scholarly journals New constraints on the physical properties and dynamical history of Centaur 174P/Echeclus

2021 ◽  
Vol 507 (3) ◽  
pp. 3444-3460
Author(s):  
P Rousselot ◽  
A Kryszczyńska ◽  
P Bartczak ◽  
I Kulyk ◽  
K Kamiński ◽  
...  
Keyword(s):  
Dust Emission ◽  
Rotation Period ◽  
Axial Ratio ◽  
Photometric Data ◽  
Spectral Interval ◽  
Rotational Axis ◽  
Orbital Elements ◽  
Active Object ◽  
Dynamical Study ◽  
Short Period

ABSTRACT Since 2005 December, recurrent outbursts have been observed for Centaur 174/P Echeclus, confirming it is an active object. Thanks to a large number of photometric data obtained between 2001 April and 2019 December, we were able to compute a shape model of this object. We obtain a sidereal rotation period P = 26.785178 ± 10−6 h and six equally probable pole solutions, each with a large obliquity of the rotational axis (50° or more). We also find the object significantly elongated, with a semi-major axial ratio a/b = 1.32 (and b/c ∼ 1.1 but this second ratio is poorly constrained by the photometric data). Additionally, we present a detailed analysis of the dust emission from the 2016 outburst. Different colour maps are presented that reveal a change in dust colour, which becomes bluer with increasing cometocentric distance. A blue ring-like structure around the nucleus clearly visible in the images obtained on October 4 in the V-R spectral interval points out that the innermost near nucleus region is considerably redder than the surrounding coma. Different jets are also apparent, the main one being oriented southward. A detailed dynamical study is done to investigate past and future orbital elements. These elements appear stable in the period ≈1200 CE to ≈2900 CE. For a period of 12 000 yr the main conclusion is that Echeclus’ perihelion distance was greater than about 4 au, preventing it from following a typical cometary activity like a short-period comet. Close encounters with giant planets nevertheless prevent any study of orbital elements on longer timescale.

Models of comets with strongly variable nongravitational effects

1999 ◽  
Vol 173 ◽  
pp. 381-387
Author(s):  
M. Królikowska ◽  
G. Sitarski ◽  
S. Szutowicz
Keyword(s):  
Cometary Nucleus ◽  
Spin Axis ◽  
Reactive Force ◽  
Orbital Elements ◽  
Cometary Nuclei ◽  
Short Period ◽  
Basic Parameters ◽  
Polar Radius ◽  
Cometary Activity ◽  
Nongravitational Effects

AbstractThe nongravitational motion of five “erratic” short-period comets is studied on the basis of published astrometric observations. We present the precession models which successfully link all the observed apparitions of the comets: 21P/Giacobini-Zinner, 31P/Schwassmann-Wachmann 2, 32P/Comas Solá, 37P/Forbes, and 43P/Wolf-Harrington. We used the Sekanina's forced precession model of the rotating cometary nucleus to include the nongravitational terms into equations of the comet's motion. Values of six basic parameters (four connected with the rotating comet nucleus and two describing the precession of spin-axis of the nucleus) have been determined along the orbital elements from positional observations of the comets. The solutions were derived with additional assumptions which introduce instantaneous changes of modulus of reactive force,Aand of maximum of cometary activity with respect to perihelion time. The present precession models impose some contraints on sizes and rotational periods of cometary nuclei. According to our solutions the nucleus of 21P/Giacobini-Zinner with oblateness along the spin-axis of about 0.32 (equatorial to polar radius of 1.46) is the most oblate among five investigated comets.

scholarly journals On the 2PN Pericentre Precession in the General Theory of Relativity and the Recently Discovered Fast-Orbiting S-Stars in Sgr A*

Universe ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 37
Author(s):  
Lorenzo Iorio
Keyword(s):  
General Theory ◽  
Present Author ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Orbital Elements ◽  
Analytical Expression ◽  
Potential Interest ◽  
Short Period ◽  
The Future ◽  
Sgr A

Recently, the secular pericentre precession was analytically computed to the second post-Newtonian (2PN) order by the present author with the Gauss equations in terms of the osculating Keplerian orbital elements in order to obtain closer contact with the observations in astronomical and astrophysical scenarios of potential interest. A discrepancy in previous results from other authors was found. Moreover, some of such findings by the same authors were deemed as mutually inconsistent. In this paper, it is demonstrated that, in fact, some calculation errors plagued the most recent calculations by the present author. They are explicitly disclosed and corrected. As a result, all of the examined approaches mutually agree, yielding the same analytical expression for the total 2PN pericentre precession once the appropriate conversions from the adopted parameterisations are made. It is also shown that, in the future, it may become measurable, at least in principle, for some of the recently discovered short-period S-stars in Sgr A*, such as S62 and S4714.

scholarly journals The CARMENES search for exoplanets around M dwarfs

2018 ◽  
Vol 620 ◽  
pp. A171 ◽  
Author(s):  
R. Luque ◽  
G. Nowak ◽  
E. Pallé ◽  
D. Kossakowski ◽  
T. Trifonov ◽  
...  
Keyword(s):  
Bimodal Distribution ◽  
Photometric Data ◽  
M Dwarfs ◽  
Visual Channel ◽  
Low Mass Stars ◽  
Short Period ◽  
Low Mass ◽  
Periodic Signals ◽  
M Stars ◽  
Host Stars

We announce the discovery of two planetary companions orbiting around the low-mass stars Ross 1020 (GJ 3779, M4.0V) and LP 819-052 (GJ 1265, M4.5V). The discovery is based on the analysis of CARMENES radial velocity (RV) observations in the visual channel as part of its survey for exoplanets around M dwarfs. In the case of GJ 1265, CARMENES observations were complemented with publicly available Doppler measurements from HARPS. The datasets reveal two planetary companions, one for each star, that share very similar properties: minimum masses of 8.0 ± 0.5 M⊕ and 7.4 ± 0.5 M⊕ in low-eccentricity orbits with periods of 3.023 ± 0.001 d and 3.651 ± 0.001 d for GJ 3779 b and GJ 1265 b, respectively. The periodic signals around 3 d found in the RV data have no counterpart in any spectral activity indicator. Furthermore, we collected available photometric data for the two host stars, which confirm that the additional Doppler variations found at periods of approximately 95 d can be attributed to the rotation of the stars. The addition of these planets to a mass-period diagram of known planets around M dwarfs suggests a bimodal distribution with a lack of short-period low-mass planets in the range of 2–5 M⊕. It also indicates that super-Earths (>5 M⊕) currently detected by RV and transit techniques around M stars are usually found in systems dominated by a single planet.

scholarly journals Wolf-Rayet binaries: old friends and new acquaintances

1999 ◽  
Vol 193 ◽  
pp. 26-37 ◽  
Author(s):  
Virpi S. Niemela ◽  
Roberto Gamen ◽  
Nidia I. Morrell ◽  
Sixto Giménez Benítez
Keyword(s):  
Radial Velocity ◽  
Binary Systems ◽  
Magellanic Cloud ◽  
Elliptic Orbit ◽  
Spectral Lines ◽  
Small Magellanic Cloud ◽  
Orbital Elements ◽  
Spectroscopic Observations ◽  
Short Period ◽  
Old Friends

Observations of WR stars in binary systems are discussed, emphasizing constraints on our knowledge of the binary frequency of WR stars, and of WR stars as a distinctive class of objects. Radial velocity orbits of newly discovered binaries, e.g., WR 29, a short period WN7+OB binary in our Galaxy, and SMC/AB 7, a massive WN+O7 binary in the Small Magellanic Cloud, are presented. New spectroscopic observations of binary systems with previously known orbits are also reported, showing in the case of WR 21 evidence of change of the orbital elements as derived from different spectral lines. An elliptic orbit for CV Ser is also illustrated.

scholarly journals The EBLM project – VII. Spin–orbit alignment for the circumbinary planet host EBLM J0608-59 A/TOI-1338 A

2020 ◽  
Vol 497 (2) ◽  
pp. 1627-1633 ◽  
Author(s):  
Vedad Kunovac Hodžić ◽  
Amaury H M J Triaud ◽  
David V Martin ◽  
Daniel C Fabrycky ◽  
Heather M Cegla ◽  
...  
Keyword(s):  
Rotation Period ◽  
Primary Component ◽  
High Resolution Spectroscopy ◽  
Spin Orbit ◽  
Primary Star ◽  
Secondary Star ◽  
Short Period ◽  
Low Mass ◽  
Detached Binaries ◽  
Binary Orbit

ABSTRACT A dozen short-period detached binaries are known to host transiting circumbinary planets. In all circumbinary systems so far, the planetary and binary orbits are aligned within a couple of degrees. However, the obliquity of the primary star, which is an important tracer of their formation, evolution, and tidal history, has only been measured in one circumbinary system until now. EBLM J0608-59/TOI-1338 is a low-mass eclipsing binary system with a recently discovered circumbinary planet identified by TESS. Here, we perform high-resolution spectroscopy during primary eclipse to measure the projected stellar obliquity of the primary component. The obliquity is low, and thus the primary star is aligned with the binary and planetary orbits with a projected spin–orbit angle β = 2${_{.}^{\circ}}$8 ± 17${_{.}^{\circ}}$1. The rotation period of 18.1 ± 1.6 d implied by our measurement of vsin i⋆ suggests that the primary has not yet pseudo-synchronized with the binary orbit, but is consistent with gyrochronology and weak tidal interaction with the binary companion. Our result, combined with the known coplanarity of the binary and planet orbits, is suggestive of formation from a single disc. Finally, we considered whether the spectrum of the faint secondary star could affect our measurements. We show through simulations that the effect is negligible for our system, but can lead to strong biases in vsin i⋆ and β for higher flux ratios. We encourage future studies in eclipse spectroscopy test the assumption of a dark secondary for flux ratios ≳1 ppt.

scholarly journals Recent Dynamical History of the Six Short-Period Comets Discovered in 1975

1979 ◽  
Vol 81 ◽  
pp. 293-298 ◽  
Author(s):  
Hans Rickman
Keyword(s):  
Orbital Elements ◽  
Close Encounters ◽  
Short Period ◽  
History Of

In 1975 a remarkably large number of short-period comets were discovered - only the most recent number from 1977 is comparable. While the average discovery rate has been 0.8-1.0 new short-period comets per year (Kresák 1974), in 1975 there were six discoveries. In five of the cases IAU Circulars soon afterwards contained indications that close encounters with Jupiter had recently taken place (Marsden 1975, Kastel' 1975). For two of the comets, P/Kohoutek and P/Smirnova-Chernykh, also pre-encounter orbital elements were outlined, suggesting that substantial reductions of the perihelion distances had occurred.

scholarly journals Determination of the rotational period of the comet 29P/Schwassmann-Wachmann-1 using dynamics of the dust structures (jets) in the coma

2012 ◽  
Vol 10 (H16) ◽  
pp. 176-176
Author(s):  
Aleksandra Ivanova ◽  
Viktor Afanasiev ◽  
Pavlo Korsun ◽  
Aleksandr Baransky ◽  
Maksim Andreev ◽  
...  
Keyword(s):  
Digital Filters ◽  
Cross Correlation ◽  
Rotation Period ◽  
Correlation Method ◽  
Photometric Data ◽  
Rotational Period ◽  
Water Ice ◽  
Ice Sublimation ◽  
Made In

AbstractWe present analysis of the photometric data of the distant comet 29P/Schwassmann-Wachmann-1, obtained at the 6-m BTA telescope (SAO RAS, Russia) and at the 2-meter telescope Zeiss-2000 (ICAMER, KB). The comet shows significant jets activity at large heliocentric distances, beyond the zone of water ice sublimation. Various digital filters were applied to increase the contrast of the jets and separate them. The rotation period of the nucleus was derived using cross-correlation method. The value of the rotation period is 12.1 ± 1.2 days for observations made in 2008 and 11.7 ± 1.5 days for observations made in 2009.

scholarly journals The Evolution of Jupiter Family Comets over 2000 Years

1992 ◽  
Vol 152 ◽  
pp. 269-274 ◽  
Author(s):  
G. Tancredi ◽  
H. Rickman
Keyword(s):  
Data Base ◽  
Orbital Evolution ◽  
Physical Parameters ◽  
Time Interval ◽  
Orbital Elements ◽  
Present Epoch ◽  
Numerical Integrations ◽  
Short Period

The orbital evolution of the whole sample sample of short-period comets was computed by numerical integrations for a time interval of 2000 yr centered on the present epoch. This data base is intended to serve in various studies involving the statistics of orbital evolution and correlation with physical parameters or discovery circumstances. We present some results concerning the following aspects: the evolution of the orbital elements and their past-future asymmetry, statistics on the discovery of comets and on the encounters of comets with Jupiter.

scholarly journals Stellar activity analysis of Barnard’s Star: Very slow rotation and evidence for long-term activity cycle

2019 ◽  
Author(s):  
B Toledo-Padrón ◽  
J I González Hernández ◽  
C Rodríguez-López ◽  
A Suárez Mascareño ◽  
R Rebolo ◽  
...  
Keyword(s):  
Time Series ◽  
Spectroscopic Data ◽  
Rotation Period ◽  
Photometric Data ◽  
Activity Level ◽  
Slow Rotation ◽  
Activity Levels ◽  
Stellar Activity

Abstract The search for Earth-like planets around late-type stars using ultra-stable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, since these phenomena induce radial velocity (RV) signals that can be misinterpreted as planetary signals. Among the nearby stars, we have selected Barnard’s Star (Gl 699) to carry out a characterization of these phenomena using a set of spectroscopic data that covers about 14.5 years and comes from seven different spectrographs: HARPS, HARPS-N, CARMENES, HIRES, UVES, APF, and PFS; and a set of photometric data that covers about 15.1 years and comes from four different photometric sources: ASAS, FCAPT-RCT, AAVSO, and SNO. We have measured different chromospheric activity indicators (Hα, Ca II HK and Na I D), as well as the FWHM of the cross-correlation function computed for a sub-set of the spectroscopic data. The analysis of Generalized Lomb-Scargle periodograms of the time series of different activity indicators reveals that the rotation period of the star is 145 ± 15 days, consistent with the expected rotation period according to the low activity level of the star and previous claims. The upper limit of the predicted activity-induced RV signal corresponding to this rotation period is about 1 m/s. We also find evidence of a long-term cycle of 10 ± 2 years that is consistent with previous estimates of magnetic cycles from photometric time series in other M stars of similar activity levels. The available photometric data of the star also support the detection of both the long-term and the rotation signals.

scholarly journals The Use of Lie Series in The Construction of a Perturbation Theory and some Recent Results in The Theory of The Motion ofd Hyperion

1999 ◽  
Vol 172 ◽  
pp. 349-358
Author(s):  
P.J. Message
Keyword(s):  
Perturbation Theory ◽  
Generating Function ◽  
Orbital Elements ◽  
Lie Series ◽  
Orbit Plane ◽  
Long Period ◽  
Short Period ◽  
First Results ◽  
Series Transformation

AbstractThis paper begins with a brief review of a form of the Lie series transformation, and then reports some new results in the study, using Lie series methods, of the orbit of Saturn’s satellite Hyperion. In particular, improved expressions are given for the long-period perturbations of the orbital elements which describe the motion in the orbit plane, and also first results for expressions for the short-period perturbations in the apse longitude, derived from the Lie series generating function.

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