arXiv subjects

Gisela N. Ortiz-Leon

Publications and source records attributed to Gisela N. Ortiz-Leon.

9 recordsLinked to original sources

arXiv2026

Characterization of Planetary Systems with Astrometry

Astrometry is the oldest method used to search for extrasolar planets. This technique provides key information about a planetary system, like the true mass of planets and its three-dimensional orbital architecture. Nowadays, the space-based mission Gaia, on one hand, and ground-based interferometry at infrared and radio wavelengths, on the other hand, can achieve astrometric accuracies of tens of micro-arseconds. Thanks to this unprecedented level of accuracy, the number of astrometrically discovered exoplanets has started to grow. In this chapter, I review the basic principles for orbital characterization of unseen planetary companions using astrometric data. I also review the properties of the exoplanets discovered so far with astrometric methods and comment on the contributions that this technique can make to the exoplanet field.

astro-ph.EP↗

arXiv2025

Upper Limits to the Proper Motions of JuMBO 24, a Jupiter-Mass Binary Object Candidate in Orion

Using JWST near-infrared data of the inner Orion Nebula, \citet{Pearson_McCaughrean_2023} detected 40 binary systems they proposed to be Jupiter-Mass Binary Objects (JuMBOs) -- although their actual nature is still in debate. Only one of the objects, JuMBO\,24, was detected in the radio continuum. Here, we report on new radio continuum (10 GHz) Karl G. Jansky Very Large Array (VLA) detections of the radio counterpart to JuMBO\,24, and on an unsuccessful search for 5 GHz continuum emission with the High Sensitivity Array (HSA). From our new VLA detections and adopting a distance to the region, we set an upper limit of $\simeq 6$~km~s$^{-1}$ to the velocity of the radio source in the plane of the sky. This upper limit favors an origin for this source similar to that of stars, that is, from a stationary contracting core. The nature of the radio emission remains uncertain but the lack of strong variability (all VLA observations are consistent with a steady flux of $\sim$50 $μ$Jy), of detection on long HSA baseline, and of detectable circular polarization in VLA data do not favor a non-thermal origin.

astro-ph.EP↗

arXiv2024

Precise Mass, Orbital motion and Stellar properties of the M-dwarf binary LP 349-25AB

LP~349$-$25 is a well studied close stellar binary system comprised of two late M dwarf stars, both stars close to the limit between star and brown dwarf. This system was previously identified as a source of GHz radio emission. We observed LP~349$-$25AB in 11 epochs in 2020$-$2022, detecting both components in this nearby binary system using the Very Long Baseline Array (VLBA). We fit simultaneously the VLBA absolute astrometric positions together with existing relative astrometric observations derived from optical/infrared observations with a set of algorithms that use non-linear least-square, Genetic Algorithm and Markov Chain Montecarlo methods to determine the orbital parameters of the two components. We find the masses of the primary and secondary components to be 0.08188 $\pm$ 0.00061 $M\odot$, and 0.06411 $\pm$ 0.00049 $M_\odot$, respectively, representing one of the most precise mass estimates of any UCDs to date. The primary is an UCD of 85.71$\pm$0.64 M$_{Jup}$, while the secondary has a mass consistent with being a Brown Dwarf of 67.11 $\pm$ 0.51 $M_{Jup}$. This is one of the very few direct detections of a Brown Dwarf with VLBA observations. We also find a distance to the binary system of 14.122 $\pm$ 0.057 pc. Using Stellar Evolutionary Models, we find the model-derived stellar parameters of both stars. In particular, we obtain a model-derived age of 262 Myr for the system, which indicates that LP~349$-$25AB is composed of two pre-main-sequence stars. In addition, we find that the secondary star is significantly less evolved that the primary star.

astro-ph.SR↗

arXiv2023

The distance to the Serpens South Cluster from H2O masers

In this Letter, we report Very Long Baseline Array observations of 22 GHz water masers toward the protostar CARMA-6, located at the center of the Serpens South young cluster. From the astrometric fits to maser spots, we derive a distance of 440.7+/-3.5 pc for the protostar (1% error). This represents the best direct distance determination obtained so far for an object this young and deeply embedded in this highly obscured region. Taking into account depth effects, we obtain a distance to the cluster of 440.7+/-4.6 pc. Stars visible in the optical that have astrometric solutions in the Gaia Data Release 3 are, on the other hand, all located in the periphery of the cluster. Their mean distance of 437 (+51, -41) pc is consistent within 1-sigma with the value derived from maser astrometry. As the maser source is just at the center of Serpens South, we finally solve the ambiguity of the distance to this region that has prevailed over the years.

astro-ph.GA↗

arXiv2020

SiO maser astrometry of the red transient V838 Monocerotis

We present multi-epoch observations with the VLBA of SiO maser emission in the v=1, J=1-0 transition at 43 GHz from the remnant of the red nova V838 Mon. We model the positions of maser spots to derive a parallax of 0.166+/-0.060 mas. Combining this parallax with other distance information results in a distance of 5.6+/-0.5 kpc, which agrees with an independent geometric distance of 6.1+/-0.6 kpc from modeling polarimetry images of V838 Mon's light echo. Combining these results, and including a weakly constraining Gaia DR2 parallax, yields a best estimate of distance of 5.9+/-0.4 kpc. The maser spots are located close to the peaks of continuum at ~225 GHz and SiO J=5-4 thermal emission detected with ALMA. The proper motion of V838 Mon confirms its membership in a small open cluster in the Outer spiral arm of the Milky Way.

astro-ph.SR↗

arXiv2018

The Gould's Belt Distances Survey (GOBELINS). IV. Distance, Depth and Kinematics of the Taurus Star-Forming Region

We present new trigonometric parallaxes and proper motions of young stellar objects in the Taurus molecular cloud complex from observations collected with the Very Long Baseline Array as part of the Gould's Belt Distances Survey (GOBELINS). We detected 26 young stellar objects and derived trigonometric parallaxes for 18 stars with an accuracy of 0.3$\%$ to a few percent. We modeled the orbits of six binaries and determined the dynamical masses of the individual components in four of these systems (V1023 Tau, T Tau S, V807 Tau and V1000 Tau). Our results are consistent with the first trigonometric parallaxes delivered by the Gaia satellite and reveal the existence of significant depth effects. We find that the central portion of the dark cloud Lynds 1495 is located at $d=129.5\pm 0.3$ pc while the B 216 clump in the filamentary structure connected to it is at $d=158.1\pm 1.2$ pc. The closest and remotest stars in our sample are located at $d=126.6\pm 1.7$ pc and $d=162.7\pm 0.8$ pc yielding a distance difference of about 36 pc. We also provide a new distance estimate for HL Tau that was recently imaged. Finally, we compute the spatial velocity of the stars with published radial velocity and investigate the kinematic properties of the various clouds and gas structures in this region.

astro-ph.SR↗

arXiv2014

Tomography of Galactic star-forming regions and spiral arms with the Square Kilometer Array

Very Long Baseline Interferometry (VLBI) at radio wavelengths can provide astrometry accurate to 10 micro-arcseconds or better (i.e. better than the target GAIA accuracy) without being limited by dust obscuration. This means that unlike GAIA, VLBI can be applied to star-forming regions independently of their internal and line-of-sight extinction. Low-mass young stellar objects (particularly T Tauri stars) are often non-thermal compact radio emitters, ideal for astrometric VLBI radio continuum experiments. Existing observations for nearby regions (e.g. Taurus, Ophiuchus, or Orion) demonstrate that VLBI astrometry of such active T Tauri stars enables the reconstruction of both the regions' 3D structure (through parallax measurements) and their internal kinematics (through proper motions, combined with radial velocities). The extraordinary sensitivity of the SKA telescope will enable similar "tomographic mappings" to be extended to regions located several kpc from Earth, in particular to nearby spiral arm segments. This will have important implications for Galactic science, galactic dynamics and spiral structure theories.

astro-ph.SR↗

arXiv2014

Periodic Radio Continuum Emission Associated with the beta Cephei Star V2187 Cyg

We present new optical time-resolved photometry and medium-resolution spectroscopy of V2187 Cyg. We confirm its classification as a beta Cephei star based on sinusoidal light variations with a period of 0.2539 days and mean amplitudes of 0.037 and 0.042 magnitudes in "i" and "V", respectively. We classified the spectrum of this star B2-3V with no evidence of variations in the profiles of its absorption lines in timescales of hours or days. The stellar spectrum is totally absent of emission lines. We detected unexpected faint radio continuum emission (between 0.4 and 0.8 mJy at 6-cm) showing a sinusoidal variation with a period of 12.8 days. The radio spectrum is thermal. We searched in the Very Large Array archive for radio continuum emission toward other 15 beta Cephei stars. None of these additional stars, some of them much closer to the Sun than V2187 Cyg, was detected, indicating that radio emission is extremely uncommon toward beta Cephei stars.

astro-ph.SR↗

arXiv2012

Multi-Epoch VLBA Observations of the Compact Wind-Collision Region in the Quadruple System Cyg OB2 #5

We present multi--epoch VLBA observations of the compact wind collision region in the Cyg OB2 #5 system. These observation confirm the arc-shaped morphology of the emission reported earlier. The total flux as a function of time is roughly constant when the source is "on", but falls below the detection limit as the wind collision region approaches periastron in its orbit around the contact binary at the center of the system. In addition, at one of the "on" epochs, the flux drops to about a fifth of its average value. We suggest that this apparent variation could result from the inhomogeneity of the wind that hides part of the flux rather than from an intrinsic variation. We measured a trigonometrical parallax, for the most compact radio emission of 0.61 $\pm$ 0.22 mas, corresponding to a distance of 1.65 $^{+0.96}_{-0.44}$ kpc, in agreement with recent trigonometrical parallaxes measured for objects in the Cygnus X complex. Using constraints on the total mass of the system and orbital parameters previously reported in the literature, we obtain two independent indirect measurements of the distance to the Cyg OB2 #5 system, both consistent with 1.3--1.4 kpc. Finally, we suggest that the companion star responsible for the wind interaction, yet undetected, is of spectral type between B0.5 to O8.

astro-ph.SR↗