C2014Q2

[Joan Guarro Flo]

Hi all:

Leave a graphic on 16 January. I think all we do a good job.

Friendly, Joan.

[umberto sollecchia]

Félicitations à tous pour vos profils: Umberto

[Paolo Berardi]

After Robin and Martin highlighting about comet radial velocity, I tried to compare some spectra in database, finding a significant redshifting after a few days.



Left panel shows two observations close together (around comet approach to Earth) so there was a small Vrad difference (~2 Km/s from ephemeris). Furthermore one of the two spectrum has not an high resolution (R~5000).

On the right, two hi-res spectra (R=11000 and 15000) show very well the Vrad difference between Jan 7 and 13 (~13 Km/s from ephemeris and ~12 Km/s measured averaging some lines). On Jan 13 the comet was moving away from us, then the spectrum redshifted by about 0.26A.

A plot of comet distance from Earth and radial velocity ("delta-dot" of JPL/HORIZONS ephemeris):



During the Earth fly-by, Vrad had the maximum negative value on Nov, 28 (-36.9 Km/s) and will become positive maximum on next Feb, 10 (33.8 Km/s).

Paolo

[Joan Guarro Flo]

Good work Paolo.

Saluti tanti, Joan.

[Olivier Thizy]

Hello,


A very good resources from Nicolas Biver on comet analysis (in french but I suspect it can be understood by all):
http://www.astrosurf.com/jpmasviel/unpe ... comete.pdf


Cordialement,
Olivier Thizy
Vous ne verrez plus des étoiles comme avant !
http://www.shelyak.com/en/

[Paolo Berardi]

Hi all. Joan, Umberto, grazie! Olivier, thank you for Nicolas Biver document (any recommendations for comets absolute flux calibration? Perhaps not an easy task even with the photometric slit...).

Coming back to radial velocity, I try to measure the shift of sun absorption lines on comet observed spectrum, respect to their rest wavelengths (using some Fe I lines) for 13 jan observation, finding a Vrad value around 10 Km/s. Being reflected light, we should consider the Vrad between Sun and comet (~ -5.2 Km/s - from ephemeris - comet was slowly approaching the Sun) and Earth-comet Vrad (~ 14.4 Km/s moving away, eph.). Hoping the reasoning is correct and leave aside other local effects that can occur close to nucleus (what's impact?), observed Vrad should be the sum, 9.2 Km/s, a value not far from measured one.

Some of Fe I lines on comet spectrum and a G2V star rest spectrum:



Paolo

[Paolo Berardi]

Weather continues to be very bad here, so I took the opportunity to reduce an old observation (5 jan)... Just an attempt to capture CN 3880 bands with Lhires III 1200. The two bands are not individually resolved in this R~3200 spectrum:



Rigel in the same spectral interval:



Paolo

[Miguel Rodriguez]

Spectrum from last night with Alpy600.

Cheers
Miguel

[Dubreuil Pierre]

Bonsoir à tous
Good evening everyone

Spectres hier soir Alpy600
Spectrum from last night with Alpy600

C2014q2_20150123_778_Pierre Dubreuil.png (11.17 KiB) Viewed 6979 times

Ce soir, météo mauvaise (un peu de repos !)
Tonight, bad weather (some rest!)

Cdt

Pierre

[Joan Guarro Flo]

Hello:

The Comet in last night.

J.Guarro.