Radio observations of different molecular species in comet C/1995 O1(Hale-Bopp) have been carried out regularly since August 1995. We present an analysis of carbon monoxide spectra observed at SEST. ...A detailed picture of the nature of the post-perihelion outgassing at large heliocentric distances is shown. The data starts at 2.9 AU, with active water sublimation, and stretch outside 10 AU, where CO-driven activity is still detected. The activity is studied using a coma model which separates the outgassing into two different sources, one insolation-dependent source, peaking at the subsolar point, and one isotropically outgassing source. Gas velocities and production rates of the two sources are derived for two different cases. In the first case the isotropic source is assumed to be inside the nucleus, and in the second case this source is assumed to be CO-rich material in the coma. Under both assumptions, the results indicate that the two component sources evolve independently. At heliocentric distances around 3 AU, acceleration of the CO molecules in the innermost region of the coma is required for the model to fit the observations. This acceleration must occur at a slower rate than that predicted by hydrodynamic simulations. From 6 to 10 AU, the derived parameters appear remarkably constant. The nuclear outgassing velocity is generally unchanged with heliocentric distance during this wide interval. Observations of molecules other than CO are included in the SEST dataset, and a comparison is made to the modelling results. HCN and CH3OH show signs of being produced in the same way as the CO up to a heliocentric distance of 6 AU.
Comet 9P/Tempel 1 was the target of a multi-wavelength worldwide investigation in 2005. The NASA Deep Impact mission reached the comet on 4.24 July 2005, delivering a 370-kg impactor which hit the ...comet at 10.3 km s
−1. Following this impact, a cloud of gas and dust was excavated from the comet nucleus. The comet was observed in 2005 prior to and after the impact, at 18-cm wavelength with the Nançay radio telescope, in the millimeter range with the IRAM and CSO radio telescopes, and at 557 GHz with the Odin satellite. OH observations at Nançay provided a 4-month monitoring of the outgassing of the comet from March to June, followed by the observation of H
2O with Odin from June to August 2005. The peak of outgassing was found to be around
1
×
10
28
molec.
s
−1
between May and July. Observations conducted with the IRAM 30-m radio telescope in May and July 2005 resulted in detections of HCN, CH
3OH and H
2S with classical abundances relative to water (0.12, 2.7 and 0.5%, respectively). In addition, a variation of the HCN production rate with a period of
1.73
±
0.10
days was observed in May 2005, consistent with the 1.7-day rotation period of the nucleus. The phase of these variations, as well as those of CN seen in July by Jehin et al. Jehin, E., Manfroid, J., Hutsemékers, D., Cochran, A.L., Arpigny, C., Jackson, W.M., Rauer, H., Schulz, R., Zucconi, J.-M., 2006. Astrophys. J. 641, L145–L148, is consistent with a rotation period of the nucleus of 1.715 days and a strong variation of the outgassing activity by a factor 3 from minimum to maximum. This also implies that the impact took place on the rising phase of the “natural” outgassing which reached its maximum ≈4 h after the impact. Post-impact observations at IRAM and CSO did not reveal a significant change of the outgassing rates and relative abundances, with the exception of CH
3OH which may have been more abundant by up to one order of magnitude in the ejecta. Most other variations are linked to the intrinsic variability of the comet. The Odin satellite monitored nearly continuously the H
2O line at 557 GHz during the 38 h following the impact on the 4th of July, in addition to weekly monitoring. Once the periodic variations related to the nucleus rotation are removed, a small increase of outgassing related to the impact is present, which corresponds to the release of
≈
5000
±
2000
tons of water. Two other bursts of activity, also observed at other wavelengths, were seen on 23 June and 7 July; they correspond to even larger releases of gas.
We report on repeated bolometric observations of the Pluto–Charon system at 1.2 mm with the IRAM 30-m telescope. These observations indicate at most small (∼1–2 mJy) variations of the millimeter-wave ...emission of Pluto with orbital longitude, suggesting that the dark regions of Pluto have a millimeter emissivity of ∼0.6–0.7.
Astronomical detection of H2CCC CERNICHARO, J; GOTTLIEB, C. A; GUELIN, M ...
Astrophysical journal/The Astrophysical journal,
02/1991, Letnik:
368, Številka:
2
Journal Article
Recenzirano
Odprti dostop
H2CCC, an isomer of the widely distributed interstellar ring C3H2, has been detected in TMC-1 and possibly IRC + 10216 with the IRAM 30 m telescope, following a recent laboratory determination of the ...rotational spectrum of this new type of highly polar carbon chain. The rotational temperature of H2CCC in TMC-1, like that of other highly polar molecules in this source, is very low: 4-6 K; the column density is also fairly low: (2.5 + or - 0.5) x 10 to the 12th/sq cm, slightly more than 1 percent that of the cyclic isomer. 16 refs.
We present millimeter heterodyne observations of Jupiter performed at the IRAM 30-m telescope during and immediately after the infall of comet Shoemaker–Levy 9 on the planet. Rotational lines of CO ...and CS were first observed in emission during the impacts. They faded rapidly and turned into absorption features after July 28, 1994. The shapes of the lines imply that persistent layers of newly created molecular compounds remained in the upper stratosphere. Modeling of these lines was performed by taking into account the specific geometry of the impact sites. The main results concern: (i) the CO mass at the impact site G 10.5 h after impact, which is found in the range 0.5–
2×10
14
g
, (ii) the CS mass derived on the Q1+R+S complex, which is between 0.9 and
2.5×10
12
g
one week after the impacts, (iii) the temporal evolution of the stratospheric temperature through July and September 1994. Assuming an exponential decrease of the perturbed temperature in the upper stratosphere, a cooling time constant of 29 h is found for the 10-μbar region. Moreover, the temperature near 10-μbar became colder than in pre-impact conditions between 2 and 3 weeks after the impacts, before returning to unperturbed values. Comparison is presented with published temperature evolution models of the SL9 sites.
In July 1994, the collisions of the fragments of comet Shoemaker-Levy 9 with Jupiter resulted in dramatic changes in the planet's atmosphere. Observations of the events suggest that the composition ...and thermal properties of the atmosphere were considerably modified at the impact sites, with the changes persisting for times lasting from minutes to weeks (see, for example, refs 1-4). Here we report observations of the impact sites at millimetre wave-lengths, which reveal strong emission lines associated with carbon monoxide, carbonyl sulphide and carbon monosulphide. The abundance of carbon monoxide in the jovian atmosphere is normally very low; carbonyl sulphide and carbon monosulphide, on the other hand, have not hitherto been detected. We find that the largest fragments (G and K) each produced approximately 10(14) g of carbon monoxide, 3 x 10(12) g of carbonyl sulphide and 3 x 10(11) g of carbon monosulphide, most probably by shock-induced chemical reactions. Our observations also place firm constraints on the thermal response of Jupiter's stratosphere to the impacts.
The apparition of bright comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy) in March-April 2013 and January 2015, combined with the improved observational capabilities of submillimeter facilities, ...offered an opportunity to carry out sensitive compositional and isotopic studies of the volatiles in their coma. We observed comet Lovejoy with the IRAM 30 meter telescope between 13 and 26 January 2015, and with the Odin submillimeter space observatory on 29 January - 3 February 2015. We detected 22 molecules and several isotopologues. The H2 O-16 and H2 O-18 production rates measured with Odin follow a periodic pattern with a period of 0.94 days and an amplitude of approximately 25 percent. The inferred isotope ratios in comet Lovejoy are O-16/O-18 = 499 +/- 24 and D/H equals 1.4 +/- 0.4 x 10(exp -4) in water, S-32/S-34 = equals 24.7 +/- 3.5 in CS, all compatible with terrestrial values. The ratio C-12/C-13 equals 109 +/- 14 in HCN is marginally higher than terrestrial and 14 N/ 15/N equals 145 +/- 12 in HCN is half the Earth ratio. Several upper limits for D/H or C-12/ C-13 in other molecules are reported. From our observation of HDO in comet C/2014 Q2 (Lovejoy), we report the first D/H ratio in an Oort Cloud comet that is not larger than the terrestrial value. On the other hand, the observation of the same HDO line in the other Oort-cloud comet, C/2012 F6 (Lemmon), suggests a D/H value four times higher. Given the previous measurements of D/H in cometary water, this illustrates that a diversity in the D/H ratio and in the chemical composition, is present even within the same dynamical group of comets, suggesting that current dynamical groups contain comets formed at very different places or times in the early solar system.
Detection of Sulfur Monoxide in Io's Atmosphere Lellouch, E; Strobel, D. F; Belton, M. J. S ...
Astrophysical journal/The Astrophysical journal,
03/1996, Letnik:
459, Številka:
2
Journal Article
Millimeter and submillimeter heterodyne observations performed with the IRAM 30-m telescope (Pico Veleta, Spain) and the JCMT (Mauna Kea, Hawaii) have been used to derive the stratospheric ...distribution of carbon monoxide on Titan. Rotational transition lines from12COJ(0 → 1),J(1 → 2),J(2 → 3) at 115.271, 230.538, 345.796 GHz, respectively, as well as theJ(1 → 2) andJ(2 → 3) lines of the13CO isotope at 220.399 and 330.588 GHz, respectively, were recorded with a spectral resolution of 1 MHz. Flux calibration uncertainties were estimated to 10% for all the data. A terrestrial value of the12C/13C ratio has been assumed in the analysis as suggested by T. Hidayatet al. (1997,Icarus126, 170–182) from recent observations of the H12CN(1–0) and H13CN(4–3) lines. The13CO lines sound the 60- to 180-km altitude range, while the12CO lines permit us to probe the atmosphere up to an altitude of about 350 km. Below 180 km, the13CO data impose a constant-with-height CO mixing ratio of ∼2.5 × 10−5. Extending this uniform mixing ratio profile throughout the stratosphere, all the12CO observations could be matched only if the systematic calibration errors were greater than our estimated value by at least a factor of 2. Uncertainties related to the temperature profile adopted in the stratosphere have been also investigated. Taking into account random and systematic uncertainties, the entire set of data indicates a CO mixing ratio equal to 2.9+0.9−0.5× 10−5at 60 km, decreasing to 2.4 ± 0.5 × 10−5at 175 km, and reaching a value of 4.8+3.8−1.5× 10−6at 350 km.
PDF
