Observations of the SX Observations of the SX Phoenicis Star XX CygniPhoenicis Star XX Cygni

X.H. YangX.H. Yang

Beijing Normal UniversityBeijing Normal University

2010.4.12010.4.1

ContentsContents

Introduction of the SX Phe starsIntroduction of the SX Phe stars New observationsNew observations Data reductionData reduction Light curvesLight curves AnalysisAnalysis ConclusionsConclusions

IntroductionIntroductionδ Scuti Stars:

1.The SX Phoneicis stars

2.High-amplitude δ Scuti Stars (HADS)

Period changes:

Period increasing and period decreasing were detected in different

δ Scuti Stars

The SX Phoenicis stars:The SX Phoenicis stars: Found in the field starsFound in the field stars Found in the blue straggler populations of Found in the blue straggler populations of

globular clustersglobular clusters short-periodshort-period Single- or multiple-mode pulsationsSingle- or multiple-mode pulsations

Importance of studying SX Phe starsImportance of studying SX Phe stars

1.Studying stellar evolution1.Studying stellar evolution

2. Potential targets for Asterseismology2. Potential targets for Asterseismology

XX Cygni:XX Cygni:

2020hh0303mm15.6 58°5715.6 58°57''17.017.0""

Spectral type: A5-F5,Spectral type: A5-F5,

VV=11.=11.mm7, P≈0.7, P≈0.dd1349, V=0.△1349, V=0.△ mm8484

Mass:1 Msun [Fe/H]=-0.49 dexMass:1 Msun [Fe/H]=-0.49 dex TTeffeff: 7530 K Radial Velocity=-108 km/s: 7530 K Radial Velocity=-108 km/s

Discovered by Ceraski (1904)Discovered by Ceraski (1904) Constant period, marked by occasional discontinuous Constant period, marked by occasional discontinuous

period changes (Szeidl & Mahdy 1981)period changes (Szeidl & Mahdy 1981) Single-mode pulsation (Hintz & Joner1997)Single-mode pulsation (Hintz & Joner1997) Both amplitude and period changes (Zhou et al. 2001)Both amplitude and period changes (Zhou et al. 2001) If the small secondary peak(maximum) is real,it is If the small secondary peak(maximum) is real,it is

transient (Blake 2002)transient (Blake 2002)

The secondary peak or maximumThe secondary peak or maximum

From BLAKE

Period Changes in SX Phoenicis Stars. II. XX Cygni

New observationsNew observations Telescope used in observationsTelescope used in observations 1. The 85-cm telescope located at the Xinglong Station 1. The 85-cm telescope located at the Xinglong Station

of NAOCof NAOC

Focal ratio: 3.27 ;Focal ratio: 3.27 ; Focal length: 2780mmFocal length: 2780mm

CCD camera: CCD,PI1024 BFTCCD camera: CCD,PI1024 BFT

Filters: Standard Johnson-Cousin-Bessel Filters: Standard Johnson-Cousin-Bessel UBVRIUBVRI

Field of view: 16Field of view: 16’’.5×16.5×16’’.5.5

2.The 60-cm telescope located in Kunming (Yunnan 2.The 60-cm telescope located in Kunming (Yunnan Astronomical Observatory)Astronomical Observatory)

Journal of new observations in Journal of new observations in VV band for XX Cyg band for XX Cyg

YearYear DateDate TelescopeTelescope FramesFrames

20072007 07.1507.15 85-cm85-cm 4242

07.1807.18 218218

07.1907.19 108108

07.2207.22 374374

07.2307.23 364364

08.1708.17 677677

08.1908.19 5757

08.2208.22 229229

08.2308.23 639639

08.2408.24 13081308

YearYear DateDate TelescopeTelescope FramesFrames

20072007 08.2708.27 85cm85cm 10691069

08.2908.29 260260

08.3008.30 992992

20082008 08.3108.31 85cm85cm 488488

20092009 07.0907.09 85cm85cm 770770

08.1108.11 684684

08.1208.12 771771

08.1308.13 472472

08.2208.22 60cm60cm 140140

08.2308.23 6565

08.2508.25 137137

YearYear DateDate TelescopeTelescope FramesFrames

20092009 10.1310.13 85-cm85-cm 830830

10.1410.14 720720

10.1710.17 598598

Totally, 24 nights of data in Totally, 24 nights of data in VV band band

Data ReductionData Reduction

Data reduction was performed using the Data reduction was performed using the APPHOT program in IRAF:APPHOT program in IRAF:

1.Bias and Dark correction, Flat fielding1.Bias and Dark correction, Flat fielding

2.Multiple aperture photometry2.Multiple aperture photometry

3.Determination of the best aperture3.Determination of the best aperture

Example of the best aperture selected:Example of the best aperture selected:

FWHM:

4 pixel

Field of view:

16’.5*16’.5

Xinglong

Light CurvesLight Curves2007

07.15-08.30

Xinglong 85cm

Error:

0.004-0.02

2008.08.2008.08.3131

XinglongXinglong

Error:Error:

0.0030.003

2009200907.0907.09-10.17-10.17XinglongXinglong

Error:Error:0.003-0.020.003-0.02KunmingKunming

60cm

Kunming

Observed new times of maximum: 37Observed new times of maximum: 37

AnalysisAnalysis

Fourier analysis:Fourier analysis:

Software: Period04

Data set: 2007.08

8 nights of observations

Frequency (dFrequency (d-1-1)) Amplitude (mmag)Amplitude (mmag) S/NS/N

ff00 7.415687.41568 343.9343.9 201.1201.1

2 f2 f00 14.8304414.83044 151.6151.6 177.7177.7

3 f3 f00 22.2466322.24663 75.675.6 122.1122.1

4 f4 f00 29.6606029.66060 38.938.9 64.864.8

5 f5 f00 37.0770137.07701 22.322.3 54.954.9

6 f6 f00 44.4924744.49247 17.517.5 47.847.8

7 f7 f00 51.9082951.90829 12.212.2 40.340.3

8 f8 f00 59.3204759.32047 9.09.0 27.727.7

9 f9 f00 66.7372766.73727 6.56.5 24.824.8

10 f10 f00 74.1538074.15380 5.45.4 13.113.1

Frequency solutions of XX Frequency solutions of XX CygCyg

Fitting curvesFitting curves

ConclusionsConclusions

No secondary peaks were found in our data.No secondary peaks were found in our data.

Next work:Next work: O-C analysis O-C analysis Period change analysisPeriod change analysis