Infrared photometry of the RS CVn binary HR 1099 (V711 Tau)

Infrared observations inJ, H andK of the RS CVn-type binary HR 1099 (V711 Tau) show apparent light variations similar to those in the visible. The phase shift towards increasing phase is confirmed. There is no conspicuous infrared excess attributable to circumstellar emission. The amplitudes of the infrared variation are compatible with the spot model proposed for RS CVn and enable plausible limits on a characteristic spot temperature and effective spot area to the set.     

B,V photometry of the active RS CVn system II Peg

In this work,B andV photometry of the RS CVn-type binary II Peg is presented. The light curves obtained in 1983 and 1984 display two unequal maxima. The light curves of the system have different amplitudes. The amplitude seems to vary with three different periods. 10, 6, and 4 years of periods may be attributed to those variations.     

Precision IR and visible solar photometry

A precision Solar Photometric Telescope (SPT) was constructed to study the large-scale thermal structure of the solar photosphere. This instrument does full-disk, broad-band (10 nm FWHM), two-color (500 and 650 nm) imaging of the solar photosphere. Data obtained by the SPT reveals network structures correlated with the supergranulation velocity field, and the CaK network of the chromosphere. Infrared array photometry extends these measurements to 1.6 and 2.2 micron. The observed correlation of the network brightness signal with the CaK network is positive at visible wavelengths. The correlation between the network at the opacity minimum (1.6 micron) and in the higher photosphere (2.2 micron) is positive also. The root-mean-square (r.m.s.) amplitude of the contrast at disk center is (2.34 ± 0.38) × 10^-3, (1.83 ± 0.51) × 10^-3, (1.02 ± 0.21) × 10^-3, and (1.11 ± 0.21) × 10^-3 for the green, red, H, and K band, respectively. It is consistent with a brightness temperature modulation of 2.9 K. The r.m.s. amplitude of the contrast of active region network shows a large increase toward the limb, and the quiet region network shows little center-to-limb variation (CLV). Power-spectrum analysis shows that the bright facular points in the active regions appear in the form of enhanced network.     

Infrared photometry of AGB stars

The goal of this article is to show that, if one avoids star forming regions, mass-losing AGB stars can generally be selected from the data that will be provided by the near-infrared surveys which are presently considered. Also, if IRAS data are available, the separation between carbon-rich and oxygen-rich stars can be operated by their positions in infrared colour diagrams. In extragalactic systems, red supergiants can be discriminated from AGB stars by their luminosities.based on observations obtained with the ESO 1-m telescope     

Infrared photometry of Comet Kohoutek

Before perihelion, the 8.8–21 μm luminosity of Comet Kahoutek (1973f) was on the order of 10²¹ ergsec^?1 and dropped to 10²⁰ ergsec^?1 after perihelion.     

Infrared photometry and spectrophotometry of Comet Halley

We report on our photometric and spectrophotmetric measurement of Comet Halley in near infrared. The observations confirmed the explosion found in the preceding article and showed the post-explosion behaviour of the comet was different in the visible and the infrared. Water emission lines at 1.4 cm and 1.9 cm were found.     

Infrared photometry of five long-period binaries

We present and discuss JHKLM photometry for five long-period binaries (VV Cep, ZZ CMi, WY Gem, ε Aur, and ζ Aur). The IR radiation from WY Gem may contain a component with a period of ～430 days, attributable to temperature pulsations of an M supergiant. The 3.5-and 5-μm radiation from the eclipsing binary ε Aur outside the eclipse exhibits excess (relative to the light from an F supergiant) fluxes which correspond to the emission from a cool source with a temperature of ～1000 K. For the eclipsing binary Aur, we present the hitherto unpublished results of our optical and IR photometry during 1982–1985, when a primary eclipse was observed in the system.     

Infrared photometry of solar active regions

Simultaneous time series of broad-band images of two active regions close to the disk center were acquired at the maximum (0.80Μm) and minimum (1.55Μm) continuum opacities. Dark faculae are detected in images obtained as weighted intensity differences between both wave-length bands. The elements of quiet regions can be clearly distinguished from those of faculae and pores in scatter plots of brightness temperatures. There is a smooth transition between faculae and pores in the scatter plots. These facts are interpreted in terms of the balance between the inhibition of convective energy transport and the lateral radiative heating.     

Infrared photometry of eight planetary nebulae

We discuss the infrared (IR) (1.25–5 µm) photometry of eight planetary nebulae performed in 1999–2006. For all of the nebulae under study, we have firmly established IR brightness and color variations on time scales shorter than one year and up to 6–8 years. The greatest IR brightness variations were observed in IC 2149, IC 4997, and NGC 7662. Their J magnitudes varied within 0 _. ^m 2–0 _. ^m 25. In the remaining objects, the J magnitude variations did not exceed 0 _. ^m 15. All of the planetary nebulae under study exhibited IR color variations. Based on the IR photometry, we have classified the central regions of the planetary nebula NGC 1514 and of the northern part of NGC 7635 seen through a 12″ aperture as a B(3–7) main-sequence star (NGC 1514) and a ～O9.5 upper-main-sequence star (NGC 7635). The nebulae IC 4997 and NGC 7027 exhibited an excess emission (with respect to the emission from a hot source) at λ > 2.5 µm.     

Physical survey of 24 Centaurs with visible photometry

We present optical observations of 24 Centaurs performed between 1998 and 2002 with the University of Hawaii 2.2-m telescope. This is the largest such Centaur survey to date. We report colors for all objects, and show that they cover a continuum with mean V–R color of 0.58±0.01 and standard deviation 0.15. The color distribution fits between those of the Kuiper Belt and the cometary nuclei, and seems consistent with the dynamical concept of the majority of Centaurs originating from the Kuiper Belt. We find no strong correlation between a Centaur's color and its orbital elements; there is at best a <3−σ correlation with semimajor axis, with redder Centaurs being farther from the Sun. We have calculated the phase-darkening slope parameters G for 5 Centaurs, 4 of which are reported for the first time. They range from −0.18 to 0.13. We have sufficient data to constrain the rotation periods of two Centaurs, 1999 UG₅ (which we reported earlier) and 1998 SG₃5. We performed a comparison of the surface brightness profiles of 10 apparently-inactive Centaurs with point sources. We found no coma around these 10 objects, including C/LINEAR (2000 B4), and generally the upper limits to the dust mass loss rates are below 0.05 kg s⁻¹.     

Near infrared photometry of some RS CVn systems and candidates

Infrared observations in the J, H, and K bands were made on eleven RS CVn systems. Infrared (IR) excess 0.3 mag in the J, H, and K bands was observed from the three systems UX Ari, HR 1099 and CrB. Similar observations were also made on the RS CVn candidates HD 26354, 39937, 42449, 51268, and 86005.The IR excess in the RS CVn systems for which near infrared photometric data are available is found to be correlated with the maximum of optical wave amplitude of these systems.The observed excess cannot be explained on the basis of a single process such as: (i) emission from cool spots on the photosphere; (ii) free-free emission from an optically thin circumstellar plasma; or (iii) dust grain emission from circumstellar material.On leave from TIFR, Bombay, India.     

Infrared photometry of low-mass stars in Praesepe

We present follow-up infrared photometry for a sample of low-mass and very low-mass stars in the Praesepe open cluster. Our sample is selected from two sources: (i) 90 stars selected from the Hambly et al. photometric and proper-motion survey of Praesepe; (ii) 17 stars selected from the CCD imaging survey presented by Pinfield et al. We investigate cluster membership using infrared colour–magnitude and colour–colour diagrams. We find 81 likely and two possible members in the Hambly et al. sample, in line with predictions. Contamination in the Pinfield et al. sample is higher, and we find nine probable cluster members. We investigate the non-grey models of Baraffe et al., which are found to be in good agreement with the data. Multiplicity in Praesepe is also examined, and we find the multiple star fraction to be 0.51 from analysis of the I , I − K diagram. We investigate individual object masses, and find that the faintest candidate cluster members have masses close to the substellar limit.     

Infrared photometry of a sunspot near the disk center

A time series of broadband images of a sunspot near the disk center was obtained simultaneously in two wavelength bands at 0.56 μm and 1.55 μm at the German VTT on June 17, 1998. We computed intensity difference images of the best frame pairs which reveal information about the facular distribution in the present field of view. Faculae are found around pores, in the quiet granulation and as well around the sunspot penumbra.     

Infrared photometry of comets Bowell and P/Stephan-Oterma

We report broadband infrared photometry of comets P/Stephan-Oterma and Bowell between 1 and 20 μm. Their JHK colors are similar to P/Meier and P/Tuttle and are compatible with scattering of sunlight by micron-sized grains. The thermal emission from P/Stephan-Oterma showed an effective temperature significantly higher than that expected from a blackbody in equilibrium. The thermal emission can be models be fit by models of the dust coma consisting of micron-sized grains. Most of the flux at all observed wavelengths comes from the dust grains rather than form the nucleus.     

Photoelectric photometry of the RS CVn binary EI Eridani = HD 26337

DifferentialUBV(RI) _KC andUBVRI photometry of the RS CVn binary EI Eridani obtained during December 1987 and January 1988 at fourteen different observatories is presented. A combined visual bandpass light curve, corrected for systematic errors of different observatories, utilizes the photometric period of 1.945 days to produce useful results. Analysis shows the visual light curve to have twin maxima, separated by about 0.4 phase, and a full amplitude of approximately 0.06 mag for the period of observation, a smaller amplitude than reported in the past. The decrease in amplitude may be due to a decrease or homogenization of spot coverage. To fit the asymmetrical light curve, a starspot model would have to employ at least two spotted regions separated in longitude.     

RS CVn型密近双星系统的红外辐射

本文给出了41个RS CVn型密近双星系统的J,H和K的测光结果和经证认为IRAS点源的40个Rs CVn系统的数据。对那些子星具有光谱分类的系统,我们讨论了它们的红外色余,发现只有少数系统具有红外色余。在近红外区有UX Ari,Z Her和HR 1099;在12μm处为SZ Psc。对那些具有确切的12、25μm流量并作了K星等测量的系统,我们讨论了他们在logf_(2.2)/f_(12)和logf_(25)/f_(12)的双色图上的位置。大多数RS CVn系统都在黑体线的附近。这一些结论却和P.Biermann和D.Hall所指出的红外色余是RS CVn型密近双星的一般特性所不相符合。对一些红外辐射有差异的天体应进一步研究。     

Infrared radiation oF RS CVn systems

We give the results of our J, H, K photometry on 41 RS CVn systems and the data on 40 RS CVn systems identified with IRAS point sources. For those systems in which the components have individual spectral types, we discuss their infrared color excess. We found only very few systems showed infrared excesses. (UX Ari, Z Her and HR 1099 in the near infrared and SZ Psz at 12μm).

For systems having fluxes at 12 and 25μm and K magnitudes, we plotted a color-color diagram and found the majority of points to be lying close to the black body line. These observations are in conflict with Biermann and Hall's statement [1] that infrared excess is a general characteristic of RS CVn systems.