César Briceño
A5103324006- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Molecular Spectroscopy and Structure
- Gamma-ray bursts and supernovae
- Space Exploration and Technology
- Astrophysical Phenomena and Observations
- Atmospheric Ozone and Climate
- Adaptive optics and wavefront sensing
- Galaxies: Formation, Evolution, Phenomena
- Calibration and Measurement Techniques
- Pulsars and Gravitational Waves Research
- Planetary Science and Exploration
- Spectroscopy and Laser Applications
- Advanced Combustion Engine Technologies
- Scientific Computing and Data Management
- Geological and Geochemical Analysis
- Environmental Monitoring and Data Management
- Atmospheric and Environmental Gas Dynamics
- Scientific Research and Discoveries
- CCD and CMOS Imaging Sensors
- Pharmacological Effects and Assays
- Geophysics and Gravity Measurements
Cerro Tololo Inter-American Observatory
2016-2025
Southern Astrophysical Research Telescope
2019-2024
NSF’s NOIRLab
2020-2021
Kitt Peak National Observatory
1998-2019
University of Toronto
2019
Canadian Institute for Theoretical Astrophysics
2019
Optica
2018
University of the Andes
2004-2013
University of Michigan–Ann Arbor
2012
Instituto Venezolano de Investigaciones Científicas
2001-2012
DESI (Dark Energy Spectroscopic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations (BAO) and the growth of structure through redshift-space distortions with wide-area galaxy quasar redshift survey. To trace underlying matter distribution, spectroscopic targets be selected in four classes from imaging data. We measure luminous red galaxies up to $z=1.0$. probe Universe out even higher redshift, target bright [O II] emission line $z=1.7$....
Abstract The DESI Legacy Imaging Surveys ( http://legacysurvey.org/ ) are a combination of three public projects (the Dark Energy Camera Survey, the Beijing–Arizona Sky and Mayall z -band Survey) that will jointly image ≈14,000 deg 2 extragalactic sky visible from northern hemisphere in optical bands g , r using telescopes at Kitt Peak National Observatory Cerro Tololo Inter-American Observatory. combined survey footprint is split into two contiguous areas by Galactic plane. imaging...
We present new measurements of disk accretion rates for T Tauri stars in the Taurus molecular cloud complex. Our results are based on intermediate-resolution spectrophotometry from 3200 to 5200 Å, which is used derive excess hot continuum emission produced by onto central star. Previous estimates literature differ as much 1 order magnitude; our agree better with lowest estimates, and we discuss problems systematic effects that led previous disagreement. In particular, note stellar...
We present 1210 Johnson/Cousins B, V, R, and I photometric observations of 22 recent Type Ia supernovae (SNe Ia): SNe 1993ac, 1993ae, 1994M, 1994S, 1994T, 1994Q, 1994ae, 1995D, 1995E, 1995al, 1995ac, 1995ak, 1995bd, 1996C, 1996X, 1996Z, 1996ab, 1996ai, 1996bk, 1996bl, 1996bo, 1996bv. Most the photometry was obtained at Fred Lawrence Whipple Observatory Harvard-Smithsonian Center for Astrophysics in a cooperative observing plan aimed improving database Ia. The redshifts sample range from cz =...
We report new Spitzer Space Telescope observations from the IRAC and MIPS instruments of young (~ 3 Myr) sigma Orionis cluster. identify 336 stars as members cluster using optical near-infrared color magnitude diagrams. Using spectral energy distribution (SED) slopes in range, we place objects several classes: non-excess stars, with optically thick disks(like classical T Tauri stars), class I (protostellar) candidates, ``evolved disks''; last exhibit smaller excesses than disk systems. In...
We present multiband photometry of 185 type-Ia supernovae (SNe Ia), with over 11,500 observations. These were acquired between 2001 and 2008 at the F. L. Whipple Observatory Harvard-Smithsonian Center for Astrophysics (CfA). This sample contains largest number homogeneously observed reduced nearby SNe Ia (z ≲ 0.08) published to date. It more than doubles sample, bringing SN cosmology point where systematic uncertainties dominate. Our natural system has a precision ≲0.02 mag in BVRIr'i' ≲0.04...
We present a study of accretion in sample 45 young, low-mass objects variety star-forming regions and young associations, about half which are likely substellar. Based primarily on the presence broad, asymmetric Hα emission, we have identified 13 (~30% our sample) that strong candidates for ongoing accretion. At least three these do not detect significant continuum veiling most accretors with late spectral types (M5-M7). Accretion shock models show lack measurable allows us to place an upper...
We present Hubble Space Telescope ultraviolet spectra and supporting ground-based data for a sample of nine intermediate-mass T Tauri stars (IMTTSs; 1.5–4 M⊙). The targets belong to three star-forming regions: Tau, SU Aur, RY Tau in the Taurus clouds; EZ Ori, P2441, V1044 Ori OB1c association surrounding Orion Nebula cluster; CO GW GX ring around λ Ori. observations include nearly simultaneous UBV(R I)C photometry, 6 Å resolution covering range 3900–7000 Å, optical echelle 5800–8600 K-band...
We present UBVRI photometry of 44 Type Ia supernovae (SNe Ia) observed from 1997 to 2001 as part a continuing monitoring campaign at the Fred Lawrence Whipple Observatory Harvard-Smithsonian Center for Astrophysics. The data set comprises 2190 observations and is largest homogeneously reduced sample SNe date, nearly doubling number well-observed, nearby with published multicolor CCD light curves. large U-band unique addition, important connections high redshift. decline rate SN curves...
Abstract We present optical and ultraviolet spectra of the first electromagnetic counterpart to a gravitational-wave (GW) source, binary neutron star merger GW170817. Spectra were obtained nightly between 1.5 9.5 days post-merger, using Southern Astrophysical Research Magellan telescopes; UV spectrum was with Hubble Space Telescope at 5.5 days. Our data reveal rapidly fading blue component ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>T</mml:mi>...
We present the results of Gould's Belt Distances Survey young star-forming regions toward Orion Molecular Cloud Complex. detected 36 stellar objects (YSOs) with Very Large Baseline Array, 27 which have been observed in at least three epochs over course two years. At half these YSOs belong to multiple systems. obtained parallax and proper motions stars study structure kinematics measured a distance 388 ± 5 pc Nebula Cluster, 428 10 southern portion L1641, NGC 2068, roughly ∼420 2024. Finally,...
DESI (Dark Energy Spectropic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations and the growth of structure through redshift-space distortions with wide-area galaxy quasar redshift survey. The instrument robotically-actuated, fiber-fed spectrograph capable taking up to 5,000 simultaneous spectra over wavelength range from 360 nm 980 nm. fibers feed ten three-arm spectrographs resolution $R= λ/Δλ$ between 2000 5500, depending on...
TESS is finding transiting planet candidates around bright, nearby stars across the entire sky. The large field-of-view, however, results in low spatial resolution, therefore multiple contribute to almost every light curve. High-angular resolution imaging can detect previously unknown companions planetary candidate hosts that dilute transit depths, lead host star ambiguity, and some cases are source of false-positive signals. We use speckle on SOAR search for 542 Southern provide correction...
Abstract We present the discovery and characterization of TOI-4364b, a young mini-Neptune in tidal tails Hyades cluster, identified through TESS transit observations ground-based follow-up photometry. The planet orbits bright M dwarf ( K = 9.1 mag) at distance 44 pc, with an orbital period 5.42 days equilibrium temperature <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>48</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>8</mml:mn> </mml:mrow> <mml:mo>−</mml:mo>...
By combining a deep optical imaging (I, z') survey of 8 deg2 in the Taurus star-forming region with data from Two-Micron All-Sky Survey (2MASS) and follow-up spectroscopy, we have performed search for low-mass members that is complete to 0.02 M☉ reddenings AV ≲ 4. We report discovery nine new spectral types M5.75-M9.5, corresponding masses 0.1-0.015 by recent evolutionary models. The M9.5 member least massive brown dwarf found date region. derive an initial mass function (IMF) fields...
We present an analysis of the optical spectra 75 early-type emission-line stars, many which have been classified previously as Herbig Ae/Be (HAeBe) stars. Accurate spectral types were derived for 58 members sample; high continuum veiling, contamination by nonphotospheric absorption features, or a composite binary spectrum prevented accurate typing rest. Approximately half our sample exhibited [O I] λ6300 forbidden-line emission down to detection limit 0.1 Å equivalent width; third Fe II...
We have found that two members of the TW Hydrae association, and Hen 3-600A, are still actively accreting, based on ballistic infall signature their broad Halpha emission profiles. present first quantitative analysis accretion in these objects conclude same mechanisms which operate well-studied 1 Myr old T Tauri stars can do occur older (10 Myr) stars. derive estimates disk mass rate Hya 1-2 orders magnitude lower than average rates objects. The decrease over 10 Myr, as well low fraction...
We present observations of Halpha emission line profiles taken at Magellan Observatory for a sample 39 young low-mass stars and brown dwarfs in the Taurus Chamaeleon I star forming regions. have identified 11 new substellar accretors, more than tripling number known with measurable accretion activity. These include lowest-mass objects yet seen accretion, masses down to ~0.015 Msun. Using models produced magnetospheric flows, most widely applicable primary calibrator now available, we...
We have measured the periods and light curves of 148 RR Lyrae variables from V = 13.5 to 19.7 first 100 deg2 Quasar Equatorial Survey Team survey. Approximately 55% these stars belong clump detected earlier by Sloan Digital Sky Survey. According our measurements, this feature has ~10 times background density halo stars, spans at least 375 35 in α δ (≥30 ≥3 kpc), lies ~50 kpc Sun, a depth along line sight ~5 (1 σ). These properties are consistent with recent models that suggest it is tidal...
We have carried out a study of the early type stars in nearby OB associations spanning an age range $\sim$ 3 to 16 Myr, with aim determining fraction which belong Herbig Ae/Be class. studied B, A, and F ($\le 500$ pc) Upper Scorpius, Perseus OB2, Lacerta OB1, Orion membership determined from Hipparcos data. obtained spectra for 440 these associations, we accurate spectral types, visual extinctions, effective temperatures, luminosities masses, using photometry. Using colors corrected...
We present new Spitzer Space Telescope observations of two fields in the Orion OB1 association. report here IRAC/MIPS for 115 confirmed members and 41 photometric candidates ~10 Myr 25 Orionis aggregate OB1a subassociation, 106 65 5 region located OB1b subassociation. The shows a disk frequency 6% while field subassociation 13%. Combining IRAC, MIPS 2MASS photometry we place stars bearing disks several classes: with optically thick (class II systems), an inner transitional (transitional...
We present the first results of Gould's Belt Distances Survey (GOBELINS), a project aimed at measuring proper motion and trigonometric parallax large sample young stars in nearby regions using multi-epoch Very Long Baseline Array (VLBA) radio observations. Enough VLBA detections have now been obtained for 16 stellar systems Ophiuchus to derive their motion. This leads distance determinations individual with an accuracy 0.3 few percent. In addition, orbits 6 multiple were modelled by...
Abstract We present Gaia -DR2 astrometry of a sample YSO candidates in Ophiuchus, Serpens Main, and South/W40 the Aquila Rift, which had been mainly identified by their infrared excess with Spitzer . compare parallaxes against published new obtained from our Very Long Baseline Array (VLBA) program Gould’s Belt Distances Survey. obtain consistent results between VLBA for mean each regions analyzed here. see small offsets, when comparing values, few tens microarcseconds parallaxes, are either...
Abstract We present the discovery and validation of a three-planet system orbiting nearby (31.1 pc) M2 dwarf star TOI-700 (TIC 150428135). lies in TESS continuous viewing zone Southern Ecliptic Hemisphere; observations spanning 11 sectors reveal three planets with radii ranging from 1 R ⊕ to 2.6 orbital periods 9.98 37.43 days. Ground-based follow-up combined diagnostic vetting tests enables us rule out common astrophysical false-positive scenarios validate planets. The outermost planet, d,...