In the current Light Curve of the Week addressing the bright novae V1500 Cygni, Matthew Templeton comment's on an off-hand remark by Brad Schaefer noting that:
"Since the Second World War, there has only been one nova to reach second magnitude, 1975's V1500 Cyg (Nova Cygni 1975). Prior to world war two, there were 1-2 per decade. Is the universe conspiring to have fewer bright novae?"
Matthew responds by saying, "Probably not. Brad made several suggestions as to why this might be the case, but it may come down to fundamental changes in how people have observed the sky during the past 50 years. Improvements in observational technology may have enabled the community to find more faint novae, but these may have in turn taken our attention away from events that might've been obvious to our predecessors."
This odd lack of "bright" novae in recent decades is something I likewise noted and commented on to colleagues long ago and in an historical context I too find equally curious. However, I cannot accept that modern observers are less diligent and may have missed any such obvious outbursts. Plus, with the kind of imaging sky coverage that has been underway since the 1980's by a host of advanced amateurs (first by photographic means and today via CCD) I would say that virtually every novae coming above 10th is likely detected within just a very brief interval following the onset of an outburst.
Now I can personally recall quite a number of distinctly nakedeye and near nakedeye novae during the 1950's to the 70's, but a general decline of even these during the insuing decades, something which I find even more strange. Nevertheless, my take is that the situation can be nothing more than a result of random chance. Averaged over an interval of centuries I expect that the "bright" novae rate is still likely to be quite constant in spite of our current drought. Still, the current state of affairs is a most disappointing one for visual observers.
Be that as it may, I'd be interested to hear what others might have to say concerning the distinct oddity of a lack of bright novae in our time.
J.Bortle (BRJ)
John,
These are good points, and I agree that this may simply be a statistical fluke. I should clarify though that it wasn't Brad's (nor my) intention that modern observers are less diligent, simply that methods may be different. Brad is working on a statistical study to clarify exactly what you're asking, and I'll have to wait for his results to say more.
However, I will follow up with a question for you and for nova searchers generally: do you still do large-area, naked eye surveys? More generally, do you make it a regular part of an observing session to just "look up"?
Matthew posts:
"However, I will follow up with a question for you and for nova searchers generally: do you still do large-area, naked eye surveys? More generally, do you make it a regular part of an observing session to just "look up"?
Now I'm certainly no nova searcher myself, but for information purposes I would offer that in the course of conducting my evening variable program, amounting to usually 60-80 fields spread around amost the entire sky visible at that hour, I am reasonably positive that I would immediately notice any interloper of +3.5 or brighter, along with ones of +4.0 situated within 5 degrees of specific fields I observer. Of course, NY weather, especially in winter, is notoriously poor, severly limiting the number of available nights and thus detection opportunities.
J.Bortle (BRJ)
There were many bright novae in the first half of the 20th century, but e.g. the second half of the 19th century there were none brighter than 2nd mag. either, or they were not noticed (see http://www.cbat.eps.harvard.edu/nova_list.html).
Weeks or months after the outburst these bright novae will fade to magnitudes that are within range of the improved technology, so they will very likely be found anyway. Survey data may then give a good idea of how bright they really got. A case in point is Nova Pup 2007 (V598 Pup) discovered by the XMM-Newton satellite at mag 10 months after the outburst, but then found to have reached at least mag. 4 in ASAS data (see e.g. http://simostronomy.blogspot.be/2008/07/hello-operator-mis-information-please.html).
Patrick
KT Eri was discovered by Itagaki at a CCD magnitude of 8.1 on November 25, 2009, but pre-discovery images were later found, giving its peak magnitude at 5.4 on November 14. I remember, even I found KT Eri was visible on the DSLR images of two Hungarian amateurs taken near the maximum of the Leonids meteor shower.
The "Pi of the Sky" project observed KT Eri every night up to 12 days before the discovery.
Accoording to their website the "Pi of the Sky" apparatus continuously monitors the sky. They scan the whole sky twice a night (20min/scan). So probably they can catch the brightest novae.
http://grb.fuw.edu.pl/piinta1/events_index_public.php
But as I've noticed there is still room to improve the all sky coverage and discovery of transient objects. In the last few years several bright novae or CVs have been discovered weeks after their peak brightness. One tipical example comes into my mind is Mis V1448. This dwarf nova (or classical/recurrent nova?) was discovered by Seiichi Yoshida on June 8 2012 at 13.4 mag from 2012 May 27 images made by Youichirou Nakashima. When Yoshida discovered Mis V1448 about 2 weeks have already passed afret the doscovery images was made by Nakashima. However, Denis Denisenko found the pre-discovery data by the MASTER robotic telescopes at 12 mag on May 13. And this object might have been brighter between 10 April and 13 May 2012.
Actually the story of prediscovery images was one of the final trigger pishing me towards DSLR photometry and starting our "Vendégcsillag-kereső" (Guest Star Hunter) programme wich led to the discovery of three new variables Vend2, Vend44 and Vend219 up to now.
While I make my 10-20x30s images with my Canon EoS 1000 + 300mm focus (zoom) telephoto lens I usualy check the sky with naked eyes. Probably I would discover any new objects brighter than 2.5-3 magnitudes and in some parts of the sky brighter than 4th mag. But the wheather here in Hungary was very bad this winter.
I know there are several project running or are in the planning phase with the aim to have at least daily fully sky coverage and do photometry of all bright stars (above 10-15th magnitudes) and chack for optical transients, but
a) the history of past few years clearly shows that there are still several OTs discovered weeks after they peak brightness
b) the long term sustainability of these projects are not realy secured (since most of them are based project funding)
so maybe it is time to start a grassroot, co-ordinated, P2P full sky monitoring initiative. With the modern ICT tools it would be quite easy to share information about who is/was imaging some specific parts of the sky down to a given magnitude limit.
I can for example say that I make 10-20x30s DSLR images with ~3x4 degrees FOV of 10-20 variables almost all clear nights with a limit usually around 14-15th magnitudes. My main regular fields are: V Cas, SS Cyg, V778 Cyg, CO Cyg, khi Cyg - EY Cyg, V404 Cyg, HO Lyr, T Lyr, PQ And, LX And, LS And, S Tri, NSV 895 Per, GK Per, GQ Per, NVS 1436 Per, CG Cam, UV Aur, DN Gem, U Gem, S LMi - RZ LMi, SW UMa, CH UMa, DO Dra, SS Dra, V CVn, TV CVn, IC 4182, V838 Her. I also observe some other fields too, but these are the fields I try to observe when possible.
If a few dozen amateurs do a coordinated work probably we can cover the full sky without starting a huge invesment in new equipments.
Here is the list of the target fields of our Vendégcsillag-kereső (Guest Star Hunter) programme.
Is there anyone checking regularly the fields BSM for optical transients? Is the list of target fields of BSM available?
Clear skies,
Robert Fidrich "Fidusz"
HAA/VSS
Is there anyone checking regularly the fields BSM for optical transients?
Not specifically unless Arne does it himself. We have a custom program that does star matching and astrometry, and I'm wondering whether one could detect transients by checking for images that fail matching? I've never actually done a test adding a synthetic star to an image and seeing whether the matching fails... The field size of BSM isn't large though, only 2 by 3.
It's a valid point that they might get caught later. However, you can potentially get better data when they're bright, particularly spectroscopic data -- that was especially true in the pre-CCD era, but is still true to an extent. And novae present themselves differently near maximum and late in the outburst, especially after they become optically thin. Catching them early has its benefits, and that was sort of the point of the conversation we all had with Brad that day.
Hi Robert,
The BSM fields are not currently being checked for new transient objects. We currently have one BSM actively running (BSM-South), with two others nearly operational and a couple more at various stages of implementation. Each of these has a Telescope Advocate who sees all of the images. If someone wanted to volunteer as a Telescope Advocate who also wanted to check the images for new interlopers, that seems like a win-win situation.
That said, the total BSM survey covers about 1500 variables that are brighter than 8th magnitude. Each field is about 3 square degrees, so we are looking at perhaps 5000 square degrees of sky coverage on an annual basis, once all systems are running. With one BSM, perhaps 1000 square degrees are covered about once per week, a low-enough cadence that it is far more likely an initial discovery will be made by someone else. BSM was not designed as an all-sky survey, but instead is a targeted survey.
I posted the survey fields somewhere; I'll see that they get posted again.
Arne
Dear Arne,
I think my friends László Németh would be happy to volunteer checking the BSM images for new transients, but I'll ask him. Maybe on some clouded nights I can check some images too.
I was right; these files have been posted before. Go to
http://www.aavso.org/bright-star-monitor-stations
and at the bottom of the page are links to the northern and southern survey field files.
Arne