YORP and Yarkovsky effects in asteroids (1685) Toro, (2100) Ra-Shalom, (3103) Eger, and (161989) Cacus

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F18%3A10385759" target="_blank" >RIV/00216208:11320/18:10385759 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/67985815:_____/18:00494685

Výsledek na webu

<a href="https://doi.org/10.1051/0004-6361/201731465" target="_blank" >https://doi.org/10.1051/0004-6361/201731465</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1051/0004-6361/201731465" target="_blank" >10.1051/0004-6361/201731465</a>

Jazyk výsledku

angličtina

Název v původním jazyce

YORP and Yarkovsky effects in asteroids (1685) Toro, (2100) Ra-Shalom, (3103) Eger, and (161989) Cacus

Popis výsledku v původním jazyce

Context. The rotation states of small asteroids are affected by a net torque arising from an anisotropic sunlight reflection and thermal radiation from the asteroids&apos; surfaces. On long timescales, this so-called YORP effect can change asteroid spin directions and their rotation periods. Aims. We analyzed lightcurves of four selected near-Earth asteroids with the aim of detecting secular changes in their rotation rates that are caused by YORP or at least of putting upper limits on such changes. Methods. We use the lightcurve inversion method to model the observed lightcurves and include the change in the rotation rate d omega/dt as a free parameter of optimization. To enlarge the time line of observations and to increase the sensitivity of the method, we collected more than 70 new lightcurves. For asteroids Toro and Cacus, we used thermal infrared data from the WISE spacecraft and estimated their size and thermal inertia by means of a thermophysical model. We also used the currently available optical and radar astrometry of Toro, Ra-Shalom, and Cacus to infer the Yarkovsky effect. Results. We detected a YORP acceleration of d omega/dt = (1.9 +/- 0.3) x 10(-8) rad d(-2) for asteroid Cacus. The current astrometric data set is not sufficient to provide detection of the Yarkovsky effect in this case. For Toro, we have a tentative (2 sigma) detection of YORP from a significant improvement of the lightcurve fit for a nonzero value of d omega/dt = 3.0 x 10(-9) rad d(-2). We note an excellent agreement between the observed secular change of the semimajor axis d omega/dt and the theoretical expectation for densities in the 2-2.5 g cm(-3) range. For asteroid Eger, we confirmed the previously published YORP detection with more data and updated the YORP value to (1.1 +/- 0.5) x 10(-8) rad d(-2). We also updated the shape model of asteroid Ra-Shalom and put an upper limit for the change of the rotation rate to vertical bar d omega/dt vertical bar &lt;= 1.5 x 10(-8) rad d(-2). Ra-Shalom has a greater than 3 sigma Yarkovsky detection with a theoretical value consistent with observations assuming its size and/or density is slightly larger than the nominally expected values. Using the convex shape models and spin parameters reconstructed from lightcurves, we computed theoretical YORP values and compared them with those measured. They agree with each other within the expected uncertainties of the model.

Název v anglickém jazyce

YORP and Yarkovsky effects in asteroids (1685) Toro, (2100) Ra-Shalom, (3103) Eger, and (161989) Cacus

Popis výsledku anglicky

Context. The rotation states of small asteroids are affected by a net torque arising from an anisotropic sunlight reflection and thermal radiation from the asteroids&apos; surfaces. On long timescales, this so-called YORP effect can change asteroid spin directions and their rotation periods. Aims. We analyzed lightcurves of four selected near-Earth asteroids with the aim of detecting secular changes in their rotation rates that are caused by YORP or at least of putting upper limits on such changes. Methods. We use the lightcurve inversion method to model the observed lightcurves and include the change in the rotation rate d omega/dt as a free parameter of optimization. To enlarge the time line of observations and to increase the sensitivity of the method, we collected more than 70 new lightcurves. For asteroids Toro and Cacus, we used thermal infrared data from the WISE spacecraft and estimated their size and thermal inertia by means of a thermophysical model. We also used the currently available optical and radar astrometry of Toro, Ra-Shalom, and Cacus to infer the Yarkovsky effect. Results. We detected a YORP acceleration of d omega/dt = (1.9 +/- 0.3) x 10(-8) rad d(-2) for asteroid Cacus. The current astrometric data set is not sufficient to provide detection of the Yarkovsky effect in this case. For Toro, we have a tentative (2 sigma) detection of YORP from a significant improvement of the lightcurve fit for a nonzero value of d omega/dt = 3.0 x 10(-9) rad d(-2). We note an excellent agreement between the observed secular change of the semimajor axis d omega/dt and the theoretical expectation for densities in the 2-2.5 g cm(-3) range. For asteroid Eger, we confirmed the previously published YORP detection with more data and updated the YORP value to (1.1 +/- 0.5) x 10(-8) rad d(-2). We also updated the shape model of asteroid Ra-Shalom and put an upper limit for the change of the rotation rate to vertical bar d omega/dt vertical bar &lt;= 1.5 x 10(-8) rad d(-2). Ra-Shalom has a greater than 3 sigma Yarkovsky detection with a theoretical value consistent with observations assuming its size and/or density is slightly larger than the nominally expected values. Using the convex shape models and spin parameters reconstructed from lightcurves, we computed theoretical YORP values and compared them with those measured. They agree with each other within the expected uncertainties of the model.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10308 - Astronomy (including astrophysics,space science)

Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2018

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Astronomy &amp; Astrophysics [online]

ISSN

1432-0746

e-ISSN

—

Svazek periodika

609

Číslo periodika v rámci svazku

Neuveden

Stát vydavatele periodika

FR - Francouzská republika

Počet stran výsledku

10

Strana od-do

—

Kód UT WoS článku

000423434200004

EID výsledku v databázi Scopus

2-s2.0-85042534493