Michael L. Sitko
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View article: Refining the Migrating Differentiated Planetesimal Disruption Model for Classical T-Tauri Star RW Aur A’s Dimming Events
Refining the Migrating Differentiated Planetesimal Disruption Model for Classical T-Tauri Star RW Aur A’s Dimming Events Open
C. M. Lisse et al. (2022) published a near-infrared time domain spectral study of the dimming events in RW Aurigae A (RWAurA). Emission from the protostellar surface, protostellar atmosphere, accretion disk, and jets was reported, with the…
View article: Real-time Early Solar System Evolution in RW Auriga A: A New Major Dimming Event has Started in 2025 February
Real-time Early Solar System Evolution in RW Auriga A: A New Major Dimming Event has Started in 2025 February Open
In this Note1 we introduce the problem of the highly dynamic T Tauri system RWAurA, and, using new analyses of lightcurves and imaged jet structures, its potential for understanding early solar system formation processes. In the following …
View article: The Late Infrared Spectrum of the Very Slow Nova V5558 Sagittarii
The Late Infrared Spectrum of the Very Slow Nova V5558 Sagittarii Open
A 0.8–5.0 μ m spectrum of V5558 Sagittarii from 2013 September, more than six years after outburst, shows a still active nova emitting a rich coronal line spectrum. Lines exist for multiple ionization states of Al, S, Si, Ca, and Ti and co…
View article: SPHEREx Discovery of Strong Water Ice Absorption and an Extended Carbon Dioxide Coma in 3I/ATLAS
SPHEREx Discovery of Strong Water Ice Absorption and an Extended Carbon Dioxide Coma in 3I/ATLAS Open
In mid-August 2025, 0.75–5.0 μ m SPHEREx imaging spectrophotometric and ancillary NASA-IRTF/SpeX 0.7–2.5 μ m low-resolution spectral observations of 3I/ATLAS were obtained. The combined spectrophotometry is dominated by features due to wat…
View article: Sparse aperture masking interferometry survey of transitional discs: Search for substellar-mass companions and asymmetries in their parent discs
Sparse aperture masking interferometry survey of transitional discs: Search for substellar-mass companions and asymmetries in their parent discs Open
Context. Transitional discs are a class of circumstellar discs around young stars with extensive clearing of dusty material within their inner regions on 10s of au scales. One of the primary candidates for this kind of clearing is the form…
View article: Evidence for Ongoing Core Expulsion & Refractory Inclusion/Chondrule Formation in the RW Aurigae T-Tauri System
Evidence for Ongoing Core Expulsion & Refractory Inclusion/Chondrule Formation in the RW Aurigae T-Tauri System Open
The Earliest Solar System Materials and Solar System Formation. Sun-like TTauri stars (TTS) grow in their final stages via magnetically focused mass flows from a circumstellar accretion disk (CAD) [1-2; Fig.1]. The CAD is also the site of …
View article: Direct imaging discovery of a young giant planet orbiting on Solar System scales
Direct imaging discovery of a young giant planet orbiting on Solar System scales Open
HD 135344 AB is a young visual binary system that is best known for the protoplanetary disk around the secondary star. The circumstellar environment of the A0-type primary star, on the other hand, is already depleted. HD 135344 A is theref…
View article: Direct imaging discovery of a young giant planet orbiting on Solar System scales
Direct imaging discovery of a young giant planet orbiting on Solar System scales Open
Context . HD 135344 AB is a young visual binary system that is best known for the protoplanetary disk around the secondary star. The circumstellar environment of the A0-type primary star, on the other hand, is already depleted. HD 135344 A…
View article: The Early Infrared Spectrum of the Fe <scp>ii</scp> Nova V1310 Scorpii
The Early Infrared Spectrum of the Fe <span>ii</span> Nova V1310 Scorpii Open
V1310 Scorpii (Nova Scorpii 2010, No. 1) was an Fe ii -type nova whose early spectral properties are broadly representative of the class. We present a 0.8–5.2 μ m spectrum from 11 days after peak brightness that exhibit these properties. I…
View article: The Infrared Spectrum of the Stellar Merger V1309 Scorpii One Month After Outburst
The Infrared Spectrum of the Stellar Merger V1309 Scorpii One Month After Outburst Open
An infrared spectrum from 0.8 to 5.1 μ m is presented for the stellar merger V1309 Scorpii (Nova Scorpii 2008) from 32 days after discovery and 28 days after maximum light. The spectrum resembles a late-type M-supergiant in its overall sha…
View article: The Early Post-outburst Infrared Spectrum of the Stellar Merger V1309 Scorpii (Nova Scorpii 2008)
The Early Post-outburst Infrared Spectrum of the Stellar Merger V1309 Scorpii (Nova Scorpii 2008) Open
In this paper we present a 0.8–2.4 μ m spectrum of the stellar merger V1309 Scorpii (Nova Scorpii 2008). The spectrum was acquired within three days of discovery and a day before maximum light and has the appearance of a F supergiant. It i…
View article: Gas Dynamics in 3 “Dippers”: EPIC 203850058, EPIC 204638512, and EPIC 205151387 in 2017–2018
Gas Dynamics in 3 “Dippers”: EPIC 203850058, EPIC 204638512, and EPIC 205151387 in 2017–2018 Open
We have examined variability of the three dipper stars—EPIC 203850058, EPIC 204638512, and EPIC 205151387—using the SpeX spectrograph on NASA’s Infrared Telescope facility on two nights in 2018. We combined these data with those previously…
View article: SCExAO/CHARIS Near-infrared Scattered-light Imaging and Integral Field Spectropolarimetry of the AB Aurigae Protoplanetary System
SCExAO/CHARIS Near-infrared Scattered-light Imaging and Integral Field Spectropolarimetry of the AB Aurigae Protoplanetary System Open
We analyze near-infrared integral field spectropolarimetry of the AB Aurigae protoplanetary disk and protoplanet (AB Aur b), obtained with SCExAO/CHARIS in 22 wavelength channels covering the J , H , and K passbands ( λ 0 = 1.1–2.4 μ m) ov…
View article: SCExAO/CHARIS Near-Infrared Scattered-Light Imaging and Integral Field Spectropolarimetry of the AB Aurigae Protoplanetary System
SCExAO/CHARIS Near-Infrared Scattered-Light Imaging and Integral Field Spectropolarimetry of the AB Aurigae Protoplanetary System Open
We analyze near-infrared integral field spectropolarimetry of the AB Aurigae protoplanetary disk and protoplanet (AB Aur b), obtained with SCExAO/CHARIS in 22 wavelength channels covering the J, H, and K passbands ($λ_{\rm o}$ = 1.1--2.4 $…
View article: Gas Dynamics in the Herbig Ae Star HD 163296 in 2024
Gas Dynamics in the Herbig Ae Star HD 163296 in 2024 Open
We observed the Herbig Ae star HD 163296 over 9 nights in 2024. On 4 of the nights, the He i line at 1.083 μ m exhibited a profile rarely seen in the star. Rather than the typical P Cygni profile indicating a net gas outflow, the profile c…
View article: The Coronal Lines of the High-excitation, Fe ii-type Nova V2467 Cygni
The Coronal Lines of the High-excitation, Fe ii-type Nova V2467 Cygni Open
Optical and infrared spectra are presented for the nova V2467 Cygni from the period of its maximum excitation. The spectra indicate exceptionally high excitation for a Fe ii -type nova, exhibiting [Si x ] 1.4305 μ m and several emission li…
View article: Dracula’s Chivito: Discovery of a Large Edge-on Protoplanetary Disk with Pan-STARRS
Dracula’s Chivito: Discovery of a Large Edge-on Protoplanetary Disk with Pan-STARRS Open
We report the serendipitous discovery of a large edge-on protoplanetary disk in Pan-STARRS (PS1) images. PS1 has five broadband filters designated as g P1 , r P1 , i P1 , z P1 , and y P1 with mean wavelengths 4866, 6215, 7545, 8679, and 96…
View article: JWST/NIRCam Imaging of Young Stellar Objects. I. Constraints on Planets Exterior to the Spiral Disk Around MWC 758
JWST/NIRCam Imaging of Young Stellar Objects. I. Constraints on Planets Exterior to the Spiral Disk Around MWC 758 Open
MWC 758 is a young star hosting a spiral protoplanetary disk. The spirals are likely companion-driven, and two previously identified candidate companions have been identified—one at the end the Southern spiral arm at ∼0.″6, and one interio…
View article: CO and C i Emission in the Early Spectrum of the Nova V1391 Cassiopeiae
CO and C i Emission in the Early Spectrum of the Nova V1391 Cassiopeiae Open
V1391 Cassiopeiae is one of a growing number of novae to show emission from carbon monoxide but only the second to display molecular absorption as well (after V2676 Ophiuchi). In this Research Note, we present a 0.69–5.2 μ m spectrum that …
View article: Dracula's Chivito: discovery of a large edge-on protoplanetary disk with Pan-STARRS
Dracula's Chivito: discovery of a large edge-on protoplanetary disk with Pan-STARRS Open
We report the serendipitous discovery of a large edge-on protoplanetary disk associated with the infrared source IRAS 23077+6707. The disk's apparent size in the Pan-STARRS (PS1) images is ~11", making this one of the largest known disks o…
View article: JWST/NIRCam Imaging of Young Stellar Objects. I. Constraints on Planets Exterior to The Spiral Disk Around MWC 758
JWST/NIRCam Imaging of Young Stellar Objects. I. Constraints on Planets Exterior to The Spiral Disk Around MWC 758 Open
MWC 758 is a young star hosting a spiral protoplanetary disk. The spirals are likely companion-driven, and two previously-identified candidate companions have been identified -- one at the end the Southern spiral arm at ~0.6 arcsec, and on…
View article: CO and Atomic Line Emission from the Young Stellar Object V1331 Cygni
CO and Atomic Line Emission from the Young Stellar Object V1331 Cygni Open
The infrared spectrum of the young disk star V1331 Cygni shows rare atomic emission lines from several species including C i , O i , Na i , Mg i , Al i , Si i , Ca i , Fe i , and probably S i . The presence of H i emission but the absence …
View article: Searching for low-mass companions at small separations in transition disks with aperture masking interferometry
Searching for low-mass companions at small separations in transition disks with aperture masking interferometry Open
Transition disks have large central cavities that have been spatially resolved during recent years. Cavities and other substructures in circumstellar disks are often interpreted as signposts to massive companions. We aim to search for stel…
View article: Searching for low-mass companions at small separations in transition disks with aperture masking interferometry
Searching for low-mass companions at small separations in transition disks with aperture masking interferometry Open
Context . Transition disks have large central cavities that have been resolved by imaging surveys during recent years. Cavities and other substructures in circumstellar disks are often interpreted as signposts to massive companions. Detect…
View article: The disk of the eruptive protostar V900 Mon
The disk of the eruptive protostar V900 Mon Open
Aims. In this work, we study the silicate dust content in the disk of one of the youngest eruptive stars, V900 Mon, at the highest angular resolution, probing down to the inner 10 au of said disk, and study the historical evolution of the …
View article: The disk of the eruptive protostar V900 Mon; a MATISSE/VLTI and MUSE/VLT perspective
The disk of the eruptive protostar V900 Mon; a MATISSE/VLTI and MUSE/VLT perspective Open
In this work, we study the silicate dust content in the disk of one of the youngest eruptive stars, V900 Mon, at the highest angular resolution probing down to the inner 10 au of said disk, and study the historical evolution of the system …
View article: CO Fundamental and First Overtone Emission in the Nova V496 Scuti
CO Fundamental and First Overtone Emission in the Nova V496 Scuti Open
Simultaneous spectroscopic observations of the carbon monoxide (CO) fundamental and first overtone emission are presented for the nova V496 Scuti. Total emission is comparable in the two features, indicating that optically thick conditions…
View article: Modeling the Multiwavelength Evolution of the V960 Mon System
Modeling the Multiwavelength Evolution of the V960 Mon System Open
We study the evolution of the FU Ori object V960 Mon since its outburst, using available multiwavelength photometric time series over 8 yr, complemented by several epochs of moderate-dispersion spectrophotometry. We find that the source fa…
View article: Optical and Near-infrared Atmospheric Extinction Coefficients at La Silla
Optical and Near-infrared Atmospheric Extinction Coefficients at La Silla Open
We used observations obtained at the Rapid Eye Mount (REM) at the La Silla Observatory between 2016 June 7 UT to determine the extinction coefficients of the REM filters currently in use. The observations were obtain on 6 nights, spanning …
View article: Direct images and spectroscopy of a giant protoplanet driving spiral arms in MWC 758
Direct images and spectroscopy of a giant protoplanet driving spiral arms in MWC 758 Open
Understanding the driving forces behind spiral arms in protoplanetary disks remains a challenge due to the faintness of young giant planets. MWC 758 hosts such a protoplanetary disk with a two-armed spiral pattern that is suggested to be d…