Affiliation
American Association of Variable Star Observers (AAVSO)
Thu, 02/13/2014 - 18:51
Moving into the predawn sky, RS Tel is noted as having now recovered to maximum. The observation of 10.50V on Feb 11, 2014 is at least 6 magnitudes brighter than last summers minimum estimate of fainter than 16.4V in July 2013. In VSX the range is currently listed as 9.6-15.34V.
kind regards,
Steve O'Connor
WX CrA is another RCB now entering the pre-dawn sky. I observed it recently, on Feb 9 2014 at 13.12V, this being even fainter than the magnitude 11-12 estimates that were reported at the end of its' last observing season. Checking back in the database I was surprised that I had to go all the way back to October 2004 to find it reported in the 13s. Looking forward to checking this one again when the chance presents itself. The VSX range for WX CrA is currently listed as 10.25 - <15.2V.
kind regards,
Steve
V CrA, now a pre-dawn star, is observed to still be in deep minimum, perhaps at record faintness.
I have it at 17.86V (0.21) on Feb22.776. 136 and 152 were the primary comps. The current fading episode seems to have begun in early 2012. It was observed as faint as 17.6V during the last observing season (SXN).
An earlier minimum, in 2007, showed the star reported at V around 16.5 a number of times, once as faint as 16.9.
On my current observation, I note a faint companion (about 16.62V), several arc-sec N of the RCB. Can't help but wonder whether it was this star that was responsible for reports of the RCB in the 16s during the 2007 fade, perhaps V CrA itself being way fainter.
There's a mira in this field, CD CrA, about 15 arc-min away. This star is currently well beyond the minimum listed in VSX. It's sitting at 17.08V (0.12) at the moment, whereas the VSX range is 135-163p. Very careful identification needed for this one when feeble like this.
Good observing to all !
Steve
S Aps is yet another RCB currently in a long deep minimum. Seems like more variables of this type are currently active than not !
My recent estimate of 16.44V (0.05) on Feb23.721 2014 shows this active star has no intention of returning to its' normal state just yet.
The current minimum seems to have begun about June 2013 with a decline from about 10.5v to about 14.3V by mid July. This apparently was followed by a steeper dive to around 16.5V in early August. There was a short-lived mini-recovery to 15th magnitude in September 2013 followed by a fall to a new deep low near 16.9V by years end. And then my observation from yesterday ...
This kind of fairly detailed photometric/visual history is only possible due to the persistant efforts of numerous observers. Kudos to all of you ! Keep up your amazing work.
Steve
Hi All,
S Aps is still 3 to 4 magnitudes below normal as of earlier this month (Aug, not yet reported). I've got several observations between May-August of this year (soon to be posted ! ) which show the star has come up to the mid-14s (V) by mid-May and further,to the low-13s (near 13.8V) by last week.
Looking back at the last 10,000 days of data on the LCG (back to April 1987) it's evident that the 2013-2014 'event' was the most drastic ever witnessed for this star in at least the last 27 years or so. I haven't checked further back in the record at this time.
Was this rather drastic fade of about 7 magnitudes representative of S Aps turning a new evolutionary corner ? Perhaps it was more the case of luck, and adequate equipment being brought to bear at an oportune time. Fades of 7 to 8 magnitudes for 'real' RCBs seem more the norm than the exception although one would think there must be a certain point in each RCB's evolution, where they start evidencing these super-minima. Is that what S Aps is showing us now ?
A check back in the historical record for this star (a number of decades I imagine) should give clues as to how well any ealier fades were documented.
One sure thing .... keep watching !
kind regards,
Steve
The southern RCB known as ASAS J164124-5147.8 in Ara appears to have been active since before AAVSO observations began on it in August of 2012. Up to now, only a single positive estimate has been reported, at 14.2v on Aug15 2012 (PEX). The range, in VSX, is 11.7 - <14.4V.
I prefer simply calling this one BHJ-177, a simplified version of its' AUID (000-BHJ-177).
The field is very close to the galactic plane, hence quite crowded with faint stars. I have a recent, positive estimate of this elusive RCB, currently at V = 18.14 (0.24) on Feb23.716 2014. Comparisons used were 139, 141, 143 and 148. The identification that VPhot provides in this dense field is the correct one. I verified this by referring to the DSS2 IR image taken in May 1980.
So, currently about 6 magnitudes below maximum. If this RCB has a total range similar to better observed examples of this type like SU Tau and R CrB (8 to 9 magnitudes), BHJ-177 could possibly dip to 20th magnitude or so, who knows ? At the very least, this is a highly active star.
regards,
Steve
As if a portent of things to come, the first estimate in the AAVSO International Database on this neglected RCB variable (also known as ASAS RCB-18, or my personal favorite, simply BKT-290) has it in a deep minimum, fainter than 17.2V on February 25.564 2014.
Careful not to confuse it with the closeby visual companion, measured as V=14.59 (0.05) on the same date. Check your VSP charts.
I may have archived a couple of images of this field some time ago - I'll report back if I find anything.
This active RCB variable is located at 19h 00m 09.44s -02d 02m 57.9s (VSX) and now a predawn object. The maximum ('normal') brightness is between 13.5 - 14.0V when the star is behaving itself.
Good Observing,
Steve
I try to follow RCBs and this one is in my range. But there is only the one data point (yours?) in the entire AAVSO data base. I don't want to waste time on a wild goose chase. When was it last above 15?
It has a nice ASAS lightcurve which is published in:
http://arxiv.org/pdf/1211.2475v4.pdf
Geoff
Hi, Steve,
The ASAS light curve includes both objects so the actual maximum is a little fainter. 13.8-14.8 would be a better estimate of the star's behaviour at maximum.
I have added a note about the companion to VSP/VSX so observers are aware of this. Thanks for pointing it out.
Cheers,
Sebastian
Still very much in its' active state but significantly brighter than it has been for a long time, UW Centauri has recovered to between mag 14.6V and 14.9v (max is magnitude 9) in the current minimum which appears to have begun sometime between September 2008 and the beginning of 2009.
The AAVSO LCG nicely illustrates the current long, deep fade to as faint as 17.8V (a record low) in April 2013 (SXN). It also suggests that the current 5 year long minimum is, up to now, the second longest one on record for this RCB, going back more than 60 years.
As well, UW Cen apparently, is no stranger to failed comebacks. The longterm light curve shows the star is more likely than not to fade out again, perhaps several times, before eventually making it back to full maximum. This phenomenon has already occured once during the present fade episode - the star recovered to at least 14.7V in August 2012 (DSI) before dropping off to the 17th magnitude in the first quarter of 2013.
Good observing to all,
Steve