J/ApJ/835/8 UBVR photometry of the T Tauri binary DQ Tau (Tofflemire+, 2017)
Accretion and magnetic reconnection in the classical T Tauri binary DQ Tau.
Tofflemire B.M., Mathieu R.D., Ardila D.R., Akeson R.L., Ciardi D.R.,
Johns-Krull C., Herczeg G.J., Quijano-Vodniza A.
<Astrophys. J., 835, 8-8 (2017)>
=2017ApJ...835....8T 2017ApJ...835....8T (SIMBAD/NED BibCode)
ADC_Keywords: Photometry, UBVRI ; YSOs ; Stars, double and multiple
Keywords: accretion, accretion disks; binaries: close;
stars: individual: DQ Tau; stars: formation
Abstract:
The theory of binary star formation predicts that close binaries
(a<100au) will experience periodic pulsed accretion events as streams
of material form at the inner edge of a circumbinary disk (CBD), cross
a dynamically cleared gap, and feed circumstellar disks or accrete
directly onto the stars. The archetype for the pulsed accretion theory
is the eccentric, short-period, classical T Tauri binary DQ Tau.
Low-cadence (∼daily) broadband photometry has shown brightening events
near most periastron passages, just as numerical simulations would
predict for an eccentric binary. Magnetic reconnection events (flares)
during the collision of stellar magnetospheres near periastron could,
however, produce the same periodic, broadband behavior when observed
at a one-day cadence. To reveal the dominant physical mechanism seen
in DQ Tau's low-cadence observations, we have obtained continuous,
moderate-cadence, multiband photometry over 10 orbital periods,
supplemented with 27 nights of minute-cadence photometry centered on
four separate periastron passages. While both accretion and stellar
flares are present, the dominant timescale and morphology of
brightening events are characteristic of accretion. On average, the
mass accretion rate increases by a factor of five near periastron, in
good agreement with recent models. Large variability is observed in
the morphology and amplitude of accretion events from orbit to orbit.
We argue that this is due to the absence of stable circumstellar disks
around each star, compounded by inhomogeneities at the inner edge of
the CBD and within the accretion streams themselves. Quasiperiodic
apastron accretion events are also observed, which are not predicted
by binary accretion theory.
Description:
The Las Cumbres Observatories Global Telescope (LCOGT) 1m network
consists of nine 1m telescopes spread across four international sites:
McDonald Observatory (USA), CTIO (Chile), SAAO (South Africa), and
Siding Springs Observatory (Australia).
Over the 2014-2015 winter observing season, our program requested
queued "visits" of DQ Tau 20 times per orbital cycle for 10 continuous
orbital periods. Given the orbital period of DQ Tau, the visit cadence
corresponded to ∼20hr. Each visit consisted of three observations in
each of the broadband UBVRIY and narrowband Hα and Hβ
filters, requiring ∼20 minutes.
In this work we present only the UBVR observations, which overlap with
our high-cadence observations.
Indeed, two eight-night observing runs centered on separate periastron
passages of DQ Tau (orbital cycles 3 and 5 in Figure 1) were obtained
from the WIYN 0.9m telescope located at the Kitt Peak National
Observatory. In addition to our two eight-night observing runs, a
synoptic observation program was also in place at the WIYN 0.9m that
provided approximately weekly observations of DQ Tau in UBVR during
the 2014-B semester. Also, using Apache Point Observatory's ARCSAT
0.5m telescope, we performed observing runs of seven and ten nights
centered on two separate periastron passaged of DQ Tau (orbital cycles
2 and 7 in Figure 1).
Objects:
--------------------------------------------------------------
RA (ICRS) DE Designation(s) (Period)
--------------------------------------------------------------
04 46 53.06 +17 00 00.2 DQ Tau = V* DQ Tau (P=15.8016)
--------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig1.dat 30 8948 DQ Tau UBVR lightcurves
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See also:
VI/135 : All-sky spectrally matched Tycho2 stars (Pickles+, 2010)
J/A+A/299/89 : COYOTES II (Bouvier+, 1995)
J/ApJS/101/117 : UBVRIJHKLMNQ photometry in Taurus-Auriga (Kenyon+ 1995)
J/AJ/130/873 : Properties of BQS objects in the SDSS DR3 area (Jester+, 2005)
J/AJ/131/1184 : A recalibration of optical photometry (Maiz-Apellaniz+, 2006)
J/A+A/479/827 : UBVR light curves of weak-line T Tauri stars (Grankin+, 2008)
J/AJ/140/483 : Flares of UV Cet type stars (Dal+, 2010)
J/ApJS/190/1 : A survey of stellar families (Raghavan+, 2010)
J/ApJ/731/8 : Multiple star formation in Taurus-Auriga (Kraus+, 2011)
J/ApJ/751/115 : Millimeter emission from Taurus binary systems (Harris+, 2012)
J/ApJS/207/15 : M dwarf flare spectra (Kowalski+, 2013)
J/A+A/561/A2 : 36 accreting YSOs emission lines (Alcala+, 2014)
J/AJ/147/82 : Monitoring of disk-bearing stars in NGC 2264 (Cody+, 2014)
J/ApJ/786/97 : Photospheric properties of T Tauri stars (Herczeg+, 2014)
J/A+A/570/A82 : Mapping accretion variability in NGC 2264 (Venuti+, 2014)
J/ApJ/788/59 : Parametric model for disks gas masses (Williams+, 2014)
Byte-by-byte Description of file: fig1.dat
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Bytes Format Units Label Explanations
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1 A1 --- Filt [UBVR] Filter used in the observation (1)
3- 15 F13.5 d HJD Heliocentric Julian Date
17- 22 F6.3 mag mag [11.8/16.4] Apparent magnitude in Filt
24- 28 F5.3 mag e_mag [0.003/0.2] Error in mag (2)
30 A1 --- Tel Telescope used in the observation (3)
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Note (1): Johnson system for the U and B filters and Cousins for
the V and R filters.
Note (2): The systematic errors in the UBVR magnitudes are 0.24, 0.10, 0.05,
and 0.07 magnitudes, respectively.
Note (3): Description of data reduction and calibration procedures can
be found in Section 2 of the paper. ARCSAT data are transformed
from SDSS to Johnson filters. Telescope as follows:
0 = Las Cumbres Observatories Global Telescope (LCOGT) 1m network;
1 = Apache Point Observatory's ARCSAT 0.5m telescope;
2 = WIYN0.9m/S2BK;
3 = WIYN0.9m/HDI.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 02-Aug-2017