Possible Nova in Centaurus

I've programmed APASS to take a look at the field.  However, at 13hrs, it will be another 7-8hrs before imaging occurs.

Arne

I made a finding chart with some comparison stars from nearby bright variables in my other charts to be able to observe this Centaurus possible nova as soon as possible:

http://varsao.com.ar/Nova_Cen_2013.htm

I am going to observe it in an hour or so.

The sequnce team will surely come up with a sequence later but for such bright stars the magnitudes are very good so there should be no problem.

Cheers,
Sebastian

Hi friends, I observe it too at 06:55 UT (Dec 03) and estimated at 5.4 magnitude using BSC stars (522 and 538 on Otero's Chart). The star was observed through 10x50B and naked eye.
A single image is available at this link:
http://www.geocities.ws/costeira1/img/cen_20131203_0700tu.jpg

I've uploaded a rather poor quality low resolution spectrum to http://www.flickr.com/photos/malclocke/11187714294/

I'm not experienced enough to place a good visual magnitude on it other than to say it looked on the bright end of 5th magnitude.

Here is a 1x1 degree image of nova Cen from APASS last night.  V band, north up and east left.  You can't miss it. :-)

The question is what stars to use for CCD observation.  At this brightness, all nearby stars are fainter, so you will have to push the nova closer to saturation or stack multiple images to get good signal/noise in the comps.

Arne

Here is a comparison of APASS images; 16x16arcmin, centered on the nova.  One is from 2012 and the other is a closeup of the one from last night; both V band.  You can see that there is a close companion to the northeast that will be a problem as the nova fades, but is not a factor now.

Arne

Visual Observation on

Dec 03.781ut = 5.0v, 20 x 80mm Binoculars

its an easy naked eye object.

Paul Camilleri - CMQ

Warners Bay NSW

Australia

Andrew's post about the nova position falling between a couple of variables that he normally follows reminded me to look at BSM_South data.  We have one variable nearby that has been imaged: ASAS_J135026-59448.  It turns out that the nova position is right on the top edge of the images, so we have three nights of BV imaging that can be used to determine any prior outburst.  These are 120508, 120515 and 130811.  In addition, I've mentioned that there are a handful of nights from APASS.

This is a pretty crowded field, fine for the current outburst, but be careful as the nova fades!

Arne

I made it at V= 4.3 at 06.37 UT.
Going to bed 5 AM these nights is worth!

I hope to have even better news tomorrow.

Cheers,
Sebastian

I had my first glimpse of Nova Cen 2013 (PNV J13544700-5909080) at 5:14am local (Adelaide) time today, as the sky was starting to become blue. All I can really say from that hurried observation, given the finder chart (provided by Sebastian above; thanks) is that it was brighter than the magnitude 4.33 comp star (2456631.28102, >4.33).

What a great sight!

Tomorrow morning I need to be better prepared:

1. Outside about 45 mins earlier.
2. Have another finder chart with brighter comp stars. Suggestions for VSP parameters welcome.

To work!

David 

I've programmed APASS so that, starting tonight, it will take a short exposure series.  At 4th magnitude, it is really difficult for APASS to use a short-enough exposure, so it may be a few nights before the nova has faded enough to be unsaturated.  We also have BSM_South taking data on clear nights; we almost got data last night, but clouds rolled in at the end of the night when the observations were to be taken.

However, there are a number of DSLR folk in the southern hemisphere - this is an ideal target!  If you have one of the SSP-4 J&H photometers, your measures are really valued.  Two bright novae in a single year - what fun!

Arne

Amazing!
We ran out of comp stars again!
It is now brighter than gam Mus (V= 3.85).

I used delta Mus (V= 3.608; B-V= 1.180) to estimate it and got V= 3.80.
 

There are some other comp stars in Centaurus/Lupus but they are rather low if we don't stay up until the early morning....

They are:

iot Lup V= 3.545; B-V= -0.182

phi Cen V= 3.820; B-V= -0.219

upsilon1 Cen V= 3.863; B-V= -0.205
 

They are all blue, the nova looks whitish but delta Mus is closer and high up in the sky.
I can't wait to observe again tomorrow!

Cheers,
Sebastian

-----------------------
Sebastian Otero
VSX Team
American Association of Variable Star Observers

Dear friends,

According to IUAC #9265 this Nova was officially named as V1369 Centauri.

Cloudy sky in Florianopolis at this Dec 5.
Another observers in Brazil estimated today between 3.7 and 3.8 at naked eye.

AAX!

Even here in the southernmost tip of Hawaii (19N) This nova rises too late in morning twilight to be readily visible. I suppose from the summit of Mauna Kea, with the perfect horizon and clarity above the clouds, it may be possible, but I'm not going to drive all the way up there just for this (2.5 hrs by road and 14000ft high!)

Mike LMK

It looks like the nova is already past its peak.
My observation is exactly the same as last night's. V= 3.8.
Observers from other latitudes seem to have caught the peak earlier today around V= 3.7.
Anyway, we need to keep observing to see what happens!

Cheers,
Sebastian
 

My observation a few hours ago was the same as Sebastian V=3.8 at 07:32UT

Gastón

I was clouded out this morning and the next few days don't look promising either. I'll try again tomorrow though.

See my blog for more including a light curve.

David

After cloud and wind, I was able to spot this lovely nova perched near beta Cen.

I estimated it at V 4.1 +/- 0.2 this morning (2013 Dec 07 @02:33 UT).

Wide-field photos are here:

http://www.psychohistorian.org/display_article.php?id=201312071011_nova-cen-2013.content

Regard,

Auke

I did some more photometry this morning (7 Dec 17:40 UT) again through the guidescope stacking 12x1s subs.  V=4.276, B=4.85.  I'm more confident in these when I saw that my measurements yesterday were within 0.005 of Arne Henden's transformed B and V obs taken with BSM South.

if my B measurement is correct, the B is fading faster than V.

i also took some lo-res spectra with the SA100. Ysterday's spectrum which showed a balanced P Cygni profile for the Hydrogen lines is gone.  Now the Hydrogen emission lines are emerging again from the continuum.  This would explain the B-V increase: the H alpha lines are staring to contribute more to the total flux.  

Cheers

jonathan

As mentioned by others, I've posted two nights of BVRI photometry from BSM_South of the nova.  These are preliminary results, as I'm just using the two 7th magnitude comp stars in the field as a small ensemble, and those stars only have UBV measures (I'm using instrumental Rc/Ic magnitudes for those two stars, as determined by BSM).  There isn't anything really bright nearby, so even in the final case, it will probably be a small ensemble of perhaps 3-4 stars.  It was nice of Peter Nelson to work hard at leaving BSM_South running on those two nights!  There was a third earlier night taken through heavy clouds, but I don't think anything will be salvageable from those images.

Each night is actually a small time series; about 90minutes on the first and 120 minutes on the second.  These measures will be stacked in the final analysis to improve the signal/noise.  At 4th magnitude, I'm taking 1-2 second exposures, so most of the scatter is from scintillation at high airmass and small telescope aperture.

V1369 Cen will be around for a long time, and is rising in the east, meaning that you will have many months of possible monitoring.  I hope that people stay interested in this one!  Perfect for DSLRs right now, and an easy target for spectroscopy.

Arne

As I mentioned above, we have a set of images taken through cloud with BSM_South on 131204 UT.  As this was during the rise to peak, the images have value.  However, the clouds were pretty thick.  I've gone through them and attempted to get some photometry, but it is taking way too long.  If someone else wants to play with the data, and try different stacking methods to get out one B,V,R,I photometric dataset, I'll be happy to place the images on our ftp site or upload them to your VPHOT account.  There are 93 images, each about 2MB in size compressed.

Arne

Here's a trap I have found in making visual estimates of V1369 Cen. There is a 4.7 to the south of the nova and a 4.3 to the north. When the Pointers are very low in the sky (for me maybe within 10° from the horizon), the 4.7 appears brighter than the 4.3. I think it's called 'extinction' but if not, please can someone correct me. This creates MAJOR problems in estimating the brightness of the nova. If fact, for me personally, it is pointless to make an estimate until the nova gets higher in the sky (ie later at night).

On 7 Dec, the spread in visual observations was 0.8 mag.
On 8 Dec 0.9 mag
On 9 Dec 0.7 mag.

Is this spread due to fluctuations in the nova, or individual observer differences, or because the nova was close to the horizon for some observations and higher for others?

Anyone got any thoughts on this?

Stephen [HSP]

After being faint last Sunday morning (V= 4.35), two days later it is back to V= 3.8. I estimated it V= 3.83 at 07.31 UT.
I think it is showing ups and downs and we are missing it because of lack of coverage, because I see that sometimes I make it brighter or fainter than other observers some hours earlier or later.
Will it be an important rebrightening or just an example of that variability?

Exciting object!

Cheers,
Sebastian

Hi Sebastian,

Yes, there is a hint of variability in the short BSM_South time series.  These are taken at high airmass (starting at X=2.5), so I don't have strong confidence and would like it if we had additional digital observers (not all visual observers have Sebastian's eyes!).

At mag 4, this is still too bright for APASS, so I won't have any Chilean time series for another week or two.  We saw fluctuations near maximum with V339 Del, so this is not unusual.  I'm hoping some of the DSLR observers will start posting their data!

Arne

The nova is still too bright for APASS to obtain reliable photometry, at least in normal passbands.  I thought that you might like to see the difference in the nova field between the Johnson B passband (400nm) and the Y passband (1000nm).  Here is an 800x800 cutout of the field from last night, with a 2-second exposure for B (saturated on the nova) and a 20-second exposure for Y.  Enjoy!

Arne

For those of you who may be interested in V1369 spectra (H-Alpha region, resolution 11000, dispersion 0.21 A/px), I have posted some recent profiles in:

http://www.spectro-aras.com/forum/viewtopic.php?f=5&t=742

Please notice the prominent P-Cygni profile in the Dec 5 spectrum, indicating an expansion speed in the range of 900 km/s. On the other hand, the Dec 9 spectrum shows a much stronger emission in H-Alpha (the same phenomenon happened with V339 Del a few days after the explosion).

Spectra details available in the above link.

Regards,

Tasso Napoleao (NTA)

Tonight it was supposed to be a Geminids' night but it was cloudy in BA most of the night. Fortunately at 3AM clouds parted and I could make some observations. I saw only a couple of faint Geminids but was able to look the other way and what a surprise it was to see the nova brighter than ever! It was at V= 3.3!! I made a second estimate when sunrise started and I made it at V= 3.27 at 07.26 UT and rising.

So this is an update with more comparison stars:

bet Mus V= 3.05; B-V= -0.19
lam Cen V= 3.13; B-V= -0.05
alp Cir V= 3.18; B-V= 0.25 (roAp, ampl. 0.02 mag.)
nu Cen V= 3.41; B-V= -0.23 (R, ampl. 0.02 mag.)
iot Lup V= 3.55; B-V= -0.18 (Possible BCEP, ampl. 0.01 mag.)

And I could enjoy 3 bright Geminids between 07.10 and 07.20 when I was looking to the opposite side of Gemini :)

Cheers,
Sebastian

Finally the clouds parted in Canberra and I was able to do some photometry.  A rapid drop: at 16 Dec 16:40 UT it was V=4.715, B=4.90. 

I also took a low resolution spectrum with the SA 100.  Ha lines continue to increase and FeII lines strong.

B  continues to get closer to V.  In fact B-V now = 0.  Both 5.03 this morning, 18/12/2013 17:00 UT

I note that Nova Del did the same at the same point in its evolution.  I wonder what is happening spectrally?

Cheers

Jonathan

What's this nova doing? First observation in six days and it was back up to about 45 even 44 on Dec 23.500. Definitely brighter than 47.

Stephen [HSP]

The AAVSO home page references the above article published by www.universetoday.com/.

The article talks about an image from Rolf Wahl Olsen in which the nova appears pink.  The image is a LRGB and I suspect shows more than a little false color.  After all, black and white pretty pictures don't sell all that well.  But it is the explanation that really leaves me scratching my head.

“The nova appears pink because we are really viewing the light from an expanding shell of ionized hydrogen which emits strongly in both the red and blue part of the optical spectrum,” Rolf explained. “These emissions give the nova its strong pinkish colour, similar to emission nebulae which are also predominantly pink/magenta in hue.”

It would seem that color should be a function of tempature rather than chemical composition.  I would expect that there should be multiple hydrogen lines present but not a basic shift in color.  On checking the AAVSO light curve and this forum, it appears that most observers are reporting a B-V of between 0.0 and 0.6.  A little on the blue side to neutral.

What am I missing?

Jim Jones

Jim,

My understanding is that we are not actually seeing the photosphere of the star itself.  The ionised ejecta from the nova are optically thick at this point. We are only seeing the expanding gas cloud - mostly ionised hydrogen, of course, but a significant component of doubly-ionised iron.  The attached low-resolution spectrum from 26 December gives you some sense of the relative intensity of the Ha and Hb emissions relative to the underlying continuum.

B-V started at about 0.5 when the nova was at maximum.  This dropped to around 0 by about 18/12 as the Hb lines really started to take off.  Then B-V has increased a little to its current level of around 0.15, my guess is as the FeII lines around 5100 A have made more of a contribution to V.

The Ha line at 6562 is the source of the pink, and is outside the passband of the V filter.  If we had ongoing R measurements, we would see them significantly brighter than B or V.  I asked Santa for R and I filters, but he didn't cough up :-)

Traditional assumptions around B-V don't hold up for an object like this.  Look at the obs for 18/12 taken by Arne.  B-V is close to zero, indicating a pretty blue star (this is the Hb).  But V-R is 0.7!  Most unusual, to say the least, for a colour index based on temperature.  But explicable through the intensity of the hydrogen emission lines.

Cheers

Jonathan

This nova had three main peaks (four if we count the bright bump before the brigthest maximum) and now it is fading rapidly again after the most recent of those peaks (which was much shallower than the other two). Will this fading be the definite one? Its behaviour has been so erratic that I am more inclined to say "no"...
It is at V= 4.8 on December 30, 06.32 UT.

Cheers,
Sebastian

I notice another bounce in brightness is being displayed in the AAVSO light curve (4 Jan 2014).  I'm seeing lots of reports of magnitudes to 4.3 and even to 4.1 on popular forums and I wonder if the Purkinje effect is coming into play.  I was just outside and tested it using binoculars.  Staring at the nova and close bright comp stars it could seem as bright as 4.3, maybe brighter.  Using the recommended quick glance method it was dimmer, around 4.7-4.8.  The best measure I could get was by placing the nova and the 4.3 & 4.8 comp stars in the same binocular field and quickly glancing at the centre of the field, all the bright stars being in peripheral (averted) vision.  It was consistently close to the 4.8 star in brightness, maybe a slight touch brighter (4.7).

While the trends of the light curve have been clear, there is still a scatter of about 0.5 mag or more in visual estimates.  What's more is that there is no clear denser line of 'favoured' observations, just a 0.5 mag scatter.  No doubt airmass differences could be a contributor but the nova is reaching reasonable altitudes in late evening in the south and is quite high for morning observations.

Cheers -

Rob Kaufman KBJ

Hi Rob, all

I wrote a blog post about observing the nova from Stockport Observatory last night.

Rob, I used both an unaided and binocular approach with short observations of the nova and I'm confident of the 4.5 observation.

David