Absolute magnitudes for late-type dwarf stars for Sloan photometry
We present a new formula for absolute magnitude determination forlate-type dwarf stars as a function of (g-r) and (r-i) for Sloanphotometry. The absolute magnitudes estimated by this approach arebrighter than those estimated by colour-magnitude diagrams, and theyreduce the luminosity function rather close to the luminosity functionof Hipparcos.
|
UBVRI photopolarimetry of the long-period eclipsing AM Herculis binary V1309 Ori
We report simultaneous UBVRI photopolarimetric observations of thelong-period (7.98 h) AM Her binary V1309 Ori. The length and shape ofthe eclipse ingress and egress vary from night to night. We suggest thatthis is a result of the variation in the brightness of the accretionstream. By comparing the phases of circular polarization zero-crossoverswith previous observations, we confirm that V1309 Ori is wellsynchronized, and find an upper limit of 0.002 per cent for thedifference between the spin and orbital periods. We model thepolarimetry data using a model consisting of two cyclotron emissionregions at almost diametrically opposite locations, and centred atcolatitude β= 35° and 145° on the surface of the whitedwarf. We also present archive X-ray observations which show that thenegatively polarized accretion region is X-ray bright.
|
The u'g'r'i'z' Standard-Star System
We present the 158 standard stars that define the u'g'r'i'z' photometricsystem. These stars form the basis for the photometric calibration ofthe Sloan Digital Sky Survey. The defining instrument system andfilters, the observing process, the reduction techniques, and thesoftware used to create the stellar network are all described. Webriefly discuss the history of the star selection process, thederivation of a set of transformation equations for theUBVRCIC system, and plans for future work.
|
The B jRI Photometric System
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..281G&db_key=AST
|
Dust and extinction in the planetary nebula NGC 7027
High spatial resolution (not more than 1.0 arcsec/pixel) optical andnear-IR images of NGC 7027 obtained to investigate the overall dustdistribution and small-scale (about 1-2 arcsec) extinction variation ispresented. Analysis of the derived near-IR color excess suggests thatthe variation of line-of-sight visual extinction across the face of NGC7027 ranges from about 1 to 8 mag. Although the observed nebular size atnear-IR wavelengths is comparable to that determined at radiofrequencies, indicating that the dust and ionized gas are partiallycomixed in the H II region, the dust component primarily responsible forthe extinction likely resides in a shell, or possibly a disk, outsidethe volume containing the dust emitting the near-IR thermal continuum.
|
UBVRI photometric standard stars in the magnitude range 11.5-16.0 around the celestial equator
UBVRI photoelectric observations have been made on theJohnson-Kron-Cousins photometric system of 526 stars centered on thecelestial equator. The program stars within a 298 number subset havesufficient measures so that they are capable of providing, fortelescopes of intermediate and large size in both hemispheres, aninternally consistent homogeneous broadband standard photometric systemaround the sky. The stars average 29 measures each on 19 nights. Themajority of the stars in this paper fall in the magnitude range11.5-16.0, and in the color range -0.3 to +2.3.
|
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.
|
The 77-81 intermediate-band photometric system
The 77-81 intermediate-band photometric color system for the study oflate-type stars is defined. The passbands are centered on a region ofTiO absorption at 7750 A (77) and on a region of CN absorption at 8100 A(81). Good agreement is found between measurements made on the 77-81system with different detectors. The 77-81 color is well correlated withM type and reasonably correlated with carbon-richness class. The 77-81,V-I color-color diagram clearly distinguishes M and C types from otherstars. It is also shown that the 77-81 color may be used to measure TiOband strength.
|
Photoelectric observations of classical cepheids.
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.
|
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
|
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.
|
