J/AJ/138/845 BVRI observations of 235 bright quasars (Ojha+, 2009)
Photometric observations of selected, optically bright quasars for Space
Interferometry Mission and other future celestial reference frames.
Ojha R., Zacharias N., Hennessy G.S., Gaume R.A., Johnston K.J.
<Astron. J., 138, 845-857 (2009)>
=2009AJ....138..845O 2009AJ....138..845O
ADC_Keywords: QSOs ; Photometry, UBVRI ; Photometry, CCD
Keywords: astrometry - galaxies: photometry - quasars: general -
reference systems
Abstract:
Photometric observations of 235 extragalactic objects that are
potential targets for the Space Interferometry Mission (SIM) are
presented. Mean B, V, R, I magnitudes at the 5% level are obtained at
1-4 epochs between 2005 and 2007 using the 1m telescopes at Cerro
Tololo Inter-American Observatory and the Naval Observatory Flagstaff
Station. Of the 134 sources that have V magnitudes in the Veron &
Veron-Cetty catalog (Cat. VII/248), a difference of over 1.0mag is
found for the observed-catalog magnitudes for about 36% of the common
sources, and 10 sources show over 3mag difference. Our first set of
observations presented here form the basis of a long-term photometric
variability study of the selected reference frame sources to assist in
mission target selection and to support QSO multicolor photometric
variability studies in general.
Description:
With the ultimate goal of selecting suitable, compact, optically
bright QSOs for a future astrometric celestial reference frame that
will be established by a mission like SIM, 242 extragalactic sources
preferably brighter than 16th visual magnitude and with no noticeable
asymmetric structure on the Digitized Sky Survey images as compared to
nearby stellar objects were chosen by visual inspection from the
Veron-Cetty catalog (Veron-Cetty & Veron, 2006, Cat. VII/248,
hereafter VCV06). Photometric observations of these sources were
carried out in the Johnson B, V, R, and I bands and results for 214 of
these sources are presented along with an additional 21 sources which
were observed as part of related observing programs.
Objects in the northern hemisphere were primarily observed with the
Naval Observatory Flagstaff Station (NOFS) 1.0m Ritchey-Chretien
reflector, using a 2k CCD camera during four observing runs between
2005 and 2007. Objects in the southern hemisphere were observed with
the Cerro Tololo Inter-American Observatory (CTIO) Small and Moderate
Aperture Research Telescope System (SMARTS) 1.0m in Chile. The 4kx4k
pixel camera Y4KCam was used and four successful observing runs were
carried out from 2005 through 2007.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 101 390 Magnitudes of Space Interferometry Mission (SIM)
candidate quasars
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See also:
VII/248 : Quasars and Active Galactic Nuclei (12th Ed.) (Veron+ 2006)
VII/258 : Quasars and Active Galactic Nuclei (13th Ed.) (Veron+ 2010)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Source J2000.0 name (HHMM+DDd)
10- 15 F6.3 mag <Bmag> ? Mean B band magnitude
17- 22 F6.3 mag <Vmag> ? Mean V band magnitude
24- 29 F6.3 mag <Rmag> ? Mean R band magnitude
31- 36 F6.3 mag <Imag> ? Mean I band magnitude
38- 42 F5.3 mag e_<Bmag> ? Standard deviation in <Bmag>
44- 48 F5.3 mag e_<Vmag> ? Standard deviation in <Vmag>
50- 54 F5.3 mag e_<Rmag> ? Standard deviation in <Rmag>
56- 60 F5.3 mag e_<Imag> ? Standard deviation in <Imag>
62- 67 F6.3 mag B-V ? The (B-V) color index
69- 74 F6.3 mag V-R ? The (V-R) color index
76- 81 F6.3 mag R-I ? The (R-I) color index
83- 88 F6.3 mag V-I ? The (V-I) color index
90 I1 --- o_<Bmag> Number of observations in <Bmag>
92 I1 --- o_<Vmag> Number of observations in <Vmag>
94- 95 I2 --- o_<Rmag> Number of observations in <Rmag>
97 I1 --- o_<Imag> Number of observations in <Imag>
99-101 A3 --- Epoch Epoch label (1)
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Note (1): Observation summary:
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Label Telescope Epoch Nights
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n51 = NOFS 2005.28 4
n52 = NOFS 2005.66 3
n53 = NOFS 2006.15 3
n54 = NOFS 2007.53 3
c02 = CTIO 2005.86 4
c03 = CTIO 2006.29 4
c05 = CTIO 2006.92 12
c06 = CTIO 2007.15 5
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 16-Jan-2012