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CUBIC Preliminary Point Source Target List
This page presents a very preliminary list of possible point source targets
for the CUBIC instrument. Although CUBIC is designed
specifically to study the diffuse X-ray background, it can also measure
the spectrum of isolated bright point sources. The design of the
CUBIC field of view permits simultaneous on-source and off-source
measurements by offsetting the pointing direction from the source position;
the spectra in the two CCDs can then be subtracted to obtain the source
spectrum. We estimate the point source sensitivity to be about 30 mCrab,
and expect a count rate from the Crab of about 15 cps. However, it probably
only makes sense to use CUBIC for observations of point sources
too bright to be observed with telescopic observatories like ASCA,
AXAF, or XMM.
In the following table, we give a list of bright X-ray sources that are
possible CUBIC targets. This list is intended to be illustrative,
not definitive. (A definitive target list will be released before launch.)
Bright Point Sources
(data from Catalog of Compact Galactic
X-ray Sources : Bradt, Doxsey, and Jernigan 1979,
Advances in Space Exploration, 3)
Source
Name | Galactic
Longitude |
Galactic
Latitude | Brightness
(mCrabs) |
|---|
| X Per | 163.1 | -17.1 | 11-37 |
| LMC X-2 | 283.1 | -32.7 | 9-44 |
| Crab | 184.6 | -5.8 | 1000 |
| Vela X-1 | 263.1 | 3.9 | <28-280 |
| Cen X-3 | 292.1 | 0.3 | <21-224 |
| Sco X-1 | 359.1 | 23.8 | 6900-19000 |
| 1636-536 | 332.9 | -4.8 | 140-390 |
| GX340+0 | 339.6 | -0.1 | 170-640 |
| Her X-1 | 56.9 | 44.8 | 11-160 |
| 1702-363 | 349.1 | 2.7 | 420-1140 |
| GX9+9 | 8.5 | 9.0 | 175-330 |
| 1735-444 | 346.1 | -7.0 | 110-290 |
| GX3+1 | 2.3 | 0.8 | 220-670 |
| GX5-1 | 5.1 | -1.0 | 530-1400 |
| GX9+1 | 9.1 | 1.2 | 220-670 |
| GX13+1 | 13.5 | 0.1 | 150-450 |
| GX17+2 | 16.4 | 1.3 | 270-1060 |
| 1820-303 | 2.8 | -7.9 | 61-410 |
| Ser X-1 | 36.1 | 4.8 | 140-310 |
| Cyg X-1 | 71.3 | 3.1 | 260-1320 |
| Cyg X-2 | 87.3 | -11.3 | 220-740 |
| Cyg X-3 | 79.9 | 0.7 | 90-430 |
The fields of view for these targets are shown here, superposed on the
University of Wisconsin's MI band all-sky map (galactic coordinates,
centered on the galactic center).
Click on map for full-sized image: 922 x 612 GIF, 199K
For each rectangular box shown on this map, the source is at the box
center. Each target is shown with two overlapping fields of view,
representing the effect of centering the source on CCD1 or on CCD2.
Thus, for the three partitions of each source box, the central partition
represents the field of view of the CCD observing the source, while the
outer boxes represent the possible off-source fields. The target pointing
direction should be selected to use the off-source field providing the
best estimate of the background rate. For example, for Vela X-1
(263, +4), the
upper box should be used for background subtraction, since the lower one
will be contaminated by photons from the Vela supernova remnant (deleted
from this X-ray map because of the high count rate there). Similarly,
for Cygnus
X-2 (87, -11), the lower off-source region should be used, because the
upper one is contaminated by the Cygnus Superbubble.
Most of the galactic
bulge sources probably cannot be observed by CUBIC because the
source density towards the galactic center is too high to permit us
to resolve individual sources (see overlapping source fields at center of
map). This leaves about a dozen sources that
can be observed by CUBIC .
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Ask Us
Last updated March 7, 1996
Web page maintained by
David Burrows
( burrows@astro.psu.edu )
Department of Astronomy and Astrophysics
Penn State University
