H-band Data Research Articles

Near-infrared polarimetric study of the bipolar nebula IRAS 19312+1950

Aims. We have investigated the properties of the central star and dust in the bipolar nebula IRAS 19312+1950, which is an unusual object showing the characteristics of a supergiant, a young stellar object, and an asymptotic giant branch (AGB) star. Methods. We obtained H-band polarimetric data of IRAS 19312+1950 using the near-infrared camera (CIAO) on the 8 m Subaru telescope. In order to investigate the physical properties of the central star and the nebula, we performed radiative transfer modeling and compared the model results with the observed spectral energy distributions (SEDs), the radial profiles of the total intensity image, and the fraction of linear polarization map. Results. The total intensity image shows a nearly spherical core with ∼3 �� radius, an S-shaped arm extending ∼10 �� in the northwest to southeast direction, and an extended lobe towards the southwest. The polarization map shows a centro-symmetric vector alignment in almost the entire nebula and low polarizations along the S-shaped arm. These results suggest that the nebula is accompanied by a central star, and the S-shaped arm has a physically ring-like structure. From our radiative transfer modeling, we estimated the stellar

ESO imaging survey: infrared observations of CDF-S and HDF-S

This paper presents infrared data obtained from observations carried out at the ESO 3.5m New Technology Telescope (NTT) of the Hubble Deep Field South (HDF-S) and the Chandra Deep Field South (CDF-S). These data were taken as part of the ESO Imaging Survey (EIS) program, a public survey conducted by ESO to promote follow-up observations with the VLT. In the HDF-S field the infrared observations cover an area of ~53 square arcmin, encompassing the HST WFPC2 and STIS fields, in the JHKs passbands. The seeing measured in the final stacked images ranges from 0.79 to 1.22 and the median limiting magnitudes (AB system, 2 aperture, 5sigma detection limit) are J_AB~23.0, H_AB~22.8 and K_AB~23.0 mag. Less complete data are also available in JKs for the adjacent HST NICMOS field. For CDF-S, the infrared observations cover a total area of \~100 square arcmin, reaching median limiting magnitudes (as defined above) of J_AB~23.6 and K_AB~22.7 mag. For one CDF-S field H-band data are also available. This paper describes the observations and presents the results of new reductions carried out entirely through the un-supervised, high-throughput EIS Data Reduction System and its associated EIS/MVM C++-based image processing library developed, over the past 5 years, by the EIS project and now publicly available. The paper also presents source catalogs extracted from the final co-added images which are used to evaluate the scientific quality of the survey products, and hence the performance of the software. This is done comparing the results obtained in the present work with those obtained by other authors from independent data and/or reductions carried out with different software packages and techniques. The final science-grade catalogs and co-added images are available at CDS.

Milliarcsecond-resolution observations of IRC +10216

We analyze two lunar occultation lightcurves of the carbon star IRC +10216 ( CW Leo). The two events were recorded in 1989 and 1998, in the near-infrared H and K bands respectively. The results consist of two extended (≈2″), high-resolution (≈0″.001), one-dimensional brightness profiles along position angles 164° and 304° at the two epochs. The profiles show evidence for a bright central spike of emission having a FWHM of 0″.035, which is consistent with what is predicted by current models for the photosphere of the central star in IRC +10216. This feature can be identified with the so-called A component recently revealed by speckle imaging [A&A 334 (1998) L5; A&A 357 (2000) 169; A&A 333 (1998) L51], and the so-called core of the southern component observed with the aperture masking technique by Tuthill et al. [ApJ 543 (2000) 284]. The B component, alternatively suggested to mark the actual location of the central star by Osterbart et al. [A&A 357 (2000) 169], also seems to show a FWHM consistent with the above value, but it is well detected only in the 1998 K-band lightcurve, while for the 1989 H-band data the detection is less evident. Our brightness profiles also reveal a wealth of other structures, on several levels of scale, which are consistent with models of episodic dust ejection from the central star [A&A 302 (1995) 483].

Keck Diffraction‐limited Imaging of the Young Quadruple Star System HD 98800

This paper presents diffraction-limited 1-18 μm images of the young quadruple star system HD 98800 obtained with the W. M. Keck 10 m telescopes using speckle and adaptive optics imaging at near-infrared wavelengths and direct imaging at mid-infrared wavelengths. The two components of the visual binary, A and B, both themselves spectroscopic binaries, were separable at all wavelengths, allowing us to determine their stellar and circumstellar properties. Combining these observations with spectroscopic data from the literature, we derive an age of ~107 yr, masses of 0.93 and 0.64 M☉, and an inclination angle of 58° for the spectroscopic components of HD 98800 B and an age of ~107 yr and a mass of 1.1 M☉ for HD 98800 Aa. Our data confirm that the large mid-infrared excess is entirely associated with HD 98800 B. This excess exhibits a blackbody temperature of 150 K and a strong 10 μm silicate emission feature. The theoretical equilibrium radius of large, perfectly absorbing, 150 K grains around HD 98800 B is 2.4 AU, suggesting a circumspectroscopic binary distribution. Our observations set important upper limits on the size of the inner dust radius of ~2 AU (from the mid-infrared data) and on the quantity of scattered light of less than 10% (from the H-band data). For an inner radius of 2 AU, the dust distribution must have a height of at least 1 AU to account for the fractional dust luminosity of ~20% LB. Based on the scattered-light limit, the dust grains responsible for the excess emission must have an albedo of less than 0.33. The presence of the prominent silicate emission feature at 10 μm implies dust grain radii of 2 μm. The total mass of the dust is greater than 0.002 M⊕. We conclude that the dust is located in a circumbinary disk around the HD 98800 B spectroscopic binary with an inner gap of ~2 AU and a height of 1 AU, and we speculate that the A-Bc orbital dynamics are responsible for the characteristics of the observed dust in the system.

YOHKOH/HXT Evidence for a Hyperhot Loop-Top Source in The Pre-Impulsive Phase of a Loop Flare

A loop flare that occurred on 22 April 1993 near the disk center is examined using the Yohkoh Hard X-ray Telescope (HXT). We specifically looked into the faint early phase of the flare prior to the start of the strong impulsive phase. The pre-impulsive phase, though weak in intensity, is expected to contain essential clues to the mechanism of loop flares according to the causality principle, but it has not received attention previously, probably due to the insufficient dynamic range and cadence of observations by the instruments on earlier satellites. Observations with Yohkoh/HXT can clarify what occurs in this phase. This flare, like many other flares of this type, shows a relatively weak emission with a smooth and gradual increase during this pre-impulsive phase, followed by impulsive bursts, and then turns into a smooth decay phase without impulsive bursts. First, we found that the spectrum for the initial smooth rise part is consistent with a thin-thermal source at a temperature around 80 MK. Imaging of this phase in the HXT/L and M bands shows a single source between the footpoint sources that will come up in the impulsive phase following this phase, suggesting that this hyperhot source is located at a high part of the loop between the footpoints, since this flare takes a form of a loop. Furthermore, as we go up to the earliest times of the flare before this `hyperhot' source phase, two fainter sources are found near the footpoint sources that will appear later in the impulsive phase. The spectra of these sources at this earliest time of the flare, in contrast to the `hyperhot' source, cannot be determined from the HXT because the instrument was not in flare mode, and HXT/M1, M2, and H-band data are, unfortunately, not available at this very initial time. We can guess, however, that they are also of thermal character because the time profile is smooth without any spikes just as in the following `hyperhot' thermal phase, and in the post-impulsive `superhot' thermal phase coming up much later. These findings suggest that there is an important, and probably dynamic, early phase in loop flares that has been unnoticed in the still dark pre-impulsive phase, because the very early footpoint sources change into the loop top source in a matter of 20–30 s, comparable to the dynamic Alfven time scale. Some implications of our new findings are discussed.

TheHubble Space TelescopeKey Project on the Extragalactic Distance Scale. XXIV. The Calibration of Tully‐Fisher Relations and the Value of the Hubble Constant

This paper presents the calibration of BVRIH-0.5 Tully-Fisher relations based on Cepheid distances to 21 galaxies within 25 Mpc and 23 clusters within 10,000 km s-1. These relations have been applied to several distant cluster surveys in order to derive a value for the Hubble constant, H0, mainly concentrating on an I-band all-sky survey by Giovanelli and collaborators, consisting of total I magnitudes and 50% line width data for ~550 galaxies in 16 clusters. For comparison, we also derive the values of H0 using surveys in the B and V bands by Bothun and collaborators, and in H band by Aaronson and collaborators. Careful comparisons with various other databases from the literature suggest that the H-band data, which have isophotal magnitudes extrapolated from aperture magnitudes rather than total magnitudes, are subject to systematic uncertainties. Taking a weighted average of the estimates of Hubble constants from four surveys, we obtain H0 = 71 ± 4 (random) ± 7 (systematic). We have also investigated how the value of H0 is affected by various systematic uncertainties, such as the internal extinction correction method used, Tully-Fisher slopes and shapes, a possible metallicity dependence of the Cepheid period-luminosity relation, and cluster population incompleteness bias.

IR Observations of the K and F Corona During the 1991 Eclipse

The availability of relatively large format IR array detectors is incentive for reexamining the classic question of whether or not there are “dust rings” around the sun – a problem for which there are conflicting observational answers. The 1991 eclipse path included a high altitude observatory and provided a potentially ideal opportunity to study the infrared properties and dust content of the corona. Here we report results from an experiment conducted from Mauna Kea using a HgCdTe array detector sensitive to wavelengths between 1-2.5 μm. Surface brightness measurements in the H-band and polarization data in the J-band were obtained over a field-of-view of ±6 R⊙ while K-band images further extend to 15 R⊙ on the western side of the Sun. J-band polarization data and H and K-band surface brightness data clearly show the inhomogeneous structure in the K corona and the ecliptical flattening of the F corona. We see no evidence of a circumsolar, local dust corona (dust rings) out to 15 R⊙.

The 21 centimeter line width as an extragalactic distance indicator. III - The correction for velocity dispersion and the B- and H-band Tully-Fisher relations

view Abstract Citations (25) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The 21 centimeter line width as an extragalactic distance indicator. III - The correction for velocity dispersion and the B- and H-band Tully-Fisher relations Bottinelli, L. ; Gouguenheim, L. ; Paturel, G. ; de Vaucouleurs, G. Abstract The curvature of the H-band Tully-Fisher relation reported by Aaronson and Mould (1983) is demonstrated to be wholly a result of neglecting the corrections for bandwidth and turbulent velocities. The application of the correction model of Bottinelli et al. (1980, 1982, 1983) eliminates the curvature and decreases the slope of the linearized H-band relation to the previously determined value of 9.7. The curvature of the H-band relation disappears when the correction for velocity dispersion derived for the B-band is applied to the H-band data. After correction for the effect of bandwidth and velocity dispersion, the slope and zero point of the H-band relation are nearly independent of type. For well observed galaxies, it is shown that the distance moduli derived from the B- and H-band relations, both corrected for line broadening, have mean errors of, respectively, 0.3 and 0.4 mag. Publication: The Astrophysical Journal Pub Date: May 1984 DOI: 10.1086/161965 Bibcode: 1984ApJ...280...34B Keywords: Astrometry; Astronomical Photometry; Centimeter Waves; Distance; Galactic Rotation; Radio Sources (Astronomy); Correction; Galactic Structure; Spectral Line Width; Turbulence; Astronomy full text sources ADS |