arXiv subjects

Toni Scarmato

Publications and source records attributed to Toni Scarmato.

9 recordsLinked to original sources

arXiv2026

Linking System of Jets to the Non-Gravitational Acceleration of 3I/ATLAS

Building on the jet morphology and periodic wobble analysis of 3I/ATLAS in Scarmato & Loeb (2026), we link observed jet position angles (PAs) and the non-gravitational acceleration components (A1,A2,A3) in the 3D RTN (radial, transverse, normal) frame relative to the Sun. We: (i) compute RTN directions from heliocentric state vectors and project them on the sky at the measured astromet ric pointings; (ii) compare projected RTN PAs to three persistent jets (Jet1-Jet2-Jet3) and quantify angular offsets; and (iii) estimate order-of-magnitude thrust and accelerations from HST/WFC3-UVIS F350LP net counts via transformations from photometry to cross-section, dust mass, mass-loss rate, and thrust. We explicitly document the uncertainties through background handling, phase-function systematics, and geometric degeneracies along the line of sight. For U.T. 2025-11-30.80903, Jet2 is aligned with the projected transverse direction to within 0.5 degs, while Jet3 is the closest to the pro jected normal direction with a moderate offset (about 25 degs). For UT 2025-12-27, Jet2 exhibits a monotonic PA drift over 24 minutes with a larger oscillation amplitude.

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arXiv2026

Periodic Wobble of the Post-Perihelion Jet Structure Around 3I/ATLAS

We analyse data on the post-perihelion morphology, including jet position angles (PAs) and coma dominated photometry of the interstellar object 3I/ATLAS. From Hubble Space Telescope (HST) images processed with a Larson Sekanina rotational gradient filter, we measure the PAs of three main persistent jet like features between November 30 and December 27, 2025 and fit a weighted Fourier model in a period scan. The dominant jet PA wobble yields Pjet = 7.20 +/- 0.05 h. An independent Gr (R band) time-series photometry data set, using two different apertures from MPC station L92, analyzed with nightly offsets and 30 minute binning, gives Pphot = 7.136 +/- 0.001 h (formal 1sigma), with a semiamplitude A about 0.311 mag and scatter sigmajit about 0.089 mag. The close agreement beetwen the periods supports a characteristic post-perihelion period of about 7.1 h. We interpret this period as an attitude precession/nutation (non principal axis rotation) traced by jet orientation and coma flux redistribution. The jet structure precesses about the rotation axis with a characteristic angular excursion of order about 20 degs, and the rotation axis is aligned with the sunward direction to within about 20 degs.

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arXiv2026

Rotation Period of 3I/ATLAS After Perihelion from Jet Position Angle Wobble and Photometric Variability

We determine the post-perihelion rotation period of 3I/ATLAS using two independent diagnostics: the temporal modulation of the position angle (PA) of a persistent jet-like feature, and a time-series photometric light curve in the Gr (R) band. For the jet morphology, we measure the PA at multiple epochs by applying the Larson-Sekanina Rotational Gradient filter to Hubble Space Telescope images between November 20, 2025 and December 27, 2025, and model the phase-folded PA curve with weighted least-squares Fourier series up to two harmonics while scanning trial periods P to identify minima in \c{hi}2(P). For the photometry, we adopt the best-fit period from an independent 30-minute binned analysis (from a 0.25 meter telescope MPC L92) based on a refined \c{hi}2(P) profile for a sinusoidal model with nightly offsets. We find that the jet-PA modulation gives a period Pjet = 7.20 +/-0.05 h (adopting a conservative uncertainty dominated by sparse sampling and systematics), while the photometry yields Pphot = 7.136+/-0.001 h (formal 1{\sigma} uncertainty). Although the periods differ slightly, the offset is plausibly attributable to non-Gaussian systematics and aliasing. The combined data supports a post-perihelion rotation period of 7.1 h associated with precession of the jet structure around the rotation axis by 20{\deg}. The rotation axis is aligned with the sunward direction to within 20{\deg}

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arXiv2025

Interstellar Interloper 3I/ATLAS: Nucleus Size, Photometry in RGB, Af(rho) and Antitail Structure Analysis

Interstellar comet 3I/ATLAS (C/2025 N1) exhibits an unusual, tightly collimated dust feature in the sunward hemisphere which has been widely described as an anti-tail. At the same time, precise constraints on the nucleus size have been derived from a combination of high-resolution imaging and non-gravitational dynamics. In this work I present a unified analysis that combines existing constraints on the nucleus radius with new ground-based RGB imaging of the dust anti-tail obtained with a 0.25 m telescope at the Toni Scarmato Astronomical Observatory (MPC L92).

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arXiv2025

Measuring Cometary Nuclei Behind Bright Comae: PSF Delta Decomposition with Bicubic Resampling and an Application to Interstellar Comet 3I/ATLAS C/2025 N1

Measuring cometary nuclei is notoriously difficult because they are usually unresolved and embedded within bright comae, which hampers direct size measurements even with space telescopes. We present a practical, instrumental method that, stabilises the inner core through bicubic resampling, performs forward point-spread function PSF+convolution, and separates the unresolved nucleus from the inner-coma profile via an explicit Dirac Delta function added to a Rho^-1 surface brightness law. The method yields the nucleus flux by fitting an azimuthal averaged profile with two amplitudes only PSF core and convolved coma, with transparent residual diagnostics. As a case study, we apply the workflow to the interstellar comet 3I/ATLAS alias C/2025 N1, incorporating Hubble Space Telescope constraints on the nucleus size. We find that radius solutions consistent with 0.16 <= Rn <= 2.8 km for Pv = 0.04 are naturally recovered, in line with the most recent HST upper limits. The approach is well-suited for survey pipelines Rubin LSST and targeted follow up.

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arXiv2016

Comet C/2011 L4 (PanStarrs): Small nucleus, fast rotator and dust rich comet observed after perihelion

Orbital elements of C2011 L4 (PanStarrs) Oort cloud comet, computed by MPC (Minor Planet Center, Minor Planet Electronic Circular 2012-T08), show that the closest approach to the Sun occurred on 2013 March 10th, at about 0.3 A.U., then about 4,51x10^7 km. Discovered by Richard Wainscoat (Institute for Astronomy, University of Hawaii) on four CCD images taken with the 1.8-m "Pan-STARRS 1" telescope at Haleakala taken on 2011 June 6th. My first observation of the comet was on 2013 March 10th whit the comet visible in the twilight. I did the following visual estimation; Mar. 10.73,-1.0*,5'(T. Scarmato, Calabria, Italy, 7x50 binoculars; altitude 7 deg, tail 1 deg in pa 140 deg), reported to the ICQ (International Comet Quarterly). Easy comet in 7x50 binoculars I started to see C/2011 L4 at 18:35 L.T. when the comet was at about 7° above the horizon. I saw a tail long about 1,5° in pa 140° with a coma well condensed and large about 5'. I followed the comet until to the set at 18:55 L.T., still clearly visible at so low altitude about 1° or less! I don't saw Mars (1.39 mag) at the same altitude, so I esteemed the comet using Aldebaran (1.1 mag) at 62,44° of altitude also using the ICQ Table of Atmospheric Extinction; but remembering C/2006 P1 in the same conditions of observation I could to assume that the comet was at negative apparent total magnitude m1= -1.0. The image of the comet was impressive (see Fig. 2). Here, I present my observations and results on the size of the nucleus, period of rotation, dust production and peculiar structures in the inner coma. Key words: General: general; comets: C/2011 L4 (PanStarrs), PanStarrs, comets, afrho, photometry of aperture, flux, apparent magnitude, absolute magnitude; comet nucleus: size, rotation.

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arXiv2014

Comet C/2011 J2 (Linear): Fragmentation and physical properties of the two nuclei

Comet C2011 J2 (Linear), was discovered to the Catalina Sky Survey Observatory, based on University of Arizona. Is an hyperbolic comet passed to the perihelion at T 2013 Dec. 25.4020 TT. The distance q from the Sun is 3.443732 A.U., that mean that dont never cross the snow line. Also, the Sun gravitational force is not such to determine a strong stress on the cometary nucleus. A possible fragmentation at that distance from the Sun in general, is unlikely, but on 2014 September 19th, the CBAT 3979 by D. Green of the ICQ, report the discoveries of a fragment companion of the comet main body. In the following days others observers confirms the presence of the secondary body. (F. Manzini et al. September 2014, IAU CBET 3986, 2014 September 24th) In the observation of the comet on 2014 September 28, using a 25 cm Newton and CCD with R photometric filter, I detect the secondary body and assuming as possible scenario the presence of a solid fragment in the cloud of material of the fragmentation, I measured some physical parameters, the magnitude in R band and Af(rho) value of the two nuclei. Here are presented the preliminaries data.

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arXiv2014

Photometry differential of comets

Here are presented the results obtained with three comets 73P (Schwassmann Wachmann) B the component B, 6P dArrest and C2008 J1 (Boattini). Comet 73P was observed in April 2006 with a CCD camera Starlight Express SXL8 attached to direct focus of a Newton telescope 250 mm, focal length 1200 mm, while the 6P and C2008 J1 were ever observed by telescope Newtonian but with a CCD camera Atik 16IC to direct focus. To the CCD camera was added a filter photometric Rc (Schuler). For 6P comet has been used a defocus of 14 pixels, meaning that the central false nucleus has defocused a FWHM of 14 pixels. The technical data of the tools used are shown in Tables 1 and 2.

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arXiv2014

Sungrazer Comet C/2012 S1 (ISON): Curve of light, nucleus size, rotation and peculiar structures in the coma and tail

We present our results for comet (ISON). Our results were obtained with amateur telescopes observing from the ground, before and after the comet had passed conjunction with the Sun in August 2013. We measured a mean radius of 830 +- 245 m, and we have identified a persistent structure in the direction of the sun with a preliminary rotation period of approximately 3 days. In the tail are visible peculiar structures linked to the production of dust by the nucleus. Our data Af(rho) (AHearn et al. 1984), a physical parameter that indicates the amount of dust produced, is approximately 500+-50 cm in the quite phase which means a production Qdust=500kgxsec^-1 equal to 43.2x10^6 kg per day. A considerable amount for a small comet. We have also detected two major outbursts in January, 2013 and November, 2013, and minor outbursts throughout the observation period. Key words: General: general; comets: C2012 S1 (ISON), ISON, comets, afrho, photometry of aperture, flux, apparent magnitude, absolute magnitude, fragmentation.

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