Times of maximum of KZ Hya from OACS -UNAH

2020 ◽  
Vol 8 (2) ◽  
pp. 90-93
Author(s):  
M. Meza ◽  
A. Pineda ◽  
C. Argueta ◽  
Y. Mendoza ◽  
M. C. Pereira ◽  
...  
Keyword(s):  
Variable Star ◽  
Variable Stars ◽  
Surface Layers ◽  
Maximum Light ◽  
Photometric Observations

A pulsating variable star is one whose brightness changes periodically due to the expansion and contraction of the surface layers of the star. Several times of maximum light can be obtained in brief observations of SX Phoenicis variable stars due to their short periods of pulsation (P ~ 1:0 - 1:75 h). We report three new times of maximum light of SX Phoenicis star KZ Hya obtained from photometric observations made on the night of April 5-6, 2019 from the Observatorio Astronómico Centroaméricano de Suyapa (OACS) of the Universidad Nacional Autónoma de Honduras

scholarly journals A Variable Star Survey of the Open Cluster NGC 2126

2004 ◽  
Vol 193 ◽  
pp. 162-165
Author(s):  
A. Derekas ◽  
L.L. Kiss ◽  
T.R. Bedding ◽  
A. Gáspár ◽  
K. Sárneczky ◽  
...  
Keyword(s):  
Variable Star ◽  
Open Cluster ◽  
Variable Stars ◽  
Time Span ◽  
Photometric Observations

AbstractWe present the first CCD photometric observations of the northern open cluster NGC 2126. Data were taken on eight nights in 2002 February and December with a total time span of ~57 hours. We have discovered six new variable stars and have estimated the main characteristics of the cluster.

scholarly journals Variable star observations with automatic telescopes

1986 ◽  
Vol 118 ◽  
pp. 47-55
Author(s):  
Russell M. Genet ◽  
Louis J. Boyd ◽  
Douglas S. Hall
Keyword(s):  
Variable Star ◽  
Wide Band ◽  
Variable Stars ◽  
Entire Class ◽  
Photometric Observations ◽  
The Cost ◽  
Rs Canum Venaticorum Binaries ◽  
Automatic Systems

Small automatic telescopes have been used for several years to make wide band, differential photometric observations of brighter variable stars. For example, a single automatic telescope located in Arizona has been used to study essentially the entire class of RS Canum Venaticorum binaries. These stars have changing spot structures that require once-a-night photometric observations - an ideal job for an automatic telescope located in the clear skies of Arizona. The operation of such automatic systems has become so routine that an “Automatic Photoelectric Telescope Service” now makes photometric observations for any institution so requesting. A list of stars is sent to the Arizona site of this service, and every three months the observational results are returned, with the cost typically being similar to the publication page charges. Currently the use of automatic telescopes is being extended to fainter stars and narrower bandwidths. For instance, a highly specialized one-meter telescope has been designed for automatic observations of Ca II K-line emissions from brighter active chromosphere stars. Further extensions of such automation seem likely.

FIRST RESULTS FROM TIEN-SHAN SURVEY TO SEARCH FOR VARIABLE STARS: LIGHTCURVE ANALYSIS AND VARIABLE STAR CLASSIFICATION

2020 ◽  
Vol 3 (331) ◽  
pp. 81-91
Author(s):  
Serebryanskiy A., ◽  
◽  
Aimanova G. K., ◽  
Kondratyeva L.N., ◽  
Omarov Ch., ◽  
...  
Keyword(s):  
Variable Star ◽  
Variable Stars ◽  
Tien Shan ◽  
First Results ◽  
Star Classification

scholarly journals The AAVSO and its Variable Star Databank on Pulsating Stars

1995 ◽  
Vol 155 ◽  
pp. 421-422 ◽  
Author(s):  
Janet A. Mattei
Keyword(s):  
Variable Star ◽  
American Association ◽  
Variable Stars ◽  
Pulsating Stars

AbstractThe American Association of Variable Stars Observers is the world’s largest organization of variable star observers. Its services to the astronomical community and database on pulsating variables are described.

scholarly journals The Massive Stellar Wind of the Hubble-Sandage Variable S Doradus

1986 ◽  
Vol 116 ◽  
pp. 235-236
Author(s):  
C. Leitherer ◽  
I. Appenzeller ◽  
G. Klare ◽  
H.J.G.L.M. Lamers ◽  
O. Stahl ◽  
...  
Keyword(s):  
High Resolution ◽  
Stellar Wind ◽  
Variable Star ◽  
Photometric Observations ◽  
Visual Range ◽  
Bright Phase

We present coordinated spectroscopic and photometric observations obtained during the present bright phase of the luminous variable star S Dor in the LMC. High resolution spectrograms in the satellite UV and in the visual range were obtained with IUE and with CASPEC (attached to the ESO 3.6-m telescope), respectively. Moreover, photometric UBVRIJHKL observations were carried out.

scholarly journals Optical photometric variable stars towards Cygnus OB7

2019 ◽  
Vol 487 (2) ◽  
pp. 1765-1776 ◽  
Author(s):  
Somnath Dutta ◽  
Soumen Mondal ◽  
Santosh Joshi ◽  
Ramkrishna Das
Keyword(s):  
Variable Stars ◽  
T Tauri Stars ◽  
Light Curves ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Rotation Rates ◽  
T Tauri ◽  
Photometric Observations ◽  
Sky Survey ◽  
Magnitude Diagram

ABSTRACT We present optical I-band light curves of the stars towards a star-forming region Cygnus OB7 from 17-night photometric observations. The light curves are generated from a total of 381 image frames with very good photometric precision. From the light curves of 1900 stars and their periodogram analyses, we detect 31 candidate variables including five previously identified. 14 out of 31 objects are periodic and exhibit the rotation rates in the range of 0.15–11.60 d. We characterize those candidate variables using optical/infrared colour–colour diagram and colour–magnitude diagram (CMD). From spectral indices of the candidate variables, it turns out that four are probably Classical T-Tauri stars (CTTSs), rest remain unclassified from present data, they are possibly field stars or discless pre-main-sequence stars towards the region. Based on their location on the various CMDs, the ages of two T Tauri Stars were estimated to be ∼5 Myr. The light curves indicate at least five of the periodic variables are eclipsing systems. The spatial distribution of young variable candidates on Planck 857 GHz (350 $\mu$m) and 2MASS (Two Micron All Sky Survey) Ks images suggest that at least two of the CTTSs are part of the active star-forming cloud Lynds 1003.

scholarly journals The Carina Dwarf Galaxy Variable Star Population

2002 ◽  
Vol 185 ◽  
pp. 134-135
Author(s):  
V. Ripepi ◽  
M. Dall’Ora ◽  
L. Pulone ◽  
M. Castellani ◽  
C. Corsi ◽  
...  
Keyword(s):  
Variable Star ◽  
Dwarf Galaxy ◽  
Variable Stars ◽  
Photometric Data ◽  
Wide Field ◽  
Preliminary Results

AbstractWe present some preliminary results based on new observations of the variable stars belonging to the Carina Dwarf Galaxy (DG). Photometric data were collected with the two wide field imagers available at ESO ([email protected].) and CTIO (4m prime focus).

scholarly journals AAVSO’s Astronomical Data Bank

1979 ◽  
Vol 53 ◽  
pp. 506-506
Author(s):  
Janet Akyüz Mattei
Keyword(s):  
Variable Star ◽  
Data Bank ◽  
Variable Stars ◽  
Astronomical Data ◽  
The World ◽  
Visual Magnitude ◽  
Recurrent Nova

The AAVSO founded in 1911 is the largest organization of variable star observers in the world, with 1100 members in 49 states and 38 countries. AAVSO Headquarters, in Cambridge, MA, receives about 150,000 observations a year from about 400 active observers. Since 1911, over 4 million observations have been compiled. The limiting visual magnitude of observations is about AAVSO’s observing program contains about 2000 variable stars of the following types: Mira (825); semiregular (350); cataclysmic-U Gem, Z Cam, nova, recurrent nova, novalike, symbiotic (200); cepheid (120); R Coronae Borealis (20); RV Tauri (30); nebular (100); flare (15); irregular (140); suspected variables (200). AAVSO has finder charts for most of the stars.

scholarly journals CCD VI time-series of the extremely metal-poor globular cluster M92: revisiting its variable star population

2020 ◽  
Vol 494 (3) ◽  
pp. 3212-3226 ◽  
Author(s):  
M A Yepez ◽  
A Arellano Ferro ◽  
D Deras
Keyword(s):  
Time Series ◽  
Globular Cluster ◽  
Variable Star ◽  
Variable Stars ◽  
Frequency Spectra ◽  
Fourier Decomposition ◽  
Rr Lyrae ◽  
Blazhko Effect ◽  
New Variables ◽  
Gaia Dr2

ABSTRACT We present an analysis of VI CCD time-series photometry of the Oo II type globular cluster M92. The variable star population of the cluster is studied with the aim of revising their classifications, identifications, frequency spectra, and to select indicators of the parental cluster metallicity and distance. The Fourier decomposition of RR Lyrae light curves lead to the estimation of mean [Fe/H]spec = −2.20 ± 0.18 and distance of 8.3 ± 0.2 kpc. Four new variables are reported: one RRd (V40), a multimode SX Phe (V41), an SR (V42), and one RRc (F1) that is most likely not a cluster member. The AC nature of V7 is confirmed. The double mode nature of the RRc star V11 is not confirmed and its amplitude modulations are most likely due to the Blazhko effect. Two modes are found in the known RRc variable V13. It is argued that the variable V30, previously classified as RRab is, in fact, a BL Her-type star not belonging to the cluster. Using the Gaia-DR2 proper motions, we identified 5012 stars in the field of the cluster, which are very likely cluster members, and for which we possess photometry, enabling the production of a refined colour–magnitude diagram. This also allowed us to identify a few variable stars that do not belong to the cluster. The RR Lyrae pulsation modes on the HB are cleanly separated by the first overtone red edge, a common feature in all Oo II-type clusters.

scholarly journals The Large Magellanic Cloud R CrB Star - HV 12842

1985 ◽  
Vol 87 ◽  
pp. 225-228
Author(s):  
D.H. Morgan ◽  
K. Nandy ◽  
N. Kameswara Rao
Keyword(s):  
Spectral Type ◽  
Large Magellanic Cloud ◽  
Variable Stars ◽  
Magellanic Cloud ◽  
Schmidt Telescope ◽  
Maximum Light ◽  
The North ◽  
North Eastern ◽  
The Uk ◽  
North Eastern Part

The star HV12842 is one of the 5 R CrB stars listed in the catalogue of variable stars in the LMC (Payne-Goposchkin 1971) and is located 4 deg. to the north of 30 Doradus. At this location it falls in the north-eastern part of one of two standard LMC fields used by the UK 1.2 m Schmidt Telescope. Since 1976 a series of I-plates (normally 90 minute exposures of hypersensitized Kodak IV-N emulsion through a Schott RG 715 filter) has been obtained on both the standard fields (LMC (N) and LMC (S)). This paper describes the behaviour of HV 12842 during the period 1976-1985 as it appears on the 38-I-plates of LMC(N) taken with the UK 1.2 m Schmidt Telescope. Earlier, the UBV magnitude at maximum light are given as V=13.65, B−V=0.51, U−B=−0.11 (Sherwood 1974) and the spectral type as F (Feast 1979).

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