrains the star mass where this transition occurs.
Comment: 34 pages, 23 figures, accepted for Astronomical Journal

الوصول الحر: http://arxiv.org/abs/2210.11649Test

المؤلفون: Morales, Leslie M., Sandquist, Eric L., Schaefer, Gail H., Farrington, Christopher D., Klement, Robert, Bedin, Luigi R., Libralato, Mattia, Malavolta, Luca, Nardiello, Domenico, Orosz, Jerome A., Monnier, John D., Kraus, Stefan, Bouquin, Jean-Baptiste Le, Anugu, Narsireddy, Brummelaar, Theo Ten, Davies, Claire L., Ennis, Jacob, Gardner, Tyler, Lanthermann, Cyprien

مصطلحات موضوعية: Astrophysics - Solar and Stellar Astrophysics

الوصف: We observe the brightest member of the Praesepe cluster, Epsilon Cancri, to precisely measure the characteristics of the stars in this binary system, en route to a new measurement of the cluster's age. We present spectroscopic radial velocity measurements and interferometric observations of the sky-projected orbit to derive the masses, which we find to be M_1/M_sun = 2.420 +/- 0.008 and M_2/M_sun = 2.226 +/- 0.004. We place limits on the color-magnitude positions of the stars by using spectroscopic and interferometric luminosity ratios while trying to reproduce the spectral energy distribution of Epsilon Cancri. We re-examine the cluster membership of stars at the bright end of the color-magnitude diagram using Gaia data and literature radial velocity information. The binary star data are consistent with an age of 637 +/- 19 Myr, as determined from MIST model isochrones. The masses and luminosities of the stars appear to select models with the most commonly used amount of convective core overshooting.
Comment: 46 pages, 15 figures

الوصول الحر: http://arxiv.org/abs/2205.10690Test

المؤلفون: Sandquist, Eric L., Latham, David W., Mathieu, Robert. D., Leiner, Emily, Vanderburg, Andrew, Stello, Dennis, Orosz, Jerome A., Bedin, Luigi R., Libralato, Mattia, Malavolta, Luca, Nardiello, Domenico

مصطلحات موضوعية: Astrophysics - Solar and Stellar Astrophysics

الوصف: We present a study of the bright detached eclipsing main sequence binary WOCS 11028 (Sanders 617) in the open cluster M67. Although the binary has only one eclipse per orbital cycle, we show that the masses of the stars can be derived very precisely thanks to a strong constraint on the orbital inclination: $M_A = 1.222\pm0.006 M_\odot$ and $M_B = 0.909\pm0.004 M_\odot$. We use a spectral energy distribution fitting method to derive characteristics of the component stars in lieu of the precise radii that would normally be derived from a doubly-eclipsing binary. The deconvolution of the SEDs reveals that the brighter component of the binary is at the faint turnoff point for the cluster -- a distinct evolutionary point that occurs after the convective core has been established and while the star is in the middle of its movement toward lower surface temperature, before the so-called hook at the end of main sequence. The measurements are in distinct disagreement with evolution models at solar metallicity: higher metal abundances are needed to reproduce the characteristics of WOCS 11028 A. We discuss the changes to model physics that are likely to be needed to address the discrepancies. The clearest conclusions are that diffusion is probably necessary to reconcile spectroscopic abundances of M67 stars with the need for higher metallicity models, and that reduced strength convective overshooting is occurring for stars at the turnoff. At super-solar bulk metallicity, various indicators agree on a cluster age between about 3.5 and 4.0 Gyr.
Comment: 31 pages, 20 figures, accepted for AJ

الوصول الحر: http://arxiv.org/abs/2011.08365Test

المؤلفون: Sandquist, Eric L., Stello, Dennis, Arentoft, Torben, Brogaard, Karsten, Grundahl, Frank, Vanderburg, Andrew, Hedlund, Anne, DeWitt, Ryan, Ackerman, Taylor R., Aguilar, Miguel, Buckner, Andrew J., Juarez, Christian, Ortiz, Arturo J., Richarte, David, Rivera, Daniel I., Schlapfer, Levi

مصطلحات موضوعية: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies

الوصف: We present a survey of variable stars detected in K2 Campaign 13 within the massive intermediate age ($\sim1$ Gyr) open cluster NGC 1817. We identify a complete sample of 44 red clump stars in the cluster, and have measured asteroseismic quantities ($\nu_{\rm max}$ and/or $\Delta \nu$) for 29 of them. Five stars showed suppressed dipole modes, and the occurrence rates indicate that mode suppression is unaffected by evolution through core helium burning. A subset of the giants in NGC 1817 (and in the similarly aged cluster NGC 6811) have $\nu_{\rm max}$ and $\Delta \nu$ values at or near the maximum observed for core helium burning stars, indicating they have core masses near the minimum for fully non-degenerate helium ignition. Further asteroseismic study of these stars can constrain the minimum helium core mass in red clump stars and the physics that determines this limit. Two giant stars show photometric variations on timescales similar to previously measured spectroscopic orbits. Thirteen systems in the field show eclipses, but only five are probable cluster members. We identify 32 $\delta$ Sct pulsators, 27 $\gamma$ Dor candidates, and 7 hybrids that are probable cluster members, with most new detections. We used the ensemble properties of the $\delta$ Sct stars to identify stars with possible radial pulsation modes. Among the oddities we have uncovered are: an eccentric orbit for a short-period binary containing a $\delta$ Sct pulsating star; a rare subgiant within the Hertzsprung gap showing $\delta$ Sct pulsations; and two hot $\gamma$ Dor pulsating star candidates.
Comment: Accepted to AJ. 28 pages, 25 figures, 5 tables

الوصول الحر: http://arxiv.org/abs/2001.01839Test

المؤلفون: Buckner, Andrew J., Sandquist, Eric L.

مصطلحات موضوعية: Astrophysics - Solar and Stellar Astrophysics

الوصف: We identify a likely member of the NGC 752 open cluster (based on Gaia DR2 proper motions and parallax) having photometry consistent with being a white dwarf and a relatively low-mass main sequence star. If confirmed, this would be the first white dwarf known in this nearby cluster, and the brightest.
Comment: 2 pages, 1 figure, accepted to RNAAS

الوصول الحر: http://arxiv.org/abs/1808.05718Test

المؤلفون: Sandquist, Eric L., Mathieu, Robert D., Quinn, Samuel N., Pollack, Maxwell L., Latham, David W., Brown, Timothy M., Esselstein, Rebecca, Aigrain, Suzanne, Parviainen, Hannu, Vanderburg, Andrew, Stello, Dennis, Somers, Garrett, Pinsonneault, Marc H., Tayar, Jamie, Orosz, Jerome A., Bedin, Luigi R., Libralato, Mattia, Malavolta, Luca, Nardiello, Domenico

مصطلحات موضوعية: Astrophysics - Solar and Stellar Astrophysics

الوصف: We present an analysis of a slightly eccentric ($e=0.05$), partially eclipsing long-period ($P = 69.73$ d) main sequence binary system (WOCS 12009, Sanders 1247) in the benchmark old open cluster M67. Using Kepler K2 and ground-based photometry along with a large set of new and reanalyzed spectra, we derived highly precise masses ($1.111\pm0.015$ and $0.748\pm0.005 M_\odot$) and radii ($1.071\pm0.008\pm0.003$ and $0.713\pm0.019\pm0.026 R_\odot$, with statistical and systematic error estimates) for the stars. The radius of the secondary star is in agreement with theory. The primary, however, is approximately $15\%$ smaller than reasonable isochrones for the cluster predict. Our best explanation is that the primary star was produced from the merger of two stars, as this can also account for the non-detection of photospheric lithium and its higher temperature relative to other cluster main sequence stars at the same $V$ magnitude. To understand the dynamical characteristics (low measured rotational line broadening of the primary star and the low eccentricity of the current binary orbit), we believe that the most probable (but not the only) explanation is the tidal evolution of a close binary within a primordial triple system (possibly after a period of Kozai-Lidov oscillations), leading to merger approximately 1Gyr ago. This star appears to be a future blue straggler that is being revealed as the cluster ages and the most massive main sequence stars die out.
Comment: 33 pages, 11 figures, accepted to AJ, photometry files will be available with the electronic journal article

الوصول الحر: http://arxiv.org/abs/1802.05854Test

المؤلفون: Sandquist, Eric L., Buckner, Andrew J., Shetrone, Matthew D., Barden, Samuel C., Pilachowski, Catherine A., Deliyannis, Constantine P., Harmer, Dianne, Mathieu, Robert, Meibom, Søren, Frandsen, Søren, Orosz, Jerome A.

المصدر: Sandquist , E L , Buckner , A J , Shetrone , M D , Barden , S C , Pilachowski , C A , Deliyannis , C P , Harmer , D , Mathieu , R , Meibom , S , Frandsen , S & Orosz , J A 2023 , ' Evolved Eclipsing Binaries and the Age of the Open Cluster NGC 752* * Based on observations made with with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen. ' ....

الوصف: We present analyses of improved photometric and spectroscopic observations for two detached eclipsing binaries at the turnoff of the open cluster NGC 752: the 1.01 days binary DS And and the 15.53 days BD +37 410. For DS And, we find M 1 = 1.692 ± 0.004 ± 0.010M ⊙ , R 1 = 2.185 ± 0.004 ± 0.008R ⊙ , M 2 = 1.184 ± 0.001 ± 0.003M ⊙ , and R 2 = 1.200 ± 0.003 ± 0.005R ⊙ . We either confirm or newly identify unusual characteristics of both stars in the binary: the primary star is found to be slightly hotter than the main-sequence turnoff and there is a more substantial discrepancy in its luminosity compared to models (model luminosities are too large by about 40%), while the secondary star is oversized and cooler compared to other main-sequence stars in the same cluster. The evidence points to nonstandard evolution for both stars, but most plausible paths cannot explain the low luminosity of the primary star. BD +37 410 only has one eclipse per cycle, but extensive spectroscopic observations and the Transiting Exoplanet Survey Satellite light curve constrain the stellar masses well: M 1 = 1.717 ± 0.011M ⊙ and M 2 = 1.175 ± 0.005M ⊙ . The radius of the main-sequence primary star near 2.9R ⊙ definitively requires large convective core overshooting (>0.2 pressure scale heights) in models for its mass, and multiple lines of evidence point toward an age of 1.61 ± 0.03 ± 0.05 Gyr (statistical and systematic uncertainties). Because NGC 752 is currently undergoing the transition from nondegenerate to degenerate He ignition of its red clump stars, BD +37 410 A directly constrains the star mass where this transition occurs.

العلاقة: https://pure.au.dk/portal/en/publications/0937b91b-fc66-473c-9656-fddabe9cd23dTest

الإتاحة: https://doi.org/10.3847/1538-3881/ac9c59Test
https://pure.au.dk/portal/en/publications/0937b91b-fc66-473c-9656-fddabe9cd23dTest
http://www.scopus.com/inward/record.url?scp=85144014096&partnerID=8YFLogxKTest

المؤلفون: Bavarsad, Ernest A., Sandquist, Eric L., Shetrone, Matthew D., Orosz, Jerome A.

مصطلحات موضوعية: Astrophysics - Solar and Stellar Astrophysics

الوصف: We present an extensive set of photometry and radial velocities for the detached eclipsing binary KV 29 in the intermediate-aged open cluster M11 (NGC 6705). Spectroscopy shows that the system is double-lined and all available evidence (proper motion, photometry, and position on the CMD) indicates it is a member of the cluster. We find the period of the binary to be $4.64276\pm0.00001$ days. We find masses $3.604^{+0.002}_{-0.011}M_\odot$ and $1.837^{+0.001}_{-0.006}M_\odot$, and radii $5.392^{+0.018}_{-0.035}R_\odot$ and $1.656^{+0.007}_{-0.044}R_\odot$ for the primary and secondary stars, respectively. Because the primary star in the binary is rapidly evolving and is brighter than the cluster turnoff in a color-magnitude diagram, the measurement of its radius leads to a strong constraint on the cluster age. We find the age of M11 to be $222^{+2}_{-3}\pm15$ Myr, where the quoted uncertainties come from statistical errors in the calculated masses and radii, and systematic uncertainties due to the ambiguity of the metallicity of the open cluster and variations within the isochrone models concerning heavy elements and convective overshooting.
Comment: 31 pages, 11 figures, accepted to ApJ

الوصول الحر: http://arxiv.org/abs/1608.05190Test

المؤلفون: Sandquist, Eric L., Jessen-Hansen, J., Shetrone, Matthew D., Brogaard, Karsten, Meibom, Soren, Leitner, Marika, Stello, Dennis, Bruntt, Hans, Antoci, Victoria, Orosz, Jerome A., Grundahl, Frank, Frandsen, Soren

مصطلحات موضوعية: Astrophysics - Solar and Stellar Astrophysics

الوصف: We present the analysis of an eccentric, partially eclipsing long-period ($P=19.23$ d) binary system KIC 9777062 that contains main sequence stars near the turnoff of the intermediate age open cluster NGC 6811. The primary is a metal-lined Am star with a possible convective blueshift to its radial velocities, and one star (probably the secondary) is likely to be a $\gamma$ Dor pulsator. The component masses are $1.603\pm0.006$(stat.)$\pm0.016$(sys.) and $1.419\pm0.003\pm0.008 M_\odot$, and the radii are $1.744\pm0.004\pm0.002$ and $1.544\pm0.002\pm0.002 R_\odot$. The isochrone ages of the stars are mildly inconsistent: the age from the mass-radius combination for the primary ($1.05\pm0.05\pm0.09$ Gyr, where the last quote was systematic uncertainty from models and metallicity) is smaller than that from the secondary ($1.21\pm0.05\pm0.15$ Gyr) and is consistent with the inference from the color-magnitude diagram ($1.00\pm0.05$ Gyr). We have improved the measurements of the asteroseismic parameters $\Delta \nu$ and $\nu_{\rm max}$ for helium-burning stars in the cluster. The masses of the stars appear to be larger (or alternately, the radii appear to be smaller) than predicted from isochrones using the ages derived from the eclipsing stars. The majority of stars near the cluster turnoff are pulsating stars: we identify a sample of 28 $\delta$ Sct, 15 $\gamma$ Dor, and 5 hybrid types. We used the period-luminosity relation for high-amplitude $\delta$ Sct stars to fit the ensemble of the strongest frequencies for the cluster members, finding $(m-M)_V = 10.37\pm0.03$. This is larger than most previous determinations, but smaller than values derived from the eclipsing binary ($10.47\pm0.05$).
Comment: 33 pages, 16 figures, 1 electronic table, accepted for ApJ

الوصول الحر: http://arxiv.org/abs/1608.03917Test