RESOLVED COMPANIONS of CEPHEIDS: TESTING the CANDIDATES with X-RAY OBSERVATIONS

Nancy Remage Evans, Ignazio Pillitteri, Scott Wolk, Margarita Karovska, Evan Tingle, Edward Guinan, Scott Engle, Howard E. Bond, Gail H. Schaefer, Brian D. Mason

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

We have made XMM-Newton observations of 14 Galactic Cepheids that have candidate resolved (≥5″) companion stars based on our earlier HST Wide Field Camera 3 (WFC3) imaging survey. Main-sequence stars that are young enough to be physical companions of Cepheids are expected to be strong X-ray producers in contrast to field stars. XMM-Newton exposures were set to detect essentially all companions hotter than spectral type M0 (corresponding to 0.5 M). The large majority of our candidate companions were not detected in X-rays, and hence are not confirmed as young companions. One resolved candidate (S Nor #4) was unambiguously detected, but the Cepheid is a member of a populous cluster. For this reason, it is likely that S Nor #4 is a cluster member rather than a gravitationally bound companion. Two further Cepheids (S Mus and R Cru) have X-ray emission that might be produced by either the Cepheid or the candidate resolved companion. A subsequent Chandra observation of S Mus shows that the X-rays are at the location of the Cepheid/spectroscopic binary. R Cru and also V659 Cen (also X-ray bright) have possible companions closer than 5″ (the limit for this study) which are the likely sources of X-rays. One final X-ray detection (V473 Lyr) has no known optical companion, so the prime suspect is the Cepheid itself. It is a unique Cepheid with a variable amplitude. The 14 stars that we observed with XMM constitute 36% of the 39 Cepheids found to have candidate companions in our HST/WFC3 optical survey. No young probable binary companions were found with separations of ≥5″ or 4000 au.

Original languageEnglish (US)
Article number108
JournalAstronomical Journal
Volume151
Issue number4
DOIs
StatePublished - Apr 2016

Fingerprint

XMM-Newton telescope
x rays
newton
cameras
companion stars
star distribution
main sequence stars
stars
young

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Evans, N. R., Pillitteri, I., Wolk, S., Karovska, M., Tingle, E., Guinan, E., ... Mason, B. D. (2016). RESOLVED COMPANIONS of CEPHEIDS: TESTING the CANDIDATES with X-RAY OBSERVATIONS. Astronomical Journal, 151(4), [108]. https://doi.org/10.3847/0004-6256/151/4/108
Evans, Nancy Remage ; Pillitteri, Ignazio ; Wolk, Scott ; Karovska, Margarita ; Tingle, Evan ; Guinan, Edward ; Engle, Scott ; Bond, Howard E. ; Schaefer, Gail H. ; Mason, Brian D. / RESOLVED COMPANIONS of CEPHEIDS : TESTING the CANDIDATES with X-RAY OBSERVATIONS. In: Astronomical Journal. 2016 ; Vol. 151, No. 4.
@article{a693d897dca246e38815b57b3dcb2fb2,
title = "RESOLVED COMPANIONS of CEPHEIDS: TESTING the CANDIDATES with X-RAY OBSERVATIONS",
abstract = "We have made XMM-Newton observations of 14 Galactic Cepheids that have candidate resolved (≥5″) companion stars based on our earlier HST Wide Field Camera 3 (WFC3) imaging survey. Main-sequence stars that are young enough to be physical companions of Cepheids are expected to be strong X-ray producers in contrast to field stars. XMM-Newton exposures were set to detect essentially all companions hotter than spectral type M0 (corresponding to 0.5 M⊙). The large majority of our candidate companions were not detected in X-rays, and hence are not confirmed as young companions. One resolved candidate (S Nor #4) was unambiguously detected, but the Cepheid is a member of a populous cluster. For this reason, it is likely that S Nor #4 is a cluster member rather than a gravitationally bound companion. Two further Cepheids (S Mus and R Cru) have X-ray emission that might be produced by either the Cepheid or the candidate resolved companion. A subsequent Chandra observation of S Mus shows that the X-rays are at the location of the Cepheid/spectroscopic binary. R Cru and also V659 Cen (also X-ray bright) have possible companions closer than 5″ (the limit for this study) which are the likely sources of X-rays. One final X-ray detection (V473 Lyr) has no known optical companion, so the prime suspect is the Cepheid itself. It is a unique Cepheid with a variable amplitude. The 14 stars that we observed with XMM constitute 36{\%} of the 39 Cepheids found to have candidate companions in our HST/WFC3 optical survey. No young probable binary companions were found with separations of ≥5″ or 4000 au.",
author = "Evans, {Nancy Remage} and Ignazio Pillitteri and Scott Wolk and Margarita Karovska and Evan Tingle and Edward Guinan and Scott Engle and Bond, {Howard E.} and Schaefer, {Gail H.} and Mason, {Brian D.}",
year = "2016",
month = "4",
doi = "10.3847/0004-6256/151/4/108",
language = "English (US)",
volume = "151",
journal = "Astronomical Journal",
issn = "0004-6256",
publisher = "IOP Publishing Ltd.",
number = "4",

}

Evans, NR, Pillitteri, I, Wolk, S, Karovska, M, Tingle, E, Guinan, E, Engle, S, Bond, HE, Schaefer, GH & Mason, BD 2016, 'RESOLVED COMPANIONS of CEPHEIDS: TESTING the CANDIDATES with X-RAY OBSERVATIONS', Astronomical Journal, vol. 151, no. 4, 108. https://doi.org/10.3847/0004-6256/151/4/108

RESOLVED COMPANIONS of CEPHEIDS : TESTING the CANDIDATES with X-RAY OBSERVATIONS. / Evans, Nancy Remage; Pillitteri, Ignazio; Wolk, Scott; Karovska, Margarita; Tingle, Evan; Guinan, Edward; Engle, Scott; Bond, Howard E.; Schaefer, Gail H.; Mason, Brian D.

In: Astronomical Journal, Vol. 151, No. 4, 108, 04.2016.

Research output: Contribution to journalArticle

TY - JOUR

T1 - RESOLVED COMPANIONS of CEPHEIDS

T2 - TESTING the CANDIDATES with X-RAY OBSERVATIONS

AU - Evans, Nancy Remage

AU - Pillitteri, Ignazio

AU - Wolk, Scott

AU - Karovska, Margarita

AU - Tingle, Evan

AU - Guinan, Edward

AU - Engle, Scott

AU - Bond, Howard E.

AU - Schaefer, Gail H.

AU - Mason, Brian D.

PY - 2016/4

Y1 - 2016/4

N2 - We have made XMM-Newton observations of 14 Galactic Cepheids that have candidate resolved (≥5″) companion stars based on our earlier HST Wide Field Camera 3 (WFC3) imaging survey. Main-sequence stars that are young enough to be physical companions of Cepheids are expected to be strong X-ray producers in contrast to field stars. XMM-Newton exposures were set to detect essentially all companions hotter than spectral type M0 (corresponding to 0.5 M⊙). The large majority of our candidate companions were not detected in X-rays, and hence are not confirmed as young companions. One resolved candidate (S Nor #4) was unambiguously detected, but the Cepheid is a member of a populous cluster. For this reason, it is likely that S Nor #4 is a cluster member rather than a gravitationally bound companion. Two further Cepheids (S Mus and R Cru) have X-ray emission that might be produced by either the Cepheid or the candidate resolved companion. A subsequent Chandra observation of S Mus shows that the X-rays are at the location of the Cepheid/spectroscopic binary. R Cru and also V659 Cen (also X-ray bright) have possible companions closer than 5″ (the limit for this study) which are the likely sources of X-rays. One final X-ray detection (V473 Lyr) has no known optical companion, so the prime suspect is the Cepheid itself. It is a unique Cepheid with a variable amplitude. The 14 stars that we observed with XMM constitute 36% of the 39 Cepheids found to have candidate companions in our HST/WFC3 optical survey. No young probable binary companions were found with separations of ≥5″ or 4000 au.

AB - We have made XMM-Newton observations of 14 Galactic Cepheids that have candidate resolved (≥5″) companion stars based on our earlier HST Wide Field Camera 3 (WFC3) imaging survey. Main-sequence stars that are young enough to be physical companions of Cepheids are expected to be strong X-ray producers in contrast to field stars. XMM-Newton exposures were set to detect essentially all companions hotter than spectral type M0 (corresponding to 0.5 M⊙). The large majority of our candidate companions were not detected in X-rays, and hence are not confirmed as young companions. One resolved candidate (S Nor #4) was unambiguously detected, but the Cepheid is a member of a populous cluster. For this reason, it is likely that S Nor #4 is a cluster member rather than a gravitationally bound companion. Two further Cepheids (S Mus and R Cru) have X-ray emission that might be produced by either the Cepheid or the candidate resolved companion. A subsequent Chandra observation of S Mus shows that the X-rays are at the location of the Cepheid/spectroscopic binary. R Cru and also V659 Cen (also X-ray bright) have possible companions closer than 5″ (the limit for this study) which are the likely sources of X-rays. One final X-ray detection (V473 Lyr) has no known optical companion, so the prime suspect is the Cepheid itself. It is a unique Cepheid with a variable amplitude. The 14 stars that we observed with XMM constitute 36% of the 39 Cepheids found to have candidate companions in our HST/WFC3 optical survey. No young probable binary companions were found with separations of ≥5″ or 4000 au.

UR - http://www.scopus.com/inward/record.url?scp=84963704179&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84963704179&partnerID=8YFLogxK

U2 - 10.3847/0004-6256/151/4/108

DO - 10.3847/0004-6256/151/4/108

M3 - Article

AN - SCOPUS:84963704179

VL - 151

JO - Astronomical Journal

JF - Astronomical Journal

SN - 0004-6256

IS - 4

M1 - 108

ER -

Evans NR, Pillitteri I, Wolk S, Karovska M, Tingle E, Guinan E et al. RESOLVED COMPANIONS of CEPHEIDS: TESTING the CANDIDATES with X-RAY OBSERVATIONS. Astronomical Journal. 2016 Apr;151(4). 108. https://doi.org/10.3847/0004-6256/151/4/108