Friday, August 11, 2017

studied HD 38

Probed HD 38 aka STT 547 a bit deeper.

Pulled data from the Washington Double Star database for 00057+4549STT 547. Very interesting. Way beyond what is shown in my favourite software.

discoverer first obs last obs P.A. sep mag pri mag sec spectral
STT 547AB 1876 2016 189 6 8.98 9.15 K6+M0
STT 547AC 1911 2015 263 116.2 8.98 13.71 K6
STT 547AD 1911 2015 230 110.3 8.98 12.51 K6
STT 547AE 1911 2015 344 58.4 8.98 11.75 K6
STT 547AF 1897 2007 254 327.9 8.98 10.19 K6V+M2e
POP 217AP 1994 2015 320 15.4 8.98 13.4 K6
POP 217AQ 1998 2006 130 20 8.98 16 K6
POP 217AX 2004 2006 222 12 8.98 K6
POP 217AY 1998 2005 79 199 8.98 14.8 K6
STT 547BC 1925 2015 266 114.8 9.15 13.71 M0
STT 547BD 1921 2015 232 105.9 9.15 12.51 M0
STT 547BE 1991 2015 346 64 9.15 11.75 M0
STT 547BF 1961 2002 255 326.4 9.15 10.19 M0
STT 547BP 1989 2015 333 19.8 9.15 13.1 M0
POP 217YG 1998 2005 189 10 14.8 15.8

I transcribed the data from SkyTools 3 Professional.

AB 190 5.89
AC 356 54.5
AD 188 82.2
AF 268 84.52

Now, ST3P shows binary data information... The calculated values as of June 2017. AB has a 1551 year period. AF has a 83000 year period! Wow.

I flipped, zoomed, and cropped the image.

cropped flipped image of HD 38

North is up; east is right (opposite the full image).

I plotted in my custom Excel workbook the A through F stars using the WDS data. There is good correspondence to my BGO image.

plot of HD 38 A or STT 547

North is up; east is right.

I noted that the labelling between the WDS and ST3P was different. What ST3P called the C star, WDS said was E. What ST3P called star GSC 03246-1561 is C according to the WDS. From the BGO photo, I knew there was an issue with F. The WDS refers to a bright star which ST3P says is J000511.7+454706.

This means that for my log notes, I can claim to have spotted B, C, D, E, and F, according to the WDS. I have to adjust some notes from the initial observations. C is nearly due west of AB. It is extremely faint. It appears to me to be beside another star making it a pair (opposed or at a 90° angle to AB) with nearly the same separation as AB. E is to the north, about half the separation has C. F is far afield to the west.

plot of POP 217 stars

The WDS shows observations from POP. I plotted the stars POP 217 P, Q, X, and Y. I added the STT 547 F star to maintain the scale in the graph.

P corresponds to the image quite well. It is the medium-bright nearby star to the north-north-west. ST3P calls this GSC 03246-0320. I don't see anything at the Q location. Nor the X spot. Q is listed as mag 16; X has no value. The Y star however lines up with my image with a faint star. In fact, it too seems to be part of a faint double. Their alignment is almost identical to AB, roughly north-south. It is to the east, well away. In ST3P, this is shown as J000600.2+454920 at mag 14.8.

So I think I can safely add the P and Y stars to my life list log.

plot HD 38 B proper

The WDS catalogue lists C, D, E, F, and P associated with B. I plotted this system. Again I see a very good correlation to my image.

There's another POP 217 entry, this time for the G partner to Y. It is at position angle 189 and is 10 arc-seconds away. I see this in my image. This star is south of Y and fainter. And ST3P shows this too: GSC 03246-1853. I think I can add the G star to my log.

For clarity, I annotated the photograph.

photo of HD 38 with annotations


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