J/AJ/159/121 V-band light curve & RVs of the Cepheid V473Lyr (Evans+, 2020)
X-ray observations of the peculiar Cepheid V473 Lyr identify a low-mass
companion.
Evans N.R., Pillitteri I., Molnar L., Szabados L., Plachy E., Szabo R.,
Engle S., Guinan E., Wolk S., Gunther H.M., Neilson H., Marengo M.,
Matthews L.D., Moschou S., Drake J.J., Kashyap V., Kervella P., Tordai T.,
Somogyi P., Burki G.
<Astron. J., 159, 121 (2020)>
=2020AJ....159..121E 2020AJ....159..121E
ADC_Keywords: X-ray sources; Stars, variable; Photometry, UBV; Photometry, CCD;
Radial velocities
Keywords: Cepheid variable stars ; Binary stars ; Massive stars ;
X-ray astronomy
Abstract:
V473Lyr is a classical Cepheid that is unique in having substantial
amplitude variations with a period of approximately 3.3yr, thought to
be similar to the Blazhko variations in RR Lyrae stars. We obtained an
X-ray Multi-Mirror Mission (XMM)-Newton observation of this star to
follow up a previous detection in X-rays. Rather than the X-ray burst
and rapid decline near maximum radius seen in δCephei itself,
the X-ray flux in V473Lyr remained constant for a third of the
pulsation cycle covered by the observation. Thus the X-rays are
probably not produced by the changes around the pulsation cycle. The
X-ray spectrum is soft (kT=0.6keV), with X-ray properties consistent
with a young low-mass companion. Previously there was no evidence of a
companion in radial velocities or in Gaia and Hipparcos proper
motions. While this rules out companions that are very close or very
distant, a binary companion at a separation between 30 and 300au is
possible. This is an example of an X-ray observation revealing
evidence of a low-mass companion, which is important in completing the
mass ratio statistics of binary Cepheids. Furthermore, the detection
of a young X-ray bright companion is a further indication that the
Cepheid (primary) is a Population I star, even though its pulsation
behavior differs from other classical Cepheids.
Description:
Since the pulsation amplitude of V473 Lyr is variable, photometry was
obtained near the time of the XMM observation obtained in 2019 (see
Section 2.1) to confirm the phases. Observations were made near
Budapest, Hungary, with a 15cm telescope, and an Orion StarShoot G3
CCD camera, in the V band. See Section 2.2 for further details.
Radial velocity data were collected on two nights from Hungary with a
30cm Newton telescope, and a Shelyak LHires III spectrograph, at
R=13000 resolution, on 2019 March 17, right before the XMM run
started, and again on March 24, for 2.3 and 2.7hr, respectively.
see Section 2.3 for further details.
V473 Lyr was observed by the Transiting Exoplanet Survey Satellite
(TESS) space telescope in Sector 14, a few months after the XMM run,
from 2019 July 18 to August 14. See Section 2.4 for further details.
Objects:
------------------------------------------------------------------------
RA (2000) DE Designation(s)
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19 15 59.49 +27 55 34.7 V473Lyr = Gaia DR2 2036471357742521728
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 24 1169 Photometry of V473 Lyr
table3.dat 24 27 Radial Velocities of V473 Lyr in 2019
table4.dat 21 1038 CORrelation RADial VELocities (CORAVEL) velocities
of V473Lyr discussed by Burki (2006JAVSO..35...19B 2006JAVSO..35...19B)
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See also:
B/xmm : XMM-Newton Observation Log (2002-2014)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
IX/55 : XMM-Newton Serendipitous Source Catalogue 3XMM-DR8 (XMM-SSC, 2018)
J/MNRAS/362/1167 : Radial velocities of 14 southern Cepheids (Petterson+, 2005)
J/AJ/136/1770 : VI light curves of NGC 247 Cepheids (Garcia-Varela+, 2008)
J/AJ/137/4598 : VR light curve of ASAS-North Cepheids (Schmidt+, 2009)
J/ApJ/694/1237 : BVRI light curves of NGC 247 Cepheids (Madore+, 2009)
J/PAZh/35/44 : BV light curves of 33 ASAS-3 Cepheids (Berdnikov+, 2009)
J/AcA/60/17 : VI light curves of SMC classical Cepheids (Soszynski+, 2010)
J/A+A/534/A94 : Milky Way Cepheids radial velocities (Storm+, 2011)
J/A+A/534/A95 : LMC Cepheids radial velocities (Storm+, 2011)
J/AcA/61/285 : VI light curves of Galactic Bulge Cepheids (Soszynski+,2011)
J/AJ/145/143 : XMM observations of α Per (Pillitteri+, 2013)
J/MNRAS/434/870 : Radial velocity curves of 3 Cepheids (Szabados+, 2013)
J/PAZh/40/147 : BVIc light curves of 57 Cepheids (Berdnikov+, 2014)
J/AJ/150/13 : Cepheid Radial Velocities (CRaV) project (Evans+, 2015)
J/ApJS/226/18 : 5yr radial velocity of 19 Cepheids (Anderson+, 2016)
J/AcA/68/89 : VI light curves of SMC type II Cepheids (Soszynski+, 2018)
J/A+A/622/A164 : Radial velocity curves of 11 Cepheids (Gallenne+, 2019)
J/A+A/623/A72 : Binarity of Hipparcos stars Gaia pm anomaly (Kervella+,2019)
J/A+A/631/A37 : Classical Cepheids consistent RVs (Borgniet+,2019)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 F12.6 d JD [58553/58565] Julian Date; JD-2400000
14- 18 F5.3 mag Vmag [6.039/6.253] Apparent V band magnitude
20- 24 F5.3 mag e_Vmag [0.001/0.002] Standard deviation in Vmag
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 10 F10.4 d JD [58559/58567] Julian Date; JD-2400000
12- 18 F7.3 km/s RV [-17.9/-13.1] Radial velocity
20- 24 F5.3 km/s e_RV [0.4/0.9] Standard deviation in RV
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 9 F9.3 d JD [43286/51130] Julian Date; JD-2400000
11- 16 F6.2 km/s RV [-33.8/5.7] Radial velocity
18- 21 F4.2 km/s e_RV [0.2/1.6] Standard deviation in RV
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 04-May-2020