SECULAR AND STATISTICAL PARALLAXCALEB ABBOTT

Our Journey Today:Basic Technique

Measurable Range

Potential Problems

Error

Examples in Literature

Step 1:

Pick stars that are likely to be the same distance away (type, luminosity, etc.)

To be able to make use of radial velocities, to determine relative Solar motion, the sample of stars needs to be randomly distributed around the sky.

Step 1:

Select a group of stars with common parameters

Obtain the Sun’s relative motion (radial velocities)

Step 2:

Determine the components of the star’s proper motion (𝜐 and 𝞃)

Requires position angle, declination, and the proper motion in both RA and Dec

Step 3:

Use statistics (“averages”) to get a mean parallax for stars in that group

Step 4:

Profit?

BASIC TECHNIQUESA STEP-BY-STEP GUIDE TO “SUCCESS” Turner, Odessa Astronomical Publications, vol. 25/1

(2012)

Step 2:

𝜐 and 𝞃 reflect on the Solar motion and the star’s spatial motion respectively

𝞃 should be randomly distributed

can be calculated with the RA and Dec Components of proper motion

BASIC TECHNIQUESA STEP-BY-STEP GUIDE TO “SUCCESS” Turner, Odessa Astronomical Publications, vol. 25/1

(2012)

Step 2: Determine components

Turner, Odessa Astronomical Publications, vol. 25/1 (2012)

Step 3: Calculate Parallax

Secular parallax —>

Better for when Solar motion dominates

Statistical parallax —>

Can obtain reasonable results out to ~500 pc

Turner, Odessa Astronomical Publications, vol. 25/1 (2012)

Bonney & Merrifield

Step 4: Profit Problems and Errors

Selecting stars likely to be near the same distance

Determining relative Solar motion

Measuring proper motions

Outdated?

Bonney & Merrifield

Hakkila (1990)

Used secular parallaxes to determine distances (and therefore absolute magnitudes) of Barium Stars.

Hakkila, Astrophysical Journal, Volume 100 Number 6 (1990)

HAKKILA (1990)PARALLAX OF BARIUM STARS Hakkila, Astrophysical Journal, Volume 100 Number 6

(1990)

J.H.J. de Bruijne et al (2000)

“A Hipparcos study of the Hyades open cluster”

Improved the distances provided by trig. parallax by ~3 times

Being that the proper motion is better constrained

de Bruijne et al, Astronomy and Astrophysics (2000)

J.H.J DE BRUIJNE (2000)IMPROVEMENTS TO THE PARALLAX de Bruijne et al, Astronomy and Astrophysics (2000)

THANK YOUQUESTIONS?