DRAFT VERSION OCTOBER 1, 2019
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MINERVA-Australis I: Design, Commissioning, & First Photometric Results
BRETT ADDISON,
1
DUNCAN J. WRIGHT,
1
ROBERT A. WITTENMYER,
1
JONATHAN HORNER,
1
MATTHEW W. MENGEL,
1
DANIEL JOHNS,
2
CONNOR MARTI,
3
BELINDA NICHOLSON,
1
JACK OKUMURA,
1
BRENDAN BOWLER,
4
IAN CROSSFIELD,
5
STEPHEN R. KANE,
6
JOHN KIELKOPF,
7
PETER PLAVCHAN,
8
C.G. TINNEY,
9
HUI ZHANG,
10
JAKE T. CLARK,
1
MATHIEU CLERTE,
1
JASON D. EASTMAN,
11
JON SWIFT,
12
MICHAEL BOTTOM,
13
PHILIP MUIRHEAD,
14
NATE MCCRADY,
15
ERICH HERZIG,
13
KRISTINA HOGSTROM,
13
MAURICE WILSON,
11
DAVID SLISKI,
16
SAMSON A. JOHNSON,
17
JASON T. WRIGHT,
18, 19
CULLEN BLAKE,
16
REED RIDDLE,
13
BRIAN LIN,
13
MATTHEW CORNACHIONE,
20
TIMOTHY R. BEDDING,
21, 22
DENNIS STELLO,
23
DANIEL HUBER,
24
STEPHEN MARSDEN,
1
AND BRADLEY D. CARTER
1
1
University of Southern Queensland, Centre for Astrophysics, West Street, Toowoomba, QLD 4350 Australia
2
Department of Physical Sciences, Kutztown University, Kutztown, PA 19530, USA
3
Department of Astronomy, Williams College, 33 Lab Campus Drive, Williamstown, MA 01267 USA
4
Department of Astronomy, The University of Texas at Austin, TX 78712, USA
5
Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
6
Department of Earth Sciences, University of California, Riverside, CA 92521, USA
7
Department of Physics and Astronomy, University of Louisville, Louisville, KY 40292, USA
8
Department of Physics & Astronomy, George Mason University, 4400 University Drive MS 3F3, Fairfax, VA 22030, USA
9
Exoplanetary Science at UNSW, School of Physics, UNSW Sydney, NSW 2052, Australia
10
School of Astronomy and Space Science, Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education,
Nanjing University, Nanjing 210046, Jiangsu, China
11
Center for Astrophysics, Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
12
The Thacher School, 5025 Thacher Road, Ojai, CA 93023, USA
13
California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA
14
Department of Astronomy, Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA
02215, USA
15
University of Montana, Department of Physics and Astronomy, 32 Campus Drive, No. 1080, Missoula, Montana 59812, USA
16
Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA
17
Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA
arXiv:1901.11231v3 [astro-ph.IM] 30 Sep 2019
2 Addison et al.
18
Department of Astronomy & Astrophysics, 525 Davey Laboratory The Pennsylvania State University, University Park, PA,
16802, USA
19
Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory The Pennsylvania State University, University Park, PA,
16802, USA
20
Department of Physics, United States Naval Academy, 572C Holloway Rd, Annapolis, MD 21402, USA
21
Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006, Australia
22
Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus
C, Denmark
23
School of Physics, University of New South Wales, NSW 2052, Australia
24
Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
(Published November 2019)
Submitted to Publications of the Astronomical Society of the Pacific
ABSTRACT
The MINERVA-Australis telescope array is a facility dedicated to the follow-up, confir-
mation, characterization, and mass measurement of planets orbiting bright stars discovered
by the Transiting Exoplanet Survey Satellite (TESS) – a category in which it is almost
unique in the Southern Hemisphere. It is located at the University of Southern Queens-
land’s Mount Kent Observatory near Toowoomba, Australia. Its flexible design enables
multiple 0.7 m robotic telescopes to be used both in combination, and independently, for
high-resolution spectroscopy and precision photometry of TESS transit planet candidates.
MINERVA-Australis also enables complementary studies of exoplanet spin-orbit alignments
via Doppler observations of the Rossiter-McLaughlin effect, radial velocity searches for non-
transiting planets, planet searches using transit timing variations, and ephemeris refinement
for TESS planets. In this first paper, we describe the design, photometric instrumentation,
software, and science goals of MINERVA-Australis, and note key differences from its North-
ern Hemisphere counterpart, the MINERVA array. We use recent transit observations of four
PASP 3
planets, WASP-2b, WASP-44b, WASP-45b, and HD 189733b, to demonstrate the photomet-
ric capabilities of MINERVA-Australis.
1. INTRODUCTION
There has long been interest in the discovery of planets around other stars. Early attempts to find such
worlds, however, got off to a slow and rocky start with several exoplanetary detection claims being ei-
ther later retracted, or never confirmed, such as the proposed planets orbiting 70 Ophiuchi (Jacob 1855),
Barnard’s Star, (van de Kamp 1963; Gatewood 1995), and the pulsar PSR B1829-10 (Bailes et al. 1991;
Lyne & Bailes 1992)). It took until the announcement of the first confirmed exoplanet orbiting a Sun-like
star in 1995 (51 Pegasi b; Mayor & Queloz 1995) to truly kick off the “Exoplanet Era.”
In the years immediately following that discovery, the number of confirmed exoplanets grew slowly. As
we have become ever more adept at finding new planets, however, the number known has grown exponen-
tially, especially over the last decade. This is due, in large part, to the extremely successful Kepler mission
launched by NASA in 2009 (Koch et al. 2010) to search for planets via their transits. The spacecraft’s four
year primary mission, together with its more recent K2 program extension (Howell et al. 2014), confirmed
the existence of over 2500 planets
1
, including many that resemble nothing found in the solar system.
This incredible diversity includes the so-called ’hot Jupiters’ and ’hot Neptunes’ (e.g., Mayor & Queloz
1995; Charbonneau et al. 2000; Gillon et al. 2007; Bakos et al. 2010; Bayliss et al. 2013), planets moving
on extremely eccentric orbits (e.g., Jones et al. 2006; Wittenmyer et al. 2017), planets with densities greater
than iron and even osmium (e.g., Deleuil et al. 2008; Dumusque et al. 2014; Johns et al. 2018), or compara-
ble to styrofoam (e.g., Faedi et al. 2011; Welsh et al. 2015; Pepper et al. 2017). Perhaps most surprisingly,
Kepler revealed that planets between the size of Earth and Neptune (“super-Earths” or “mini-Neptunes”)
are incredibly common, despite the fact that no analog exists in the solar system (e.g., Charbonneau et al.
2009; Barragán et al. 2018).
The primary goals of Kepler were to perform a detailed exoplanet census and to measure the frequency
distribution function for planets around other stars. This was accomplished by continually monitoring
1
See https://exoplanetarchive.ipac.caltech.edu/ for the latest tally.
4 Addison et al.
∼150,000 stars in the northern constellation of Cygnus for transits (Koch et al. 2010) for a period in excess
of four years. Chief among Kepler’s results is the revelation that planets are ubiquitous, and that the majority
of stars host small planets, with mini-Neptunes and super-Earths being the most common of those found
on orbits of ≤ 200 days (Fressin et al. 2013). Kepler also revealed that Earth-sized planets (0.5 ≤ R
P
≤
1.4R
⊕
) are particularly common around cool stars (T
eff
≤ 4000 K), with an occurrence rate of just over 50%
(Dressing & Charbonneau 2013). Indeed, based on Kepler data, Dressing & Charbonneau estimated the
occurrence rate of Earth-size planets in the habitable zone as 0.15
+0.13
−0.06
planets per cool star. This suggest
that the nearest transiting Earth-size planet in the habitable zone could be located within 21 pc of Earth.
Despite the stunning success of the Kepler mission, little is known about the compositions, masses, and
densities of the majority of the Kepler planets. The reason for this is that the majority of the planet-hosting
stars identified by Kepler are either too faint for further follow-up investigations using existing facilities,
or would require an inordinate investment of time on large telescopes. Because of the significant resources
that are required to convert the large number of Kepler candidates into confirmed planets and measure their
masses, only about 50% of Kepler’s candidate planets have been confirmed, and of these, only ∼ 10% have
mass measurements
2
.
On 2018 April 18, NASA launched its next-generation exoplanet finder, the Transiting Exoplanet Survey
Satellite (TESS; Ricker et al. 2015). Unlike Kepler, which observed a single small region on the sky, TESS
expands the search for planets to nearly the entire sky. TESS consists of four wide-angle cameras that each
have a field of view of 24
◦
× 24
◦
, yielding a total field of view for TESS of 96
◦
× 24
◦
. The spacecraft is
oriented such that one of the cameras is centered on one of the ecliptic poles while the others are pointed
progressively closer to the ecliptic. TESS will monitor each 24
◦
wide strip on the celestial sphere for a
period of 27 days before moving on to an adjacent strip of the sky. As such, the majority of stars will be
observed for 27 days, while those closer to the ecliptic poles will be observed for longer. As a result of this
strategy, stars within ∼ 12
◦
of the ecliptic poles will be observed for a year. TESS will observe the southern
2
Determined using the NASA Exoplanet Archive (https://exoplanetarchive.ipac.caltech.edu/). There are 2347 confirmed Ke-
pler planets and 244 of them have mass measurements listed in the table.
PASP 5
ecliptic hemisphere in its first year of operation before moving on to the northern ecliptic hemisphere in the
second year of its mission.
Throughout the course of its initial two-year mission, TESS will survey approximately 200,000 of the
brightest stars in the sky with a cadence of two minutes. Planets discovered around these bright stars
will be suitable for ground-based follow-up observations to both confirm their existence and facilitate their
characterization (e.g. Huang et al. 2018; Gandolfi et al. 2018). Data will also be returned on an additional
20 million stars from ”full-frame images”, taken with a cadence of 30 minutes. As a result, there will be no
shortage of planet candidates coming from TESS that will need follow-up observations. Additionally, stars
observed by TESS will be, on average, a hundred times brighter than those observed by Kepler, and it is
expected that TESS will deliver a yield of thousands of new planets orbiting bright stars.
With the expected flood of planet candidates being found by TESS to be orbiting bright stars, dedicated
facilities are urgently needed to confirm the candidates and characterize them. The radial velocity technique
is the primary method to deliver the critical planetary parameters, such as mass and orbital eccentricity,
that are required to properly characterize the planetary system. Most of the existing facilities capable of
carrying out the required high-precision radial velocity measurements, however, are subject to intense com-
petition and scheduling constraints (particularly on shared large telescopes). Traditionally, radial velocity
programs are allocated blocks of time (a couple of weeks to a month) on large telescopes during bright
nights (though some such as the Hobby-Eberly Telescope and WIYN are working to facilitate queue and
cadence observations).
With the expected large number of planet candidates to be delivered by TESS, the most exciting of which
will be low-mass planets with orbital periods exceeding one month (in particular those planets orbiting
within the habitable zone around M-dwarf stars), this strategy simply will not work. This is the primary
cause of the significant bottlenecks experienced during the follow-up work carried out on Kepler candidates
(Fleming et al. 2015).
Similarly with TESS, we will be in a situation where we have too many planets, and too few telescopes to
confirm them.
