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AAVSO SPP Program

The AAVSO SPP program includes a number of RR Lyrae stars and a few delta Scutid stars with large amplitudes, although data on any short period pulsating star can be submitted to the AAVSO International Database.  These stars typically have a small range, often less than one magnitude, so CCD observations are preferred over visual ones.  CCD observations should be through a standard filter to allow data sets to be merged together, and to minimize the effects due to the color changes these stars undergo during the pulsation cycle.  Many Cepheid stars are quite bright and photometry with a digital SLR or even a webcam is practical.  Refer to the information on DSLR photometry on the Citizen Sky site for more information.

RR Lyrae Ephemeris

Each year the AAVSO SPP Section issues a month-by-month prediction of times of maximum (ToMx) for selected RR Lyrae and large-amplitude delta Scuti stars.  This document lists times when each star will be at its maximum brightness.  (Hint:  to save these to your local system right-click and choose "Save link as")

RR Lyrae Ephemeris 2018
RR Lyrae Ephemeris 2017
RR Lyrae Ephemeris 2016
RR Lyrae Ephemeris 2015
RR Lyrae Ephemeris 2014
RR Lyrae Ephemeris 2013

RR Lyrae Ephemeris Generator

In addition to the PDF ephemeris above, an online ephemeris generator for RR Lyrae and delta Scuti stars is available.  This site allows the user to input their location and select a magnitude range, and generates a nightly list of stars that can be observed at the selected site.

Program Stars

The Table 1 lists some RR Lyrae stars that exhibit the Blahzko effect as well as some large-amplitude delta Scuti stars that have multiple periods. These stars should be observed several times every few seasons, at all phases (not just during maximum) to look for changes in the primary and Blazhko periods. The light curves for the multi-periodic delta Scuti stars are complex and vary markedly from cycle to cycle.  The RR Lyrae and delta Scuti stars in Table 2 appear to have single, stable periods without any Blazhko effect.  These need "time of maximum" (ToMx) measurements every few years to check for any changes in period that may occur.  Table 3 shows interesting Cepheid stars that have been observed by SPP section members.  Like the stars in Table 2, measuring the time of maximum should be done every few years for these stars.

Table 1 - RR Lyrae stars showing Blazhko effect, and multi-periodic delta Scuti stars

Variable

Type

Period (days)

Blazhko (days)

Notes

SW And

RRab

0.4423

36.8

 

AC And

RR

 

 

Has 2 or 3 periods

RS Boo

RRab

0.3773

533

 

ST Boo

RRab

0.6223

284

 

SW Boo

RRab

0.5136

13

 

TV Boo

RRc

0.3126

33.5

 

RW Cnc

RRab

0.5472

87

 

TT Cnc

RRab

0.5634

89

 

XZ Cyg

RRab

0.4666

57.3

 

DM Cyg

RRab

0.4199

26

 

RW Dra

RRab

0.4429

41.6

 

XZ Dra

RRab

0.4765

76

 

RR Gem

RRab

0.3973

37

 

AR Her

RRab

0.4700

31.6

 

DL Her

RRab

0.5916

33.6

 

SZ Hya

RRd

0.5372

25.8

Dual mode

VX Hya

Delta Sct

2 periods

 

Has a strong beat period between the two periods

RZ Lyr

RRab

0.5112

116.7

 

RV UMa

RRab

0.4681

90.1

 

Note: because the behavior of AC And and VX Hya are so irregular, these stars do not appear in the AAVSO Ephemeris.

Table 2 - Non-Blazhko RR Lyrae stars and large-amplitude delta Scuti stars

Variable

Type

Period (days)

Notes

XX And

RRab

0.7228

 

AT And

RRab

0.6169

 

SW Aqr

RRab

0.4593

 

TZ Aur

RRab

0.3917

 

BH Aur

RRab

0.4561

 

SZ Boo

RRab

0.5228

 

TW Boo

RRab

0.5323

 

UU Boo

RRab

0.4569

 

UY Boo

RRab

0.6510

 

RR Cet

RRab

0.5530

 

TW Her

RRab

0.3996

 

VX Her

RRab

0.4554

 

DY Her

Delta Sct

0.1486

 

UU Hya

RRab

0.5239

 

DG Hya

RRab

0.7542

 

DH Hya

RRab

0.4890

 

RR Leo

RRab

0.4524

 

SS Leo

RRab

0.6263

 

TV Leo

RRab

0.6729

 

WW Leo

RRab

0.6029

 

SZ Lyn

Delta Sct

0.1205

Part of a binary system.

AV Peg

RRab

0.3904

 

Table 3 - Target Cepheids

Star Name

Magnitude Range

Period (days)

Comment / Reference

Polaris (alpha UMi)

1.97 - 2.00

3.97

Amplitude has shrunk to almost zero in the last several decades but appears to be increasing now

beta Dor

3.46 – 4.08

9.843

 

T Mon

5.58 – 6.62

27.025

JAAVSO 4:84 (Landis 1975)

RT Aur

5.00 – 5.82

3.728

 

zeta Gem

3.62 – 4.18

10.151

 

ASAS182612

11.51 – 11.98

4.151

Eclipsing Cepheid; AAVSO Alert Notice #351

FF Aql

5.18 – 5.68

4.471

 

TT Aql

6.46 – 7.7

13.755

JAAVSO 4: 84 (Landis 1975)

U Aql

6.08 – 6.86

7.024

 

eta Aql

3.48 – 4.39

7.177

 

TW Cap

9.95 – 11.28

28.61

W Virginis type; JAAVSO, 10: 66 (DeYoung 1981)

delta Cep AB

3.48 – 4.37

5.366

Cepheid Prototype

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484