CN, C2, C3 production rates of Comet C/2020 F3 (NEOWISE) as observed from Himalayan Chandra Telescope, Hanle, India
ATel #13897; Aravind Krishnakumar(Physical Research Laboratory, India), Dorje Angchuk(Indian Institute of Astrophysics), Kumar Venkataramani(Auburn University), Shashikiran Ganesh(Physical Research Laboratory), D K Sahu(Indian Institute of Astrophysics), T Sivarani(Indian Institute of Astrophysics, Athira Unni (Indian Institute of Astrophysics)
on 26 Jul 2020; 18:32 UT
Distributed as an Instant Email Notice Comets
Credential Certification: Shashikiran Ganesh (shashi@prl.res.in)
Optical spectra of comet C/2020 F3 (NEOWISE) were obtained on 22nd and 23rd July using the Hanle Faint Object Spectrograph (HFOSC) mounted on the Himalayan Chandra Telescope (HCT), India, with exposure times of a few minutes.
HCT is located at 78:57:51E, 32:46:46N at an altitude of 4500 m. The comet was tracked using the non-sidereal rate
tracking mode of the telescope. The slit was placed in the East-West orientation, passing through the photo-centre. The spectra of 22nd July (14:48 UT) have been
transferred from the remote location and reduced. They show strong emissions from CN(Δν=0), CN(Δν=-1), C3, C2 (Δν=+1)
and C2 (Δν=0). The production rates for an aperture size of 32,000 km radius were calculated to be Q(CN(Δν=0))=(1.39±0.07)E+28 molec/s, Q(C2 (Δν=0))=(2.37±0.21)E+28 molec/s, Q(C3)=(1.39±0.13)E+27 molec/s indicating a very strong activity.
Other than these emissions commonly seen in other comets, strong spectral feature matching the H2O+(0-5-0) have been
detected at 7467 Å and 7497 Å with a total flux of 3.12E-08 ergs/cm2/s/Å.
DA, the observer on the site, reports that the dust tail (but not the ion tail) was well visible to the naked eye on the nights of the observations. His DSLR photograph of the comet setting over the observatory (night of 23rd July 2020) is posted on the web at the link below.
It shows the ion tail to be quite structured. The images were taken with a 300mm lens mounted on a star tracking mount at about 1.5 km away from the observatory. They were stacked and processed for display. The sodium tail seen by other observers (see eg ATel #13886) is not seen in this photo. It is not very prominent in our spectra, which suggests that the Sodium feature may be short-lived and/or episodic in nature. The redder feature at 7467 and 7497 Å in our spectra are, perhaps, too far into the red to be detected by an unmodified DSLR.
Dorje Angchuk's photo of Comet C/2020 F3 setting over the HCT
