IMACS: the wide-field imaging spectrograph on Magellan-Baade

Dressler, Alan; Hare, Tyson; Bigelow, Bruce C.; Osip, D. J.

doi:10.1117/12.670573

Cited by 92 publications

(45 citation statements)

References 4 publications

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“…In addition to the PS1 photometry, we also obtained one epoch of r-band imaging for PS1-11bbq with Gemini GMOS (Hook et al 2004), one epoch of ri-band imaging for PS1-12brf with Magellan IMACS (Dressler et al 2006) and one (A color version of this figure is available in the online journal.) epoch of r-band imaging for PS1-13ess with Magellan IMACS.…”

Section: Other Transient Photometrymentioning

confidence: 99%

Rapidly Evolving and Luminous Transients From Pan-Starrs1

Drout

Chornock

Söderberg

et al. 2014

ApJ

315

442

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In the past decade, several rapidly evolving transients have been discovered whose timescales and luminosities are not easily explained by traditional supernovae (SNe) models. The sample size of these objects has remained small due, at least in part, to the challenges of detecting short timescale transients with traditional survey cadences. Here we present the results from a search within the Pan-STARRS1 Medium Deep Survey (PS1-MDS) for rapidly evolving and luminous transients. We identify 10 new transients with a time above half-maximum (t 1/2 ) of less than 12 days and −16.5 > M > −20 mag. This increases the number of known events in this region of SN phase space by roughly a factor of three. The median redshift of the PS1-MDS sample is z = 0.275 and they all exploded in star-forming galaxies. In general, the transients possess faster rise than decline timescale and blue colors at maximum light (g P1 − r P1 −0.2). Best-fit blackbodies reveal photospheric temperatures/radii that expand/cool with time and explosion spectra taken near maximum light are dominated by a blue continuum, consistent with a hot, optically thick, ejecta. We find it difficult to reconcile the short timescale, high peak luminosity (L > 10 43 erg s −1 ), and lack of UV line blanketing observed in many of these transients with an explosion powered mainly by the radioactive decay of 56 Ni. Rather, we find that many are consistent with either (1) cooling envelope emission from the explosion of a star with a low-mass extended envelope that ejected very little (<0.03 M ) radioactive material, or (2) a shock breakout within a dense, optically thick, wind surrounding the progenitor star. After calculating the detection efficiency for objects with rapid timescales in the PS1-MDS we find a volumetric rate of 4800-8000 events yr −1 Gpc −3 (4%-7% of the core-collapse SN rate at z = 0.2).

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Section: Other Transient Photometrymentioning

confidence: 99%

Rapidly Evolving and Luminous Transients From Pan-Starrs1

Drout

Chornock

Söderberg

et al. 2014

ApJ

315

442

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“…One transit was observed in 2007 with IMACS on the Magellan Baade telescope (Dressler et al 2006). We used the f/ 4 imaging mode with a subraster on one of the eight instrument CCDs (chip 2), reading out 1200 × 1200 pixels centered around x = 1080 and y = 3015, in order to decrease the readout time to roughly 35 s frame −1 in FAST mode.…”

Section: Observations and Data Analysismentioning

confidence: 99%

TWENTY-ONE NEW LIGHT CURVES OF OGLE-TR-56b: NEW SYSTEM PARAMETERS AND LIMITS ON TIMING VARIATIONS

Adams¹,

López‐Morales²,

Elliot³

et al. 2011

ApJ

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Although OGLE-TR-56b was the second transiting exoplanet discovered, only one light curve, observed in 2006, has been published besides the discovery data. We present 21 light curves of 19 different transits observed between 2003 July and 2009 July with the Magellan Telescopes and Gemini South. The combined analysis of the new light curves confirms a slightly inflated planetary radius relative to model predictions, with R p = 1.378 ± 0.090 R J . However, the values found for the transit duration, semimajor axis, and inclination values differ significantly from the previous result, likely due to systematic errors. The new semimajor axis and inclination, a = 0.01942 ± 0.00015 AU and i = 73.• 72 ± 0.• 18, are smaller than previously reported, while the total duration, T 14 = 7931 ± 38 s, is 18 minutes longer. The transit midtimes have errors from 23 s to several minutes, and no evidence is seen for transit midtime or duration variations. Similarly, no change is seen in the orbital period, implying a nominal stellar tidal decay factor of Q * = 10 7 , with a 3σ lower limit of 10 5.7 .

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“…The f/4 provides higher resolution spectra, up toR 5000, over a smaller, ¢ 15 square field. The detector of each camera is composed of eight 2 K×4 K CCDs, forming an 8 K×8 K mosaic (Dressler et al 2006).…”

Section: Observational Designmentioning

confidence: 99%

ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

Rackham

Espinoza

Apai

et al. 2017

ApJ

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GJ1214b is the most studied sub-Neptune exoplanet to date. Recent measurements have shown its near-infrared transmission spectrum to be flat, pointing to a high-altitude opacity source in the exoplanetʼs atmosphere, either equilibrium condensate clouds or photochemical hazes. Many photometric observations have been reported in the optical by different groups, though simultaneous measurements spanning the entire optical regime are lacking. We present an optical transmission spectrum (4500-9260Å) of GJ1214b in 14 bins, measured with Magellan/IMACS repeatedly over three transits. We measure a mean planet-to-star radius ratio of ( ) in the spectral bins. The optical transit depths are shallower on average than observed in the near-infrared. We present a model for jointly incorporating the effects of a composite photosphere and atmospheric transmission through the exoplanetʼs limb (the CPAT model), and use it to examine the cases of absorber and temperature heterogeneities in the stellar photosphere. We find the optical and near-infrared measurements are best explained by the combination of (1) photochemical haze in the exoplanetary atmosphere with a mode particle size r=0.1μm and haze-forming efficiency = f 10% haze and (2) faculae in the unocculted stellar disk with a temperature contrast D = -+ T 354 46 46 K, assuming 3.2% surface coverage. The CPAT model can be used to assess potential contributions of heterogeneous stellar photospheres to observations of exoplanet transmission spectra, which will be important for searches for spectral features in the optical.

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IMACS: the wide-field imaging spectrograph on Magellan-Baade

Cited by 92 publications

References 4 publications

Rapidly Evolving and Luminous Transients From Pan-Starrs1

Rapidly Evolving and Luminous Transients From Pan-Starrs1

TWENTY-ONE NEW LIGHT CURVES OF OGLE-TR-56b: NEW SYSTEM PARAMETERS AND LIMITS ON TIMING VARIATIONS

ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

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