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RCB Activity: Will The Real RZ Normae Please Stand Up

ocn's picture
Joined: 2010-07-25

Hi To All

Just like to draw your attention to RZ Normae : This RCB star, although still 4 to 5 magnitudes below max, is apparently beginning to recover from an even fainter level observed in late May 2013 (16.2V). Unfortunately, a wide field image I was able to secure on March 25th of this year is, although quite deep, pretty useless due to the presence of the close 13th mag companion (see note in VSX).

The minimum in VSX is listed as <14.2V. The database (I've only looked at the obs from 2000 to the present so far) shows very few positives below the magnitude given for the close companion. Would some of you like to weigh in on this one ?

Very best regards to all,

Steve O'Connor

RCB Activity: Will The Real RZ Normae Please Stand Up
WPX's picture
Joined: 2010-10-30

Hi Steve and All.

The early chart 352 issued about 1977 by the old VSS RASNZ did not plot the mag 13.5 star close NE of RZ Nor and some observers (no doubt me included) have misidentified this field star with the variable.  RZ Nor does not appear to stay near that brightness for very long and this field star is therefore easily misidentified when the variable is faint or over powered when RZ Nor is near maximum.

It is clearly resolved in my visual 30cm reflector that I began using in 1992.  This was at a time when detailed charts were simply not available and the Internet something that might just catch on.

I first noted this companion star during the deep decline of RZ Nor in 1999 and confirmed its presence in a field sketch during the subsequent decline of 2001.  I mentioned it to the AAVSO in an email in July 2012 when it was apparent that it was being confused with the variable.  Perhaps this prompted the remark in the VSX.

In any case, observers need to be careful when observing RZ Nor during deep minima to ensure they clearly identify both the variable and companion.

Tks and regards.

Peter Williams (WPX)  

RZ Nor
CGCA's picture
Joined: 2010-10-06

Thanks for pointing that out. I became aware of it when we took a decline spectrum of RZ Nor and it was an A star! I made a note of this in my recent review paper on RCB stars,

Geoff Clayton

RZ Nor's incorrect proper motion (due to the companion)
wel's picture
Joined: 2010-07-26

In preparation for the paper about R CrB stars that Patrick Tisserand, Geoff Clayton and I published recently, I tracked down the proper motions from the PPMXL catalog of the R CrB stars to be listed in our paper. RZ Nor's proper motion was a whopping 103.6 milliarcseconds per year (compared to the others which were typically 20 milliarcseconds per year or less. The reason, of course, was that the nearby A-star was identified with RZ Nor at one epoch (when RZ Nor was in deep decline) but not at the other.



RZ Normae Recovering
ocn's picture
Joined: 2010-07-25

Hi All

Just like to note that RZ Nor is recovering from a sixteenth magnitude minimum it reached in May. Evidently it didn't spend much time there:  By June 23 it was back up to 15.4V, and just last night, observed at V=15.08. We'll see if it gets all the way back up to maximum....

Interesting how some of these events are of relatively short duration while at the other end of the 'RCB Zoo' you've got variables like R CrB itself (and UW Cen) just to name two, that have real marathon style fades lasting years.


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