2008A&A...483..801A


Query : 2008A&A...483..801A

2008A&A...483..801A - Astronomy and Astrophysics, volume 483, 801-813 (2008/6-1)

The stellar population of the Rosat North Ecliptic Pole survey. II. Spectral analysis.

AFFER L., MICELA G. and MOREL T.

Abstract (from CDS):

X-ray surveys allow to identify young, main-sequence stars in the solar neighborhood. Young, stellar samples, selected according to their activity, can be used to determine the stellar birthrate in the last billion years. The ROSAT North Ecliptic Pole survey (NEP), with its moderately deep sensitivity (fluxes ≃10–14erg/cm2/s), is the best survey, to date, able to sample the intermediate-age (108-109years) nearby population. The identification process of NEP X-ray sources resulted in 144 X-ray sources having a normal stellar counterpart, with an excess of yellow stars with respect to model predictions. We want to determine if these X-ray active stars are young or intermediate-age stars, or active binaries. We acquired high-resolution, high signal-to-noise ratio optical spectra, to determine the age and physical properties of the NEP X-ray-detected stellar sources. We measure the (i) lithium abundance using the LiI 6707.8Å line, which is an excellent, youth indicator for our age range of interest; (ii) rotational and radial velocities (through cross-correlation methods); and (iii) chromospheric emission (from Hα and NaI D1 and D2 lines). The radial velocities distribution is consistent with that of a young field star population of age 4x109yrs, or younger. Rotational velocity measurements imply that our sample is dominated by relatively young or intermediate-age stars, as confirmed by our lithium measurements. Most of the detected stars probably belong to a young or intermediate-age population. Our measurements suggest that a burst in the stellar birthrate of a factor of four occurred in the last 108-years. We cannot, however, exclude the possibility that a small fraction of sources, amongst the fastest of the K-rotators, are old binary systems with tidally-locked rotation.

Abstract Copyright:

Journal keyword(s): stars: rotation - stars: abundances - techniques: spectroscopic - techniques: radial velocities - Galaxy: solar neighbourhood

Simbad objects: 61

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Number of rows : 61
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 Cl Melotte 22 OpC 03 46 24 +24 06.8           ~ 3282 0
2 Cl Melotte 25 OpC 04 29 47 +16 56.9           ~ 2929 0
3 TYC 4206-459-1 * 17 19 28.6932851496 +65 22 29.809483464   12.17 11.39 11.27   K0 6 0
4 BD+62 1542 ** 17 20 05.5423 +62 06 23.656   9.93 9.25     F8 11 0
5 TYC 4210-457-1 PM* 17 20 26.4803038080 +67 03 40.405507668   10.71 10.01     G8 2 0
6 HD 158063 * 17 21 10.4373888048 +69 48 02.547864000   7.99 7.38     F8 26 0
7 TYC 4202-210-1 * 17 21 42.6090028728 +62 00 32.866631388   12.21 11.57     K4 4 0
8 TYC 4421-511-1 * 17 24 00.4989289728 +69 40 29.865306972   12.49 12.49     G2IV 6 0
9 RX J1724.4+6412 EB* 17 24 26.9563565184 +64 12 23.878638864   11.02 10.47 10.059 9.728 G2 7 0
10 TYC 4206-1161-1 * 17 24 38.9759626512 +64 40 52.436049888   10.78 10.08     G7 5 0
11 TYC 4421-553-1 * 17 26 45.4393545096 +69 37 49.782762012   11.25 10.72     G2 3 0
12 HD 159539 * 17 29 39.4650315168 +68 47 39.608785032   9.58 9.14     G 4 0
13 TYC 4421-47-1 * 17 30 19.8865605096 +69 55 25.956355332   10.43 10.00     G0~ 7 0
14 HD 160198 PM* 17 33 18.0696418848 +67 12 13.389124932   8.08 7.65     F2 26 0
15 RX J1736.2+6502 PM* 17 36 14.5681460496 +65 02 28.757980932   11.79 10.75     K0 9 0
16 BD+68 946 PM* 17 36 25.8993094605 +68 20 20.909627174 11.73 10.65   8.3   M3.0V 277 0
17 BD+70 947 * 17 39 15.8082159600 +70 20 06.542779596   9.66 9.11     F8 4 0
18 V* MS Dra BY* 17 39 55.6940144688 +65 00 05.889381804   9.33 8.40     K0V 43 0
19 HD 161919 * 17 42 26.4395397336 +69 07 59.918735460   9.01 8.56     G0 4 0
20 BD+66 1042 * 17 43 01.8681590160 +66 06 42.727934520   10.30 9.66     F8V 5 0
21 TYC 4432-885-1 * 17 43 51.9921668208 +70 31 40.413553536   10.88 10.35     F3 2 0
22 RX J1744.0+7015 EB* 17 44 00.3335751504 +70 15 31.819143204   11.38 10.82 10.375 9.962 K0 6 0
23 HD 162898 PM* 17 49 03.8676228216 +62 47 55.779342504 7.030 7.060 6.690     F2 26 0
24 V* ET Dra Ro* 17 50 25.1179947720 +70 45 36.437554548   10.71 9.67     K2.5 43 1
25 BD+67 1039B * 17 52 43.9790711136 +67 00 29.556081828   10.89 10.48     F5VmA7 6 0
26 HD 163788 * 17 52 56.0356983936 +66 25 08.666981328   8.60 7.67     K0 16 0
27 HD 164781 PM* 17 57 03.6418628160 +68 49 19.656165468   9.74 9.01     G8V 8 0
28 BD+64 1235 * 17 58 01.4624535552 +64 09 34.579926108   11.07 10.11     G 4 0
29 TYC 4212-61-1 * 17 58 28.3025243904 +67 26 08.760650856   11.19 10.53     G2 3 0
30 HD 164873 * 17 58 47.7268066056 +63 50 37.806773064   8.66 8.49     A2 4 0
31 HD 164984 * 17 59 13.7339322528 +64 08 33.277846884   7.68 7.26     F2 25 0
32 TYC 4212-1074-1 * 17 59 23.0188229688 +66 02 56.285914236   11.46 10.29     K0III 14 0
33 NAME NEP reg 18 00 00.000 +66 33 38.55           ~ 319 0
34 TYC 4213-617-1 * 18 00 02.1412105656 +66 45 54.994939848   11.28 10.68     F8 7 0
35 V* EF Dra EB* 18 05 30.406392 +69 45 15.54228   10.92 10.34 10.128 9.804 F8/9V 82 0
36 HD 166227 * 18 05 30.6057092472 +62 19 00.582295044   9.05 8.15     K0 7 0
37 BD+65 1242 * 18 05 45.4316789520 +65 51 58.913436852   9.79 9.36     F5 5 0
38 HD 166578 * 18 06 40.5625937280 +64 13 17.129101692   7.63 6.68     K0 20 0
39 HD 166975 * 18 08 45.4795448688 +62 56 35.652639444   9.36 8.61     G5 3 0
40 V* LP Dra RS* 18 09 55.4986110768 +69 40 49.792233036       8.0   K2V 47 0
41 TYC 4433-597-1 * 18 10 49.9846105920 +70 16 09.989628132   11.30 10.62     K1V 6 0
42 TYC 4429-90-1 * 18 13 48.6185322408 +68 31 32.974444776   12.01 10.76     K2 2 0
43 * 36 Dra PM* 18 13 53.8328065738 +64 23 50.225760192   5.407 4.987 4.8   F5V 187 0
44 BD+65 1255 * 18 16 21.3672496440 +65 29 38.079108312   9.92 8.33     K5 2 0
45 TYC 4209-270-1 PM* 18 16 49.7250350376 +65 04 27.443789040   11.57 10.86     ~ 3 0
46 BD+70 990 * 18 18 31.8915786600 +70 42 16.882825428   10.86 10.04     G5 8 0
47 HD 169531 * 18 20 19.2938389872 +65 19 18.807298608   8.46 8.00     F8 20 0
48 TYC 4222-1770-1 PM* 18 21 47.0035178784 +63 57 14.589822924   10.52 9.75     K0 3 0
49 HD 170527 PM* 18 25 10.1138252544 +64 50 18.307185756   7.86 6.86     K0 39 0
50 RX J1825.5+6234 Ro* 18 25 33.0063568440 +62 34 14.704924548   11.52 10.37     K 6 0
51 HD 172066 PM* 18 32 30.2109965304 +68 36 51.098380164   8.11 7.59     G5 27 0
52 LSPM J1833+6513 PM* 18 33 48.068 +65 13 40.23       8.9   K3 4 0
53 TYC 4434-2172-1 * 18 34 33.9656443920 +69 31 45.447358908   12.04 11.24     K5 2 0
54 HD 172569 PM* 18 36 13.2672431064 +65 29 19.336764120 6.440 6.340 6.060     F0V 47 0
55 HD 172669 PM* 18 36 23.4527880600 +66 54 47.676863736   8.18 7.60     G3V 29 0
56 LSPM J1839+6903 PM* 18 39 25.6964120112 +69 03 03.569558184   12.1   11.522   M2.0Ve 15 0
57 BD+70 1017 PM* 18 40 43.2191136768 +70 38 49.635655764   10.30 9.41     K2~ 5 0
58 HD 173398 PM* 18 40 56.4085550640 +62 44 58.066829664   7.086 6.091     K0III 40 0
59 BD+69 1000 SB* 18 43 12.4683094704 +69 55 55.481744964   9.85 9.43     F0 3 0
60 NAME Gould Belt PoG ~ ~           ~ 832 1
61 NAME NEP Supercluster SCG ~ ~           ~ 10 0

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2023.02.08-01:31:20

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