摘要:

Maps of the ‘‘Monogem Ring,’’ also known as the Gemini‐Monoceros X‐ray enhancement, in the R1 (110–284 eV), R2 (140–284 eV), and R4+R5 (500–1100 eV) bands from theROSATAll‐Sky Survey have been generated. The Monogem Ring has a fragmented, shell‐like structure in the R1 and R2 bands and extends across the galactic plane with little or no absorption; only part of the ring is visible in the R4+R5 band. There are intrinsic spectral variations within the ring, most notably from the low longitude side to the high longitude side, which would be consistent with a temperature increase from log (T/K)=5.95 to log (T/K)=6.34, assuming a Raymond & Smith (1977) equilibrium model with normal abundances and a constant neutral hydrogen column density (NH) of 5.0×1019cm−2.The Monogem Ring is modeled as a supernova remnant (SNR) in the adiabatic stage at various distances between 100 and 1300 pc. If the distance to the ring is 300 pc and the average temperature is log (T/K)=6.15, the initial ambient density is 5.2×10−3cm−3, the initial explosion energy is 1.9×1050ergs, the luminosity in the 100–1000 eV band is 6.1×1034ergs s−1, and the age is ∼86,000 yrs. The thermal pressure of the X‐ray emitting gas is 4.5×104K cm−3, which is only 2–4 times higher than the pressure of the undisturbed interstellar medium (ISM). © 1994American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.46700

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Stellar clusters and star‐forming regions provide excellent laboratories for stellar astronomers since they consist of coeval populations of stars of varied mass but fixed distance, chemical composition and age. By comparing clusters of different ages, the evolution of a variety of stellar properties that can serve as diagnostics of the unseen physics controlling the interior evolution of stars can be determined.ROSAT PSPC and HRI observations of more than a dozen star‐forming regions and stellar clusters, ranging in age from ∼106yrs to ∼700×106yrs, have provided an enormous amount of data with which questions left unanswered byEinsteinobservations can be addressed. The results from theseROSATobservations, as they pertain to the issues of stellar populations in star‐forming regions, luminosity functions in stellar clusters, relations between coronal activity and stellar rotation, and temporal and spectral analyses, are presented. © 1994American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.46667

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The ROSAT PSPC has proven to be an excellent instrument for detecting soft X‐ray shadows cast by interstellar clouds. We have conducted a program of shadowing observations aimed at improving our understanding of the soft X‐ray diffuse background and the hot phase of the ISM. In this program, dense interstellar clouds are used to place limits on the distance to the emission sources of the soft X‐ray background by measuring the depths of the absorption shadows cast by these clouds. We will present some of the results obtained to date in this program, focussing particularly on shadows of low latitude clouds and what they tell us about the Local Bubble and the origin of 3/4 keV galactic emission. © 1994American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.46706

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

I will present selected highlights from ROSAT observations of stellar X‐ray emission. Specifically I will discuss the dearth of X‐ray emission among white dwarfs and new evidence for the occurrence of X‐ray emitting shocks in the winds of early‐type stars. Last I will focus on ROSAT observations of the eclipsing cool star binary systems AR Lac, Algol, YY Gem and &agr; CrB and the resulting implications for coronal structure on these stars. © 1994American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.46719

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Gamma Draconis is the first, normal, single late K giant located on the red side of the coronal ‘‘dividing line’’ known to show conclusive evidence for hot (∼105K) transition region (TR) and coronal plasma. We present ROSAT PSPC data and HST GHRS spectra of &ggr; Dra and describe the coronal and TR properties of this K5 III star. The high temperature emissions of &ggr; Dra are compared to those of a sample of hybrid‐chromosphere bright giants and supergiants. New PSPC detections of the K3 giant &agr; Hya and the G supergiant &bgr; Aqr are presented. Upper limits are found for the hybrid‐chromosphere stars &thgr; Her and &agr; Aqr. These new measurements extend the X‐ray to C IV flux‐flux relations to significantly lower activity levels.

ISSN:0094-243X    

DOI:10.1063/1.46691

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The soft X‐ray response (below ∼0.5 keV), spectral resolution, and imaging capabilities ofROSATmake it an ideal observatory for studying the high energy emission from isolated radio pulsars. Some of the results from the first three years of theROSATmission pertaining to this interesting class of neutron stars are summarized. The class is presented according to their dynamical age (&tgr;∼P/2P˙) which, by no accident, is also a presentation according to rotational energy loss rate. The implicatins for the thermal evolution of neutron stars wil be highlighted. © 1994American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.46658

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

By applying a new method of source detection to the IPC data from theEinsteinSatellite, we have obtained a list of 1900 X‐ray targets at the declination range visible from the Arecibo Observatory. Over two‐thirds of those have been observed in a search for radio pulsars that might be associated with X‐ray emission. We report the discovery of three new radio pulsars near X‐ray targets. One is a young anti‐center pulsar PSR J0631+10) with a shallow spectrum and spindown age of 43 kyr. The other two, (PSR J1843+20 and J1908+04B, are slower pulsars with spin periods of 3.4 s and 0.84 s respectively. Both pulsars are at most 3′ away from their X‐ray counterparts, but the large positional uncertainties cannot yet rule out an association. PSR J1908+04B was found in the same 430 MHz beam of a previously known pulsar, B1905+04, which indicates that many pulsars may have gone undetected by previous searches. In a separate project, we have searched for radio pulsars inside the error boxes of unidentified &ggr;‐ray sources found by the EGRET detector aboard the GRO Observatory. Seven gamma‐ray error boxes were covered with 430 MHz beam areas. The search has produced a new 3.5 millisecond pulsar towards the galactic anti‐center. This pulsar is in a binary orbit with a period of only 6.3 hours. Preliminary results favor a low‐mass companion. Investigation of the possible association of the pulsar and gamma‐ray source as well as the existence of x‐ray emission will have to await further measurements. © 1994American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.46664

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The reports of periodic X‐ray emission from the Seyfert galaxy NGC 6814 have motivated a number of exotic models for the active nucleus. We took advantage of the superior sensitivity and the wide field of view of the Position‐Sensitive Proportional Counter on‐board the ROSAT satellite to show that while the nucleus of NGC 6814 is indeed an X‐ray emitter, the periodicity is due to another source, most likely a Galactic cataclysmic variable, ∼37 arc min away. © 1994American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.46743

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Recent ROSAT results on magnetic CV systems are reviewed with emphasis on the properties of the new sample of polars discovered from the ROSAT surveys. © 1994American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.46665

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Using the example of a still unidentified ‘‘serendiptious’’ X‐ray source in the field of the nearby galaxy NGC 1313, we describe a procedure for determining if unidentified x‐ray sources are likely compact objects. The very high X‐ray to optical flux ratio and other unusual properties of the X‐ray source MS 0317.7–6647 eliminate all the usual classes of optical counterparts except for either a very massive X‐ray binary (and Black Hole candidate) in NGC 1313 or a very nearby (∼100 pc) isolated neutron star slowly accreting interstellar matter. The presence of an IR cirrus cloud which shadows the 1/4 keV X‐ray background in this field supports the latter possibility. © 1994American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.46666

出版商:AIP    

年代:1994

数据来源: AIP