2017ApJ...838...67E


C.D.S. - SIMBAD4 rel 1.7 - 2020.01.20CET15:53:15

2017ApJ...838...67E - Astrophys. J., 838, 67-67 (2017/March-3)

The Secret Lives of Cepheids: δ Cep-the prototype of a new class of pulsating X-ray variable stars.

ENGLE S.G., GUINAN E.F., HARPER G.M., CUNTZ M., EVANS N.R., NEILSON H.R. and FAWZY D.E.

Abstract (from CDS):

From our Secret Lives of Cepheids program, the prototype Classical Cepheid, δ Cep, is found to be an X-ray source with periodic pulsation-modulated X-ray variations. This finding complements our earlier reported phase-dependent FUV-UV emissions of the star that increase ∼10-20 times with highest fluxes at ∼0.90–0.95φ, just prior to maximum brightness. Previously δ Cep was found as potentially X-ray variable, using XMM-Newton observations. Additional phase-constrained data were secured with Chandra near X-ray emission peak, to determine if the emission and variability were pulsation-phase-specific to δ Cep and not transient or due to a possible coronally active, cool companion. The Chandra data were combined with prior XMM-Newton observations, and were found to very closely match the previously observed X-ray behavior. From the combined data set, a ∼4 increase in X-ray flux is measured, reaching a peak LX = 1.7 x 1029 erg s–1 near 0.45ph. The precise X-ray flux phasing with the star's pulsation indicates that the emissions arise from the Cepheid and not from a companion. However, it is puzzling that the maximum X-ray flux occurs ∼0.5ph (∼3 days) later than the FUV-UV maximum. There are several other potential Cepheid X-ray detections with properties similar to δ Cep, and comparable X-ray variability is indicated for two other Cepheids: β Dor and V473 Lyr. X-ray generating mechanisms in δ Cep and other Cepheids are discussed. If additional Cepheids are confirmed to show phased X-ray variations, then δ Cep will be the prototype of a new class of pulsation-induced X-ray variables.

Abstract Copyright: © 2017. The American Astronomical Society. All rights reserved.

Journal keyword(s): stars: activity - stars: atmospheres - stars: individual: δ Cep - stars: variables: Cepheids - ultraviolet: stars - X-rays: stars - X-rays: stars

Simbad objects: 17

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Number of rows : 17

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 * alf UMi cC* 02 31 49.09456 +89 15 50.7923 3.00 2.62 2.02 1.53 1.22 F8Ib 603 2
2 Cl Melotte 22 OpC 03 47 00 +24 07.0           ~ 2924 0
3 * bet Cam * 05 03 25.0896309 +60 26 32.089527 5.57 4.95 4.02 3.33 2.86 G1Ib 162 0
4 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14462 1
5 HD 36705 TT* 05 28 44.8916324761 -65 26 55.289846904 8.259 7.856 6.999 6.496 5.993 K0V 919 0
6 * bet Dor cC* 05 33 37.5125319201 -62 29 23.323100433 5.13 4.58 3.76 3.55 3.12 F8/G0Ib 343 0
7 NAME Orion Nebula Cluster OpC 05 35.0 -05 29           ~ 1921 1
8 V* S Mus cC* 12 12 47.0194644681 -70 09 06.436474127 7.58 8.80 8.33 7.39 5.196 F6Ib+B5V 234 0
9 V* R Cru cC* 12 23 37.6883962336 -61 37 44.856977549 7.41 7.00 6.42     F7Ib/II 139 0
10 V* V659 Cen cC* 13 31 33.4103851030 -61 34 56.514647163 7.57 7.19 6.49     F6/7Ib+B6V 91 1
11 * pi. Her V* 17 15 02.8343634 +36 48 32.984340 6.28 4.61 3.18 2.22 1.49 K3II 227 0
12 * bet Dra * 17 30 25.9616959 +52 18 04.999351 4.43 3.79 2.81 2.12 1.64 G2Ib-IIa 388 0
13 V* V473 Lyr cC* 19 15 59.4894683081 +27 55 34.683764506 7.18 6.770 6.153     F8Ib-II 202 0
14 V* RR Lyr RR* 19 25 27.9123232234 +42 47 03.690634101   7.36   7.6   A8-F7 876 0
15 * gam Aql * 19 46 15.5802908 +10 36 47.740788 5.93 4.23 2.72 1.65 0.87 K3II 417 0
16 HD 213307 V*? 22 29 09.2460235698 +58 24 14.743960258 5.95 6.28 6.30     B7IV 142 0
17 * del Cep cC* 22 29 10.2650184 +58 24 54.713856 4.71 4.35 3.75   3.219 F5Iab:+B7-8 671 0

    Equat.    Gal    SGal    Ecl

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2020.01.20-15:53:15

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