Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userFLAMINGOS-2 infrared photometry of 2I/Borisov
79
0
0.0
(
0
)
Authors
Chien-Hsiu Lee
Ask ChatGPT about the research
No Arabic abstract
2I/Borisov is the second interstellar object (ISO) after Oumuamua (Meech et al. 2017), but differs from Oumuamua drastically with its extensive cometary activity. A key ingredient to understand the nature of this comet is its size. However, due to its cometary activity and extended coma in the optical, only rough estimates and upper limits can be made for 2I/Borisov, ranging in a wide spread from 0.7 to 3.8 km (Guzik et al. 2019; Fitzsimmons et al. 2019; Jewitt, & Luu 2019; Bolin et al. 2019). It has been shown that observations at longer wavelengths (i.e. infrared) are less susceptible to the effects of coma, and can provide a better estimate of the size of the comet nucleus (see, e.g., Fernandez et al. 2013; Bauer et al. 2017). Here we present an estimate of the nucleus of 2I/Borisov from infrared observations by FLAMINGOS-2 on-board the Gemini South telescope (under Fast Turnaround program GS-2019B-FT-207), and infer a comet nucleus size of 1.5 km, comparable to but more stringent than the estimate from Keck AO imaging by Bolin et al. (2019).
rate research
Read More
The composition of comets in the Solar System come in multiple groups thought to encode information about their formation in different regions of the outer protosolar disk. The recent discovery of the second interstellar object, 2I/Borisov, allows for spectroscopic investigations into its gas content and a preliminary classification of it within the Solar System comet taxonomies to test the applicability of planetesimal formation models to other stellar systems. We present spectroscopic and imaging observations from 2019 September 20th to October 26th at the Bok, MMT, and LBT telescopes. We identify CN in the comets spectrum and set precise upper limits on the abundance of C2 on all dates. We use a Haser model to convert our integrated fluxes to production rates and find Q(CN) = 5.0 +/- 2.0 * 10^24 mol/s on September 20th and Q(CN) = 1.1 - 1.9 * 10^24 mol/s on later dates, both consistent with contemporaneous observations. We set our lowest upper limit on a C2 production rate, Q(C2) < 1.6 * 10^23 mol/s, on October 10th. The measured ratio upper limit for that date, Q(C2)/Q(CN) < 0.095 indicates that 2I/Borisov is strongly in the (carbon chain) depleted taxonomic group. The only comparable Solar System comets have detected ratios near this limit, making 2I/Borisov statistically likely to be more depleted than any known comet. Most depleted comets are Jupiter Family Comets, perhaps indicating a similiarity in formation conditions between the most depleted of the JFCs and 2I/Borisov. More work is needed to understand the applicability of our knowledge of Solar System comet taxonomies onto interstellar objects, and we discuss future work that could help clarify the usefulness of the approach.
We present high resolution imaging observations of interstellar comet 2I/Borisov (formerly C/2019 Q4) obtained using the Hubble Space Telescope. Scattering from the comet is dominated by a coma of large particles (characteristic size 0.1 mm) ejected anisotropically. Convolution modeling of the coma surface brightness profile sets a robust limit to the spherical-equivalent nucleus radius r_n < 0.5 km (geometric albedo 0.04 assumed). We obtain an independent constraint based on the non-gravitational acceleration of the nucleus, finding r_n > 0.2 km (nucleus density 500 kg/m3 assumed). The profile and the non-gravitational constraints cannot be simultaneously satisfied if density < 25 kg/m3; the nucleus of comet Borisov cannot be a low density fractal assemblage of the type proposed elsewhere for the nucleus of 1I/Oumuamua. We show that the spin-up timescale to outgassing torques, even at the measured low production rates, is comparable to or shorter than the residence time in the Suns water sublimation zone. The spin angular momentum of the nucleus should be changed significantly during the current solar fly-by. Lastly, we find that the differential interstellar size distribution in the 0.5 mm to 100 m size range can be represented by power laws with indices < 4 and that interstellar bodies of 100 m size scale strike Earth every one to two hundred million years.
2I/Borisov is the first-ever observed interstellar comet (and the second detected interstellar object). It was discovered on 30 August 2019 and has a heliocentric orbital eccentricity of ~ 3.35, corresponding to a hyperbolic orbit that is unbound to the Sun. Given that it is an interstellar object, it is of interest to compare its properties -- such as composition and activity -- with the comets in our Solar System. This study reports low-resolution optical spectra of 2I/Borisov. The spectra were obtained by the MDM observatory Hiltner 2.4m telescope/Ohio State Multi-Object Spectrograph (on 1 and 5 November 2019). The wavelength coverage spanned from 3700A to 9200A. The dust continuum reflectance spectra of 2I/Borisov show that the spectral slope is stepper in the blue end of the spectrum (compared to the red). The spectra of 2I/Borisov clearly show CN emission at 3880A, as well as C2 emission at both 4750A and 5150A. Using a Haser model to covert the observed fluxes into estimates for the molecular production rates, we find Q(CN) = 2.4 +/- 0.2 x 10^24 s^-1, and Q(C2) = 5.5 +/- 0.4 x 10^23 s^-1 at the heliocentric distance of 2.145 au. Our Q(CN) estimate is consistent with contemporaneous observations, and the Q(C2) estimate is generally below the upper limits of previous studies. We derived the ratio Q(C2)/Q(CN) = 0.2 +/- 0.1, which indicates that 2I/Borisov is depleted in carbon chain species, but is not empty. This feature is not rare for the comets in our Solar System, especially in the class of Jupiter Family Comets.
We present Hubble Space Telescope observations of a photometric outburst and splitting event in interstellar comet 2I/Borisov. The outburst, first reported with the comet outbound at 2.8 AU (Drahus et al.~2020), was caused by the expulsion of solid particles having a combined cross-section about 100 sq. km and a mass in 0.1 mm sized particles about 2e7 kg. The latter corresponds to 1e-4 of the mass of the nucleus, taken as a sphere of radius 500 m. A transient ``double nucleus was observed on UT 2020 March 30 (about three weeks after the outburst), having a cross-section about 0.6 sq. km and corresponding dust mass 1e5 kg. The secondary was absent in images taken on and before March 28, and in images taken on and after April 03. The unexpectedly delayed appearance and rapid disappearance of the secondary are consistent with an origin through rotational bursting of one or more large (meter-sized) boulders under the action of outgassing torques, following their ejection from the main nucleus. Overall, our observations reveal that the outburst and splitting of the nucleus are minor events involving a negligible fraction of the total mass: 2I/Borisov will survive its passage through the planetary region largely unscathed.
The discovery of the first active interstellar object 2I/Borisov provides an unprecedented opportunity to study planetary formation processes in another planetary system. In particular, spectroscopic observations of 2I allow us to constrain the composition of its nuclear ices. We obtained optical spectra of 2I with the 4.2 m William Herschel and 2.5 m Isaac Newton telescopes between 2019 September 30 and October 13, when the comet was between 2.5 au and 2.4 au from the Sun. We also imaged the comet with broadband filters on 15 nights from September 11 to October 17, as well as with a CN narrow-band filter on October 18 and 20, with the TRAPPIST-North telescope. Broadband imaging confirms that the dust coma colours (B-V=0.82$pm$0.02, V-R=0.46$pm$0.03, R-I=0.44$pm$0.03, B-R=1.28$pm$0.03) are the same as for Solar System comets. We detect CN emission in all spectra and in the TRAPPIST narrow-band images with production rates between 1.6$times10^{24}$ and 2.1$times10^{24}$ molec/s. No other species are detected. We determine three-sigma upper limits for C$_2$, C$_3$, and OH production rates of 6$times10^{23}$ molec/s, 3$times10^{23}$ molec/s and 2$times10^{27}$ molec/s, respectively, on October 02. There is no significant increase of the CN production rate or A(0)f$rho$ during our observing period. Finally, we place a three-sigma upper limit on the Q(C$_2$)/Q(CN) ratio of 0.3 (on October 13). From this, we conclude that 2I is highly depleted in C$_2$, and may have a composition similar to Solar System carbon-chain depleted comets.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
