Spectral Irradiance Calibration in the Infrared. XIV. The Absolute Calibration of 2MASS
Element by element, we have combined the optical components in the threecameras of the Two Micron All Sky Survey (2MASS), and incorporateddetector quantum efficiency curves and site-specific atmospherictransmissions, to create three relative spectral response curves (RSRs).We provide the absolute 2MASS attributes associated with ``zeromagnitude'' in the JHKs bands so that these RSRs may be usedfor synthetic photometry. The RSRs tie 2MASS to the``Cohen-Walker-Witteborn'' framework of absolute photometry and stellarspectra for the purpose of using 2MASS data to support the developmentof absolute calibrators for the Infrared Array Camera and pairwisecross-calibrators between all three SIRTF instruments. We examine therobustness of these RSRs to changes in water vapor within a night. Wecompare the observed 2MASS magnitudes of 33 stars (converted from theprecision optical calibrators of Landolt and Carter-Meadows intoabsolute infrared calibrators from 1.2 to 35 μm) with ourpredictions, thereby deriving 2MASS ``zero-point offsets'' from theensemble. These offsets are the final ingredients essential to merge2MASS JHKs data with our other absolutely calibrated bandsand stellar spectra, and to support the creation of faint calibrationstars for SIRTF.
|
Spectral Irradiance Calibration in the Infrared. XIII. ``Supertemplates'' and On-Orbit Calibrators for the SIRTF Infrared Array Camera
We describe the technique that will be used to develop a set of on-orbitcalibrators for the Infrared Array Camera (IRAC) and demonstrate thevalidity of the method for stars with spectral types either K0-M0 III orA0-A5 V. For application to SIRTF, the approach is intended to operatewith all available optical, near-infrared (NIR), and mid-infrared (MIR)photometry and to yield complete absolute spectra from UV to MIR. Oneset of stars is picked from Landolt's extensive network of optical(UBVRI) calibrators, the other from the Carter-Meadows set of faint IRstandards. Traceability to the ``Cohen-Walker-Witteborn'' framework ofabsolute photometry and stellar spectra is assured. The method is basedon the use of either ``supertemplates,'' which represent the intrinsicshapes of the spectra of K0-M0 III stars from far-UV (1150 Å) toMIR (35 μm) wavelengths, or Kurucz synthetic spectra for A0-A5 Vstars. Each supertemplate or Kurucz model is reddened according to theindividual star's extinction and is normalized using availablecharacterized optical photometry. This paper tests our capability topredict NIR (JHK) magnitudes using supertemplates or models constrainedby Hipparcos/Tycho or precision ground-based optical data. We provideabsolutely calibrated 0.275-35.00 μm spectra of 33 Landolt andCarter-Meadows optical standard stars to demonstrate the viability ofthis technique, and to offer a set of IR calibrators 100-1000 timesfainter than those we have previously published. As an indication ofwhat we can expect for actual IRAC calibration stars, we have calculatedthe absolute uncertainties associated with predicting the IRACmagnitudes for the faintest cool giant and hot dwarf in this new set ofcalibration stars.
|
Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
|
The B jRI Photometric System
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..281G&db_key=AST
|
Photometry of Stars in the Field of V345 and V553 Aquilae
Not Available
|
Photometry of Stars in the Field of Nova Cassiopeiae 1993
Not Available
|
Photometry of Stars in the Field of the Dwarf Nova KU Cassiopeiae
Not Available
|
Photometry of Stars in the Field of WZ Cassiopeiae
Not Available
|
Photometry of Stars in the Field of the Mira XY Aquilae
Not Available
|
Photometry of Stars in the Field of the Mira YZ Draconis
Not Available
|
Photometry of Stars in the Field of AV Cygni and DV Cygni
Not Available
|
On the sytematic accuracy of the equatorial UBVRI standard stars
The considerable systematic difference in B-V between northern andsouthern measurements of the equatorial UBVRI standard stars arestudied. It is found that the northern data (Landolt 1983) are muchcloser to the original UBV system than the southern ones. The situationis less clear in the case of V and U-B.
|
Photometry of Stars in the Field of the Mira V418 Cassiopeiae
Not Available
|
Fifth fundamental catalogue. Part 2: The FK5 extension - new fundamental stars
The mean positions and proper motions for 3117 new fundamental starsessentially in the magnitude range about 4.5 to 9.5 are given in thisFK5 extension. Mean apparent visual magnitude is 7.2 and is on average2.5 magnitudes fainter then the basic FK5 which has a mean magnitude of4.7. (The basic FK5 gives the mean positions and proper motions for theclassical 1535 fundamental stars). The following are discussed: theobservational material, reduction of observations, star selection, andthe system for the FK5 extension. An explanation and description of thecatalog are given. The catalog of 3117 fundamental stars for the equinoxand epoch J2000.0 and B1950.0 is presented. The parallaxes and radialvelocities for 22 extension stars with large forecasting effects aregiven. Catalogs used in the compilation of the FK5 fundamental catalogare listed.
|
UBV(RI)c photometry of equatorial standard stars - A direct comparison between the northern and southern systems
UBV(RI)c photometry of 212 stars from Landolt's list of equatorialstandards is presented. The observations are tied to the system definedby Cousin's E-region standards. A comparison of the present results withLandolt's reveals reasonably good agreement for (V-R)c and (V-I)c, butmarked systematic differences for (B-V) and (U-B). The UBV systems ofCousins and Landolt are evidently not the same and both probably differfrom Johnson's original system.
|
UBV Photometry of Equatorial Stars
Not Available
|
UBVRI photometric standard stars around the celestial equator
It is pointed out that accurate, internally consistent, and readilyaccessible standard star photometric sequences are necessary for thecalibration of the intensity and color data which astronomers obtain atthe telescope. The photometric results provided in connection with thepresent study represent the first part of an effort which is concernedwith the presentation of UBVRI photoelectric photometric standard starsin the magnitude range from 7 to 17 over as broad a range in color aspossible. All of the photometric observations were made with a 31034type photomultiplier used in a pulse counting mode. Some 15 to 25standard stars chosen from Cousins' lists (1973, 1976) in the E-regionswere observed with an 0.4-m telescope each night along with the programstars. UBVRI standard stars were observed periodically throughout thenight. Observations with a 0.9-m telescope were also conducted. TheUBVRI photoelectric observations take into account 223 stars.
|
Distances to eclipsing binaries. III - Masses, radii, and absolute magnitudes of 96 stars
Distances to, and absolute magnitudes of, 96 components of eclipsingbinaries with well-determined absolute dimensions have been computedusing V-R photometry. The calculations take into account interstellarreddening, which is estimated from existing UBV and uvby-betaphotometry, as well as photometric proximity effects. The resultingabsolute magnitudes, dimensions, and masses are compared with zero-agemain sequences predicted by theory. Theory is in good agreement with theobserved data for stars more massive than the sun if a composition (X,Y, Z) = (0.66 + or - 0.03, 0.303 + or - 0.03, 0.037 + or - 0.005) ischosen. The corresponding helium-to-hydrogen number ratio is 0.115 + or- 0.02, in agreement with previous estimates.
|
Spectral classifications for Landolt's celestial equatorial standard stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979AJ.....84..783D&db_key=AST
|
A set of faint equatorial standard stars for BVRI photometry
BVRI photoelectric photometry is presented for 48 of Landolt's (1973)faint equatorial standard stars. The 48 stars, which have spectral typesfrom A to K and V magnitudes in the range from 8.0 to 12.0, are chosento provide two blue and two red stars in each of 12 of the equatorialselected areas studied by Landolt. The program stars were observed withan S-1 photomultiplier, with the B-V, V-R, and V-I colors transformed tothe Johnson system; they were also observed with an RCA 31034Aphotomultiplier, with the resulting V-R and V-I colors given on azero-point-adjusted instrumental system. Observations of several Mdwarfs with the two photomultipliers are also reported. Serious problemsencountered in transforming the observed V-R and V-I colors of the Mdwarfs to the Johnson system are discussed.
|
Equatorial UBVRI photoelectric sequences
From 1335 BVRI observations of 189 stars in selected areas 92-115,Landolt's (1973) network of faint UBV standards has been extended to RI. Of these stars, 173 have four or more observations. The (U-B) valuesof Landolt are adopted, and a well-observed equatorial faint-starnetwork is presented on the Johnson UBVRI photometric system.
|
INHABITED SKY
