Space Telescope Faint Object Camera Research Articles

Resolving LB 11146 withHubble Space Telescope's Fine Guidance Sensor

On the basis of its observed spectra, LB 11146 was identified as a binary system composed of pair of massive (∼0.9 M⊙) white dwarf stars. However, observations with the Hubble Space Telescope (HST) Faint Object Camera did not resolve the system, and searches for radial velocity variations yielded null results. Subsequent observations of LB 11146 with the HST's Fine Guidance Sensor have resolved the system at three epochs spanning 295 days, thereby confirming the binary nature of this object. We find a nearly constant component separation of approximately 15 mas and a large change in position angle, consistent with a low-inclination, low-eccentricity orbit with a period of approximately 130 days. At a distance of 40 pc, this corresponds to a component separation of about 0.6 AU, which in turn also results in a Keplerian orbit with a period of about 130 days, assuming the spectroscopic masses of the white dwarfs. The size of the orbit is significantly smaller than the size of the progenitor stars as they evolved through the asymptotic giant branch, so one or more phases of binary star evolution is likely to have occurred. LB 11146 joins PG 1115+116, but in a more extreme sense, as an example of a close binary composed of massive white dwarfs that did not evolve to become a short-period system, thereby providing an additional key observational test for models of binary star evolution.

The Cuspy Liner Nucleus of the S0/a Galaxy NGC 2681

The nucleus of the bulge-dominated, multiply barred S0/a galaxy NGC 2681 is studied in detail using the high-resolution Hubble Space Telescope Faint Object Camera (FOC), Near-Infrared Camera and Multiobject Spectrometer (NICMOS) imaging, and the Faint Object Spectrograph (FOS). The ionized gas central velocity dispersion is found to increase by a factor ≈2 when narrowing the aperture from R ≈ 15 (ground) to R ≈ 01 (FOS). Dynamical modeling of these velocity dispersions suggests that NGC 2681 does host a supermassive black hole (BH) for which one can estimate a firm mass upper limit MBH ≲ 6 × 107 M☉. This upper limit is consistent with the relation between the central BH mass and velocity dispersion MBH - σ known for other galaxies. The emission-line ratios place the nucleus of NGC 2681 among LINERs. It is likely that the emission-line region comes from a rather mild, but steady, feeding of gas to the central BH in this galaxy. The inner stellar population lacks any measurable color gradient (to a radius of 0.6 kpc) from the infrared to the ultraviolet, consistently with FOC, FOS, and IUE data, all indicating that this system underwent a starburst ≈1 Gyr ago that encompassed its whole interior, down to its very center. The most likely source of such a widely distributed starburst is the dumping of tidally extruded gas from a galaxy neighbor. If so, then NGC 2681 can be considered as the older brother of M82, seen face-on as opposed to the edge-on view we have for M82.

On the Nuclear Rotation Curve of M31

The currently favored model for the double nucleus of M31 consists of an eccentric disk with an off-center density concentration caused by stars lingering at the apocenters of their orbits about the central black hole. If such a disk is to be in equilibrium, the requirement that it precess uniformly because of self-gravity imposes a characteristic radial structure on the orbits that comprise it, creating an observable feature in the rotation curve. The sequence of closed orbits through the densest part of the disk must follow a steep eccentricity gradient, which reverses the arrangement of pericenter and apocenter with respect to the central mass. Stars making up the inner part of the density concentration are at apocenter, while stars making up the outer part are at pericenter, producing a steep local velocity gradient and a distinctive in the projected rotation curve near the eccentric density peak. This wiggle closely resembles a feature seen near the off-center brightness peak (P1) in the nuclear rotation curve observed by the Hubble Space Telescope Faint Object Camera Spectrograph. If confirmed by upcoming Space Telescope Imaging Spectrograph observations, this feature will lend further strong support to the eccentric disk picture and provide important constraints for more realistic dynamical models.

ITAL]HUBBLE SPACE TELESCOPE[/ITAL][ITAL]Hubble Space Telescope[/ITAL] Ultraviolet Spectral Energy Distributions for Three Ultraluminous Infrared Galaxies

We present Hubble Space Telescope Faint Object Camera ultraviolet (λ = 2300 A, 1400 A) images of three ultraluminous infrared galaxies (ULIGs: Lir > 1012 L⊙) selected from the IRAS Revised Bright Galaxy Sample. The purpose is to estimate spectral energy distributions (SEDs) to facilitate the identification of similar objects at high redshift in deep optical, infrared, and submillimeter surveys. All three galaxies, VII Zw 031 (=IRAS F05081+7936), IRAS F12112+0305, and IRAS F22491-1808, were well detected with the F220W filter. Two of the three were marginally detected with the F140W filter. The fluxes, together with ground-based optical and infrared photometry, are used to compute SEDs over a wide wavelength range. The measured SEDs drop from the optical to the ultraviolet, but the magnitude of the drop ranges from a factor of ~3 in IRAS F22491-1808 to a factor of ~100 in VII Zw 031. This is most likely due to different internal extinctions. Such an interpretation is also suggested by extrapolating to ultraviolet wavelengths the optical internal extinction measured in VII Zw 031. K-corrections are calculated to determine the colors of the sample galaxies as seen at high redshifts. Galaxies such as VII Zw 031 have very low observed rest-frame UV fluxes, which means that such galaxies at high redshift will be extremely red or even missing in optical surveys. On the other hand, galaxies such as IRAS F12112+0305 and IRAS F22491-1808, if seen at high redshift, would be sufficiently blue that they would not easily be distinguished from normal field galaxies and therefore, identified as ULIGs. The implication is then that submillimeter surveys may be the only means of properly identifying the majority of ULIGs at high redshift.

The Origin of the Narrow‐Line Region of Markarian 3: An Overpressured Jet Cocoon

We have obtained Hubble Space Telescope (HST) Faint Object Camera (FOC) f/48 long-slit optical spectroscopy of the inner 2'' of the narrow-line region (NLR) of the Seyfert 2 galaxy Mrk 3 with a spatial resolution of 006. Spectra were taken in six locations with the slit approximately perpendicular to the radio axis. In the region cospatial with the radio jet, where the brightest emission line knots are located, the velocity field is highly perturbed, showing two velocity systems separated by as much as 1700 km s-1. In several locations the split lines form almost complete velocity ellipsoids, implying that we are seeing an expanding shell of gas. The diameter of this shell (~200 pc) is much larger than the width of the radio jet (d<15 pc). We interpret this to be the consequence of the rapid expansion of a cocoon of hot gas, shocked and heated by the radio-emitting outflow, which compresses and accelerates the ambient gas. The cocoon mediates the energy exchange between jets and the line-emitting gas. The gas motions within the NLR of Mrk 3 are therefore clearly dominated by the interaction between the jets and the interstellar medium; the NLR itself is essentially a cylindrical shell expanding supersonically. With its current size of 200 pc, the cocoon has expanded to several disk scale heights. Because of the external gas density stratification, the hot gas located above the plane of the disk blows out into the halo, puncturing the bubble and fracturing the velocity ellipsoids. The system is effectively momentum driven. From the size and velocity of the expanding region, we derive an upper limit to the age of the radio source of 1.5?105 yr, and a lower limit for the jet power of 2?1042 ergs s-1, required to inflate the cocoon; we estimate that the jet minimum advance speed is 3?10-3 pc yr-1. The total kinetic energy of the high-velocity gas associated with the radio jet can be estimated as ~6?1054 ergs, comparable to the total energy carried by the jet over its lifetime; this quantitatively supports the idea that the NLR gas is accelerated by the jet. Radio outflows are associated with at least 50% of Seyfert galaxies with typical sizes smaller than a few kpc. If the advance speed of Mrk 3 is representative of the Seyfert population, then these sources must also be short lived and are probably recurrent. Evidence that this is indeed the case is provided by the fact that the expansion timescale derived for NGC 1068 is comparable to that seen in Mrk 3. The jet kinetic luminosity of Mrk 3 is between 2 and 3 orders of magnitude smaller than that derived for radio-loud AGNs with similar emission-line luminosity. On the other hand, the fraction of jet power dissipated in radio emission is similar. We speculate that the main distinction between radio-quiet and radio-loud active galactic nuclei can be ascribed to a difference in jet power rather than to a different efficiency in synchrotron emission production.

The Very Young Starburst Merger System NGC 1741

We use Hubble Space Telescope (HST) Faint Object Camera (FOC) ultraviolet (UV) and WFPC2 optical images in conjunction with UV spectroscopic observations taken with the Goddard High Resolution Spectrograph to examine the star formation history and properties of the interacting galaxy system NGC 1741 in the Hickson Compact Group 31. The high spatial resolution afforded by HST has allowed us to identify a large number of starburst knots, or super?star clusters (SSCs), in the starburst regions of this system. Photometry of these SSCs in the UV and optical bands indicates that most of these objects have ages of a few Myr, with a few up to ?100 Myr, and masses between 104 and 106 M?. The estimated age is confirmed by a spectral synthesis analysis of one knot for which we have obtained a UV spectrum. The V-band luminosity function of the SSCs is well represented by a power law (L) ~ L-? with an index of -1.85, with no evidence of a turnover brighter than the completeness limit. These properties are in good agreement with those found for SSCs in other starburst galaxies. Our results support the suggestion that some of these SSCs may be extremely young globular clusters formed in a relatively recent starburst episode that has been triggered by a merger event.

Stellar Kinematics of the Double Nucleus of M31

We report observations of the double nucleus of M31 with the f/48 long-slit spectrograph of the Hubble Space Telescope Faint Object Camera. We obtain a total exposure of 19,000 s over seven orbits, with the 0063-wide slit along the line between the two brightness peaks (P.A. 42°). Careful correction of the raw data for detector backgrounds and geometric distortion is essential. A spectrum of Jupiter obtained with the same instrument is used as a spectral template to extract rotation and velocity profiles by cross-correlation. The rotation curve is resolved and reaches a maximum amplitude of ~250 km s-1 roughly 03 to either side of a rotation center lying between peaks P1 and P2, 016 ± 005 from the optically fainter P2. We find the velocity to be 250 km s-1 everywhere except for a narrow dispersion spike centered 006 ± 003 on the anti-P1 side of P2, in which σ peaks at 440 ± 70 km s-1. At much lower confidence, we see local disturbances to the rotation curve at P1 and P2 and an elevation in σ at P1. At very low significance we detect a weak asymmetry in the line-of-sight velocity distribution opposite to the sense usually encountered. Convolving our V and σ profiles to Canada-France-Hawaii Telescope resolution, we find good agreement with the forthcoming results of Kormendy & Bender, although there is a 20% discrepancy in the that cannot be attributed to the spike. Our results are not consistent with the location of the maximum found by Bacon et al. in 1994. Comparing with published models, we find that the more recent sinking star cluster model of Emsellem & Combes does not reproduce either the rotation curve or the profile. The eccentric-disk model proposed by Tremaine fares better and can be improved somewhat by adjusting the original parameters. However, detailed modeling will require dynamical models of significantly greater realism.

Detailed study of FUV Jovian auroral features with the post‐COSTAR HST faint object camera

A set of Hubble Space Telescope faint object camera images taken in the H2 bands near 1550 Å is used to infer the morphological properties of the steady state Jovian FUV aurorae. We focus on issues best addressed using the excellent spatial resolution available after correction of the spherical aberration, i.e., those related to high latitude or small auroral features. A thorough comparison of the emission loci with model ovals highlights the improvement of the VIP4 magnetic field model over previous ones at all latitudes. The north‐south conjugacy of the main oval is now correctly accounted for, and second‐order discrepancies suggest non axially symmetric contributions of external origin. This oval is usually amazingly narrow (down to 80±50 km) and very bright, although quite variable with time (100 kR to 1–2 MR, i.e., peak input flux of ∼10–200 ergs cm−2 s−1). We discuss its structure, in latitude and longitude, and show that it is consistent with precipitation by pitch angle scattering. Fainter concentric narrow ovals are also present on the north polar cap, presumably at the footprint of open field lines. Both polar caps are partly covered by a faint diffuse emission, confined to the afternoon sector in magnetic local time. A bright extended feature, previously identified across the north polar cap along the 160° meridian, might be not a specific auroral feature but rather a region where inner arcs and diffuse polar cap emissions are intensified, maybe by a solar wind driven ionospheric process. Equatorward of the main oval, we identify a belt of moderate emission, attributed to a precipitation process distributed between the Io torus and the distant magnetosphere. Longitudinally confined bright areas lie in the same latitude range and consist of series of short segments of concentric arcs. We also present the discovery of a narrow faint oval at the footprint of Io's orbit. Finally, we confirm that the FUV footprints of the Io flux tube are very small (a few hundreds of kilometers or less), implying an interaction close to Io. The input energy flux in this spots is huge and variable (0.8–5 × 1011W).

Jet-Driven Motions in the Narrow-Line Region of NGC 1068

We have obtained Hubble Space Telescope Faint Object Camera (FOC) f/48 long-slit spectroscopy of the inner 4'' of the narrow-line region (NLR) of NGC 1068 between 3500 and 5400 A with a spectral resolution of 1.78 A pixel-1. At a spatial scale of 00287 pixel-1 these data provide an order-of-magnitude improvement in resolution over previous ground-based spectra and allow us to trace the interaction between the radio jet and the gas in the NLR. Our results show that within ±05 of the radio jet the emission lines are kinematically disturbed and split into two components whose velocity separation is 1500 km s-1. The filaments associated with the radio lobe also show a redshifted kinematic disturbance on the order of 300 km s-1, which is probably a consequence of the expansion of the radio plasma. Furthermore, the material enveloping the radio jet is in a much higher ionization state than that of the surrounding NLR gas. The highest excitation is coincident with the jet axis, where emission in the coronal line of [Fe VII] λ3769 is detected and the He II λ4686 is strong but where [O II] λ3727 is depressed. This large localized increase in ionization on the jet axis is accompanied by the presence of an excess continuum. Because the electron density is substantially larger in the jet compared with the surrounding NLR, these results can be explained only if there is a more intense ionizing continuum associated with the jet. This can be accomplished in a variety of ways, which include an intrinsically anisotropic nuclear radiation field, a reduced gas covering factor, or the presence of a local ionization source. The morphology, kinematics, and, possibly, the ionization structure of the NLR in the vicinity of the jet of NGC 1068 are a direct consequence of the interaction with the radio outflow.

ITAL]Hubble Space Telescope[/ITAL] Observations of the Middle-aged Pulsar 0656+14

Multiwavelength spectral observations of middle-aged (τ~104-106 yr) isolated pulsars enable one in principle to separate thermal radiation emitted from the neutron star surface and nonthermal radiation from its magnetosphere. We have previously detected the middle-aged radio and soft X-ray pulsar 0656+14 with the Hubble Space Telescope Faint Object Camera (FOC) long-pass filter F130LP. In the present Letter we report new FOC observations of this pulsar with three broadband filters: F430W, F342W, and F195W. The optical-UV spectral flux can be fitted with a two-component spectral model that combines a power-law spectrum with a Rayleigh-Jeans spectrum. The nonthermal component with the power-law index α=1.4−0.7+ 0.6 dominates at λ3000 A. The thermal component is characterized by the Rayleigh-Jeans parameter, G ≡ T6(R10/d500)2, where T=106T6 K is the brightness temperature, R=10R10 km is the neutron star radius as seen by a distant observer, and d=500d500 pc is the distance. For a plausible extinction, E(B-V)=0.03, we obtained G=3.6+ 1.6−2.0. The observed shape of the optical-UV spectrum of PSR 0656+14 differs drastically from those of both younger pulsars (Crab, 0540-69, Vela) and the older pulsar Geminga.

Hubble Space Telescope Faint Object Camera calculated point-spread functions

A set of observed noisy Hubble Space Telescope Faint Object Camera point-spread functions is used to recover the combined Hubble and Faint Object Camera wave-front error. The low-spatial-frequency wave-front error is parameterized in terms of a set of 32 annular Zernike polynomials. The midlevel and higher spatial frequencies are parameterized in terms of set of 891 polar-Fourier polynomials. The parameterized wave-front error is used to generate accurate calculated point-spread functions, both pre- and post-COSTAR (corrective optics space telescope axial replacement), suitable for image restoration at arbitrary wavelengths. We describe the phase-retrieval-based recovery process and the phase parameterization. Resultant calculated precorrection and postcorrection point-spread functions are shown along with an estimate of both pre- and post-COSTAR spherical aberration.

Motion of the Ultraviolet R Aquarii Jet

We present evidence for subarcsecond changes in the ultraviolet (~2550 A) morphology of the inner 5 arcseconds of the R Aqr jet over a 2 yr period. These data were taken with the Hubble Space Telescope (HST) Faint Object Camera (FOC) when the primary mirror flow was still affecting observations. Images of the R Aqr stellar jet were successfully restored to the original design resolution by completely characterizing the telescope-camera point spread function (PSF) with the aid of phase-retrieval techniques. Thus, a noise-free PSF was employed in the final restorations which utilized the maximum entropy method (MEM). We also present recent imagery obtained with the HST/FOC system after the COSTAR correction mission that provides confirmation of the validity of our restoration methodology. The restored results clearly show that the jet is flowing along the northeast (NE)-southwest (SW) axis with a prominent helical-like structure evident on the stronger NE side of the jet. Transverse velocities increase with increasing distance from the central source, providing a velocity range of 36-235 km s-1. From an analysis of proper motions of the two major ultraviolet jet components, we detect an ~40.2 yr event separation of this apparent enhanced material ejection occurring probably at periastron which is consistent with the suspected ~44 yr binary period; this same analysis shows that the jet is undergoing nonlinear acceleration which suggests that the propulsive force probably results from magnetohydromagnetic effects. The restoration computations and the algorithms employed demonstrate that mining of flawed HST data can be scientifically worthwhile.

ITAL]Hubble Space Telescope[/ITAL] Discovers Optical Emission from the Radio Pulsar PSR 1055−52

Optical/UV emission from isolated neutron stars, if detected, represents a valuable indicator of the pulsar's emission mechanisms, and more so for those objects of "intermediate" age, where thermal and nonthermal processes are known to coexist. PSR 1055-52 is a middle-aged pulsar and a strong γ-ray emitter. As such, it represents a logical target, but the presence of a nearby star renders optical ground-based searches totally hopeless. The Hubble Space Telescope Faint Object Camera (FOC), however, was successful in detecting the pulsar's emission through its U (F342) filter. It is interesting to compare such emission with an extrapolation of the soft, thermal part of the ROSAT X-ray spectrum. Within the uncertainties, it appears that the FOC flux is compatible with the Rayleigh-Jeans side of such a spectrum, as was the case for Geminga, in many ways a similar object. PSR 1055-52 becomes one of three pulsars (besides the Crab and Vela) visible at all wavelengths.

An Atlas of Hubble Space Telescope Ultraviolet Images of Nearby Galaxies

We present an atlas of UV ($\sim 2300$ \AA) images, obtained with the Hubble Space Telescope (HST) Faint Object Camera, of the central $22''\times 22''$ of 110 galaxies. The observed galaxies are an unbiased selection constituting about one half of a complete sample of all large ($D>6'$) and nearby ($V< 2000$ km s$^{-1}$) galaxies. This is the first extensive UV imaging survey of normal galaxies. The data are useful for studying star formation, low-level nuclear activity, and UV emission by evolved stellar populations in galaxies. At the HST resolution ($\sim 0.05''$), the images display an assortment of morphologies and UV brightnesses. These include bright nuclear point sources, compact young star clusters scattered in the field or arranged in circumnuclear rings, centrally-peaked diffuse light distributions, and galaxies with weak or undetected UV emission. We measure the integrated $\sim 2300$ \AA flux in each image, classify the UV morphology, and examine trends between these parameters and the optical properties of the galaxies.

Correction: Rapid energy dissipation and variability of the lo-Jupiter electrodynamic circuit

Nature 379, 323-325 (1995) IN Fig. 1 of this Letter, a dashed line was omitted that was referred to in the legend to Fig. 30. The corrected figure is shown here. Images of the FUV Jovian aurorae and of the far-ultraviolet signature of the lo magnetic flux tube with the Hubble Space Telescope Faint Object Camera (11 96).

Hubble Space Telescope far-ultraviolet imaging of M31, M32, and NGC 205

Hubble Space Telescope (HST) Faint Object Camera (FOC) f/48 images of M31, M32, and NGC 205 (field of view 23 sec x 23 sec with 0.45 sec pixel size) are analyzed as observed through the combined UV filters F150W and F130LP. The absolute calibration of the data and the internal disagreement between observed and expected count rates in the UV region lead us to suggest that the filter combination F150W+F130LP suffers from a 5 times degraded UV sensitivity. A corrected efficiency curve is construced using the UV/optical spectral energy distributions of these three galaxies, which is consistent with all of the data analyzed here. Eighty-one individual stars are detected in M31, 10 stars in M32, and 78 stars in NGC 205. Comparisons with other UV images and optical images indicates that these stars are hot, UV-bright stars, even though our corrected efficiency curve suggests that flux from 1200-2450 A contributes only 7% of the counts in M32, 19% in M31, and 60% in NGC 205. The complex nucleus of M31 as seen by Lauer et al. (1993) is confirmed; M32 has a generally smooth appearance and NGC 205 is dominated by a UV-bright, somewhat resolved nucleus. Analysis of these data is done through the new, extensive stellar isochrones of Bertelli et al. (1994) and the population synthesis models of Bressan, Chiosi, and Fagotto (1994). This analysis shows that high-metal stars (Z greater than 0.05) evolve into UV-bright stars (P-EAGB, H-HB, and AGB-manque stars) that are less luminous and cooler but are significantly longer lived than the P-AGB stars produced by stars with Z less than 0.05. Moreover, the proportion of P-EAGB, H-HB, and AGB-manque stars is also a function of age, with older stars of fixed mean metallicity having a higher proportion than younger stars. Hence, with either metallicity or age differences as an interpretation of the line-strength luminosity correlation for ellipticals, the high-metallicity 'tail' of the stellar content of a galaxy can produce far-UV flux in much greater proportion than its actual proportion of galaxy mass. The resulting model of the sources of far-UV flux is inherently composite, with the total UV flux from a stellar population both rapidly increasing and changing its mean spectrum with increasing mean metallicity (or mean age). This model is consistent with several pieces of observational evidence.

IMAGING THE BIPOLAR NEBULA AROUND HM SAGITTAE

ABSTRACT Hubble Space Telescope Faint Object Camera UV images are presented for HM Sge showing a bipolar optical nebula similar to that in R Aquarii and RX Puppis. The nebula extends to a distance of 0.174" with a P.A. of 135 degrees inside a faint halo extending to a radius of 0.28". A kinematic distance to HM Sge based on positions of features in the nebula is found to be 1.77 ± 0.1 kpc. Comparisons between our UV images, radio maps taken in 1982 and IUE spectra all demonstrate that this system is still undergoing dramatic changes.

Imaging of four planetary nebulae in the Magellanic Clouds using the Hubble Space Telescope Faint Object Camera

view Abstract Citations (25) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Imaging of Four Planetary Nebulae in the Magellanic Clouds Using the Hubble Space Telescope Faint Object Camera Blades, J. C. ; Barlow, M. J. ; Albrecht, R. ; Barbieri, C. ; Boksenberg, A. ; Crane, P. ; Deharveng, J. M. ; Disney, M. J. ; Jakobsen, P. ; Kamperman, T. M. ; King, I. R. ; Macchetto, F. ; Mackay, C. D. ; Paresce, F. ; Weigelt, G. ; Baxter, D. ; Greenfield, P. ; Jedrzejewski, R. ; Nota, A. ; Osmer, S. ; Sparks, W. B. Abstract Using the Faint Object Camera on-board the Hubble Space Telescope, we have obtained images of four planetary nebulae (PNe) in the Magellanic Clouds, namely N2 and N5 in the SMC and N66 and N201 in the LMC. Each nebula was imaged through two narrow-band filters isolating [O III] λ5007 and Hβ, for a nominal exposure time of 1000 s in each filter. Significant detail is evident on the raw images and, after deconvolution using the Richardson-Lucy algorithm, structures as small as 0.06" are easily discernible. In [O III], SMC N5 shows a circular ring structure, with a peak-to-peak diameter of 0.26" and a FWHM of 0.35", while SMC N2 shows an elliptical ring structure with a peak-to-peak diameter of 0.26" x 0.21" (FWHM 0.40" x 0.35"). The expansion ages corresponding to the observed structures in SMC N2 and N5 are of the order of 3000 yr. Such low ages appear more easy to reconcile with helium-burning rather than hydrogen-burning central star evolutionary tracks. LMC N201 is very compact, with a FWHM of 0.21" in Hβ. The Type I PN LMC N66 is a multipolar nebula, with the brightest part having an extent of about 2" and with fainter structures extending over 4". The [O III] image reveals structures unprecedented for a planetary nebula, with several bright knots and faint loops visible outside the two main bright lobes. Publication: The Astrophysical Journal Pub Date: October 1992 DOI: 10.1086/186572 Bibcode: 1992ApJ...398L..41B Keywords: Faint Object Camera; Hubble Space Telescope; Magellanic Clouds; Planetary Nebulae; Spaceborne Astronomy; H Beta Line; Stellar Evolution; Stellar Structure; Astrophysics full text sources ADS | data products SIMBAD (7) NED (2) MAST (1) ESA (1)

Hubble Space Telescope Imaging of the North Polar Aurora on Jupiter

The first direct images of the Jovian aurora at ultraviolet wavelengths were obtained by the Hubble Space Telescope Faint Object Camera near the time of the Ulysses spacecraft encounter with Jupiter on 8 February 1992. The auroral oval is not uniformly luminous. It exhibits a brightness minimum in the vicinity of longitude 180 degrees . In the few images available, the brightest part of the oval occurs in late afternoon Jovian time. The observed oval is not concentric with calculated ovals in the O(6) model of Connerney. The size of the oval is consistent with auroral particles on field lines with magnetic L parameter >8, indicating significant migration from lo, its torus, or both, if these are their origins.

Preliminary analysis of an ultraviolet Hubble Space Telescope faint object camera image of the center of M31

A 5161 s exposure was taken with the FOC on the central 44 arcsec of M31, through a filter centered at 1750 A. Much of the light is redleak from visible wavelengths, but nearly half of it is genuine UV. The image shows the same central peak found earlier by Stratoscope, with a somewhat steeper dropoff outside that peak. More than 100 individual objects are seen, some pointlike and some slightly extended. We identify them as post-asymptotic giant branch stars, some of them surrounded by a contribution from their accompanying planetary nebulae. These objects contribute almost a fifth of the total UV light, but fall far short of accounting for all of it. We suggest that the remainder may result from the corresponding evolutionary tracks in a population more metal-rich than solar.