4/21/21

 . Luh-man note that “Young brown dwarfs are brightest at near-infraredwavelengths (1-2 microns)”. Luhman note that photometric andcolor-magnitude analysis are excellent ways to select brown dwarfcandidates, but spectroscopic followup is required to confirm thesecandidates as actual brown dwarfs. Luhman note that the surfacetemperature of young low-mass stars and brown dwarfs remainsroughly constant as they contract down the Hayashi track of theHertzsprung-Russell Diagram; because of this constant temperatureas a function of age, the masses of young objects can be reliablyinferred from their effective temperature and/or spectral type. Luh-man further notes that gravity-sensitive spectroscopic features in thespectra of brown dwarfs can be an indicator of age.

4/20/21

 The identification and characterization of young brown dwarfs andvery low mass stars is discussed extensively in Luhman (2012)

4/19/21

Scholz & Jayawardhana (2006) presented the first dedicated spec-troscopic variability survey of young brown dwarfs, with six targetsover 11 nights. In this study, they demonstrated the variability of ac-cretion and outflow tracers such as the H훼emission line and others.

4.15.21

 . Gutermuth et al. (2009)performed aSpitzersurvey of Mon R2, identifying 235 young stel-lar objects associated with the Mon R2 region, of which 132 wereassociated directly with the Mon R2 cluster.

4/14/21

  The Mon R2 cluster’s age is estimated to be.1-3 Myr, asestimated via isochrone fitting by Carpenter et al. (1997); Andersenet al. (2006); a range of stellar ages appears to be present, possiblycorrelated with mass, such that the lowest-mass stars are less than1 Myr old.

4/12/21

 6.1 Comparison to other variability studies of brown dwarfsVos et al. (2019) studied the near-infrared variability of 30 relativelyyoung (∼10–200 Myr) low-gravity brown dwarfs, finding that browndwarfs of spectral type L0–L8.5 had a higher variability occurrence(∼30%) than older brown dwarfs in the field (∼11%). Vos et al.’sstudy made use of near-infrared monitoring at퐽,퐽푆and퐾푆bandswith the New Technology Telescope (NTT) of La Silla Observatoryin Chile, and UKIRT of Hawai‘i. Their search focused especially on
searching for low-amplitude, periodic variability, with a cadence of∼30 times per hour, time coverage of 2–6 hours, and photometricsensitivity of∼1%.

4/7/21

 Given some brown dwarfs and their associated light curves,what are we looking at when we want to decide whether the objectis “variable” or not? Some answers:(a) What “data quality class” is it in?(1) (How many of its datapoints are ‘good’ vs ‘info’ vs ‘warn’vs ‘severe’)?(b) Is the star “variable”?(1) What’s its Stetson index?(2) What’s its reduced chi-squared in each band?(3) Does the star show significant periodicity, according tothe Lomb-Scargle diagram?(c) Does the star show significantcolorvariability? (What arethe rchi2 values for its J-H and H-K colors? Is there periodicitydetectable in these “differenced” channels?)(d) If the star is variable, how would we classify its variability?Some possible answers:(1) nonvariable / flat (this is a “null hypothesis” answer)(2) rotators, including:(A) sinusoidal periodic, like a perfect rotator(B) differential rotator (sinusoidal with some drift in thephase and/or amplitude)(C) sinusoidal plus linear/secular drift(3) other periodic stars:(A) AA Tau / periodic disk dipper variables(B) eclipsing binaries of any sort (unlikely in our sample)(C) f95 types (including, like, the actual f95): periodicdisk brighteners(4) non-periodic variables:(A) short timescale, irregular accretion “bursty” activity(B) long timescale, changes in disk geometry(C) one-off “dipper” events(D) also, consider classifying this kind of variability byits color change behavior(E) sometimes we’ll see “compound color variability”,i.e. a star having clear “dust reddening” but then switch to“blueing disk geometry changes” and back, etc (as describedby Rice et al. (2015)).(5) other weird cases, which we can handle as they arise...

4/8/21

 TheONC’s age is estimated to be1−2Myr (Muench et al. 2008; Zariet al. 2017)

4/6/21 for real (yesterday's post should have said 4/5/21)

 This figure shows the퐾,퐻−퐾trajectory of all the brown dwarfsin NGC 1333 during our observing campaign.

4/6/21

 The Orion Nebula Cluster (discussed in detail in Muench et al. 2008),part of the Orion star-forming complex (discussed in detail in Bally2008), is the nearest region in which massive stars are being born

4/1/21

 The Mon R2 star cluster lies within its namesake, the Mon R2 reflec-tion nebula complex; a detailed review of the complex and its clusterare presented in Carpenter & Hodapp (2008)