Outburst and fading of FN Sgr


(vsnet-alert 236, 1995 Sep. 15, J. Bortle)

The Z And-type star 1848-19a FN Sgr is undergoing an outburst, as indicated by the following observations made by the undersigned:

                date UT       Mag
                -------      -----
FN Sgr         Aug  14.1     13.0
               Aug  20.1     12.9
               Aug  29.1     12.9
               Sep   3.1     12.9
               Sep  12.1     12.4
               Sep  15.1     11.8

This star last experienced an outburst in May/June 1994.

John E. Bortle (AAVSO)

(vsnet-alert 249, J. Bortle)

I also note that the Z And-type star 1848-19a FN Sgr, which recently began an outburst phase, has brightened further during October.

         Sep. 28.1 UT        11.8    (RASNZ/AAVSO Sequence)
              29.1           11.8
              30.0           11.9
         Oct.  1.0           11.9
               3.1           11.8
              10.1           11.5
              12.1           11.5
              13.0           11.5
              14.0           11.5

John E. Bortle (AAVSO)

Fading

(from AAVSO NEWS FLASH No. 27)

FN SAGITTARII

The symbiotic star FN Sgr is fading from the outburst that began in the fall of 1995 (see AAVSO Alert Notice 215) as indicated by the following observations:

                     AAVSO Observer                           AAVSO Observer  
    UT        Mag.     Initials              UT        Mag.     Initials      

APR 18.3      11.8       BRJ             APR 28.0      12.0       OB    
APR 21.0      12.0       OB              MAY 14.9      11.9       MLF   
APR 22.0      12.0       OB              MAY 24.4069   13.1       SQN   
APR 23.0      12.0       OB              MAY 30.101   <13.0       OB    
APR 24.383    12.1       MRV             MAY 30.2042   13.8       BRJ   
APR 27.0      12.0       OB      

Eclipse?

(vsnet-alert 433, T. Kato)

Dear colleagues,

The symbiotic variable FN Sgr is showing a dramatical fading from an outburst (cf. AAVSO NEWS FLASH Nos. 27, 29). Available observations from postings:

    1996 Apr.  2.810  11.9  Has.VSOLJ (N. Hasegawa)
               3.786  11.8  Has.VSOLJ
              11.736  12.0  Has.VSOLJ
              18.3    11.8  BRJ (J. Bortle *1)
              21.0    12.0  OB (D. Overbeek *1)
              22.0    12.0  OB
              23.0    12.0  OB
              24.383  12.1  MRV (R. Medic *1)
              27.0    12.0  OB
              28.0    12.0  OB
         May  14.9    11.9  MLF (B. Monard)
              24.407  13.1  SQN (L. Shaw)
              30.101 <13.0  OB
              30.204  13.8  BRJ
              31.162 <13.0  OB
         Jun.  5.656  13.7  Has.VSOLJ
               6.163  14.5  BRJ

  (*1 from issues of AAVSO NEWS FLASH)

The object stayed at mv~11.8 since last September ( vsnet-alert 236, J. Bortle; vsnet-obs 1188, M. Moriyama; vsnet-obs 1273, S. Kiyota; vsnet-alert 249, J. Bortle).

The current rapid fading may represent an eclipse of the outbursting component by the red giant secondary star, a phenomenon which was most dramatically observed during the latest outbursts of AX Per, V1413 Aql (=AS 338) and FG Ser(=AS 296). Although I am not aware of any orbital ephemeris of this symbiotic binary (does anyone know?), I would like urge observers to closely monitor the object to see if any egress may occur in a month or so. Since evolvement of the eclipse in AX Per was quite rapid, nightly observations would help.

Regards,
Taichi Kato

Photoelectric photometry by Hickel

(vsnet-obs 3431)

Observer : Gabriel Hickel
(e-mail: hickel@das.inpe.br)
Inst. : 60cm Zeiss reflector + Fast Photometer (Hamamatsu R943-02)
LNA Observatory - Brasopolis - Brazil

Date             Object    Magnitude             Colour Index

1996                           V         U-B     B-V     V-R     R-I
(July/UT)                   error      error   error   error   error


26.95268         FN Sgr     13.179     -0.733   1.160   1.250   1.300  
                             0.071      0.252   0.156   0.071   0.030  

26.95981         FN Sgr     13.252     -0.755   1.241   1.233   1.337  
                             0.075      0.266   0.170   0.075   0.030  

27.05160         FN Sgr     12.970     -0.638   1.210   1.092   1.267  
                             0.052      0.186   0.112   0.051   0.023  

27.11263         FN Sgr     13.334     -0.696   0.947   1.269   1.270  
                             0.086      0.231   0.153   0.090   0.060  

27.12113         FN Sgr     12.929     -0.306   0.961   0.998   1.224  
                             0.059      0.223   0.115   0.059   0.031  

27.12286         FN Sgr     12.828     -0.441   1.053   0.950   1.201  
                             0.054      0.213   0.110   0.054   0.029  

27.12465         FN Sgr     12.884     -0.196   0.852   1.008   1.202  
                             0.063      0.205   0.110   0.061   0.025  

27.12646         FN Sgr     12.783     -0.369   0.963   0.919   1.177  
                             0.052      0.215   0.110   0.053   0.030  

27.12824         FN Sgr     12.793     -0.333   0.941   0.914   1.198  
                             0.063      0.209   0.116   0.062   0.033  

27.13234         FN Sgr     12.778     -0.034   0.822   0.904   1.161  
                             0.054      0.201   0.101   0.053   0.025  

27.13409         FN Sgr     12.743     -0.428   1.090   0.885   1.183  
                             0.049      0.202   0.110   0.049   0.027  

27.13580         FN Sgr     12.815     -0.350   0.867   0.937   1.238  
                             0.058      0.181   0.099   0.057   0.027  

27.13763         FN Sgr     12.819     -0.332   0.936   0.945   1.157  
                             0.053      0.219   0.111   0.055   0.029  

27.13946         FN Sgr     12.702     -0.178   0.895   0.863   1.198  
                             0.050      0.197   0.095   0.049   0.027  

27.14123         FN Sgr     12.741     -0.184   1.055   0.919   1.207  
                             0.058      0.209   0.117   0.056   0.025  

27.14305         FN Sgr     12.792     -0.094   1.150   0.951   1.201  
                             0.059      0.274   0.121   0.060   0.033  

27.14498         FN Sgr     12.861     -0.498   1.193   0.988   1.223  
                             0.061      0.222   0.124   0.060   0.027  

Recovery from the minimum

AAVSO NEWS FLASH No. 53 ( AAVSO ftp) reports a siginificant brighetening as cited below. Termination of an eclipse?

FN SAGITTARII

The symbiotic star FN Sgr is brightening as indicated by the following 
observations:
                    AAVSO Observer                           AAVSO Observer  
    UT        Mag.     Initials              UT        Mag.     Initials      

JUL 17.1076   14.1       HAV             AUG 16.1049   12.8       BRJ
JUL 20.1319   13.9       HAV             AUG 19.1292   12.5       BRJ
JUL 21.1375   13.8       HAV             AUG 22.1750   12.8:      SQN
JUL 21.1382   14.3       BRJ             AUG 23.1854   12.8       SQN
AUG 07.2785   12.3:      SQN             AUG 26.0694   12.1       BRJ
AUG 14.181    12.5       MRV    

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