[vsnet-alert 9468] (fwd) Re: R CrB (Renz)
Taichi Kato
tkato at kusastro.kyoto-u.ac.jp
Tue Aug 14 10:32:26 JST 2007
From: "Wolfgang Renz" <w_renz at onlinehome.de>
Subject: Re: [vsnet-alert 9452] R CrB rapid fading apparently stopped
Date: Mon, 13 Aug 2007 08:39:47 +0200
> R CrB rapid fading apparently stopped:
R CrB actually didn't stop fading, since ~ Aug 3rd it seems to have
(just) slowed down its fast fading from ~ 0.4 mag/d (since falling
below ~ 8 mag) to ~ 0.2 mag/d now.
The fading seems to be gray (at least up to now):
- Near maximum
(1982PASP...94..172F: obs mag / 2002A&A...394..617Y: <m>):
U-B =3D ~ 0.07 / 0.06
B-V =3D ~ 0.61 / 0.58
V-R =3D ~ 0.49 / 0.42
V-I =3D ~ 0.70 / 0.18
- At ~ 7 magV (from Simbad UBV data):
U-B =3D ~ 0.3
B-V =3D ~ 0.7
V-I =3D ~ 0.7 (see below)
- At ~ 8.5 magV (see below)
B-V =3D ~ 0.7
V-R =3D ~ 0.4
- At ~ 10.7 magV (see below)
V-R =3D ~ 0.53
The derived color-brightness relations in 2002A&A...394..617Y:
U-B =3D 0.402 * V - 2.31
B-V =3D 0.280 * V - 1.08
V-R =3D 0.301 * V - 1.36
V-I =3D 0.430 * V - 1.94
V-J =3D 0.418 * V - 1.62
for the 5.775-6.025 magV range (due to pulsation) obviously of
course don't hold for fadings.
The lightcurves in the V and J band (probably U to J) look pretty
similar. In L and M band its dominated by the disc. The K band
shows a transit between the two.
Their modelled dust shell itself seems to be faint, but pretty blue:
V ~~ 14.6
U-B ~~ -0.65
B-V ~~ -0.28
V-R ~~ -0.41
R-I ~~ +1:47
(Rayleigh scattering at very small dust grains in UBVR and already
beginning thermal emission of the grains in I)
As black body radiation of ~ 400=B0C starts to be detectable at
below 1100 nm with CCDs, the dust must be pretty warm to
give a significant signal in the I band.
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!=
!!!!!!!!!!!!
Therefore it will be most interesting for amateurs and pros to
observe R CrB (with the available silicon CCDs) in the V and/or
R plus in the I band (at least and especially when it approaches
a very faint minimum (14 magV and fainter when the dust starts
to contribute significantly to the total brightness)).
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!=
!!!!!!!!!!!!
The color excess E(B-V) of R CrB is just 0.05 (Asplund et al. 1997).
Recent R CrB CCD obs
...
20070716.9250 6.14 I MXL.AAVSO HIP77373,HIP77152 None 0.02 Y
20070716.9250 6.746 V MXL.AAVSO HIP77373,HIP77152 None 0.005 Y
20070726.8799 7.78 CV RZD.AAVSO 10.2 USNO A2 0.02 N
20070727.9667 7.89 CV LDS.AAVSO U H BAAVSS 041.03 N
20070729.9215 8.45 CV LDS.AAVSO M H BAAVSS 041.03 N
20070730.2126 8.047 R NMR.AAVSO T 9.51,9.83,10.68,12.1 Not AAVSO 0.0=
2 N MaximDL 9.534,9.782,10.554,12.319
20070730.2133 8.441 V NMR.AAVSO T 9.955,10.198,11.159, Not AAVSO 0.0=
2 N MaximDL 9.925,10.118,11.049,12.667
20070730.2141 9.086 B NMR.AAVSO T 10.630,10.750,11.894 Not AAVSO 0.0=
2 N MaximDL 10.526,10.702,11.823,13.095
20070801.9396 9.58 CV LDS.AAVSO O Q BAAVSS 041.03 N DSLR+AIP4WIN
20070802.8583 9.95 CV RZD.AAVSO 12.2 AAVSO 0.03 N CCD
20070802.9236 10.06 CV LDS.AAVSO O KK BAAVSS 041.03 N DSLR+AIP4WIN
20070803.9401 10.4 V GTZ.AAVSO A 111,102,122 041211 E N
20070804.515 10.55 V Ioh.VSOLJ
20070805.1467 10.64 V DIL.AAVSO O 11.1 070805 0.01 N GRAS-AERO4, 10"=
, 2m-exp
20070805.1548 10.081 R NMR.AAVSO T 9.51,9.83,10.68,12.1 Not AAVSO 0.0=
2 N MaximDL 9.543,9.788,10.556,12.303
20070805.1558 10.603 V NMR.AAVSO T 9.955,10.198,11.159, Not AAVSO 0.0=
2 N MaximDL 9.936,10.144,11.049,12.629
20070805.2586 10.091 R NMR.AAVSO T 9.51,9.83,10.68,12.1 Not AAVSO 0.0=
2 N MaximDL 9.535,9.793,10.555,12.307
20070805.2596 10.601 V NMR.AAVSO T 9.955,10.198,11.159, Not AAVSO 0.0=
2 N MaximDL 9.928,10.134,11.040,12.658
20070805.604 10.75 V Mhh.VSOLJ
20070806.1595 10.263 R NMR.AAVSO T 9.51,9.83,10.68,12.1 Not AAVSO 0.0=
2 N MaximDL 9.549,9.793,10.553,12.294
20070806.1604 10.808 V NMR.AAVSO T 9.955,10.198,11.159, Not AAVSO 0.0=
2 N MaximDL 9.940,10.150,11.054,12.616
20070806.59625 10.95 V Mhh.VSOLJ
20070807.9250 11.42 CV LDS.AAVSO O T BAAVSS 041.03 N DSLR+AIP4WIN
AAVSO LC:
<http://www.aavso.org/cgi-bin/newlcg.pl?name=3DR+CRB&lastdays=3D&start=
=3D2454271.5&stop=3D2454321.5&mag1=3D5.5&mag2=3D12.0&obscode=3D&obstotal=
s=3Don&type=3Dpng&width=3D800&height=3D600&style=3Dpoints&grid=3Don&visu=
alunvalidated=3Don&visualvalidated=3Don&fainterthan=3Don&v=3Don&bband=3D=
on&r=3Don&iband=3Don&uband=3Don&j=3Don&h=3Don&unfiltered=3Don&discrepant=3Do=
n>
vsnet LC:
[vsnet-cvcirc 2079] VSNET CV Circular 2007.6 (up to Jul 09)
... 62(20) 60(21) 62(23) 59(25)
[vsnet-cvcirc 2114] VSNET CV Circular 2007.7 (up to Aug 08)
61(2) 61(3) 62(6) 63(7) 63(8) 63(9) 64(10) 64(11) 66(12)
67(13) 68(14) 68(15) 68(16) 69(17) 69(18) 71(19) 70(20) 70(21)
74(22) 73(23) 74(24) 75(25) 77(26) 79(27) 80(28) 84(29) 87(30)
90(31)
[vsnet-cvcirc 2109] VSNET CV Circular 2007.08 (up to Aug 06)
R CrB (RCB)
94(1) 99(2) 102(3) 106(4) 107(5) 110(6)
vsnet dayly means (UT) of R CrB:
6 7 8
2222222222330000000001111111111222222222233000000000
0123456789011234567890123456789012345678901123456789
58
59 *
60 *
61 **
62 * * *
63 ***
64 **
65
66 *
67 *
68 *** =
69 **
70 **
71 *
72
73 *
74 * *
75 *
76
77 *
78
79 *
80 *
81
82
83
84 *
85
86
87 *
88
89
90 *
91
92
93
94 *
95
96
97
98
99 *
100
101
102 *
103
104
105
106 *
107 *
108
109
110 *
6 7 8
222222222233000000000111111111122222222223300000000
012345678901123456789012345678901234567890112345678
Clear skies
Wolfgang
--
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV =3D WRe.vsnet =3D RWG.AAVSO
More information about the vsnet-alert
mailing list