Stellar variability in IC 348 YETI Observations

Dario Fritzewski Leibniz Institut für Astrophysik Potsdam (AIP)

19 October 2018

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 1/24 Outline

1 The IC 348

2 Observations and Time Series Analysis

3 Results

4 What we have learned

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 2/24 (AIU/M.Mugrauer)

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 3/24 Basic Facts on IC 348

§ Located in the molecular cloud (03h 44m 34s, `320 091 45”)

§ Median age between 2 Myr and 6 Myr (Luhman+ 2003, Bell+ 2013)

§ « 470 members including several brown dwarfs (Luhman+ 2016)

§ Distance: 316 pc (Herbig 1998) § Several photometric surveys in the literature.

(Herbig 1998, Cohen+ 2004, Littlefair+ 2005, Nordhagen+ 2006)

§ 143 are periodically variable or candidates (Cieza & Baliber,

2006)

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 4/24 § Selection based on proper motion § Refine cluster membership based on parallax. § recovers 220 members from Luhman+ (2016)

Colour-Magnitude-Diagram of IC 348

§ CMD from Gaia DR2

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 5/24 § Refine cluster membership based on parallax. § recovers 220 members from Luhman+ (2016)

Colour-Magnitude-Diagram of IC 348

§ CMD from Gaia DR2 § Selection based on proper motion

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 5/24 Colour-Magnitude-Diagram of IC 348

§ CMD from Gaia DR2 § Selection based on proper motion § Refine cluster membership based on parallax. § recovers 220 members from Luhman+ (2016)

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 5/24 Observations and Data Analysis

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 6/24 The Observations in Numbers

§ 2.4 year timebase § 17 846 frames obtained § 8 involved observatories § 10 808 frames from Jena § 125 nights of observations § 1001 stars in the field of view analysed

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 7/24 The Advantage of YETI

§ Better phase coverage for any given period § Advantage for periods that are multiple of 1 d Ñ reducing alias

100 YETI 80 Only Jena Deviation 60

40

20

Phase coverage [%] 0 0 50 100 150 200 250 300 Period [d]

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 8/24 The Advantage of YETI

§ Better phase coverage for any given period § Advantage for periods that are multiple of 1 d Ñ reducing alias

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 8/24 Time-Series Analysis

Three methods were deployed

§ Generalised Lomb-Scargle periodogram (Zechmeister & Kürster 2009)

§ Gregory-Loredo Bayesian periodogram (Gregory & Loredo 1992)

§ String-length algorithm (Dworetsky 1982)

Common properties of the methods § Work on arbitrary spaced data § Use predefined trial periods

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 9/24 Workflow of Period Determination

1 Independent application of methods to light curve (LC) 2 Two of three should give same period within 10% margin 3 Search within 10% range with finer grid 4 Agreement on 1% level Ñ Accept period after manual inspection of LC.

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 10/24 Results

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 11/24 Stellar Rotation of PMS stars

§ Rotational variability observable due to spots. § Young stars have large spots Ñ easier to detect § Found 87 periodic stars in IC 348, including 33 new § Well studied cluster, finding new periods still possible

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 12/24 Comparison with Previous Work

20 § Comparison with prior work of Cieza & Baliber (2006) shows:

15 § Most previously found periods have a ratio of 1:1, 10 1:2, or 2:1 § few periods diverge without Period (CB06) [d] Period 5 a proper reason § 24 periods could not have be recovered 0

0 5 10 15 20 Period (this work) [d]

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 13/24 Bimodal Period Distribution in IC 348

§ Stars in young OC are either

0.15 fast or slow rotators

§ Discovered in ONC (Herbst 2000) § Bimodel distribution with 0.10 Prot « 2 d and Prot « 8 d

Relative Frequency Relative § Two populations due to

0.05 accretion history (Meibom+ 2013) § Not statistically significant in our data 0.00 0 5 10 15 Period [d]

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 14/24 V695 Per – An AA Tauri System

§ Magnetic interactions of the disc’s inner edge with the star § Inner edge of the proto-planetary disc is warped § Periodic occultation of the star (P “ 7.55 d, orbital period)

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 15/24 V909 Per – An UX Orionis System

§ Clumps in proto-planetary disc occult the star § Different clump sizes Ñ varying shape and depth § Fading of 0.6 mag in a few days

§ Two other stars in IC 348 show this behaviour (Barsunova+ 2013)

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 16/24 V718 Per – An Unusual System

§ Long-lasting eclipse of 3.5 yr (Nordhagen+ 2006)

§ ”Stable, extended, dusty structure“ (Grinin+ 2008) § Period: 4.7 yr Ñ eclipse lasts for 75 % of a cycle

1.0

1.2

1.4

1.6

1.8

2.0 instrumental R magnitude [mag] 2.2

200 400 600 800 1000 JD [d] +2.456e6

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 17/24 Non-periodic Variability

∆m « 1.2 mag τ 1 « 8.4 min 2

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 18/24 Variability Among the Field Stars – Periodic Variability is not Limited to Open Cluster –

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 19/24 W UMa Binaries and Other Variables

star 213 P =0.43 d star 777 P =0.49 d § Four contact binaries in the field identified § All have a similar period

R Magnitude and are background stars

star 974 Phase P =0.42 d star 975 Phase P =0.45 d R Magnitude

0 0.5 1.0 1.5 0 0.5 1.0 1.5 Phase Phase

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 20/24 § Gaia confirms those stars as possible members.

Additional members of IC 348

§ Some field stars show fast rotation (P ă 10 d). § May be additional members of IC 348.

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 21/24 Additional members of IC 348

§ Some field stars show fast rotation (P ă 10 d). § May be additional members of IC 348. § Gaia confirms those stars as possible members.

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 21/24 A Visual Summary

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 22/24 Conclusion

§ YETI improves the phase coverage for all periods. § 87 periodic stars in IC 348 identified (33 new). § Wide range of photometric variable objects detected. § Rotation periods can identify member candidates.

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 23/24 Thank You for Your Attention!

Stellar variability in IC 348 Dario Fritzewski-19 October 2018 24/24