scholarly journals Evidence for magnetic activity at starbirth: a powerful X-ray flare from the Class 0 protostar HOPS 383

2020 ◽  
Vol 638 ◽  
pp. L4 ◽  
Author(s):  
Nicolas Grosso ◽  
Kenji Hamaguchi ◽  
David A. Principe ◽  
Joel H. Kastner
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Direct Proof ◽  
Magnetic Activity ◽  
Evolutionary Stage ◽  
X Rays ◽  
X Ray ◽  
Order Of Magnitude ◽  
Solar Type ◽  
Bona Fide

Context. Class 0 protostars represent the earliest evolutionary stage of solar-type stars, during which the majority of the system mass resides in an infalling envelope of gas and dust and is not yet in the central, nascent star. Although X-rays are a key signature of magnetic activity in more evolved protostars and young stars, whether such magnetic activity is present at the Class 0 stage is still debated. Aims. We aim to detect a bona fide Class 0 protostar in X-rays. Methods. We observed HOPS 383 in 2017 December in X-rays with the Chandra X-ray Observatory (∼84 ks) and in near-infrared imaging with the Southern Astrophysical Research telescope. Results. HOPS 383 was detected in X-rays during a powerful flare. This hard (E >  2 keV) X-ray counterpart was spatially coincident with the northwest 4 cm component of HOPS 383, which would be the base of the radio thermal jet launched by HOPS 383. The flare duration was ∼3.3 h; at the peak, the X-ray luminosity reached ∼4 × 1031 erg s−1 in the 2−8 keV energy band, a level at least an order of magnitude larger than that of the undetected quiescent emission from HOPS 383. The X-ray flare spectrum is highly absorbed (NH ∼ 7 × 1023 cm−2), and it displays a 6.4 keV emission line with an equivalent width of ∼1.1 keV, arising from neutral or low-ionization iron. Conclusions. The detection of a powerful X-ray flare from HOPS 383 constitutes direct proof that magnetic activity can be present at the earliest formative stages of solar-type stars.

scholarly journals Quest for the Upcoming Periastron Passage of an Episodic Dust Maker and Particle-accelerating Colliding-wind Binary: WR 125

2021 ◽  
Vol 162 (6) ◽  
pp. 257
Author(s):  
Bharti Arora ◽  
J. C. Pandey ◽  
Michaël De Becker ◽  
S. B. Pandey ◽  
Nand K. Chakradhari ◽  
...  
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Recurrence Time ◽  
Time Interval ◽  
Wide Field ◽  
X Rays ◽  
Optical Telescope ◽  
X Ray ◽  
Enhanced Absorption

Abstract We have carried out a long-term infrared and X-ray investigation of the colliding-wind binary WR 125 (WC7 + O9III). The source was monitored using AstroSat Soft X-ray Telescope and the Tata Institute of Fundamental Research Near Infrared Imaging Camera-II mounted at the back of 3.6 m Devasthal Optical Telescope. WR 125 appeared brighter in the near-infrared K-band during the years 2017–2021 which is attributed to another episode of dust formation similar to the one reported during the likely periastron passage at the beginning of the 1990s. This is further supported by enhanced emission observed in the W1 and W2 bands of Wide-field Infrared Survey Explorer from 2018–2019. By combining archival X-ray data sets with our new measurements, long-term variations have been noticed. The source reaches a lower emission state in 2020 June (close to the recent infrared maximum) which could be due to enhanced absorption of X-rays produced in the colliding-wind region by the WC stellar wind close to the periastron in an eccentric orbit. The time interval between the previous and latest X-ray low states may indicate an orbital period of 28–29 years, in fair agreement with the recurrence time of episodic dust production. We also discuss published radio measurements in the context of a common picture based on a long-period binary scenario. These results allow us to draw relevant guidelines for future multiwavelength observations of WR 125.

scholarly journals eROSITA - Nearby Young Stars in X-rays

2015 ◽  
Vol 10 (S314) ◽  
pp. 280-285
Author(s):  
J. Robrade
Keyword(s):  
Magnetic Activity ◽  
Young Stars ◽  
Stellar Systems ◽  
X Rays ◽  
X Ray ◽  
Sky Survey ◽  
Order Of Magnitude ◽  
Existing Data ◽  
Sensitivity Increase

AbstractX-ray surveys are well suited to detect, identify and study young stars based on their high levels of magnetic activity and thus X-ray brightness. The eROSITA instrument onboard the Spectrum-Roentgen-Gamma (SRG) satellite will perform an X-ray all-sky survey that surpasses existing data by a sensitivity increase of more than an order of magnitude. The 4 yr survey is expected to detect more than half a million stars and stellar systems in X-rays.

scholarly journals Updated X-ray view of the Hyades cluster

2020 ◽  
Vol 640 ◽  
pp. A66 ◽  
Author(s):  
S. Freund ◽  
J. Robrade ◽  
P. C. Schneider ◽  
J. H. M. M. Schmitt
Keyword(s):  
Main Sequence ◽  
Distribution Functions ◽  
X Rays ◽  
Stellar Rotation ◽  
Detection Rates ◽  
X Ray ◽  
Rotation Periods ◽  
Hyades Cluster ◽  
Bona Fide ◽  
Tidal Tails

Aims. We revisit the X-ray properties of the main sequence Hyades members and the relation between X-ray emission and stellar rotation. Methods. As an input catalog for Hyades members, we combined three recent Hyades membership lists derived from Gaia DR2 data that include the Hyades core and its tidal tails. We searched for X-ray detections of the main sequence Hyades members in the ROSAT all-sky survey, and pointings from ROSAT, the Chandra X-Ray Observatory, and XMM-Newton. Furthermore, we adopted rotation periods derived from Kepler’s K2 mission and other resources. Results. We find an X-ray detection for 281 of 1066 bona fide main sequence Hyades members and provide statistical upper limits for the undetected sources. The majority of the X-ray detected stars are located in the Hyades core because of its generally smaller distance to the Sun. F- and G-type stars have the highest detection fraction (72%), while K- and M-type dwarfs have lower detection rates (22%). The X-ray luminosities of the detected members range from ∼2 × 1027 erg s−1 for late M-type dwarfs to ∼2 × 1030 erg s−1 for active binaries. The X-ray luminosity distribution functions formally differ for the members in the core and tidal tails, which is likely caused by a larger fraction of field stars in our Hyades tails sample. Compared to previous studies, our sample is slightly fainter in X-rays due to differences in the Hyades membership list used; furthermore, we extend the X-ray luminosity distribution to fainter luminosities. The X-ray activity of F- and G-type stars is well defined at FX/Fbol ≈ 10−5. The fractional X-ray luminosity and its spread increases to later spectral types reaching the saturation limit (FX/Fbol ≈ 10−3) for members later than spectral type M3. Confirming previous results, the X-ray flux varies by less than a factor of three between epochs for the 104 Hyades members with multiple epoch data, significantly less than expected from solar-like activity cycles. Rotation periods are found for 204 Hyades members, with about half of them being detected in X-rays. The activity-rotation relation derived for the coeval Hyades members has properties very similar to those obtained by other authors investigating stars of different ages.

scholarly journals Megavoltage X-Ray Imaging Based on Cerenkov Effect: A New Application of Optical Fibres to Radiation Therapy

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
A. Teymurazyan ◽  
G. Pang
Keyword(s):  
Optical Fibres ◽  
X Rays ◽  
Modulation Transfer ◽  
Imaging Device ◽  
Active Matrix ◽  
X Ray ◽  
X Ray Imaging ◽  
Order Of Magnitude ◽  
Detection Quantum Efficiency ◽  
Cerenkov Effect

A Monte Carlo simulation was used to study imaging and dosimetric characteristics of a novel design of megavoltage (MV) X-ray detectors for radiotherapy applications. The new design uses Cerenkov effect to convert X-ray energy absorbed in optical fibres into light for MV X-ray imaging. The proposed detector consists of a matrix of optical fibres aligned with the incident X rays and coupled to an active matrix flat-panel imager (AMFPI) for image readout. Properties, such as modulation transfer function, detection quantum efficiency (DQE), and energy response of the detector, were investigated. It has been shown that the proposed detector can have a zero-frequency DQE more than an order of magnitude higher than that of current electronic portal imaging device (EPID) systems and yet a spatial resolution comparable to that of video-based EPIDs. The proposed detector is also less sensitive to scattered X rays from patients than current EPIDs.

scholarly journals Discovery and follow-up of ASASSN-19dj: an X-ray and UV luminous TDE in an extreme post-starburst galaxy

2020 ◽  
Vol 500 (2) ◽  
pp. 1673-1696 ◽  
Author(s):  
Jason T Hinkle ◽  
T W-S Holoien ◽  
K Auchettl ◽  
B J Shappee ◽  
J M M Neustadt ◽  
...  
Keyword(s):  
Optical Emission ◽  
Starburst Galaxy ◽  
Late Time ◽  
X Rays ◽  
Tidal Disruption ◽  
X Ray ◽  
Bolometric Luminosity ◽  
Order Of Magnitude ◽  
High Cadence

ABSTRACT We present observations of ASASSN-19dj, a nearby tidal disruption event (TDE) discovered in the post-starburst galaxy KUG 0810+227 by the All-Sky Automated Survey for Supernovae (ASAS-SN) at a distance of d ≃ 98 Mpc. We observed ASASSN-19dj from −21 to 392 d relative to peak ultraviolet (UV)/optical emission using high-cadence, multiwavelength spectroscopy and photometry. From the ASAS-SN g-band data, we determine that the TDE began to brighten on 2019 February 6.8 and for the first 16 d the rise was consistent with a flux ∝t2 power law. ASASSN-19dj peaked in the UV/optical on 2019 March 6.5 (MJD = 58548.5) at a bolometric luminosity of L = (6.2 ± 0.2) × 1044 erg s−1. Initially remaining roughly constant in X-rays and slowly fading in the UV/optical, the X-ray flux increased by over an order of magnitude ∼225 d after peak, resulting from the expansion of the X-ray emitting region. The late-time X-ray emission is well fitted by a blackbody with an effective radius of ∼1 × 1012 cm and a temperature of ∼6 × 105 K. The X-ray hardness ratio becomes softer after brightening and then returns to a harder state as the X-rays fade. Analysis of Catalina Real-Time Transient Survey images reveals a nuclear outburst roughly 14.5 yr earlier with a smooth decline and a luminosity of LV ≥ 1.4 × 1043 erg s−1, although the nature of the flare is unknown. ASASSN-19dj occurred in the most extreme post-starburst galaxy yet to host a TDE, with Lick HδA = 7.67 ± 0.17 Å.

scholarly journals The deep Chandra survey in the SDSS J1030+0524 field

2020 ◽  
Vol 637 ◽  
pp. A52 ◽  
Author(s):  
R. Nanni ◽  
R. Gilli ◽  
C. Vignali ◽  
M. Mignoli ◽  
A. Peca ◽  
...  
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Cumulative Number ◽  
Imaging Data ◽  
X Ray ◽  
Large Scale Structures ◽  
Multi Wavelength ◽  
Deep Fields ◽  
Initial Source

We present the X-ray source catalog for the ∼479 ks Chandra exposure of the SDSS J1030+0524 field, which is centered on a region that shows the best evidence to date of an overdensity around a z > 6 quasar, and also includes a galaxy overdensity around a Compton-thick Fanaroff-Riley type II (FRII) radio galaxy at z = 1.7. Using wavdetect for initial source detection and ACIS Extract for source photometry and significance assessment, we create preliminary catalogs of sources that are detected in the full (0.5−7.0 keV), soft (0.5−2.0 keV), and hard (2−7 keV) bands, respectively. We produce X-ray simulations that mirror our Chandra observation to filter our preliminary catalogs and achieve a completeness level of > 91% and a reliability level of ∼95% in each band. The catalogs in the three bands are then matched into a final main catalog of 256 unique sources. Among them, 244, 193, and 208 are detected in the full, soft, and hard bands, respectively. The Chandra observation covers a total area of 335 arcmin2 and reaches flux limits over the central few square arcmins of ∼3 × 10−16, 6 × 10−17, and 2 × 10−16 erg cm−2 s−1 in the full, soft, and hard bands, respectively This makes J1030 field the fifth deepest extragalactic X-ray survey to date. The field is part of the Multiwavelength Survey by Yale-Chile (MUSYC), and is also covered by optical imaging data from the Large Binocular Camera (LBC) at the Large Binocular Telescope (LBT), near-infrared imaging data from the Canada France Hawaii Telescope WIRCam (CFHT/WIRCam), and Spitzer IRAC. Thanks to its dense multi-wavelength coverage, J1030 represents a legacy field for the study of large-scale structures around distant accreting supermassive black holes. Using a likelihood ratio analysis, we associate multi-band (r, z, J, and 4.5 μm) counterparts for 252 (98.4%) of the 256 Chandra sources, with an estimated reliability of 95%. Finally, we compute the cumulative number of sources in each X-ray band, finding that they are in general agreement with the results from the Chandra Deep Fields.

Hyperspectral Cathodoluminescence Imaging and Analysis Extending from Ultraviolet to Near Infrared

2012 ◽  
Vol 18 (6) ◽  
pp. 1239-1245 ◽  
Author(s):  
C.M. MacRae ◽  
N.C. Wilson ◽  
A. Torpy ◽  
C.J. Davidson
Keyword(s):  
Rare Earth ◽  
Near Infrared ◽  
Preliminary Investigation ◽  
X Rays ◽  
Spectral Mapping ◽  
X Ray ◽  
Quantitative Electron Probe Microanalysis ◽  
Uv Visible ◽  
Intense Emission ◽  
Cathodoluminescence Imaging

AbstractThe measurement of near-infrared (NIR) cathodoluminescence (CL) with sufficient sensitivity to allow full spectral mapping has been investigated through the application of optimized grating spectrometers that allow the ultraviolet (UV), visible, and NIR CL spectra to be measured simultaneously. Two optical spectrometers have been integrated into an electron microprobe, allowing simultaneous collection of hyperspectral CL (UV-NIR), characteristic X-rays, and electron signals. Combined hyperspectral CL spectra collected from two natural apatite (Ca5[PO4]3[OH,F]) samples from Wilberforce (Ontario, Canada) and Durango (Mexico) were qualitatively analyzed to identify the emission centers and then deconvoluted pixel-by-pixel using least-squares fitting to produce a series of ion-resolved CL intensity maps. Preliminary investigation of apatite has shown strong NIR emissions associated primarily with the rare-earth element Nd. Details of growth and alteration were revealed in the NIR that were not discernable with electron-induced X-ray mapping. Intense emission centers from Nd3+ and Sm3+ were observed in the spectra from both apatites, along with minor emissions from other 3+ rare-earth elements. Quantitative electron probe microanalysis was performed on points within the mapped area of the Durango apatite to produce a calibration line relating cathodoluminescent intensity of the fitted peak centered at 1,073 nm (1.156 eV) to the Nd concentration.

X-rays from superbubbles in the Large Magellanic Cloud

1991 ◽  
Vol 148 ◽  
pp. 99-100
Author(s):  
You-Hua Chu ◽  
Mordecai-Mark Mac Low
Keyword(s):  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Shell Structures ◽  
X Rays ◽  
Simple Ring ◽  
X Ray ◽  
Order Of Magnitude

We find diffuse X-ray emission not associated with known SNRs in seven LMC HII complexes. All, except 30 Dor, have simple ring morphologies, indicating shell structures. Assuming these are superbubbles, we find the X-ray luminosity expected from their hot interiors to be an order of magnitude lower than the observed value. SNRs close to the center of a superbubble add very little emission, but we calculate that off-center SNRs hitting the ionized shell could explain the observed emission.

scholarly journals X-rays from magnetic massive OB stars

2013 ◽  
Vol 9 (S302) ◽  
pp. 330-333
Author(s):  
V. Petit ◽  
D. H. Cohen ◽  
Y. Nazé ◽  
M. Gagné ◽  
R. H. D. Townsend ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Massive Stars ◽  
Magnetic Activity ◽  
Magnetic Characteristics ◽  
Driving Mechanism ◽  
X Rays ◽  
X Ray ◽  
Ob Stars ◽  
Strong Winds

AbstractThe magnetic activity of solar-type and low-mass stars is a well known source of coronal X-ray emission. At the other end of the main sequence, X-rays emission is instead associated with the powerful, radiatively driven winds of massive stars. Indeed, the intrinsically unstable line-driving mechanism of OB star winds gives rise to shock-heated, soft emission (~0.5 keV) distributed throughout the wind. Recently, the latest generation of spectropolarimetric instrumentation has uncovered a population of massive OB-stars hosting strong, organized magnetic fields. The magnetic characteristics of these stars are similar to the apparently fossil magnetic fields of the chemically peculiar ApBp stars. Magnetic channeling of these OB stars' strong winds leads to the formation of large-scale shock-heated magnetospheres, which can modify UV resonance lines, create complex distributions of cooled Halpha emitting material, and radiate hard (~2-5 keV) X-rays. This presentation summarizes our coordinated observational and modelling efforts to characterize the manifestation of these magnetospheres in the X-ray domain, providing an important contrast between the emission originating in shocks associated with the large-scale fossil fields of massive stars, and the X-rays associated with the activity of complex, dynamo-generated fields in lower-mass stars.

scholarly journals X-ray emission fromHerbig stars

2021 ◽  
Author(s):  
E. B. Ryspaeva ◽  
Keyword(s):  
Magnetic Activity ◽  
X Rays ◽  
Space Observatory ◽  
Thermal Component ◽  
Radiation Characteristics ◽  
X Ray ◽  
Close Relationship

The archived X-ray observations of 9 Ae/Be Herbig stars obtained on the XMM-Newton space observatory are analysed for checking the hypotheses of their X-rays formation. An analysis of the dependences of the X-ray radiation characteristics for Herbig stars on the parameters of the stars revealed a close relationship between the magnetic activity and the processes of generation of X-ray radiation from Herbig stars, as well as the possible presence of a non-thermal component of the X-ray spectra.

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