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The Sky's 25 Brightest White Dwarf Stars

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#1 SNH

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Posted 19 September 2023 - 04:41 PM

Well, I recently finished a research project that I had been wanting to get to for at least five years. I present a list of the sky's 25 brightest white dwarf stars arranged by brightness. It was harder than you might think because the line between a hot subdwarf and a white dwarf is a fine one. Plus, it seems to be hard to accurately measure the brightness of white dwarfs because of their peculiar spectrum.

 

I don't have much more to say than that. I hope a few people find it useful enough to try hunting some down. I've been going after them in binoculars since they're stellar with any instrument. I didn't include coordinates, but if you want those simply punch in one of the two designations listed into SIMBAD and voilĂ !

 

Download here: The Sky's 25 Brightest White Dwarf Stars

 

Scott H.

 

 

WDS.jpg


Edited by SNH, 19 September 2023 - 07:56 PM.

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#2 12BH7

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Posted 19 September 2023 - 06:51 PM

Thanks, downloaded and excited to find a few.



#3 timokarhula

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Posted Yesterday, 04:06 AM

Thanks Scott for the list.  Last week I observed the brightest solitary white dwarf in the northern sky with 25x100 binoculars, the 11.5 magnitude Wolf 1346 (HD340611) in Vulpecula.  It has a proper motion of 0.69 arc-seconds per year.  I compared its position with an image from the Digitized Sky Survey taken in 1956.  Its 46" movement was clearly evident.

 

/Timo Karhula


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#4 yuzameh

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Posted Yesterday, 08:56 AM

It was harder than you might think because the line between a hot subdwarf and a white dwarf is a fine one. Plus, it seems to be hard to accurately measure the brightness of white dwarfs because of their peculiar spectrum.

 

re brightness measure difficulties, that's mostly if you are using Johnson V.  In the past dedicated passbands have been used based more on the blue end continua or similar.  Sideway, O stars used to be measured most in Walraven photometric passbands.

 

Now, because you have a relatively bright faint limit it is possible to readily distinguish white dwarfs and hot blue subdwarfs with a very basic astrophysics arithmetic trick.

 

First, white dwarfs and subdwarfs are intrinsically faint in terms of absolute magnitude, but their faintnesses are quite distinct.

 

Second, as white dwarfs are intrinsically / inherently faint their absolute magnitudes is about your limit of magnitude 12.5 so any white dwarf brighter than that is closer than 10 parsecs or so (by definition).

 

If closer than 10 parsecs then there is likely going to be a good parallax value in GAIA DR3.  Unfortunately this may not be true for close binaries, however in true binaries you can use the parallax from the primary star.

 

You look up the formula, try and find a simple one, for calculating absolute magnitude.  You use only data from GAIA DR3.  You use the GAIA Gmag and the parallax (remember GAIA parallax is in 1/1000th arcseconds so you need to divide the catalogue value by 1000).

 

White dwarfs will cluster about Absolute Gmag 12 to 12.5 whereas subdwarfs cluster around Absolute Gmag 4.  There'll be one or two in the middle, or outliers, but the vast majority will obey this.

 

You can do the whole hog and use GAIA BP-RP too, if available.  Subdwarfs are about -0.5 and white dwarfs about 0.  HOWEVER, there is overlap in these two.

 

But if you plot then in an xy graph, BP-RP as x axis and Absolute Gmag as y axis you'll see them in separate islands.

 

See if you can find some GAIA HR diagrams online, some will give you a hint of this, the subdwarfs and white dwarfs are little islands to the bottom left of the graphs.

 

Some white dwarfs may be off the beaten path, possibly because they are unresolved binaries, but this shouldn't be  agreat issue for nearby ones and because of their apparent V magnitudes all yours are going to be with about 35 light years or just over 10 parsecs, best to try to start thinking in parsecs, they are a thing that is measured whereas lightyears are a made up thing that can't be directly measured.  You measure a distance then calculate how many years the speed of light in vacuo would need to traverse that distance, which isn't direct measurement.



#5 yuzameh

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Posted Yesterday, 06:49 PM

Well, I recently finished a research project that I had been wanting to get to for at least five years. I present a list of the sky's 25 brightest white dwarf stars arranged by brightness. It was harder than you might think because the line between a hot subdwarf and a white dwarf is a fine one. Plus, it seems to be hard to accurately measure the brightness of white dwarfs because of their peculiar spectrum.

 

I don't have much more to say than that. I hope a few people find it useful enough to try hunting some down. I've been going after them in binoculars since they're stellar with any instrument. I didn't include coordinates, but if you want those simply punch in one of the two designations listed into SIMBAD and voilĂ !

 

Download here: The Sky's 25 Brightest White Dwarf Stars

 

Scott H.

 

 

attachicon.gif WDS.jpg

I can never get into google drive so I had to read the image.  Procyon B is of course at the same distance as Procyon.  Similarly the one in Ara is going to be the same distance as its primary star.

 

Given the delta magnitude and/or the subarcsecond separations in the case of these two double stars currently you're not going to see them, irrespective of which hemisphere they are in.  V841 Ara = RST 869AB.  RST means Rossiter.  Distance between 115 and 120 light years (GAIA DR3 parallax is 0.027931")

 

I can't remember if I have ever read anywhere of anyone (amateur) splitting the Procyon visually.  It may have been done, in that I wouldn't be surprised if some amateur managed it, but it doesn't tickle any memory cells.

 

If you include things like RA and Dec in spaced sexagesimal or decimal degrees you can then import a .csv file into CDS Xmatch (websearch) and crossmatch them to GAIA DR3 or many other catalogues to find extra data.  You need an ID (running number will suffice as long as you have a means of crosslinking that back to true IDs in another table) an RA and a Dec, you need to include these as the column headers for the three columns.  You get to set a search radius in arcseconds, default is 5".


Edited by yuzameh, Yesterday, 07:14 PM.

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#6 SNH

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Posted Yesterday, 08:34 PM

I can never get into google drive so I had to read the image.  Procyon B is of course at the same distance as Procyon.  Similarly the one in Ara is going to be the same distance as its primary star.

 

Given the delta magnitude and/or the subarcsecond separations in the case of these two double stars currently you're not going to see them, irrespective of which hemisphere they are in.  V841 Ara = RST 869AB.  RST means Rossiter.  Distance between 115 and 120 light years (GAIA DR3 parallax is 0.027931")

 

I can't remember if I have ever read anywhere of anyone (amateur) splitting the Procyon visually.  It may have been done, in that I wouldn't be surprised if some amateur managed it, but it doesn't tickle any memory cells.

 

If you include things like RA and Dec in spaced sexagesimal or decimal degrees you can then import a .csv file into CDS Xmatch (websearch) and crossmatch them to GAIA DR3 or many other catalogues to find extra data.  You need an ID (running number will suffice as long as you have a means of crosslinking that back to true IDs in another table) an RA and a Dec, you need to include these as the column headers for the three columns.  You get to set a search radius in arcseconds, default is 5".

Thanks for looking into HD 149499B in Ara for me! I was suspicious about it being a double since it had a 'B' in its designation, but I didn't take the time to follow up on that. I've now updated the document and uploaded a newer version to my Drive, so the link in my first post is still active.

 

Also, I've PM you a copy of the document since you seem interested but couldn't access it.

 

Scott H.




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