MUSCAT2

End of night form

MuSCAT2 is an instrument that has been offered at the Carlos Sánchez Telescope since 2018. It has been developed by the Center for Astrobiology and the University of Tokyo (P.I. Norio Narita) in collaboration with the IAC (P.I. Enric Palle). It allows simultaneous photometry in the g (400 to 550 nm), r (550 to 700 nm), i (700 to 820 nm) and z_s (820 to 920 nm) bands. 146 nights a year are reserved for the team that developed the instrument, but MuSCAT2 is offered as a common user instrument, following the rules of other CAT telescopes. Applicants should note that some targets related to extrasolar planets are protected.

The article MuSCAT2: four-color simultaneous camera for the 1.52-m Telescopio Carlos Sánchez, where all the relevant information about this instrument appears, is available at:

Narita et al. (2019), Journal of Astronomical Telescopes, Instruments, and Systems, Volume 5, id. 015001

An image of MuSCAT2 installed at the Cassegrain focus of the 1.52 m TCS telescope (Fig. 2, Narita et al. 2019).

Physical characteristics

The optical system of MuSCAT2 is composed of $F$-conversion lenses (lens-1 and lens-2) to widen the field-of-view (FoV) and dichroic mirrors (DMs) to separate the light into four-wavelength bands.

Layout of the TCS and MuSCAT2 optical system. The left side shows the ray tracing of the entire telescope and instrument system. The right side is a zoomed-in view of MuSCAT2 ray tracing. The incident light is divided into four channels by three DMs. The F-conversion lenses are placed before (lens-1) and after (lens-2) the DMs. Plane mirrors (PM) are inserted into channels 1 to 3 to fold the optical path. Bandpass filters (BF) are inserted just before the CCD cameras. Instrument sizes are described in millimeters (Fig. 1, Narita et al. 2019).

You can find a technical description of the cameras in this document.

• Pixel size:

  -0.434 “/px for g and r (7.41 arcmin x 7.41 arcmin)
  -0.435 “/px for i (7.43 arcmin x 7.43 arcmin)
  -0.436 “/px for z_s (7.44 arcmin x 7.44 arcmin)

Filters

MuSCAT2 is equipped with a griz_s filter set, located on channel 1 to 4, respectively.

Linearity

Measured fluxes (abscissa) and relationships between measured fluxes and expected fluxes (ordinate) for the CCD cameras for bands (a) g, (b) r, (c) i and (d) z_s, respectively. The orange solid lines represent the best-fit linear function models. The gray dotted lines indicate boundaries of 1% nonlinearity (Fig. 10, Narita et al. 2019).

Quantum efficiency

The total transmittance of the MuSCAT2 instrument, including all optics and quantum efficiency of the detectors, is plotted in the figure below.

Total transmittance of the MuSCAT2 instrument in the g (blue), r (green), i (orange), and z_s (red) bands from left to right. (Fig. 7 from Narita et al. 2019)

Pipeline

Basic reduction (dark images subtraction and flatfield correction) is performed at the end of each night. Observers will have access to to both raw and pre-reduced data.

ETC

The following figure can be used as an estimator of the exposure time as a function of the target’s magnitude.

While developing a dedicated ETC, we remind users that the “mov” command can be used to acquire tests images to check the flux level. The limiting quantities of MuSCAT2 that give a signal-to-noise ratio (S/N) of 10 with a 10-minute exposure are $g_{\lim }^{\prime }=20.5\mathrm{mag}$, $r_{\lim }^{\prime }=20.5\mathrm{mag}$, $i_{\lim }^{\prime }=19.7\mathrm{mag}$, and $z_{\lim }^{\prime }=19.0\mathrm{mag}$.

SDSS magnitudes (abscissa) versus expected errors over 600 s in magnitude (ordinate) for bands (a) g, (b) r, (c) i, and (d) z_s, respectively. The solid black, dashed magenta, dotted orange, and aquamarine dot-dashed lines represent total noise, stellar noise, readout noise, and sky noise, respectively. (from Fig. 9, Narita et al. 2019)

 List of representative papers (more papers can be found here)

– Exoplanets

Peterson et al. 2023, Nature, Volume 617, Issue 7962, p.701-705
A temperate Earth-sized planet with tidal heating transiting an M6 star
https://urldefense.com/v3/__https://ui.adsabs.harvard.edu/abs/2023Natur.617..701P/abstract__;!!D9dNQwwGXtA!T5IX90voKno2J-HR7NgoxPip0ZdblYLamP_b4H6GBztB9Sbd2gk0JRfzBsVWZKLo5CaXDYxC08NEcL82FGrbDgYGrXQ$

Trifonov et al. 2021, Science, Volume 371, Issue 6533, pp. 1038-1041
A nearby transiting rocky exoplanet that is suitable for atmospheric investigation
https://urldefense.com/v3/__https://ui.adsabs.harvard.edu/abs/2021Sci…371.1038T/abstract__;!!D9dNQwwGXtA!T5IX90voKno2J-HR7NgoxPip0ZdblYLamP_b4H6GBztB9Sbd2gk0JRfzBsVWZKLo5CaXDYxC08NEcL82FGrbKg0s2j0$

Vanderburg et al. 2020, Nature, Volume 585, Issue 7825, p.363-367
A giant planet candidate transiting a white dwarf
https://urldefense.com/v3/__https://ui.adsabs.harvard.edu/abs/2020Natur.585..363V/abstract__;!!D9dNQwwGXtA!T5IX90voKno2J-HR7NgoxPip0ZdblYLamP_b4H6GBztB9Sbd2gk0JRfzBsVWZKLo5CaXDYxC08NEcL82FGrbf4HwdCU$

– Solar System Small Bodies

Slivan et al. 2023, Icarus, Volume 405, article id. 115701
Spin vectors in the Koronis family: V. Resolving the ambiguous rotation period of (3032) Evans
https://urldefense.com/v3/__https://ui.adsabs.harvard.edu/abs/2023Icar..40515701S/abstract__;!!D9dNQwwGXtA!T5IX90voKno2J-HR7NgoxPip0ZdblYLamP_b4H6GBztB9Sbd2gk0JRfzBsVWZKLo5CaXDYxC08NEcL82FGrb9xRVO9w$

Pinilla-Alonso et al. 2022, The Planetary Science Journal, Volume 3,
Issue 12, id.267
Detection of the Irregular Shape of the Southern Limb of Menoetius from Observations of the 2017-2018 Patroclus-Menoetius Mutual Events
https://urldefense.com/v3/__https://ui.adsabs.harvard.edu/abs/2022PSJ…..3..267P/abstract__;!!D9dNQwwGXtA!T5IX90voKno2J-HR7NgoxPip0ZdblYLamP_b4H6GBztB9Sbd2gk0JRfzBsVWZKLo5CaXDYxC08NEcL82FGrbdhs1JYA$

– Stars

Maas et al. 2022, Astronomy & Astrophysics, Volume 668, id.A111
Lower-than-expected flare temperatures for TRAPPIST-1
https://urldefense.com/v3/__https://ui.adsabs.harvard.edu/abs/2022A*26A…668A.111M/abstract__;JQ!!D9dNQwwGXtA!T5IX90voKno2J-HR7NgoxPip0ZdblYLamP_b4H6GBztB9Sbd2gk0JRfzBsVWZKLo5CaXDYxC08NEcL82FGrbj367ptk$

– Transients

Tampo et al. 2020, Publications of the Astronomical Society of Japan,
Volume 72, Issue 3, id.49
First detection of two superoutbursts during the rebrightening phase of a WZ Sge-type dwarf nova: TCP J21040470+4631129
https://urldefense.com/v3/__https://ui.adsabs.harvard.edu/abs/2020PASJ…72…49T/abstract__;!!D9dNQwwGXtA!T5IX90voKno2J-HR7NgoxPip0ZdblYLamP_b4H6GBztB9Sbd2gk0JRfzBsVWZKLo5CaXDYxC08NEcL82FGrbT5z-ZqE$ —

Gallery

M57, a composition of gri images, 10s exposures

Example light curve of Wasp-12b, observed during commissioning. The precision of photometry reaches 629 ppm (g), 616 ppm (r), 834 ppm (i) and 1166 ppm (z).

Part of the developer team during the installation of MuSCAT2.