Docstoc

相対 VLBI 観測によるミラ型変光星 UX Cygni の年周視差測定

Document Sample
相対 VLBI 観測によるミラ型変光星 UX Cygni の年周視差測定 Powered By Docstoc
					  Parallax measurements of the
  Mira-type star UX Cygni with
     phase-referencing VLBI
                8th European VLBI Network Symposium
                       (Toruń, Poland, 2006 Sep 26-29)

                     Tomoharu Kurayama
         (National Astronomical Observatory of Japan)
2006.09.25-29               8th EVN Symposium            1
    Period-luminosity (PL) relation of Mira
                  variables
                              Relationship in K-band (2.2μm)
►       Large Magellanic Cloud (LMC)                                  ►               Solar-neighbourhood (Hipparcos)
          6                                                                           -13

          8                                                                           -11
K-mag




                                                                      absolute mag.
        10                                                                            -9

        12                                                                            -7

        14                                                                            -5
              2         2.2     2.4      2.6       2.8       3                              2   2.2     2.4      2.6    2.8        3
                              log(period/day)                                                         log(period/day)
                                                (Feast et al. 1989)                                        (van Leeuwen et al. 1997)

►        The red line is the fitting result                             ►              Error bars are caused by the
         from data whose periods are                                                   uncertainties of Hipparcos’
         less than 420 days.                                                           parallax ( 1 mas).
        2006.09.25-29                                     8th EVN Symposium                                                    2
             Why is the solar-neighbourhood
                      scatter large?
►    Large Magellanic Cloud            ►    Solar-neighborhood
     (LMC)                                  (Hipparcos)



                       LMC

►  Distance >> distribution               ► Distance = distribution
► Distance to all Miras are               ► We must calculate absolute
   same                                     magnitude using distances.
►  apparent   absolute 
  
   magnitude    magnitude   const .
                            
                           
    2006.09.25-29             8th EVN Symposium                     3
    Period-luminosity (PL) relation of Mira
                  variables
                              Relationship in K-band (2.2μm)
►       Large Magellanic Cloud (LMC)                                  ►               Solar-neighbourhood (Hipparcos)
          6                                                                           -13

          8                                                                           -11
K-mag




                                                                      absolute mag.
        10                                                                            -9

        12                                                                            -7

        14                                                                            -5
              2         2.2     2.4      2.6       2.8       3                              2   2.2     2.4      2.6    2.8        3
                              log(period/day)                                                         log(period/day)
                                                (Feast et al. 1989)                                        (van Leeuwen et al. 1997)

►        The red line is the fitting result                             ►              Error bars are caused by the
         from data whose periods are                                                   uncertainties of Hipparcos’
         less than 420 days.                                                           parallax ( 1 mas).
        2006.09.25-29                                     8th EVN Symposium                                                    4
                    Scientific target
► Uncertainties in PL relation of solar-neighborhood
  Miras are large.
► When we measure the parallaxes (that is,
  distances) of Miras and establish the relationship
  between periods and absolute luminosities,
        PL relation of Miras becomes an absolute distance
         indicator,
        we can measure the distance to the LMC, and
        it is possible to measure the Galactic structure using
         Miras as probes.
► We    carried out phase-referencing VLBI
     observations in order to measure the parallaxes.
2006.09.25-29                  8th EVN Symposium                  5
                           Observation
► VLBA 10          stations
► 22 GHz
  (water maser)
► 5 hours  4 days
► Bandwidth : 16 MHz
► Velocity resolution :
     0.2 km/s
► Recording rate :                                                (VLBA Home Page)
     128 Mbps (32 Msps×2 bit×2 ch)
           7 sec       13 sec            7 sec           13 sec   7 sec
            Mira   antenna slewing   reference antenna slewing     Mira

                                40 sec
2006.09.25-29                        8th EVN Symposium                          6
                     Observed sources
►    Mira variable : UX Cygni
                                       
           (α,δ)=(20h55m05.4s, +30 24’53’’)
                           
           (l,b)=(74.34 , -9.41)
          K-band magnitude : 1.96 mag (Feast & Whitelock 2000)
          Variation period : 565 days (GCVS)
          Total flux density : 24.83 Jy (Comoretto et al. 1990)
►    Reference source for phase-referencing : J2050+3127
        Redshift : 3.18 (Fey et al. 2001)
►                                     
     Separation angle of 2 sources : 1.38
►    Observed date : 2001 Feb 22, 2001 Oct 12,
                     2001 Nov 11, 2002 Feb 04

2006.09.25-29                     8th EVN Symposium                7
     Water masers around UX Cygni
                                                                20 mas




      2001 Feb 22         2001 Oct 13        2001 Nov 11 2002 Feb 04
                                       ►    Radial velocity : ► Synthesized
                                            -2.5 km/s           beam
                                                                     0.8 mas
                                       ►    The centres of all
                                            maps are same
         -20    -10     0    10   20        against the         175° 0.4 mas
                      [km/s]                reference source.
2006.09.25-29                      8th EVN Symposium                     8
                 Positions of all maser spots
►   Origins are fixed to
    the position of B on                             A
                                                                  E
                                                     B C                  A
    2001 Feb 22 (1st obs.).                             D                 B C        E
                                                                      G     D
                                                                                         G
VLA observation
                                                                  F              F
(Bowers et al. 1994)


                                                          A       E       A
                   Position of star                       B   C                      E
                                                                          B C
                                                              D
                                                                             D
                                                                      G                      G

                                                                  F                  F



 2006.09.25-29                        8th EVN Symposium                                      9
                    Fitting for parallax
►   Least square fitting with             ►    Fitted movements excluding
    the common parallax and                    linear motions and observed
    the linear motion of each                  positions
    maser spot.
       Total number of
        parameters : 29
       Total number of coordinate
        data : 54
►   Parallax : 0.54  0.06 mas
►   Disatnce : 1.850..25 kpc
                     0 19


    2006.09.25-29                    8th EVN Symposium                       10
                 Discussion 1 : Distance to LMC
                                             UX Cygni
                                             Distance : 1.850..25 kpc
                                                               0 19
                                             Apparent mag. :
                                                    1.96 mag
                                                                           Distance
                                             Absolute mag. :
                                                                           modulus to
                                                      9.37 0..24 mag     LMC :
        LMC                                 565 days
                                                             0 27
                                                                                  18.710..33
         6                                                                              0 31
         8                                                                 Distance to
                                                                           LMC :
K-mag




        10
                                                                                  55.19..0 kpc
                                                                                      7 2
        12
                                                      9.33     mag
                                                               0.19
        14                                                                 Typical value :
             2      2.2    2.4       2.6    2.8   3
                          log(period/day)                                         50 kpc
                              (Feast et al. 1989)                                   (Alves, 2004)
        2006.09.25-29                                  8th EVN Symposium                     11
                 Discussion 2 :
       Position and motion in the Galaxy

         ► Position                                       ► Motion
                                                                               For Galactic
                                                      204.03..6
                                                           3 4    km/s        centre
                 
     8.20 0.01 kpc
                         Galactic centre
                                                                          81.615 ..3 km/s
                                                                               14 0
0.300..03 kpc
     0 04
                                      1 7
                                12.41..3
                                     
                                                          UX Cygni            

        UX Cygni     The Sun                                  12.110 ..3 km/s
                                                                  
                                                                   10 2




                        Assuming R0  8.5 kpc、 0  220 km/s
                        Adopted proper motion is the average.

 2006.09.25-29                        8th EVN Symposium                                   12
                Summary and future
►   We carried out the water                      Parallaxes derived with VLBI
    maser observation around                     (Published from 1986 to 2006)
    the Mira-star UX Cygni with                              0.1
    phase-referencing VLBI.               This result
                    
     Parallax : 0.54 0.06 mas
                                                                                     30%
     Distance : 1.850..25 kpc
                      0 19                                                          uncertainty



                                            Parallax [mas]
                                                               1
►   This is the first parallax
    from water maser.                                              Pulsars
►   We would like to observe                                  10
                                                                   Stars
    more Mira variables with                                       Star formations
    VERA in the future.
    (some sources have been                                  100
    already observed)                                           0.01     0.1        1        10
2006.09.25-29                     8th EVN Symposium
                                                                       Uncertainty [mas]     13
                   Reference
► Kurayama,     T. et al. 2005, ApJ, 627, L49




2006.09.25-29         8th EVN Symposium         14
                        Discussion 1 : PL relation
                                  PL relation in K-band (2.2μm)
  ► Large                 Magellanic Cloud                    ► Solar-neighborhood
         6                                                                     -13
                                     This result                                                          This result
         8                                                                     -11
K-mag




                                                               absolute mag.
        10                                                                      -9

        12                                                                      -7

        14                                                                      -5
             2          2.2     2.4      2.6    2.8      3                           2   2.2     2.4      2.6    2.8        3
                              log(period/day)                                                  log(period/day)

  (Assuming the distance modulus of the
  LMC is 18.50.)
        2006.09.25-29                                 8th EVN Symposium                                                15

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:6
posted:4/29/2013
language:Unknown
pages:15