Charts

One of the most daunting tasks new observers encounter is actually locating variable stars in the sky. Although finding the region of the sky where the variable resides may be straightforward, the actual identification of the variable is a learned skill involving patience, persistence, and a good chart. You will find that several types of charts exist. First, you'll need finding charts. The purpose of a finding chart is to get you to the approximate vicinity of the variable star that you want...

RCB R Coronae Borealis stars

- These are hydrogen-poor, carbon- and helium-rich, high-luminosity stars belonging to the spectral types Bpe-R, which are simultaneously eruptive and pulsating variables. They show slow non-periodic fadings by lm-9' in V lasting from a month or more to several hundred days. These changes are superposed on cyclic pulsations with amplitudes up to several tenths of a magnitude and periods in the range of 30d-l00d. GCVS Variables of the R Coronae Borealis type are hydrogen-poor, carbon- and...

Data Reduction

After collecting your observational data, the first step that you must take in analyzing variable-star data is to organize it. When organizing variable-star data, the date time of the observation, the estimated magnitude of the variable star and the star with which it is being compared and perhaps a remark regarding special conditions are necessary. In some cases, more information is recorded but for basic analysis of variable-star data, we will use the date time and magnitude of the star being...

Preparing Your Own Charts

Some of the astronomical associations are not going to be happy with this section of the book (they really like you to use their charts) but for you to truly understand how a star chart works you must make and use a few of your own. Besides, in some cases, you'll find no charts Supernova chart for NGC 1365. Chart provided by the AAVSO. Used with permission. 19C0J 0329-36 28'7 (2000) 03h33m26s -SB OS'i Drav*iby KM8 0 SM 200 1dj is located aoout 90' westand Pom Digitized Sky Survey 10 south of...

PER 53 Persei stars

- Non-radial g-mode pulsating stars of spectral type 09-B5 showing line profile variations with periods ranging from ff 16 to not recognized within the GCVS 53 Persei3 stars surround the instability zone of the ft Cephei stars on the HR diagram with spectral types that range from 09 through B5. Suggestions have been made to add the 53 Persei star group to the variable stars observed in the range B3-B8 and called mid B variables. Eventually, it was decided to separate the two groups and to...

Selecting Variable Star Targets

By now, you should feel comfortable with your growing knowledge regarding variable stars and you will probably have little difficulty selecting the variable stars that you wish to begin observing. If I'm wrong and you still feel a bit unsure of yourself, let me help a little. When selecting a variable star that will be suitable for observation, consider these thoughts Which stars are visible during the current season How hard do I want to hunt for a variable star Are there charts available for...

EW W Ursae Majoris eclipsing systems

- These are eclipsers with periods shorter than 1 day, consisting of ellipsoidal components almost in contact and having light curves for which it is impossible to specify the exact times of onset and end of eclipses. The depths of the primary and secondary minima are almost equal or differ insignificantly. Light amplitudes are usually < 0.8 mag in V. The components generally belong to spectral types F-G and later. GCVS Mixed stars gg Small amplitudes f Mixed periods < > CCD or PEP PARCOS...

Sxari Sx Arietis7 variable stars

- These stars are main-sequence B0p-B9p stars with variable intensity He I and Si III lines and magnetic fields. They are sometimes called helium variables. Periods of light and magnetic field changes (about 1 ) coincide with rotational periods, while amplitudes are 0 1 in V. These stars are high-temperature analogs of the ACV variables. GCVS Many years ago, these stars were called spectrum variables of type-A, silicon variables, helium variables, or Ap silicon stars. Now, the SX Arietis stars...

Close Binary Eclipsing Systems

We adopt a triple system of classifying eclipsing binary systems according to the shape of the combined light curve, as well as to physical and evolutionary characteristics of their components. The classification based on light curves is simple, traditional, and suits the observers the second and third classification methods take into account positions of the binary-system components in the (Mv, B-V) diagram and the degree of inner Roche lobe filling. Estimates are made by applying the simple...

Vsge V Sagittae stars

- Stars of this type are often classified as novalike cataclysmic variables but, in fact, they do not fit into any of the patterns established for this class. The nature of these stars is still not clear, but there seems to be a consensus in the literature that they are binary systems with an evolved component. The nature of this component, however, has not been clearly established. Ideas involving a subdwarf, white dwarf, neutron star, curve of RX And UGZ). Data provided by the VSNET. Used...

RS RS Canum Venaticorum stars

- This type is ascribed to close binary systems with spectra showing Ca II H and K in emission, their components having increased chromospheric activity that causes quasi-periodic light variability. The period of variation is close to the orbital one, and the variable amplitude is usually as great as 0.'2 in V. They are X-ray sources and rotating variables. RS CVn itself is also an eclipsing system. GCVS Canis Venatici, the Hunting Dogs, identified as Asterion and Chara, are usually depicted as...

Using a Telescope for VSO

Do not worry about what telescope works best for variable-star observing. Use what you have or what you can afford. If you are new to amateur astronomy, I will tell you something that will take years to discover on your own. You will never be satisfied with the telescope that you have. It will be too small, too big, too heavy, too light, lacking a computer system, without motor drive the list is perpetual. You must, at some point, just say enough is enough, and use what you have to its full...

Fkcom Fk Comae Bernices6 stars

- These are rapidly rotating giants with nonuniform surface brightnesses, which have spectral types G-K with broad H and K Ca 11 emission and sometimes Ha. They may also be spectral binary systems. Periods of light variation (up to several days) are equal to rotational periods, and amplitudes are several tenths of a magnitude. It is not excluded that these objects are the product of further evolution of EW (W UMa) close binary systems. GCVS FK Comae variables are rapidly rotating giant stars...

RV RV Tauri stars

- These are radially pulsating supergiants having spectral types F-G at maximum light and K-M at minimum. The light curves are characterized by the presence of double waves with alternating primary and secondary minima that can vary in depth so that primary minima may become secondary and vice versa. The complete light amplitude may reach 3'-4m in V. Periods between two adjacent primary minima (usually called formal periods) lie in the range 30''-150'' (these are the periods appearing in the...

How Color Affects VSO

As you know, the human eye is an extraordinary detector of color under bright conditions. You also know that the color receptors, the cone cells, do not function well at night and as a result you will usually see no color. You have no doubt noticed that you are unable to distinguish the colors of vehicles or of the clothing of people walking in parking lots at night or along a street that is poorly illuminated. Because rod cells and cone cells are each most sensitive to different colors, the...

TOADS Tremendous outburst amplitude dwarf novae

- In 1995, Howell, Szkody and Cannizzo distinguished a particular type of dwarf novae, characterized by the very large outburst amplitudes of their optical outbursts (6 to 10 magnitudes) and very long intervals between the outbursts (months to decades). These TOADs are a subset of the SU UMa systems (dwarf novae that show both normal outbursts and super-outburst). Apart from the very long intervals and the very large amplitudes, TOADs also differ from the other SU UMa systems in that almost all...

Oculars

Eyepieces, correctly called oculars, will, without any doubt, be the first accessory that you purchase after your telescope. Without oculars, you will not be able to see anything of importance or interest. Additional oculars, beyond the one or two supplied with most telescopes, make visual observing much more enjoyable and most variable-star observers have several oculars. Like camera lenses, they determine the field of view and magnification seen through your telescope. Owning a proper...

The Argelander Method of Estimating Brightness

This is the method developed by Fredrich Wilhelm August Argelander in 1840. You must select two comparison stars that are close in brightness to the variable. Variable star charts have many comparison stars from which you may choose so doing so should be fairly easy. One of the comparison stars should be slightly brighter than the variable star and the other comparison star should be slightly fainter than the variable star. Using a method called interpolation, you're going to estimate the...

CEP Cepheid stars

- Radial pulsating, high luminosity (classes Ib-II) variables with periods in the range ld-135d and amplitudes from several hundredths to 2' in V (in the B band, the amplitudes are greater). Spectral type at maximum light is F at minimum, the types are G-K and Bright stars Mixed amplitudes fl long periods < 3> CCD or PEP the periods of light variation are longer the later the spectral type. The radial-velocity curves are practically reflections of the light curves, the maximum of the...

N Novae

- Close binary systems with orbital periods from ff 05 to 230 . One of the components of these systems is a hot dwarf star that suddenly, during a time interval from one to several dozen or several hundred days, increases it brightness by 7'-19' in V, then returns gradually to its former brightness over several months, years, or decades. Small changes at minimum light may be present. Cool components may be giants, subgiants, or dwarfs of K-M type. The spectra of novae near maximum light...

RR RR Lyrae stars

Radially pulsating A-F stars having amplitudes from 0.'2 to 2' in V. Cases of variable light-curve shapes as well as variable periods are known. If these changes are periodic, they are called the Blazhko effect. Traditionally, RR Lyr stars are sometimes called short-peripd Cepheids or cluster-type variables. The majority of these stars belong to the spherical component of the Galaxy they are present, sometimes in large numbers, in some globular clusters, where they are known as pulsating...

The Pogson Method of Estimating Brightness

Norman Pogson is a well-known variable-star observer from the nineteenth century. He developed a procedure that differs from Argelander's method in that each step is determined to be precisely OTl. This method requires you to compare a variable star with a single comparison star using a previously memorized interval of O'Vl. You then observe the variable again, using a different comparison star. The variable's magnitude is deduced later. Your first observation might be recorded as A - 5,...

ACV a2 Canum Venaticorum stars

- These are main-sequence stars with spectral types B8p-A7p and displaying strong magnetic fields. Spectra show abnormally strong lines of Si, Sr, Cr, and rare earths whose intensities vary with rotation, magnetic field, and brightness changes (05-160d or more). The amplitudes of the light changes are usually in the range of 0.'01-0.'I in V. ACVO (subtype) - Rapidly oscillating a2 Canum Venaticorum variables. These are nonra-dially pulsating, rotating magnetic variables of Ap spectral type....

Time Series Analysis Using TS11

Time series analysis allows you to search for periodic variability. Periodic variability means that the varying brightness of the star repeats with a good degree of precision. It's important to remember that not all variable stars are strictly periodic, even though they may vary in brightness. Cataclysmic variables vary in brightness and are usually said to have a period even though there can be great differences in time between their outbursts. The program TS11, provided by the AAVSO, will...

Dcep

- These are the classical Cepheids, or S Cephei variables. Comparatively young objects that have left the main sequence and evolved into the instability strip of the HR diagram, they obey the well-known Cepheid period-luminosity relation and belong to the young disk population. DCEP stars are present in open clusters. They display a certain relation between the shapes of their light curves and their periods. DCEPS (subtype) -These are S Cep variables having light amplitudes < 0.'5 in V (<...

WR Wolf Rayet stars

- Stars with broadband emission features of He I and He II as well as C II-C IV, 0 II-OIV, and N II-N V. They display irregular light changes with amplitudes up to 0.'l in V, which are probably caused by physical processes, in particular, by non-stable mass outflow from their atmosphere. GCVS Wolf-Rayet (WR) stars, named after the French astronomers Charles Wolf and Georges Rayet, who discovered them in 1867, are as strange as the luminous blue variables. WR stars are luminous hot supergiants...

Using Binoculars for VSO

Using binoculars to observe variable stars is an excellent decision because binoculars offer several advantages over a telescope when it comes to observing variable stars. First, they are easy to use and require a minimum amount of effort to set up and take down. Secondly, binoculars offer a wider field of view so that finding comparison stars is relatively easy. If you believe that binoculars will not allow you to make detailed observations or will in some way inhibit your ability to detect...

EA 3 Persei stars

- Binaries with spherical or slightly ellipsoidal components. It is possible to specify for their light curves the moments of the beginning and end of the eclipses. Between eclipses the light remains almost constant or varies insignificantly because of reflection effects, slight ellipsoidality of components, or physical variations. Secondary minima may be absent. An extremely wide range of periods is observed, from 01 2 to > 104 days. Light amplitudes are also quite different and may reach...

Rotating Variable Stars

Variable stars with nonuniform surface brightness and or ellipsoidal shapes, whose variability is caused by axial rotation with respect to an observer. The nonuniformity of surface brightness distributions may be caused by the presence of spots or by some thermal or chemical inhomogeneity of the atmosphere caused by a magnetic field whose axis is not coincident with the rotation axis. There are over 900 stars classified as rotating variables within the General Catalog of Variable Stars. The a2...

ER UMa ER Ursae Majoris stars or RZ Leo Minoris stars

- ER Ursae Majoris stars are dwarf nova subtypes that exhibit a standstill like phase similar to Z Camelopar-dalis stars. They exhibit short outbursts that resemble normal outbursts of SU Ursae Majoris stars in regards to their rapid decline rate, not recognized within the GCVS ER UMa was originally discovered as an ultraviolet-excess object and confirmed to be a cataclysmic variable in 1986. Until very recently the object had been little studied. It was only in 1992 that the dwarf nova nature...

Database Management

Some types of databases will allow you to categorize, sort and retrieve the observations that you will collect over the years. Perhaps, in the beginning you may not feel a need for a computerized method, but as the years go by, you'll be surprised at the amount of information that you collect. Within any database system, the field names are used to label each category of information, such as date, brightness estimate, type of observation, etc. Take a good look at your analysis needs and develop...

Be B[e stars

- It becomes more and more clear that, although the majority of Be stars are photometrically variable, not all of them could be properly called GCAS variables. Quite a number of them show small-scale variations not necessarily related to shell events in some cases the variations are quasi-periodic. By now we are not able to present an elaborated system of classification for Be variables, but we adopt a decision that in the cases when a Be variable cannot be readily described as a GCAS star we...

Estimating Magnitudes Using Interpolation

Any optical instrument's resolving power is greatest at its center of field, in other words, when the star is centered within the ocular. As a result, when the comparison star and the variable are widely separated, they should not be viewed simultaneously. They should be brought successively into the center of the field of view. You will do this by making slight adjustments, moving the optical tube assembly (OTA) of your telescope so that each star is centered. Some times you'll need to repeat...

Photoelectric Photometry PEP

A stellar photometer is an electrical device that measures the amount of light received from a single star. The process of using a stellar photometer to measure the light intensity of a star is called photoelectric photometry and is abbreviated as PEP. People who make photoelectric photometry measurements are sometimes called Peppers. There is much interest within the amateur community regarding PEP. For example, the International Amateur-Professional Photoelectric Photometry (IAPPP) group was...

Computer Programs for Data Analysis

Available today are computer programs that will assist you in performing sophisticated mathematical analysis of your data such as searching for and fitting sinusoidal patterns within time series data, Discrete Fourier analysis, and phase dispersion minimization (PDM). Without possessing an advanced degree in mathematics, you will be able to use these powerful mathematical tools to aid you in understanding variable stars. Of course, an understanding of mathematical methods that goes beyond the...

RS CVn RS Canum Venaticorum eclipsing systems

- A significant property of these systems is the presence in their spectra of strong CA II, H and K emission lines of variable intensity, indicating increased chromo-spheric activity of the solar type. These systems are also characterized by the presence of radio and X-ray emission. Some have light curves that exhibit quasi-sine waves outside eclipses, with amplitudes and positions changing slowly with time. The presence of this wave (often called a distortion wave) is explained by differential...

ZZ ZZ Ceti stars

- These are non-radially pulsating white dwarfs that change their brightness with periods from 30 s to 25 min and amplitudes from 0.'001 to 0.'2 in V. They usually show several close period values. Flares of 1 magnitude are sometimes observed however, these may be explained by the presence of close UV Ceti companions. These variables are divided into the following subtypes ZZA (subtype) - ZZ Cet-type variables of DA spectral type (ZZ Cet) having only hydrogen absorption lines in their spectra....

ACYG Cygni stars

- Non-radial pulsating supergiants of Bep-Aepla spectral types. The light changes with amplitudes of the order of 0.'l often seem irregular, being caused by the superposition of many oscillations with close periods. Cycles from several days to several weeks are observed. GCVS a Cygni4 variable stars are spectral type B and A, luminous, pulsating supergiant stars. You will notice that B- and A-type stars are located toward the upper left portion of the HR diagram where the relatively young, hot...

Pvtel Pv Telescopii stars

- These are helium supergiant Bp stars with weak hydrogen lines and enhanced lines of He and C. They pulsate with periods of ff 1 to or vary in brightness with an amplitude ff'.'l in V during a time interval of about a year. GCVS PV Telescopii stars in the past were called helium stars, helium horizontal branch stars, extreme helium EHe stars, and hydrogen-deficient binary HdB stars. Small amplitude light and radial velocity variations of the R Coronae Borealis RCB variable RY Sgr have long...