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Bright new dwarf nova (or nova?) in Sgr: PNV J17522579-2126215

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FRF
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Dear Folks,

There has been a new transient in Sgr reporten in the CBET TOCP home page: PNV J17522579-2126215

http://www.cbat.eps.harvard.edu/unconf/followups/J17522579-2126215.html

The latest data show it has brightened up to 8.9R.

The medium-resolution optical spectrogram obtained with the 0.5m RC telescope of the Gothard Observatory by L. Kiss et al. show lack of strong emission lines (private communication). So this may be a dwarf nova, not a nova? Interesting...

Bright new dwarf nova (or nova?) in Sgr: PNV J17522579-2126215
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  I have submitted a sequence to HQ.  Stay tuned.

AAVSO sequence soon
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Thanks, Mati!

Meanwhile I've also sent a preliminary sequence to the Sequence Team list, so hopefully we can print a good chart sooon. Actually the Hungarian observers are already excited, but we still have several hours until it gets dark here.

I wonder what will be the real nature of this object. Anyway some time series would be useful too. Let's see the first result of the BSM run tonight...

Clear skies,

Robert Fidrich (FRF)

I observed this object,
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I observed this object, visually, last night and it was at 9.6 magnitude. That's my report:

AAVSO Format
PNV J17522579-2126215|2456105.4264|9.6|BK|95|96|7963JB|MOON TYC

or VSNET format
PNV J17522579-2126215 20120626.9264 9.6 AAX MOON TYC

PNV J17522579-2126215 sequence
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I've uploaded Mati Morel's sequence to VSD. It should be more than adequate to the task for the next few weeks to months, depending on how quickly this one fades.

 

PNV sequence
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I've processed the BSM-south data, and have new magnitudes for Mati's stars, as shown below.  Unfortunately, I can't edit the stars easily in VSD right now.

  ID          RA (J2000) DEC         V     B-V    V-R    R-I    V-I
Variable  17:52:25.81 -21:26:21.5  10.005  1.634  1.192  1.011  2.211
95        17:53:07.05 -21:24:45.2   9.441  0.688  0.397  0.361  0.756
105       17:52:37.78 -21:24:43.4  10.475  1.039  0.591  0.608  1.197
106       17:52:50.78 -21:32:34.9  10.528  0.586  0.328  0.336  0.660
114       17:52:21.59 -21:26:11.8  11.358  0.869  0.460  0.400  0.859
119       17:52:13.07 -21:23:21.7  11.757  0.737  0.405  0.415  0.816

all with Poisson errors under 0.02mag.  As you can see, the variable
is heavily reddened, and (V-R) is not unusual, so there is not much
Halpha emission. The coordinates are from the BSM astrometry,
 and are probably good to 0.2arcsec or so.

For visual observers, the labels only change by 0.1mag or so, and I don't think you will see any difference.  CCD observers probably should use the values above, as they are internally consistent.

Arne

Revised PNV sequence
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We have one night of calibration from BSM-south, and one night from BSM-north.  Luckily, the two nights pretty much agree. Mike Simonsen has uploaded the mean values from those two nights for the sequence stars from 95 through 119 into VSD, and so they should be available.

The nova has faded dramatically in the past 24hrs, and was V=10.8 as of about 12UT.

Arne

Has there as yet been
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Has there as yet been any reported spectroscopic evidence to clearly indicate whether we are dealing with an actual fast nova, or simply the outburst of a previously unknown dwarf nova of some type?

If anything other than a classical nova, of course one would immediately suspect a UGWZ star considering the peak brightness and yet no earlier discoveries. With the variable's position projected against the relatively starless background of a broad dark cloud in the Milky Way, PNV J17522579-2126215 should have been easily detected at some point previously unless the interval between outbursts is extremely long. Were outbursts on a more frequent time scale than even a couple of decades, I feel that it would have favored some earlier discovery as this region was so heavily covered photographically with wide-field patrol cameras for upwards of a century by professionals.

BRJ

No spectra yet
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Hi John,

That is an excellent question and point. To my knowledge (and I've been scouring the net) no one has taken a spectrum yet. It's kind of faint so would require a fairly large telescope. But looking at the BVRI data from the two BSM telescopes and discussing it with Arne, I'm leaning more towards a highly reddened dwarf nova (UGWZ?). It might even be a recurrent nova, which could account for the rapid rise and subsequent fading we are seeing as well as the lack of historical evidence of previous outbursts.

This case illustrates plainly how much a 24-inch AAVSOnet telescope in New Zealand with a spectrograph would be a great benefit to the organization. If we could just find such a thing, and a partner who would help us get it up and running...

;)

spectrum
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"no one has taken a spectrum yet."

This is not true.

As I've already mentioned the medium-resolution optical spectrogram obtained with the 0.5m RC telescope of the Gothard Observatory by L. Kiss et al. show lack of strong emission lines (private communication). According to them this may be a dwarf nova, not a nova. They've already sent the details about the spectrum ~ 2 days ago. I don't understand why the CBAT people have not published it yet.

Settle for second best - 22 inches in New Mexico
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This case illustrates plainly how much a 24-inch AAVSOnet telescope in New Zealand with a spectrograph would be a great benefit to the organization. If we could just find such a thing, and a partner who would help us get it up and running...

Can you settle for second best?  The 22-inch Autoscope is sitting in my garage.  Can you find supports/partners that want to get it running?

Would a low-resolution
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roe
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Would a low-resolution spectrograph a la the grism designs of Christian Buil handle jobs such as this?  They report interesting results on 3C273 (mag 14?) with an 8-in.  Back in '03 we demonstrated usable results on 15th mag asteroids with an 8-in.  Seems like it could just occupy another slot in a filter wheel.

Nova Spectrum
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Christian got a spectrum last night.

A typical  He/N nova

 

http://www.astrosurf.com/buil/nova_sgr2012_2/obs.htm

I'm currently on the nova (SC 10 " and LISA Spectrograph)

You can see the raw spectrum :

http://www.spectro-aras.com/forum/viewtopic.php?f=12&t=348

with broad H alpha line

 

Best regards


François Teyssier

Thank you, Francois. Now at
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Thank you, Francois. Now at least we can be pretty well certain just what type of object we are dealing with and this essentially eliminates any real need to search for prior outbursts (as had it been a DN) so far as I am concerned.

I would note also that by this morning the nova has reportedly declined by two full magnitudes, although the rate of decline has clearly begun to slacken in past 24 hours. The limited lightcurve so far available would seem to place PNV J17522579-2126215 among the "fast" novae and quite the opposite in behavior from nearby Nova Oph 2012.

Unfortunately, with the inceasingly gibbous moon rapidly approaching the nova's position observations, particularly visual ones, will be rather hindered for the next few days.

BRJ

 

 

 

I've been taking R and I data
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I've been taking R and I data since the 10th.  Haven't yet reduced it....  I'm a newbie, and I see that some R and I data have been submitted.  I'd like to also reduce it....

Jason

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484