Young Stellar Object Candidates Toward the Orion Region Selected from GALEX (Research Note)
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Interstellar Extinction in Orion. Variation of the Strength of the UV
MNRAS 000, 1–9 (2017) Preprint 9 July 2018 Compiled using MNRAS LATEX style file v3.0 Interstellar extinction in Orion. Variation of the strength of the UV bump across the complex. Leire Beitia-Antero,1⋆ Ana I. G´omez de Castro,1† 1AEGORA Research Group, Universidad Complutense de Madrid, Facultad de CC. Matem´aticas, Plaza de Ciencias 3, E-28040 Madrid Accepted XXX. Received YYY; in original form ZZZ ABSTRACT There is growing observational evidence of dust coagulation in the dense filaments within molecular clouds. Infrared observations show that the dust grains size distri- bution gets shallower and the relative fraction of small to large dust grains decreases as the local density increases. Ultraviolet (UV) observations show that the strength of the 2175 A˚ feature, the so-called UV bump, also decreases with cloud density. In this work, we apply the technique developed for the Taurus study to the Orion molecular cloud and confirm that the UV bump decreases over the densest cores of the cloud as well as in the heavily UV irradiated λ Orionis shell. The study has been extended to the Rosette cloud with uncertain results given the distance (1.3 kpc). Key words: ISM: dust, extinction 1 INTRODUCTION feature of the extinction curve, the so-called UV bump. The UV bump is, by far, the strongest spectral feature in the ex- The Interstellar Medium (ISM) is a complex ensemble of tinction curve but its source remains uncertain (see e.g. the gas, large molecules and dust coupled through the action of review by Draine (2003)). -
Cassiopeia a January2008
CASSIOPEIA A JANUARY2008 Cassiopeia A is the youngest (about 300 years old) known supernova Su Mo Tu We Th Fr Sa remnant in the Milky Way. Astronomers have used Chandra’s long ob - 01 02 03 04 05 servations of this remnant to make a map of the acceleration of elec - trons in this supernova remnant. The analysis shows that the electrons 06 07 08 09 10 11 12 are being accelerated to almost the maximum theoretical limit in some 13 14 15 16 17 18 19 parts of Cassiopeia A (Cas A) in what can be thought of as a “relativistic pinball machine.” Protons and ions, which make up the bulk of cosmic 20 21 22 23 24 25 26 rays, are expected to be accelerated in a similar way to the electrons. The Cas A observations thus provide strong evidence that supernova 27 28 29 30 31 remnants are key sites for energizing cosmic rays. 3C442A FEBRUARY2008 X -ray data from NASA’s Chandra X -ray Observatory and radio obser - Su Mo Tu We Th Fr Sa vations from the NSF’s Very Large Array show that a role reversal is 01 02 taking place in the middle of 3C442A - a system with two merging gal - 03 04 05 06 07 08 09 axies in the center. Chandra detects hot gas (blue) that has been push - ing aside the radio -bright gas (orange). This is the opposite of what 10 11 12 13 14 15 16 is typically found in these systems when jets from the supermassive black hole in the center create cavities in the hot gas surrounding the 17 18 19 20 21 22 23 galaxy. -
Multicolor Photometric Behavior of the Young Stellar Object V1704 Cygni
Multicolor photometric behavior of the young stellar object V1704 Cygni Sunay Ibryamov1, Evgeni Semkov2, Stoyanka Peneva2, U˘gur Karadeniz3 1 Department of Physics and Astronomy, University of Shumen, 115, Universitetska Str., 9700 Shumen, Bulgaria 2 Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, 72, Tsarigradsko Shose Blvd., 1784 Sofia, Bulgaria 3 Department of Physics, Izmir Institute of Technology, Urla, 35430 Izmir, Turkey [email protected] (Submitted on 22.01.2018. Accepted on 20.02.2018) Abstract. Results from BV RI photometric observations of the pre-main sequence star V1704 Cyg collected during the time period from August 2010 to December 2017 are presented. The star is located in the star-forming HII region IC 5070 and it exhibits photometric variability in all optical passbands. After analyzing the obtained data, V1704 Cyg is classified as a classical T Tauri star. Key words: stars: pre-main sequence, stars: variables: T Tauri, star: individual: (V1704 Cyg) 1. Introduction One of the most frequent types of pre-main sequence (PMS) stars are the low-mass (M ≤ 2M⊙) T Tauri stars (TTSs). The first study of the TTSs as a separate class of variables with the prototype star T Tau was made by Joy (1945). These stars show irregular photometric variability and emission spectra. TTSs are divided into two sub-classes: classical T Tauri stars (CTTSs) still actively accreting from their massive circumstellar disks and the weak- line T Tauri stars (WTTSs) without evidence of disk accretion (M´enard -
Theoretical Limits of Star Sensor Accuracy †
sensors Article Theoretical Limits of Star Sensor Accuracy † Marcio A. A. Fialho 1,* and Daniele Mortari 2 1 Divisão de Eletrônica Aeroespacial (DIDEA), National Institute for Space Research (INPE), Av. dos Astronautas, 1758, São José dos Campos, SP 12227, Brazil 2 Aerospace Engineering, Texas A&M University, College Station, TX 77843, USA; [email protected] * Correspondence: marcio.fi[email protected]; Tel.: +55-12-3208-6145 † This paper is a revised and extended version of a work previously published as a doctoral thesis chapter. Received: 17 October 2019; Accepted: 25 November 2019; Published: 5 December 2019 Abstract: To achieve mass, power and cost reduction, there is a trend to reduce the volume of many instruments aboard spacecraft, especially for small spacecraft (cubesats or nanosats) with very limited mass, volume and power budgets. With the current trend of miniaturizing spacecraft instruments one could naturally ask if is there a physical limit to this process for star sensors. This paper shows that there is a fundamental limit on star sensor accuracy, which depends on stellar distribution, star sensor dimensions and exposure time. An estimate of this limit is given for our location in the galaxy. Keywords: star sensors; stellar distribution; photometry; astrometry; star catalogs; fundamental limits 1. Introduction Much progress in a variety of fields in science and technology could be accomplished thanks to the miniaturization obtained in microelectronics in the recent decades. One of the most remarkable examples is the prediction by Gordon Moore that the computational power would increase exponentially, an empirical observation that became known as Moore’s law [1–4]. -
The Spitzer Space Telescope and the IR Astronomy Imaging Chain
Spitzer Space Telescope (A.K.A. The Space Infrared Telescope Facility) The Infrared Imaging Chain Fundamentals of Astronomical Imaging – Spitzer Space Telescope – 8 May 2006 1/38 The infrared imaging chain Generally similar to the optical imaging chain... 1) Source (different from optical astronomy sources) 2) Object (usually the same as the source in astronomy) 3) Collector (Spitzer Space Telescope) 4) Sensor (IR detector) 5) Processing 6) Display 7) Analysis 8) Storage ... but steps 3) and 4) are a bit more difficult! Fundamentals of Astronomical Imaging – Spitzer Space Telescope – 8 May 2006 2/38 The infrared imaging chain Longer wavelength – need a bigger telescope to get the same resolution or put up with lower resolution Fundamentals of Astronomical Imaging – Spitzer Space Telescope – 8 May 2006 3/38 Emission of IR radiation Warm objects emit lots of thermal infrared as well as reflecting it Including telescopes, people, and the Earth – so collection of IR radiation with a telescope is more complicated than an optical telescope Optical image of Spitzer Space Telescope launch: brighter regions are those which reflect more light IR image of Spitzer launch: brighter regions are those which emit more heat Infrared wavelength depends on temperature of object Fundamentals of Astronomical Imaging – Spitzer Space Telescope – 8 May 2006 4/38 Atmospheric absorption The atmosphere blocks most infrared radiation Need a telescope in space to view the IR properly Fundamentals of Astronomical Imaging – Spitzer Space Telescope – 8 May 2006 5/38 -
Gao-21-306, Nasa
United States Government Accountability Office Report to Congressional Committees May 2021 NASA Assessments of Major Projects GAO-21-306 May 2021 NASA Assessments of Major Projects Highlights of GAO-21-306, a report to congressional committees Why GAO Did This Study What GAO Found This report provides a snapshot of how The National Aeronautics and Space Administration’s (NASA) portfolio of major well NASA is planning and executing projects in the development stage of the acquisition process continues to its major projects, which are those with experience cost increases and schedule delays. This marks the fifth year in a row costs of over $250 million. NASA plans that cumulative cost and schedule performance deteriorated (see figure). The to invest at least $69 billion in its major cumulative cost growth is currently $9.6 billion, driven by nine projects; however, projects to continue exploring Earth $7.1 billion of this cost growth stems from two projects—the James Webb Space and the solar system. Telescope and the Space Launch System. These two projects account for about Congressional conferees included a half of the cumulative schedule delays. The portfolio also continues to grow, with provision for GAO to prepare status more projects expected to reach development in the next year. reports on selected large-scale NASA programs, projects, and activities. This Cumulative Cost and Schedule Performance for NASA’s Major Projects in Development is GAO’s 13th annual assessment. This report assesses (1) the cost and schedule performance of NASA’s major projects, including the effects of COVID-19; and (2) the development and maturity of technologies and progress in achieving design stability. -
Pre-Main-Sequence Star
Pre-main-sequence star A pre-main-sequence star (also known as a PMS star and PMS object) is a star in the stage when it has not yet reached the main sequence. Earlier in its life, the object is a protostar that grows by acquiring mass from its surrounding envelope of interstellar dust and gas. After the protostar blows away this envelope, it is optically visible, and appears on the stellar birthline in the Hertzsprung-Russell diagram. At this point, the star has acquired nearly all of its mass but has not yet started hydrogen burning (i.e. nuclear fusion of hydrogen). The star then contracts, its internal temperature rising until it begins hydrogen burning on the zero age main sequence. This period of contraction is the pre-main sequence stage.[1][2][3][4] An observed PMS object can either be a T Tauri star, if it has fewer than 2 solar masses (M☉), or else a Herbig Ae/Be star, if it has 2 to 8 M☉. Yet more massive stars have no pre-main-sequence stage because they contract too quickly as protostars. By the time they become visible, the hydrogen in their centers is already fusing and they are main-sequence objects. The energy source of PMS objects is gravitational contraction, as opposed to hydrogen burning in main-sequence stars. In the Hertzsprung–Russell diagram, pre-main-sequence stars with more than 0.5 M☉ first move vertically downward along Hayashi tracks, then leftward and horizontally along Henyey tracks, until they finally halt at the main sequence. -
Experiments on the Differential Vlbi Measurements with the Former Russian Deep Space Network
EXPERIMENTS ON THE DIFFERENTIAL VLBI MEASUREMENTS WITH THE FORMER RUSSIAN DEEP SPACE NETWORK Igor E. Molotov(1,2,3) (1)Bear Lakes Radio Astronomy Station of Central (Pulkovo) Astronomical Observatory, Pulkovskoye chosse 65/1, Saint-Petersburg, 196140, Russia , E-mail: [email protected] (2)Keldysh Institute of Applied Mathematics, Miusskaja sq. 4, 125047 Moscow, Russia (3)Central Research Institute for Machine Building, 4 Pionerskaya Street, Korolev, 141070, Russia ABSTRACT The differential VLBI technique (delta-VLBI) is applied transforms the signals into video frequencies, which for measuring spacecraft position with accuracy up to 1 then are sampled with 1- or 2-bit quantization, formatted in any standard VLBI format (Mk-4, S2, K-4, mas. This procedure allows to link the sky position of object with the position of close ICRF quasar on the Mk-2) and recorded on magnetic tapes or PC-disks celestial sphere. Few delta-VLBI measurements can together with precise clock using VLBI terminal. All frequency transformations are connected with atomic urgently improve the knowledge of object trajectory in the times of critical maneuvers. frequency standard. The tapes/disks from all radio telescopes of VLBI array are collected at data The Russian Deep Space Network that was based on processing center, where the data are cross-correlated. three large antennas: 70 m in Evpatoria (Ukraine) and The processing is aimed to measure the time delay of Ussuriysk (Far East), and 64 m in Bear Lakes (near emitted wavefront arrival to receiving antennas, and Moscow) arranged the trial delta-VLBI experiments frequency of interference (fringe rate), that contain the with help of four scientific institutions. -
Simulated JWST Data Sets for Multispectral and Hyperspectral Image Fusion Claire Guilloteau, Thomas Oberlin, Olivier Berné, Émilie Habart, Nicolas Dobigeon
Simulated JWST data sets for multispectral and hyperspectral image fusion Claire Guilloteau, Thomas Oberlin, Olivier Berné, Émilie Habart, Nicolas Dobigeon To cite this version: Claire Guilloteau, Thomas Oberlin, Olivier Berné, Émilie Habart, Nicolas Dobigeon. Simulated JWST data sets for multispectral and hyperspectral image fusion. Astronomical Journal, American Astro- nomical Society, 2020, 160 (1), pp.0. 10.3847/1538-3881/ab9301. hal-02886110 HAL Id: hal-02886110 https://hal.archives-ouvertes.fr/hal-02886110 Submitted on 1 Jul 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Open Archive Toulouse Archive Ouverte OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible This is a publisher’s version published in: https://oatao.univ-toulouse.fr/26226 Official URL : https://doi.org/10.3847/1538-3881/ab9301 To cite this version: Guilloteau, Claire and Oberlin, Thomas and Berné, Olivier and Habart, Émilie and Dobigeon, Nicolas Simulated JWST data sets for multispectral and hyperspectral image fusion. (2020) The Astronomical Journal, 160 (1). ISSN 0004-6256. Any correspondence concerning this service should be sent to the repository administrator: [email protected] The Astronomical Journal, 160:28 (13pp), 2020 July https://doi.org/10.3847/1538-3881/ab9301 © 2020. -
Selection of Spitzer Young Stellar Object Candidates Using Deep Learning Classifiers
Selection of Spitzer Young Stellar Object candidates using Deep Learning classifiers David Cornu and Julien Montillaud linkedin page UTINAM, Univ. Bourgogne Franche-Comt´e, Besan¸con,France 1 - Introduction 3 - Deep Learning Observing Young Stellar Objects (YSOs) enables us to characterize the star forming regions, In our case, we rely on one of the most famous and widely used supervised-learning approach e.g. by their star formation efficiency and history or by their density distribution. They are : Artifical Neural Networks (ANN). The neurons in ANN are defined as a mathematical classified into evo lutionary stages (class 0, I, II) using their infrared (IR) Spectral Energy model performing weighted sums of an input vector (which represents different dimensions of Distribution (SED). The Spitzer telescope can be used for such classification using his the same object to classify). It then compares the result to a threshold activation function IRAC bands at 3.6, 4.5, 5.6, 8 µm and MIPS 24 µm, allowing us to distinguish IR excess in and changes the state of the neuron to 1 or 0 (firing or not). The learning process consist in class I or the disk emission of the class II from other kind of objects/contaminents. comparing the expected value (target) with the result obtained by the activation of the neuron, and then modify the weights according to the error gradient, hence learning anti/correlations. m XX h = Xi!i i=1 ( 1 if h > θ O = g(h) = 0 if h ≤ θ Performing complex classification requires more than one neuron. We can add them in one layer, fully connecting each neuron to all the inputs, and we can add multiple layers by making some neurons take the output of the previous layer as their own inputs. -
THE STAR FORMATION NEWSLETTER an Electronic Publication Dedicated to Early Stellar Evolution and Molecular Clouds
THE STAR FORMATION NEWSLETTER An electronic publication dedicated to early stellar evolution and molecular clouds No. 148 — 15 February 2005 Editor: Bo Reipurth ([email protected]) Abstracts of recently accepted papers The Brightest OH Maser in the Sky? A Flare of Emission in W75 N A. V. Alakoz1, V. I. Slysh1, M. V. Popov1, and I. E. Val’tts1 1 Astro Space Center of the Lebedev Physical Institute of RAS, Profsoyuznaya Str. 84/32, Moscow 117997, Russia E-mail contact: [email protected] A flare of maser radio emission in the OH-line 1665 MHz has been discovered in the star forming region W75 N in 2003, with the flux density about 1000 Jy. At the moment of observations this was the strongest OH maser detected during the whole history of studies since the discovery of cosmic masers in 1965. The flare emission is linearly polarized with a degree of polarization near 100%. A weaker flare with a flux of 145 Jy was observed in this source in 2000 – 2001, which was probably a precursor of the powerful flare. Intensity of two other spectral features has decreased after beginning of the flare. Such variation of the intensity of maser condensation emission (increasing of one and decreasing of other) can be explained by passing of the magneto hydrodynamic shock across the regions of the enhanced gas concentration. Accepted by Astronomy Letters astro-ph/0501539 (2005) Pushing the Envelope: The Impact of an Outflow at the Earliest Stages of Star Forma- tion H´ector G. Arce1 and Anneila I. -
Herschel Litho: Orion's Rainbow of Infrared Light
Orion’s Rainbow of Infrared Light www.nasa.gov Orion’s Rainbow of Infrared Light activity in protostars, Herschel’s Photodetector Array Camera and Spectrometer probed long infrared wavelengths of light that trace cold dust particles, while Spitzer gauged the warmer dust emitting shorter infrared wavelengths. In these data, as- tronomers noticed that several of the young stars varied in their brightness by more than 20 percent over just a few weeks. As this twinkling comes from cool material emitting infrared light, the material must be far from the hot center of the young star, likely in the outer disk or surrounding gas envelope. At that distance, it should take years or centuries for material to spiral closer in to the growing starlet, rather than mere weeks. A couple of scenarios under investigation could account for this short span. One possibility is that lumpy filaments of gas funnel from the outer to the central regions of the star, temporarily warming the object as the clumps hit its inner disk. Or, it could be that material occasionally piles up at the inner edge of the disk and casts a shadow on the outer disk. Herschel’s exquisite sensitivity opens up new possibilities for astronomers to study star formation and observe short-term variability in Orion protostars. Follow-up observations with Herschel will help astronomers identify the physical processes Astronomers have spotted young stars in the Orion Nebula responsible for the variability. changing right before their eyes, thanks to the European Space Herschel is a European Space Agency cornerstone mission, Agency’s Herschel Space Observatory and NASA’s Spitzer with science instruments provided by consortia of European Space Telescope.