A5042216818- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Molecular Spectroscopy and Structure
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Space Exploration and Technology
- Solar and Space Plasma Dynamics
- Calibration and Measurement Techniques
- Nuclear Physics and Applications
- Phase Equilibria and Thermodynamics
- Medical Imaging Techniques and Applications
- Geomagnetism and Paleomagnetism Studies
- Thermodynamic properties of mixtures
- History and Developments in Astronomy
- Superconducting Materials and Applications
- Astrophysics and Cosmic Phenomena
- Ionosphere and magnetosphere dynamics
- Geophysics and Gravity Measurements
- Atmospheric Ozone and Climate
- Pulsars and Gravitational Waves Research
- Scientific Measurement and Uncertainty Evaluation
- Origins and Evolution of Life
University of Dundee
2017-2024
University of St Andrews
2014-2019
Universidad Autónoma de Madrid
2011-2017
Max Planck Institute for Astronomy
2006-2012
Max Planck Society
2008-2011
Center for Astrophysics Harvard & Smithsonian
2002-2009
University of Michigan–Ann Arbor
2009
Max Planck Institute for Extraterrestrial Physics
2009
University of Groningen
2009
Goddard Space Flight Center
2009
We summarize the first results from Gould Belt survey, obtained toward Aquila Rift and Polaris Flare regions during 'science demonstration phase' of Herschel. Our 70-500 micron images taken in parallel mode with SPIRE PACS cameras reveal a wealth filamentary structure, as well numerous dense cores embedded filaments. Between ~ 350 500 prestellar 45-60 Class 0 protostars can be identified field, while unbound starless no are observed field. The core mass function (CMF) derived for region...
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...
<i>Context. <i/>Knowledge of the evolution circumstellar accretion disks is pivotal to our understanding star and planet formation; yet despite intensive theoretical observational studies, disk dissipation process not well understood. Infrared observations large numbers young stars, as performed by <i>Spitzer Space Telescope<i/>, may advance knowledge this inherently complex process. While infrared data reveal evolutionary status disk, they hold little information on properties central...
We present the results of an infrared imaging survey two clusters in Cep OB2 Association, Tr 37 and NGC 7160, using IRAC MIPS instruments on board Spitzer Space Telescope. Our observations cover wavelength range from 3.6 to 24 μm, allowing us detect disk emission over a typical radii ~0.1 ~20 AU central star. In 37, with age about 4 Myr, 48% low-mass stars exhibit detectable bands. Roughly 10% disks may be "transition" objects, essentially photospheric fluxes at wavelengths ≤4.5 μm but...
With the uniquely high contrast within 01 (Δmag(L') = 5–6.5 mag) available using Sparse Aperture Masking with NACO at Very Large Telescope, we detected asymmetry in flux from Herbig Fe star HD 142527 a barycenter emission situated projected separation of 88 ± 5 mas (12.8 1.5 AU 145 pc) and ratios H, K, L' 0.016 0.007, 0.012 0.008, 0.0086 0.0011, respectively (3σ errors), relative to primary disk. After extensive closure-phase modeling, interpret this detection as close-in, low-mass stellar...
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 report the detection of a faint pointlike feature possibly related to ongoing planet-formation in disk transition star HD 169142. The has $\Delta$mag(L)$\sim$6.4, at separation $\sim$0.11" and PA$\sim$0$^{\circ}$. Given its lack an H or K$_{S}$ counterpart despite relative brightness, this candidate cannot be explained by purely photospheric emission must heated as yet unknown source. Its extremely red colors make it highly unlikely background object, but future multi-wavelength followup...
HD 142527A is one of the most studied Herbig Ae/Be stars with a transitional disk, as it has largest imaged gap in any protoplanetary disk: gas cleared from 30 to 90 AU. The HD142527 system also unique that stellar companion small mass compared primary star. This factor ~20 ratio between two objects makes this binary different other YSO. could therefore provide valuable test bed. low-mass object may be responsible for both and dust trapping observed by ALMA at longer distances. We NACO GPI...
Using the Hectochelle multifiber spectrograph, we have obtained high-resolution (R ∼ 34,000) spectra in Hα region for a large number of stars 4 Myr old cluster Tr 37, containing 146 previously known members and 26 newly identified ones. We present line profiles all members, compare them to our IR observations dusty disks (Two Micron All Sky Survey JHK + IRAC MIPS 24 μm), use radial velocities as membership criterion, calculate rotational velocities. find good correlation between...
We present the results of MMT observations young stars for our study protoplanetary disks at ages 1–10 Myr in two clusters located Cepheus OB2 region: Trumpler 37 (embedded H II region IC 1396) and NGC 7160. Using low-resolution optical spectra from Hectospec multifiber spectrograph, we have tripled number known low-mass cluster members, identifying ∼130 new members Tr ∼30 use indicators youth (Li absorption 6707 Å) accretion/chromospheric activity (Hα emission) to identify classify members....
We present accretion rates for a large number of solar-type stars in the Cep OB2 region, based on U-band observations. Our study comprises 95 members ∼4 Myr old cluster Tr 37 (including 20 "transition" objects (TOs)), as well only classical T Tauri star (CTTS) ∼12 NGC 7160. The show different disk morphologies, with majority them having evolved and flattened disks. typical are about 1 order magnitude lower than regions aged 1–2 Myr, we find no strong correlation between morphology rates....
Context. Fomalhaut is a young (2 ± 1 × 108 years), nearby (7.7 pc), 2 M⊙ star that suspected to harbor an infant planetary system, interspersed with one or more belts of dusty debris.
(abridged) We investigate the properties of young stars and their disks in NGC 6357 complex, concentrating on most massive star cluster within complex: Pismis 24. discover two new clusters complex. give a revised distance estimate for 24 1.7+-0.2 kpc. find that Pis 24-18 is binary system, with secondary being main X-ray source pair. derive mass function up to completeness limit at low masses it agrees well IMF Trapezium cluster. median age 1 Myr members. five proplyds HST archival imaging...
We investigate the young stellar objects (YSOs) in Lynds~1641 (L1641) cloud using multi-wavelength data including Spitzer, WISE, 2MASS, and XMM covering ~1390 YSOs across a range of evolutionary stages. In addition, we targeted sub-sample for optical spectroscopy. use this data, along with archival photometric to derive spectral types, extinction values, masses, ages, as well accretion rates. obtain disk fraction ~50% L1641. The frequency is almost constant function mass slight peak at...
Low brightness dips have been recently observed in images of protoplanetary disks, and they are believed to be shadows by the inner disk. We present VLT/SPHERE polarimetric differential imaging transition disk around dipper star RX J1604.3-2130. gathered 11 epochs that cover a large temporal baseline, search for variability over timescales years, months, weeks, days. Our observations unambiguously reveal two along an almost face-on narrow ring (with width $\sim$20 au), location peak this is...
The evolution of young stars and disks is driven by the interplay several processes, notably accretion ejection material. Critical to correctly describe conditions planet formation, these processes are best probed spectroscopically. About five-hundred orbits Hubble Space Telescope (HST) being devoted in 2020-2022 ULLYSES public survey about 70 low-mass (M<2Msun) (age<10 Myr) at UV wavelengths. Here we present PENELLOPE Large Program that carried out ESO Very (VLT) acquire,...
We present the first identification of low-mass (spectral types K–M) stars in young clusters Tr 37 and NGC 7160, members CepOB2 association. This is part a program to follow evolution protoplanetary accretion disks through ages thought be crucial understanding disk dissipation planet formation (∼3–10 Myr). Combining optical photometry spectroscopy, we have identified ∼40 ∼15 using several independent tests for determining membership (optical colors, variability, Hα emission, Li λ6707...
We report on the results of an optical spectroscopic survey designed to confirm youth and determine spectral types among a sample young stellar object (YSO) candidates in Serpens molecular cloud. observed 150 infrared (IR) excess objects previously discovered by Spitzer Legacy Program "From Molecular Cores Planet-Forming Disks" (c2d), bright enough for subsequent Spitzer/InfraRed Spectrograph (IRS) spectroscopy. obtained 78 spectra sufficient signal-to-noise analysis. Extinctions, effective...
We present optical and IR spectra of a set low-mass stars brown dwarfs in the Coronet cluster (aged ~1 Myr), obtained with multifiber spectrograph FLAMES on VLT IRS instrument Spitzer. Most objects had been selected via their X-ray emission deep Chandra survey. The reveal spectral types between M1 M7.5, confirm youth (via Li λ6708 absorption), show presence accretion Hα) shocks forbidden line emission). spectra, together photometry from IRAC/MIPS instruments Spitzer 2MASS, excesses...
We present Spitzer 3.6–24 μm photometry and spectroscopy for stars in the 1–3 Myr old Coronet Cluster, expanding upon survey of Sicilia-Aguilar et al. Using sophisticated radiative transfer models, we analyze these new data those from to identify disks with evidence substantial dust evolution consistent disk clearing: transitional disks. then Taurus others young clusters—IC 348, NGC 2362, η Cha—to constrain frequency as a function time. Our analysis confirms previous results finding two...
EX Lup is the prototype of EXor class eruptive young stars. These objects show optical outbursts which are thought to be related runaway accretion onto star. In a previous study we observed in situ crystal formation disk during its latest outburst 2008, making object an ideal laboratory investigate circumstellar and transport. This was monitored by campaign ground-based Spitzer Space Telescope observations. Here modeled spectral energy distribution (SED) from millimeter wavelengths with...
Context. Taurus represents an ideal region to study the three-dimensional distribution of young stellar population and relate it associated molecular cloud. Aims. The second Gaia data release (DR2) enables us investigate complex in three dimensions, starting from a previously defined robust membership. cloud structured filaments can be traced emission using public far-infrared maps Herschel. Methods. From compiled catalog spectroscopically confirmed members, we analyze 283 sources with...