[vsnet-alert 9899] re bright variable quasar QSO B0133+47
da55 at Safe-mail.net
da55 at Safe-mail.net
Sat Feb 9 00:51:23 JST 2008
This is an intriguing object. It is in many a radio source catalogue, both all sky survey and direct monitoring ones, so for convenience's sake I'll refer to it as DA 55, which appears to be it's first identifier by precedent.
SIMBAD reveals that it has been well known as being a _radio_ variable for some time, and it appears in a great many papers related to such matters, sometimes on its own, sometimes as part of other lists.
Indeed, at a preliminary glance it looks as though it is monitored in the radio spectrum at regular intervals. Yet there appears to be little or nothing in terms of optical monitoring, certainly not in the established literature.
Given that some people like to follow active galaxies and QSOs this may be a rewarding object, both visually and for CCD photometrists, in that light. Normally such work has to wait for professional campaigns with radio instruments in order to be meaningful, similar to the OJ 287 campaign Gary Poyner occasionally notes on the BAAVSS ALERT weblist.
But this object looks to be sufficiently monitored that just making it a programme object will lead to work that will overlap and coincide with radio work at some points or others.
Photometrically the above GIF shows the recent behaviour, with two adjacent stars in forms a triangle which is quite illustrative of the optical changes as the brightness varies. This shows unfiltered CCD work, so its red sensitive imaging.
Strangely old POSS plates show the object to be quite faint, 18th to 19th red magnitude. A more recent near infrared N plate magnitude is similar to the current value, at about 15th mag.
CMC14 lists it as r' 15.0 from two observations, this being a mean value of those two observations, with the standard deviation listed as > 0.7! r' 15.0 is comfortably above the faint limit of the CMC14 survey, so this value likely reflects true variability between these two observations, both in the post2000 era.
Similar, circa 2000, we have the UCAC2 red sensitive magnitude, which although not photometric, is usually accurate enough to a global +/- 0.3, and that gives a magnitude of 14.3.
And the above GIF gives quite a range too, from around 16 to 14 unfiltered, and in quite short intervals at times.
2MASS also detects it in late 1999 with J mag about 16 and Ks mag about 14.
And it's a ROSAT point source object, both first and second catalogue version.
But other than that there appears to be little if any optical photometry.
NED lists none.
But what NED does list is an interesting little bunch of radiograms, both traditional contour plots and modern false colour contour plots, plus some grayscale radiograms
and as the titles of many of the papers that include this object suggest, this object has a relativistic radio jet associated with it.
And the radio variability looks to stem from the interaction of this jet with a neutral hydrogen cloud in the Intergalactic Medium, as the form of the resulting plasma cloud appears to change over time.
And it now seems the object also markedly changes optically over time.
The object appears to be related to a type of objects called DRAGNS by some
although, having apparently only one lobe, whether DA 55 fits the definition of these objects is not quite clear (ie the [D]RAGNs are [double] lobe sources).
For variable AGN/QSO observers the object lies not all that distant from the more familiar 3C 66A, and looks as though it could be actually more interesting in terms of optical variability.
An admittedly not thoroughly exhaustive search suggests that no one is actively monitoring this object opically in any way, yet it might well be amongst the more active such objects available, as visual and photometric observers regularly manage the 14th to 16th magnitude range nowadays.
And as noted above, it is a regular target of radio astronomy campaigns, both picked up in many surveys at many wavelengths, and targetted in surveys aimed at objects with relativistic jets, and even on occasions monitored in the time domain.
It isn't beyond the realms of possibility that should the recent optical outburst event have been noted somewhere like ATEL at the time that this may have generated ToO radio monitoring too. However, people having liaison links with radio community observers would be better placed to enquire after that possibility, and I suggest to them that they forward Seiichi's email to any such people for their interest, and enquire of them if regular monitoring in the optical and notification of bright state events, ie when the object is obviously on a rapid rise to 14th magnitude, would be of interest. I'd assume that optical behaviour lags the radio behaviour, and an enhanced jet (or blob) event may well be past by the time the optical consequence appears, but the measuring of redshift of optical spectral lines for relativistic effects might be of interest to some, if visible.
A quite active, and reasonable amplitude, object well studied for variability in the radio spectrum (especially by those interested in the interactions of QSO/AGN sourced relativistic jets with radio lobe sources), but apparently little known in the optical, although evidently variable in said. Suitable for any campaign or observing list for those already involved in variable QSO/AGN programmes.
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