2009/03/18-202009/03/18-20 East Asia VLBI WorkshopEast Asia VLBI Workshop 11

Period-Luminosity Relation of Period-Luminosity Relation of Mira-Variables Revealed from Mira-Variables Revealed from

VLBIVLBI--- Parallax Measurement --- Parallax Measurement

Results around 500-Day Period Results around 500-Day Period with VLBAwith VLBA

East Asia VLBI WorkshopEast Asia VLBI Workshop

(Seoul, 2009 Mar 18-20)(Seoul, 2009 Mar 18-20)

Kurayama, Tomoharu (KVN/KASI)Kurayama, Tomoharu (KVN/KASI)*1*1

Matsui, Makoto (Kagoshima Univ.)Matsui, Makoto (Kagoshima Univ.)*1 Kagoshima Univ. from 2009 April*1 Kagoshima Univ. from 2009 April

2009/03/18-20 East Asia VLBI Workshop 2

Period-luminosity (PL) relation of Period-luminosity (PL) relation of Mira variablesMira variables

► Large Magellanic Cloud (LMC)Large Magellanic Cloud (LMC)

(Feast et al. 1989)(Feast et al. 1989)

► The red line is the fitting The red line is the fitting result from data whose result from data whose periods are less than 420 periods are less than 420 days.days.

(van Leeuwen et al. 1997)(van Leeuwen et al. 1997)

► Error bars are caused by Error bars are caused by the uncertainties of the uncertainties of HipparcosHipparcos’’ parallax ( 1 parallax ( 1 mas).mas).

-13

-11

-9

-7

-52 2.2 2.4 2.6 2.8 3

log(period/ day)ab

solu

te m

ag.

6

8

10

12

142 2.2 2.4 2.6 2.8 3

log(period/ day)

K-m

ag

Relationship in K-band Relationship in K-band (2.2μm)(2.2μm) ► Solar-neighbourhood (Hipparcos)Solar-neighbourhood (Hipparcos)

2009/03/18-20 East Asia VLBI Workshop 3

Why are the solar-neighbourhood Why are the solar-neighbourhood error and scatter large?error and scatter large?

► Large Magellanic Cloud Large Magellanic Cloud (LMC)(LMC)

► Solar-neighborhood Solar-neighborhood (Hipparcos)(Hipparcos)

► Distance >> Distance >> distributiondistribution

► Distance to all Miras Distance to all Miras are sameare same

► .constmagnitude

absolute

magnitude

apparent

► Distance = distributionDistance = distribution► We must calculate We must calculate

absolute magnitude absolute magnitude using distances.using distances.

LMLMCC

2009/03/18-20 East Asia VLBI Workshop 4

Scientific targetScientific target

► Uncertainties in PL relation of solar-Uncertainties in PL relation of solar-neighborhood Miras are large.neighborhood Miras are large.

► When we measure the parallaxes (that is, When we measure the parallaxes (that is, distances) of Miras and establish the relationship distances) of Miras and establish the relationship between periods and absolute luminosities,between periods and absolute luminosities, PL relation of Miras becomes an absolute distance PL relation of Miras becomes an absolute distance

indicator,indicator, we can measure the distance to the LMC, andwe can measure the distance to the LMC, and it is possible to measure the Galactic structure using it is possible to measure the Galactic structure using

Miras as probes.Miras as probes.► We carried out phase-referencing VLBI We carried out phase-referencing VLBI

observations in order to measure the parallaxes.observations in order to measure the parallaxes.

2009/03/18-20 East Asia VLBI Workshop 5

ObservationObservation► VLBA 10 stationsVLBA 10 stations► 22 GHz 22 GHz

(water maser)(water maser)► 5 hours 4 days5 hours 4 days► Bandwidth : 16 MHzBandwidth : 16 MHz► Velocity resolution :Velocity resolution :

0.2 km/s0.2 km/s► Recording rate : Recording rate :

128 Mbps (32 Msps×2 bit×2 ch)128 Mbps (32 Msps×2 bit×2 ch)(VLBA Home Page)

Mira antenna slewing referenceantenna slewing Mira

7 sec 13 sec 7 sec 13 sec 7 sec

40 sec

2009/03/18-20 East Asia VLBI Workshop 6

Observed sourcesObserved sources

Miras Reference for

phase-ref Period [days]

Observed dates

VX UMa J1048+7143 (quasar) 215

2001 Jan 27 2001 April 13

2001 Jan 28 2001 Jun 28

RT Aql J1938+0942

327 2001 May 13 2001 Aug 13

2001 Jun 20 2001 Sep 10

R Cas 2352+495 (Seyfert galaxy) 430

2002 Mar 30 2002 May 23

2002 Apr 25 2002 Jun 25

UX Cyg J2050+3127 (quasar) 565

2001 Feb 22 2001 Nov 11

2001 Oct 12 2002 Feb 04

AW Tau J0547+2721 (extragalactic) 654

2001 Jan 23 2001 Apr 03

2001 Mar 03 2001 Jun 04

(GCVS : General Catalogue of Variable Stars)

2009/03/18-20 East Asia VLBI Workshop

► Parallax : 0.54 0.06 Parallax : 0.54 0.06 masmas

► Distance :Distance :

kpc85.1 25.019.0

AB C

DE

F

G

AB C

DE

F

G

AB C

D

E

F

G

AB C

D

E

F

G

Results of UX CygniResults of UX Cygni

7

(Kurayama et al. 2005)

Parallax of VX UMa Parallax of VX UMa (Preliminary)(Preliminary)

►Movement on the Movement on the skysky Blue : ObservedBlue : Observed Pink : FittedPink : Fitted

►Parallax :Parallax : 0.4 0.1 mas0.4 0.1 mas

2009/03/18-20 East Asia VLBI Workshop 8

- 8

-6

-4

-2

0

2

-2024

dec

offse

t [m

as]

RA offset [mas]

2009/03/18-20 East Asia VLBI Workshop 9

Overlapping to Previous PL Overlapping to Previous PL relationsrelations

► PL relation of Large Magellanic CloudPL relation of Large Magellanic Cloud

(Assuming the distance modulus of the LMC is 18.50.)

8

9

10

11

12

13

2 2.2 2.4 2.6 2.8 3

K-m

ag

log(period/day)

VX UMaUX Cyg

(Feast et al. 1989)

Period of VX UMaPeriod of VX UMa

► In GCVS (General In GCVS (General Catalogue of Catalogue of Variable Stars) : Variable Stars) : 215.2 days215.2 days

► Correct one Correct one Carter 1993, J. Carter 1993, J.

AAVSO, 22, 69AAVSO, 22, 69 R band : 520 daysR band : 520 days V band : 507 daysV band : 507 days Uncertainty : Uncertainty :

around 10 daysaround 10 days

2009/03/18-20 East Asia VLBI Workshop 10

(from AAVSO homepage)

R

I

VVisualB

Relative date [days]200 4000

Mag

.

4

18

8

14

2009/03/18-20 East Asia VLBI Workshop 11

Overlapping to Previous PL Overlapping to Previous PL relationsrelations

► PL relation of Large Magellanic CloudPL relation of Large Magellanic Cloud

(Assuming the distance modulus of the LMC is 18.50.)

8

9

10

11

12

13

2 2.2 2.4 2.6 2.8 3

K-m

ag

log(period/day)

VX UMaUX Cyg

(Feast et al. 1989)

Overlapping to Previous PL Overlapping to Previous PL RelationsRelations

► Slightly above (bright) from overall resultsSlightly above (bright) from overall results

2009/03/18-20 East Asia VLBI Workshop 12

UX Cyg

VX UMa

-6

-8

-10

2 2.82.62.42.2log (period/day)

Ab

solu

te

mag

.

(Whitelock et al. 2008)

Black : Hipparcos parallaxesBlue : globular clusterRed : VLBI parallaxes

► Solar-neighbourhoodSolar-neighbourhood

Why Are Our Results Slightly Why Are Our Results Slightly Bright?Bright?

► Physical processes Physical processes of Mira variables?of Mira variables? Different sequence?Different sequence? Hot bottom Hot bottom

burning?burning?► Systematical error Systematical error

in parallaxes?in parallaxes? VERA results are VERA results are

slightly fainter. slightly fainter. (Nakagawa-san’s (Nakagawa-san’s talk)talk)

VERA also observes VERA also observes VX UMa.VX UMa.

2009/03/18-20 East Asia VLBI Workshop 13

–1 1 3log P [days]

10

17

K

(Ita et al. 2004)

SummarySummary► Two parallaxes of Mira variables are Two parallaxes of Mira variables are

measured with VLBA.measured with VLBA. UX Cyg : 0.54 0.06 masUX Cyg : 0.54 0.06 mas VX UMa :VX UMa : 0.4 0.1 mas0.4 0.1 mas

► The period of VX UMa was wrong.The period of VX UMa was wrong. 215.5 days –> 507 – 520 days215.5 days –> 507 – 520 days

► Two Miras are plotted on period-luminosity Two Miras are plotted on period-luminosity relation.relation. Not so big differenceNot so big difference Slightly brighter than PL relation by other Slightly brighter than PL relation by other

methodsmethods► We need confirmation works…We need confirmation works…2009/03/18-20 East Asia VLBI Workshop 14

Thank you!Thank you!

2009/03/18-20 East Asia VLBI Workshop 15

2009/03/18-20 East Asia VLBI Workshop 16

50 mas