J/ApJ/598/L43 Polarimetry of V838 Mon and stars around (Wisniewski+, 2003)
Evolution of the inner circumstellar envelope of V838 Monocerotis.
Wisniewski J.P., Bjorkman K.S., Magalhaes A.M.
<Astrophys. J., 598, L43-L46 (2003)>
=2003ApJ...598L..43W 2003ApJ...598L..43W
ADC_Keywords: Stars, variable ; Polarization
Keywords: circumstellar matter - stars: individual (V838 Monocerotis) -
techniques: polarimetric
Abstract:
We present imaging polarimetry observations of the eruptive variable
V838 Monocerotis and its neighboring field obtained in 2002 October.
The polarization of field stars confirms the previously determined
interstellar polarization along the line of sight to V838 Mon. While
V838 Mon showed intrinsic polarization shortly after its second
outburst on 2002 February 8, all subsequent observations only showed a
quiescent interstellar polarization component. We find that V838 Mon
once again showed significant intrinsic polarization in 2002 October,
suggesting the presence of an asymmetrical geometry of scattering
material close to the star. Furthermore, an observed 90° position
angle flip in the intrinsic polarization from 2002 February to October
suggests that the distribution of nearby circumstellar material has
experienced significant changes. We discuss the opacity changes in the
evolving circumstellar cloud around V838 Mon that may explain these
observations.
Description:
We obtained polarimetric measurements of V838 Mon and its field in
2002 October at the Cerro Tololo Inter-American Observatory (CTIO)
1.5m telescope.
Objects:
-----------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------
07 04 04.85 -03 50 51.1 V838 Mon
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 71 12 Summary of Our Observations of V838 Mon and
Polarimetric Observations from the Literature
table2.dat 40 50 Filter polarimetry of targets shown in Figure 1a,b
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See also:
J/PAZh/28/764 : UBVR photometry of Nova Mon 2002 (V838 Mon) (Goranskii+, 2002)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Filter Filter
9 A1 --- n_Filter [*] Note on Filter (1)
11- 27 A17 --- Date Observation date (in 2002)
29- 33 F5.3 % Pol Polarisation
35- 39 F5.3 % e_Pol ? rms uncertainty on Pol
41- 45 F5.1 deg PA Position angle
47- 49 F3.1 deg e_PA ? rms uncertainty on PA
51- 55 F5.3 % PolI ? Intrinsic polarisation
57- 61 F5.3 % e_PolI ? rms uncertainty on PolI
63- 67 F5.1 deg PAI ? Intrinsic position angle
71 A1 --- Ref [1-4] Reference (2)
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Note (1): The asterisk denotes a spectropolarimetric observation that
did not span the entire wavelength range of the Johnson V filter;
thus, the V-band polarization for this observation is only an
estimate. Wisniewski et al. (2003ApJ...588..486W 2003ApJ...588..486W) suggested that the
polarization of V838 Mon on 2002 February 13 was purely interstellar
in origin, which the present field star measurements support. We
determined the intrinsic polarization present on 2002 October 2224 by
subtracting the observed polarization on 2002 February 13 from our data.
Note (2): References:
1: Wisniewski et al., 2003ApJ...588..486W 2003ApJ...588..486W
2: This study
3: Giro et al., 2002IAUC.8025....2G 2002IAUC.8025....2G
4: Munari et al., 2002IAUC.8005....2M 2002IAUC.8005....2M
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 I1 h RAh Hour of Right Ascension (J2000)
3- 4 I2 min RAm Minute of Right Ascension (J2000)
6- 7 I2 s RAs Second of Right Ascension (J2000)
9 A1 --- DE- Sign of the Declination (J2000)
10 I1 deg DEd Degree of Declination (J2000)
12- 13 I2 arcmin DEm Arcminute of Declination (J2000)
15- 16 I2 arcsec DEs Arcsecond of Declination (J2000)
18- 19 I2 --- FigRef Label in Figure 1a,b
21 A1 --- Filt Filter
23- 28 F6.3 % Pol Percent polarization
30- 34 F5.3 % e_Pol Error in Pol
36- 40 F5.1 deg PA Position angle
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 19-Dec-2003