news on the optical and radio variability of mwc349 gary walker coauthors: elissa sperling, reu...
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News on the Optical and Radio
Variability of MWC349 Gary Walker
CoAuthors: Elissa Sperling, REU Wesleyan Margaret Danielson, RET Nantucket
&Dr. Vladimir Strelnitski
AAVSO Meeting, October 17, 2008
Abstract:
The results of the long-term (11 years) monitoring of MWC349 at optical and radio wavelengths, as well as a recent (summer 2008) experiment of simultaneous optical and radio observations to detect short-term variability, will be summarized. In particular, we will compare the results obtained with the 24-inch CCD telescope of the MMO with those submitted to the AAVSO database by various observers. The revealed amplitudes of MWC349 variations are small – a few tenths of a magnitude for a long-term variations (years) and, typically, less than one tenth for the short-term variations (months to days). This requires a relatively high accuracy photometry, not always achieved in amateur observations. The data obtained so far can be summarized as follows: (1) No obvious periodicity; (2) The amplitude of variations monotonically decreases with the decreasing time scale and towards longer wavelengths; (3) There is correlation of optical (R) and radio (hydrogen recombination line maser) radiation on both a long and short time scales, but the amplitude of the radio variations is greater. Possible interpretation of these results will be discussed. This project was supported by the NSF/REU grant AST-0354056 and the Nantucket Maria Mitchell Association.
Maria Mitchell Association/Observatory
• MMA—10 Buildings, 24 Summer Interns, Astronomy, Natural Science, Education, Marine Science, Library, Curation
• MMO—Astronomy Department– Director Dr. Vladimir Strelnitski
– Telescope Engineer and Astronomer Gary Walker
– Original Prototype of REU Program Started by Dorrit Hoffleit
– 6 Astronomy Majors every Summer are Taught Research
– All write Posters for AAS Meeting in January
– 100 Applicants—Harvard, Columbia, Swathmore, BU, Berkley, Rice
– Projects cover Radio, Optical Observational, and Theoretical
– Prest Grant and Vladimir’s Energy have made MMO a Premier Program
40’ South of the Cyg OB2 center: MWC 349
MWC 349
Comparison Star 134 N
CK4--137
CK1--128
CK2--134
CK3--119
It has been observed in…
• Visible - emission line star (MWC 349)- variable star (V1478 Cyg)
• IR - neutral gas/dust edge-on disk
• Radio, mm, sub mm- ionized disk and outflow; masers and lasers in hydrogen recombination lines
-0.2
-0.1
0
0.1
0.2
0.3
0.4
50500 51000 51500 52000 52500 53000 53500Julian Date (-2400000)
Mag
nitu
de D
iffe
renc
e
I
R
V
R
I
V
Plan (and Proposal) for 2007-08:
MMO plan• Intensify parallel visible and radio monitoring
• Include Hα and IR monitoring
• Observe lasing mid-IR rec. lines from SOFIA and possible X rays from CHANDRA
Proposal• Personal collaboration or making MWC 349 an AAVSO “Star of the Year” for 2007-2008
• Summarize all the results at the AAVSO annual meeting in Nantucket, October 2008 (MMO’s Centennial)
Haw--MWC349--Summer 08
y = 7E-06x2 - 0.0624x + 155.63
R2 = 0.8417
11.35
11.40
11.45
11.50
11.55
11.60
11.65
11.70
11.75
4560 4580 4600 4620 4640 4660 4680 4700 4720 4740 4760
HD - 2450000
Dif
fere
nti
al M
ag
nit
ud
es
MWC349 C124 Avg - 3.05 ( Linear)C 124 Avg -3.05 (Poly) .MWC349
R--MWC349_Summer 08
y = 5E-06x2 - 0.05x + 125.49
R2 = 0.7299
10.55
10.60
10.65
10.70
10.75
10.80
10.85
10.90
10.95
11.00
4560 4580 4600 4620 4640 4660 4680 4700 4720 4740 4760
JD - 2450000
R--
Dif
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ag
s
MWC349 Ck Ensemble Avg - 1.15 (Poly) .MWC349 ( Linear) Ck Ensemble Avg -1.15
Ri--MWC349--Summer 08
y = -1E-05x2 + 0.1124x - 247.7
R2 = 0.2963
13.65
13.70
13.75
13.80
13.85
13.90
13.95
14.00
14.05
4560 4580 4600 4620 4640 4660 4680 4700 4720 4740 4760
JD - 2450000
Dif
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ag
Series1 Series2 ( Linear)Series2 (Poly) .Series1
Haw and Han Comparison; MWC 349
y = -0.0002x + 11.838
R2 = 0.0272
y = 0.0018x + 2.0415
R2 = 0.7021
y = 0.0023x - 0.3151
R2 = 0.9008
10.40
10.45
10.50
10.55
10.60
10.65
10.70
10.75
10.80
4715 4720 4725 4730 4735 4740 4745 4750
JD - 2450000
Dif
fere
nti
al M
ag
Han Ck124 Avg Haw CK 124 Avg ) Linear(Ck 124Avg ) Linear(Haw ) Linear(Han
Comparison of Flat Fielding
y = 0.0024x - 0.6306
R2 = 0.9179
y = 0.0023x - 0.3151
R2 = 0.9008
10.52
10.53
10.54
10.55
10.56
10.57
10.58
10.59
10.60
10.61
10.62
4715 4720 4725 4730 4735 4740 4745 4750
JD - 2450000
Diff
erenti
al
Mag
Han Raw Han FF ) Linear(Han FF ) Linear(Han Raw
AAVSO V Data; MWC349
y = 1E-05x2 - 0.0901x + 221.53
R2 = 0.386
12.75
12.80
12.85
12.90
12.95
13.00
13.05
13.10
13.15
4500 4550 4600 4650 4700 4750 4800
JD - 245550
V D
iffe
ren
tial
Mag
MWC349 Poly. (MWC349)
Data Courtesy AAVSO & Observer Robert James
Air Mass During MWC349 Observations
0.0
0.5
1.0
1.5
2.0
2.5
4560 4580 4600 4620 4640 4660 4680 4700 4720 4740 4760
JD - 2450000
Air
Ma
ss
Air Mass Durring MWC Observations
Air Mass During MWC349 Observations
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
4560 4580 4600 4620 4640 4660 4680 4700 4720 4740 4760
JD - 2450000
Air
Ma
ss
Air Mass Durring MWC Observations
Air Mass Calculator Courtesy Bruce Gary, AXA web site
Possible Spectra
617
618
619
620
621
622
623
624
625
626
627
550 570 590 610 630 650 670 690 710 730
Wavelength (nm)
Re
sp
on
se
Early Summer08 End of Summer 08
Haw & HanRi
Conclusions
• Work in Progress
• Need Nightly Spectra
• May monitor in Sii—(672nm)
• Try Simultaneous Radio and Optical monitoring
• Look at other objects with Ri (645nm) Band
Conclusions
• MWC349 is a unique young object in a transitory evolutionary state (102-103 yrs)
• Masing lines are highly variable indicating fast variations of the central object or local conditions in the disk
• Optical continuum probes the nature of the central object and its closest environment; shows now a secular decline and possible periodicity (a binary? magnetic cycle?)
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