10.4 Source V Magnitude Limits

In the following tables, the screening limits in Table 10.1 are converted into V magnitude limits for a variety of sources. These values are not meant to be a substitute for the ETC, but rather an indication of whether a given object may be near the limit. The most sensitive spectroscopic setting and lowest rate limit (global or local) determine the listed values. Stellar spectra are assumed to be unreddened. Table 10.2 corresponds to spectroscopy through the PSA, Table 10.3 through the BOA, and Table 10.4 to NUV imaging for both apertures.

These tables were calculated for the Cycle 19 COS Instrument Handbook (Version 3.0; December 2010). Due to the decline in the sensitivity of COS over time (TDS), targets that are brighter than the given values by up to 0.5 mag (4.0 to 4.5 mag for the G285M grating) may be within the spectroscopic screening limits. (Limits for imaging are not expected to differ.) Users are required to use the ETC for the final assessment of whether their targets violate the brightness limits.


Table 10.2: V Magnitude Limits for PSA Spectroscopy.

Spectral ClassFUVNUV

G130MG160MG140LG185MG225MG285MG230L
O5 V14.714.015.110.19.58.712.5

O7 V

14.5

13.8

14.9

10.0

9.5

8.6

12.4

O9 V

14.2

13.6

14.7

9.9

9.4

8.5

12.3

B0 V

14.2

13.5

14.6

9.8

9.3

8.4

12.2

B1 V

13.8

13.1

14.3

9.4

9.0

8.2

11.9

B3 V

12.8

12.5

13.4

8.8

8.4

7.7

11.3

B5 V

12.0

11.9

12.7

8.3

8.0

7.4

10.8

B8 V

10.9

11.0

11.5

7.5

7.2

6.7

10.0

A1 V

8.5

8.9

9.3

6.4

6.2

5.8

9.0

A3 V

6.4

7.8

8.3

6.1

6.0

5.6

8.7

A5 V

2.9

6.9

7.3

5.8

5.8

5.5

8.5

F0 V

−0.1

4.9

5.7

4.8

5.2

5.2

7.8

F2 V

−1.2

4.0

5.0

4.5

5.0

5.2

7.6

F5 V

−3.4

1.9

3.2

3.7

4.4

5.0

7.3

F8 V

−4.8

0.5

2.0

3.2

4.1

4.8

7.1

G2 V (Solar)

1.8

−0.5

3.4

1.4

2.7

4.4

6.8

G8 V (Tau Ceti)

3.0

−0.4

4.7

0.5

2.2

3.9

6.4

K2 V (Epsilon Eri)

4.0

−0.1

5.8

−0.8

1.1

3.2

6.1

KM III (Eta Ser)

−1.5

−1.4

0.2

−0.7

1.0

2.9

5.7

KM III (Alpha Boo)

−0.8

−2.3

0.9

−3.1

−1.1

0.9

4.7

KM III (Gamma Aql)

−2.3

−4.5

−0.5

−5.4

−3.9

−2.3

3.8

KM III (HD 146051)

−3.1

−5.0

−1.4

−7.0

−5.1

−3.1

3.3

KM III (Alpha Cet)

0.2

−1.5

1.9

−4.2

−1.9

−1.0

3.3

KM III (HD 123023)

0.0

−1.0

1.6

−3.2

−1.2

−0.3

3.7

KM III (Beta Gru)

−0.2

−0.6

1.5

−2.9

−1.0

0.7

3.4

T ~ 50,000 K Blackbody

14.6

14.0

15.0

10.1

9.5

8.6

12.5

Fλ ~ λ1

11.0

10.6

11.5

7.2

7.2

6.7

9.9

Fλ = const surface brightness

11.1

10.9

11.8

7.7

8.0

7.6

10.7

Fλ = const point source

9.3

9.2

10.0

6.0

6.3

5.9

9.0


Table 10.3: V Magnitude Limits for BOA Spectroscopy.  

Spectral ClassFUVNUV

G130MG160MG140LG185MG225MG285MG230L

O5 V

9.4

8.5

9.8

4.6

3.8

2.8

6.9

O7 V

9.2

8.4

9.6

4.4

3.7

2.7

6.8

O9 V

9.0

8.2

9.4

4.3

3.6

2.7

6.7

B0 V

8.9

8.0

9.3

4.2

3.5

2.6

6.6

B1 V

8.5

7.7

9.0

3.9

3.3

2.4

6.2

B3 V

7.5

7.0

8.1

3.2

2.7

1.9

5.6

B5 V

6.7

6.5

7.4

2.7

2.2

1.5

5.1

B8 V

5.5

5.5

6.2

1.9

1.5

0.8

4.3

A1 V

3.1

3.4

3.8

0.8

0.4

−0.1

3.3

A3 V

1.0

2.2

2.8

0.5

0.2

−0.3

3.0

A5 V

−2.5

1.4

1.8

0.2

0.0

−0.4

2.8

F0 V

−5.6

−0.7

0.1

−0.8

−0.6

−0.7

2.0

F2 V

−6.7

−1.6

−0.6

−1.2

−0.8

−0.8

1.7

F5 V

−8.8

−3.7

−2.4

−2.0

−1.4

−1.0

1.4

F8 V

−10.2

−5.0

−3.6

−2.5

−1.7

−1.1

1.2

G2 V (Solar)

−3.6

−6.1

−1.9

−4.3

−3.1

−1.5

0.8

G8 V (Tau Ceti)

−2.3

−5.9

−0.6

−5.2

−3.6

−2.0

0.3

K2 V (Epsilon Eri)

−1.2

−5.6

0.5

−6.4

−4.7

−2.7

0.1

KM III (Eta Ser)

−6.9

−6.9

−5.2

−6.3

−4.8

−3.1

-0.4

KM III (Alpha Boo)

−6.1

−7.8

−4.4

−8.7

−6.9

−5.1

−1.3

KM III (Gamma Aql)

−7.6

−10.0

−5.9

−11.1

−9.7

−8.2

−2.2

KM III (HD 146051)

−8.5

−10.5

−6.8

−12.6

−10.9

−9.0

−2.8

KM III (Alpha Cet)

−5.1

−7.0

−3.4

−9.7

−7.7

−7.0

−2.8

KM III (HD 123023)

−5.4

−6.5

−3.7

−8.8

−7.0

−6.4

−2.3

KM III (Beta Gru)

−5.6

−6.1

−3.8

−8.6

−6.8

−5.2

−2.6

T~50,000 K Blackbody

9.3

8.5

9.7

4.5

3.7

2.8

6.9

Fλ ~ λ1

5.7

5.1

6.2

1.6

1.4

0.8

4.2

Fλ = const surface brightness

5.8

5.4

6.4

2.2

2.2

1.7

5.0

Fλ = const point source

4.1

3.7

4.6

0.5

0.5

0.0

3.3


Table 10.4: V Magnitude Bright-Object Limits for Imaging.

Spectral ClassPSA+MirrorAPSA+MirrorBBOA+MirrorABOA+MirrorB

O5 V

19.2

16.3

13.5

10.7

O7 V

19.1

16.1

13.4

10.5

O9 V

19.0

16.0

13.3

10.4

B0 V

18.9

15.9

13.2

10.3

B1 V

18.6

15.6

12.9

10.0

B3 V

18.1

15.0

12.4

 9.3

B5 V

17.6

14.5

11.9

 8.9

B8 V

16.9

13.7

11.1

 8.0

A1 V

15.8

12.6

10.1

 6.9

A3 V

15.6

12.3

 9.9

 6.6

A5 V

15.3

12.0

 9.6

 6.2

F0 V

14.7

11.3

 8.9

 5.5

F2 V

14.4

11.0

 8.6

 5.2

F5 V

14.0

10.6

 8.1

 4.7

F8 V

13.7

10.3

 7.8

 4.4

G2 V (Solar)

13.0

 9.6

 7.1

 3.7

G8 V (Tau Ceti)

12.6

 9.1

 6.6

 3.2

K2 V (Epsilon Eri)

11.8

 8.3

 5.8

 2.4

KM III (Eta Ser)

11.4

 8.0

 5.5

 2.0

KM III (Alpha Boo)

 9.6

 6.1

 3.6

 0.2

KM III (Gamma Aql)

 7.1

 3.6

 1.1

–2.3

KM III (HD 146051)

 6.2

 2.7

 0.2

–3.3

KM III (Alpha Cet)

 8.0

 4.6

 2.1

–1.3

KM III (HD 123023)

 8.7

 5.2

 2.7

–0.7

KM III (Beta Gru)

 8.9

 5.5

 3.0

–0.4

T~50,000 K Blackbody

19.2

16.2

13.5

10.6

Fλ ~ λ1

16.8

13.6

11.0

 7.9

Fλ= const surface brightness

10.9

 8.0

 5.1

 2.3

Fλ= const point source

15.8

12.6

10.1

 6.9