F. Bruhweiler - Academia.edu (original) (raw)
Papers by F. Bruhweiler
We have observed the extensive circumstellar disk (Kuiper Belt) of beta Pictoris using the WFPC2/... more We have observed the extensive circumstellar disk (Kuiper Belt) of beta Pictoris using the WFPC2/PC aboard the Hubble Space Telescope. We have used the pyramid of the WFPC2 to image separately the central star on a different CCD chip than that of the disk. This eliminated bleeding and other effects inherent in the CCDs, thereby leaving the PC chip containing
We present preliminary results for observations obtained by the Far-Ultraviolet Spectral Explorer... more We present preliminary results for observations obtained by the Far-Ultraviolet Spectral Explorer (FUSE) of three Wolf-Rayet pre-white dwarfs, the nuclei of NGC 6905, NGC 5189, and NGC 5315. These stars represent some of the hottest objects (Teff 100-170k K) in the H-R diagram. All three stars display ultra-high ionization emission lines, most notably emission from hydrogen-like O V III at
Proceedings of the International Astronomical Union, 2009
We derive a substantially improved ephemeris for HD 209-458b based on photometric transit observa... more We derive a substantially improved ephemeris for HD 209-458b based on photometric transit observations. I-band observations taken at SDSU's Mount Laguna Observatory during the 2001, 2002, and 2003 observing seasons were combined with transit observations by the Hubble Space Telescope STIS (Brown et al. 2001) and FGS (Schultz et al. 2003), and additional ground-based APT photometry. The Eclipsing Light Curve
Examination of high resolution (R 100,000) echelle spectra of the nearby, hot DA white dwarf, G19... more Examination of high resolution (R 100,000) echelle spectra of the nearby, hot DA white dwarf, G191-B2B, obtained by the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST) reveals two velocity components to the C IV resonance doublet at 1548 and 1550 Angstroms. One component is clearly photospheric and corresponds to the common velocity of other established photospheric
Coronagraphic imaging with STIS on the HST reveals an 450 AU circumstellar disk around the 4-10 M... more Coronagraphic imaging with STIS on the HST reveals an 450 AU circumstellar disk around the 4-10 Myr old Herbig Ae star HD 163296. A broad-band (0.2-1.1 micron) reflected light image shows the disk oriented with its semi-major axis at PA=140+/-5 degrees, and inclination of 60+/-5 degrees. The disk includes an annulus of depleted material at 325 AU, and a flat
We summarize a free-flying occulter proposal that was submitted to NASA in response to NRA-01-OSS... more We summarize a free-flying occulter proposal that was submitted to NASA in response to NRA-01-OSS-04. Free-flying occulters in association with space telescopes have been proposed for nearly four decades to detect and study extrasolar planets. External occulters reduce the magnitude differences between a planet and the host star; light scatter within the telescope is reduced resulting from fewer obstructions and
Applications of Photonic Technology 4, 2000
We present a novel coronagraphic imaging technique and design for space-based telescopes. The Umb... more We present a novel coronagraphic imaging technique and design for space-based telescopes. The Umbral Mission Blocking Radiating Astronomical Sources (UMBRAS) is a space mission design consisting of a free flying occulter, the Solar Powered Ion Driven Eclipsing Rover (SPIDER), and possibly one or two metrology platforms. The UMBRAS spacecraft operate in conjunction with a space-based telescope. The size of the occulting SPIDER is dictated by the size of the telescope with which it will work. The goal of UMBRAS is to provide "paleolithic" (i.e., non-focal plane) coronagraphic capability to enable direct imaging of extrasolar Jovian planets and other bright substellar companions such as brown dwarfs.
Astronomy and …, 1997
... 1994, Walter et al. ... Symp., Evolution in Astrophysics, ed. EJ Rolfe, ESA-SP 310, p. 315 Fr... more ... 1994, Walter et al. ... Symp., Evolution in Astrophysics, ed. EJ Rolfe, ESA-SP 310, p. 315 Freire Ferrero R., Catalano S., Marilli E., Wonnacott D. Bruhweiler F., Talavera A. 1993 in: Advances in Stellar and Solar Coronal Physics, GS Vaiana Memorial Symposium, eds JL Linsky, S ...
The very massive star, Eta Carinae, is enshrouded in an unusual complex environment of nebulositi... more The very massive star, Eta Carinae, is enshrouded in an unusual complex environment of nebulosities and structures. The circumstellar gas gives rise to distinct absorption and emission components at different velocities and distances from the central source(s). Through photoionization modeling, we find that the radiation field from the more massive B-star companion supports the low ionization structure throughout the 5.54 year period. The radiation field of an evolved O-star is required to produce the higher ionization emission seen across the broad maximum. Our studies utilize the HST/STIS data and model calculations of various regimes from doubly ionized species (T= 10,000K) to the low temperature (T = 760 K) conditions conductive to molecule formation (CH and OH). Overall analysis suggests the high depletion in C and O and the enrichment in He and N. The sharp molecular and ionic absorptions in this extensively CNO - processed material offers a unique environment for studying the...
The Astrophysical Journal, 2006
We present an observational picture of the HH 409 bipolar outflow including the detection of six ... more We present an observational picture of the HH 409 bipolar outflow including the detection of six previously unreported Herbig-Haro knots from the Herbig Ae star HD 163296. This study combines seven years of data from ground-based Fabry-Pérot and HST coronagraphic imagery, as well as HST long-slit spectral imagery. The redshifted counterjet includes a chain of six Herbig-Haro knots spanning >27 00 to the northeast (P:A: % 42 ) of the source and has been active for >80 yr. The brightest knot in the counterjet is HH 409 C, a low-excitation bow shock with a shock velocity V s $ 50 km s À1 and total space motion V jet % 260 km s À1 . The presence of additional knots in the counterjet beyond the bow shock may indicate precession of the jet axis. The blueshifted jet includes two closely spaced knots within 10 00 and a distant bow shock (%21 00 ) southwest (P:A: % 223 ) of the source. The brightest knot in the jet is HH 409 A, a higher excitation more bullet-like shock with V s $ 90 km s À1 and V jet % 360 km s À1 . The average opening angles for both the jet and counterjet are similar, a $ 2 , and consistent with opening angles of lower mass T Tauri stars. The mass-loss rates in both lobes of the flow, despite the asymmetry of the knots, are also comparable, M out $ 1:0 ; 10 À8 M yr À1 . This suggests that variations in the mass outflow rate are not more than a factor of $2. Subject headingg s: ISM: Herbig-Haro objects -ISM: individual (HH 409 A, HH 409 C) -ISM: jets and outflowsshock waves -stars: individual ( HD 163296) -stars: preYmain-sequence
The Astrophysical Journal, 1982
The Astrophysical Journal, 1998
Long-standing questions regarding the temperature, gravity, mass, and radius of the well-known wh... more Long-standing questions regarding the temperature, gravity, mass, and radius of the well-known white dwarf Sirius B are considered in light of new data. Recently obtained Extreme Ultraviolet Explorer (EUV E) observations and reprocessed IUE NEWSIPS data have produced a new, well-deÐned e †ective temperature of 24,790^100 K and a surface gravity of log g \ 8.57^0.06 for Sirius B. A new Hipparcos parallax for the Sirius system of is used in conjunction with the above n \ 0A .37921^0A .00158 spectroscopic results and the previously published gravitational redshift to yield a mass of 0.984^0.074 and a radius of for the white dwarf. Combining these results with M _ R \ 0.0084^0.00025R _ the existing astrometric mass for Sirius B gives a reÐned mass estimate of M \ 1.034^0.026
The Astrophysical Journal, 2000
We present a study of available Hubble Space Telescope (HST) spectroscopic and imaging observatio... more We present a study of available Hubble Space Telescope (HST) spectroscopic and imaging observations of the low ionization nuclear emission line region (LINER) galaxy NGC 1052. The WFPC2 imagery clearly differentiates extended nebular Hα emission from that of the compact core. Faint Object Spectrograph (FOS) observations provide a full set of optical and UV data (1200-6800Å). These spectral data sample the innermost region (0."86 × 0."86 ∼ 82pc × 82pc) and exclude the extended Hα emission seen in the WFPC2 image. The derived emission line fluxes allow a detailed analysis of the physical conditions within the nucleus. The measured flux ratio for Hα/Hβ, F Hα /F Hβ = 4.53, indicates substantial intrinsic reddening, E(B-V)=0.42, for the nuclear nebular emission. This is the first finding of a large extinction of the nuclear emission line fluxes in NGC 1052. If the central ionizing continuum is assumed to be attenuated by a comparable amount, then the emission line fluxes can be reproduced well by a simple photoionization model using a central power law continuum source with a spectral index of α = −1.2 as deduced from the observed flux distribution. A multi-density, dusty gas gives the best fit to the observed emission line spectrum. Our calculations show that the small contribution from a highly ionized gas observed in NGC 1052 can also be reproduced solely by photoionization modeling. The high gas covering factor determined from our model is consistent with the assumption that our line of sight to the central engine is obscured.
The Astrophysical Journal, 1993
The Astrophysical Journal, 1997
We present the results of our 1994 January and 1995 January observations of the quasar 3C 273 obt... more We present the results of our 1994 January and 1995 January observations of the quasar 3C 273 obtained with the International Ultraviolet Explorer (IUE) and the Extreme-Ultraviolet Explorer (EUV E).
![Research paper thumbnail of A L[CLC]y[/CLC]α Bright Jet from a Herbig A[CLC]e[/CLC] Star](https://attachments.academia-assets.com/41440936/thumbnails/1.jpg)
](The Astrophysical Journal, 2000
We report the detection in Lya of a collimated, bipolar outflow (HH 409) associated with the 1.5-... more We report the detection in Lya of a collimated, bipolar outflow (HH 409) associated with the 1.5-10 Myr old Herbig Ae star HD 163296. A blueshifted jet is visible in Lya and Si iii extending toward the southwest for at least 6Љ (725 AU). The combination of low line-of-sight extinction and relative faintness of the central star near Lya enables us to trace the jet to within an unprecedented 0Љ .06 (7.3 AU) of HD 163296. The jet has a radial velocity of 335-380 km s Ϫ1 , which is common for protostellar outflows. We also detected redshifted Lya emission southwest of the star that may be due to infall or a poorly collimated wind component. If the age of the star is correct, then protostellar outflows may last up to 10 times longer than previously believed.
The Astrophysical Journal, 2005
We focus on two Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) spectra of... more We focus on two Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) spectra of the Weigelt Blobs B&D, extending from 1640 to 10400Å; one recorded during the 1998 minimum (March 1998) and the other recorded in February 1999, early in the following broad maximum. The spatially-resolved spectra suggest two distinct ionization regions. One structure is the permanently low ionization cores of the Weigelt Blobs, B&D, located several hundred AU from the ionizing source. Their spectra are dominated by emission from H I, [N II], Fe II, [Fe II], Ni II, [Ni II], Cr II and Ti II. The second region, relatively diffuse in character and located between the ionizing source and the Weigelt Blobs, is more highly ionized with emission from [Fe III]
The Astrophysical Journal, 2005
The very massive star, Eta Carinae (η Car) , is enshrouded in an unusual complex of stellar eject... more The very massive star, Eta Carinae (η Car) , is enshrouded in an unusual complex of stellar ejecta, which is highly depleted in C and O, and enriched in He and N. This circumstellar gas gives rise to distinct absorption components corresponding to at least 20 different velocities along the line-of-sight. The velocity component at −513 km s −1 exhibits very low ionization with predominantly neutral species of iron-peak elements. Our statistical equilibrium/photoionization modeling indicates that the low temperature (T = 760 K) and high density (n H ∼10 7 cm −3 ) of the −513 km s −1 component is conducive to molecule formation including those with the elements C and O. Examination of echelle spectra obtained with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST) confirms the model's predictions. The molecules, H 2 , CH, and most likely OH, have been identified in the −513 km s −1 absorption spectrum. This paper presents the analysis of the HST/STIS spectra with the deduced column densities for CH, OH and C I, and upper limit for CO. It is quite extraordinary to see molecular species in a cool environment at such a high velocity. The sharp molecular and ionic absorptions in this extensively CNOprocessed material offers us a unique environment for studying the chemistry, dust formation processes, and nucleosynthesis in the ejected layers of a highly evolved massive star.
The Astrophysical Journal, 1980
We have observed the extensive circumstellar disk (Kuiper Belt) of beta Pictoris using the WFPC2/... more We have observed the extensive circumstellar disk (Kuiper Belt) of beta Pictoris using the WFPC2/PC aboard the Hubble Space Telescope. We have used the pyramid of the WFPC2 to image separately the central star on a different CCD chip than that of the disk. This eliminated bleeding and other effects inherent in the CCDs, thereby leaving the PC chip containing
We present preliminary results for observations obtained by the Far-Ultraviolet Spectral Explorer... more We present preliminary results for observations obtained by the Far-Ultraviolet Spectral Explorer (FUSE) of three Wolf-Rayet pre-white dwarfs, the nuclei of NGC 6905, NGC 5189, and NGC 5315. These stars represent some of the hottest objects (Teff 100-170k K) in the H-R diagram. All three stars display ultra-high ionization emission lines, most notably emission from hydrogen-like O V III at
Proceedings of the International Astronomical Union, 2009
We derive a substantially improved ephemeris for HD 209-458b based on photometric transit observa... more We derive a substantially improved ephemeris for HD 209-458b based on photometric transit observations. I-band observations taken at SDSU's Mount Laguna Observatory during the 2001, 2002, and 2003 observing seasons were combined with transit observations by the Hubble Space Telescope STIS (Brown et al. 2001) and FGS (Schultz et al. 2003), and additional ground-based APT photometry. The Eclipsing Light Curve
Examination of high resolution (R 100,000) echelle spectra of the nearby, hot DA white dwarf, G19... more Examination of high resolution (R 100,000) echelle spectra of the nearby, hot DA white dwarf, G191-B2B, obtained by the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST) reveals two velocity components to the C IV resonance doublet at 1548 and 1550 Angstroms. One component is clearly photospheric and corresponds to the common velocity of other established photospheric
Coronagraphic imaging with STIS on the HST reveals an 450 AU circumstellar disk around the 4-10 M... more Coronagraphic imaging with STIS on the HST reveals an 450 AU circumstellar disk around the 4-10 Myr old Herbig Ae star HD 163296. A broad-band (0.2-1.1 micron) reflected light image shows the disk oriented with its semi-major axis at PA=140+/-5 degrees, and inclination of 60+/-5 degrees. The disk includes an annulus of depleted material at 325 AU, and a flat
We summarize a free-flying occulter proposal that was submitted to NASA in response to NRA-01-OSS... more We summarize a free-flying occulter proposal that was submitted to NASA in response to NRA-01-OSS-04. Free-flying occulters in association with space telescopes have been proposed for nearly four decades to detect and study extrasolar planets. External occulters reduce the magnitude differences between a planet and the host star; light scatter within the telescope is reduced resulting from fewer obstructions and
Applications of Photonic Technology 4, 2000
We present a novel coronagraphic imaging technique and design for space-based telescopes. The Umb... more We present a novel coronagraphic imaging technique and design for space-based telescopes. The Umbral Mission Blocking Radiating Astronomical Sources (UMBRAS) is a space mission design consisting of a free flying occulter, the Solar Powered Ion Driven Eclipsing Rover (SPIDER), and possibly one or two metrology platforms. The UMBRAS spacecraft operate in conjunction with a space-based telescope. The size of the occulting SPIDER is dictated by the size of the telescope with which it will work. The goal of UMBRAS is to provide "paleolithic" (i.e., non-focal plane) coronagraphic capability to enable direct imaging of extrasolar Jovian planets and other bright substellar companions such as brown dwarfs.
Astronomy and …, 1997
... 1994, Walter et al. ... Symp., Evolution in Astrophysics, ed. EJ Rolfe, ESA-SP 310, p. 315 Fr... more ... 1994, Walter et al. ... Symp., Evolution in Astrophysics, ed. EJ Rolfe, ESA-SP 310, p. 315 Freire Ferrero R., Catalano S., Marilli E., Wonnacott D. Bruhweiler F., Talavera A. 1993 in: Advances in Stellar and Solar Coronal Physics, GS Vaiana Memorial Symposium, eds JL Linsky, S ...
The very massive star, Eta Carinae, is enshrouded in an unusual complex environment of nebulositi... more The very massive star, Eta Carinae, is enshrouded in an unusual complex environment of nebulosities and structures. The circumstellar gas gives rise to distinct absorption and emission components at different velocities and distances from the central source(s). Through photoionization modeling, we find that the radiation field from the more massive B-star companion supports the low ionization structure throughout the 5.54 year period. The radiation field of an evolved O-star is required to produce the higher ionization emission seen across the broad maximum. Our studies utilize the HST/STIS data and model calculations of various regimes from doubly ionized species (T= 10,000K) to the low temperature (T = 760 K) conditions conductive to molecule formation (CH and OH). Overall analysis suggests the high depletion in C and O and the enrichment in He and N. The sharp molecular and ionic absorptions in this extensively CNO - processed material offers a unique environment for studying the...
The Astrophysical Journal, 2006
We present an observational picture of the HH 409 bipolar outflow including the detection of six ... more We present an observational picture of the HH 409 bipolar outflow including the detection of six previously unreported Herbig-Haro knots from the Herbig Ae star HD 163296. This study combines seven years of data from ground-based Fabry-Pérot and HST coronagraphic imagery, as well as HST long-slit spectral imagery. The redshifted counterjet includes a chain of six Herbig-Haro knots spanning >27 00 to the northeast (P:A: % 42 ) of the source and has been active for >80 yr. The brightest knot in the counterjet is HH 409 C, a low-excitation bow shock with a shock velocity V s $ 50 km s À1 and total space motion V jet % 260 km s À1 . The presence of additional knots in the counterjet beyond the bow shock may indicate precession of the jet axis. The blueshifted jet includes two closely spaced knots within 10 00 and a distant bow shock (%21 00 ) southwest (P:A: % 223 ) of the source. The brightest knot in the jet is HH 409 A, a higher excitation more bullet-like shock with V s $ 90 km s À1 and V jet % 360 km s À1 . The average opening angles for both the jet and counterjet are similar, a $ 2 , and consistent with opening angles of lower mass T Tauri stars. The mass-loss rates in both lobes of the flow, despite the asymmetry of the knots, are also comparable, M out $ 1:0 ; 10 À8 M yr À1 . This suggests that variations in the mass outflow rate are not more than a factor of $2. Subject headingg s: ISM: Herbig-Haro objects -ISM: individual (HH 409 A, HH 409 C) -ISM: jets and outflowsshock waves -stars: individual ( HD 163296) -stars: preYmain-sequence
The Astrophysical Journal, 1982
The Astrophysical Journal, 1998
Long-standing questions regarding the temperature, gravity, mass, and radius of the well-known wh... more Long-standing questions regarding the temperature, gravity, mass, and radius of the well-known white dwarf Sirius B are considered in light of new data. Recently obtained Extreme Ultraviolet Explorer (EUV E) observations and reprocessed IUE NEWSIPS data have produced a new, well-deÐned e †ective temperature of 24,790^100 K and a surface gravity of log g \ 8.57^0.06 for Sirius B. A new Hipparcos parallax for the Sirius system of is used in conjunction with the above n \ 0A .37921^0A .00158 spectroscopic results and the previously published gravitational redshift to yield a mass of 0.984^0.074 and a radius of for the white dwarf. Combining these results with M _ R \ 0.0084^0.00025R _ the existing astrometric mass for Sirius B gives a reÐned mass estimate of M \ 1.034^0.026
The Astrophysical Journal, 2000
We present a study of available Hubble Space Telescope (HST) spectroscopic and imaging observatio... more We present a study of available Hubble Space Telescope (HST) spectroscopic and imaging observations of the low ionization nuclear emission line region (LINER) galaxy NGC 1052. The WFPC2 imagery clearly differentiates extended nebular Hα emission from that of the compact core. Faint Object Spectrograph (FOS) observations provide a full set of optical and UV data (1200-6800Å). These spectral data sample the innermost region (0."86 × 0."86 ∼ 82pc × 82pc) and exclude the extended Hα emission seen in the WFPC2 image. The derived emission line fluxes allow a detailed analysis of the physical conditions within the nucleus. The measured flux ratio for Hα/Hβ, F Hα /F Hβ = 4.53, indicates substantial intrinsic reddening, E(B-V)=0.42, for the nuclear nebular emission. This is the first finding of a large extinction of the nuclear emission line fluxes in NGC 1052. If the central ionizing continuum is assumed to be attenuated by a comparable amount, then the emission line fluxes can be reproduced well by a simple photoionization model using a central power law continuum source with a spectral index of α = −1.2 as deduced from the observed flux distribution. A multi-density, dusty gas gives the best fit to the observed emission line spectrum. Our calculations show that the small contribution from a highly ionized gas observed in NGC 1052 can also be reproduced solely by photoionization modeling. The high gas covering factor determined from our model is consistent with the assumption that our line of sight to the central engine is obscured.
The Astrophysical Journal, 1993
The Astrophysical Journal, 1997
We present the results of our 1994 January and 1995 January observations of the quasar 3C 273 obt... more We present the results of our 1994 January and 1995 January observations of the quasar 3C 273 obtained with the International Ultraviolet Explorer (IUE) and the Extreme-Ultraviolet Explorer (EUV E).
The Astrophysical Journal, 2000
We report the detection in Lya of a collimated, bipolar outflow (HH 409) associated with the 1.5-... more We report the detection in Lya of a collimated, bipolar outflow (HH 409) associated with the 1.5-10 Myr old Herbig Ae star HD 163296. A blueshifted jet is visible in Lya and Si iii extending toward the southwest for at least 6Љ (725 AU). The combination of low line-of-sight extinction and relative faintness of the central star near Lya enables us to trace the jet to within an unprecedented 0Љ .06 (7.3 AU) of HD 163296. The jet has a radial velocity of 335-380 km s Ϫ1 , which is common for protostellar outflows. We also detected redshifted Lya emission southwest of the star that may be due to infall or a poorly collimated wind component. If the age of the star is correct, then protostellar outflows may last up to 10 times longer than previously believed.
The Astrophysical Journal, 2005
We focus on two Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) spectra of... more We focus on two Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) spectra of the Weigelt Blobs B&D, extending from 1640 to 10400Å; one recorded during the 1998 minimum (March 1998) and the other recorded in February 1999, early in the following broad maximum. The spatially-resolved spectra suggest two distinct ionization regions. One structure is the permanently low ionization cores of the Weigelt Blobs, B&D, located several hundred AU from the ionizing source. Their spectra are dominated by emission from H I, [N II], Fe II, [Fe II], Ni II, [Ni II], Cr II and Ti II. The second region, relatively diffuse in character and located between the ionizing source and the Weigelt Blobs, is more highly ionized with emission from [Fe III]
The Astrophysical Journal, 2005
The very massive star, Eta Carinae (η Car) , is enshrouded in an unusual complex of stellar eject... more The very massive star, Eta Carinae (η Car) , is enshrouded in an unusual complex of stellar ejecta, which is highly depleted in C and O, and enriched in He and N. This circumstellar gas gives rise to distinct absorption components corresponding to at least 20 different velocities along the line-of-sight. The velocity component at −513 km s −1 exhibits very low ionization with predominantly neutral species of iron-peak elements. Our statistical equilibrium/photoionization modeling indicates that the low temperature (T = 760 K) and high density (n H ∼10 7 cm −3 ) of the −513 km s −1 component is conducive to molecule formation including those with the elements C and O. Examination of echelle spectra obtained with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST) confirms the model's predictions. The molecules, H 2 , CH, and most likely OH, have been identified in the −513 km s −1 absorption spectrum. This paper presents the analysis of the HST/STIS spectra with the deduced column densities for CH, OH and C I, and upper limit for CO. It is quite extraordinary to see molecular species in a cool environment at such a high velocity. The sharp molecular and ionic absorptions in this extensively CNOprocessed material offers us a unique environment for studying the chemistry, dust formation processes, and nucleosynthesis in the ejected layers of a highly evolved massive star.
The Astrophysical Journal, 1980