首页     开始     To Survive in the Universe    
Inhabited Sky
    News@Sky     天文图片     收集     论坛     Blog New!     常见问题     新闻     登录  

HD 68164


目录

图像

上传图像

DSS Images   Other Images


相关文章

Distances and Metallicities of High- and Intermediate-Velocity Clouds
A table is presented that summarizes published absorption linemeasurements for the high- and intermediate-velocity clouds (HVCs andIVCs). New values are derived for N(H I) in the direction of observedprobes, in order to arrive at reliable abundances and abundance limits(the H I data are described in Paper II). Distances to stellar probesare revisited and calculated consistently, in order to derive distancebrackets or limits for many of the clouds, taking care to properlyinterpret nondetections. The main conclusions are the following. (1)Absolute abundances have been measured using lines of S II, N I, and OI, with the following resulting values: ~0.1 solar for one HVC (complexC), ~0.3 solar for the Magellanic Stream, ~0.5 solar for a southern IVC,and ~solar for two northern IVCs (the IV Arch and LLIV Arch). Finally,approximate values in the range 0.5-2 solar are found for three moreIVCs. (2) Depletion patterns in IVCs are like those in warm disk or halogas. (3) Most distance limits are based on strong UV lines of C II, SiII, and Mg II, a few on Ca II. Distance limits for major HVCs aregreater than 5 kpc, while distance brackets for several IVCs are in therange 0.5-2 kpc. (4) Mass limits for major IVCs are0.5-8×105 Msolar, but for major HVCs theyare more than 106 Msolar. (5) The Ca II/H I ratiovaries by up to a factor 2-5 within a single cloud, somewhat morebetween clouds. (6) The Na I/H I ratio varies by a factor of more than10 within a cloud, and even more between clouds. Thus, Ca II can beuseful for determining both lower and upper distance limits, but Na Ionly yields upper limits.

The distance to the Chain A high-velocity cloud complex.
We present high-resolution (R~5km/s) NaI and CaII interstellarabsorption line spectra observed toward five B stars in the line ofsight to the high-velocity cloud complex Chain A. We have failed todetect the presence of any high-velocity (V<-100km/s) interstellarabsorption toward these stars. This null detection enables us to place anew lower limit on the distance to the Chain A complex ofz>=837+/-200pc, assuming normal gas-phase abundances of NaI and CaII.If this distance determination is typical for other high-velocityclouds, it poses problems for theories that currently argue these cloudsinteract with the galactic disk.

An Einstein Observatory SAO-based catalog of B-type stars
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.

Photometrie de la comete Arend-Roland.
Not Available

提交文章


相关链接

  • - 没有找到链接 -
提交链接


下列团体成员


观测天体数据

星座:大熊座
右阿森松:08h14m47.05s
赤纬:+62°02'11.9"
视星:8.715
距离:350.877 天文距离
右阿森松适当运动:0.3
赤纬适当运动:-1.1
B-T magnitude:8.964
V-T magnitude:8.736

目录:
适当名称   (Edit)
HD 1989HD 68164
TYCHO-2 2000TYC 4126-1668-1
USNO-A2.0USNO-A2 1500-05003215
HIPHIP 40390

→ 要求更多目录从vizier