Table 3.
Spin and orbital frequency derivatives for NGC 1851A for two different reference epochs.
| Reference epoch (MJD) | 53623.155 (Epoch 1) | 53623.155 (Epoch 1) | 59728.338 (Epoch 2) |
|---|---|---|---|
| Epoch of periastron, T0 (MJD) | 53623.15508797(35) | 53623.15508755(33) | 59728.33832689(13) |
| (R19) | (This work) | (This work) | |
| With one orbital period derivative | |||
| Spin frequency, f (Hz) | 200.37770740535 (10) | 200.3777074057 (2) | 200.37770716645 (1) |
| First spin frequency derivative, ḟ (10−17 Hz s−1) | −2.8 (5) | −3.5 (4) | −94.51 (8) |
Second spin frequency derivative,  (10−24 Hz s−2) |
−1.533 (27) | −1.31 (2) | −2.14 (1) |
Third spin frequency derivative,  (10−33 Hz s−3) |
– | −1.57 (8) | −1.57 (8) |
| Orbital period, Pb (day) | 18.785179217(19) | 18.785179201 (2) | 18.785179194 (2) |
| Observed orbital period derivative, Ṗb,obs (10−12 s s−1) | 22 (9) | −1.2 (7) | −1.2 (7) |
| Intrinsic spin period derivative, Ṗint (10−21 s s−1) | – | 4.05 (9) | 26.71 (2) |
| Characteristic age (Gyr) | – | 19.5 (4) | 2.960 (2) |
| With multiple orbital period derivatives | |||
| Spin frequency, f (Hz) | – | 200.3777074057 (2) | 200.37770716645 (1) |
| First spin frequency derivative, ḟ (10−17 Hz s−1) | – | −3.5 (4) | −94.51 (8) |
Second spin frequency derivative,  (10−24 Hz s−2) |
– | −1.31 (2) | −2.14 (2) |
Third spin frequency derivative,  (10−33 Hz s−3) |
– | −1.57 (8) | −1.57 (8) |
Second orbital frequency derivative,  (10−33 Hz s−2) |
– | −4.03 | −6.58 |
Third orbital frequency derivative, (10−42 Hz s−3) |
– | −4.84 | −4.84 |
| Orbital period, Pb (day) | – | 18.785179207 (2) | 18.785179196 (2) |
| Observed orbital period derivative, Ṗb,obs (10−12 s s−1) | – | −5.2 (7) | 2.2 (7) |
| Intrinsic spin period derivative, Ṗint (10−20 s s−1) | – | 1.633 (9) | 1.632 (2) |
| Characteristic age (Gyr) | – | 4.84 (3) | 4.844 (6) |
Notes. The parameters are derived from a modified DDH timing solution, except a) the higher (> 1) order orbital frequency derivatives, which are derived from the spin frequency derivatives and b) the derived parameters below the horizontal lines. The values in the parenthesis indicate 1-σ uncertainties on the last digit.
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