共查询到20条相似文献,搜索用时 31 毫秒
1.
V. T. Doroshenko S. G. Sergeev Yu. S. Efimov S. Nazarov V. I. Pronik E. A. Sergeeva G. A. Sivtsov 《Astrophysics》2007,50(1):40-53
Observations with a matrix photometer are reported. The stellar magnitudes in the BVRcIc bands are estimated for 80 comparison
stars in the neighborhoods of 10 galaxies with active nuclei: 2 Seyfert galaxies, 4 quasars, and 4 BL Lac objects. The stellar
magnitudes of the observed stars range from 11 to 19m.5. For stars with magnitudes of 14–15m the typical photometric errors are 0m.011, 0m.008, 0m.006, and 0m.007 in the B, V, R, and I bands, respectively. The BVRI magnitudes for most of these stars were not known previously. 14′
× 14′ finding charts for these stars are included. These results can be used for differential BVRI photometry of active galactic
nuclei.
__________
Translated from Astrofizika, Vol. 50, No. 1, pp. 57–72 (February 2007). 相似文献
2.
V. T. Doroshenko S. G. Sergeev N. I. Merkulova E. A. Sergeeva Yu V. Golubinsky V. I. Pronik N. N. Okhmat 《Astrophysics》2005,48(2):156-178
Results are presented from CCD BVRI observations of comparison stars in the neighborhoods of 22 galaxies with active nuclei having right ascensions ranging from 0 to 12 hours, of which 19 are Seyfert galaxies. The observed stars have magnitudes ranging from V=11 to V=17. For stars brighter than V=14 the typical photometic error is 0.01m. The B, V, Rc, and Ic magnitudes of most of these stars were not known previously. 14′×14′ finding charts are included. These results can be used for differential photometry of the AGNs in the B, V, Rc, and Ic bands.__________Translated from Astrofizika, Vol. 48, No. 2, pp. 191–211 (May 2005). 相似文献
3.
V. T. Doroshenko S. G. Sergeev N. I. Merkulova E. A. Sergeeva Yu. V. Golubinsky V. I. Pronik N. N. Okhmat 《Astrophysics》2005,48(3):304-320
Results are presented from CCD BVRI-observations of 145 comparison stars in the neighborhoods of 14 Seyfert galaxies, 3 quasars, and 5 BL Lac objects with right ascensions of 12 to 24 hours. The magnitudes of the observed stars ranged from V=11 to V=17. The typical photometric error for stars brighter V=14 is 0m.01. The B, V, Rc, and Ic magnitudes of most of these stars were not known previously. 14′ x 14′ finding charts are provided. These results can be used for differential photometry of the nuclei of active galaxies in the B, V, Rc, and Ic bands.__________Translated from Astrofizika, Vol. 48, No. 3, pp. 365–379 (August 2005). 相似文献
4.
We present UBVRCIC magnitudes of 49 comparison stars in the fields of the Seyfert galaxies Mrk 335, Mrk 79, Mrk 279, Mrk 506, 3C 382, 3C 390.3, NGC 6814, Mrk 304, Ark 564, and NGC 7469 in order to facilitate the photometric monitoring of these objects; 36 of the stars have not been calibrated before. The comparison stars are situated in 5 × 5 arcmin fields centred on the Seyfert galaxies, their V band flux ranges from 11.7 to 18.2 mag with a median value of 16.3 mag, and their B – V colour index ranges from 0.4 to 1.6 mag with a median value of 0.8 mag. The median errors of the calibrated UBVRCIC magnitudes are 0.08, 0.04, 0.03, 0.04, and 0.06 mag, respectively. Comparison stars were calibrated for the first time in three of the fields (Mrk 506, 3C 382, and Mrk 304). The comparison sequences in the other fields were improved in various aspects. Extra stars were calibrated in four fields (Mrk 335, Mrk 79, NGC 6814, and NGC 7469) – most of these stars are fainter and are situated closer to the Seyfert galaxies compared to the existing comparison stars. The passband coverage of the sequences in five fields (Mrk 335, Mrk 79, Mrk 279, NGC 6814, and Ark 564) was complemented with the U band. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
G. V. Zajtseva 《Astrophysics》2010,53(4):573-574
The V magnitude and B-V and U-B color indices of comparison stars within distances of about 2′ from the variable Ry Tauri
are given. 相似文献
6.
Near infrared measurements in the J, H and K bands have been carried out for a number of symbiotic stars with the 1.5 m telescope
at the Rothney Astrophysical Observatory (RAO). A comparison with the earlier observations shows that the S-type symbiotic
stars do not have any significant variation in the infrared flux over the past five years. However a small variation ∼ 0.3
magnitude in the infrared flux has been detected for CH Cygni. The observations of HM Sagittae show large decreases in the
infrared flux compared to the previous measurements. The variability in the infrared fluxes of both these objects could be
attributed to a variation in the temperature due to the cooling of the dust shell. The variability observed for V1016 Cygni
is found consistent with the previous measurements. 相似文献
7.
Regina E. Schulte-Ladbeck Igor O. Drozdovsky Michèle Belfort Ulrich Hopp 《Astrophysics and Space Science》2003,284(2):909-912
Formation paradigms for massive galaxies have long centered around two antipodal hypotheses – the monolithic-collapse and
the accretion/merger scenarios. Empirical data on the stellar contents of galaxy halos is crucial in order to develop galaxy
formation and assembly scenarios which have their root in observations, rather than in numerical simulations. The Hubble Space
Telescope (HST) has enabled us to study directly individual stars in the nearby E/S0 galaxies Cen A, NGC 3115, NGC 5102, and
NGC 404. We here present and discuss HST single-star photometry in V and I bands. Using color-magnitude diagrams and stellar
luminosity functions, we gauge the galaxies' stellar contents. This can be done at more than one position in the halo, but
data with deeper limiting magnitudes are desired to quantify the variation of metallicity with galactocentric radius. We here
compare the color distributions of red giant stars with stellar isochrones, and we intercompare the galaxies' halo populations,
noting that their total absolute V magnitudes cover the range from about –21.5 to –17.5. In the future, we plan to model the
stellar metallicity distributions with the aim to constrain chemical enrichment scenarios, a step towards unravelling the
evolutionary history of elliptical and lenticular galaxies.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
Rob Cavallo Keith A. Arnaud Virginia Trimble 《Journal of Astrophysics and Astronomy》1993,14(3-4):141-143
Pointed ROSAT PSPC exposures of 9277 and 6992 sec, directed toward the nearby, single, cool, magnetic white dwarfs GR 290
and EG 250 yielded no counts significantly above the expected background rate. The corresponding flux limits (for an assumed
source temperature of l keV) are 1.0 and 1.7 × 10−14erg cm−2 s−1, within the 0.1–2.5 keV bandpass of the instrument (99% confidence limits). This is more than an order of magnitude below
the tentative detection level (for GR 290) and limits (for four other similar stars) obtained from archival Einstein data
in 1991. The corresponding limits on coronal electron density are comparable with those implied if cyclotron emission is not
responsible for any of the features observed in the optical spectra of magnetic white dwarfs. X-ray data currently provide
no evidence for the existence of coronae around these stars. A final long observation (25,000 sec of GD 356) is scheduled
for later this year on ROSAT, along with coordinated EUVE observations. 相似文献
9.
E. I. Terez 《Solar physics》1994,152(1):87-90
Based on long-term observations of the absolute energy distribution in stellar spectra (starting in 1975), and from a survey of the literature, 14 stars of early spectral type (B7 III–A7 V) were selected. The constancy of their brightness is beyond any doubt now. These stars, with visual magnitudes 0.0 to 4.8, can be recommended as spectrophotometric standards for the spectral region 310–750 nm. 相似文献
10.
Observations of the Pleiades cluster by the method of stellar tracks, carried out on the 40-inch Schmidt telescope of Byurakan
Astrophysical Observatory, have resulted in the detection of 49 flares from 38 stars, 17 of which were not previously known
to be flare stars. It is shown that for bright stars (U ≤ 16.0) the detection of flares in observations by the method of stellar
tracks is at least three times more efficient than for observations by the method of stellar chains. Another advantage of
the first method is that one can detect brief flares that last less than 6 min. The visual stellar magnitude at the minimum
for the brightest of the flare stars that we found is 11.92. This raised the upper luminosity limit of known flare stars in
the Pleiades by 0.21 magnitude. A comparison of the expected number of bright flare stars in the Pleiades with the number
of all bright members of the cluster (falling in the range from V ≈ 12.0 toV ≈16.0) suggested that all these stars evidently
must be flare stars.
Translated from Astrofizika, Vol. 42, No. 3, pp. 351–358, July–September, 1999. 相似文献
11.
S. Bilir S. Ak S. Karaali A. Cabrera-Lavers T. S. Chonis C. M. Gaskell † 《Monthly notices of the Royal Astronomical Society》2008,384(3):1178-1188
We present colour transformations for the conversion of the Two Micron All Sky Survey (2MASS) photometric system to the Johnson–Cousins UBVRI system and further into the Sloan Digital Sky Survey (SDSS) ugriz system. We have taken SDSS gri magnitudes of stars measured with the 2.5-m telescope from SDSS Data Release 5 (DR5), and BVRI and JHK s magnitudes from Stetson's catalogue and Cutri et al., respectively. We matched thousands of stars in the three photometric systems by their coordinates and obtained a homogeneous sample of 825 stars by the following constraints, which are not used in previous transformations: (1) the data are dereddened, (2) giants are omitted and (3) the sample stars selected are of the highest quality. We give metallicity, population type and transformations dependent on two colours. The transformations provide absolute magnitude and distance determinations which can be used in space density evaluations at short distances where some or all of the SDSS ugriz magnitudes are saturated. The combination of these densities with those evaluated at larger distances using SDSS ugriz photometry will supply accurate Galactic model parameters, particularly the local space densities for each population. 相似文献
12.
The results of a spectroscopic survey of late-type M stars in three regions of dark nebulae are given. The observations were
made on the 1-m Schmidt telescope of Byurakan Observatory with a 4° preobjective prism. A method of detecting late-type M
giants is developed on the basis of the presence of TiO absorption bands in their spectra. The area of the regions studied
is 48 sq. deg. We found 96 new late-type M stars, 22 of which exhibited brightness variability during our observations and
are new variable stars. The limiting magnitude on the plates obtained in red light is 16m.0, which enables us to state confidently that all late-type M stars (starting with M4) brighter than R = 15m.0 have been detected.
Translated from Astrofizika, Vol. 40, No. 4, pp. 595–607, October-December, 1997. 相似文献
13.
V. L. Karbovs’ky P. F. Lazorenko V. N. Andruk V. V. Kleshchenok M. O. Litvin K. O. Bogatyrev E. V. Denisyuk 《Kinematics and Physics of Celestial Bodies》2011,27(4):204-210
Specifications of a new Apogee Alta U47 CCD camera mounted at the Kyiv meridian axial circle (MAC) are presented. The camera
is based on the 1024 × 1024 pxl e2v CCD47-10 with pixel sizes of 13 × 13 μm. Observations are carried out in the scan-drift
mode with an effective exposure time of 77 s for equatorial stars. The MAC photometric system answers the standard Johnson
V band, the MAC limiting magnitude V is 17
m
. The test MAC observations of 2009 give positional accuracy and V magnitude errors equal to approximately 0.1″ and 0.09
m
, respectively, for Tycho-2 stars. The telescope is used for observations of equatorial stars with the purpose of detecting
their positions, proper motion, and brightness. 相似文献
14.
R. Poggiani 《Astrophysics and Space Science》2009,323(4):319-322
We report the spectroscopic observations of nova V2670 Oph secured at the Loiano Observatory, Italy, 39 days after the outburst.
The spectra of V2670 Oph showed auroral lines, suggesting that ionization was increasing. V2670 Oph is a fast nova, with a
decline rate by three magnitudes of 42 days. We have estimated the absolute magnitude at maximum and the distance of V2670
Oph. The nova achieved an absolute magnitude at maximum in the interval −7.9,…,−7.4. The distance of V2670 Oph is in the range
4.7–5.8 kpc. 相似文献
15.
V. N. Frolov Yu. K. Ananjevskaja D. L. Gorshanov E. V. Polyakov 《Astronomy Letters》2010,36(5):338-348
We present the results of our comprehensive study of the Galactic open star cluster NGC 6866. The positions of stars in the
investigated region have been obtained with the “Fantasy” automatic measuring machine from 10 plates of the normal astrograph
at the Pulkovo Astronomical Observatory. The size of the investigated field is 40′ × 40′, the limiting magnitude is B ∼ 16·
m
6, and the maximum epoch difference is 79 yr. For 1202 field stars, we have determined the relative proper motions with an
rms error of 2.5 mas yr−1. Out of them, 423 stars may be considered cluster members with a probability P > 70% according to the astrometric criterion. Photometric diagrams have been used as an additional criterion. We have performed
two-color BV CCD photometry of stars with the Pulkovo ZA-320M mirror astrograph. The U magnitudes from the literature have also been used to construct the two-color diagrams. A total of 267 stars have turned
out to be members of NGC 6866 according to the two criteria. We present refined physical parameters of the cluster and its
age estimate (5.6 × 108 yr). The cluster membership of red and blue giants, variable, double, and multiple stars is considered. We have found an
almost complete coincidence of the positions of one of the stars in the region (a cluster nonmember) and a soft X-ray source
in the ROSAT catalog. The “Fantasy” automatic measuring machine is described in the Appendix. 相似文献
16.
M. I. Wilkinson A. Vallenari C. Turon U. Munari D. Katz G. Bono M. Cropper A. Helmi N. Robichon F. Thévenin S. Vidrih T. Zwitter F. Arenou M.-O. Baylac G. Bertelli A. Bijaoui F. Boschi F. Castelli F. Crifo M. David A. Gomboc A. Gómez M. Haywood U. Jauregi P. de Laverny Y. Lebreton P. Marrese T. Marsh S. Mignot D. Morin S. Pasetto M. Perryman A. Pra A. Recio-Blanco F. Royer A. Sellier A. Siviero R. Sordo C. Soubiran L. Tomasella Y. Viala 《Monthly notices of the Royal Astronomical Society》2005,359(4):1306-1335
17.
对兴隆60cm望远镜主焦CCD系统的测光性能进行了测试和研究.测定了CCD快门时间函数,讨论了快门延迟效应对短时间曝光观测的可能影响.通过观测大批Landolt标准星,较准确地定出了BVRI宽带测光的星等系统转换关系,结果表明本系统与标准BVRI系统很接近.对CCD系统的天文测光精度作了仔细的检验和分析,并对PSF拟合测光和孔径测光两种方法进行了比较 相似文献
18.
V. M. Andruk V. M. Reshetnik Ya. O. Romanyuk V. V. Kleshchonok I. V. Khatko A. I. Yatsenko V. S. Samoylov 《Kinematics and Physics of Celestial Bodies》2012,28(6):296-303
We performed a series of CCD observations in BVRI bands of a celestial region in cluster M67 (NGC 2682) to study the photometric system of the Kyiv network telescope. The signal recording system consists of a CGE-1400 telescope, Celestron #94175 focal reducer, an automatic turret with a set of UBVRI filters, and a Rolera Mgi CCD camera. The operating field of the system is 10.62′ × 10.62′. CCD images are processed in the MIDAS/ROMAFOT package. The reduction coefficients of the instrumental photometric system relative to Johnson’s BVRI system are determined. The resulted value of the module of distance to cluster M67 V ? M V = 9.63 m does not contradict the results of other researchers. The mean square errors for one determination of stellar magnitude for different bands are 0.02–0.12 m . The errors in determining equatorial coordinates in the TYCHO-2 catalog system are ± 1″. 相似文献
19.
I. A. Tereshchenko V. G. Shevchenko Yu. N. Krugly 《Kinematics and Physics of Celestial Bodies》2010,26(2):89-93
We investigate the photometric system consisting of the AZT-8 telescope BVRI filters, and IMG 1024S CCD-camera. The coefficients
of the transformation from the instrumental values of magnitudes and color indexes to the standard Johnson-Cousins system
for the BVRI bands are derived. 相似文献
20.
We have applied the astrometric techniques devised by Murray for analysis of 48-inch Schmidt photographic data to SuperCOSMOS scans of UK Schmidt plates centred on Kapteyn's Selected Area 94 ( α =2h 53m , δ =0°). In this preliminary study, we combine astrometric data from four short-exposure V -band plates, taken in 1987 August (2 plates) and 1993 August (2 plates), with BVRI photometry from sky-limited plate material, to identify stars with proper motions exceeding 0.1 arcsec yr−1 . This paper discusses the completeness of the resulting sample and presents spectroscopy of 30 stars with μ >0.2 arcsec yr−1 . Based on the latter observations and the distribution in the [H V , ( V − I )] reduced proper-motion diagram, we have classified stars in the complete sample as candidate white dwarfs, main-sequence dwarfs and halo subdwarfs, and derived estimates of the disc and halo luminosity functions. 相似文献