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Wolf 359 lghtcurve

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bskiff
Wolf 359 lghtcurve

In view of the recent public engagement announcement about using the New Horizons spacecraft to get instant parallaxes of Proxima Cen and Wolf 359, I had a look at data I took in 2015 for the latter star.  I have now re-reduced these images with improved magnitudes for the comp stars, and find that the star has a clear rotation period of 2.69 days with full amplitude about 0.02 mag.  The phased lightcurve is attached.  This may be a 'new' result, but needn't be a secret.  (TESS will surely blow this lightcurve out of the water.)  These are from the Lowell 0.7-m robotic telescope, mainly 3-minute V filter exposures.  The rms scatter is 0.009 mag.  Data taken during a number of flare events are omitted, and the remaining jitter is surely from low-level activity on the star.

Given the upcoming parallax observations, I started a new series last night (Apr 14 UT).  The star has moved considerably and is now clear of field stars (it was crowded by one in 2015).  There is no significant change in the overall brightness and the new data fit the old lightcurve with seemingly little change in phase.  So evidently the active longitudes on the star are relatively fixed over the interval.

\Brian

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dcrowson
Brian,

Brian,

is Wolf 359 the same as CN Leo? When I look it up in simbad, it gives CN Leo as well as GSC 00261-00377 and others. Those appear to be a couple different stars but very close to each other. I noticed the campaign as well and I've been pointing at it when clear but vphot is telling me there are no variables in my field (but there are seq stars). I've never had this issue with vphot before and I wonder if this is somewhat why there have been no observations since 2015?

Dan

bskiff
Wolf 359 lightcurve

Yes, this is CN Leo.  I wouldn't ever call it that for historical reasons, but it is a valid name.  The large proper motion may cause some issues with designations in various epoch catalogues, and it could be that VSX is placing it at the epoch/equinox 2000 position, whereas it has moved off considerably to the southwest from that location.  The motion is about 4".7 per year toward pa 235 deg.  Using an image from last night, I get a position of  10 56 23.6 +06 59 59  for equinox J2000 but epoch 2020.28.

     It would be of interest to know if someone else can confirm the 2.7-day rotation period.

\Brian

bskiff
Wolf 359 lightcurve

I just had a look at a AAVSO finder chart.  The star is indeed plotted for some date in the recent past.  It is now nearly due south from the 144 comp star, basically to the lower-right of where it is shown, and to the lower-right of the field star near there.

     I have adopted magnitudes for four comp stars from a combination of ASAS-3, TASS MkIV, APASS DR9, Pan-STARRS, and GAIA2.  The magnitudes I decided on are ~0.05 mag brighter than the AAVSO ones for the two stars in common.

\Brian

dcrowson
I'm still confused on this

I'm still confused on this one. My image is rotated 180 degrees. I'm figuring it is one of the stars to the right of measure in this image but vphot tells me no variables in the field.

Dan

spp
spp's picture
missing variable in VPhot

Message deleted.  Ken picked up on this question in the VPhot Forum.

Sebastian Otero
Sebastian Otero's picture
GCVS names in VSX

Hi Phil,
If a star has a GCVS name, that will be the primary name in VSX so there is no case when a GCVS star is listed in VSX under another name.
The problem with CN Leo lies -as Brian pointed out- on its very large proper motion. The star is very far away from its J2000.0 position right now. And VSX uses those coordinates. VSP doesn't precess them to the current epoch so these stars will cause problems.
Follow Brian's comments to find where the red dwarf is.

Cheers,
Sebastian

spp
spp's picture
Names

Hi Sebastian,

"If a star has a GCVS name, that will be the primary name in VSX so there is no case when a GCVS star is listed in VSX under another name."

Thanks for the correction.  

Phil 

bskiff
Where is Wolf 359 ?

You have the correct field!  The image has south-up and west-left.   Between your star 148 and the legend to its upper-left, there is a small trio of stars.  Wolf 359 is the brightest one, i.e. the upper-left star of the trio.  Hope that helps.

\Brian

 

dcrowson
That is what I figured. The

That is what I figured. The issue is that vphot does not think there are any variables in this field. I'm not sure where I should go on this one. I tried CHET but was told it was mainly for chart errors.

Dan

bskiff
Wolf 359 coords, lightcurve

I just did a "search everything" trawl in Vizier in hopes of finding a near-current epoch position for the star.  But it is not in GAIA2, so the most recent positions-of-date are nearly 10 years old (e.g. WISE).  Anyway, the image in the thread above shows the star for spring 2020, as described previously. 

     I also found in VizieR that the star was "on silicon" for one of the Kepler K2 campaigns, and folks have derived the rotation period from those data, getting values close to 2.70 day.  One source says the amplitude is only 0.003 mag(!), which seems low even for the red K2 passband.  You have to have fairly good precision, but it is not that hard to see the current 0.02 mag variation.

     And finally, thanks to Sebastian for the comments here and also the amendments to VSX.

\Brian

SQL
SQL's picture
Wolf 359 K2 period

Hello Brian: I found a period in K2 very similar to the one you found, with your comments. Try to track
the star in ASAS Sn but I couldn't find her. I never participate in these forums but I have been doing data mining for years and I have been
K2 poll and now Tess like other surveys. It is a great honor to exchange this information with you and with my colleagues at AAVSO.

Raul Salvo - Uruguay - Observatorio de Montevideo .

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