Some thoughts about cometary and ccd photometry comets

Some thoughts about cometary and ccd photometry comets - Transcript

Meeting on Asteroids and Comets in Europe MACE 2006
Vienna May 12 14 2006

Some thoughts about cometary CCD photometry

by Giovanni Sostero and Ernesto Guido
Remanzacco Observatory www afamweb com CARA http cara uai it

Summary

Some issues about comets CCDs photometry Photometry and physical studies of comets The CARA standardization approach Some results Conclusions

Comets are diffuse objects

Which photometric aperture has to be selected for their measurement

Which is the influence of the observing conditions

Comets do have significative proper motions

Stacking of multiple subframes

Need to provide suitable reference stars sequences

Comets are emission line objects

Possibility to use ulfiltered photometry limited amount of objects and or under
particular conditions

Need to use narrowband filters objects with strong emission lines

Possibility to use broadband filters objects with negligible emission lines

Photometry and physical studies of comets

The Afrho connection

What is Afrho

Afrho is a quantity introduced by A Hearn et al in 1984 with the aim of comparing measurements concerning the dust continuum produced under different observing conditions times and instruments The Af is the product of the albedo A filling factor f of grains within the field of view and the linear radius of the field of view at the comet We can consider it only as a proxy of the dust abundance within the coma This means that we cannot establish a simple and secure link between Afrho and the dust production rate

The Afrho quantity is calculated by the ratio between the luminous flux received from the comet and the solar flux Using the following equation Af 2DR 2 Fcom Fsun Where A is the albedo f is the filling factor that is how much the powder grains fill the field of view is the coma radium considered in the measurement usually expressed in cm D is the geocentric distance Earth Comet expressed in cm R is the eliocentric distance expressed in Astronomical Unit Fcom is the observed comet light flux or flow Fsun is the solar flux at 1 AU

CCD comet photometry
Do we really need some kind of filtered photometry

Narrowband Interference Filters

Central Wavelength nm
390 405 430 450 515 620 647 or 650

Molecule
CN C3 CO Blue Dust Continuum C2 H2O Red Dust Continuum

CCD comet photometry
C 2001 Q4 NEAT strong gas contamination

Example of Afrho determinations 1

Comparison with D Schleicher results Lowell Observatory Comet C 2001 Q4 NEAT on May 12 2004 Strong gas contaminations narrowband filter 647nm

Aperture radius 5 000 to 20 000

Lowell Obs 4450 cm

CARA 4320cm

Difference 3

CCD comet photometry
9P Tempel negligible gas contamination

Example of Afrho determinations 2
Comparison with D Schleicher results Lowell Observatory Comet 9P Tempel on May 6 2005 Negligible gas contamination R I broadband photometric filters
Aperture radius 25 000 Km 15 000 Km 10 000 Km Lowell Obs 166 cm 193 cm 234 cm CARA 189 cm 215 cm 245 cm Difference 13 11 5

CCD comet filtered photometry
A standardization tentative from the CARA collaboration WINDOW APERTURE Main window size for aperture photometry 100 000 km comet distance arcsec 138 circular apertures arcsec 122 3 square apertures Multiples and submultiples apertures e g 200 000 Km 50 000 km 25 000 km etc


REFERENCE STARS MAGNITUDES SOURCES Johnson B V Hipparcos Tycho catalogue magnitudes recommended Cousins R I polynomial extrapolation from catalogued B V values 0 1 magn


TARGET Attempt to produce uniform photometry 10 from various observers

Historic roadmap of the CARA collaboration
TA Annual General Meeting September 2001 Basingstoke UK BAA Comet Section Meeting February 2002 London UK
First CCDs filtered lightcurves of comets Presentation of the fixed aperture window technique for CCD photometry

Meeting on Asteroids and Comets in Europe MACE2002 May 2002 Visnjan Croatia
Improvements in photometric methods The first experiments with the Afrho procedure are presented

Meeting on Asteroids and Comets in Europe MACE 2003 May 2003 Mallorca Observatory Spain
Presentation of the CARA collaboration Suggestion about the opportunity of the Afrho procedure approach also for the amateurs

IWCA III June 2004 Paris France
Some observing campaigns results based on the Afrho method are presented

BAA Comet Section Meeting May 2005 Cambridge UK
Discussion about the need to choose some kind of standardization for CCDs comets photometry

Wafrho the CARA workhorse

Developed by Roberto Trabatti CARA

Output tabulated data
0009P 0009P 0009P 0009P 0009P 0009P 0009P 0009P 0009P 0009P 0009P 20050426 86 0 715 1 656 18 85 R 11 51 025580 0000182 00001 HIP Sos 20050426 86 0 715 1 656 18 85 R 11 98 012539 0000241 00002 HIP Sos 20050426 86 0 715 1 656 18 85 R 12 05 011536 0000244 00002 HIP Sos 20050426 86 0 715 1 656 18 85 R 12 12 010533 0000250 00002 HIP Sos 20050426 86 0 715 1 656 18 85 R 12 21 009530 0000256 00002 HIP Sos 20050426 86 0 715 1 656 18 85 R 12 29 008527 0000265 00002 HIP Sos 20050426 86 0 715 1 656 18 85 R 12 40 007524 0000271 00002 HIP Sos 20050426 86 0 715 1 656 18 85 R 12 52 006520 0000281 00002 HIP Sos 20050426 86 0 715 1 656 18 85 R 12 65 005517 0000295 00002 HIP Sos 20050426 86 0 715 1 656 18 85 R 12 83 004514 0000304 00003 HIP Sos 20050426 86 0 715 1 656 18 85 R 13 09 003511 0000309 00003 HIP Sos www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com HIP 64792 G0Vs 0 45m reflector data HIP 64792 G0Vs 0 45m reflector data HIP 64792 G0Vs 0 45m reflector data HIP 64792 G0Vs 0 45m reflector data HIP 64792 G0Vs 0 45m reflector data HIP 64792 G0Vs 0 45m reflector data HIP 64792 G0Vs 0 45m reflector data HIP 64792 G0Vs 0 45m reflector data HIP 64792 G0Vs 0 45m reflector data HIP 64792 G0Vs 0 45m reflector data HIP 64792 G0Vs 0 45m reflector data 0069 45 0069 45 0069 45 0069 45 0069 45 0069 45 0069 45 0069 45 0069 45 0069 45 0069 45

0009P 0009P 0009P 0009P 0009P 0009P 0009P 0009P 0009P 0009P 0009P

20050501 91 0 712 1 637 21 38 R 11 23 049954 0000116 00005 HIP Sos 20050501 91 0 712 1 637 21 38 R 11 53 025532 0000172 00007 HIP Sos 20050501 91 0 712 1 637 21 38 R 11 57 023312 0000181 00007 HIP Sos 20050501 91 0 712 1 637 21 38 R 11 64 021092 0000188 00007 HIP Sos 20050501 91 0 712 1 637 21 38 R 11 71 018872 0000196 00008 HIP Sos 20050501 91 0 712 1 637 21 38 R 11 80 016651 0000206 00008 HIP Sos 20050501 91 0 712 1 637 21 38 R 11 90 014431 0000216 00009 HIP Sos 20050501 91 0 712 1 637 21 38 R 12 03 012211 0000226 00009 HIP Sos 20050501 91 0 712 1 637 21 38 R 12 20 009991 0000238 00009 HIP Sos 20050501 91 0 712 1 637 21 38 R 12 41 007771 0000251 00010 HIP Sos 20050501 91 0 712 1 637 21 38 R 12 73 005550 0000263 00010 HIP Sos

www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com www afamweb com

HIP 63215 G5 HIP 63215 G5 HIP 63215 G5 HIP 63215 G5 HIP 63215 G5 HIP 63215 G5 HIP 63215 G5 HIP 63215 G5 HIP 63215 G5 HIP 63215 G5 HIP 63215 G5

0064 40 0064 40 0064 40 0064 40 0064 40 0064 40 0064 40 0064 40 0064 40 0064 40 0064 40

From theory to practice

Some examples C 2002 T7 LINEAR 97 Tempel 73P Schwassmann Wachmann

Publications so far

The dust environment of comet 67P Churyumov Gerasimenko Fulle M Barbieri C Cremonese G Rauer H Weiler M Milani G Ligustri R Astronomy and Astrophysics v 422 p 357 368 2004

A neck line structure in the dust tail of Comet C 2004 F4 Bradfield
Pansecchi L Scardia M Astronomy and Astrophysics v 430 p 1129 1132 2005

Photometry of comet 9P Tempel 1 during the 2004 2005 approach and the Deep Impact module impact Milani G A Sostero G Trabatti R Ligustri R
Nicolini M Facchini M Tirelli D Carosati D Vinante C and Szabo Gy M Icarus submitted CBET nr 464 473 361 IAUC nr 8668 8660 8659 8658 8557 8543

Conclusions
Some kind of standardization for cometary photometry is needed It s unlikely to establish an all purpose method

Different kind of approaches are possible according to the targets

Different approaches must hopefully converge to comparable results

Cometary CCDs photometry is well suited for amateurs

Acknowledgements
Collaborating astronomers
Marco Fulle Trieste Astronomical Observatory Italy Gian Paolo Tozzi Arcetri Astronomical Observatory Italy Luigi Pansecchi Merate Astronomical Observatory Italy Mauro Barbieri Padova Astronomical Observatory Italy Gyula Szabo University of Szeged Hungary Laurent Jorda Lab d Astrophysique de Marseille France

CARA dedicated staff
Giannantonio Milani Coordinator Carlo Vinante Webmaster Roberto Trabatti Martino Nicolini Mauro Facchini Software

CARA observing stations
Giannantonio Milani Padova Italy Diego Tirelli Vicenza Italy Toni Scarmato S Costantino Briatico Italy Filip Fratev Bulgaria Descartes Observatory Pavia Italy Campo dei Fiori Observatory Varese Italy CAsT Observatory Talmassons Italy Remanzacco Observatory Remanzacco Italy G Montanari Observatory Cavezzo Italy Cor Caroli Observatory Vicenza Italy Armenzano Observatory Perugia Italy Crn Vrh Observatory Crni Vrh Slovenia Terry Lovejoy Brisbane Australia Erik Bryssinck Belgium New Mexico Skies USA