J/A+A/235/185 OT 1809+31 quiescent candidates UBVR photometry (Motch+ 1990)
Quiescent candidates for the repeating optical transient OT 1809+31
Motch C., Hudec R., Christian C.
<Astron. Astrophys. 235, 185 (1990)>
=1990A&A...235..185M 1990A&A...235..185M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Photometry, UBV ; Gamma rays
Keywords: gamma rays: bursts - stars: variable
Abstract:
We have obtained deep U, B, V, and R band CCD images of the field
containing the repeating optical transient discovered by Hudec et al.
(1988, see references). Compared to previously reported optical
studies of this field, the data presented here have a higher
sensitivity and improved spatial resolution. The 30" by 10" error
ellipse derived from the brightest optical flash recorded on 1946
August 31 contains only faint (V>25) galaxies. The upper limit on the
brightness of any stellar object in the error area is U=23.2, B=26.5
and V=25.3. Photometric analysis of all objects present in the whole
CCD field fails to detect any convincingly variable star. Comparing
CCD frames obtained about 10 months apart we derive an upper limit of
∼0.2"/yr on the proper motion of any stellar object brighter than V∼24
and located within 50" from the optical flash position. UBV photometry
reveals that the bluest stellar object present in the CCD frame
(V=22.9, B-V=0.0, U-B=-0.9) is located only ∼9.6' away from the edge
of the error oval and could thus be the quiescent counterpart of the
optical transient if the error ellipse is slightly underestimated or
if the object proper motion is of the order of the upper limit derived
here. Other stellar objects located inside this "proper motion allowed
area" are disc M dwarfs. We present various constraints that our deep
observations put on the nature of the optical transient counterpart
depending on assumed proper motion. We discuss the likely nature of
the UV excess object and its possible connection to the repeating
optical transient and to the class of gamma-ray bursters.
Objects:
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RA (2000) DE Designation(s)
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18 11 20 +31 23.8 OT 19460831 = OTS 1809+31
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2 28 125 Photometric properties of all objects detected
within 1' from the optical transient center
position
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Byte-by-byte Description of file: table2
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Bytes Format Units Label Explanations
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1- 3 I3 --- Id Identification number
5- 9 F5.2 mag Vmag V magnitude
11- 15 F5.2 mag B-V ? B-V colour index
17- 21 F5.2 mag U-B ? U-B colour index (1)
22 A1 --- u_U-B Uncertainty flag on U-B
24- 28 F5.2 --- Gradient Gradient (2)
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Note (1): U-B colour indexes are listed only for objects having U magnitude
brighter than 23.4.
Note (2): Stars have gradient values in the range -0.05 to 0.05. Values smaller
than -0.05 indicate a probable extended image whereas values larger
than 0.05 suggest an image sharper than the mean stellar profile and
the possible presence of a spike.
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History: Prepared via OCR at CDS.
References:
Hudec et al., 1988: Paper presented at the COSPAR/IAU Symposium of
The Physics of Compact Objects: Theory vs. Observations, Sofia, Bulgaria
(End) Marie-Jose Wagner, Patricia Bauer [CDS] 02-May-1997