Engineering topics

Becklin, E. E.

Publications and source records attributed to Becklin, E. E..

At least 37 records · Page 2

NASA NTRS1988

Infrared spectroscopy, imaging, and 10 micron photometry of Giclas 29-38

An NIR spectrum and several images of Giclas 29-38, a white dwarf suspected to have a brown dwarf in orbit around it, are presented. There is no absorption feature in the spectrum that is deeper than 5 percent in the wavelength range 1.95-2.45 microns, from which it is inferred that there is no feature deeper than 10 percent at 2.4 microns from any brown dwarf companion. The IR spectrum does not yield any strong constraint on whether or not the thermal emission observed from G29-38 comes from a brown dwarf or dust. The 1.6- and 2.2-micron images of G29-38 appear indistinguishable from a point source with an upper limit of 0.4 arcsec for the separation of the white dwarf and the source of the excess IR emission. This corresponds to a projected linear separation of 5.6 AU. A 2sigma limit at 10 microns of 10 mJy constrains possible alternative models for the IR excess by emission from dust grains. While the present results do not show evidence for the suspected brown dwarf companion around G29-38, the presence of such an object cannot be ruled out.

Tokunaga, A. T.↗

NASA NTRS1988

Resolution of the circumstellar disk of Beta Pictoris at 10 and 20 microns

Observations at 10 and 20 microns with about 5 arcsec resolution are presented of the central, approximately 13 arcsec diameter region of the A5 dwarf Beta Pictoris. These observations resolve the inner disk and provide important constraints for models of the star and a basis for removing some of their ambiguities. The evidence indicates that submicron-sized grains emit much of the excess 10 and 20 micron radiation from the star. The characteristics of the dust are discussed, and the possibility that comets form the dust reservoir is considered.

Telesco, C. M.↗

NASA NTRS1987

Ground-based 1- to 32-microns observations of ARP 220: Evidence for a dust-embedded AGN?

New observations of the 10 and 20 micron size of the emission region in Arp 220 are presented. Also given are ground based photometry from 1 to 32 micron including measurements of the strength of the silicate feature at 10 micron. The results show that the 20 micron size of Arp is smaller than 1.5 arcsec (500 pc); comparison of IRAS and ground based observations show that IRAS 12 micron flux measured with a large arcmin beam is the same as that seen from the ground with a 3 arcsec aperture. At 10 micron a deep silicate absorption feature is seen that corresponds to a visual extinction of about 50 mag. These results suggest that a very significant portion of the 10 to the 12th power L sub 0 infrared luminosity from Arp 220 comes from a region less than or of the order of 500 pc in diameter. When these results are combined with recent measurement of a broad Brackett alpha line by DePoy and an unresolved 2.2 micron source by Neugebauer, Matthews and Scoville, a very attractive possibility for the primary luminosity source Arp 220 is a dust embedded compact Seyfert type nucleus.

Becklin, E. E.↗

NASA NTRS1987

Morphology of luminous IRAS galaxies: Summary talk

The author discusses the morphology of luminous Infrared Astronomy Satellite (IRAS) galaxies. A few comments are made about the direction to be taken in future observations of luminous IRAS galaxies.

Becklin, E. E.↗

NASA NTRS1986

Extreme limb profiles of the sun at far-infrared and submillimeter wavelengths

Thirty, 50, 100, and 200 microns solar limb intensity profiles determined with arcsecond resolution from airborne observations of the occultation of the solar limb during the total eclipse of July 31, 1981, are presented. Two points of particular importance emerge: (1) the longer-wavelength (100 and 200 micron) limbs are significantly brighter than disk center. At 200 microns the extreme limb is about 1.22 times the brightness of disk center. This is consistent with the 6000 K temperature-plateau structure of the model chromospheres of Vernazza, Avrett, and Loeser (1973, Ap. J., 184, 605; 1981; Ap. J. Suppl., 45, 635); and (2) the longer wavelength limbs are extended significantly further above the visible limb than Vernazza, Avrett, and Loeser predict. These results provide a strong basis for modeling of the solar chromosphere free from the assumption of gravitational-hydrostatic equilibrium.

Lindsey, C.↗

NASA NTRS1986

The 2 micron spectrum of NGC 6240 - Evidence for more than a starburst

The exceptionally luminous interacting galaxy NGC 6240 has been studied with infrared spectroscopy and photometry. Emission lines of molecular hydrogen and the Paschen-alpha line of ionized hydrogen have been detected. Broad-band 10 micron and 20 micron emission has also been observed. Combined with previous optical spectroscopy and results from IRAS, the observations show that NGC 6240 cannot be explained along the lines of a superstarburst of massive stars such as seen in M82. It may be more easily understood in terms of an active nucleus similar to Seyfert galaxies.

Depoy, D. L.↗

NASA NTRS1986

Extreme limb profiles of the sun at far-infrared and submillimeter wavelengths

Thirty, 50, 100, and 200 microns solar limb intensity profiles determined with arcsecond resolution from airborne observations of the occultation of the solar limb during the total eclipse of 1981 July 31 are presented. Two points of particular importance emerge: (1) the longer-wavelength (100 and 200 micron) limbs are significantly brighter than disk center. At 200 microns the extreme limb is about 1.22 times the brightness of disk center. This is consistent with the 6000 K temperature-plateau structure of the model chromospheres of Vernazza, Avrett, and Loeser (1973, Ap. J., 184, 605; 1981; Ap. J. Suppl., 45, 635;) and (2) the longer wavelength limbs are extended significantly further above the visible limb than Vernazza, Avrett, and Loeser predict. These results provide a strong basis for modeling of the solar chromosphere free from the assumption of gravitational-hydrostatic equilibrium.

Lindsey, C.↗

NASA NTRS1986

Simultaneous submillimeter and infrared observations of flat-spectrum radio sources

Observations are presented of 12 extragalactic nonthermal radio emission sources made at eight wavelengths between 1.25 and 1000 microns, including the important submillimeter wavelength of 350 microns. Nine of the objects were detected at 350 microns, roughly double the number of objects of this type that have previously been detected at this wavelength. The majority of the observations were made within a three-week time span. The results, combined with other studies, show that these objects generally have flat energy distributions at wavelengths longer than 1 mm that break in most cases between 350 microns and 1 mm. At wavelengths shorter than 1 mm, the energy distributions fall with a rough power-law behavior with a spectral index of about -1. For many of the objects, there is a definite break or curvature in the energy distributions at wavelengths near 2.2 microns, with the fluxes falling even more steeply into the near infrared. At the time of the observations, both OJ 287 and 3C 273 were undergoing flares. The results are generally consistent with the flares propagating out to longer wavelengths with time.

Roellig, T. L.↗

NASA NTRS1986

Infrared astronomy after IRAS

The development of infrared astronomy in the wake of IRAS is discussed. Attention is given to an overview of next generation infrared telescope technology, with emphasis on the Space Infrared Telescope Facility (SIRTF) which has been built to replace IRAS in the 1990s. Among the instruments to be included on SIRTF are: a wide-field high-resolution camera covering the infrared range 3-30 microns with large arrays of detectors; an imaging photometer operating in the range 3-700 microns; and a spectrograph covering the range 2.5-200 microns with resolutions of 2 and 0.1 percent. Observational missions for the SIRTF are proposed in connection with: planetary formation; star formation; cosmic energy sources; active galactic nuclei; and quasars.

Rieke, G. H.↗

NASA NTRS1985

The infrared size of IRc2/KL and its structure on an arcsecond scale

Small-aperture diffraction-limited scans of IRc2/KL at 7.8 and 12.5 microns are discussed. These scans, which were made at several position angles, spatially resolve the region within a 250 AU radius of this source, which is thought to be a newly formed luminous star undergoing heavy mass loss. IRc2 is found to have a pronounced elongation. The shape and orientation of this extended structure is similar to that seen on a larger scale in low-excitation molecular transitions, and is very similar to the distribution of H2O 'shell' masers. The size of the object may be reconciled with its dereddened blackbody temperature and total luminosity of 0.00001 solar luminosities (which is appropriate to OMC1) by the presence of small-scale structure. The observations thus support the idea that IRc2 is the primary luminosity source for OMC1. New astrometric measurements indicate that the 12.5 microns peak of IRc2 is coincident with the positions of the two bright SiO masers to within 0.3 arcsec.

Lester, D. F.↗

NASA NTRS1985

The IRAS galaxy 0421 + 040P06 - An active spiral (?) galaxy with extended radio lobes

The infrared bright galaxy 0421 + 040P06 detected by IRAS at 25 and 60 microns was studied at optical, infrared, and radio wavelength. It is a luminous galaxy with apparent spiral structure emitting 4 x 10 to the 37th power from far-infrared to optical wavelengths. Optical spectroscopy reveals a Seyfert 2 emission line spectrum, making 0421 + 040P06 the first active galaxy selected from an unbiased infrared survey of galaxies. The fact that this galaxy shows a flatter energy distribution with more 25 micron emission than other galaxies in the infrared sample may be related to the presence of an intense active nucleus. The radio observations reveal the presence of a non-thermal source that, at 6 cm, shows a prominent double lobed structure 20 to 30 kpc in size extending beyond the optical confines of the galaxy. The radio source is three to ten times larger than structures previously seen in spiral galaxies.

Beichman, C.↗

NASA NTRS1985

Multiaperture infrared photometry of the nuclei of spiral galaxies

Results of a multiaperture, 2.2- and 10-micron photometric survey of the nuclei of 25 nearby, low-inclination spiral galaxies are presented. The 10-micron nuclear luminosities, attributed to thermal reradiation by dust in regions of active star formation, and 10-micron/2.2-micron nuclear flux ratios, are examined as a function of the slope of 2.2-micron growth curve. No correlation is seen, suggesting that the contribution of young, red giants and supergiants to the near-infrared light of spiral nuclei is small. These results indicate that the 2.2-micron light of galaxies in the present sample is not radically altered by starbursts.

Cizdziel, P. J.↗

NASA NTRS1984

Extreme Limb Profiles of the Sun at Far Infrared and Submillimeter Wavelengths

Limb intensity profiles at 30, 50, 100, and 200 microns, determined from Kuiper airborne observatory (KAO) observations of the occultation of the solar limb during the total eclipse of July 31, 1981, are presented. Significant but gradual limb brightening was found at the longer wavelengths consistent with the 6000 K temperature-plateau structure of the model chromospheres of Vernazza, Avrett, and Loeser. The 100 and 200 micrometers limbs are extended significantly further above the visible limb than the Vernazza, Avrett, and Loeser model predicts. These results show that the solar chromosphere is strongly perturbed from gravitational-hydrostatic equilibrium to heights as low as 1000 km. These profiles can serve as a powerful diagnostic for modeling the temperature and density of chromospheric structure free from the assumption of gravitational-hydrostatic equilibrium.

Becklin, E. E.↗

NASA NTRS1984

Far Infrared Continuum Emission from the Galactic Center

High angular resolution observations of the Galactic center from the Kuiper Airborne Observatory are discussed. The results of multi-wavelength mapping reveal that the 30 micron distribution shows a single peak which lies between two emission lobes seen at the longer wavelengths. The 30 micron emission is known from ground-based measurements to peak at the galactic center. The far-infrared color temperature and luminosity also peak at the position of the galactic center, and the observations show a strong temperature gradient away from the galactic center in all directions. Consideration of these data leads to the conclusion that the dust density decreases inward over the central 3 pc of the Galaxy, and that the central parsec of the Galaxy is remarkably devoid of dust, so that optical and ultraviolet photons may traverse it freely. The inferred total luminosity of the sources that heat the dust radiating the far-infrared emission from the central few pc of the Galaxy is 1 to 3 x to the 7th power L(Sun). It is probable that these same sources are responsible for ionizing the plasma at the galactic center.

Werner, M. W.↗

NASA NTRS1984

Infrared observations of the eclipse of Epsilon Aurigae Direct measurement of the 500 K secondary at 5, 10, and 20 microns

Photometric data of the once-every-27 yr eclipse of the Epsilon Auriga F supergiant are reported. The data were taken on 28 nights from July 1982-May 1984 and covered the 1.25-20 microns region. The secondary object was identified at 5, 10, and 20 microns when the eclipse removed 48 percent of the F star's light. The data indicated that the secondary is a compact object surrounded by a large optically thick cloud, with a luminosity under 0.01 of the primary. The secondary's mass is, however, more than 14 solar masses.

Backman, D. E.↗

NASA NTRS1984

The IRAS galaxy 0421+040P06: An active spiral (?) galaxy with extended radio lobes

The infrared bright galaxy 0421+040P06 detected by IRAS at 25 and 60 microns was studied at optical, infrared, and radio wavelength. It is a luminous galaxy with apparent spiral structure emitting 4 x 10 to the 37th power from far-infrared to optical wavelengths. Optical spectroscopy reveals a Seyfert 2 emission line spectrum, making 0421+040P06 the first active galaxy selected from an unbiased infrared survey of galaxies. The fact that this galaxy shows a flatter energy distribution with more 25 micron emission than other galaxies in the infrared sample may be related to the presence of an intense active nucleus. The radio observations reveal the presence of a non-thermal source that, at 6 cm, shows a prominent double lobed structure 20 to 30 kpc in size extending beyond the optical confines of the galaxy. The radio source is three to ten times larger than structures previously seen in spiral galaxies.

Beichman, C. A.↗

NASA NTRS1984

A luminous 3 kiloparsec infrared disk in NGC 1068

A 10 micron map of the Seyfert galaxy NGC 1068 and airborne measurements of its angular extent in the far-infrared are presented. It is shown that the infrared emission originates primarily from two physically distinct regions; approximately half of the total infrared luminosity of 3 x 10 to the 11th solar luminosities is associated with the Seyfert nucleus and half with a 3 kpc (35 arc sec) diameter disk surrounding it. It is argued that the disk component of infrared emission originates from an extended but heavily obscured burst of star formation which resembles those seen in some non-Seyfert galaxies. This high-luminosity disk is distinguished more by its large size than by its high surface brightness. On the basis of current evidence it cannot be concluded that the high disk luminosity in NGC 1068 is causally related to its Seyfert activity.

Telesco, C. M.↗

NASA NTRS1984

Observations of the brightness profile of the sun in the 30-200 micron continuum

The brightness profile of the quiet sun in broad continuum passbands centered at 30, 50, 100, and 200 microns was observed with a resolution of 2 arcmin. Weak radial darkening was seen at all four wavelengths near disk center. This reverses to brightening toward the limb in the 100 and 200 micron continuum. Radial darkening at 100 and 200 microns is not expected from smooth model chromospheres consistent with absolute brightness measurements. These results do not support a homogeneous model of the low chromosphere, where the temperature reversal occurs.

Lindsey, C.↗