Edward F. Guinan

Edward F. Guinan
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Edward verified their affiliation via an institutional email.
Verified
Edward verified their affiliation via an institutional email.
  • PhD
  • Professor (Full) at Villanova University

About

844
Publications
42,923
Reads
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10,418
Citations
Current institution
Villanova University
Current position
  • Professor (Full)
Additional affiliations
January 2013 - June 2015
James Cook University
Position
  • Professor (Associate)
August 1975 - August 1978
Shiraz University
Position
  • Visitng Professor
Description
  • Taught courses in Physics and Astrophysics. Helped to establish Biruni Observatory.
September 1984 - September 1992
Center for Astrophysics Harvard & Smithsonian
Position
  • Visiting Summer Fellow

Publications

Publications (844)
Article
Full-text available
Antares A is a bright ∼0.6–1.3 mag irregular/semi-regular variable M1.5 Iab star. Antares with Betelgeuse (M2.5 Iab) are the two nearest red supergiant, core-collapse Type-II supernova progenitors. Unlike Betelgeuse, Antares A has a resolved companion (B4V: Antares B) and is near its birthplace in the Upper Scorpius OB Association. We analyzed ∼70...
Article
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Recent studies indicate that Gliese 581d, a proposed habitable zone (HZ) super-Earth planet, does not exist, as the respective data denote that the planet is an artifact of stellar activity. Here we report evidence to the contrary considering that those studies were based on inaccurate spectroscopic measurements of the stellar rotation period regar...
Article
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Age is a fundamental stellar property, yet for many stars, it is difficult to reliably determine. For M dwarfs, it has been notoriously so. Due to their lower masses, core hydrogen fusion proceeds at a much slower rate in M dwarfs than it does in more massive stars like the Sun. As a consequence, more customary age determination methods (e.g., isoc...
Preprint
Full-text available
Age is a fundamental stellar property, yet for many stars it is difficult to reliably determine. For M dwarfs it has been notoriously so. Due to their lower masses, core hydrogen fusion proceeds at a much slower rate in M dwarfs than it does in more massive stars like the Sun. As a consequence, more customary age determination methods (e.g. isochro...
Article
Full-text available
GJ 667Cc is a nearby (23.6 lt-yr) super-Earth that orbits within the habitable zone (HZ) of its ∼M2V host star and has Earth-like properties: ( M - sin ( i ) ∼ 4.1 M ⊕ ; R ∼ 1.7 R ⊕ ; T eq ( A = 0.3) ∼ 277 K). The age of the star/planet is poorly constrained at 2 ≳ Gyr. Age is crucial in evaluating the potential for complex life. We determine an ag...
Article
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X-ray observations have been made of a sample of 20 classical Cepheids, including two new observations (Polaris and l Car) reported here. The occurrence of X-ray flux around the pulsation cycle is discussed. Three Cepheids are detected ( δ Cep, β Dor, and Polaris). X-rays have also been detected from the low-mass F, G, and K companions of four Ceph...
Article
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W Persei is a massive, luminous and large red supergiant located relatively nearby. W Persei is a probable SN-II progenitor. We analyzed ∼120 yr of photometry from the AAVSO database. The analysis was conducted in the period analysis software Peranso where the CLEANest power spectrum and WWZ-wavelet programs were utilized. Two dominant periods of P...
Preprint
Full-text available
X-ray observations have been made of a sample of 20 classical Cepheids, including two new observations (Polaris and {\it l} Car) reported here. The occurrence of X-ray flux around the pulsation cycle is discussed. Three Cepheids are detected ($\delta$ Cep, $\beta$ Dor, and Polaris). X-rays have also been detected from the low--mass F, G, and K comp...
Article
Full-text available
Few stars offer as much toward understanding fundamental aspects of stellar astrophysics and binary star evolution than the eclipsing binary V471 Tauri (DAZ+K2V; P = 12.52 hr). V471 Tauri (Tau) is the product of common-envelope binary evolution and a pre-cataclysmic variable. X-ray and UV (291 nm) observations were secured with XMM-Newton over ∼ 62...
Article
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VY Canis Majoris (VY CMa) is one of the largest, most luminous red supergiant (RSG) stars in the Galaxy. This huge oxygen-rich RSG may be on the verge of becoming a bright core-collapse Type-II supernova. Over the 20th century, VY CMa has been undergoing episodic large quasi-periodic light variations. It has experienced two “great dimming” episodes...
Article
We report NASA-DLR SOFIA upGREAT circumstellar [O i ] 63.2 μ m and [C ii ] 157.7 μ m emission profiles and FIFI-LS [O i ] 63.2 μ m, [O i ] 145.5 μ m, and [C ii ] 157.7 μ m fluxes obtained shortly after Betelgeuse’s 2019/2020 Great Dimming event. Haas et al. noted a potential correlation between the [O i ] 63.2 μ m flux and V magnitude based on thre...
Article
Full-text available
We report on Transiting Exoplanet Survey Satellite (TESS) high-precision photometry of the iconic non-eclipsing 5.60 days (O9.7Iab+black hole) binary Cygnus X-1. Previous ground-based photometry reveals low-amplitude (∼0.04 mag) ellipsoidal light-variations that arise from the tidal (and rotational) distortion of the O9.7Iab companion. Additional s...
Article
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X-ray bursts have recently been discovered in the Cepheids δ Cep and β Dor modulated by the pulsation cycle. We have obtained an observation of the Cepheid η Aql with the XMM-Newton satellite at the phase of maximum radius; the phase at which there is a burst of X-rays in δ Cep. No X-rays were seen from the Cepheid η Aql at this phase, and the impl...
Article
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μ Cephei is a 4th mag semi-regular variable M2Ia star. It is among the largest, most luminous red supergiants in our galactic neighborhood and a probable SN-II core-collapse progenitor. Analyses of ∼175 yr of photometry were conducted. The observations are mostly from the AAVSO database. Period analyses were conducted using the Period Analysis Soft...
Preprint
Full-text available
X-ray bursts have recently been discovered in the Cepheids $\delta$ Cep and $\beta$ Dor modulated by the pulsation cycle. We have obtained an observation of the Cepheid $\eta$ Aql with the XMM-Newton satellite at the phase of maximum radius, the phase at which there is a burst of X-rays in $\delta$ Cep. No X-rays were seen from the Cepheid $\eta$ A...
Article
Full-text available
Cepheids in multiple systems provide information on the outcome of the formation of massive stars. They can also lead to exotic end-stage objects. This study concludes our survey of 70 galactic Cepheids using the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) with images at two wavelengths to identify companions closer than 5″. In the enti...
Article
Full-text available
The processes that shape the extended atmospheres of red supergiants, heat their chromospheres, create molecular reservoirs, drive mass loss, and create dust remain poorly understood. Betelgeuse’s V -band “Great Dimming” event of 2019 September/2020 February and its subsequent rapid brightening provides a rare opportunity to study these phenomena....
Preprint
Full-text available
The processes that shape the extended atmospheres of red supergiants (RSGs), heat their chromospheres, create molecular reservoirs, drive mass loss, and create dust remain poorly understood. Betelgeuse's V-band "Great Dimming" event of 2019 September /2020 February and its subsequent rapid brightening provides a rare opportunity to study these phen...
Preprint
Cepheids in multiple systems provide information on the outcome of the formation of massive stars. They can also lead to exotic end-stage objects. This study concludes our survey of 70 galactic Cepheids using the {\it Hubble Space Telescope\} (\HST) Wide Field Camera~3 (WFC3) with images at two wavelengths to identify companions closer than $5\arcs...
Article
Full-text available
The fact that Earth is teeming with life makes it appear odd to ask whether there could be other planets in our galaxy that may be even more suitable for life. Neglecting this possible class of "superhabitable" planets, however, could be considered anthropocentric and geocentric biases. Most important from the perspective of an observer searching f...
Article
The bright supergiant Betelgeuse (Alpha Orionis, HD 39801) experienced a visual dimming during 2019 December and the first quarter of 2020, reaching an historic minimum 2020 February 7–13. During 2019 September–November, prior to the optical dimming event, the photosphere was expanding. At the same time, spatially resolved ultraviolet spectra using...
Preprint
Full-text available
The bright supergiant, Betelgeuse (Alpha Orionis, HD 39801) experienced a visual dimming during 2019 December and the first quarter of 2020 reaching an historic minimum 2020 February 7$-$13. During 2019 September-November, prior to the optical dimming event, the photosphere was expanding. At the same time, spatially resolved ultraviolet spectra usi...
Article
Classical Cepheids are powerful probes of both stellar evolution and near-field cosmology thanks to their great luminosities, pulsations, and their adherence to the Leavitt (period–luminosity) Law. However, there still exist a number of questions regarding their evolution, such as the roles of rotation, convective core overshooting, and winds. ln p...
Preprint
We first present spatially resolved ALMA and VLA continuum observations of the early-M red supergiant Antares to search for the presence of a chromosphere at radio wavelengths. We resolve the free-free emission of the Antares atmosphere at 11 unique wavelengths between 0.7 mm (ALMA band 8) and 10 cm (VLA S band). The projected angular diameter is f...
Article
We first present spatially resolved ALMA and VLA continuum observations of the early-M red supergiant Antares to search for the presence of a chromosphere at radio wavelengths. We resolve the free-free emission of the Antares atmosphere at 11 unique wavelengths between 0.7 mm (ALMA band 8) and 10 cm (VLA S band). The projected angular diameter is f...
Article
In 2019 October Betelgeuse began a decline in V -band brightness that went beyond the minimum expected from its quasi-periodic ∼420 day cycle, becoming the faintest in recorded photometric history. Observations obtained in 2019 December with Very Large Telescope/SPHERE have shown that the southern half of the star has become markedly fainter than i...
Preprint
In 2019 October Betelgeuse began a decline in V-band brightness that went beyond the minimum expected from its quasi-periodic ~420 day cycle, becoming the faintest in recorded photometric history. Observations obtained in 2019 December with VLT/SPHERE (Montarges 2020) have shown that the southern half of the star has become markedly fainter than in...
Article
V473 Lyr is a classical Cepheid that is unique in having substantial amplitude variations with a period of approximately 3.3 yr, thought to be similar to the Blazhko variations in RR Lyrae stars. We obtained an XMM-Newton observation of this star to follow up a previous detection in X-rays. Rather than the X-ray burst and rapid decline near maximum...
Preprint
Full-text available
V473 Lyr is a classical Cepheid which is unique in having substantial amplitude variations with a period of approximately 3.3 years, thought to be similar to the Blazhko variations in RR Lyrae stars. We obtained an {\it XMM-Newton} observation of this star to followup a previous detection in X-rays. Rather than the X-ray burst and rapid decline nea...
Preprint
PolStar is an Explorer-class far ultraviolet (FUV) spectropolarimetry mission designed to target massive stars and their environments. PolStar will take advantage of resonance lines only available in the FUV to measure for the first time the magnetic and wind environment around massive stars to constrain models of rotation and mass loss.
Preprint
Full-text available
We summarize some of the compelling new scientific opportunities for understanding stars and stellar systems that can be enabled by sub-milliarcsec (sub-mas) angular resolution, UV-Optical spectral imaging observations, which can reveal the details of the many dynamic processes (e.g., evolving magnetic fields, accretion, convection, shocks, pulsati...
Article
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The search for Earth-like planets around late-type stars using ultra-stable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, since these phenomena induce radial velocity (RV) signals that can be misinterpreted as planetary signals. Among the nearby stars, we have selected Barnard’s S...
Preprint
Full-text available
The search for Earth-like planets around late-type stars using ultra-stable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, since these phenomena induce radial velocity (RV) signals that can be misinterpreted as planetary signals. Among the nearby stars, we have selected Barnard's S...
Article
Full-text available
Barnard’s star is a red dwarf, and has the largest proper motion (apparent motion across the sky) of all known stars. At a distance of 1.8 parsecs¹, it is the closest single star to the Sun; only the three stars in the α Centauri system are closer. Barnard’s star is also among the least magnetically active red dwarfs known2,3 and has an estimated a...
Preprint
At a distance of 1.8 parsecs, Barnard's star (Gl 699) is a red dwarf with the largest apparent motion of any known stellar object. It is the closest single star to the Sun, second only to the alpha Centauri triple stellar system. Barnard's star is also among the least magnetically active red dwarfs known and has an estimated age older than our Sola...
Preprint
Full-text available
Classical Cepheids are powerful probes of both stellar evolution and near-field cosmology thanks to their high luminosities, pulsations, and that they follow the Leavitt (Period-Luminosity) Law. However, there still exist a number of questions regarding their evolution, such as the role of rotation, convective core overshooting and winds. ln partic...
Preprint
We analyze space- and ground-based data for the old ($7.0\pm0.3$~Gyr) solar analogs 16 Cyg A and B. The stars were observed with the Cosmic Origins UV Spectrographs on the Hubble Space Telescope (HST) on 23 October 2015 and 3 February 2016 respectively, and with the Chandra X-ray Observatory on 7 February 2016. Time-series data in \ion{Ca}{2} data...
Article
Full-text available
We analyze space- and ground-based data for the old ($7.0\pm0.3$~Gyr) solar analogs 16 Cyg A and B. The stars were observed with the Cosmic Origins UV Spectrographs on the Hubble Space Telescope (HST) on 23 October 2015 and 3 February 2016 respectively, and with the Chandra X-ray Observatory on 7 February 2016. Time-series data in \ion{Ca}{2} data...
Article
We present the first results of a continuous monitoring of Algol with IUE along 1.5 orbital period (4 1/3 days). A total of 32 high resolution spectra were obtained. Algol represents the final slow stage of mass transfer. The spectra show the presence of high ionization lines (NV, SiIV, CIV) due to the heating of the gas that impacts the accreting...
Article
Full-text available
A review of IAU Symposium 151 on Interacting Binary Stars is given along with discussions of the present and future prospects of research in close binary stars.
Preprint
We provide an update for the astrometric solution for the Type II supernova progenitor Betelgeuse using the revised Hipparcos Intermediate Astrometric Data (HIAD) of van Leeuwen, combined with existing VLA and new e-MERLIN and ALMA positions. The 2007 Hipparcos refined abscissa measurements required the addition of so-called Cosmic Noise of 2.4 mas...
Article
We provide an update for the astrometric solution for the Type II supernova progenitor Betelgeuse using the revised Hipparcos Intermediate Astrometric Data (HIAD) of van Leeuwen, combined with existing VLA and new e-MERLIN and ALMA positions. The 2007 Hipparcos refined abscissa measurements required the addition of so-called Cosmic Noise of 2.4 mas...
Article
From our Secret Lives of Cepheids program, the prototype Classical Cepheid, $\delta$ Cep, is found to be an X-ray source with periodic pulsation-modulated X-ray variations. This finding complements our earlier reported phase-dependent FUV--UV emissions of the star that increase $\sim$10--20 times with highest fluxes at $\sim0.90-0.95\phi$, just pri...
Preprint
From our Secret Lives of Cepheids program, the prototype Classical Cepheid, $\delta$ Cep, is found to be an X-ray source with periodic pulsation-modulated X-ray variations. This finding complements our earlier reported phase-dependent FUV--UV emissions of the star that increase $\sim$10--20 times with highest fluxes at $\sim0.90-0.95\phi$, just pri...
Article
Full-text available
We present a NASA-DLR SOFIA-Echelon Cross Echelle Spectrograph (EXES) and NASA Infrared Telescope Facility-Texas Echelon Cross Echelle Spectrograph (TEXES) mid-IR R ≃ 50,000 spectral study of forbidden Fe II transitions in the early-type M supergiants, Betelgeuse (α Ori: M2 Iab) and Antares (α Sco: M1 Iab + B3 V). With EXES, we spectrally resolve t...
Article
Full-text available
The X-ray observations of three classical Cepheids produce a surprising result. At approximately the phase of maximum radius there is a sharp increase in X-ray flux above the normal “quiescent” level. The relation of this new upper atmosphere diagnostic to other phenonena above the photosphere is discussed.
Article
The number of confirmed exoplanets now exceeds 3000, with an additional nearly 5000 exoplanet candidates awaiting confirmation in the NASA Exoplanet Archive (2016). Nearly weekly we hear about the detection of a new exoplanet similar in mass to Earth and located in the so-called habitable zone around its host star. The excitement is understandable...
Article
Full-text available
Among the solar proxies, κ ¹ Cet, stands out as potentially having a mass very close to solar and a young age. We report magnetic field measurements and planetary habitability consequences around this star, a proxy of the young Sun when life arose on Earth. Magnetic strength was determined from spectropolarimetric observations and we reconstruct th...
Article
Full-text available
Proxima b is a planet with a minimum mass of 1.3 MEarth orbiting within the habitable zone (HZ) of Proxima Centauri, a very low-mass, active star and the Sun's closest neighbor. Here we investigate a number of factors related to the potential habitability of Proxima b and its ability to maintain liquid water on its surface. We set the stage by esti...
Preprint
Proxima b is a planet with a minimum mass of 1.3 MEarth orbiting within the habitable zone (HZ) of Proxima Centauri, a very low-mass, active star and the Sun's closest neighbor. Here we investigate a number of factors related to the potential habitability of Proxima b and its ability to maintain liquid water on its surface. We set the stage by esti...
Article
One of the most fundamental topics of exobiology concerns the identification of stars with environments consistent with life. Although it is believed that most types of main-sequence stars might be able to support life, particularly extremophiles, special requirements appear to be necessary for the development and sustainability of advanced life fo...
Preprint
One of the most fundamental topics of exobiology concerns the identification of stars with environments consistent with life. Although it is believed that most types of main-sequence stars might be able to support life, particularly extremophiles, special requirements appear to be necessary for the development and sustainability of advanced life fo...
Article
As part of Villanova's Living with a Red Dwarf program, we have obtained UV, X-ray and optical data of the Population II red dwarf -- Kapteyn's Star. Kapteyn's Star is noteworthy for its large proper motions and high RV of ~+245 km s^-1. As the nearest Pop II red dwarf, it serves as an old age anchor for calibrating Activity/Irradiance-Rotation-Age...
Article
The classical Cepheid $l$ Carinae is an essential calibrator of the Cepheid Leavitt Law as a rare long-period Galactic Cepheid. Understanding the properties of this star will also constrain the physics and evolution of massive ($M \ge 8$ $M_\odot$) Cepheids. The challenge, however, is precisely measuring the star's pulsation period and its rate of...
Preprint
The classical Cepheid $l$ Carinae is an essential calibrator of the Cepheid Leavitt Law as a rare long-period Galactic Cepheid. Understanding the properties of this star will also constrain the physics and evolution of massive ($M \ge 8$ $M_\odot$) Cepheids. The challenge, however, is precisely measuring the star's pulsation period and its rate of...
Article
We have made XMM-Newton observations of 14 Galactic Cepheids that have candidate resolved (≥5'') companion stars based on our earlier HST Wide Field Camera 3 (WFC3) imaging survey. Main-sequence stars that are young enough to be physical companions of Cepheids are expected to be strong X-ray producers in contrast to field stars. XMM-Newton exposure...
Article
The VV Cep close binary system (O8V + M2 lab; P = 20 3 yrs.) is described from published spectral, radial velocity, photometric, and astrometric results. A long-term photometric monitoring program shows intrinsic variability in a red bandpass. Variability exists on several time scales and the longest of these is attributed to tidal distortion of th...
Article
Full-text available
We report magnetic field measurements for κ1 Cet, a proxy of the young Sun when life arose on Earth. We carry out an analysis of the magnetic properties determined from spectropolarimetric observations and reconstruct the large-scale surface magnetic field to derive the magnetic environment, stellar winds, and particle flux permeating the interplan...
Preprint
We report magnetic field measurements for Kappa1~Cet, a proxy of the young Sun when life arose on Earth. We carry out an analysis of the magnetic properties determined from spectropolarimetric observations and reconstruct its large-scale surface magnetic field to derive the magnetic environment, stellar winds and particle flux permeating the interp...
Preprint
Full-text available
We have made {\it XMM-Newton\/} observations of 14 Galactic Cepheids that have candidate resolved ($\geq$5$\arcsec$) companion stars based on our earlier {\it HST\/} WFC3 imaging survey. Main-sequence stars that are young enough to be physical companions of Cepheids are expected to be strong X-ray producers in contrast to field stars. {\it XMM-Newt...
Preprint
As part of Villanova's Living with a Red Dwarf program, we have obtained UV, X-ray and optical data of the Population II red dwarf -- Kapteyn's Star. Kapteyn's Star is noteworthy for its large proper motions and high RV of ~+245 km s^-1. As the nearest Pop II red dwarf, it serves as an old age anchor for calibrating Activity/Irradiance-Rotation-Age...
Article
Full-text available
Seventeen years of V-band and intermediateWing near-IRTiO (λ719-nm to λ1024-nm) time-series photometry of the M1-4 Iab supergiant TV Geminorum are presented. The observations were conducted from 1997 to 2014 with the primary goals of determining both long-term (years) and short-term (months) periodicities and estimating temporal changes in temperat...
Article
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We discuss the IAU Commission 46 and Office for Astronomy Development (OAD) programs that support advancing Astronomy education and research primarily in universities in developing countries. The bulk of these operational activities will be coordinated through the OAD's newly installed Task Force 1. We outline current (and future) IAU/OAD Task Forc...
Article
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C46 was a Commission of the Executive Committee of the IAU under Division XII (Union-Wide Activities), then after 2012 under Division C (Education, Outreach, and Heritage). It was the only commission dealing exclusively with astronomy education; a previous Commission 38 (Exchange of Astronomers), which allocated travel grants to astronomers who nee...
Article
In 2012, the International Astronomical Union (IAU), through its Office of Astronomy for Development (OAD), established the three Task Forces which drive global activities using astronomy as a tool to stimulate development. These Task Forces are: (i) Astronomy for Universities and Research; (ii) Astronomy for Children and Schools; and (iii) Astrono...
Article
The main purpose of this panel discussion was to encourage conversation around potential collaborations between the IAU Office of Astronomy for Development (OAD) and IAU Divisions. The discussion was facilitated by the OAD and the conversation revolved mainly around two questions: (i) What should the OAD be doing to enhance the work of the Division...
Article
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We use the Very Large Array (VLA) in the A configuration with the Pie Town (PT) Very Long Baseline Array (VLBA) antenna to spatially resolve the extended atmosphere of Betelgeuse over multiple epochs at 0.7, 1.3, 2.0, 3.5, and 6.1 cm. The extended atmosphere deviates from circular symmetry at all wavelengths while at some epochs we find possible ev...
Article
Full-text available
Over the past decade, the Secret Lives of Cepheids (SLiC) program has been carried out at Villanova University to study aspects and behaviors of classical Cepheids that are still not well-understood. In this, the first of several planned papers on program Cepheids, we report the current results for delta Cep, the Cepheid prototype. Ongoing photomet...
Article
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Measurements of secular period change probe real-time stellar evolution of classical Cepheids making these measurements powerful constraints for stellar evolution models, especially when coupled with interferometric measurements. In this work, we present stellar evolution models and measured rates of period change for two Galactic Cepheids: Polaris...
Article
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The galactic Cepheid S Muscae has recently been added to the important list of Cepheids linked to open clusters, in this case the sparse young cluster ASCC 69. Low-mass members of a young cluster are expected to have rapid rotation and X-ray activity, making X-ray emission an excellent way to discriminate them from old field stars. We have made an...
Article
Full-text available
Thanks to its long and rich observational history and rapid apsidal motion, the massive eclipsing binary Y Cyg represents one of the cornestones to critical tests of stellar evolution theory for massive stars. Yet, the determination of the basic physical properties is less accurate than it could be given the existing number of spectral and photomet...
Article
M-dwarf stars are the most common stars in the universe (80%) but also form the one of the least explored spectral classes. We analyzed a photometric sample of the 500 brightest M-dwarf star long-cadence lightcurves (T<4000K, logg>4) from the Kepler MAST catalogue for rotation rates of starspots and presence of flares. We determined (differential)...
Article
Red dwarfs (dM) stars make up over 80% of the local stellar population and a significant fraction of them are old (age > 4 Gyr). Because of the high frequency of red dwarfs and their longevity, there is a greater possibility of more advanced life in red dwarf planet systems. MEarths, UVES, SDSS-III, and the upcoming TESS mission are some surveys th...
Article
Polaris is arguably the best-known star in the Northern Hemisphere, since it lies within a degree of the North Celestial Pole. For much of human history, Polaris was highly regarded for its unchanging nature. However, we now know that Polaris is a Cepheid variable, undergoing ultra-low-amplitude pulsations. Thirty years ago, a paper in the Astrophy...
Article
We have compiled a catalogue of all exoplanets and their host stars within ten parsecs (32.6 ly) from the Sun. In addition to the physical properties of the exoplanets: estimated mass, orbital period, etc; we have compiled the properties of the host stars. These include: spectral class, effective temperature, luminosity, metallicity, period of rota...
Article
The 1.3 m (50 inch) telescope on Kitt Peak has been refurbished and provided with an autonomous scheduler. It is operated by The Robotically Controlled Telescope (RCT) consortium whose members are: South Carolina State, Villanova and Western Kentucky Universities. The facility possesses 5 board (UBVRI) and 11 narrow-band filters. Attached to the RC...
Article
We present an analysis of 58 low-mass stars surveyed by the Kepler Space Telescope. Our initial study was a search for eclipses in a sample of candidate M dwarf - white dwarf binary stars. The stars were observed in the Kepler wide-band visual filter nearly continuously over 300 days, at a cadence of 29.5 minutes. The resulting light curves were us...
Article
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The RCT 1.3-meter telescope, formerly known as the Kitt Peak National Observatory (KPNO) 50-inch telescope, has been refurbished as a fully robotic telescope, using an autonomous scheduler to take full advantage of the observing site without the requirement of a human presence. Here we detail the current configuration of the RCT, and present as a d...
Article
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α1 Her is the second closest Asymptotic Giant Branch (AGB) star to the Sun, and the variable luminous M5 Ib-II member of a triple stellar system containing G8 III and A9 IV-V components. However, the mass of this important star was previously uncertain with published values ranging from ∼2 - 15M⊙. As shown by this study, its fortuitous membership i...
Article
Full-text available
Among the solar proxies studied in the Sun in Time k Cet (HD 20630) stands out as potentially having a mass very close to solar and a young age. On this study, we monitored the magnetic field and the chromospheric activity from the Ca II H & K lines of k Cet. We used the Least-Square-Deconvolution (LSD, Donati et al. 1997) by simultaneously extract...

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