J/AJ/161/193 BVRI light curve of RR Lyrae V* AX UMa (Li+, 2021)
AX UMa, an ab-type RR Lyrae star with a rapidly decreasing pulsation period, and
its binarity.
Li L.-J., Qian S.-B., Zhu L.-Y., He J.-J., Fang X.-H.
<Astron. J., 161, 193-193 (2021)>
=2021AJ....161..193L 2021AJ....161..193L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable; Stars, double and multiple; Photometry, UBVRI
Keywords: Sky surveys; RR Lyrae variable stars; Binary stars; CCD observation
Abstract:
The pulsation periods of RR-Lyrae stars usually vary with time, and
they are often used as probes to study the mechanism behind the
variation. After the early discovery that the pulsation period of the
RR-Lyrae star AXUMa decreased rapidly, in further research, we made
multiband photometric observations of this star using the Sino-Thai
70cm telescope and the 60cm telescope at Yunnan Observatories, and
collected its light-curve data from several photometry sky surveys.
The O-C diagram confirmed that AX UMa has a rapid period decrease with
a rate of -7.752±0.005days/Myr, which indicates that it is the
fastest-period decreasing ab-type RR Lyrae star in the Galactic field.
Moreover, the O-C residuals contain additional periodic variations. We
suppose that the variation with a long period is probably caused by
the light-travel time effect as the star orbits in a binary system.
The calculation shows that the lower mass limit of the companion is
about 1M☉. Combined with the full amplitudes and color indexes, we
suggested that the companion is probably a hot subdwarf star. We
compared the light curves of AXUMa and those of another binary
evolution pulsator, OGLE-BLG-RRLYR-02792, and found that the former
shows the characteristics of ab-type RR-Lyrae stars, while the latter
is more like an extreme long-period c-type RR-Lyrae star. However, the
absence of a bump in the light curves implies that the mass loss has
occurred in the outer atmosphere of AXUMa. The special features of
AXUMa make it worth more attention and further observations.
Description:
Between January 6th and 17th in 2019, we adopted the 60cm telescope
located in Yunnan observatory near Kunming city to observe AXUMa over
nine nights. Standard Johnson-Cousin Bessel filter BVI bands were used
in the observations. Due to the weather, location, and diameter of the
telescope, the quality of the data was not good. Therefore, the
Sino-Thai 70cm reflecting telescope at the Lijiang observational
station was used to monitor AXUMa for two nights (27 and 31 January
2019). During the observation, the BVRI bands were used to study its
color indexes and Apul in different filters.
Objects:
---------------------------------------------
RA (2000) DE Designation(s)
---------------------------------------------
11 38 26.84 +45 56 05.9 AX UMa = V* AX UMa
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 44 171 Times of light maximum and corresponding errors
of AX UMa determined from photometric surveys
and our observations
fig9.dat 16 1574 Color curves of AX UMa obtained by Sino-Thai
70cm telescope
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2017)
II/312 : GALEX-DR5 (GR5) sources from AIS and MIS (Bianchi+ 2011)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/MNRAS/368/1757 : Catalogue of RR Lyrae from NSVS (Wils+, 2006)
J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)
J/AJ/139/2639 : DY Peg times of light maximum (Li+, 2010)
J/other/IBVS/5959 : Minima and maxima of 436 variables (Huebscher+, 2011)
J/AJ/144/39 : Galactic RRab stars from GEOS RR Lyr Survey (Le Borgne+, 2012)
J/A+A/589/A94 : TU UMa light curves and maxima, CL Aur minima (Liska+, 2016)
J/ApJ/863/151 : Period analysis of 7 field RRab stars (Li+, 2018)
J/AJ/158/93 : Regression of stellar Teff in GaiaDR2 (Bai+, 2019)
J/A+A/635/A66 : Humps and bumps in RR Lyrae stars (Prudil+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.4 d HJD [27291/58512] Times of light maximum, HJD-2400000
12- 17 F6.4 d e_HJD [0.0002/0.01]? Uncertainty in HJD
19- 21 A3 --- Method Method used (1)
23- 28 I6 --- Epoch [-33808/24550] Epoch (cycle)
30- 36 F7.4 d O-C [-6.66/0.08] O-C, Equation 2
38- 44 A7 --- Ref Reference or source (2)
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Note (1): Methods as follows:
vis = visual (13 occurrences)
pg = photographic (134 occurrences)
ccd = Charge Coupled Device (24 occurrences)
Note (2): References and sources as follows:
Rom64 = Romano, 1964MmSAI..35..101R 1964MmSAI..35..101R
I2862 = Romano, 1986IBVS.2862....1R 1986IBVS.2862....1R
Bon85 = Boninsegna, 1985GEOCR...8.....B 1985GEOCR...8.....B
Sch95 = Schmidt+, 1995AJ....109.1239S 1995AJ....109.1239S
Wils06 = Wils+, 2006, J/MNRAS/368/1757
I5854 = Le Borgne+, 2008IBVS.5854....1L 2008IBVS.5854....1L
VS10 = Vandenbroere J., Salmon G., 2010, GEOS Circular RR45;
I5959 = Hubscher & Monninger, 2011, J/other/IBVS/5959
I6149 = Hubscher & Lehmann, 2015IBVS.6149....1H 2015IBVS.6149....1H
GaiaDr2 = Gaia Collaboration+, 2018, I/345
Fer15 = data from the GEOS RR Lyr Database observed by V. Ferrand, 2015.
AAVSO = American Association of Variable Star Observers
CRTS = Drake+, 2009, J/ApJ/696/870
DASCH = Grindlay+, 2009ASPC..410..101G 2009ASPC..410..101G
NSVS = Wozniak+, 2004AJ....127.2436W 2004AJ....127.2436W
QES = Alsubai+, 2013AcA....63..465A 2013AcA....63..465A
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Byte-by-byte Description of file: fig9.dat
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Bytes Format Units Label Explanations
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1- 6 F6.3 --- Phase [-0.25/1.25] Phase
8- 13 F6.3 --- Color [-0.01/0.63] Color Index
15- 16 A2 --- Ref Color Code; B-V, R-I, V-I or V-R
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 03-Aug-2021