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Везани чланци
Improved u'g'r'i'z' to UBVRCIC Transformation Equations for Main-Sequence Stars
We report improved transformation equations between the u'g'r'i'z' andUBVRCIC photometric systems. Although the detailsof the transformations depend on luminosity class, we find a typical rmsscatter on the order of 0.001 mag if the sample is limited tomain-sequence stars. Furthermore, we find that an accuratetransformation requires complex, multicolor dependencies for the bluerbandpasses. Results for giant stars will be reported in a subsequentpaper.
| 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.
| High-Resolution Ultraviolet Observations of the Highly Ionized Interstellar Gas toward Radio Loops I and IV
We present new Goddard High-Resolution Spectrograph (GHRS) echelleobservations of the high ionization lines of Si IV, C IV, and N V towardHD 119608, a halo star at d = 4.1 kpc behind the Loop I and IV supernovaremnants. Absorption along the path to HD 119608 makes it possible tostudy energetic processes that may result in the flow of gas into theGalactic halo. The data have a resolution (FWHM) of ~3.5 km s-1 and S/Nratios of 30:1--50:1. The integrated high ion column densities log N =13.57 +/- 0.02, 14.48 +/- 0.06, and 13.45 +/- 0.07 for Si IV, C IV, andN V, respectively, imply a factor of 2--4 enhancement in the amount ofhighly ionized gas compared to average sight lines through the Galacticdisk and halo. The integrated high ion column density ratios, N(CIV)/N(Si IV) = 8.1 +/- 1.1 and N(C IV)/N(N V) = 10.7 +/- 2.1, are alsoseveral times larger than normal. These high ion results suggest theabsorption is influenced by passage of the sight line through the centerof Loop IV. The HD 119608 C IV absorption profile has a bimodal velocitystructure indicative of an expanding shell; we tentatively derive anexpansion velocity of 16 km s-1 for Radio Loop IV. A detailed analysisof the high ion profile structure indicates that multiple types ofhighly ionized gas with a range of properties exist along this sightline. We also reexamine the high ionization properties of the QSO 3C 273sight line using new intermediate-resolution (FWHM ~ 20 km s-1) GHRSdata. We obtain log N = 14.49 +/- 0.03 and 13.87 +/- 0.06 for C IV and NV, respectively. The C IV column density, which is 0.12 dex smaller thanearlier estimates, leads to somewhat smaller ionic ratios thanpreviously determined. We find N(C IV)/N(Si IV) = 5.1 +/- 0.6 and N(CIV)/N(N V) = 4.2 +/- 0.6. However, as for HD 119608, the high ion columndensities toward 3C 273 are larger than normal by factors of 2--4. The3C 273 high ion absorption profiles are much broader than those seentoward HD 119608 and other sight lines near the center of Loop IV. Thelarger line widths may result because the sight line passes through theturbulent edge of Loop IV as well as the X-ray and radio continuumemission regions of the North Polar Spur. We have compiled a list of thehighest quality IUE and GHRS high ion measurements available forinterstellar sight lines through the disk and halo and find thefollowing median averaged results: N(C IV)/N(Si IV) = 3.8 +/- 1.9 andN(C IV)/N(N V) = 4.0 +/- 2.4. These ratios are lower than those foundfor four Loop IV sight lines. We suggest a model for the production ofhighly ionized gas in Loop IV in which the contributions from turbulentmixing layers and conductive interfaces/SNR bubbles to the total highion column densities are approximately equal. Much of the high ionabsorption toward HD 119608 and 3C 273 may occur within a highlyfragmented medium within the remnant or the outer cavity walls of theremnant.
| New pulsational properties of eight `anomalous' RR Lyrae variables
CCD photometry in the V band is presented for seven field RR Lyrae starsselected from a sample of eight variables; these, according to datacollected in the literature, are expected to be ab-type pulsators, tohave short periods (and hence high metallicity), and to be located at ahigh z from the Galactic plane. New periods and epochs are derived forthem. The new periods are only slightly shorter than the valuespublished in the fourth edition of the General Catalogue of VariableStars (GCVS4). In six cases our amplitude of the light variation issignificantly smaller than that published in the GCVS4, and in at leastthree cases the actual pulsation appears to be in the first harmonicrather than in the fundamental mode. All the suggested c-type pulsatorsshow variations in the amplitude and/or quite scattered light curves.Some possible explanations are given. From a spectrophotometric analysisof the sample, only DL Com is confirmed to pulsate in the fundamentalmode, to have a short period, and to be located at a relatively high z.However, a single object cannot be taken as evidence for a significantmetal-rich population at a large distance from the Galactic plane.
| A 325 Square Degree Survey of B-Type Stars at High Galactic Latitudes
Abstract image available at:http://adsabs.harvard.edu/abs/1995ApJ...447..783L
| 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.
| Photoelectric UBV photometry of northern stars from the HK objective-prism survey. II
Photoelectric UBV photometry is presented for a sample of 165 starsdrawn from the extension of the HK objective-prism/interference-filtersurvey of Beers, Preston, and Shectman to the northern galactichemisphere. These results are part of continuing follow-up observationsof candidate metal-deficient and horizontal-branch field stars and otherinteresting stars identified in the survey. A complete set ofphotometric observations is now available for three of the25-square-degree survey fields. The complete photometric sample of 299northern HK candidates obtained to date contains on order 90main-sequence turnoff, subgiant, and giant stars with (Fe/H) of lessthan or equal to -1.0, 50 field blue horizontal-branch stars, and 30stars with the photometric properties of field-blue stragglers.
| 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.
| Photoelectric UBV photometry of northern stars from the HK objective-prism survey
Photoelectric photometry is presented for a sample of 139 halo starsdrawn from an extension of the HK objective-prism survey of Beers,Preston, and Shectman to the northern galactic hemisphere. Thecandidates for which photometry is reported were selected to span a widerange of types, but are dominated by stars classified as type AB, A, or'metal poor'.
| Broad-band photometry of selected southern ultraviolet-bright stars.
Not Available
| Four-colour and H-beta photometry of blue stars selected from a balloon-ultraviolet survey and other sources
New uvby and/or H-beta photometry is obtained at the Chiranhigh-altitude outstation for 105 stars. Certain of the program stars areselected from a comparison of the SCAP 2000 balloon-ultraviolet skysurvey of the Laboratoire d'Astronomie Spatiale with the correspondingblue and red prints of the Palomar Observatory sky survey. Only a smallportion of these stars turn out to be B stars, whereas, the rest of thestars, which are selected from a variety of other sources, are mostly Bstars and if of normal luminosity are in many cases many Population Iscale heights from the galactic plane. It is shown that theidentification of B stars is practicable only at a good observing siteand that if H-beta photometry is also obtained, sdOB, sdB, and hothorizontal branch B stars can be distinguished from normal stars bytheir position in the beta/c(0) diagram.
| 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.
| Mean absolute magnitude of the blue stars at high galactic latitude.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962AJ.....67..740K&db_key=AST
| A search for blue stars in high galactic latitudes.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958AJ.....63..484C&db_key=AST
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Посматрања и Астрометриски подаци
| Сазвежђа: | Девица |
| Ректацензија: | 13h42m19.01s |
| Deклинација: | +01°30'18.7" |
| Apparent магнитуда: | 10.222 |
| Proper motion RA: | -6.1 |
| Proper motion Dec: | 0.5 |
| B-T magnitude: | 10.239 |
| V-T magnitude: | 10.224 |
Каталог и designations:
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