NOVA Del 2013 = V339 Del

An amateur spectroscopic survey of a bright classical CO Nova

 Nova Del - Page 0 Nova Del - Page 1 Nova Del - Page 2 Nova Del - Page 3 Nova Del - Page 4
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 The fire ball and optically thick phase From 14-08 to 22-08-2013 Strong Balmer and Fe II lines with P Cygni profiles First appearence of [O I]
 Main features and evolutions Blue continuum fading Balmer and Fe II lines with P cygni profiles First appareance of [OI]

 Discovery 14-08-2013 The fire ball stage
 Olivier Thizy - Alpy600 - R = 650 Oliver Garde - eShel - R = 11000 The first spectra show clearly a nova type Fe near its maximum luminosité, with narrow balmer liens, Fe II lines, noticelly multiplet 42. Most of the lines shows a P Cygni absorption.    " strong H-alpha emission with a P Cyg profile extending to a maximum radial velocities of -2300 km/s (absorption, EW approx 8.1A) and +2400 km/s (emission, EW \approx 52.9A) with no terminal edge at high negative velocity. The emission is broad, asymmetric (stronger blueward) and now structureless. The He I 6678 appears to show a detached absorption feature at -870 km/s without strong emission. In contrast, He I 5875 shows a strong P Cyg line with velocities similar to H\alpha. Both components of Si II 6347, 6371 (RMT 2, see Williams, R. E. 2012, AJ, 144, 98) are present in absorption with vrad \approx -1100 km/s; Fe II 6456, and N I 6486 also appear to be present with vrad \approx -1100 and -960 km/s, respectively. The spectrum is typical of a classical nova -- possibly CO type -- in the early (optically thick) fireball stage but with indications of the onset of the recombination event (e.g. Shore et al. 2012, A&A, 537, C2) , based on weak displaced broad absorption from the Na I D lines. The interstellar components of Na I D are not saturated, suggesting the extinction is relatively low " ATel# 5282, S. Shore & al., 2013 H alpha H beta H gamma Na I D lines and He I 5875 strong P Cygni profile Si II 6347 and 6371 strong absorptions He I 6678

 15-08-2013 The rise toward maximum

 François Teyssier -Lisa - R = 1000 Oliver Garde - eShel - R = 11000 ATel#5291 Tarasova & al., 2013 The spectra display that Nova Del 2013 is still in the fireball stage as mention Darnley et al. (ATEL 5279) and Shore et al. (ATEL 5282). The spectra contain the strong emission lines of Balmer series exhibiting PCygni profiles with velocities (Halpha ~ -1400 km/s, Hbeta ~ -1200 km/s, Hgamma ~ -1120 km/s, Hdelta ~ -960 km/s) and strong FeII lines of 40, 42 multiplets, medium FeII lines of 37, 38 multiplets with also P Cygni profiles (RV ~ -900 km/s). H alpha H beta H gamma
 Fe II (42) lines 4924 5018 5169 Fe II lines (27,37,38)

 Comments about velocity by Steve Shore The terminal velocity of the line profile is an absolute thing, relative to the rest , not the separation of maximum and minimum (you see that described, too often, in the older photographic literature).   So you're right in saying that there's been a change but it's mainly in the shape and minimum of the absorption.   You'll notice that in the last profile the absorption has changed shape, this is the sort of thing some models predict for the evolution as the ejecta expand since the different layers have different temperatures and densities along with different velocities.  You never see this sort of thing in winds unless they're very collimated (and that's rare enough). Instead, the decrease is when the line is formed deeper in.  Remember, this was very hot and not that it's cooling the optical is becoming less opaque.  This is a part of the spectrum where there are few absorbers, the main opacity sources are scattering and thermal (and the photosphere down to which you're seeing -- or rather a moving opaque surface).  The timescale for the changes is consistent with the column density varying as 1/t^2 and the optical depth varying as 1/t.  So you would expect that (since the intensity depends on the exponential of the optical depth) that the line intensity at any velocity should vary as I(vel) ~1- exp [- (t0/t)] where the time t0 is a scaling time.  In other words, as the expansion causes the opacity to drop the intensity at a given velocity increases (decreased absorption).  This will go on for a bit until the Fe lines appear, as they seem to be now starting to do.

Maximum : August 16.45 UT at V=4.3 mag (ATel #5297 Munari & al., 2013)

 16-08-2013 The first decline The first decine is unusual : A first very fast drop in luminsosity (ATel)
 Keith Graham - Alpy600 - R = 650 Oliver Garde - eShel - R = 11000 ATel#5297, Munari & al. Nova Del 2013 seems to have reached maximum brightness on August 16.45 UT at V=4.3 mag. It immediately entered the decline phase and it is declining pretty fast, of the order of 1 mag in a day, qualifying it as a very fast nova if the pace will be maintained on the coming days... The strong CaII (3934, 3968) and NaI (5890, 5896) interstellar lines appear single component and have an heliocentric radial velocity of -2.6 +/- 0.2 km/s. The equivalent width of NaI 5890 is 0.3945 +/- 0.003 Ang, which corresponds to a reddening of E(B-V)=0.182 following the calibration by Munari and Zwitter (1997, A&A 318, 269). All strongest diffuse interstellar bands are readily visible: 5780 (equivalent width 0.136 Ang), 5797 (e.w. 0.014 Ang), 6196 (e.w. 0.010 Ang), 6203 (e.w. 0.048 Ang), 6614 (e.w. 0.024) Our Echelle spectrum for Aug 15.83 shows a flat topped Halpha emission profile (confirming Tomov et al. ATel #5288), with - at best - only a feeble trace of a double peak; on Aug 14 the emission was trapezoidal in shape, on Aug 16 it turned into Gaussian profile; (3) HeI lines has weakened during the rise toward maximum: on Aug 14 they displayed a marked P-Cyg profile, on Aug 15 the emission component disappeared, and on Aug 16 also the absorption component vanished; (4) while the equivalent width of the absorption component of the P-Cyg profile of Balmer lines have remained essentially constant during the rise to maximum, that of emission component has steadily declined: for Hbeta it was -24.3 Ang on Aug 14.84, -14.6 Ang on Aug 15.83, -9.1 Ang on Aug 16.85 U H alpha H beta H gamma

 17-08-2013 The first decline Halt post maximum   Max + 1 day Mag ~ 5.0
 Jim Edlin - LISA - R = 1000 Oliver Garde - eShel - R = 11000 ATel#5304 Munari & al., 2013 "Spectroscopically the plateau phase was characterized by a large reduction in the intensity of emission lines, with FeII and Hbeta almost vanished, and CaII H and K lines rivalling Halpha in terms of integrated flux. At the same time the absorption spectrum strongly increased in overall intensity, up to a point when the absorption lines where so strong and blended to make impossible to recognize the level of the continuum. The end of the plateau phase has been marked by the rapid vanishing of the absorption spectrum and a large increase in intensity of the emission line" We estimate that maximum was reached on Aug 16.25 at V=4.3. The nova immediately bounced back from maximum and initiated the decline. The decline proceeded linearly at a rate of 0.6 mag/day for about 22 hours, until Aug 17.15 when it suddenly halted and the nova remained stable at V=4.85 until Aug 19.0 UT. The nova entered this 1.85 day long V-band plateau with a blue color, B-Ic=+0.70, and left it appreciably redder at B-Ic=+1.17. Following the plateau, the nova resumed the decline, this time at a slower 0.28 mag/day rate in the V band. Our latest measurement on Aug 20.817 UT reads B=5.78, V=5.37, Ic=4.52 H alpha H beta H gamma

Merged spectrum of 4 spectra obtained with a 600 l/mm grating - Paolo Berardi

 The fireball stage by Steve Shore At the start of the expansion, at least when we see the nova visibly, the ejecta should pass through a stage called the fireball.  This is an opaque stage that resembles a single expanding surface, or a sort of thin atmosphere, with an almost uniform temperature.  Usually that isn't observed but in this nova it might have been caught.  The expansion velocity is high enough that the matter can't radiate efficiently enough to cool by energy loss, the temperature drops instead because of the increasing volume at constant mass -- he energy density is dropping.  This is the same as saying that the total energy remains almost constant but the temperature decreases.  Then something important happens.  When the matter gets cool enough, first the hydrogen and then heavier elements start to recombine.  This releases some energy (from the excess energy of the electrons as they're captured by the ions) but mainly that the neutral and low ionization stages have much higher line (and continuum) opacities and the absorption in the ultraviolet increases quickly.  The lines that absorb there are the ground state transitions; that is, they're the strong zero volt states.  Their upper levels are those that both pump the absorption strength of the optical transitions and excite the levels to reradiate.  So the Fe II spectrum, for instance, suddenly starts to appear.  There are coincidences with some of the He I lines, e.g. He I 5016 is close to Fe II 5018, the same for He I 4923 being near an Fe II line (in these cases they're both from the same lower level).   The lack, in the last spectra, of He I 5875 gives the game away: the triplet series (He I 7065, 5875, 4471) being absent means the stuff at the near-coincidences if Fe II (and other heavy ions).   In the Ondrejov spectra, we have Ca I 4226 yesterday suddenly making an entry.  At the same time Ca II showed a higher velocity absorption than the H-beta line.  So the ejecta seem to be showing some depth structure now. What all this means is that we're watching a stage in a classical nova that hasn't been covered since photographic series on DQ Her, the last nova that was bright enough for such coverage in the modern era, although DN Gem and CP Pup were also well covered (but not like what all of you have produced!)   As I've already written, we're in new territory here -- between observational capabilities and opportunities to catch individual events -- so it's important that you keep up your courage and bang away.  It is possible that within the next week there it 'll be a shortlived absorption stage in CN 4216 (and also 3883).    In the IR there should be a CO 2 micron emission stage.  If the nova isn't a DQ Her type, then we really have no analog.  The continuing fluctuations in the photometry, also known from other novae at maximum light, remain a very deep problem and, again, any observations with the highest possible cadence (this also means longitude coverage from all of you to get the most continuous sequences) will be critical.  For instance, the disappearance of the He I corresponded to a "local" peak in the optical light, this could be a recombination event or it could be multiple ejections.  To speculate, so early, is too risky (even for a theorist!) so I'll stop now and hope this explains the stages you're seeing. One more point, though.  The recession of the absorption velocity is something also known from the DQ Her outburst,  this is an effect of the change in the transparency of the ejecta.  If this is the effect of seeing deeper into the layers at first during the late fireball, then it should reverse as he recombination sets in and the ejecta cool.

 18-08-2013 The first decline Detection of gamma rays
 Thieery Lemoult - eShel - R = 11000 ATel#5302, Hays & al., 2013 The preliminary gamma-ray daily-averaged flux, F(E>100 MeV) = (3.3 +/- 0.8) x 10^-07 ph cm^-2 s^-1, and photon index, 2.2 +/- 0.2 (errors are statistical only), for August 18 are consistent with previous gamma-ray novae H alpha H beta H gamma

 Comments about gamma rays by Steve Shore Nova Del 2013 has been the in the energy range above 100 MeV.  for perspective, is is an energy interval where thermal processes are irrelevant and indicate something relativistic is happening.  More on that in a moment.   The detection makes this the second classical nova (third if you count Nova Sco 2012 whose nature remains uncertain).  The other was V959 Mon = Nova Mon 2012, although the gamma-ray detection occurred while the nova was invisible fro the ground due to the Sun.  The first detected nova, V407 Cyg = Nova Cyg 2010, was like RS Oph, a recurrent (probably) nova that exploded within the wind of a red giant companion so it was a physically very different mechanism that accelerated the particles to the required energies although the avaklable energy was ultimately the same.   The luminosity of Del 2013 is about 1/3 to 1/4 that of Mon 2012 at peak.  If novae are, somehow, a new sort of "standard candle" in the gamma-ray range, then that implies a greater distance (a factor of about 2 at most), placing Del 2013 at around 6-7 kpc.  That is a problem since the nova is not in the plane and such a distance is uncomfortably far above the height of the distribution expected for the main population candidates.  It also makes the nova particularly luminous (and that is the next issue).  The gamma's are generated by a variety of processes, all involving accelerating either electrons or protons to high enough energies that they either scatter visible and UV into the MeV and higher range, or that the protons collide and emit pions (remember those form the "nuclear glue", the mesons that bind nuclei) that decay at around that energy (but not higher).  There's a hint that perhaps the energy range is more extended and that would favor relativistic electrons scattering photons up to higher energies (the inverse of the process, known from the birth of modern physics, as Compton scattering; an electron scatters a photon at low energy but releases it at high energy in the observer's frame of reference). Why this is important is that the origin of cosmic rays has been a headache for almost a century (since shortly after they were discovered).  These are particles that must be actively accelerated, likely by stellar sources such as supernovae, but the actual process is elusive.  If even little novae can do this, it makes it far more likely that strong supernova shocks -- those expected when their ejecta slam into the surrounding interstellar gas -- can work.  That makes astroparticle types salivate and for good reason, we have here something that happens on human rather than Galactic timescales. The other reason is the likely presence of internal shocks and collisions between fragments of the ejecta.  It's well known, and you will all see this in the weeks ahead, that the ejecta are hardly uniform or homogeneous, they consist of fragments of a wide range of density and mass, and these will be clear once you start seeing multiple absorption components on the main emission lines (e.g. Balmer series, Na I, Ca II, Mg II, Fe II).  But that's just barely staring and the next couple of weeks will show what the structure of the ejecta is. If these shocks are slamming into *each other*, the ejecta themselves may be the site of the acceleration and therefore it becomes a generic (!) phenomenon of novae depending only on the available energy and mass.  We don't know the answer to this and it's one of the reasons the measurements of the slow peeling of the layers in which you're all engaged is so important.

 19-08-2013 The first decline - Smooth decline Max + 3 days Mag V ~ 5.0
 Joan Guaro Thierry Lemoult- eShel - R = 11000 P cygni profiles vanishes Balmer lines stengthens H alpha H beta H gamma

 22-08-2013 The first decline Max + 6 days Mag V ~ 5.8
 Jean-Noël Terry Alpy600 R =650 C. Buil eShel R = 1000 H alpha H beta H gamma

Focus on near UV/Blue and possible CN lines

 Near UV - R. Leadbeater - LHIRES III 1200 l/mm Blue - C. Bui - eShel R = 11000
 Comments about Dust formation and CN lines by Steve Shore Now a quick word for the moment about CN and why this is so important. One paper (!!) by Wilson and Merrill http://adsabs.harvard.edu/abs/1935PASP...47...53W reported this line and only in DQ Her. But they also discussed the Na I in another paper and Payne-Gaposchkin discussed this also. The molecule, CN, is amazingly stable for a radical (no, not a political comment). It has a high dissociation energy and can remain in stellar atmospheres to hotter values than the Sun (> 5800 K). The same for CH and CO but we don't see those in the optical; they've been detected in the IR. The usual molecule is CO that consumes almost all of the C w=o if that channel is saturated it means the C/O ratio is high enough for other organics and hydrocarbons to form. The others, often quite complex, are seen in winds from highly evolved stars. And the higher the C abundance the more is available from which the solid phase -- dust -- can condense. Any isotopic anomalies remaining from the nuclear burning will also remain locked in teh dust so after a while drifting through the Galaxy (shades of the Hitchhiker's Guide, no?) they can be incorporated through passage in a molecular cloud, into a star. The dust forms in a way we don't well understood but it is likely that molecular formation and growth is a signal of the right environment for the appearance of grains. This may be purely chemical, homogeneous condensation or "nucleation", or it may be induced (sorry, some of my own work) but whatever the mechanism, it happens. Therefore we can witness the dust formation process in a well constrained event and -- holy grail though it is -- figure out what triggers the dust formation. Other molecules have been detected in the IR, CO for example, but nothing from the cold matter in the ground state. In Nova del 2013, it seems that the CN has not appeared but it may yet and there's every reason to continue at all resolutions.  DQ Her by Stratton and Manning (1939) with the CN 4216 band

 Comparison between an amateur (Buil) and a professionnal spectrum (Ondrejov Observatory) Comments from Steve Shore : " This is just one order, it's VERY good agreement and this time -- pure chance -- the spectra are literally simultaneous.  This should clear any doubts about the quality of the spectra produced by ARAS " Most of the spectra of the ARAS Data Base have been treated with ISIS software (C. Buil) ISIS Page

Publication in ATel#5312, Shore & al., 2013

# Continuing spectroscopic observations (3500-8800A) of Nova Del 2013 with the Ondrejov Observatory and the ARAS group

ATel #5312; S. N. Shore (Univ. of Pisa, INFN-Pisa); P. Skoda, D. Korcakova, P. Koubsky R. K?Ã­?ek, P. Rutsch, M. Slechta ((Astronomical Institute, Academy of Sciences of the Czech Republic- Ondrejov, Czech Republic); O. Garde, O. Thizy , T. de France, D. Antao, J. Edlin, K. Graham, J. Guarro, F. Teyssier, P. Berard, i T. Bohlsen, E. Pollmann, T. Lemoult, A. Favaro, J.-N. Terry, E. Barbotin, F. Boubault, J. P. Masviel, R. Leadbeater, C. Buil, B. Mauclaire (contributing participants, ARAS)
on 23 Aug 2013; 01:15 UT
Distributed as an Instant Email Notice Novae
Credential Certification: S. N. Shore (shore@df.unipi.it)

Subjects: Optical, Cataclysmic Variable, Nova

Observations with the Ondrejov Observatory 2m Zeiss coude spectrograph (R = 18000) are continuing covering the range 3550 - 8870 A (see ATel #5282). High cadence spectroscopic monitoring by the Astronomical Ring for Access to Spectroscopy (ARAS) began on 2013 Apr. 14.8 and has continued uninterrupted covering the wavelength interval at resolutions ranging from 3684 - 7431 A with resolutions ranging from 580 - 11000 with time sequences as short as 10 minutes at resolutions up to 12000. The ARAS spectra(at this writing more than 230) are publicly available at the consortium website: http://www.astrosurf.com/aras/Aras_DataBase/Novae/Nova-Del-2013.htmParticipating observers are throughout Europe, North America, and Australia. The coverage is especially dense during the period spanned by the Fermi/LAt detection and continuing observations. The rapid changes reported by the Liverpool group (ATel#5300) have not only been confirmed but resolved although the shortest interval in which significant line profile changes were detected (R > 700) was > 6 hrs with the variations being far less prominent on Aug. 20. In addition to reports in Atel #5304, ATel #5305, Balmer absorption components were detected to at least H14 on Aug. 22 (HJD 2456522.6) with vrad (abs. min) = -600+/-50 km/s. As reported, the absorption on the lower Balmer lines is also at this low velocity but the emission wings extend now to approximately +/-2000 km/s, consistent with the maximum velocity reported in the first observations from Aug. 14. The Na I D line now shows a complex absorption trough, possibly with components of both the D1 and D2 lines at -850 and -600 km/s. On Aug. 22.8 the Fe II 4921,5018 A showed absorption extending to -1400 km/s with weak indications of incipient narrow absorption at lower velocities. In the 8400-800 A region, O I 8446 may show absorption but has a profile compatible with the Na I emission and no discernible mean redshift. The changes are now relatively slower than during the first week and the nova is likely deep into the Fe-curtain phase in the UV having now passed out of the fireball. The line profiles suggest possible asphericity of the ejecta but it would be premature to speculate further. Multiwavelength spectroscopy, especially in the infrared between 2.1 =- 2.3 microns (for Na I 2.20 micron, CO 2.15 microns, etc) are extremely important now; the only feature clearly present at CN 3883, 4216 are atomic lines (e.g. Ca I 4226) but this is the period during which any molecular formation would be observed; regardless of the rate of optical decline this stage is critical to cover with R > 500 and over broad spectral range.

ARAS database for Nova Del 2013

 25-08-2013 Max + 9 days Mag V ~ 6.3 ( ~ Mag V max + 2)
 J. Edlin Lisa R =1000 T. Lemoult eShel R = 1000 H alpha H beta H gamma

Next Page - The first decline 1st part

Miscellanous treatments by ARAS observers

Ha evolution E. Barbotin

Ha evolution O. Garde

Ha evolution Ernst Pollmann

Spectral evolution (gif) by Paolo Berardi Link A MUST !

Spectral evolution by Olivier Thizy : a continuous coverage during 10 nights

Page built by François Teyssier - 25-08-2013