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Mosaic of IPHAS observations towards NGC 2264 in the Hα band. A few narrow black bands can be seen, which indicate small gaps of missing data which will be completed in a future IPHAS data release.
Source publication
There are many pertinent open issues in the area of star and planet
formation. Large statistical samples of young stars across star-forming regions
are needed to trigger a breakthrough in our understanding, but most optical
studies are based on a wide variety of spectrographs and analysis methods,
which introduces large biases. Here we show how gra...
Contexts in source publication
Context 1
... used the Montage toolkit to create an Hα mosaic of 20 fields towards the region which is shown in Fig. 9. The contrast of the mosaic has been stretched using an arcsinh curve to bring out the Hα background ...
Context 2
... of the deep optical CFHT observations (dash-dotted line), Spitzer IRAC observations (dashed line) and Chandra observations (solid line). A few objects fall outside these footprints, because they were included on the basis of bright optical photometry or literature spectroscopy (footprints not shown). The background image is an inverted version of Fig. ...
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Context. The first Gaia Data Release contains the Tycho - Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and parallax are calculated using H ipparcos and Tycho-2 positions in 1991.25 as prior information.
Aims. We investigate the scientific potential and...
The ESA GAIA spacecraft has been approved for launch by a Soyuz-Fregat launcher in December 2011. After five years continuously scanning the sky, astrometric, photometric and spectroscopic data for a billion objects down to V˜20 will be acquired. That huge survey of the Galaxy content and beyond will provide insights to the origin and evolution of...
We present observational constraints on the initial-final mass relation
(IFMR) using wide double white dwarfs (DWDs). We identify 65 new candidate wide
DWDs within the Sloan Digital Sky Survey, bringing the number of candidate wide
DWDs to 142. We then engage in a spectroscopic follow-up campaign and collect
existing spectra for these objects; usin...
Citations
... Nonetheless, some areas in the vs. diagram with a relatively high density of H -excess candidates can be highlighted. These might correspond, say, to regions with a high rate of star formation, such as molecular clouds Barentsen et al. 2013), which are easily identifiable in Fig. 8. The latter star-forming region has been the subject of previous studies, such as the one presented by Barentsen et al. (2013). ...
... These might correspond, say, to regions with a high rate of star formation, such as molecular clouds Barentsen et al. 2013), which are easily identifiable in Fig. 8. The latter star-forming region has been the subject of previous studies, such as the one presented by Barentsen et al. (2013). They applied the method of the Bayesian inference to identify 115 accreting objects in NGC2264. ...
We present a catalogue of point-like Hα-excess sources in the Northern Galactic Plane. Our catalogue is created using a new technique that leverages astrometric and photomeric information from Gaia to select Hα-bright outliers in the INT Photometric Hα Survey of the Northern Galactic Plane (IPHAS), across the colour-absolute magnitude diagram. To mitigate the selection biases due to stellar population mixing and to extinction, the investigated objects are first partitioned with respect to their positions in the Gaia colour-absolute magnitude space, and in the Galactic coordinates space, respectively. The selection is then performed on both partition types independently. Two significance parameters are assigned to each target, one for each partition type. These represent a quantitative degree of confidence that the given source is a reliable Hα-excess candidate, with reference to the other objects in the corresponding partition. Our catalogue provides two flags for each source, both indicating the significance level of the Hα-excess. By analysing their intensity in the Hα narrow band, 28,496 objects out of 7,474,835 are identified as Hα-excess candidates with a significance higher than 3. The completeness fraction of the Hα outliers selection is between $3{{\ \rm per\ cent}}$ and $5{{\ \rm per\ cent}}$. The suggested 5σ conservative cut yields a purity fraction of $81.9{{\ \rm per\ cent}}$.
... Nonetheless, some areas in the vs. diagram with a relatively high density of H -excess candidates can be highlighted. These might correspond, say, to regions with a high rate of star formation, such as molecular clouds Barentsen et al. 2013), which are easily identifiable in Fig. 8. The latter star-forming region has been the subject of previous studies, such as the one presented by Barentsen et al. (2013). ...
... These might correspond, say, to regions with a high rate of star formation, such as molecular clouds Barentsen et al. 2013), which are easily identifiable in Fig. 8. The latter star-forming region has been the subject of previous studies, such as the one presented by Barentsen et al. (2013). They applied the method of the Bayesian inference to identify 115 accreting objects in NGC2264. ...
We present a catalogue of point-like H{\alpha}-excess sources in the Northern Galactic Plane. Our catalogue is created using a new technique that leverages astrometric and photomeric information from Gaia to select H{\alpha}-bright outliers in the INT Photometric H{\alpha} Survey of the Northern Galactic Plane (IPHAS), across the colour-absolute magnitude diagram. To mitigate the selection biases due to stellar population mixing and to extinction, the investigated objects are first partitioned with respect to their positions in the Gaia colour-absolute magnitude space, and in the Galactic coordinates space, respectively. The selection is then performed on both partition types independently. Two significance parameters are assigned to each target, one for each partition type. These represent a quantitative degree of confidence that the given source is a reliable H{\alpha}-excess candidate, with reference to the other objects in the corresponding partition. Our catalogue provides two flags for each source, both indicating the significance level of the H{\alpha}-excess. By analysing their intensity in the H{\alpha} narrow band, 28,496 objects out of 7,474,835 are identified as H{\alpha}-excess candidates with a significance higher than 3. The completeness fraction of the H{\alpha} outliers selection is between 3% and 5%. The suggested 5{\sigma} conservative cut yields a purity fraction of 81.9%.
... This paper presents the discovery and characterization of Mon-735 as a young low-mass pre-main-sequence (PMS) EB member of NGC 2264. The source has been previously identified as a T Tauri-type member of NGC 2264 based on ultraviolet excess and/or optical variability (Rebull et al. 2002;Lamm et al. 2004;Barentsen et al. 2013;Venuti et al. 2014) and is listed as an EB in the surrounding CoRoT SRa01 field (Klagyivik et al. 2013). In Section 2, we introduce the photometric and spectroscopic observations. ...
We present Mon-735, a detached double-lined eclipsing binary (EB) member of the ∼3 Myr old NGC 2264 star-forming region, detected by Spitzer. We simultaneously model the Spitzer light curves, follow-up Keck/HIRES radial velocities, and the system’s spectral energy distribution to determine self-consistent masses, radii, and effective temperatures for both stars. We find that Mon-735 comprises two pre-main-sequence M dwarfs with component masses of M = 0.2918 ± 0.0099 and 0.2661 ± 0.0095 M⊙, radii of R = 0.762 ± 0.022 and 0.748 ± 0.023 R⊙, and effective temperatures of Teff = 3260 ± 73 and 3213 ± 73 K. The two stars travel on circular orbits around their common centre of mass in P = 1.9751388 ± 0.0000050 d. We compare our results for Mon-735, along with another EB in NGC 2264 (CoRoT 223992193), to the predictions of five stellar evolution models. These suggest that the lower mass EB system Mon-735 is older than CoRoT 223992193 in the mass–radius diagram (MRD) and, to a lesser extent, in the Hertzsprung–Russell diagram (HRD). The MRD ages of Mon-735 and CoRoT 223992193 are ∼7–9 and 4–6 Myr, respectively, with the two components in each EB system possessing consistent ages.
... This paper presents the discovery and characterisation of Mon-735 as a young low-mass pre-main sequence (PMS) EB member of NGC 2264. The source has been previously identified as a T Tauri type member of NGC 2264 based on ultraviolet excess and/or optical variability (Rebull et al. 2002;Lamm et al. 2004;Barentsen et al. 2013;Venuti et al. 2014) and is listed as an EB in the surrounding CoRoT SRa01 field (Klagyivik et al. 2013). In §2 we introduce the photometric and spectroscopic observations. ...
We present Mon-735, a detached double-lined eclipsing binary (EB) member of the $\sim$3 Myr old NGC 2264 star forming region, detected by Spitzer. We simultaneously model the Spitzer light curves, follow-up Keck/HIRES radial velocities, and the system's spectral energy distribution to determine self-consistent masses, radii and effective temperatures for both stars. We find that Mon-735 comprises two pre-main sequence M dwarfs with component masses of $M = 0.2918 \pm 0.0099$ and $0.2661 \pm 0.0095$ $\rm{M}_{\odot}$, radii of $R = 0.762 \pm 0.022$ and $0.748 \pm 0.023$ $\rm{R}_{\odot}$, and effective temperatures of $T_{\rm eff} = 3260 \pm 73$ and $3213 \pm 73$ $\rm{K}$. The two stars travel on circular orbits around their common centre of mass in $P = 1.9751388 \pm 0.0000050$ days. We compare our results for Mon-735, along with another EB in NGC 2264 (CoRoT 223992193), to the predictions of five stellar evolution models. These suggest that the lower mass EB system Mon-735 is older than CoRoT 223992193 in the mass-radius diagram (MRD) and, to a lesser extent, in the Hertzsprung-Russell diagram (HRD). The MRD ages of Mon-735 and CoRoT 223992193 are $\sim$7-9 and 4-6 Myr, respectively, with the two components in each EB system possessing consistent ages.
... The famous big data problem researcher Viktor Meyer-Schonberg once said that the essence of the world is data and the era of big data will open a major era transformation [6]. The rise of big data is not just a technologically flourishing or over-rewarding, it is probably a revolution that changes the way people live and understand the world [7]. ...
The similarities and differences between the K-means algorithm and the Canopy algorithm’s MapReduce implementation are described in detail, and the possibility of combining the two to design a better algorithm suitable for clustering analysis of large data sets is analyzed in this paper. Different from the previous literature’s improvement ideas for K-means algorithm, it proposes new ideas for sampling and analyzes the selection of relevant thresholds in this paper. Finally, it introduces the MapReduce implementation framework based on Canopy partitioning and filtering K-means algorithm and analyzes some pseudocode in this chapter. Finally, it briefly analyzes the time complexity of the algorithm in this paper.
... mag, along with an emission index of a -= r H 0.89 0.02 mag. According to the models in Figure 2 of Barentsen et al. (2013), the source would be an obvious Hα emitter, with an equivalent width of several tens of Angstroms. ...
We report on the source Gaia 19ajj, identifying it as a young star associated with a little-studied star-forming region seen along a complex line of sight through the Gum Nebula. The optical lightcurve recently recorded by Gaia exhibits a slow and unsteady 5.5 mag rise over about 3 yr, while the mid-infrared lightcurve from NEOWISE over the same time period shows a 1.2 mag rise having similar structure. Available color information is inconsistent with pure extinction reduction as the cause for the photometric brightening. Optical spectroscopic characteristics in the current bright phase include: little in the way of absorption except for the hallmark Li I 6707 Å signature of youth plus weak, e.g., Ca I and notably Ba II; strong wind/outflow in Ca II, Mg I b, Na I D, Hα, K I, and O I; jet signatures in [O I], [S II], [Ca II], [Fe II], and [Ni II]; and narrow rest-velocity emission in neutral species such as Fe I, Ni I, and Mg I. The infrared spectrum is also characterized by outflow and emission, including: a hot He I wind, jet lines such as [Fe II] and H2; and weak narrow rest-velocity atomic line emission. The ¹²CO bandheads are weakly in emission, but there is also broad H₂O absorption. Gaia 19ajj exhibited a previous bright state in the 2010–2012 time frame. The body of photometric and spectroscopic evidence suggests that the source bears resemblance to V2492 Cyg (PTF 10nvg) and PV Cep, both of which similarly experience bright phases that recur on long timescales, with large-amplitude photometric variations and emission-dominated spectra. We interpret the behavior of Gaia 19ajj as caused by cycles of enhanced disk accretion accompanied by reduced extinction.
... As for L Hα , the statistical uncertainty on EW Hα , typically ∼6%, is dominated by the uncertainty on the Hα photometry. The validity of this method was also independently tested and then confirmed by Barentsen et al. (2011Barentsen et al. ( , 2013, who considered both photometric and spectroscopic observations for T Tauri stars in the Galactic NGC 2264 and IC 1396 young regions. The authors found a strong correlation between Hα equivalent widths derived with both spectroscopic and photometric methods. ...
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 Hα photometry obtained with the Hubble Space Telescope, we identify 245 low-mass pre-main-sequence (PMS) candidates showing Hα excess emission above the 4σ 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.
... The iPHaS catalog ( Barentsen et al. 2014) provides r − Hα color of 0.88±0.29 mag, but the very red r−i color of 2.63±0.18 mag (Figure 4) does not make the source an obvious Hα emitter, according to the models in Figure 2 of Barentsen et al. (2013). ...
We report on the source Gaia 17bpi and identify it as a new, ongoing FU Ori-type outburst, associated with a young stellar object. The optical light curve from Gaia exhibited a 3.5 mag rise with the source appearing to plateau in mid-/late 2018. Mid-infrared observations from NEOWISE also show a >3 mag rise that occurred in two stages, with the second one coincident with the optical brightening, and the first one preceding the optical brightening by ∼1.5 yr. We model the outburst as having started between October and December of 2014. This wavelength-dependent aspect of young star accretion-driven outbursts has never been documented before. Both the mid-infrared and the optical colors of the object become bluer as the outburst proceeds. Optical spectroscopic characteristics in the outburst phase include: a GK-type absorption spectrum, strong wind/outflow in, e.g., Mgb, NaD, Hα, K i, O i, and Ca ii profiles, and detection of Li i 6707 Å. The infrared spectrum in the outburst phase is similar to that of an M-type spectrum, notably exhibiting prominent H2O and ¹²CO (2-0) bandhead absorption in the K band, and likely He i wind in the Y band. The new FU Ori source Gaia 17bpi is associated with a little-studied dark cloud in the galactic plane, located at a distance of 1.27 kpc. © 2018. The American Astronomical Society. All rights reserved..
... We use a Bayesian approach to infer the family of solutions that can describe the behavior of the degree of polarization with wavelength. In this case, we use the PyMC3 4 framework for Python, which has been successfully applied to a variety of astrophysical problems (Genet et al. 2010;Barentsen et al. 2013;Wilkins et al. 2013;Waldmann & Pascale 2014;. PyMC3 is a Python module for Bayesian statistical modeling and model inference using Markov chain Monte Carlo (MCMC) algorithms. ...
We present high-angular (0.17$-$0.35 arcsec) resolution imaging polarimetric observations of Mrk 231 in the 3.1 $\mu$m filter using MMT-Pol on the 6.5-m MMT, and in the 8.7 $\mu$m, 10.3 $\mu$m, and 11.6 $\mu$m filters using CanariCam on the 10.4-m Gran Telescopio CANARIAS. In combination with already published observations, we compile the 1$-$12 $\mu$m total and polarized nuclear spectral energy distribution (SED). The total flux SED in the central 400 pc is explained as the combination of 1) a hot (731 $\pm$ 4 K) dusty structure, directly irradiated by the central engine, which is at 1.6 $\pm$ 0.1 pc away and attributed to be in the pc-scale polar region, 2) an optically-thick, smooth and disk-like dusty structure (`torus') with an inclination of 48 $\pm$ 23$^{\circ}$ surrounding the central engine, and 3) an extinguished (A$_{\mbox{V}} =$ 36 $\pm$ 5 mag) starburst component. The polarized SED decreases from 0.77 $\pm$ 0.14 per cent at 1.2 $\mu$m to 0.31 $\pm$ 0.15 per cent at 11.6 $\mu$m and follows a power-law function, $\lambda^{\sim0.57}$. The polarization angle remains constant ($\sim$108$^{\circ}$) in the 1$-$12 $\mu$m wavelength range. The dominant polarization mechanism is explained as scattering off hot dust grains in the pc-scale polar regions.
... In this paper, we use the PyMC3 1 framework for Python, which has been successfully applied to a variety of astrophysical problems (e.g. Genet et al. 2010;Barentsen et al. 2013;Wilkins et al. 2013;Waldmann & Pascale 2014). PyMC3 is a Python module for Bayesian statistical modeling and , a Hamiltonian MCMC that avoids the random walk behavior and sensitivity of other MCMC algorithms by taking a series of steps through a first-order gradient information. ...
A fast and general Bayesian inference framework to infer the physical properties of dichroic polarization using mid-infrared
imaging- and spectro-polarimetric observations is presented. The Bayesian approach is based on a hierarchical regression and
No-U-Turn Sampler method. This approach simultaneously infers the normalized Stokes parameters to find the full family of
solutions that best describe the observations. In comparison with previous methods, the developed Bayesian approach allows
the user to introduce a customized absorptive polarization component based on the dust composition, and the appropriate extinction
curve of the object. This approach allows the user to obtain more precise estimations of the magnetic-field strength and geometry
for tomographic studies, and information about the dominant polarization components of the object. Based on this model, imaging-polarimetric
observations using two or three filters located in the central 9.5–10.5 μm, and the edges 8–9 μm and/or 11–13 μm, of the wavelength
range are recommended to optimally disentangle the polarization mechanisms.
