Laura Penny | College of Charleston (original) (raw)
Papers by Laura Penny
We are proposing here to look for new double-lined spectroscopic binaries among the most luminous... more We are proposing here to look for new double-lined spectroscopic binaries among the most luminous and massive stars in three OB associations/clusters: Cyg OB2, IC 1805, and NGC 6611. These clusters contain stars whose evolutionary tracks would suggest masses as high as 120 M_&sun;, and discovering double-lined eclipsing systems among this sample would allow us to resolve whether stellar evolutionary models or stellar atmosphere models (or neither) yield the correct answers for the masses of massive stars. (The stellar evolutionary models are the basis for all estimates of the IMF for massive stars, and yet they predict masses that are 1.5-2.0× more than that inferred from model atmosphere analysis.) Given the relatively high frequency of binaries with short periods found for massive stars (40%) we expect to find about 20 systems suitable for follow-up studies.
We present double-lined spectroscopic orbital elements for the central binary in the massive mult... more We present double-lined spectroscopic orbital elements for the central binary in the massive multiple star, HD 206267 based on fits of cross-correlation functions of the 36 IUE high dispersion UV spectra available. These elements give masses for the primary and secondary components of m1 sin 3 i = 28.0 M&sun; ± 1.8 and m2 sin 3 i = 15.3 M&sun; ± 1.5. We also present tomographic reconstructions of all three spectroscopic components that confirm the O6.5 V((f)) classification of the composite spectrum applies to the primary, indicate a B0 V type for the secondary, and an O8 V type for the tertiary. The relative line strengths between the reconstructed spectra suggest magnitude differences of Delta m = -2.5 log (Fs/F_p) = 1.4 ± 0.2 in the UV and Delta m = 1.2 ± 0.3 in the optical for the secondary and Delta m = -2.5 log (Ft/F_p) = 1.2 ± 0.2 in the UV and Delta m = 1.0 ± 0.3 in the optical for the tertiary. The widths of the UV cross-correlation functions are used to estimate the projec...
Stellar interior models are critical tools used in all branches of astronomy from chemical evolut... more Stellar interior models are critical tools used in all branches of astronomy from chemical evolution and population synthesis studies to the determination of evolutionary masses. Until recently the effects of rotation were not included in these codes. The new models show that rotation induces interior mixing that produces some drastic external changes for massive stars while they are still core-hydrogen
Fifteen very young OB stars have recently been discovered in the Galactic HII region M17. This cl... more Fifteen very young OB stars have recently been discovered in the Galactic HII region M17. This cluster represents the excitation source in the nearest giant HII region in our Galaxy. Six of the stars show evidence for stellar discs, but the others appear to have cleared away their birth material. Could the latent presence of discs be coupled to either
The relationship between mass and luminosity is poorly determined for high mass stars, with stell... more The relationship between mass and luminosity is poorly determined for high mass stars, with stellar atmosphere analysis often yielding lower estimates of the masses than stellar evolutionary models predict. For the hottest massive stars in the Magellanic Clouds such differences can be as much as a factor of two. This "mass discrepancy" problem has been known for 15 years. During
The Astrophysical Journal, 2012
The Astrophysical Journal, 2002
The Astrophysical Journal, 1999
Page 1. THE ASTROPHYSICAL JOURNAL, 527 : 353È359, 1999 December 10 1999. The American Astronomica... more Page 1. THE ASTROPHYSICAL JOURNAL, 527 : 353È359, 1999 December 10 1999. The American Astronomical Society. All rights reserved. Printed in USA ( THE STRUVE-SAHADE EFFECT: A TALE OF THREE STARS WILLIAM ...
The Astrophysical Journal, 1996
ABSTRACT We present equivalent-width measurements of ultraviolet photospheric lines that are usef... more ABSTRACT We present equivalent-width measurements of ultraviolet photospheric lines that are useful as spectral type criteria; these include 23 lines of He II, C III, N III, N IV, O IV, Si III, Si IV, S V, Fe IV, and Fe V in lUE spectra of 67 O3 to BO stars of all luminosity classes. Seven lines and two line ratios are particularly sensitive to spectral type, and we show how the ultraviolet spectral typing diagnostics lead to types that are consistent with optical types. There are few luminosity-sensitive photospheric lines in the ultraviolet but we find that the N IV λ1718 line does have a significant luminosity variation among most 0 subtypes. This criterion leads to ultraviolet classes that are approximately in agreement with optical luminosity classes. This scheme was developed in order to estimate the spectral types and luminosity classes of tomographically separated component spectra of 0-type binary systems.
The Astrophysical Journal, 1997
The Astrophysical Journal, 2008
The Astrophysical Journal, 2004
![Research paper thumbnail of Dynamical Masses for the Large Magellanic Cloud Massive Binary System [L72] LH 54‐425](https://attachments.academia-assets.com/88325248/thumbnails/1.jpg)
](The Astrophysical Journal, 2008
The Astrophysical Journal, 1998
The Astrophysical Journal, 2009
The Astrophysical Journal, 1992
ABSTRACT We present the results of a Doppler tomographic reconstruction of the UV spectra of the ... more ABSTRACT We present the results of a Doppler tomographic reconstruction of the UV spectra of the double-lined, O binary DH Cephei based on observations made with the International Ultraviolet Explorer. We describe cross-correlation methods we use to obtain precise radial velocities, and we present a radial velocity curve based on combined optical and UV measurements. We also show how we use fits of the cross-correlation functions to estimate the UV flux ratio and projected rotational velocities. The individual component spectra are classified as O6 V + O7 V using UV criteria defined by Penny, Gies, & Bagnuolo. We place the individual components in the theoretical Hertzsprung-Russell diagram using the distance modulus and reddening estimated for its home cluster, NGC 7380, and we find that the stars are larger than estimates from prior studies of the "ellipsoidal" light variations. We reconsider the ellipsoidal light curve and show that there is a range in acceptable stellar radii (as a function of orbital inclination). We discuss the constraints on inclination and system masses based on cluster distance modulus, presumed synchronous rotation, and on consistency with masses derived from evolutionary tracks (which involves the issue of the temperature calibration of O stars). We find that primary and secondary masses of 39-50 M☉ and 35-45 M☉, respectively, satisfy all the constraints from spectroscopy, photometry, distance modulus, and single-star evolutionary tracks.
The Astrophysical Journal, 2002
The Astrophysical Journal, 1996
... Printed in USA PROJECTED ROTATIONAL VELOCITIES OF 0-TYPE STARS LAURA R. PENNY' Center fo... more ... Printed in USA PROJECTED ROTATIONAL VELOCITIES OF 0-TYPE STARS LAURA R. PENNY' Center for High Angular Resolution Astronomy and Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303; penny~chara.gsu.edu Received 1995 ...
We are proposing here to look for new double-lined spectroscopic binaries among the most luminous... more We are proposing here to look for new double-lined spectroscopic binaries among the most luminous and massive stars in three OB associations/clusters: Cyg OB2, IC 1805, and NGC 6611. These clusters contain stars whose evolutionary tracks would suggest masses as high as 120 M_&sun;, and discovering double-lined eclipsing systems among this sample would allow us to resolve whether stellar evolutionary models or stellar atmosphere models (or neither) yield the correct answers for the masses of massive stars. (The stellar evolutionary models are the basis for all estimates of the IMF for massive stars, and yet they predict masses that are 1.5-2.0× more than that inferred from model atmosphere analysis.) Given the relatively high frequency of binaries with short periods found for massive stars (40%) we expect to find about 20 systems suitable for follow-up studies.
We present double-lined spectroscopic orbital elements for the central binary in the massive mult... more We present double-lined spectroscopic orbital elements for the central binary in the massive multiple star, HD 206267 based on fits of cross-correlation functions of the 36 IUE high dispersion UV spectra available. These elements give masses for the primary and secondary components of m1 sin 3 i = 28.0 M&sun; ± 1.8 and m2 sin 3 i = 15.3 M&sun; ± 1.5. We also present tomographic reconstructions of all three spectroscopic components that confirm the O6.5 V((f)) classification of the composite spectrum applies to the primary, indicate a B0 V type for the secondary, and an O8 V type for the tertiary. The relative line strengths between the reconstructed spectra suggest magnitude differences of Delta m = -2.5 log (Fs/F_p) = 1.4 ± 0.2 in the UV and Delta m = 1.2 ± 0.3 in the optical for the secondary and Delta m = -2.5 log (Ft/F_p) = 1.2 ± 0.2 in the UV and Delta m = 1.0 ± 0.3 in the optical for the tertiary. The widths of the UV cross-correlation functions are used to estimate the projec...
Stellar interior models are critical tools used in all branches of astronomy from chemical evolut... more Stellar interior models are critical tools used in all branches of astronomy from chemical evolution and population synthesis studies to the determination of evolutionary masses. Until recently the effects of rotation were not included in these codes. The new models show that rotation induces interior mixing that produces some drastic external changes for massive stars while they are still core-hydrogen
Fifteen very young OB stars have recently been discovered in the Galactic HII region M17. This cl... more Fifteen very young OB stars have recently been discovered in the Galactic HII region M17. This cluster represents the excitation source in the nearest giant HII region in our Galaxy. Six of the stars show evidence for stellar discs, but the others appear to have cleared away their birth material. Could the latent presence of discs be coupled to either
The relationship between mass and luminosity is poorly determined for high mass stars, with stell... more The relationship between mass and luminosity is poorly determined for high mass stars, with stellar atmosphere analysis often yielding lower estimates of the masses than stellar evolutionary models predict. For the hottest massive stars in the Magellanic Clouds such differences can be as much as a factor of two. This "mass discrepancy" problem has been known for 15 years. During
The Astrophysical Journal, 2012
The Astrophysical Journal, 2002
The Astrophysical Journal, 1999
Page 1. THE ASTROPHYSICAL JOURNAL, 527 : 353È359, 1999 December 10 1999. The American Astronomica... more Page 1. THE ASTROPHYSICAL JOURNAL, 527 : 353È359, 1999 December 10 1999. The American Astronomical Society. All rights reserved. Printed in USA ( THE STRUVE-SAHADE EFFECT: A TALE OF THREE STARS WILLIAM ...
The Astrophysical Journal, 1996
ABSTRACT We present equivalent-width measurements of ultraviolet photospheric lines that are usef... more ABSTRACT We present equivalent-width measurements of ultraviolet photospheric lines that are useful as spectral type criteria; these include 23 lines of He II, C III, N III, N IV, O IV, Si III, Si IV, S V, Fe IV, and Fe V in lUE spectra of 67 O3 to BO stars of all luminosity classes. Seven lines and two line ratios are particularly sensitive to spectral type, and we show how the ultraviolet spectral typing diagnostics lead to types that are consistent with optical types. There are few luminosity-sensitive photospheric lines in the ultraviolet but we find that the N IV λ1718 line does have a significant luminosity variation among most 0 subtypes. This criterion leads to ultraviolet classes that are approximately in agreement with optical luminosity classes. This scheme was developed in order to estimate the spectral types and luminosity classes of tomographically separated component spectra of 0-type binary systems.
The Astrophysical Journal, 1997
The Astrophysical Journal, 2008
The Astrophysical Journal, 2004
The Astrophysical Journal, 2008
The Astrophysical Journal, 1998
The Astrophysical Journal, 2009
The Astrophysical Journal, 1992
ABSTRACT We present the results of a Doppler tomographic reconstruction of the UV spectra of the ... more ABSTRACT We present the results of a Doppler tomographic reconstruction of the UV spectra of the double-lined, O binary DH Cephei based on observations made with the International Ultraviolet Explorer. We describe cross-correlation methods we use to obtain precise radial velocities, and we present a radial velocity curve based on combined optical and UV measurements. We also show how we use fits of the cross-correlation functions to estimate the UV flux ratio and projected rotational velocities. The individual component spectra are classified as O6 V + O7 V using UV criteria defined by Penny, Gies, & Bagnuolo. We place the individual components in the theoretical Hertzsprung-Russell diagram using the distance modulus and reddening estimated for its home cluster, NGC 7380, and we find that the stars are larger than estimates from prior studies of the "ellipsoidal" light variations. We reconsider the ellipsoidal light curve and show that there is a range in acceptable stellar radii (as a function of orbital inclination). We discuss the constraints on inclination and system masses based on cluster distance modulus, presumed synchronous rotation, and on consistency with masses derived from evolutionary tracks (which involves the issue of the temperature calibration of O stars). We find that primary and secondary masses of 39-50 M☉ and 35-45 M☉, respectively, satisfy all the constraints from spectroscopy, photometry, distance modulus, and single-star evolutionary tracks.
The Astrophysical Journal, 2002
The Astrophysical Journal, 1996
... Printed in USA PROJECTED ROTATIONAL VELOCITIES OF 0-TYPE STARS LAURA R. PENNY' Center fo... more ... Printed in USA PROJECTED ROTATIONAL VELOCITIES OF 0-TYPE STARS LAURA R. PENNY' Center for High Angular Resolution Astronomy and Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303; penny~chara.gsu.edu Received 1995 ...