Overview: Long-term visual light curves

Overview: Long-term visual light curves

This page gives background on our long-term visual data archives, with an emphasis on our data holdings for different classes of variable stars.  It is meant to give an overview of the AAVSO International Database (AID) to researchers interested in studying a number of different light curves of a given class, or who are interested in a summary of what the AAVSO's visual data archives have to offer.

Visual magnitude estimates

The AID contains several million visual magnitude estimates made by a few thousand visual observers over the past century.  While these data are made by the human eye, as an ensemble they have statistical properties very similar to those of instrumental photometry; large amounts of visual data can be treated in a statistically similar fashion as any other kind of photometric data, subject to similar uncertainties and biases.

These estimates are obtained by observing using their naked eyes (for the brightest stars), binoculars, or telescopes of various sizes.  The variable star's brightness is compared to previously established comparison stars within the field of view.  For stars where good sequences have been available throughout the observational history of the star, their lightcurves can be remarkably homogeneous.

For a fuller description of what visual magnitude estimates are and how they should be used, please see the Quickstart Guide to using AAVSO data.  For information on how to compare visual magnitudes to instrumental photometry, please see this bibliography of JAAVSO papers on the subject.

Data sources

AAVSO data comes from a number of sources.  Our largest source is the observer community itself; several hundred individuals freely submit observations directly to the AAVSO every year, and have done so since the variable star observing program was established at the Harvard College Observatory in the 19th Century.  Many of our overseas observers are members of other local variable star organizations, and submit data to their local organization in addition to submitting directly to the AAVSO.  The AAVSO has an agreement in place to receive monthly reports from the Association Française des Observateurs d'Étoiles Variables (AFOEV) to receive copies of their data, and so the AAVSO database can be considered a superset of the AFOEV database.  We have now also received a copy of the historical archives of the Royal Astronomical Society of New Zealand (RASNZ) and are in the process of adding these data to the AID.  A similar agreement is in place to mirror the British Astronomical Association -- Variable Star Section (BAAVSS) observations as well. All data from different organizations are labeled as such, and observers are now able to identify themselves as members of the AAVSO or other organizations.  This identification is included in the data you download.

Data summary: AAVSO data holdings by variable star type

For the purposes of this summary, we assume that a light curve is "well-observed" if the AAVSO light curve has at least 1000 visual observations.  Variable star classifications are those found in the AAVSO International Variable Star Index, VSX.  Data span is the time between the first and the last recorded observation.  You can obtain light curves for individual stars through our data search page.

Mira, semiregular, and long-period variables

Mira variables:  The AAVSO has 549 light curves of Mira variables with 1000 data points or more.  Two thirds of these -- 365 light curves of individual stars -- span 90 years or longer.  (For an example of how these data have been used, see Templeton, Mattei, and Willson, 2005, AJ 130, 776.)

Semiregular variables: The AAVSO has 243 well observed visual lightcurves of stars classified as semiregulars (SR) of all types. These are further broken down as follows: SRa -- 40 stars; SRb -- 134 stars; SRc -- 28 stars; SRd -- 19 stars.  Most SRa/b light curves span 60 years or more.  Of particular note is the light curve of miu Cep, for which we have over 160 years of data.

Long-period (irregular) variables: The AAVSO has 48 well observed visual light curves of stars classified as L or an L subtype: L -- 2 stars; LB -- 32 stars; LC -- 14 stars.  The spans of these light curves vary, but most are longer than 30 years.

Cataclysmic variables

U Geminorum stars (dwarf novae): The AAVSO has 232 well observed visual light curves for stars of type UG or UG-subtypes (UGSS, UGSU, UGZ, or UGWZ).  Light curves for these stars are typically much shorter than LPVs because (a) they are typically fainter, and (b) their observation was not specifically encouraged until the 1960s. More than half of these light curves span less than 30 years.  Some notable light curves include: SS Cyg (106 years); SS Aur (102 years); U Gem (102 years); X Leo (89 years); RX And (87 years); Z Cam (86 years); CN Ori (79 years); UV Per (76 years); SU UMa (75 years); and AY Lyr (74 years).

Novae (all types): The AAVSO has 84 well observed visual light curves for novae of all types (A, B, C, and R).  Notable light curves include: GK Per/N Per 1901 (110 years); RS Oph (95 years); V603 Aql/N Aql 1918 (91 years); T Pyx (89 years); and RR Tel/N Tel 1948 (87 years).

Novalikes (NL or NL/VY): The AAVSO has 16 well observed visual light curves for novalike and VY Sculptoris stars.  All span 15 to 45 years, although most are longer than 20 years.

Symbiotic stars (ZAND): The AAVSO has 30 well observed light curves for symbiotic stars of the Z Andromedae-type.  The light curves span from 16 to 97 years, with eight spanning 50 years or more: Z And (97 years), CH Cyg (82 years), AX Per (70 years), BF Cyg (68 years), AG Peg (68 years), EG And (56 years), WY Vel (56 years), and SY Mus (55 years).

Other notable types

RV Tauri stars: The AAVSO has 24 well obsrved visual light curves of RV Tauri stars.  Most are between 30 and 75 years in length, with three spanning more than 100 years: R Sct, R Sge, and V Vul.

R Coronae Borealis stars: The AAVSO has 29 well observed visual light curves of R CrB stars.  Of these, 13 light curves span 50 years or longer.  Notable light curves include those for RY Sgr, SU Tau, and R CrB, the latter of which is one of the best-observed stars in the AID.

T Tauri stars: The AAVSO has 10 well observed visual light curves of T Tauri (INT) stars, including S CrA (112 years), RY Tau (95 years), T Tau (94 years), RW Aur (73 years) and RU Lup (57 years).