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Space Telescope Imaging Spectrograph Instrument Handbook for Cycle 14

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14.8 MAMA Imaging Bright Object Limits

As described in Section 7.6, the MAMA's are subject to absolute brightness limits, above which sources cannot be observed or they would potentially damage the detectors. In Table 14.39, we present the complete set of bright object point source and integrated magnitude screening limits for the MAMA imaging modes. These screening magnitudes are presented as a guide. Whether or not an individual source can be observed is determined by whether the desired configuration and the spectrum of that source is predicted to exceed the global and local absolute observing count rate limits, as described in Chapter 7. Remember, sources cannot be observed in configurations where they exceed the absolute bright object limits. The information presented here should be used in conjunction with the material presented in Chapter 7.

A few important points to note.


Table 14.39: MAMA Bright-Object limits (V magnitudes and cgs units). V magnitudes include an additional safety factor of 3 in flux to account for extrapolation uncertainties from the optical to the UV spectral range.
 
FUV-MAMA
NUV-MAMA
Spectral Type
25MAMA
F25SRF2
F25QTZ
F25LYA
25MAMA
F25SRF2
F25QTZ
F25CN182
F25CIII
F25CN270
F25MGII
Flat, point source1
9.4x10-15
1.7x10-14
4.8x10-14
4.6x10-13
2.0x10-15
2.2x10-15
2.4x10-15
2.6x10-14
1.9x10-13
1.7x10-14
8.4x10-14
Flat, extended, peak2
4.0x10-12
7.2x10-12
2.0x10-11
1.9x10-10
8.8x10-13
9.8x10-13
1.0x10-12
1.1x10-11
7.8x10-11
6.8x10-12
3.4x10-11
O5 V3
20.2
19.4
17.9
16.3
20.3
20.1
19.9
17.9
15.7
17.3
15.3
O7 V
20.0
19.2
17.8
16.1
20.2
20.0
19.8
17.8
15.6
17.2
15.3
O9 V
19.8
19.0
17.6
15.8
20.0
19.9
19.7
17.7
15.5
17.1
15.2
B0 V
19.7
18.9
17.5
15.7
19.9
19.8
19.6
17.6
15.4
17.1
15.1
B1 V
19.4
18.6
17.1
15.4
19.7
19.5
19.3
17.3
15.1
16.9
14.9
B3 V
18.5
17.8
16.4
14.4
19.0
18.9
18.8
16.6
14.4
16.4
14.5
B5 V
17.8
17.2
15.9
13.4
18.6
18.4
18.3
16.2
14.0
16.0
14.1
B8 V
16.7
16.2
15.0
11.7
17.8
17.7
17.6
15.4
13.2
15.3
13.4
A1 V
14.4
14.2
13.4
8.3
16.7
16.6
16.6
14.2
12.1
14.4
12.6
A3 V
13.2
13.0
12.7
6.5
16.5
16.4
16.3
13.9
11.9
14.2
12.4
A5 V
11.9
11.7
11.6
4.5
16.2
16.1
16.1
13.5
11.5
14.0
12.2
F0 V
9.6
9.4
9.4
2.0
15.7
15.6
15.5
12.6
10.5
13.6
11.8
F2 V
8.8
8.6
8.5
1.1
15.4
15.3
15.3
12.2
10.0
13.4
11.7
F5 V
6.8
6.7
6.6
-0.9
15.0
14.9
14.9
11.4
9.1
13.1
11.4
F8 V
5.6
5.4
5.4
<-2.0
14.8
14.7
14.6
10.9
8.5
12.8
11.2
G2 V
4.0
3.9
3.8
<-2.0
14.3
14.3
14.2
10.2
7.8
12.4
10.9
G5 V
3.5
3.4
3.3
<-2.0
14.2
14.1
14.1
10.0
7.6
12.3
10.8
G8 V
2.8
2.6
2.5
<-2.0
13.9
13.8
13.8
9.5
7.3
12.1
10.6
K0 V
1.2
1.0
1.0
<-2.0
13.3
13.3
13.2
8.6
6.8
11.5
10.3
K4 V
<-2.0
<-2.0
<-2.0
<-2.0
11.8
11.7
11.7
6.4
6.0
10.0
9.9
K7 V
<-2.0
<-2.0
<-2.0
<-2.0
11.1
11.0
10.9
5.2
5.5
9.7
9.7
M2 V
<-2.0
<-2.0
<-2.0
<-2.0
10.8
10.7
10.7
4.7
5.4
9.5
9.6
F0 I
10.6
10.4
10.3
3.1
15.3
15.2
15.2
12.5
10.6
13.2
11.5
G5 I
-1.8
-1.9
-1.9
<-2.0
12.1
12.0
12.0
7.0
6.0
10.2
9.9
M2 I
<-2.0
<-2.0
<-2.0
<-2.0
10.2
10.1
10.0
3.1
4.0
9.3
9.4
Integrated V magnitude4
13.4
12.6
11.2
9.6
13.5
13.3
13.1
11.2
8.9
10.5
8.5
Flat, extended, all detector5
7.4x10-15
1.4x10-14
4.0x10-14
3.6x10-17
1.7x10-15
1.9x10-15
2.0x10-15
2.0x10-14
1.5x10-13
1.3x10-14
6.6x10-14
1Maximum allowed flux for a point source in erg s-1 cm-2 Å-1.
2Maximum peak allowed flux for an extended source in erg s-1 cm-2 Å-1 arcsec-2.
3V magnitude limit for unreddened single stars.
4Maximum integrated V magnitude for stars in the field assuming all are of O5 V spectral type.
5Maximum allowed flux for an extended source which covers the full detector in erg s-1 cm-2 Å-1 arcsec-2

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