watchingthesky16
My high proper motion star discovery May 4, 2010
This was on my prior flickr page which had to be deleted due to security issues. The photo has been revised as well as some of the text.
Quite by chance I stumbled upon a previously unrecognized high proper motion star (arrowed = GSC 1431-0607) while observing some galaxies in Leo on the night of May 4, 2010. I was using a chart printed from the software RealSky. This software uses the POSS1 red images from a survey done in the 1950's.
After following a chain of stars from a magnitude 6.5 star (not shown in above image) and including the galaxies MCG+3-28-2 and CGCG 95-8, I moved west at 182x with my 17.5-inch Dobsonian to what I thought was a single star as I headed to my next target. To my amazement, there was a very nice double star. It was easy to see with components of some 12th and 13th magnitudes. The pair was oriented east to west with the western star being the fainter of the two.
My initial thought was the fainter object must be an asteroid moving through the field. That did not turn out to be the case. My next thought was a variable star.
I posted about this object on the amastro yahoo group. Astronomer Brian Skiff of Lowell Observatory suggested this was actually a star which had merged with the image of the brighter star to its east when the POSS1 survey was made. He subsequently did some research and was able to confirm his hypothesis. with 0.322” per year in right ascension and 0.003” per year in declination. Meanwhile, after reading his suggestion I did some research of my own and came to the same conclusion with overall motion 0.329” per year from averaging what was determined from POSS1, POSS2, and SDSS images.
At the time we disagreed on the visual brightness of this star. From my visual observation I believe it had to have been in between magnitudes 13.0 and 14.0. The data Skiff located says more like 14.8. At the time what images I had taken suggested it was about 14.0. However, for this 2018 update using three comparison stars from APASS for the image above it measured 14.75V +/- 0.01. This is close to the actual APASS measurement of 14.71V and what Skiff had originally stated. Even so I wondered if there was some variability.
With the new ASAS-SN data release I input the coordinates of the star in their form. It came back showing variation from 13.85 to 14.05. However, that is far too bright and may be contaminated by the star to the east.
CRTS also covers the field. Their data shows the star to be probably constant around 14.1 as nearly all, but two points, are within error. Their data normally has red stars brighter as they used unfiltered images for cameras which tend to be red sensitive. As for the star to the east it averages 13.3; however, the light curve does suggest some possible irregular variation of about 0.1 magnitude. There are a few points outside that, but these may be spurious data.
Speculation is this star is a K5 to M0 dwarf and may be some 150 to 200 parsecs distant. However, there is also a suggestion it could be a class M subdwarf. That would make it much closer and its transverse velocity more reasonable.
Update June 6, 2018.
1. Gaia DR2 confirms the proper motion as RA of 319.88 mas/yr to the west and 18.80 mas/yr to the south in declination.
2. Gaia DR2 also has a parallax of 5.4594 mas which corresponds to a distance of 183 parsecs.
3. Current Gaia position is RA = 10h43m56.17s, Decl = 18d31m47.97s.
Update April 28, 2021. The yahoo group amastro has moved to a new host. The thread is now: groups.io/g/amastro/topic/51299931#22841
Update March 11, 2023
Current Gaia data has a distance of 182 parsecs. With an apparent magnitude of 14.75V that puts its absolute magnitude at 8.45V. That is slightly fainter than 61 Cygni B which is 8.31V and spectral type K7.0V. Comparing that to another nearby star that is type M0V that suggests this star is about K8.0V.
My high proper motion star discovery May 4, 2010
This was on my prior flickr page which had to be deleted due to security issues. The photo has been revised as well as some of the text.
Quite by chance I stumbled upon a previously unrecognized high proper motion star (arrowed = GSC 1431-0607) while observing some galaxies in Leo on the night of May 4, 2010. I was using a chart printed from the software RealSky. This software uses the POSS1 red images from a survey done in the 1950's.
After following a chain of stars from a magnitude 6.5 star (not shown in above image) and including the galaxies MCG+3-28-2 and CGCG 95-8, I moved west at 182x with my 17.5-inch Dobsonian to what I thought was a single star as I headed to my next target. To my amazement, there was a very nice double star. It was easy to see with components of some 12th and 13th magnitudes. The pair was oriented east to west with the western star being the fainter of the two.
My initial thought was the fainter object must be an asteroid moving through the field. That did not turn out to be the case. My next thought was a variable star.
I posted about this object on the amastro yahoo group. Astronomer Brian Skiff of Lowell Observatory suggested this was actually a star which had merged with the image of the brighter star to its east when the POSS1 survey was made. He subsequently did some research and was able to confirm his hypothesis. with 0.322” per year in right ascension and 0.003” per year in declination. Meanwhile, after reading his suggestion I did some research of my own and came to the same conclusion with overall motion 0.329” per year from averaging what was determined from POSS1, POSS2, and SDSS images.
At the time we disagreed on the visual brightness of this star. From my visual observation I believe it had to have been in between magnitudes 13.0 and 14.0. The data Skiff located says more like 14.8. At the time what images I had taken suggested it was about 14.0. However, for this 2018 update using three comparison stars from APASS for the image above it measured 14.75V +/- 0.01. This is close to the actual APASS measurement of 14.71V and what Skiff had originally stated. Even so I wondered if there was some variability.
With the new ASAS-SN data release I input the coordinates of the star in their form. It came back showing variation from 13.85 to 14.05. However, that is far too bright and may be contaminated by the star to the east.
CRTS also covers the field. Their data shows the star to be probably constant around 14.1 as nearly all, but two points, are within error. Their data normally has red stars brighter as they used unfiltered images for cameras which tend to be red sensitive. As for the star to the east it averages 13.3; however, the light curve does suggest some possible irregular variation of about 0.1 magnitude. There are a few points outside that, but these may be spurious data.
Speculation is this star is a K5 to M0 dwarf and may be some 150 to 200 parsecs distant. However, there is also a suggestion it could be a class M subdwarf. That would make it much closer and its transverse velocity more reasonable.
Update June 6, 2018.
1. Gaia DR2 confirms the proper motion as RA of 319.88 mas/yr to the west and 18.80 mas/yr to the south in declination.
2. Gaia DR2 also has a parallax of 5.4594 mas which corresponds to a distance of 183 parsecs.
3. Current Gaia position is RA = 10h43m56.17s, Decl = 18d31m47.97s.
Update April 28, 2021. The yahoo group amastro has moved to a new host. The thread is now: groups.io/g/amastro/topic/51299931#22841
Update March 11, 2023
Current Gaia data has a distance of 182 parsecs. With an apparent magnitude of 14.75V that puts its absolute magnitude at 8.45V. That is slightly fainter than 61 Cygni B which is 8.31V and spectral type K7.0V. Comparing that to another nearby star that is type M0V that suggests this star is about K8.0V.