25 results on '"Natalie M. Gosnell"'
Search Results
2. Supporting Inclusive Teaching in Introductory College Physics
- Author
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Joseph A. Taylor, Stephen R. Getty, Barbara L. Whitten, and Natalie M. Gosnell
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African american ,media_common.quotation_subject ,Physics education ,Mathematics education ,medicine ,General Physics and Astronomy ,Attrition ,Gateway (computer program) ,medicine.disease ,Female students ,Education ,Diversity (politics) ,media_common - Abstract
Even among the sciences, physics stands out as an unusually White- and male-dominated field. The American Institute of Physics (AIP) reports that only 19% of physics faculty are women, and less than 6% of physics faculty are African American or Hispanic. Particularly for female students, the transition from high school to a college major in physics has been identified as the most important point of attrition. As such, undergraduate physics education is a critical juncture where these trends can be interrupted. We approached this problem by using teaching strategies intended to promote inclusiveness in a calculus-based, introductory college physics course, a key requirement in many STEM majors and a gateway to the undergraduate physics major. Proponents of inclusive teaching strategies argue that using such strategies will benefit all students, particularly those from marginalized groups, increase the diversity of physics majors, and ultimately contribute to a more diverse community of physicists.
- Published
- 2020
3. Revealing the Field Sub-subgiant Population Using a Catalog of Active Giant Stars and Gaia EDR3
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Emily M. Leiner, Aaron M. Geller, Michael A. Gully-Santiago, Natalie M. Gosnell, and Benjamin M. Tofflemire
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Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics - Astrophysics of Galaxies ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
Sub-subgiant stars (SSGs) fall below the subgiant branch and/or red of the giant branch in open and globular clusters, an area of the color-magnitude diagram (CMD) not populated by standard stellar evolution tracks. One hypothesis is that SSGs result from rapid rotation in subgiants or giants due to tidal synchronization in a close binary. The strong magnetic fields generated inhibit convection, which in turn produces large starspots, radius inflation, and lower-than-expected average surface temperatures and luminosities. Here we cross-reference a catalog of active giant binaries (RS CVns) in the field with Gaia EDR3. Using the Gaia photometry and parallaxes we precisely position the RS CVns in a CMD. We identify stars that fall below a 14 Gyr, metal-rich isochrone as candidate field SSGs. Out of a sample of 1723 RS CVn, we find 448 SSG candidates, a dramatic expansion from the 65 SSGs previously known. Most SSGs have rotation periods of 2-20 days, with the highest SSG fraction found among RS CVn with the shortest periods. The ubiquity of SSGs among this population indicates SSGs are a normal phase in evolution for RS CVn-type systems, not rare by-products of dynamical encounters found only in dense star clusters as some have suggested. We present our catalog of 1723 active giants, including Gaia photometry and astrometry, and rotation periods from TESS and VSX. This catalog can serve as an important sample to study the impacts of magnetic fields in evolved stars., 16 pages, 7 Figures, 1 Table. Accepted for publication in ApJ
- Published
- 2021
4. Three K2 Campaigns Yield Rotation Periods for 1013 Stars in Praesepe
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Jason L. Curtis, Nicholas M. Law, Phillip A. Cargile, Marcel A. Agüeros, Stephanie T. Douglas, Natalie M. Gosnell, Kevin R. Covey, Alejandro Núñez, Adam L. Kraus, Rayna Rampalli, and Andrew W. Mann
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Physics ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Rotation ,Light curve ,Solar and Stellar Astrophysics (astro-ph.SR) ,Open cluster - Abstract
We use three campaigns of K2 observations to complete the census of rotation in low-mass members of the benchmark, $\approx$670-Myr-old open cluster Praesepe. We measure new rotation periods (\prot) for 220 $\lesssim$1.3~\Msun\ Praesepe members and recover periods for $97\%$ (793/812) of the stars with a \prot\ in the literature. Of the 19 stars for which we do not recover a \prot, 17 were not observed by K2. As K2's three Praesepe campaigns took place over the course of three years, we test the stability of our measured \prot\ for stars observed in more than one campaign. We measure \prot\ consistent to within $10\%$ for $>95\%$ of the 331 likely single stars with $\geq$2 high-quality observations; the median difference in \prot\ is $0.3\%$, with a standard deviation of $2\%$. Nearly all of the exceptions are stars with discrepant \prot\ measurements in Campaign 18, K2's last, which was significantly shorter than the earlier two ($\approx$50~d rather than $\approx$75~d). This suggests that, despite the evident morphological evolution we observe in the light curves of $38\%$ of the stars, \prot\ measurements for low-mass stars in Praesepe are stable on timescales of several years. A \prot\ can therefore be taken to be representative even if measured only once., 19 pages, 13 figures, 6 tables. Accepted in ApJ
- Published
- 2021
- Full Text
- View/download PDF
5. Observationally Constraining the Starspot Properties of Magnetically Active M67 Sub-subgiant S1063
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Natalie M. Gosnell, Michael A. Gully-Santiago, Emily M. Leiner, and Benjamin M. Tofflemire
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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
Our understanding of the impact of magnetic activity on stellar evolution continues to unfold. This impact is seen in sub-subgiant stars, defined to be stars that sit below the subgiant branch and red of the main sequence in a cluster color-magnitude diagram. Here we focus on S1063, a prototypical sub-subgiant in open cluster M67. We use a novel technique combining a two-temperature spectral decomposition and light curve analysis to constrain starspot properties over a multi-year time frame. Using a high-resolution near-infrared IGRINS spectrum and photometric data from K2 and ASAS-SN, we find a projected spot filling factor of 32 $\pm$ 7% with a spot temperature of 4000 $\pm$ 200 K. This value anchors the variability seen in the light curve, indicating the spot filling factor of S1063 ranged from 20% to 45% over a four-year time period with an average spot filling factor of 30%. These values are generally lower than those determined from photometric model comparisons but still indicate that S1063, and likely other sub-subgiants, are magnetically active spotted stars. We find observational and theoretical comparisons of spotted stars are nuanced due to the projected spot coverage impacting estimates of the surface-averaged effective temperature. The starspot properties found here are similar to those found in RS CVn systems, supporting classifying sub-subgiants as another type of active giant star binary system. This technique opens the possibility of characterizing the surface conditions of many more spotted stars than previous methods, allowing for larger future studies to test theoretical models of magnetically active stars., Comment: 14 pages, 6 figures, accepted to the Astrophysical Journal
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- 2022
6. Constraining Mass Transfer Histories of Blue Straggler Stars with COS Spectroscopy of White Dwarf Companions
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Christian Knigge, Natalie M. Gosnell, Nathan W. C. Leigh, Robert D. Mathieu, Aaron M. Geller, Alison Sills, and Emily Leiner
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Physics ,010504 meteorology & atmospheric sciences ,Star (game theory) ,White dwarf ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,01 natural sciences ,Blue straggler ,Accretion (astrophysics) ,Red-giant branch ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,13. Climate action ,Space and Planetary Science ,0103 physical sciences ,Binary system ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,0105 earth and related environmental sciences ,Open cluster - Abstract
Recent studies show that the majority of blue straggler stars (BSSs) in old open clusters are formed through mass transfer from an evolved star onto a main-sequence companion, resulting in a BSS and white dwarf (WD) in a binary system. We present constraints on the mass transfer histories of two BSS-WD binaries in the open cluster NGC 188, using WD temperatures and surface gravities measured with HST COS far-ultraviolet spectroscopy. Adopting a Gaia-based cluster distance of $1847\pm107$ pc, we determine that one system, WOCS 4540, formed through Case C mass transfer resulting in a CO-core white dwarf with $T_{\text{eff}}=17000^{+140}_{-200}$ K and a $\log g=7.80^{+0.06}_{-0.06}$, corresponding to a mass of $0.53^{+0.03}_{-0.03}$ $M_{\odot}$ and a cooling age of $105^{+6}_{-5}$ Myr. The other system, WOCS 5379, formed through Case B mass transfer resulting in a He-core white dwarf with $T_{\text{eff}}=15500^{+170}_{-150}$ K and a $\log g=7.50^{+0.06}_{-0.05}$, corresponding to a mass of $0.42^{+0.02}_{-0.02}$ $M_{\odot}$ and an age of $250^{+20}_{-20}$ Myr. The WD parameters are consistent across four different cluster distance assumptions. We determine possible progenitor binary systems with a grid of accretion models using MESA, and investigate whether these systems would lead to stable or unstable mass transfer. WOCS 4540 likely resulted from stable mass transfer during periastron passage in an eccentric binary system, while WOCS 5379 challenges our current understanding of the expected outcomes for mass transfer from red giant branch stars. Both systems are examples of the value in using detailed analyses to fine-tune our physical understanding of binary evolutionary processes., 16 pages, 10 figures, 2 tables, submitted to Astrophysical Journal
- Published
- 2019
7. Constraints on blue straggler formation mechanisms in Galactic globular clusters from proper motion velocity distributions
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Thomas H. Puzia, Quinn E. Minor, Teresa Panurach, J. Ventura, Michael M. Shara, Aaron M. Geller, Christian Knigge, Natalie M. Gosnell, Nathan W. C. Leigh, M. Simunovic, David R. Zurek, Robert D. Mathieu, and Alison Sills
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Physics ,education.field_of_study ,Proper motion ,010308 nuclear & particles physics ,Population ,Binary number ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Star (graph theory) ,Astrophysics - Astrophysics of Galaxies ,01 natural sciences ,Blue straggler ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Globular cluster ,Astrophysics of Galaxies (astro-ph.GA) ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Binary system ,education ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics - Abstract
For a sample of 38 Galactic globular clusters (GCs), we confront the observed distributions of blue straggler (BS) proper motions and masses (derived from isochrone fitting) from the BS catalog of Simunovic & Puzia with theoretical predictions for each of the two main competing BS formation mechanisms. These are mass transfer from an evolved donor on to a main-sequence (MS) star in a close binary system, and direct collisions involving MS stars during binary encounters. We use the \texttt{FEWBODY} code to perform simulations of single-binary and binary-binary interactions. This provides collisional velocity and mass distributions for comparison to the observed distributions. Most clusters are consistent with BSs derived from a dynamically relaxed population, supportive of the binary mass-transfer scenario. In a few clusters, including all the post-core collapse clusters in our sample, the collisional velocities provide the best fit., 10 pages, 8 figures, 1 table; accepted for publication in MNRAS
- Published
- 2019
8. Women in physics in the United States: Reaching toward equity and inclusion
- Author
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Christine Jones, Arlisa Richardson, Kelsey M. Hallinen, Geraldine L. Cochran, Candace Harris, Marta D. McNeese, Sathya Guruswamy, Tennille D. Presley, Nicole L. Campbell, Jessica Esquivel, Chandralekha Singh, Natalie M. Gosnell, Laura McCullough, Sally Seidel, Robin Bjorkquist, Nicole Quist, Laura Gladstone, Beth Cunningham, Angela Johnson, Jolene L Johnson, Regina A. Jorgenson, Mary K. Chessey, and Abigail M. Bogdan
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Stereotype threat ,Equity (economics) ,business.industry ,Excellence ,media_common.quotation_subject ,Harassment ,Human sexuality ,Professional association ,Public relations ,business ,Social class ,Social equality ,media_common - Abstract
The United States has a major deficit in the proportion of women earning degrees in physics, peaking around 20%. To promote excellence and maximize creativity, additional efforts to diversify the physics community must be implemented. Challenges to improving the proportion of female physicists include microaggressions, active discouragement, poor advising or mentoring, inadequate acknowledgement of achievements, sexual harassment, and many others. The latest research on gender bias suggests two main underlying psychological themes that explain much of the behavioral bias: implicit (unconscious) bias and stereotype threat. To ensure that excellence is not compromised, we need to guarantee that our entire population has access to adequate resources and the necessary support structures for success. To fully understand women in physics, we must also examine the many obstacles that women of various identities face in efforts to navigate their academic and professional careers. These identities may be related not only to gender but also to race, ethnicity, language, religion, social class, or sexuality. Increasing women’s participation in physics requires increased access to high school physics courses, funding opportunities to attend college, availability of research opportunities, and access to and support from professional societies. These approaches will enhance the culture in physics, leading to gender equity, social equity, and improved social justice for many people.
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- 2019
9. Effective Temperatures of Low-Mass Stars from High-Resolution H-band Spectroscopy
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Heeyoung Oh, Aurora Y. Kesseli, Philip S. Muirhead, Daniel T. Jaffe, Gregory N. Mace, Benjamin Kidder, Maryam Hussaini, Andrew W. Mann, Christopher M. Johns-Krull, Ricardo López-Valdivia, Natalie M. Gosnell, and Kimberly R. Sokal
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Physics ,010504 meteorology & atmospheric sciences ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Effective temperature ,01 natural sciences ,Exoplanet ,Spectral line ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Planet ,0103 physical sciences ,TW Hydrae ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Spectroscopy ,Low Mass ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,0105 earth and related environmental sciences - Abstract
High-resolution, near-infrared spectra will be the primary tool for finding and characterizing Earth-like planets around low-mass stars. Yet, the properties of exoplanets can not be precisely determined without accurate and precise measurements of the host star. Spectra obtained with the Immersion GRating INfrared Spectrometer (IGRINS) simultaneously provide diagnostics for most stellar parameters, but the first step in any analysis is the determination of the effective temperature. Here we report the calibration of high-resolution H-band spectra to accurately determine effective temperature for stars between 4000-3000 K ($\sim$K8--M5) using absorption line depths of Fe I, OH, and Al I. The field star sample used here contains 254 K and M stars with temperatures derived using BT-Settl synthetic spectra. We use 106 stars with precise temperatures in the literature to calibrate our method with typical errors of about 140 K, and systematic uncertainties less than $\sim$120 K. For the broadest applicability, we present T$_{\rm eff}$--line-depth-ratio relationships, which we test on 12 members of the TW Hydrae Association and at spectral resolving powers between $\sim$10,000--120,000. These ratios offer a simple but accurate measure of effective temperature in cool stars that is distance and reddening independent., Comment: 19 pages, 11 figures and 3 tables. Accepted in ApJ
- Published
- 2019
- Full Text
- View/download PDF
10. Blue Straggler Stars: A Window Into Alternative Pathway Stellar Products
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Natalie M. Gosnell
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Physics ,Stars ,Window (computing) ,Astrophysics ,Blue straggler - Published
- 2016
11. Implications for the Formation of Blue Straggler Stars from HST Ultraviolet Observations of NGC 188
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Christian Knigge, Nathan W. C. Leigh, Robert D. Mathieu, Aaron M. Geller, Alison Sills, and Natalie M. Gosnell
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Physics ,education.field_of_study ,010308 nuclear & particles physics ,Population ,FOS: Physical sciences ,White dwarf ,Astronomy and Astrophysics ,Astrophysics ,01 natural sciences ,Blue straggler ,Star cluster ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,0103 physical sciences ,Binary star ,Asymptotic giant branch ,Roche lobe ,education ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Open cluster - Abstract
We present results of a Hubble Space Telescope far-ultraviolet (FUV) survey searching for white dwarf (WD) companions to blue straggler stars (BSSs) in open cluster NGC 188. The majority of NGC 188 BSSs (15 of 21) are single-lined binaries with properties suggestive of mass-transfer formation via Roche lobe overflow, specifically through an asymptotic giant branch star transferring mass to a main sequence secondary, yielding a BSS binary with a WD companion. In NGC 188, a BSS formed by this mechanism within the past 400 Myr will have a WD companion hot and luminous enough to be directly detected as a FUV photometric excess with HST. Comparing expected BSS FUV emission to observed photometry reveals four BSSs with WD companions above 12,000 K (younger than 250 Myr) and three WD companions with temperatures between 11,000-12,000 K. These BSS+WD binaries all formed through recent mass transfer. The location of the young BSSs in an optical color-magnitude diagram (CMD) indicates that distance from the zero-age main sequence does not necessarily correlate with BSS age. There is no clear CMD separation between mass transfer-formed BSSs and those likely formed through other mechanisms, such as collisions. The seven detected WD companions place a lower limit on the mass-transfer formation frequency of 33%. We consider other possible formation mechanisms by comparing properties of the BSS population to theoretical predictions. We conclude that 14 BSS binaries likely formed from mass transfer, resulting in an inferred mass-transfer formation frequency of approximately 67%., 13 pages, 6 figures, accepted to the Astrophysical Journal
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- 2015
12. WIYN Open Cluster Study. LIX. Radial-Velocity Membership of the Evolved Population of the Old Open Cluster NGC 6791
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Imants Platais, Natalie M. Gosnell, Benjamin M. Tofflemire, and Robert D. Mathieu
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Physics ,Proper motion ,010504 meteorology & atmospheric sciences ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Horizontal branch ,01 natural sciences ,Blue straggler ,Red-giant branch ,Radial velocity ,Star cluster ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,0103 physical sciences ,010303 astronomy & astrophysics ,Red clump ,Solar and Stellar Astrophysics (astro-ph.SR) ,0105 earth and related environmental sciences ,Open cluster - Abstract
The open cluster NGC 6791 has been the focus of much recent study due to its intriguing combination of old age and high metallicity ($\sim$8 Gyr, [Fe$/$H]=$+$0.30), as well as its location within the Kepler field. As part of the WIYN Open Cluster Study, we present precise ($\sigma=0.38$ km s$^{-1}$) radial velocities for proper-motion candidate members of NGC 6791 from Platais et al. Our survey, extending down to $g^\prime\sim16.8$, is comprised of the evolved cluster population, including blue stragglers, giants, and horizontal branch stars. Of the 280 proper-motion-selected stars above our magnitude limit, 93% have at least one radial-velocity measurement and 79% have three measurements over the course of at least 200 days, sufficient for secure radial-velocity-determined membership of non-velocity-variable stars. The Platais et al. proper-motion catalog includes twelve anomalous horizontal branch candidates blueward of the red clump, of which we find only four to be cluster members. Three fall slightly blueward of the red clump and the fourth is consistent with being a blue straggler. The cleaned color-magnitude diagram shows a richly populated red giant branch and a blue straggler population. Half of the blue stragglers are in binaries. From our radial-velocity measurement distribution we find the cluster's radial-velocity dispersion to be $\sigma_c=0.62\pm0.10$ km s$^{-1}$. This corresponds to a dynamical mass of $\sim$4600 $M_\odot$., Comment: Accepted to The Astrophysical Journal July 28th, 2014. 12 pages, 8 figures, 5 tables
- Published
- 2014
13. TODAY A DUO, BUT ONCE A TRIO? THE DOUBLE WHITE DWARF HS 2220+2146 MAY BE A POST-BLUE STRAGGLER BINARY
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Detlev Koester, Alexandros Gianninas, Warren R. Brown, Marcel A. Agüeros, Natalie M. Gosnell, Jeff J. Andrews, and Mukremin Kilic
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Physics ,010308 nuclear & particles physics ,FOS: Physical sciences ,Binary number ,White dwarf ,Astronomy and Astrophysics ,Astrophysics ,01 natural sciences ,Blue straggler ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,0103 physical sciences ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
For sufficiently wide orbital separations {\it a}, the two members of a stellar binary evolve independently. This implies that in a wide double white dwarf (DWD), the more massive WD should always be produced first, when its more massive progenitor ends its main-sequence life, and should therefore be older and cooler than its companion. The bound, wide DWD HS 2220$+$2146 ($a\approx500$ AU) does not conform to this picture: the more massive WD is the younger, hotter of the pair. We show that this discrepancy is unlikely to be due to past mass-transfer phases or to the presence of an unresolved companion. Instead, we propose that HS 2220$+$2146 formed through a new wide DWD evolutionary channel involving the merger of the inner binary in a hierarchical triple system. The resulting blue straggler and its wide companion then evolved independently, forming the WD pair seen today. Although we cannot rule out other scenarios, the most likely formation channel has the inner binary merging while both stars are still on the main sequence. This provides us with the tantalizing possibility that Kozai-Lidov oscillations may have played a role in the inner binary's merger. {\it Gaia} may uncover hundreds more wide DWDs, leading to the identification of other systems like HS 2220$+$2146. There are already indications that other WD systems may have been formed through different, but related, hierarchical triple evolutionary scenarios. Characterizing these populations may allow for thorough testing of the efficiency with which KL oscillations induce stellar mergers., Accepted for publication in ApJ, 12 pages, 6 figures, 2 tables
- Published
- 2016
14. WIYN OPEN CLUSTER STUDY. LXVI. SPECTROSCOPIC BINARY ORBITS IN THE YOUNG OPEN CLUSTER M35 (NGC 2168)
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Natalie M. Gosnell, Emily Leiner, Robert D. Mathieu, and Aaron M. Geller
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Physics ,education.field_of_study ,Population ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Pseudorandom binary sequence ,Blue straggler ,Stars ,Star cluster ,Space and Planetary Science ,Cluster (physics) ,Astrophysics::Solar and Stellar Astrophysics ,education ,Astrophysics::Galaxy Astrophysics ,Galaxy cluster ,Open cluster - Abstract
The young (150 Myr) open cluster M35 (NGC 2168) has been one of the core clusters of the WIYN Open Cluster Study since 1997. Over these 17 years we have obtained approximately 8000 radial-velocity (RV) measurements of stars in the M35 field, which we provide here. Our target sample consists of 1355 photometrically selected stars in the field of M35 within the main sequence and binary sequence of the cluster and within and . Using our RV measurements we cleanly separate likely cluster members from field stars. We calculate RV membership probabilities for over 1200 stars in our sample. 418 are probable cluster members, of which 64 are velocity-variable (binary) systems. Here we present 52 orbital solutions for binary members of M35. This sample defines the hard binary population of M35 that dynamically powers the cluster. We also present XMM-Newton X-ray detections within the cluster. We use our large binary sample to search for interacting binaries among the X-ray sources, investigate M35's period?eccentricity distribution, and determine binary frequency. We find a circularization period of 9.9 ? 1.2 days and a binary frequency of 24% ? 3% for main-sequence binaries with days. Determining these properties in a young cluster like M35 is key to defining the initial conditions used in models of cluster dynamical evolution.
- Published
- 2015
15. WIYN OPEN CLUSTER STUDY. LX. SPECTROSCOPIC BINARY ORBITS IN NGC 6819
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Natalie M. Gosnell, Søren Meibom, Aaron M. Geller, Imants Platais, Katelyn E. Milliman, and Robert D. Mathieu
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Physics ,010308 nuclear & particles physics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,01 natural sciences ,Asteroseismology ,Blue straggler ,Radial velocity ,Stars ,Photometry (astronomy) ,Star cluster ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,0103 physical sciences ,010303 astronomy & astrophysics ,Red clump ,Solar and Stellar Astrophysics (astro-ph.SR) ,Open cluster - Abstract
We present the current state of the WOCS radial-velocity (RV) survey for the rich open cluster NGC 6819 (2.5 Gyr) including 93 spectroscopic binary orbits with periods ranging from 1.5 to 8,000 days. These results are the product of our ongoing RV survey of NGC 6819 using the Hydra Multi-Object Spectrograph on the WIYN 3.5 m telescope. We also include a detailed analysis of multiple prior sets of optical photometry for NGC 6819. Within a 1-degree field of view, our stellar sample includes the giant branch, the red clump, and blue straggler candidates, and extends to almost 2 mag below the main-sequence (MS) turnoff. For each star observed in our survey we present all RV measurements, the average RV and velocity variability information. Additionally, we discuss notable binaries from our sample, including eclipsing binaries (WOCS 23009, WOCS 24009, and WOCS 40007), stars noted in Kepler asteroseismology studies (WOCS 4008, WOCS 7009, and WOCS 8007), and potential descendants of past blue stragglers (WOCS 1006 and WOCS 6002). We find the incompleteness-corrected binary fraction for all MS binaries with periods less than 10,000 days to be 22% +/- 3% and a tidal circularization period of 6.2 +/- 1.1 days for NGC 6819., 22 pages, 12 figures
- Published
- 2014
16. DETECTION OF WHITE DWARF COMPANIONS TO BLUE STRAGGLERS IN THE OPEN CLUSTER NGC 188: DIRECT EVIDENCE FOR RECENT MASS TRANSFER
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Alison Sills, Christian Knigge, Natalie M. Gosnell, Aaron M. Geller, Robert D. Mathieu, and Nathan W. C. Leigh
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Physics ,FOS: Physical sciences ,Astronomy ,White dwarf ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Advanced Camera for Surveys ,Blue straggler ,Stars ,Star cluster ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Binary star ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Stellar evolution ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Open cluster - Abstract
Several possible formation pathways for blue straggler stars have been developed recently, but no one pathway has yet been observationally confirmed for a specific blue straggler. Here we report the first findings from a Hubble Space Telescope ACS/SBC far-UV photometric program to search for white dwarf companions to blue straggler stars. We find three hot and young white dwarf companions to blue straggler stars in the 7-Gyr open cluster NGC 188, indicating that mass transfer in these systems ended less than 300 Myr ago. These companions are direct and secure observational evidence that these blue straggler stars were formed through mass transfer in binary stars. Their existence in a well-studied cluster environment allows for observational constraints of both the current binary system and the progenitor binary system, mapping the entire mass transfer history., Comment: 5 pages, 3 figures, accepted for publication in The Astrophysical Journal Letters
- Published
- 2014
17. WIYN OPEN CLUSTER STUDY. LV. ASTROMETRY AND MEMBERSHIP IN NGC 6819
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Natalie M. Gosnell, Vera Kozhurina-Platais, Christian Veillet, Imants Platais, Søren Meibom, Andrea Bellini, and Martin S. Burkhead
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Physics ,Stars ,Star cluster ,Proper motion ,Space and Planetary Science ,Cluster (physics) ,Astronomy ,Astronomy and Astrophysics ,Astrometry ,Astrophysics ,Variable star ,Galaxy cluster ,Open cluster - Abstract
We present proper motions and astrometric membership analysis for 15,750 stars around the intermediate-age open cluster NGC 6819. The accuracy of relative proper motions for well-measured stars ranges from ~0.2 mas yr–1 within 10' of the cluster center to 1.1 mas yr–1 outside this radius. In the proper motion vector-point diagram, the separation between the cluster members and field stars is convincing down to V ~ 18 and within 10' from the cluster center. The formal sum of membership probabilities indicates a total of ~2500 cluster members down to V ~ 22. We confirm the cluster membership of several variable stars, including some eclipsing binaries. The estimated absolute proper motion of NGC 6819 is and mas yr–1. A cross-identification between the proper motion catalog and a list of X-ray sources in the field of NGC 6819 resulted in a number of new likely optical counterparts, including a candidate CV. For the first time we show that there is significant differential reddening toward NGC 6819.
- Published
- 2013
18. AN UNEXPECTED DISCOVERY IN THE RICH OPEN CLUSTER NGC 6819 USINGXMM-NEWTON
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Robert D. Mathieu, Peter M. Frinchaboy, Jason S. Kalirai, Enrico Ramirez-Ruiz, Aaron M. Geller, David Pooley, and Natalie M. Gosnell
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Astrophysics::High Energy Astrophysical Phenomena ,Population ,FOS: Physical sciences ,Cataclysmic variable star ,Astrophysics::Cosmology and Extragalactic Astrophysics ,0102 computer and information sciences ,Astrophysics ,01 natural sciences ,Photometry (optics) ,Observatory ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,education ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Physics ,education.field_of_study ,Astronomy and Astrophysics ,Radial velocity ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,010201 computation theory & mathematics ,Space and Planetary Science ,Globular cluster ,Open cluster - Abstract
We present the first study of the X-ray population of the intermediate-age rich open cluster NGC 6819 using the XMM-Newton Observatory. In the past decade, Chandra X-ray observations have shown a relationship between the X-ray population of globular clusters and their internal dynamics and encounter frequency. We investigate the role dynamics possibly play in the formation of X-ray sources in NGC 6819, and compare our results with known properties of field and globular cluster X-ray populations. We implement a multi wavelength approach to studying the X-ray sources, utilizing X-ray and UV data from XMM observations along with the wealth of photometry and radial-velocity data from the WIYN Open Cluster Study (WOCS) and the CFHT Open Cluster Survey. Within the cluster half-light radius we detect 12 X-ray sources down to a luminosity of 10^30 erg/s for cluster members. The sources include a candidate quiescent low-mass X-ray binary (qLMXB), a candidate cataclysmic variable, and two active binary systems. The presence of a qLMXB in an open cluster is previously unexpected given the known relationships between luminous X-ray sources and encounter frequency in globular clusters, and most likely has a dynamical origin., 14 pages, 11 figures, accepted for publication in the Astrophysical Journal
- Published
- 2011
19. Constraining Mass-transfer Histories of Blue Straggler Stars with COS Spectroscopy of White Dwarf Companions.
- Author
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Natalie M. Gosnell, Emily M. Leiner, Robert D. Mathieu, Aaron M. Geller, Christian Knigge, Alison Sills, and Nathan W. C. Leigh
- Subjects
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WHITE dwarf stars , *EARLY stars , *RED giants , *MASS transfer , *OPEN clusters of stars , *SPACE telescopes - Abstract
Recent studies show that the majority of blue straggler stars (BSSs) in old open clusters are formed through mass transfer from an evolved star onto a main-sequence companion, resulting in a BSS and white dwarf (WD) in a binary system. We present constraints on the mass transfer histories of two BSS–WD binaries in the open cluster NGC 188, using WD temperatures and surface gravities measured with Hubble Space Telescope COS far-ultraviolet spectroscopy. Adopting a Gaia-based cluster distance of 1847 ± 107 pc, we determine that one system, WOCS 4540, formed through Case C mass transfer resulting in a CO-core WD with Teff = K and a log g = , corresponding to a mass of M⊙ and a cooling age of Myr. The other system, WOCS 5379, formed through Case B mass transfer resulting in a He-core WD with Teff = K and a log g = , corresponding to a mass of M⊙ and an age of Myr. The WD parameters are consistent across four different cluster distance assumptions. We determine possible progenitor binary systems with a grid of accretion models using MESA, and investigate whether these systems would lead to stable or unstable mass transfer. WOCS 4540 likely resulted from stable mass transfer during periastron passage in an eccentric binary system, while WOCS 5379 challenges our current understanding of the expected outcomes for mass transfer from red giant branch stars. Both systems are examples of the value in using detailed analyses to fine-tune our physical understanding of binary evolutionary processes. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
20. Blue Lurkers: Hidden Blue Stragglers on the M67 Main Sequence Identified from Their Kepler/K2 Rotation Periods.
- Author
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Emily Leiner, Robert D. Mathieu, Andrew Vanderburg, Natalie M. Gosnell, and Jeffrey C. Smith
- Subjects
STELLAR collisions ,EARLY stars ,ROTATIONAL motion ,STELLAR luminosity function ,OPEN clusters of stars ,STELLAR evolution ,WHITE dwarf stars - Abstract
At an age of 4 Gyr, typical solar-type stars in M67 have rotation rates of 20–30 days. Using K2 Campaign 5 and 16 light curves and the spectral archive of the WIYN Open Cluster Study, we identify 11 3D kinematic members of M67 with anomalously fast rotation periods of 2–8 days, implying ages of less than 1 Gyr. We hypothesize that these anomalously fast rotators have been spun up by mass transfer, mergers, or stellar collisions during dynamical encounters within the 1 Gyr and thus represent lower-luminosity counterparts to the blue straggler stars. These 11 candidate post-interaction stellar systems have much in common with the blue stragglers, including a high binary fraction (73%); a number of long-period, low-eccentricity binary systems; and in at least one case a UV excess consistent with the presence of a hot white dwarf companion. The identification of these 11 systems provides the first picture of the low-luminosity end of the blue straggler distribution, providing new constraints for detailed binary evolution models and cluster population studies. This result also clearly demonstrates the need to properly account for the impact of binaries on stellar evolution, as significant numbers of post-interaction binaries likely exist on cluster main sequences and in the field. These stars are not always easy to identify but make up ∼10% or more of the spectroscopic binary population among the solar-type stars in M67. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
21. Effective Temperatures of Low-mass Stars from High-resolution H-band Spectroscopy.
- Author
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Ricardo López-Valdivia, Gregory N. Mace, Kimberly R. Sokal, Maryam Hussaini, Benjamin T. Kidder, Andrew W. Mann, Natalie M. Gosnell, Heeyoung Oh, Aurora Y. Kesseli, Philip S. Muirhead, Christopher M. Johns-Krull, and Daniel T. Jaffe
- Subjects
TEMPERATURE of stars ,HABITABLE planets ,IR spectrometers ,SPECTRUM analysis - Abstract
High-resolution, near-infrared spectra will be the primary tool for finding and characterizing Earth-like planets around low-mass stars. Yet, the properties of exoplanets cannot be precisely determined without accurate and precise measurements of the host star. Spectra obtained with the Immersion Grating Infrared Spectrometer simultaneously provide diagnostics for most stellar parameters, but the first step in any analysis is the determination of the effective temperature. Here we report the calibration of high-resolution H-band spectra to accurately determine the effective temperature for stars between 4000 and 3000 K (∼K8–M5) using absorption line-depths of Fe i, OH, and Al i. The field star sample used here contains 254 K and M stars with temperatures derived using BT-Settl synthetic spectra. We use 106 stars with precise temperatures in the literature to calibrate our method, with typical errors of about 140 K, and systematic uncertainties less than ∼120 K. For the broadest applicability, we present T
eff –line-depth-ratio relationships, which we test on 12 members of the TW Hydrae Association and at spectral resolving powers between ∼10,000 and 120,000. These ratios offer a simple but accurate measure of effective temperatures in cool stars that are distance and reddening independent. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
22. Observations of Spin-down in Post-mass-transfer Stars and the Possibility for Blue Straggler Gyrochronology.
- Author
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Emily Leiner, Robert D. Mathieu, Natalie M. Gosnell, and Alison Sills
- Published
- 2018
- Full Text
- View/download PDF
23. Wolf 1130: A Nearby Triple System Containing a Cool, Ultramassive White Dwarf.
- Author
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Gregory N. Mace, Andrew W. Mann, Brian A. Skiff, Christopher Sneden, J. Davy Kirkpatrick, Adam C. Schneider, Benjamin Kidder, Natalie M. Gosnell, Hwihyun Kim, Brian W. Mulligan, L. Prato, and Daniel Jaffe
- Subjects
WHITE dwarf stars ,BINARY systems (Astronomy) ,ASTRONOMICAL photometry ,ATOMIC mass ,STAR observations - Abstract
Following the discovery of the T8 subdwarf WISE J200520.38+542433.9 (Wolf 1130C), which has a proper motion in common with a binary (Wolf 1130AB) consisting of an M subdwarf and a white dwarf, we set out to learn more about the old binary in the system. We find that the A and B components of Wolf 1130 are tidally locked, which is revealed by the coherence of more than a year of V-band photometry phase-folded to the derived orbital period of 0.4967 days. Forty new high-resolution, near-infrared spectra obtained with the Immersion Grating Infrared Spectrometer provide radial velocities and a projected rotational velocity (v sin i) of 14.7 ± 0.7 for the M subdwarf. In tandem with a Gaia parallax-derived radius and verified tidal locking, we calculate an inclination of i = 29° ± 2°. From the single-lined orbital solution and the inclination we derive an absolute mass for the unseen primary ( M
⊙ ). Its non-detection between 0.2 and 2.5 μm implies that it is an old (>3.7 Gyr) and cool (Teff < 7000 K) ONe white dwarf. This is the first ultramassive white dwarf within 25 pc. The evolution of Wolf 1130AB into a cataclysmic variable is inevitable, making it a potential SN Ia progenitor. The formation of a triple system with a primary mass >100 times the tertiary mass and the survival of the system through the common-envelope phase, where ∼80% of the system mass was lost, is remarkable. Our analysis of Wolf 1130 allows us to infer its formation and evolutionary history, which has unique implications for understanding low-mass star and brown dwarf formation around intermediate-mass stars. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
24. TODAY A DUO, BUT ONCE A TRIO? THE DOUBLE WHITE DWARF HS 2220+2146 MAY BE A POST-BLUE STRAGGLER BINARY.
- Author
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Jeff J. Andrews, Marcel Agüeros, Warren R. Brown, Natalie M. Gosnell, A. Gianninas, Mukremin Kilic, and Detlev Koester
- Subjects
WHITE dwarf stars ,DWARF stars ,BLUE stragglers (Stars) ,EARLY stars ,STELLAR evolution - Abstract
For sufficiently wide orbital separations a, the two members of a stellar binary evolve independently. This implies that in a wide double white dwarf (DWD), the more massive WD should always be produced first, when its more massive progenitor ends its main sequence (MS) life, and should therefore be older and cooler than its companion. The bound, wide DWD HS 2220+2146 ( au) does not conform to this picture: the more massive WD is the younger and hotter of the pair. We show that this discrepancy is unlikely to be due to past mass-transfer phases or to the presence of an unresolved companion. Instead, we propose that HS 2220+2146 formed through a new wide DWD evolutionary channel involving the merger of the inner binary in a hierarchical triple system. The resulting blue straggler and its wide companion then evolved independently, forming the WD pair seen today. Although we cannot rule out other scenarios, the most likely formation channel has the inner binary merging while both stars are still on the MS. This provides us with the tantalizing possibility that Kozai–Lidov oscillations may have played a role in the inner binary’s merger. Gaia may uncover hundreds more wide DWDs, leading to the identification of other systems like HS 2220+2146. There are already indications that other WD systems may have been formed through different, but related, hierarchical triple evolutionary scenarios. Characterizing these populations may allow for thorough testing of the efficiency with which Kozai–Lidov oscillations induce stellar mergers. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
25. IMPLICATIONS FOR THE FORMATION OF BLUE STRAGGLER STARS FROM HST ULTRAVIOLET OBSERVATIONS OF NGC 188.
- Author
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Natalie M. Gosnell, Robert D. Mathieu, Aaron M. Geller, Alison Sills, Nathan Leigh, and Christian Knigge
- Subjects
- *
WHITE dwarf stars , *MASS transfer , *BLUE stragglers (Stars) , *ASTRONOMICAL photometry - Abstract
We present results of a Hubble Space Telescope (HST) far-ultraviolet (FUV) survey searching for white dwarf (WD) companions to blue straggler stars (BSSs) in open cluster NGC 188. The majority of NGC 188 BSSs (15 of 21) are single-lined binaries with properties suggestive of mass-transfer formation via Roche lobe overflow, specifically through an asymptotic giant branch star transferring mass to a main sequence secondary, yielding a BSS binary with a WD companion. In NGC 188, a BSS formed by this mechanism within the past 400 Myr will have a WD companion that is hot and luminous enough to be directly detected as a FUV photometric excess with HST. Comparing expected BSS FUV emission to observed photometry reveals four BSSs with WD companions above 12,000 K (younger than 250 Myr) and three WD companions with temperatures between 11,000 and 12,000 K. These BSS+WD binaries all formed through recent mass transfer. The location of the young BSSs in an optical color–magnitude diagram (CMD) indicates that distance from the zero-age main sequence does not necessarily correlate with BSS age. There is no clear CMD separation between mass transfer-formed BSSs and those likely formed through other mechanisms, such as collisions. The seven detected WD companions place a lower limit on the mass-transfer formation frequency of 33%. We consider other possible formation mechanisms by comparing properties of the BSS population to theoretical predictions. We conclude that 14 BSS binaries likely formed from mass transfer, resulting in an inferred mass-transfer formation frequency of approximately 67%. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
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