scholarly journals A census of young stellar population associated with the Herbig Be star HD 200775

2020 ◽  
Vol 494 (4) ◽  
pp. 5851-5871
Author(s):  
Piyali Saha ◽  
Maheswar Gopinathan ◽  
Umanath Kamath ◽  
Chang Won Lee ◽  
Manoj Puravankara ◽  
...  
Keyword(s):  
Proper Motion ◽  
Column Density ◽  
Stellar Population ◽  
Dark Cloud ◽  
Infrared Excess ◽  
X Ray ◽  
Density Peaks ◽  
Be Star ◽  
Cloud Complex ◽  
Gaia Dr2

ABSTRACT The region surrounding the well-known reflection nebula, NGC 7023, illuminated by a Herbig Be star, HD 200775, located in the dark cloud L1174 is studied in this work. Based on the distances and proper motion values from Gaia DR2 of 20 previously known young stellar object (YSO) candidates, we obtained a distance of 335 ± 11 pc to the cloud complex L1172/1174. Using polarization measurements of the stars projected on the cloud complex, we show additional evidence for the cloud to be at ∼335 pc distance. Using this distance and proper motion values of the YSO candidates, we searched for additional comoving sources in the vicinity of HD 200775 and found 20 new sources, which show low infrared excess emission and are of age ∼1 Myr. Among these, 10 YSO candidates and 4 newly identified comoving sources are found to show X-ray emission. Three of the four new sources for which we have obtained optical spectra show H α in emission. About 80 per cent of the total sources are found within ∼1 pc distance from HD 200775. Spatial correlation of some of the YSO candidates with the Herschel dust column density peaks suggests that star formation is still active in the region and may have been triggered by HD 200775.

A study of the stellar population in the LYNDS 1641 dark cloud. IV - The Einstein X-ray sources

1990 ◽  
Vol 362 ◽  
pp. 168 ◽  
Author(s):  
Karen M. Strom ◽  
Stephen E. Strom ◽  
Francis P. Wilkin ◽  
Luis Carrasco ◽  
Irene Cruz-Gonzalez ◽  
...  
Keyword(s):  
Stellar Population ◽  
Dark Cloud ◽  
X Ray

scholarly journals Infrared Emission from Four be Stars Optical Counterparts of Galactic X-Ray Sources

1982 ◽  
Vol 98 ◽  
pp. 247-251
Author(s):  
P. Persi ◽  
M. Ferrari-Toniolo ◽  
G.L. Grasdalen
Keyword(s):  
Energy Distribution ◽  
Electron Density ◽  
Stellar Wind ◽  
Infrared Emission ◽  
Circumstellar Disk ◽  
Be Stars ◽  
Infrared Excess ◽  
Infrared Observations ◽  
X Ray ◽  
Be Star

Preliminary results of our infrared observations from 2.3 up to 10 and 20 microns of the Be-X-ray stars X Per, γ Cas and HDE 245770, indicate the presence of an ionized circumstellar disk with an electron density law of the type ne ∝ r−3.5. x Per and γ Cas show besides, variable infrared excess at 10μ suggesting variability in the stellar wind. LS I+65°010 presents an anomalous infrared energy distribution for a Be star.

scholarly journals Multiwavelength observations of the Be-star/X-ray binary EXO2030+375 during outburst

1994 ◽  
Vol 162 ◽  
pp. 206-207
Author(s):  
A.J. Norton ◽  
M.J. Coe ◽  
C. Everall ◽  
P. Roche ◽  
L. Bildsten ◽  
...  
Keyword(s):  
Neutron Star ◽  
Emission Lines ◽  
Be Stars ◽  
Infrared Excess ◽  
X Ray ◽  
Circumstellar Material ◽  
Spin Period ◽  
Be Star ◽  
Star Surface ◽  
X Ray Binaries

EXO2030+375 consists of a neutron star in an eccentric 46 day orbit around a 20th magnitude Be-star companion (Coe et al., 1988; Parmar et al., 1989; Stollberg et al., 1993). The Be-star is thought to be surrounded by a shell/disc of material which is responsible for the infrared excess and Balmer emission lines which are characteristic of Be-stars in general. At periastron, the neutron star passes through this circumstellar material, giving rise to enhanced accretion onto the neutron star surface. As a result of this, the X-ray emission (pulsed at the neutron star spin period of 41.8s) increases dramatically, so producing the transient, outburst behaviour which is commonly seen in Be-star / X-ray binaries.

scholarly journals CO Column Density and Extinction in the Chamaeleon II–III Dark-Cloud Complex

2001 ◽  
Vol 53 (6) ◽  
pp. 1109-1118 ◽  
Author(s):  
Takahiro Hayakawa ◽  
Laurent Cambrésy ◽  
Toshikazu Onishi ◽  
Akira Mizuno ◽  
Yasuo Fukui
Keyword(s):  
Column Density ◽  
Dark Cloud ◽  
Cloud Complex

scholarly journals Swift J004427.3−734801 – a probable Be/white dwarf system in the Small Magellanic Cloud

2020 ◽  
Vol 497 (1) ◽  
pp. L50-L55 ◽  
Author(s):  
M J Coe ◽  
J A Kennea ◽  
P A Evans ◽  
A Udalski
Keyword(s):  
Gravitational Lensing ◽  
White Dwarf ◽  
Magellanic Cloud ◽  
Optical Monitoring ◽  
Small Magellanic Cloud ◽  
Optical Counterpart ◽  
Infrared Excess ◽  
X Ray ◽  
Be Star ◽  
Soft Spectrum

ABSTRACT Swift J004427.3−734801 is an X-ray source in the Small Magellanic Cloud (SMC) that was first discovered as part of the Swift S-CUBED programme in 2020 January. It was not detected in any of the previous 3 yr worth of observations. The accurate positional determination from the X-ray data has permitted an optical counterpart to be identified that has the characteristics of an O9V−B2III star. Evidence for the presence of an infrared excess and significant I-band variability strongly suggests that this is an OBe-type star. Over 17 yr worth of optical monitoring by the OGLE (Optical Gravitational Lensing Experiment) project reveals periods of time in which quasi-periodic optical flares occur at intervals of ∼21.5 d. The X-ray data obtained from the S-CUBED project reveal a very soft spectrum, too soft to be that from accretion on to a neutron star or black hole. It is suggested here that this is a rarely identified Be star–white dwarf binary in the SMC.

ROSAT X-Ray Study of the Chamaeleon I Dark Cloud. I. The Stellar Population

1993 ◽  
Vol 416 ◽  
pp. 623 ◽  
Author(s):  
Eric D. Feigelson ◽  
Sophie Casanova ◽  
Thierry Montmerle ◽  
Jean Guibert
Keyword(s):  
Stellar Population ◽  
Dark Cloud ◽  
X Ray

scholarly journals Constraining the distance to the North Polar Spur with Gaia DR2

2020 ◽  
Vol 498 (4) ◽  
pp. 5863-5872
Author(s):  
Kaustav K Das ◽  
Catherine Zucker ◽  
Joshua S Speagle ◽  
Alyssa Goodman ◽  
Gregory M Green ◽  
...  
Keyword(s):  
Column Density ◽  
Near Infrared ◽  
Galactic Centre ◽  
X Rays ◽  
X Ray ◽  
The North ◽  
North Polar ◽  
X Ray Absorption ◽  
Gaia Dr2 ◽  
Total Column

ABSTRACT The North Polar Spur (NPS) is one of the largest structures observed in the Milky Way in both the radio and soft X-rays. While several predictions have been made regarding the origin of the NPS, modelling the structure is difficult without precise distance constraints. In this paper, we determine accurate distances to the southern terminus of the NPS and towards latitudes ranging up to 55°. First, we fit for the distance and extinction to stars towards the NPS using optical and near-infrared photometry and Gaia Data Release 2 astrometry. We model these per-star distance–extinction estimates as being caused by dust screens at unknown distances, which we fit for using a nested sampling algorithm. We then compare the extinction to the Spur derived from our 3D dust modelling with integrated independent measures from XMM–Newton X-ray absorption and H i column density measures. We find that we can account for nearly 100 per cent of the total column density of the NPS as lying within 140 pc for latitudes >26° and within 700 pc for latitudes <11°. Based on the results, we conclude that the NPS is not associated with the Galactic Centre or the Fermi bubbles. Instead, it is likely associated, especially at higher latitudes, with the Scorpius–Centaurus association.

scholarly journals The frequency of Kozai–Lidov disc oscillation driven giant outbursts in Be/X-ray binaries

2019 ◽  
Vol 489 (2) ◽  
pp. 1797-1804 ◽  
Author(s):  
Rebecca G Martin ◽  
Alessia Franchini
Keyword(s):  
Orbital Period ◽  
Time Scale ◽  
Orbital Plane ◽  
Material Flows ◽  
X Ray ◽  
System Parameters ◽  
Be Star ◽  
Chaotic Nature ◽  
X Ray Binaries ◽  
Good Agreement

ABSTRACT Giant outbursts of Be/X-ray binaries may occur when a Be-star disc undergoes strong eccentricity growth due to the Kozai–Lidov (KL) mechanism. The KL effect acts on a disc that is highly inclined to the binary orbital plane provided that the disc aspect ratio is sufficiently small. The eccentric disc overflows its Roche lobe and material flows from the Be star disc over to the companion neutron star causing X-ray activity. With N-body simulations and steady state decretion disc models we explore system parameters for which a disc in the Be/X-ray binary 4U 0115+634 is KL unstable and the resulting time-scale for the oscillations. We find good agreement between predictions of the model and the observed giant outburst time-scale provided that the disc is not completely destroyed by the outburst. This allows the outer disc to be replenished between outbursts and a sufficiently short KL oscillation time-scale. An initially eccentric disc has a shorter KL oscillation time-scale compared to an initially circular orbit disc. We suggest that the chaotic nature of the outbursts is caused by the sensitivity of the mechanism to the distribution of material within the disc. The outbursts continue provided that the Be star supplies material that is sufficiently misaligned to the binary orbital plane. We generalize our results to Be/X-ray binaries with varying orbital period and find that if the Be star disc is flared, it is more likely to be unstable to KL oscillations in a smaller orbital period binary, in agreement with observations.

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