共查询到20条相似文献，搜索用时 15 毫秒
1.
Chris Koen 《Monthly notices of the Royal Astronomical Society》1998,300(2):567-572
The results of 37 h of high-speed photometry of KPD 2109+4401 are described. At least five periodicities in the range 182–198 s are consistently present in the observations, with amplitudes in the range 1–6 mmag. Results of simultaneous multicolour high-speed photometry with the Stiening photometer are also presented; these data could in principle be used for mode identification of the periodicities. The results of a preliminary study suggest that the pulsations may all be ℓ = 1 and 2 modes. Properties of the star are compared with those of the other EC 14026 stars. 相似文献
2.
J. W. Campbell 《Astrophysics and Space Science》1971,11(3):417-422
A stellar photometer utilizing a Cassegrain telescope optical system was flown in a Skylark rocket. The photometer scanned the night sky using the precessional and roll motions of the rocket and obtained observations of some ninety-two stars at a wavelength of 1450 Å. 相似文献
3.
D. Stello T. Arentoft T. R. Bedding M. Y. Bouzid H. Bruntt Z. Csubry T. H. Dall Z. E. Dind S. Frandsen R. L. Gilliland A. P. Jacob H. R. Jensen Y. B. Kang S.-L. Kim L. L. Kiss H. Kjeldsen J.-R. Koo J.-A. Lee C.-U. Lee J. Nuspl C. Sterken R. Szabó 《Monthly notices of the Royal Astronomical Society》2006,373(3):1141-1150
We report on an ambitious multisite campaign aimed at detecting stellar variability, particularly solar-like oscillations, in the red giant stars in the open cluster M67 (NGC 2682). During the six-week observing run, which comprised 164 telescope nights, we used nine 0.6-m to 2.1-m class telescopes located around the world to obtain uninterrupted time series photometry. We outline here the data acquisition and reduction, with emphasis on the optimization of the signal-to-noise ratio of the low-amplitude (50–500 μmag) solar-like oscillations. This includes a new and efficient method for obtaining the linearity profile of the CCD response at ultrahigh precision (∼10 parts per million). The noise in the final time series is 0.50 mmag per minute integration for the best site, while the noise in the Fourier spectrum of all sites combined is 20 μmag. In addition to the red giant stars, this data set proves to be very valuable for studying high-amplitude variable stars such as eclipsing binaries, W UMa systems and δ Scuti stars. 相似文献
4.
We analyze long-term UBV observations and ASAS-3 photometry for five candidates for protoplanetary nebulae—F and G supergiants with infrared excesses
at highG alactic latitudes—V340 Ser, IRAS 05113+1347, V552 Pup, V448 Lac, and RV Col. These stars exhibit quasi-periodic multifrequency
light variations caused by pulsations with characteristic time scales from 83 to 139 days, depending on the stellar temperature.
Cooler stars undergo variations with larger amplitudes and periods. The variations at close frequencies with a period ratio
of 1.03–1.09 are responsible for the amplitude modulation revealed for most program stars. 相似文献
5.
B. N. Ashoka Kumar V. C. Babu S. Seetha V. Girish S. K. Gupta Ram Sagar S. Joshi P. Narang 《Journal of Astrophysics and Astronomy》2001,22(1):131-144
The design and performance of a portable three channel photometer installed at the Uttar Pradesh State Observatory (UPSO),
Naini Tal is described. The photometer is modular and the whole unit can be disassembled as individual channels such that
the system can also be used as a single channel or two channel photometer. The system also has provision to monitor a guide
star. The instrument was put into operation since November 1999 on the 1m Sampurnanand telescope at UPSO, Naini Tal. Since
then, it is used extensively for the ‘Survey of rapidly oscillating Ap (roAp) stars in the northern sky’ from UPSO. Observational
results using this new photometer in its initial phase of operation are discussed. The advantage of having continuous sky
measurement is demonstrated. 相似文献
6.
K. V. K. Iyengar F. Strafella D. Lorenzetti C. B. Cosmovici 《Journal of Astrophysics and Astronomy》1982,3(4):451-463
Using an Infrared photometer with InSb photovoltaic detector at the 182cm Copernicus telescope of the Asiago Observatory,
Italy, we have measured theJHKL’ M magnitudes of 12 IRC sources 7 of which are very late type stars with [ICIT -K] greater than 5 magnitudes. These data have been fitted to blackbody distributions to obtain their effective temperatures.
The present data, in combination with other available photometric data at longer wavelengths seems to indicate excess emission
at 11 μm from sources 10066, 10510 and 10234, and at 19.8 μm from source 20052. The source 60098 shows extreme infrared colours.
Work carried out when the first author was a guest scientist at Max Planck-Institut für Extraterrestrische Physik,Garching FRG. 相似文献
7.
The search of roAp stars at Mt. Dushak-Erekdag Observatory was started in 1992 using the 0.8 m Odessa telescope equipped with
a two-star high-speed photometer. We have observed more than a dozen stars so far and discovered HD 99563 as roAp star while
BD+8087 is suspected to have rapid oscillations. Negative results of our observations for the search of rapid oscillations
in four stars in NGC 752 are also discussed. 相似文献
8.
We report the results of spectropolarimetric observations of the supergiant ζ Ori A made with 6-m BTA telescope of the SAO RAS. We found regular variations of line profiles in the spectrum of the star
with a period of 1–3 hours and point to their possible association with nonradial photospheric pulsations. We also searched
for a possible weak magnetic field in ζ Ori A, but observations did not confirm the existence of such a field in the star considered. 相似文献
9.
We have analyzed our long-term (1995–2008) JHKLM photometry for three variable RV Tau supergiants. It follows from this analysis that: the amplitude of the JHK brightness variations is approximately the same, 0
m
. 9–1
m
, for the three stars; a negative linear trend is noticeable in the variations of the mean J brightness for AC Her; and the mean J brightness of R Sct and V Vul remained constant. The observed J brightness fluctuations in the supergiants are shown to be consistent either only with the temperature pulsations (AC Her
and V Vul) or with the temperature and radial pulsations (R Sct). We have detected long-term pulsations in the J brightness and J-H color variations of the supergiants with the following characteristic time scales: ∼1500 days (AC Her), ∼3500 days (R Sct),
and ∼800 and ∼1500 days (V Vul). Our search for a periodic component in the infrared brightness variations of the three stars
has revealed periods that differ from those obtained from optical observations. We show that relatively hot dust shells (T
d ∼ 700–800 K) exist around the supergiants under study; the densest and most massive shell was observed for V Vul. The ranges
of optical-depth variations for the dust shells were τ(1.25 μm) ≈ 0.04–0.10 (AC Her), ≈0.02–0.12 (R Sct), and ≈0.18–0.32 (V Vul). The spectral types in the infrared varied over
narrower ranges than those that followed from optical observations of these stars. 相似文献
10.
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
11.
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
12.
High speed photometric observations of the dwarf nova VSX J074727.6 + 065050 made in December 2009 during quiescence show
an orbital modulation at P
orb
=85.6 min. They also show that the star is a member of the relatively rare CV/ZZ group, i.e. the accreting white dwarf primary
has non-radial pulsations. The two regions of oscillating power are at 684 s and 238 s. There is some evidence for hidden
∼1 μHz fine structure splitting, which has been seen in three other CV/ZZ stars. 相似文献
13.
M. Morales‐Caldern D. Barrado y Navascus J. A. Caballero E. L. Martín 《Astronomische Nachrichten》2005,326(10):1065-1067
We present the results of the optical photometric observations of the Pleiades (125 Myr) cluster. The aim of this research is to look for variability, both due to rotation of single stars and the presence of eclipsing binaries. We have used differential photometry and two different methods of statistical analysis of the data.We have found variability in the Pleiades cluster with amplitudes of about 50 mmag and uncertainties of 5 mmag until I=17.9, well within the brown dwarf regime. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
14.
A. A. Lutovinov R. A. Burenin M.G. Revnivtsev V. F. Suleimanov A. Yu. Tkachenko 《Astronomy Letters》2010,36(12):904-909
We present the results of our optical identification of the X-ray source IGR J16547-1916 detected by the INTEGRAL observatory
during a deep all-sky survey. Analysis of the spectroscopic data from the SWIFT and INTEGRAL observatories in the X-ray energy
band and from the BTA (Special Astrophysical Observatory) telescope in the optical band has shown that the source is most
likely an intermediate polar—an accreting white dwarf with the mass ofM
WD μ 0.85M
⊙ binary system. Subsequent studies of the object’s rapid variability with the RTT-150 telescope have confirmed this conclusion
by revealing periodic pulsations of its optical emission with a period of ≈550 s. 相似文献
15.
We report observations of 24 stars in the fields of the three Seyfert galaxies MCG +08-23-067, Mrk 817, and Mrk 290. The observations
were made with a CCD array photometer in the BVRcIc bands. The V magnitudes of the observed stars ranged from 13.5 and 17.2.
For stars of approximate magnitude 15, the typical photometric errors are 0.010, 0.011, 0.008 and 0.011 magnitude in the BVRI
bands, respectively. The BVRI magnitudes of all these stars were not known previously. In the field of the galaxy Mrk 290
a star has been found that probably has a periodic brightness variation with P=1.518 days and the mean value V=14.80 and which
may belong to the class of “spotted” stars. 14′x14′ charts are supplied for identifying the stars. These results can be used
for differential photometry of active galactic nuclei in the BVRI bands.
__________
Translated from Astrofizika, Vol. 51, No. 1, pp. 41–50 (February 2008). 相似文献
16.
A system for obtaining high-precision radial velocities of solar-type stars by spectral cross-correlation has been established at the Mt John University Observatory. The use of a fibre-feed between the telescope and échelle spectrograph has enabled a stability such that we can achieve a precision of better than 50 m s–1.A programme of radial-velocity observations of 29 southern solar-type stars—of which two are IAU radial velocity standard stars—is under way with the prime objective being a search for low-mass companions to the stars. Ten further IAU radial-velocity standard stars are also being monitored. 相似文献
17.
Differential BVR photometric observations of the three RS CVn binary stars: V711 Tau, UX Ari and IM Peg obtained during the period November 26, 1994–February 24, 1995 using the 0.35 m reflector telescope equipped with photoelectric photometer are presented. Analysis of light curves shows significant changes in shape, amplitude as well as the phases of minimum light of all the three binaries. The amplitude of IM Peg, in particular, is found to have reached a larger value in the present epoch of observation than reported earlier. 相似文献
18.
Joyce Ann Guzik 《Astrophysics and Space Science》2011,336(1):95-101
Advances in stellar interior modeling are being driven by new data from large-scale surveys and high-precision photometric
and spectroscopic observations. Here we focus on single stars in normal evolutionary phases; we will not discuss the many
advances in modeling star formation, interacting binaries, supernovae, or neutron stars. We review briefly: (1) updates to
input physics of stellar models; (2) progress in two and three-dimensional evolution and hydrodynamic models; (3) insights
from oscillation data used to infer stellar interior structure and validate model predictions (asteroseismology). We close
by highlighting a few outstanding problems, e.g., the driving mechanisms for hybrid γ Dor/δ Sct star pulsations, the cause of giant eruptions seen in luminous blue variables such as η Car and P Cyg, and the solar abundance problem. 相似文献
19.
The Ap Sr(CrEu) star HD 75425 is shown to be pulsating with a 30- min period. This is unusually short for a δ Scuti star and
about double the period of any known roAp star. The star is shown to be constant at the level of 0.35 mmag in the normal frequency
regime of roAp pulsation (900≤ν≤ 2500 μHz). The pulsations in HD 75425 are modulated in amplitude, but the frequencies causing
this modulation cannot be identified with the data in hand. HD 75425 is a very close visual double with an insecure Ap classification
which needs to be reexamined. If the Ap classification of HD 75425 is correct, and the pulsations can be linked to the peculiar
star, then this δ Scuti-like variability is of considerable interest.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
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