Eruptive stars spectroscopy Cataclysmics, Symbiotics, Novae ARAS Erupve Stars Informaon Leer n° 35 #2017-06 01-08-2017 Observaons of June July 2017 Contents F. Teyssier, A. Skopal, S. Shore, J. Guarro, D. Boyd, P. Somogyi, O. Garde, W. Sims, T. Lester, C. Buil, P. Berardi, U. Sollecchia, F. Campos, P. Luckas, T. Bohlsen, J. Foster, L. Franco, F. Boubault, J. Edlin, J. Moner, T. Rodda, C. Kreider Novae Nova Cen 2017 ongoing observaons Nova Sct 2017 slow nova discovered in JUne Supernovae Bright Type IIp supernova SN 2017 eaw in NGC 6946. Ongoing observaons Symbiocs Ongoing campaign CH Cygni AG Dra campaign Request for observaons of R Aqr by Margarita Karovska (p. 47) Augusn Skopal: On the stellar wind from hot components in symbiotic binaries Steve Shore: Nova Sct 2017 IRAS 17449+2320 and other misdemeanors Supernova spectra “We acknowledge with thanks the variable star observaons from the AAVSO Internaonal Database contributed by observers worldwide and used in this leer.” Kaa, S., 2015, Observaons from the AAVSO Internaonal Database, hp://www.aavso.org Authors :
Transcript
Eruptive stars spectroscopyCataclysmics, Symbiotics, Novae
ARAS Eruptive StarsInformation Letter n° 35 #2017-06 01-08-2017
Observations of June July 2017Contents
F. Teyssier, A. Skopal, S. Shore, J. Guarro, D. Boyd, P. Somogyi, O. Garde, W. Sims, T. Lester, C. Buil, P. Berardi, U. Sollecchia, F. Campos, P. Luckas, T. Bohlsen, J. Foster, L. Franco, F. Boubault, J. Edlin, J. Montier, T. Rodda, C. Kreider
NovaeNova Cen 2017 ongoing observationsNova Sct 2017 slow nova discovered in JUne
SupernovaeBright Type IIp supernova SN 2017 eaw in NGC 6946. Ongoing observations
Symbiotics
Ongoing campaign CH CygniAG Dra campaignRequest for observations of R Aqr by Margarita Karovska (p. 47)
Augustin Skopal: On the stellar wind from hot components in symbiotic binaries
Steve Shore:Nova Sct 2017IRAS 17449+2320 and other misdemeanorsSupernova spectra
“We acknowledge with thanks the variable star observations from the AAVSO International Database contributed by observers worldwide and used in this letter.”Kafka, S., 2015, Observations from the AAVSO International Database, http://www.aavso.org
Authors :
Nova Cen 2017NOVAE
Coordinates (2000.0)R.A. 13 20 55.32Dec -63 42 18.5Mag V 10.9 V (discovery)
ARAS Eruptive Stars Information Letter 2017-06 - p. 3
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ASASSN-17gk = Nova Cen 2017
2017-06-02.575
2017-06-04-474
2017-06-27.501
2017-07-01.495
2017-07-06.435
2017-07-25.572
2017-07-30.487
Nova Sct 2017NOVAE
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Nova Sct 2017 (V)
Coordinates (2000.0)R.A.DecMag V
ASASSN-17hx was discovered in images obtained on UT 2017-06-23.47 at V~12.5 (ATel # 10523 and ATel #10524) and spectroscopically identified as a nova (ATel #10527)The evolution of the spectrum is described in ATel#10527, #10558 (Paolo, Umberto and Woody), and #10572. See page 6.But:- the reference to the taxonomic classification of Williams, 1992 in ATel#10527 is inappropriate- the luminosity continued to rise after mid-July and reached its maximum on July, 30th
ARAS Eruptive Stars Information Letter 2017-06 - p. 4
One of the first spectra of the nova, obtained by Paolo Berardi, with a Lhires III, 150 l/mm In this spectrum the He I lines mentionned in ATel#10527 are still obvious. They will disap-pear later.
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2017-06-29.861
2017-06-30.270
2017-07-01.865
2017-07-02.333
2017-07-30.967
2017-07-29.821
2017-07-28.892
2017-07-26.846
2017-07-25.842
2017-07-24.851
2017-07-22.884
2017-07-19.849
2017-07-15.862
2017-07-12.856
2017-07-11.867
2017-07-10.846
2017-07-08.871
2017-07-07.510
2017-07-06.454
2017-07-05.855
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Nova Sct 2017 (V)
ARAS Eruptive Stars Information Letter 2017-06 - p. 5
Spectral evolution during the long riseLow res spectra obtained by Paolo Berardi, Umberto Sollecchia, Woody Sims, Fran Cam-pos, Terry Bohlsen, Paul Luckas, Christian Buil, Olivier Garde, Lorenzo Franco
73 spectra in ARAS Databasehttp://www.astrosurf.com/aras/
Nova Sct 2017
He I He I
Nova Sct 2017NOVAE
Spectral confirmation of galactic nova ASASSN-17hx (=ASASSN-17ib)ATel #10527A. Kurtenkov (Institute of Astronomy and NAO, Bulgaria), T. Tomov (Nicolaus Copernicus University, Torun, Poland), P. Pessev (GTC, IAC, ULL, Spain)on 24 Jun 2017; 12:07 UT
ASASSN-17hx (=ASASSN-17ib, ATel #10523, #10524, RA = 18:31:45.918, Dec = -14:18:55.57, J2000) was recently identified as a galactic nova can-didate prior to its optical maximum. On 2017 Jun 24.0 UT we obtained three low-resolution spectra of the object with a 15 min exposure each. The observations were made with the FoReRo2 focal reducer mounted at the 2mRCC telescope at the Rozhen observatory in Bulgaria. Preliminary wave-length and relative flux calibrations were applied. The strongest emissions in the nova spectrum are H-alpha and H-beta. Other strong emissions are HeI (7065A, 6678A, 5876A, 5048A, 5011A, 4922A, 4713A), NII (6482A, 6346A, 5679A). This indicates that the nova is of He/N type, accord-ing to the Williams (1992, AJ, 104, 725) classification. Also present are the NIII 4640A and HeII 4686A emissions, with the NIII line being stronger.The FWHM of the Balmer emissions is 1180+/-10 km/s and 1130+/-20 km/s for H-alpha and H-beta respectively, not accounted for the low spectral resolu-tion (R=500). The strongest HeI lines show P Cyg profiles from which absorption components an expanding velocity of the order of 990+/-80 km/s can be estimated.A combined spectrum can be previewed at: https://www.dropbox.com/s/2235tx1fqscwbeo/ASASSN-17hx_Rozhen_20170623.png?dl=0
Continuing spectroscopic monitoring of Nova Sct 2017 = ASASSN-17hxATel #10558Paolo Berardi, Woody Sims, and Umberto Sollecchia (ARAS Group)on 6 Jul 2017; 02:40 UTCredential Certification: S. N. Shore ([email protected])
We report the results of low resolution spectroscopy of the classical nova Sct 2017 = ASASSN-17hx (Atel# 10523, #10524, #10527) as part of the continuing nova monitoring program by members of the ARAS group. Spectra were obtained on 2017 Jun 29.8, Jun 30.3, Jul 1.9, Jul 2.3, Jul 4.3, and Jul. 4.8 with resolu-tions ranging from about 580 to 2650, depending on the spectrograph (Alpy600, LISA, LHIRES) and covering ~3800-7200A and S/N of about 20-100) with exposure times ranging from 3500 to 10400 sec. The He I spectrum ATel #10527 has persisted but weakened steadily since Jun 24, while after Jun 29 the Fe II 4921, 5018, 5169, among others, spectrum appeared with P Cyg profiles having maximum velocities around -800 km/s. The absorption troughs have increased in relative strength, from about 10\% on Jun 30 to around 25\% on Jul 4. Halpha showed absorption through Jul 2, at -1000 km/s, with the emission FWZI re-mained about 3200 km/s. On Jun 29-30, the He I lines showed P Cyg troughs extending to about -800 km/s, as reported previously; the absorption has persist-ed but both it and the emission have weakened, the profile narrowed, and the maximum velocity reduced to about -500 km/s or less. Na I D absorption, likely interstellar, was detected in those spectra with sufficient resolution. No Na I emission was detected but that may increase as the metallic lines develop. N II emission, reported in Atel #10527, was not detected on any of the spectra. The spectra are now those typical of the optically thick, post-fireball stage of the ex-pansion. Observations are continuing, all spectra are publicly available though http://www.astrosurf.com/aras/Aras_DataBase/Novae/2017_NovaSct2017.htm
Photometry and spectroscopy of FeII nova ASASSN-17hx, finally passing through maximumATel #10572U. Munari (INAF Padova), F.-J. Hambsch, A. Frigo, F. Castellani (ANS Collaboration),G. La Mura (Univ. Padova), G. Traven (Univ. Ljubljana), M. Ozbey Arabaci, T. Saguner (Ataturk Univ.) on 13 Jul 2017; 10:08 UT
More than two weeks past its discovery, nova ASASSN-17hx has finally reached what appears to be its peak optical brightness. Announced as a candidate nova on June 23.7 UT (ATel #10523), we begun daily photometric monitoring of ASASSN-17hx on June 24.07 UT when we measured V=12.39, B-V=+0.72, V-I=+1.19. After a monotonic - although structured - rise toward maximum, peak brightness has been reached at V=10.90, B-V=+0.85 on June 10, followed by a slow decline.
We are collecting high and low resolution spectroscopic observations of ASASSN-17hx with several telescopes over the 3200-9100 Ang range: Asiago 1.82m and 1.22m, Varese 0.6m, and Tubitak 1.5m. Spectra recorded around peak brightness shows a textbook example of a FeII nova, with prominent emission from Balmer and Paschen series, FeII (strongest multiplets 27, 38, 42, 48, 49, 74), Si II, OI (7772, 8446) and CaII far-red triplet (8498, 8542, 8662 Ang). All lines are flanked by structured P-Cyg absorptions of a width varying with the ion and multiplet. They appear sharpest for FeII multi-plet 42, for which on July 11.87 UT we measured the strongest absorption components at -451, -359 and -285 km/s heliocentric velocity, with the emis-sion component at +11 km/s and FWHM=265 km/s. From the equivalent width of the diffuse interstellar band at 6614 Ang we derive a reddening E(B-V)=0.68 following the calibration by Munari (2014, ASPC 490, 183), well matched by the E(B-V)=0.62 implied by the B-V color at maximum when compared with the mean intrinsic value for novae by van den Bergh and Younger (1987, A&AS 70, 125). Interstellar lines from NaI appear as a saturated blend of several individual and unresolved components. Other interstellar absorptions present in our spectra include CaI, CaII, CH+, KI and several DIBs
ARAS Eruptive Stars Information Letter 2017-06 - p. 6
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H alpha - ASASSN-17hx
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Nova Sct 2017 (V)
H alphaSpectra acquired by Terry Bohlsen and Paul Luckas with Lhires III - 2400 l/mmR = 15000
The nova near maximum luminosity Echelle spectra obtained by Tim Lester, Joan Guarro, Olivier GardeThe emission almost disappear at maximum luminosity and the lines remain almost un-changed during two days from 28th to 30th of July (green lines)
ARAS Eruptive Stars Information Letter 2017-06 - p. 10
SN 2017 eawSUPERNOVAE
Coordinates (2000.0)R.A. 20 34 44Dec +60 11 35.9Mag V 13
AAVSO V light curve and ARAS spectra
Discovered by Patrick Wiggins (Tooele, UT) at unfiltered CCD magnitude ~12.8on 2017 May 14.2383 UTThe supernova is located 153” NW of the center of NGC 6946. SN 2017eaw is Type II supernova (ATel #10374), more precisely Type IIP (ATel #10376)
ARAS Eruptive Stars Information Letter 2017-06 - p. 11
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SN2017 eaw(V)
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sn2017eaw
Monitoring by Peter Somogyi, with an Alpy R = 600
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SN2017eaw
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SN 2017 eawSUPERNOVAE
2017-06-20.970
ARAS Eruptive Stars Information Letter 2017-06 - p. 12
2017-06-07.877
2017-06-08.194
2017-06-12.047
2017-06-21.032
2017-06-22.460
2017-06-26.875
2017-06-30.047
2017-07-07.865
2017-07-20.008
Spectroscopic evolutionSpectra obtained by Olivier Garde, Paolo Berardi Christian Buil, Jim Edlin,James Foster, Fran Campos, Peter Somogyi, Jacques Montier26 spectra in ARAS database : http://www.astrosurf.com/aras/Aras_DataBase/Supernovae/sn2017eaw.htm
Symbiotics in June-July
Observing : main targets
AG Dra: weak ouburst mid-May - Excellent coverage following R. Gàlis & al. request - We continue the monitoring at a lower cadency - at least one spectrum a week
CH Cygni : ongoing campaign upon the request of Augustin Skopal and Margarita Karovska CH Cygni is strongly rising
SU Lyn: observations requested by Katarzyna Drozd (Nicolaus Copernicus Astronomical Centre)
R Aqr: monitoring requested by Margarita Karovska
V694 Mon: still in ‘quiescent’ stage - Observations requested by A. Lucy and J. Sokolovski
RW Hya: new star in the database with spectra obtained by Paul Luckas
SYMBIOTICS
ARAS Eruptive Stars Information Letter 2017-06 - p. 13
ARAS Eruptive Stars Information Letter 2017-06 - p. 15
Id. Observer Date Res. Id. Observer Date Res.AG Dra J. Foster 28/05/2017 3981 7399 951 AG Peg F. Teyssier 18/06/2017 4208 7160 11000AG Dra F. Teyssier 01/06/2017 4142 7160 11000 AG Peg T. Lester 05/07/2017 4031 7950 13000AG Dra W. Sims 02/06/2017 3866 7448 588 AXPer F. Campos 22/07/2017 3749 7281 736AG Dra J. Foster 02/06/2017 3865 7400 667 AXPer D. Boyd 25/07/2017 3901 7380 938AG Dra J. Guarro 03/06/2017 4053 7761 9000 BF Cyg F. Campos 09/06/2017 3755 7290 841AG Dra P. Somogyi 03/06/2017 6466 7175 2585 BF Cyg F. Teyssier 17/06/2017 4208 7160 11000AG Dra P. Somogyi 03/06/2017 4534 5251 1688 BF Cyg J. Foster 23/06/2017 3891 7401 792AG Dra T. Lester 04/06/2017 6020 7120 9000 BF Cyg T. Lester 04/07/2017 4031 7950 12000AG Dra J. Guarro 05/06/2017 4053 7498 9000 BF Cyg K. Graham 16/07/2017 3679 7377 519AG Dra K. Graham 06/06/2017 3603 7404 530 CH Cyg C. Kreider 10/06/2017 6490 6630 14174AG Dra J. Guarro 09/06/2017 4059 7667 9000 CH Cyg J. Guarro 10/06/2017 3980 7761 9000AG Dra F. Campos 09/06/2017 3756 7296 765 CH Cyg F. Teyssier 10/06/2017 4210 7150 11000AG Dra P. Somogyi 10/06/2017 6446 7154 2608 CH Cyg J. Montier 12/06/2017 3737 8243 668AG Dra P. Somogyi 10/06/2017 7747 8448 2959 CH Cyg T. Lester 15/06/2017 4045 7755 13000AG Dra J. Guarro 11/06/2017 3980 7761 9000 CH Cyg F. Teyssier 16/06/2017 4208 7160 11000AG Dra P. Somogyi 11/06/2017 3595 7885 668 CH Cyg F. Boubault 17/06/2017 4000 7402 1000AG Dra F. Teyssier 12/06/2017 4208 7160 11000 CH Cyg F. Teyssier 17/06/2017 4208 7160 11000AG Dra W. Sims 13/06/2017 3867 7450 662 CH Cyg P. Somogyi 20/06/2017 3586 7890 660AG Dra F. Teyssier 16/06/2017 4208 7160 11000 CH Cyg J. Foster 22/06/2017 3900 7399 720AG Dra J. Guarro 21/06/2017 4053 7498 9000 CH Cyg T. Lester 22/06/2017 4031 7950 13000AG Dra J. Guarro 03/07/2017 4053 7498 9000 CH Cyg J. Guarro 07/07/2017 4053 7498 9000AG Dra T. Lester 04/07/2017 4031 7950 13000 CH Cyg J. Guarro 09/07/2017 4053 7761 9000AG Dra J. Guarro 05/07/2017 4053 7498 9000 CH Cyg K. Graham 16/07/2017 3603 7405 545AG Dra J. Guarro 14/07/2017 4053 7761 9000 CH Cyg J. Guarro 27/07/2017 4053 7761 9000AG Dra T. Lester 18/07/2017 4031 7950 13000 CH Cyg F. Boubault 28/07/2017 4002 7400 1000AG Dra F. Campos 21/07/2017 3758 7276 775 CH Cyg T. Lester 29/07/2017 4031 7950 13000AG Dra D. Boyd 25/07/2017 3901 7380 930 CH Cyg L. Franco 29/07/2017 3841 7231 532AG Dra J. Guarro 26/07/2017 4053 7761 9000 CH Cyg T. Lester 30/07/2017 4031 7950 15000
CI Cyg F. Teyssier 11/06/2017 4210 7150 11000CI Cyg J. Montier 13/06/2017 3792 8246 668CI Cyg F. Boubault 17/06/2017 4000 7401 1000CI Cyg T. Lester 20/07/2017 4031 7950 13000CI Cyg F. Campos 21/07/2017 3743 7279 703CI Cyg F. Boubault 28/07/2017 4002 7400 1000CI Cyg L. Franco 29/07/2017 3841 7231 530CQ Dra J. Guarro 10/06/2017 4053 7761 9000EG And T. Rodda 20/07/2017 3811 7401 595FN Sgr T. Bohlsen 01/07/2017 3801 7267 1708HM Sge W. Sims 26/06/2017 3867 7450 538IV Vir J. Foster 25/06/2017 3940 7400 875LT Del F. Campos 10/06/2017 3755 7286 873LT Del F. Campos 22/07/2017 3813 7354 683PU Vul J. Foster 23/06/2017 3891 7401 815RS Oph L. Franco 19/06/2017 3841 7231 530RS Oph W. Sims 30/06/2017 3867 7450 622RS Oph K. Graham 06/07/2017 3938 7373 541RW Hya P. Luckas 28/06/2017 3811 7389 536RW Hya P. Luckas 01/08/2017 3800 7399 538T CrB K. Graham 15/06/2017 3682 7388 543T CrB L. Franco 19/06/2017 3841 7231 530T CrB F. Campos 23/06/2017 3851 7371 924T CrB J. Foster 25/06/2017 3941 7400 893T CrB P. Somogyi 29/06/2017 3546 7890 669T CrB L. Franco 03/07/2017 3841 7236 535T CrB T. Lester 06/07/2017 4031 7950 13000T CrB F. Campos 16/07/2017 3756 7297 955V1016 Cyg T. Lester 05/07/2017 4031 7950 13000V1329 Cyg D. Boyd 06/07/2017 3901 7381 764V443 Her L. Franco 19/06/2017 3841 7231 530V627 Cas D. Boyd 24/07/2017 3901 7380 909V934 Her K. Graham 05/06/2017 3603 7404 533V934 Her W. Sims 23/06/2017 3870 7452 563V934 Her K. Graham 27/06/2017 3603 7404 535YY Her W. Sims 04/07/2017 3871 7455 939
Range Range
AG Dra
Coordinates (2000.0)R.A. 16 01 41.0Dec +66 48 10.1Mag V 9.8
SYMBIOTICS
ARAS Eruptive Stars Information Letter 2017-06 - p. 16
"We suggest to continue in such the spectroscopic monitoring of AG Dra with low-ered cadence (at least one R>10000 spectrum per 10-14 day) in the next period. "
AAVSO lightcurve (V: right scale and B-V: left scale) since 2016Spectra obtained in 2017: blue dots on the top of the panel
2017-06-01.877 fteyssier2017-06-03.880 JGF2017-06-05.851 J. Guarro2017-06-09.853 JGF2017-06-11.867 JGF2017-06-12.901 FMTeyssier2017-06-16.899 FMTeyssier2017-06-21.852 J. Guarro2017-07-03.854 J. Guarro2017-07-04.125 tlester2017-07-05.862 J. Guarro2017-07-14.871 JGF2017-07-18.171 tlester2017-07-26.854 JGF
AG Dra
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AG Dra in June-July, 2017 - Echelle spectra
Echelle spectra obtained by Tim Lester, Joan Guarro and F. Teyssier
SYMBIOTICS
ARAS Eruptive Stars Information Letter 2017-06 - p. 21
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AG Dra in June-July, 2017 - Echelle spectra
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AX PerSYMBIOTICS
ARAS Eruptive Stars Information Letter 2017-06 - p. 22
Ongoing campaign upon the request of Augustin SkopalAt least one spectrum a month (high resolution and low resolution, with a cor-rect atmospheric response)
Top : AAVSO V lightcurve since August,2016ARAS Spectra in June-July ,2017:blue dotsBottom : AAVSO V band: green B-V index: blueCH Cygni still brightens (mag V = 7.2 late July)
ARAS Eruptive Stars Information Letter 2017-06 - p. 25
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CH Cyg 2017-07-28 20:56:49 R = 1000 F Boubault
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CH Cyg 2017-06-12 23:32:38 R = 668 Jacques Montier
CH Cyg with ALPY600 (J. Montier) and LISA (F. Boubault)
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CH Cyg 2017-07-16 03:25:56 R = 545 K. Graham
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CH Cyg 2017-07-29 22:08:49 R = 532 L. Franco
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CH Cyg 2017-06-20 20:38:27 R = 660 P. Somogyi
CH Cyg Low res. spectraSYMBIOTICS
ARAS Eruptive Stars Information Letter 2017-06 - p. 26
CH Cyg in 2017SYMBIOTICS
ARAS Eruptive Stars Information Letter 2017-06 - p. 27
Main lines evolution in 2017 from Echelle spectraJoan GuarroTim LesterOlivier GardeFrançois Teyssier
Note the complex behav-iour of [O III]
The emission lines de-crease strongly (He I almost absent) in the spectrum obtained on 2017-07-07 but recover 2 days later
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CHCyg | Ha 6563
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Halpha 2017-06-10
H alpha profile obtained by Christian Kreider at R = 15000 with a Lhires III (2400 l/mm)
Na I D - In the two spectra obtained by Tim Lester on 27 and 29 07-2017 a double absorption (or emission ?) appears in Na I doublet. It disappears in the subsequent spectra (Joan Guarro and Fran-çois Teyssier) for Na I D2 and remains very weak in Na I D1
ARAS Eruptive Stars Information Letter 2017-06 - p. 28
LT Del has been detected in outburst in May by U. Munari & al. (ATel # 10361) - New spectra obtained by Fran Cam-pos.More observations are welcome dur-ing the decline
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ARAS Eruptive Stars Information Letter 2017-06 - p. 35
PU VulSYMBIOTICS
ARAS Eruptive Stars Information Letter 2017-06 - p. 36
A new symbiotic in ARAS database with these flux calibrated spectra of RW Hya obtained by Paul Luckas (Alpy R = 600 )RW Hya is classical symbiotic, discovered as an object with combination spectrum in the same survey than CI Cyg and AX Per (Merrill, 1932)This is an eclipsing object,with a short orbitalperiod (Porb = 370.2±0.9 days), and contains a M2 giant and a hot white dwarf (Kenyon& Mikolajewska 1995).
Its short period makes it a prime candidate for detailed monitoring projects (Kenyon, 1986)
ARAS Eruptive Stars Information Letter 2017-06 - p. 38
ARAS Eruptive Stars Information Letter 2017-06 - p. 46
Campaigns: R AqrSYMBIOTICS
Margarita Karovska requests spectroscopic monitoring of the mira symbiotic R Aqrat least one spectrum a week, low and high resolution, especially H alpha and [OIII] rangeIt is great that there are already observations covering several years.We are having Chandra and HST observations currently scheduled for October 2017.It will be great we we can get photometry and spectroscopy coverage starting soon, and then during the Chandra/HST observations (more dense) and a couple of months after these observations.
ARAS Database for R Aqr: http://www.astrosurf.com/aras/Aras_DataBase/Symbiotics/RAqr.htm
FROM AAVSO Notice#589
August 4, 2017: Dr. Margarita Karovska (Harvard-Smithsonian Center for Astrophysics) has requested "visual, photometric, and spectroscopic observations of the symbiotic variable R Aqr in preparation for and in support of Chandra and HST observations currently scheduled for October 2017."
Dr. Karovska continues: "R Aqr is the nearest symbiotic system at a distance of only about 200 pc. It contains a white dwarf accreting from a mass-losing Mira-type star with binary separation of about 20 AU. The aim of the multiwavelength observations of this fascinating object is to study the physical characteristics of this system and including the multi-scale components of the powerful jet, from the central binary region to the jet-circumbinary material interaction region and beyond.
"AAVSO observations are requested in order to monitor the state of the system and correlate with the satellite observations.
"Visual observations and CCD/PEP observations in the U, B, V, I, J, and H bands are requested." DSLR photometry is also welcome.
"Optical spectroscopy, including in the Halpha, [OIII]5007A region is also requested.
"Also requested is high-speed photometry in U and B bands (a cadence of as low as a few seconds would be ideal, but a cadence of about a minute may also be all right) to reveal any possible high-speed variations in the central binary.
"Weekly observations now through...November would be very much appreciated, with increased fre-quency of observations to twice a week..." beginning four weeks before the Chandra and HST obser-vations and continuing at that frequency until the end of the campaign. "This [level of coverage] will provide solid optical data crucial to interpreting the satellite data."
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V1972 Cyg 2017-06-22 10:34:07 R = 693 James R. Foster
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V1972 Cyg 2017-06-22 10:34:07 R = 693 James R. Foster
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B[e] stars observed by James Forster (V1972 Cyg) and Fran Campos (V2028 Cyg)
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ES Dra 2017-06-24 06:11:25 R = 824 James R. Foster
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FO Aqr 2017-06-25 11:00:19 R = 834 James R. Foster
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ARAS Eruptive Stars Information Letter 2017-06 - p. 50
Spectra of dwarf novae at quiescence by J. Foster
On the stellar wind from hot components in symbiotic binaries Augustin Skopal
In this note on symbiotic stars I will continue my contribution from July 2016 (see ARAS Letter #2016-5), on the stellar wind from cool giants, by a debate on winds from hot components in symbiotic binaries.
As it is well known, the wind from hot components significantly enhances during active phases. The mass-loss rate by the hot star can temporarily reach values that are more than one order of magnitude higher than rates from red giants in symbiotic binaries. With respect to the very high temperature of the central object (pseudophotosphere of the burning white dwarf), the wind will be ionized. As a consequence, this considerably will change the geometrical and radiative properties of the symbiotic nebula. Contribution from such the ionized wind to the emission spectrum both in the continuum and the lines will be determining during active phases. On the other hand, emission from the ionized fraction of the cool giant wind will be negligible, although the mas-sive slow giant’s wind can still play an important role when colliding with the fast wind from the hot component. The wind from the hot component in the spectra of symbiotic stars is best indicated by profiles of emission lines. Already at the beginning of 1980’s of the last century, astronomers noted that there are three main groups of emission lines differing considerably in their width in the spectra of symbiotic no-vae V1016 Cyg and HM Sge. Particularly, first group included narrow lines of mostly iron (the width of ~ 20 km/s), while the second one was represented by extremely broad and intense lines of hydrogen, whose width at the half maximum was around 1000 km/s and their height was around 100 times of the local continuum. Finally, the third group included forbidden lines of highly ionized elements, from [NII] to [FeVII], whose profiles were as broad as ~200 km/s and their profiles at the top were splited into two different components. Figure 1 shows example of such profiles. Large differences in profiles and in the degree of ionization suggest that they are created at very different regions of symbiotic nebula.
Narrow lines
The lines of low-ionized metals, from which lines of one ionized iron FeII are most frequently observed cannot be formed at the vicinity of the hot star. Corresponding transitions require a relatively low temperature, and the kinematic of the hot wind goes far beyond their observed width. From this point of view, probable re-gions of their creation are the outer parts of the gian’s wind that are ionized by radiation from the hot compo-nent. This possibility is supported be their radial velocities at different orbital phases. Their radial velocity curves do not reflect the orbital motion of any from the components, that is, these lines cannot be created at their vi-cinity. For many systems, a low-amplitude wave variation within the orbital motion, but shifted in both the ra-dial velocity and the orbital phase suggest that they are created somwhere in between the binary components.
As concerns to forbidden lines they are produced when an electron jumps from an upper energy level, where it can remain for a long time (so-called meta-stable levels), to a lower level. The lifetime of meta-stable states is of the order of milliseconds to seconds, while that of permitted states is less than a microsec-ond. Therefore, the atom in a meta-stable state has to remain undisturbed long enough to emit the photon via the forbidden transition, which can be realised in a very low-density plasmas. In the opposite case, atom at the meta-stable state can be re-excited to a different (permitted) state by a collision with another atom or photon in a more dense medium, which does not allow the forbidden transition. Since meta-stable states are rather common, forbidden transitions account for a significant percentage of the photons emitted by, e.g., low-density planetary nebulae. In symbiotic nebulae, whose densities can be a few orders of magnitude higher than those of most planetary nebulae, interpretation of forbidden lines is not quite clear, cannot be generalised, and sometimes can be surprising. According to my experience I would note here examples of highly-ionized [FeVII] 608.7 nm line and the [OIII] 495.9 and 500.7 nm nebular lines that are commonly ob-served in the spectra of symbiotic stars. Interpretation of these lines is, in general, problematic. Concerning to [FeVII] transitions, Nussbaumer & Osterbrock (1970, ApJ, 161, 811) concluded that these lines result from
ARAS Eruptive Stars Information Letter 2017-06 - p. 51
collisions with thermal electrons. Iijima (1988, Ap&SS, 150, 235) found that the peaks of strong [FeVII] 608.7 mn emission follow the radial velocity curve of the hot component in AX Per, which implies that a part of the [FeVII] zone has to be located in the vicinity of the hot component. In contrast, Kenyon et al. (2001, AJ, 122, 349) placed the high-ionization emission lines including [FeVII] in AG Peg to 30-300 AU far from the central binary. In the case of Z And, Skopal et al. (2006, A&A, 453, 279) recognized a close similarity between [FeVII] 608.7 and OVI Raman 682.5 nm line profiles, which suggested a similar kinematics for the responsible emit-ting regions, but differing drastically in conditions of ionization. One region has to contain HI atoms at high density, while the other one the Fe+6 ions at a low density. This can be satisfied if these lines are formed within the wind-wind interaction zone. The Raman line can be created at/around the interaction surface from the giant’s side, where its neutral wind is pushed by the hot star wind, while the [FeVII] emission can arise in a collisionally ionized boundary layer between the two winds. As concerns to the nebular N1 and N2 lines ([O III] at 495.9 and 500.7 nm), there are very intense in most of planetary nebulae, whereas in symbiotic stars they are usually seen as faint structured emission fea-tures. For example, the ratio R = F(N1 + N2)/F4363 ~ 100 – 300 represent typical quantities for planetary nebu-lae, while for symbiotic nebulae we measure R ~ 0.5 – 5, which is a result of faint nebular lines originating in a very dense [OIII] nebula. Although ideal densities for [OIII] nebular transitions are of 103 – 104 cm-3, having a critical value around 105 cm-3, they still can be created at significantly higher densities due to a deactivation of nebular transitions leading to weakening of nebular lines. In our first paper on AX Per (Skopal et al, 2001, A&A, 367, 199), using the deactivation factor for [OIII] nebular lines, we estimated electron concentration within the [OIII] nebula to ne ~ 3 x 107 cm-3. Spectroscopic observations made after the major 1989-91 active phase, during the 1994 eclipse, showed that a significant part of flux emitted in the nebular [O III] lines is eclipsed by the stellar disk of the giant, and thus originates in the vicinity of the hot component (see Fig. 2). Thus the [OIII] nebular lines in AX Per can be created in the wind from the hot component. However, during the 2009 active phase, the nebular N1 and N2 lines were not subject to the eclipse (see Fig. 3), in contrast to the 1994 one. Figure 3 shows that also the ratio R, which is a probe of ne and Te in planetary nebulae, was extremely low, imlying a high-density [O III] nebula with ne ([O III]) ~ 107 – 108 cm-3 . How to understand to this strange behaviour of nebular fluxes? The former observations imply that the hot star wind generates (at least) a fraction of the [O III] region. Its location is therefore a function of the mass-loss rate, which deter-mines particle densities at a given distance from the wind source. Higher mass-loss rate places the [O III] zone to larger distances from the hot star and vice versa. During the active phase, the high mass-loss rate of ~ 2 x 10-6 solar masses per year and the terminal velocity of ~ 2000 km/s correspond to the critical densities for creation of nebular lines, ne ([O III]) ~ 107 – 108 cm-3 , at distances > 210 solar radii from the hot star. i.e., far beyond the eclipsed region. However, during quiescence, the mass-loss rate of ~ 10-7 solar masses per year and the terminal velocity of ~ 1600 km/s correspond to the critical radius of ~50 solar radii, which thus can be partially eclipsed by the giant.
Broad lines – a problem of broad Hα wings
Nature of the very broad wings of hydrogen lines of the Balmer series, mainly its strongest Hα line is still a subject to debates. At first glance, the most natural explanation is that the broad Hα wings originate in the ionized wind from the hot component. Accordingly, hydrogen emission lines are created due to cor-responding recombination transitions. As the emitting atoms are accelerated to high velocities, the emitted photons will be significantly Doppler shifted with respect to the reference wavelength (= the wavelength corresponding to the given transition in quiet state). Also the emissivity, which depends on the density of emitting particles, qualitatively agrees with the wing profile: the density and thus the emissivity decreases
On the stellar wind from hot components in symbiotic binaries Augustin Skopal
ARAS Eruptive Stars Information Letter 2017-06 - p. 52
radially from the central source to outside, while the particle velocity increases to the maximal terminal value. Therefore, the wing gradually expires in the noise of the continuum. Its observed maximum broaden-ing defines the terminal velocity of the stellar wind. From observations we know that Hα wings extend to around ± 50 Å, i.e. ± 2300 km/s. Such high velocities are consistent with high luminosity of hot components during active phases. Also a simple quantitative model of the hot component wind supports this idea. The model is based on the hot component ionization structure during active phases – the presence of an optically thick neutral disk around the accretor and a high velocity ionized wind, emitted from its polar regions (see left panel of Fig. 4). This approach simulates bipolar structure of the wind, which is important in explaining the observed symmetry of broad wings around the reference wavelength. The main simplification of the model is assumption that the wind is optically thin. Modelling showed that this rather strong condition is well satisfied for places above the wind origin, at which the wind particles are accelerated to > 200 km/s, be-cause of a high velocity gradient of the wind (see my last contribution in ARAS Letter #2016-05). In practice, this means that a major part of wings extending to more than 2000 km/s is produced by the optically thin part of the wind. In such the case, to reconstruct the profile of broad wings, it is sufficient to redistribute all the visible contributions of the expanding wind according to their radial velocities around the investigated transition. The wing-profile modelling showed a very good agreement with the observed profile from about ±200 km/s up to terminal velocity. Right panel of Fig. 4 shows example of such modelling for the Ha line in the spectrum of Z And during its active phase. As the basis of the model is the continuity equation of the expanding wind from its central source, and the velocity law of the wind (see equations (1) and (2) in ARAS Letter #2016-5), the model determines the accelerating parameter of the wind β and its terminal velocity v∞ . If we know the luminosity of the wings (this requires the distance to the object), the mass-loss rate via the wind dM/dt can be also determined. Modelling of the broad Ha wings during active phases of symbiotic stars showed that their winds are characterized with β= 1.7, vꝏ = 1 600 – 2 600 km/s and dM/dt = a few times (10-7 – 10-6) solar masses per year (https://www.aanda.org/articles/aa/pdf/2006/39/aa4935-06.pdf). However, as it is usual in the science, seemingly natural solution of a problem need not to be unam-biguous and/or cannot be generalised. For example, observations of other objects (e.g. AGB stars or central stars of planetary nebulae) show Ha wings that expand up to 8 000 – 10 000 km/s, which is too much than to be explained by the radiatively driven ionized wind from the central source. Therefore, different pos-sibilities were investigated. Probably the most popular rivaling explanation of broad Ha wings is based on Raman scattering of the Lyβ (1026 Å) photons on neutral atoms of hydrogen. The principle is the same as for well known Raman scattering of OVI 1032 Å photons to the emission band around 6825 Å. However, in the case of Ly-β photons, their Raman scattered counterparts are located around the Ha line, i.e. in its wings. This idea was applied for the first time by korean astronomer H.-W. Lee, who elaborated a quan-titative model of broad Ha wings in symbiotic stars (http://iopscience.iop.org/article/10.1086/312887/pdf). He showed that Ly-β photons are scattered to Ha wings proportionally to the distance Δλ from the reference wavelength as 1/Δλ2. Modelled profiles of broad wings were also in very good agreement with observed ones. It is of interest to note that wing profiles formed in the stellar wind are approxi-mated by the same type of function. Therefore, it is not possible to distinguish between these two pro-cesses only by modelling the line profile, and thus other observational characteristics of the Ha emission have to be considered to identify correct origin of the broad Ha wings in symbiotic binaries. Some exam-ples in favour of the stellar wind model as the nature of the broad wings can be summarized as follows: (i) During the 2000-03 outburst of Z And, the Ha profile considerably broadened, whereas the spec-trum made by FUSE satellite around the optical maximum indicated a decrease of emission in the Ly-β line. (ii) Another support for the wind nature of the broad Ha wings is given by radio observations. During active phases the enhanced wind from the hot component leads to a decrese of the radio emission around wavelengths of 20 cm, because the wind plasma here becomes optically thick, which changes the slope of the energy distribu-
On the stellar wind from hot components in symbiotic binaries Augustin Skopal
ARAS Eruptive Stars Information Letter 2017-06 - p. 53
tion in the radio. Such behaviour of the radio emission was observed during the 2000-03 active phase of Z And. (iii) During eclipses of the hot component by the giant the Ha emission in both the core and the wings decreased considerably, which implies that a significant frac-tion of the broad Hα wings is formed nearby the hot star (example here is in Fig. 2 for AXPer). (iv) Measurements of the radial velocities of the Ha wings revealed that they follow the orbital mo-tion of the hot component in V1329 Cyg, AR Pav, AE Ara, FN Sgr and RS Oph. This implies that the region of the Hα wings formation is connected with the hot star (e.g. https://www.aanda.org/articles/aa/pdf/2009/15/aa11417-08.pdf for RS Oph). Note that Raman scattered photons originate within the neutral part of the wind, i.e. around the cool giant.
These arguments thus suggest that the ionized stellar wind from the hot components in symbiotic binaries represents a dominant source of emission contributing to the Ha wings during active phases. In general, broadening of the line profiles also of other permitted lines is caused by the enhanced wind from the hot components during active phase according to the extension of the zone of their creation around the ionizing source. A nice example is demonstrated by the recent 2015 outburs of AG Peg, elaborated with the aid of numerous your spectra (see https://www.aanda.org/articles/aa/pdf/2017/08/aa29593-16.pdf).
Augustin Skopal
August 8, 2017
Figure 1. Example of narrow and broad emission line profiles in the spectra of symbiotic stars. Forbidden lines of highy-ionized elements (e.g. [FeVII]) can be formed in regions of colliding winds from the cool and hot compo-nent, while the broad wings of hydrogen lines follow the kinematic of the ionized wind from the hot component.
On the stellar wind from hot components in symbiotic binaries Augustin Skopal
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ARAS Eruptive Stars Information Letter 2017-06 - p. 54
Figure 2. Line profiles of He II 468.6, nebular [O III] and Hα lines in the AX Per spectrum observed out of the eclipses (solid and dashed lines) and in the mid of the 1994 eclipse (dotted lines). A significant decrease of the He II, [O III] and Hα fluxes in the eclipse implies that these lines are partly created in the vicinity of the hot star – in its ionized wind.
Figure 4. Left panel: A sketch of the ionization structure of the hot component during active phase (the cut perpen-dicular to the orbital plane containing the white dwarf (black full circle)). Arrows denote the stellar wind from the polar region of the white dwarf pseudophotosphere. Right panel shows example of the corresponding modelled (dashed line) and observed (solid line) Ha line profile during the maximum of the 2000-03 outburst of Z And. Syn-thetic profile fits well the observed wing from around ±200 km/s to the terminal velocity of around ±2 000 km/s.
On the stellar wind from hot components in symbiotic binaries Augustin Skopal
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ARAS Eruptive Stars Information Letter 2017-06 - p. 55
Figure 3. Variation in the selected line flux-es during the 2007-10 active phase of AX Per. The vertical light shadow band vizual-ize the time-interval of the whole eclipse. In contrast to the He II and H I lines, the nebular [O III] lines were not subject to the eclipse as in 1994 (compare Fig. 2).
On the stellar wind from hot components in symbiotic binaries Augustin Skopal
ARAS Eruptive Stars Information Letter 2017-06 - p. 56
Nova Sct 2017 Steve Shore
The sequence you have all produced, shown in this issue of the newsletter, is one of the few sys-tematic sequences I've seen of such high qual-ity - congratulations all - and I hope these com-ments will help you with some interpretation. First, a comment on the rise of novae to maxi-mum light. It's interesting that there are no 2MASS point sources within 5 arcsec of the nova. Some of the charac-teristics of the lines and light curve almost suggest some-thing other than a classical nova. To give you an idea of how this cartoons in a little simulation, the comparison is of To me, one of the really intriguing results of this campaign is the observation of Jul 29 that extends the limit of the echelle observations into the far red. While severely limited by atmospheric atmospheric bands, the spectrum clearly shows the O I 7772 A line in absorption and blueshifted. The line is formed in a very optically thick medium mainly by recombination. The absorption over-laps really well with that on Fe II 5169 and Na I D2, the minimum has vrad ~ 270 km.s-1 but, more importantly, the maximum expansion velocity is about - 470 km s-1. There's no corresponding red wing on either of the neu-tral lines but is present, at a similar velocity, on Fe II and the Balmer sequence with virtually no difference betweenthe structure of the absorption on the Ha and Hb pro-files. In a spectrum two weeks later, Aug. 12, the Balm-er lines have fully developed emission profiles with a red wing extending to 1500 km.s-1and an absorption now at high velocity, -1000 km.s-1. The absorption fea-ture at -500 km.s-1 has remained almost invariant. What is most strange is the change in the Fe II emission pro-files, highlighted in the plots in this issue. In the later spectra, the emission is almost what you'd expect for symmetric, completely optically thick emission profiles formed over a very narrow velocity range. But the ab-sorption at -500 km.s-1 remains on all Balmer transitions. He I 4471, 5876, 6678, and 7065 all show the same high velocity absorption feature, typical of the fireball stage if we assume that the neutral ab-sorption features are associated with the ejecta.Weak absorption at the same high velocity also appeared as early as Jul. 29, perhaps earlier (this depends very much on the S/N ratio which, in your spectra, is over-all superb!). Based on the [O I] 5577, 6300, 6364 lines, it looks like the forbidden oxygen emission is terrestrial and can be used as good checks of the resolution and at-mospheric contributions to the spectra. He I 5105 is the cause of different high velocity structure on Fe II 5018 than the other Fe II lines, there's an absorption trough that blends with the blue edge of the iron line. No C I tran-sition appears to be present in any long wavelength data. So far, in the last spectra, no high ionization lines have yet appeared (e.g. [Ar III], [O III]) and the car-
bon lines, especially C I 6828,7115 and C II 4267, 7235, are not present. It's hard to say at this point what the type is of this nova, whether the C or O dominate, es-pecially with the odd lack of [O I]. That can only mean the density is still high enough that the line is collision-ally de-excited, which implies the number density is well above 108 cm-3. That's interesting in light of the current radius, at least since outburst, if we assume a normal expansion velocity of a few thousand km.s-1.This implies a very high mass for the ejecta, although it's clear that the filling factor must be quite low in light of the structures seen on the emission profiles.The extinction is high; Munari et al. (ATel 10572) men-tion DIBs (diffuse interstellar bands) (along with CH+, which isn't easily distinguished in your spectra) and the 5785, 5792,6613 (among others) are present and strong, a lovely demonstration of the quality of these spectra.
Slow novae have always been a puzzle. On the one hand, it's simple in light of the radiative control of the ionization and thermal structure of the ejecta that slow ejecta will become optically thin on longer time scales and all stages of the spectral development will also be longer duration.But is this because the ejecta are more massive, the ejec-tion velocities lower, the geometry somehow different? There aren't many examples of the slow rise among the historical Galactic novae. This one is too fast to be a so-called "red nova", it's not likely a merger, but the lack of observed X-rays to date (having checked the Swift XRT ob-servations from this last week) is consistent with the ejecta still being quite opaque in soft XRs (and no hard emission has been seen either, not a surprise given the distance). All things considered, the simplest modeling is to use the same procedures I've already described (if anyone is inter-ested I can send pseudocode so you can write this yourself in the language of your choice)for nearly spherical ejecta with the usual assumptions of axial symmetry at some level and ballistic motion. This time, including the change in the relative inner radius (no other geometric changes) changes the relative weighting of the line forming region so you see the Balmer lines coming from a wider region with absorption against the central object not being con-sidered here but, instead, an optically thick inner region.
ARAS Eruptive Stars Information Letter 2017-06 - p. 57
ARAS Eruptive Stars Information Letter 2017-06 - p. 58
Nova Sct 2017 Steve Shore
The models show an example of what you'd expect for nearly spherical ejecta with the ab-sorption coming, mainly, from the innermost portions. Even with an expansion velocity of 2000 km s-1, the thick shell weights the line strongly toward the inner radius. So in these simulations, the Balmer lines are formed over a more extended region, outside the pseu-dophotosphere, and have broader wings and slightly different profiles. The most impor-tant feature of these, as with others I've discussed in other columns, is that the axial sym-metry (even if the ejecta are nearly spherical) produces the particular shape (the peaks) from the optically thin parts of the ejecta (the outer parts). The absorption comes from the denser gas, which in this case is located from about 10% of the maximum radius to 30%.
[O I] 6300 - Nova Sct 2017 2017-08-12. 630 Joan Guarro
O I 7772 A line in absorption and blueshifted. The line is formed in a very optically thick medium main-ly by recombination. The absorption overlaps re-ally well with that on Fe II 5169 and Na I D2, the mini-mum has vrad ~ 270 km.s-1 but, more importantly, the maximum expansion velocity is about - 470 km s-1.
the Balmer lines have fully developed emission profiles with a red wing extending to 1500 km.s-1and an absorp-tion now at high velocity, -1000 km.s-1. The absorption feature at -500 km.s-1 has remained almost invariant
Based on the [O I] 5577, 6300, 6364 lines, it looks like the forbidden oxygen emission is terrestri-al and can be used as good checks of the resolu-tion and atmospheric contributions to the spectra
ARAS Eruptive Stars Information Letter 2017-06 - p. 59
ARAS Eruptive Stars Information Letter 2017-06 - p. 60
The sequences for this B[e] star shows a progressive line profile change that's been seen in other members of this group of stars whose origin, quite simply put, is not clear. As the phrase goes, "that's why it's called `research"'. The red wing, and the shift in the absorption feature on the blue and red sides of the Balmer lines, is not seen on all transitions. For example, in this star the O I 7772 and 8446 Å multiplets show emission that seems stationary about the system radial velocity and a core than also remains stationary but some-times show a displaced absorption feature at almost 150 km/s on the redward side. Or sometimes on the blueward side but usually not. The core depression is really an absorption line, not merely a lack of emis-sion (this has been often interpreted in these stars as a simple disk-like emission prole with two peaks from the orbital motion). That isn't the case here, emission is detected at the same radial velocity for the Paschen lines as the absorption in the Balmer lines. So the absorption in one is pumping emission from the other. This relates directly to the Balmer decrement I've discussed here. The absorption of the high-er lines is weak so the photons escape but it isn't zero. Some self-absorption leads to escape of photons from the de-excitation of the upper levels. This is a process very much like what you see in the Fe curtain stage of novae and will require a bit more time to explain (hence stay tuned). But why the red wing should be the only part that varies, or varies more dramatically, is not obvious. If it's dust, as for novae, it's even harder to explain because in a disk no structure can remain stationary in angle. It may be that the disk is warped, and precessing. Or there may be structures provoked by he presence of a binary star companion. None of these explanations is yet excluded and because this is a stochastic (not always seen) phenom-enon, it's very important to follow it. I'll make the same comment for these stars as for novae. One of the most serious lacunae in our understanding of time variable cosmic phenomena is long term time series. Most ob-servatories (and time allocation committees) lose patience with things that take years. Weather is one thing, access another. Your continued interest in, and monitoring of these stars (and all of the hard work you've been ding) fill gaps, producing a permanent record of long term behavior for which the future will be grateful!
IRAS 17449+2320 and other misdemeanors Steve Shore
ARAS Eruptive Stars Information Letter 2017-06 - p. 61
It's about time we discuss the other tran-sients you're following, supernovae (the joke from a Sidney Harris cartoon about science: a source may not be a supernova but it's a "pretty good nova"). These were originally identified in extragalactic sources when the distances to galaxies, e.g. M 31, were finally understood. Novae had been seen since Curtis ha found them in Andromeda, and Hubble's fa-mous photographic plate showing the Cepheid vari-ations of one star was originally marked as a nova. BuT realizing that there are events of order > 102 times the brightness of classical novae led, rather quickly, to the suggestion of a supernova origin for the Tycho and Kepler events and the association of the Crab Nebula with the event of 1054 (and Bade an Zwicky's suggestion of neutron stars). I'll take some time to go through this material so consider that this is a first installment of what, I hope, will be a more complete discussion of what you can observe and derive from spectra of the different classes. The light curve of a supernova is, however, sim-ilar in some ways to novae. The expansion produces an initial drop that forms an Fe curtain and drives the optical and infrared rise. But that's where the similar-ity ends. Unlike novae, supernovae have an internal source that depends on the event itself, radioactive nuclei mixed into the expanding gas whose decay powers the emission (especially 56Ni and 56Co, both produced by neutron nucleosynthesis in the expand-ing fireball). Additionally, the extreme mass of the ejecta, more than 1 M, means there's a shock mov-ing outward through the gas that's heated it an pro-duced a non-ballistic velocity law for the expansion.The classification is based on the early spectra, when the expanding gas is opaque. Broadly speaking, the spectra divide into two principle types: with and without hydrogen lines. After that, the details be-come important. All SN II, those with Balmer lines as their main P Cyg features, are formed from core col-lapse. Massive stars that follow the "traditional" evo-lutionary route to form a post-oxygen ignition core (more than about 30 M when on the main sequence) produce a neutron star (or black hole) and expel the ejecta by a shock energized by neutrinos emitted from the core. These have comparatively clean environ-ments, although they may have very extended out-er atmospheres that alter the light curve. The main thing is the presence of H as the dominant element.
The Type I are so called because they show no Balm-er lines but may show He. Those coming from mas-sive stars (Ib and Ic) are not the same as the Ia type. The latter is a genuinely "different" beast, I'll return to that in a minute. Those of the Ib an Ic subgroups are thought to originate in the collapse of Wolf-Rayet stars, massive stars that have wind-stripped their en-velopes and still have sufficient mass to undergo core collapse. The distinction between the types is based on whether they show He (Ic) or not (Ib). Among the strongest lines in these spectra you'll nd Si and both O and Ca, although the silicon contributors are the main spectral features (Ia also show these lines).
The type Ia are the particular group of most interest since the finding, in the '60s (by Kowal) of a universality in their maximum brightness. This was ex-tended to a relation between the rate of decline (with of the peak) and the absolute luminosity but the basic result holds. It's this correlation that forms the basis of both the scenario and the intense interest in this class.
The "standard candle" aspect of the Kowal result, culminating in the Hubble Key project to cali-brate the SN Ia against Cepheids (observing Cepheids in galaxies in which Ia events were recorded) and the discovery of cosmic acceleration (and the Nobel prize
Supernova spectra Steve Shore
ARAS Eruptive Stars Information Letter 2017-06 - p. 62
Supernova spectra Steve Shore
nova Project), also leads to the principal element of the originating scenario. White dwarfs, you know, have maximum stable masses and form in the cores of stars sufficiently massive to pass through He core burning. If collapse triggers because this limit, about 1.4 M is somehow exceeded, the result will be an explosion and formation of a neutron star remnant. Thus, the expectation is that the composition of the explosion site is He or heavier element rich and hy-drogen poor or absent. The light curve universality is then explained by the -decay of Co and Fe isotopes mixed into the ejecta that produce a characteristic decay time of a few months. See the open access review https://link.springer.com/article/10.1007/s10509-014-1830-1 for an excellent summary with good pointers to the literature (and not too techni-cal, and contains a wonderful set of spectra, figs.7-13; the appendix on relatively recent supernovae is superb). The light curves are various in all SN, de-pending on ejecta geometry, mixing of the radioac-tive material, and composition. There are dust form-ers, evinced by the changes in the red vs. blue sides of the line profiles as I'd discussed in the last news-letter for novae. Circumstellar material has been de-tected in several SN Ia events (so- called SN Ia-CSM), using absorption lines (like Na I D) and fluoresced Fe II emission (this has been seen in gamma-ray bursts). Some Ia events are thought to be mergers (double de-generate, super-Chandrasekhar mass systems, pos-sibly also rapidly rotating white dwarfs, or systems
undergoing accretion that push them over the edge of stability) while others may be single degenerates. The details of the explosion depend on thermonucle-ar triggers by the expanding shock, and several other channels are proposed for the massive stars. These are sucinly diverse mechanisms that it would be bet-ter to postpone further discussion to another column.One last note for this month. Nearly all classification is now based on automated pattern matching, codes called SNID (for Ia, this was a way of getting redshifts for the host galaxies from template matching), GELA-TO, and PESSTO (for instance), that use a minimal set of parameters to characterize the spectra at differ-ent times of the light curve. The template spectra are based on individual case studies so the classier works with these much as a forensic expert reconstructs a face from pieces. The key point for you all is that the early observations, on the rise and at peak, are the most important distinguishing spectra for superno-vae, especially Ia's. Alpy600 or similar low resolution spectra are just dandy for this. Anything that extends into the red, beyond H, will be important.Galaxies in the NGC, which are usually pret-ty close, have relatively low redshifts but this still pushes the spectrum toward the red end so even Si II 6533 can be shifted beyond 6800 Å if the redshift of the galaxy is 0.05 or more.
ARAS Eruptive Stars Information Letter 2017-06 - p. 63
Astronomer’s Telegram
Continuing spectroscopic monitoring of Nova Sct 2017 = ASASSN-17hx
ATel #10558; Paolo Berardi, Woody Sims, and Umberto Sollecchia (ARAS Group)on 6 Jul 2017; 02:40 UTCredential Certification: S. N. Shore ([email protected])
We report the results of low resolution spectroscopy of the classical nova Sct 2017 = ASASSN-17hx (Atel# 10523, #10524, #10527) as part of the continuing nova monitoring program by members of the ARAS group. Spectra were obtained on 2017 Jun 29.8, Jun 30.3, Jul 1.9, Jul 2.3, Jul 4.3, and Jul. 4.8 with resolutions ranging from about 580 to 2650, depending on the spectrograph (Alpy600, LISA, LHIRES) and covering ~3800-7200A and S/N of about 20-100) with exposure times ranging from 3500 to 10400 sec. The He I spectrum ATel #10527 has persisted but weakened steadily since Jun 24, while after Jun 29 the Fe II 4921, 5018, 5169, among oth-ers, spectrum appeared with P Cyg profiles having maximum velocities around -800 km/s. The absorption troughs have increased in relative strength, from about 10\% on Jun 30 to around 25\% on Jul 4. Halpha showed absorption through Jul 2, at -1000 km/s, with the emission FWZI remained about 3200 km/s. On Jun 29-30, the He I lines showed P Cyg troughs extending to about -800 km/s, as reported previously; the absorp-tion has persisted but both it and the emission have weakened, the profile narrowed, and the maximum ve-locity reduced to about -500 km/s or less. Na I D absorption, likely interstellar, was detected in those spectra with sufficient resolution. No Na I emission was detected but that may increase as the metallic lines develop. N II emission, reported in Atel #10527, was not detected on any of the spectra. The spectra are now those typical of the optically thick, post-fireball stage of the expansion. Observations are continuing, all spectra are publicly available though http://www.astrosurf.com/aras/Aras_DataBase/Novae/2017_NovaSct2017.htm
Please :- respect the procedure- check your spectra BEFORE sending themResolution should be at least R = 500For new transcients, supernovae andpoorly observed objects,SA spectra at R = 100 are welcome
1/ reduce your data into BeSS file format2/ name your file with: _ObjectName_yyyymmdd_hhh_Observer Exemple: _chcyg_20130802_886_toto.fit
3/ send you spectra to Novae, Symbiotics, Cataclysmics : François Teyssier
to be included in the ARAS database
Astronomical Ring for Access to Spectroscopy (ARAS) is an infor-mal group of volunteers who aim to promote cooperation between professional and amateur astronomers in the field of spectroscopy.
To this end, ARAS has prepared the following roadmap:
• Identify centers of interest for spectroscopic observa-tion which could lead to useful, effective and motivating co-operation between professional and amateur astronomers.• Help develop the tools required to transform this cooperation into action (i.e. by publishing spectrograph building plans, organizing group purchasing to reduce costs, developing and validating observa-tion protocols, managing a data base, identifying available resourc-es in professional observatories (hardware, observation time), etc.•Develop an awareness and education policy for amateur astrono-mers through training sessions, the organization of pro/am semi-nars, by publishing documents (web pages), managing a forum, etc.• Encourage observers to use the spectrographs available in mission obser-vatories and promote collaboration between experts, particularly variable star experts.• Create a global observation network.
By decoding what light says to us, spectroscopy is the most productive field in astronomy. It is now entering the amateur world, enabling amateurs to open the doors of astrophysics. Why not join us and be one of the pioneers!
Be Monthly reportPrevious issues : http://www.astrosurf.com/aras/surveys/beactu/index.htm
About ARAS initiative
Submit your spectra to ARAS Eruptive Stars Data Base
ARAS Eruptive Stars Information Letter 2017-06 - p. 64
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