spitzer 40 day monitoring of the onc sept 12, 2011 john r. stauffer, ipac

12 Sept 2011 JRS-1STScI – Orion Treasury program group meeting

Spitzer 40 day Monitoring of the ONC

Sept 12, 2011John R. Stauffer, IPAC


Outline of Talk• I will briefly describe the Orion monitoring campaign

conducted in 2009, and one specific connection to the HST Orion project.

• I will even more briefly describe the next major effort – a 30 day Spitzer/CoRoT/MOST campaign for NGC2264.


YSOVAR – Orion; Staufferet al, Cycle 6 ES Program

• The central 1 sq. degree of the Orion Nebula Cluster was observed for 38 consecutive days

• Twice per day cadence; ~250 total observing hours• Almost 2000 YSOs with Spitzer light curves• Concurrent optical and JHK monitoring from more

than a dozen ground-based telescopes• Some additional monitoring in 2010 and 2011 to

provide longer timescale data• Goal: to understand better the physical mechanisms

causing YSO variability by (for the first time) providing data sensitive to warm dust in the inner disk



Blue dot: 3.6 mu; open circle: 4.5 mu; green dot: J band; red dot: I (or K) band



Blue dot: 3.6 mu; open circle: 4.5 mu; green dot: J band; red dot: I (or K) band

The preceding view graph werethe poster children – but theseare more typical – examples ofthe “irregular variable” class.


YSOVAR – OrionExecutive Summary

• For the ~1200 YSOs with disks for which we acquired good monitoring data– About 70% were detectably variable at IRAC wavelengths– Only about 15% were periodic – the great majority were

variable but “irregular”, at least in December 2009– Less than 5% of our sample were classifiable as AA Tau’s –

much less than the fraction in N2264 from CoRoT. Not obvious that this is all explainable by the different observing cadence and wavelength coverage.

– Even among the AA Tau class, only a small fraction showed periodic flux dips (discernible with our 40 day window)

– Our cadence was good for finding PMS eclipsing binaries.


ORION ECLIPSING BINARIESWe have recovered the 4 known PMS EBs in the ONC:

First brown dwarf eclipsing binary0.057 M+ 0.036 M

0.67 R+ 0.51 R

T2/T1 ≈ 1.05(Stassun, Mathieu & Valenti 2006)

Double-lined, spectroscopic, eclipsing binary.

1.01 M+ 0.73 M

1.3 R+ 1.1 R

(Stassun et al. 2004)

Low mass, double-lined, spectroscopic, eclipsing binary

0.41 M+ 0.41 M

1.75 R+ 1.75 R

(Cargile et al. 2008)

2MASSJ05352184-0546085 P = 9.78 d V1174 Ori P = 2.63 d Par 1802 P = 4.67 d

JW 386 P = 5.30 d

Very low mass eclipsing binary0.26 M+ 0.15 M

1.19 R+ 0.9 R

(Irwin et al. 2007)


ORION ECLIPSING BINARIESand found 7 new candidates…

Spectroscopic binaryTwo mid-G giants(Herbig & Griffin 2006)

Staring Mode

M1 ~ M2 ~ 2.5 M

M1 = 0.83 M

M2 = 0.05 M

i = 88.2 deg

Primary SpTy: K0 -> T1 = 5150 K T2 = 3000 KR1 + R2 = 3.75 R


We are working to obtain spectroscopic confirmation. If confirmed, they double the number of known low mass eclipsing binaries in the area

ORION ECLIPSING BINARIES

The longest period PMS EB to date M4.5

K7-M0

The lowest mass PMS EB to date

Only candidate presenting midIR excess consistent with having a disk

Previously identified as a fast rotator with P=0.27 d


Thoughts re: Orion Age Spread

• Reggiani et al. used the HST Treasury data to estimate the existing data (estimates of L/Teff) are inconsistent with coeval star formation, but consistent with an age spread of about 2 Myr (and a mean age of about 2.2 Myr).

• Jeffries et al used the same L, Teff data but used disk presence as a pseudo clock. Their conclusion was that there was no evidence for an age spread, and that for a mean age of 2.5 Myr, >95% of the stars should have ages between 1.3 and 4.8 Myr.

• The conclusions are not that different, given the uncertainties.



• YSOVAR can contribute to this by identifying a set of what should be the youngest YSOs in Orion, based on their variability characteristics.

• After doing this, the location of these stars in an HR diagram is essentially the same as for Orion WTTs or for full set of stars with disks.

• This also suggests that the main cause for the spread in the HR diagram is something other than age.



This plot shows all of the starsfrom Da Rio 2010, using the L and Teff from that paper, andwhich are included in the YSOVAR sample. “Disk” means having an IR excessaccording to Megeath’s IRACGTO program.

No obvious separation of thetwo – as per Jeffries paper.



This version only includes themost “active” disks based on their IR variability (largestamplitude and/or shape differentat I/J vs. IRAC).

Still no significant difference inthe HR diagram location compared to the WTT’s.


YSOVAR Orion and HST Treasury

• There must be other ways to combine the Spitzer and HST data:– Use the HST U-band or the ground-data obtained in support

of the treasury program to estimate accretion rates (or just use the values in Da Rio 2010)– and “assume” that these stars should have variability that is dominated by accretion. Compare the variability characteristics of these stars to those of the AA Tau class, where the dominant events are due to extinction.

– Do the HST-identified visual binaries have different variability characteristics from those that are single at HST resolution?

– Other?


YSOVAR2 – Mapping YSO Inner Disk Structure in NGC2264

• Simultaneous Spitzer, CoRoT and MOST imaging photometry of this 1-3 Myr old cluster for 30 days, continuous

• The only star forming region that can be observed by CoRoT

• >100 YSOs with IRAC staring mode data for ~5 days – mmag photometry with 30sec cadence at V and IRAC

• 300ksec of Chandra time – hope to have this done simultaneously with the IRAC staring mode data

• December 2011.


YSOVAR2 – More Details

• Spitzer - scheduled for Dec. 3, 2011 to Jan. 1, 2012 (5 days staring; 25 days mapping – 13 times per day)

• CoRoT – plan for same window, or slightly longer• MOST – scheduled for Dec. 5, 2011 to Jan. 12, 2012• Chandra – likely in Dec. 4-11, 2011 window• VLT/FLAMES (Halpha) – 40 hrs (2 hr/nt for ~17 nights)• CFHT Megacam U band –Dec. 16-29• KPNO 2.1m Flamingos JHK – Dec. 13-23• MMT Hectoechelle – Dec. 13-15• CAHA 3.5m Omega2000 JHK – once/nt for 30 nts• Other smaller telescopes, mostly I band.


YSOVAR2 – More Details

• CoRoT – will get data for ~300 cluster members with 10 < R < 16, at 512 or 32 second cadence.

• MOST - will get data for ~70 cluster members at about twice per minute cadence, V <~ 12.

• Spitzer – data for most of the cluster - > 600 members at about 1.7 hr cadence. Good photometry down to HBML.


YSOVAR2 – Science Goals

• By combining UVRIJHK+IRAC time series photometry plus Halpha monitoring, finally be able to separate primary causes of YSO variability (extinction, accretion, hot/cold spots on the photosphere, etc.)

• Specifically, attempt to create detailed models for the AA Tau analogs found with the 1st NGC2264 CoRoT “short-run” by Alencar et al. Is the frequency of AA Tau type variables really very different in N2264 and Orion?

• PMS EB census for a cluster that is on average older than the ONC.


YSOVAR2 – Wish List

• At some level, this campaign is a “once in a lifetime” event since it uses three space observatories that will soon stop taking data, with little in the way of the same capability coming on line any time soon.

• This makes it important to try to do this right – and to try to collect as many types of relevant data as possible during the December campaign.

• We welcome volunteers…


BACKUP SLIDES


Combining YSOVAR and HST

DaRio Log(Lacc/Lbol) vs. Range inIRAC [3.6] forIrreg. variables w.IR excesses.

spitzer 40 day monitoring of the onc sept 12, 2011 john r. stauffer, ipac

Documents