Using different Vizier Catalogues in prediction() and Star()
As the current most precise catalog available, Gaia is the default catalog implemented in SORA. Thus, the user can make predictions or adding a star in the occultation procedure by providing the coordinates or the Gaia source ID of the targets. The user can also choose between Gaia-DR2 and Gaia-EDR3 as the source catalog. However, Gaia does not have the brightest stars on the sky in its list, which can be found in Hipparcos, for instance. In other cases, some of the faintest stars are also not available, and may be available in other catalogs.
Regarding this problem, from SORA v0.3 onwards can allow the user to implement any new catalog available on Vizier that can be used in the prediciton() function and the Star() class.
To add a new catalog, the user has to provide the keywords for the necessary parameters allowing SORA to retrieve the correct values.
[1]:
from sora.star.catalog import VizierCatalogue
from astropy.time import Time
from sora import Star
SORA version: 0.3
[2]:
# Defining the NOMAD catalogue from Vizier
nomad = VizierCatalogue(name='NOMAD', cat_path='I/297/out', code='NOMAD1', ra='RAJ2000', dec='DEJ2000',
epoch=Time('J2000'), band={'B': 'Bmag', 'V': 'Vmag', 'R': 'Rmag', 'J': 'Jmag', 'H': 'Hmag', 'K': 'Kmag'})
Note the parameters name (name of the catalogue) and cat_path (path of the catalogue on Vizier) are required parameters for the proper identification of the catalog. The parameters code, ra, dec and epoch are required for a proper identification of the star. The code parameter is a unique identifier within the catalog. In Gaia, for instanca, code="Source".
The parameters for the other astrometric parameters can also be given, like pmra and pmdec for the proper motions PM_RA*COS(DEC) and PM_DEC, parallax and rad_vel for parallax and radial velocity. If not given, these parameters are default to zero. Finally, if the user wants to characterize the stars’ magnitudes, the band parameter can be given by a dictionary with the keywords for all the bands available, as shown for the NOMAD catalog above.
Predicting with new catalog
To predict with a different catalogue than Gaia, just pass the new created VizierCatalogue object to the parameter catalogue in the prediction() function
[3]:
from sora import Body
from sora.prediction import prediction
mars = Body(name='Mars', orbit_class='planet', diameter=6779, ephem='horizons', spkid='499', database=None)
p = prediction(body=mars, time_beg='2022-09-10 00:00', time_end='2022-09-10 06:00', catalogue=nomad)
p.pprint_all()
Ephemeris was split in 1 parts for better search of stars
Searching occultations in part 1/1
Generating Ephemeris between 2022-09-10 00:00:00.000 and 2022-09-10 05:59:00.000 ...
Downloading stars ...
54 NOMAD stars downloaded
Identifying occultations ...
12 occultations found.
Epoch ICRS Star Coord at Epoch Geocentric Object Position C/A P/A Vel Dist B V R J H K long loct M-G-T S-G-T NOMAD Source ID
arcsec deg km / s AU mag mag mag mag mag mag deg hh:mm deg deg
----------------------- ------------------------------ ------------------------------ ------ ------ ------ ------- ------ ------ ------ ------ ------ ------ ---- ----- ----- ----- ---------------
2022-09-10 00:37:10.480 04 37 55.92334 +20 56 19.88016 04 37 55.84499 +20 56 25.91258 6.131 349.69 13.46 0.906 20.750 nan 19.880 nan nan nan 71 05:21 89 96 1109-0056128
2022-09-10 00:39:55.360 04 37 56.13199 +20 56 22.67016 04 37 56.08202 +20 56 26.51681 3.910 349.69 13.46 0.906 nan nan 20.270 nan nan nan 70 05:21 89 96 1109-0056132
2022-09-10 00:45:26.420 04 37 56.38267 +20 56 41.21988 04 37 56.55793 +20 56 27.72996 13.712 169.68 13.46 0.906 17.910 17.060 17.150 14.587 14.015 13.720 69 05:21 89 96 1109-0056134
2022-09-10 01:04:25.900 04 37 58.33666 +20 56 21.05988 04 37 58.19585 +20 56 31.90470 11.023 349.69 13.45 0.906 21.280 nan 19.820 nan nan nan 64 05:21 89 96 1109-0056139
2022-09-10 01:29:09.520 04 38 00.44400 +20 56 28.41000 04 38 00.32811 +20 56 37.33836 9.075 349.69 13.45 0.906 21.050 nan 19.580 nan nan nan 58 05:21 89 96 1109-0056148
2022-09-10 01:34:37.760 04 38 00.78334 +20 56 39.81012 04 38 00.79981 +20 56 38.54023 1.291 169.70 13.45 0.906 19.650 17.970 18.610 16.472 16.437 15.481 57 05:21 88 96 1109-0056152
2022-09-10 02:20:09.040 04 38 04.59353 +20 56 58.59492 04 38 04.72410 +20 56 48.53684 10.223 169.69 13.44 0.906 nan nan nan 17.123 16.219 15.762 45 05:21 88 96 1109-0056165
2022-09-10 02:37:08.420 04 38 06.11633 +20 56 57.82092 04 38 06.18842 +20 56 52.26594 5.646 169.70 13.44 0.906 16.350 15.490 16.100 13.865 13.381 13.213 41 05:21 88 96 1109-0056170
2022-09-10 03:16:45.980 04 38 09.66934 +20 56 55.84992 04 38 09.60305 +20 57 00.95958 5.193 349.70 13.43 0.906 18.350 17.830 18.500 16.449 16.481 15.707 31 05:21 88 96 1109-0056189
2022-09-10 03:32:17.940 04 38 10.97573 +20 57 01.70892 04 38 10.94127 +20 57 04.36582 2.700 349.70 13.43 0.906 14.070 13.250 13.480 10.624 9.952 9.793 27 05:21 87 96 1109-0056199
2022-09-10 04:08:19.700 04 38 14.14934 +20 57 04.20012 04 38 14.04481 +20 57 12.26359 8.195 349.71 13.43 0.906 20.230 nan 19.970 nan nan nan 18 05:21 87 96 1109-0056210
2022-09-10 05:58:45.300 04 38 23.44133 +20 57 44.97984 04 38 23.55198 +20 57 36.44106 8.678 169.71 13.40 0.905 18.350 17.620 18.720 16.246 15.967 15.718 351 05:21 86 96 1109-0056239
If catalogue is not given, then the default catalogue is the Gaia-EDR3. The catalogue parameter can also be “gaiadr2” or “gaiaedr3” as it has been the case since SORA v0.2.
Note that all the bands given to the nomad object were downloaded and included in the PredictionTable. Those stars where a given band is not defined is shown with “Not A Number” (nan) mark.
In order to restrict the prediction function based on a magnitude limit, the user has to define the mag_lim parameter in the prediction() function. Previously to SORA v0.3, only a number could be given to the parameter. Currently, if a number is passed, the limit of magnitude will be defined only for the first band defined. In this example, it is the “B” band. To define which bands are to be limited, the user must pass a dictionary to the mag_lim parameter. For instance, the next piece
of code predicts occultations limiting stars with the V band smaller than 16 and the H band smaller than 14.
[4]:
p = prediction(body=mars, time_beg='2022-09-10', time_end='2022-09-11', catalogue=nomad, mag_lim={'V': 16, 'H': 14})
p.pprint_all()
Ephemeris was split in 1 parts for better search of stars
Searching occultations in part 1/1
Generating Ephemeris between 2022-09-10 00:00:00.000 and 2022-09-10 23:59:00.000 ...
Downloading stars ...
39 NOMAD stars downloaded
Identifying occultations ...
4 occultations found.
Epoch ICRS Star Coord at Epoch Geocentric Object Position C/A P/A Vel Dist B V R J H K long loct M-G-T S-G-T NOMAD Source ID
arcsec deg km / s AU mag mag mag mag mag mag deg hh:mm deg deg
----------------------- ------------------------------ ------------------------------ ------ ------ ------ ------- ------ ------ ------ ------ ------ ------ ---- ----- ----- ----- ---------------
2022-09-10 02:37:08.420 04 38 06.11633 +20 56 57.82092 04 38 06.18842 +20 56 52.26594 5.646 169.70 13.44 0.906 16.350 15.490 16.100 13.865 13.381 13.213 41 05:21 88 96 1109-0056170
2022-09-10 03:32:17.940 04 38 10.97573 +20 57 01.70892 04 38 10.94127 +20 57 04.36582 2.700 349.70 13.43 0.906 14.070 13.250 13.480 10.624 9.952 9.793 27 05:21 87 96 1109-0056199
2022-09-10 12:09:07.580 04 38 55.57073 +20 58 42.82284 04 38 55.38487 +20 58 57.21908 14.630 349.75 13.35 0.904 13.120 12.500 12.970 10.763 10.373 10.215 258 05:20 82 96 1109-0056366
2022-09-10 18:23:28.760 04 39 27.62599 +21 00 06.62004 04 39 27.47466 +21 00 18.37673 11.946 349.78 13.28 0.902 16.220 14.990 14.840 11.974 11.311 11.111 164 05:20 79 96 1110-0056967
Using a not Gaia star in the occultation process
To include a star in the occultation procedure, we must use the Star() class to define a single star. The standard catalogs defined in this class are Gaia-DR2 and Gaia-EDR3. However, we can add a star from a different catalogue defined in Vizier using the VizierCatalogue() class just like we did in the prediction() function. Notice that, in this case, we are not able to use the shortcut of the Occultation() class by providing the direct coordinate of the star. We must define a Star object previously.
[5]:
# The Star class already reads the nomad catalogue to download the magnitudes in the available bands.
# In the case of this example, we must set it to False, or it will download the bands as the main catalogue
# and the auxiliary one, replacing the magnitude with the same values.
s = Star(code='1109-0056199', catalogue=nomad, nomad=False)
print(s)
1 NOMAD star found band={'B': 14.069999694824219, 'V': 13.25, 'R': 13.479999542236328, 'J': 10.62399959564209, 'H': 9.95199966430664, 'K': 9.793000221252441}
star coordinate at J2000.0: RA=4h38m10.97573s +/- 0.0 mas, DEC=20d57m01.7089s +/- 0.0 mas
NOMAD star Source ID: 1109-0056199
ICRS star coordinate at J2000.0:
RA=4h38m10.97573s +/- 0.0000 mas, DEC=20d57m01.7089s +/- 0.0000 mas
pmRA=0.000 +/- 0.000 mas/yr, pmDEC=0.000 +/- 0.000 mas/yr
Plx=0.0000 +/- 0.0000 mas, Rad. Vel.=0.00 +/- 0.00 km/s
Magnitudes: B: 14.070, V: 13.250, R: 13.480, J: 10.624, H: 9.952, K: 9.793
Apparent diameter from Kervella et. al (2004):
V: 0.0660 mas, B: 0.0611 mas
Apparent diameter from van Belle (1999):
sg: B: 0.0596 mas, V: 0.0616 mas
ms: B: 0.0844 mas, V: 0.0579 mas
vs: B: 0.0848 mas, V: 0.0781 mas
Usually, when working with the occultation we want to estimate the uncertainty on the position of the star at the epoch of occultation. For this, the user can provide the list of keywords for the uncertainty of each of the astrometric parameters (if not available, None must be passed for the parameter uncertainty). An important note is that only with the Gaia catalog SORA will obtain the full covariance matrix.
[6]:
nomad = VizierCatalogue(name='NOMAD', cat_path='I/297/out', code='NOMAD1', ra='RAJ2000', dec='DEJ2000', pmra='pmRA', pmdec='pmDE',
epoch=Time('J2000'), band={'B': 'Bmag', 'V': 'Vmag', 'R': 'Rmag', 'J': 'Jmag', 'H': 'Hmag', 'K': 'Kmag'},
errors=['e_RAJ2000', 'e_DEJ2000', 'e_pmRA', 'e_pmDE', None, None])
s = Star(code='1109-0056199', catalogue=nomad, verbose=False, nomad=False)
print(s)
NOMAD star Source ID: 1109-0056199
ICRS star coordinate at J2000.0:
RA=4h38m10.97573s +/- 31.0000 mas, DEC=20d57m01.7089s +/- 17.0000 mas
pmRA=-7.100 +/- 6.400 mas/yr, pmDEC=-16.600 +/- 6.300 mas/yr
Plx=0.0000 +/- 0.0000 mas, Rad. Vel.=0.00 +/- 0.00 km/s
Magnitudes: B: 14.070, V: 13.250, R: 13.480, J: 10.624, H: 9.952, K: 9.793
Apparent diameter from Kervella et. al (2004):
V: 0.0660 mas, B: 0.0611 mas
Apparent diameter from van Belle (1999):
sg: B: 0.0596 mas, V: 0.0616 mas
ms: B: 0.0844 mas, V: 0.0579 mas
vs: B: 0.0848 mas, V: 0.0781 mas
[7]:
from sora import Occultation
occ = Occultation(star=s, body=mars, time='2022-09-10 03:32')
print(occ)
Stellar occultation of star NOMAD 1109-0056199 by Mars.
Geocentric Closest Approach: 3.042 arcsec
Instant of CA: 2022-09-10 03:32:06.900
Position Angle: 349.70 deg
Geocentric shadow velocity: 13.43 km / s
Sun-Geocenter-Target angle: 96.16 deg
Moon-Geocenter-Target angle: 87.36 deg
No observations reported
###############################################################################
STAR
###############################################################################
NOMAD star Source ID: 1109-0056199
ICRS star coordinate at J2000.0:
RA=4h38m10.97573s +/- 31.0000 mas, DEC=20d57m01.7089s +/- 17.0000 mas
pmRA=-7.100 +/- 6.400 mas/yr, pmDEC=-16.600 +/- 6.300 mas/yr
Plx=0.0000 +/- 0.0000 mas, Rad. Vel.=0.00 +/- 0.00 km/s
Magnitudes: B: 14.070, V: 13.250, R: 13.480, J: 10.624, H: 9.952, K: 9.793
Apparent diameter from Kervella et. al (2004):
V: 0.0660 mas, B: 0.0611 mas
Apparent diameter from van Belle (1999):
sg: B: 0.0596 mas, V: 0.0616 mas
ms: B: 0.0844 mas, V: 0.0579 mas
vs: B: 0.0848 mas, V: 0.0781 mas
Geocentric star coordinate at occultation Epoch (2022-09-10 03:32:06.900):
RA=4h38m10.96423s +/- 149.1636 mas, DEC=20d57m01.3323s +/- 70.4248 mas
###############################################################################
Mars
###############################################################################
Object Orbital Class: Planet
Physical parameters:
Diameter:
6779 +/- 0 km
Reference: User,
----------- Ephemeris -----------
EphemHorizons: Ephemeris are downloaded from Horizons website (SPKID=499)
Ephem Error: RA*cosDEC: 0.000 arcsec; DEC: 0.000 arcsec
Offset applied: RA*cosDEC: 0.0000 arcsec; DEC: 0.0000 arcsec