Abstract
We report on the properties of the low-mass stars that recently formed in the central
of 30 Dor, including the R136 cluster. Using the photometric catalog of De Marchi et al., based on ...observations with the
Hubble Space Telescope
, and the most recent extinction law for this field, we identify
bona fide pre-main-sequence (PMS) stars showing
excess emission at the
level with an
equivalent width of 20 Å or more. We find a wide spread in age spanning the range
. We also find that the older PMS objects are placed in front of the R136 cluster and are separated from it by a conspicuous amount of absorbing material, indicating that star formation has proceeded from the periphery into the interior of the region. We derive physical parameters for all PMS stars, including masses
m
, ages
t
, and mass accretion rates
. To identify reliable correlations between these parameters, which are intertwined, we use a multivariate linear regression fit of the type
. The values of
a
and
b
for 30 Dor are compatible with those found in NGC 346 and NGC 602. We extend the fit to a uniform sample of
PMS stars with
/
< 1.5 and
in six star-forming regions in the Large and Small Magellanic Clouds and Milky Way with metallicities in the range of 0.1–1.0
. We find
and
. The residuals are systematically different between the six regions and reveal a strong correlation with metallicity
Z
, of the type
. A possible interpretation of this trend is that when the metallicity is higher so is the radiation pressure, and this limits the accretion process, in both its rate and duration.
ABSTRACT Using Gaia DR2 data, combined with OmegaCAM ground-based optical photometry from the Accretion Disc with OmegaCAM survey, and detailed radial velocity measurements from ESO-Gaia, we analyse ...in detail a 10 × 5 deg region around the Wolf–Rayet Star γ2 Vel, including the previously known clusters Gamma Vel and NGC2547. Using clustering analysis that considers positions, proper motions, and parallax, we discover six clusters or associations – four of which appear new. Analysis of the colour–magnitude diagram for these clusters shows that four of them formed coevally from the same molecular clouds 10 Myr ago, while NGC 2547 formed together with a newly discovered cluster 30 Myr ago. This study shows the incredible wealth of data provided by Gaia for the study of young stellar clusters.
Abstract
We report on the accretion properties of low-mass stars in the LH 95 association within the Large Magellanic Cloud. Using noncontemporaneous wideband optical and narrowband H
α
photometry ...obtained with the
Hubble Space Telescope
, we identify 245 low-mass pre-main-sequence (PMS) candidates showing H
α
excess emission above the 4
σ
level. We derive their physical parameters, including effective temperatures, luminosities, masses (
M
⋆
), ages, accretion luminosities, and mass accretion rates (
). We identify two different stellar populations: younger than ∼8 Myr with median
yr
−1
(and
M
⋆
∼ 0.15–1.8
M
⊙
) and older than ∼8 Myr with median
yr
−1
(and
M
⋆
∼ 0.6–1.2
M
⊙
). We find that the younger PMS candidates are assembled in groups around Be stars, while older PMS candidates are uniformly distributed within the region without evidence of clustering. We find that
in LH 95 decreases with time more slowly than what is observed in Galactic star-forming regions (SFRs). This agrees with the recent interpretation, according to which higher metallicity limits the accretion process in both rate and duration due to higher radiation pressure. The
–
M
⋆
relationship shows different behavior at different ages, becoming progressively steeper at older ages, indicating that the effects of mass and age on
cannot be treated independently. With the aim to identify reliable correlations between mass, age, and
, we used a multivariate linear regression fit between these parameters for our PMS candidates. The comparison between our results and those obtained in other SFRs of our Galaxy and the Magellanic Clouds confirms the importance of the metallicity for the study of the
evolution in clusters with different environmental conditions.
We have studied the interstellar extinction in a field of ∼3 arcmin × 3 arcmin at the core of the 30 Doradus nebula, including the central R 136 cluster, in the Large Magellanic Cloud. Observations ...at optical and near-infrared wavelengths, obtained with the WFC 3 camera on board the Hubble Space Telescope, show that the stars belonging to the red giant clump are spread across the colour–magnitude diagrams because of the considerable and uneven levels of extinction in this region. Since these stars share very similar physical properties and are all at the same distance, they allow us to derive the absolute extinction in a straightforward and reliable way. Thus, we have measured the extinction towards about 180 objects and the extinction law in the range 0.3–1.6 μm. At optical wavelengths, the extinction curve is almost parallel to that of the diffuse Galactic interstellar medium. Taking the latter as a template, the value of R
V
= 4.5 ± 0.2 that we measure indicates that in the optical there is an extra grey component due to a larger fraction of large grains. At wavelengths longer than ∼1 μm, the contribution of this additional component tapers off as λ−1.5, like in the Milky Way, suggesting that the nature of the grains is otherwise similar to those in our Galaxy, but with a ∼2.2 times higher fraction of large grains. These results are consistent with the addition of ‘fresh’ large grains by supernova explosions, as recently revealed by Herschel and ALMA (Atacama Large Millimeter Array) observations of SN 1987A.
We present new optical observations of the supernova SN 1978K, obtained in 2007 and 2014 with the Very Large Telescope. We discover that the supernova has not faded significantly, even more than ...three decades after its explosion. The spectrum exhibits numerous narrow (FWHM ≲600 km s−1) emission lines, indicating that the supernova blastwave is persistently interacting with dense circumstellar material (CSM). Evolution of emission lines indicates that the supernova ejecta is slowly progressing through the reverse shock, and has not expanded past the outer edge of the circumstellar envelope. We demonstrate that the CSM is not likely to be spherically distributed, with mass of ≲1 M⊙. The progenitor mass loss rate is estimated as ≳0.01 M⊙ yr−1. The slowly fading late-time light curve and spectra show striking similarity with SN 1987A, indicating that a rate at which the CSM is being swept-up by the blastwave is gradually decaying and SN 1978K is undergoing similar evolution to become a remnant. Due to its proximity (4 Mpc), SN 1978K serves as the next best example of late-time supernova evolution after SN 1987A.
ESASky is a science-driven discovery portal to explore the multi-wavelength sky and visualize and access multiple astronomical archive holdings. The tool is a web application that requires no prior ...knowledge of any of the missions involved and gives users world-wide simplified access to the highest-level science data products from multiple astronomical space-based astronomy missions plus a number of ESA source catalogs. The first public release of ESASky features interfaces for the visualization of the sky in multiple wavelengths, the visualization of query results summaries, and the visualization of observations and catalog sources for single and multiple targets. This paper describes these features within ESASky, developed to address use cases from the scientific community. The decisions regarding the visualization of large amounts of data and the technologies used were made to maximize the responsiveness of the application and to keep the tool as useful and intuitive as possible.
We measured the extinction law in the 30 Dor star formation region in the Large Magellanic Cloud using Early Release Observations (EROs) taken with Near-Infrared Camera (NIRCam) on board the JWST, ...thereby extending previous studies carried out with the
Hubble
Space Telescope to the infrared. We used red clump stars to derive the direction of the reddening vector in twelve bands and we present the extinction law in this massive star forming region from 0.3 to 4.7 μm. At wavelengths longer than 1 μm, we find a ratio of total and selective extinction twice as high as in the diffuse Milky Way interstellar medium and a change in the relative slope from the optical to the infrared domain. Additionally, we derive an infrared extinction map and find that extinction closely follows the structure of the highly embedded regions of 30 Dor.
The 30 Doradus region in the Large Magellanic Cloud (LMC) is the most energetic star-forming region in the Local Group. It is powered by the feedback from the massive stars in R 136, the 1–2 Myr old ...central massive cluster. 30 Doradus has therefore long been regarded as a laboratory for studying star and star cluster formation under conditions reminiscent of the early Universe. We use JWST NIRCam observations to analyse how star formation proceeds in the region. Using selections based on theoretical isochrones on colour-magnitude diagrams, we identify populations of different ages. We select pre-main-sequence (PMS) stars and young stellar objects that show excess emission from warm dust or emission lines. Studying the spatial distribution of the different populations, we find that the youngest PMS stars with ages <0.5 Myr are located in an elongated structure that stretches towards the north-east from the central cluster. The same structure is found in the sources that show an infrared excess, appears to be overlapping with cold molecular gas, and covers previously investigated sites of ongoing star formation. Pre-main-sequence stars with ages between 1 and 4 Myr and upper main-sequence stars are concentrated in the centre of R 136, while older stars are more uniformly distributed across the field and likely belong to the LMC field population. Nonetheless, we find stars with excess emission from on dust or emission lines as far as 100 pc from the centre, indicating extended recent star formation. We interpret the elongated structure formed by the youngest PMS stars to be an indication of the still-ongoing hierarchical assembly of the R 136 cluster. Additionally, the lower density of old PMS stars with emission due to ongoing accretion in the central region suggests that feedback from the R 136 stars is effective in disrupting the disks of PMS stars.
Abstract
JWST Near Infrared Camera (NIRCam) observations at 1.5–4.5
μ
m have provided broadband and narrowband imaging of the evolving remnant of SN 1987A with unparalleled sensitivity and spatial ...resolution. Comparing with previous marginally spatially resolved Spitzer Infrared Array Camera (IRAC) observations from 2004 to 2019 confirms that the emission arises from the circumstellar equatorial ring (ER), and the current brightness at 3.6 and 4.5
μ
m was accurately predicted by extrapolation of the declining brightness tracked by IRAC. Despite the regular light curve, the NIRCam observations clearly reveal that much of this emission is from a newly developing outer portion of the ER. Spots in the outer ER tend to lie at position angles in between the well-known ER hotspots. We show that the bulk of the emission in the field can be represented by five standard spectral energy distributions, each with a distinct origin and spatial distribution. This spectral decomposition provides a powerful technique for distinguishing overlapping emission from the circumstellar medium and the supernova ejecta, excited by the forward and reverse shocks, respectively.
Despite the growing importance of planetary Space Weather forecasting and radiation protection for science and robotic exploration and the need for accurate Space Weather monitoring and predictions, ...only a limited number of spacecraft have dedicated instrumentation for this purpose. However, every spacecraft (planetary or astronomical) has hundreds of housekeeping sensors distributed across the spacecraft, some of which can be useful to detect radiation hazards produced by solar particle events. In particular, energetic particles that impact detectors and subsystems on a spacecraft can be identified by certain housekeeping sensors, such as the Error Detection and Correction (EDAC) memory counters, and their effects can be assessed. These counters typically have a sudden large increase in a short time in their error counts that generally match the arrival of energetic particles to the spacecraft. We investigate these engineering datasets for scientific purposes and perform a feasibility study of solar energetic particle event detections using EDAC counters from seven European Space Agency Solar System missions: Venus Express, Mars Express, ExoMars‐Trace Gas Orbiter, Rosetta, BepiColombo, Solar Orbiter, and Gaia. Six cases studies, in which the same event was observed by different missions at different locations in the inner Solar System are analyzed. The results of this study show how engineering sensors, for example, EDAC counters, can be used to infer information about the solar particle environment at each spacecraft location. Therefore, we demonstrate the potential of the various EDAC to provide a network of solar particle detections at locations where no scientific observations of this kind are available.
Plain Language Summary
Space Weather is the discipline that aims at understanding and predicting the state of the Sun, interplanetary medium and its impact on planetary environments. One source of Space Weather is Solar Energetic Particles (SEPs), which are emitted by the Sun and enhance the radiation and particles that flow in space. Predicting the motion of these particles is important but difficult as we need good satellite coverage of the entire inner Solar System, and only a limited number of spacecraft have the necessary instrumentation. Thanks to the European Space Agency flotilla, that is, Venus Express, Mars Express, ExoMars‐Trace Gas Orbiter, Rosetta, BepiColombo, Solar Orbiter, and Gaia, we performed a feasibility study of the detection of SEP events using engineering sensors in the main body of the spacecraft that were originally placed there to monitor its health during the mission. We explored how much scientific information we can get from these engineering sensors, such as the timing and duration of an SEP impacting the spacecraft, or the minimum energy of those particles to trigger a detection. The results of this study have the potential of providing a good network of solar particle detections at locations where no scientific observations are available.
Key Points
Space weather detections using housekeeping datasets on European Space Agency spacecraft
Some engineering datasets on spacecraft have the potential to be used for science
Same Space Weather events detected with housekeeping data at widely‐spaced locations in the Solar System
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