2014A&A...566A...4L


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.04CEST21:49:02

2014A&A...566A...4L - Astronomy and Astrophysics, volume 566A, 4-4 (2014/6-1)

Three new X-ray emitting O-type subdwarf stars discovered with Chandra.

LA PALOMBARA N., ESPOSITO P., MEREGHETTI S. and TIENGO A.

Abstract (from CDS):

X-ray observations of sdO stars are a useful tool to investigate their properties, but so far only two sdO stars were detected at X-rays. We aimed to perform the first systematic search for X-ray emission from sdO stars to characterize the X-ray emission from single and binary sdO stars.We observed a complete flux-limited sample of 19 sdO stars with the Chandra HRC-I camera to measure the count rate of the detected sources or to set a tight upper limit on it for the undetected sources. We obtained a robust detection of BD+37°1977 and Feige 34 and a marginal detection of BD+28° 4211. The estimated luminosity of BD+37°1977 is above 1031 erg/s, which is high enough to suggest the possible presence of an accreting compact companion. This possibility is unlikely for all the other targets (both detected and undetected), since in their case LX≲1030erg/s. On the other hand, for all 19 targets the estimated value of LX (or its upper limit) implies an X-ray/bolometric flux ratio that agrees with log(LX/Lbol)=-6.7±0.5, which is the range of values typical of main-sequence and giant O stars. The observing campaign performed by Chandra has discovered three new X-ray emitting sdO stars; for one of them the observed X-ray flux might be emitted by an accreting compact companion, while for the other two stars it is most probably due to intrinsic emission. The same is possibile for the 16 undetected stars.

Abstract Copyright:

Journal keyword(s): subdwarfs - X-rays: stars - X-rays: binaries - stars: individual: BD+37 1977 - stars: individual: Feige 34 - stars: individual: BD+28 4211

Simbad objects: 21

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Number of rows : 21

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 BD+37 442 HS* 01 58 33.4340086125 +38 34 23.846108332   9.69 9.92     sdOHe 57 0
2 LS I +63 198 HS* 03 29 05.6682994636 +64 04 42.160486711 11.71 13.18 13.20 12.96 13.2 sdOB 15 0
3 LS V +22 38 HS* 06 16 13.3273979436 +22 45 48.782736570 11.69 11.5 10.9 10.45   sdO 20 0
4 HD 49798 HXB 06 48 04.7000758397 -44 18 58.432035331 6.758 8.017 8.287 8.391 8.543 sdO6 283 0
5 CPD-31 1701 HS* 07 36 30.1947256655 -32 12 43.685247834 9 10.26 10.48 10.81   sdO8p 59 0
6 BD-03 2179 HS* 08 02 14.8868948191 -03 58 16.342511529 8.8 10.044 10.29 10.64 10.60 sdO 37 0
7 BD+75 325 HS* 08 10 49.4901623070 +74 57 57.936226530 8.002 9.23 9.50 9.698 9.884 sdO5 232 0
8 CD-45 5058 HS* 09 20 10.1321975829 -45 31 54.939916304 9.81 11.03 11.33 11.62   sdO 47 0
9 BD+37 1977 HS* 09 24 26.3928822549 +36 42 53.293596680   9.86 10.15     sdO 39 0
10 BD+48 1777 HS* 09 30 46.7811418219 +48 16 23.765039283   10.41 10.70     sdO9: 26 0
11 Feige 34 HS* 10 39 36.7377085527 +43 06 09.209752646 9.613 10.91 11.14 11.319 11.464 sdOp 604 0
12 BD+18 2647 HS* 12 41 51.7901702595 +17 31 19.750592670 10.261 11.70 11.63 11.969 12.159 sdOpec 162 1
13 CD-46 8926 HS* 13 53 08.2145759352 -46 43 42.320124869   11.04 11.30     sdO 36 0
14 HD 127493 HS* 14 32 21.4928221685 -22 39 25.645935056 8.64 9.74 10.08     sdOHe 84 0
15 LS IV -12 1 HS* 16 23 43.9894821460 -12 12 33.641936636 10.06 11.14 11.17     sdO 30 0
16 BD+39 3226 HS* 17 46 31.9117461025 +39 19 09.070415423   9.89 10.18     sdOHe 31 0
17 CD-51 11879 HS* 19 02 11.7422717452 -51 30 09.556345077   11.44 11.55     sdO 33 0
18 CD-23 15853 HS* 19 55 38.2259646039 -23 13 42.230875825   11.39 11.64     sdO 20 0
19 LS IV +10 9 HS* 20 43 02.4779659976 +10 34 20.998642549 10.51 11.71 12.06     sdO 30 0
20 BD+28 4211 HS* 21 51 11.0220905905 +28 51 50.366090892 8.922 10.25 10.58 10.656 10.831 sdO2VIIIHe5 735 0
21 BD+25 4655 HS* 21 59 41.9751489837 +26 25 57.398356446 8.27 9.39 9.68     sdO6 99 0

    Equat.    Gal    SGal    Ecl

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2020.07.04-21:49:02

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