Stellar radio emission in the SKA era: the SCORPIO project

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1 Stellar radio emission in the SKA era: Grazia Umana the SCORPIO project INAF-OAC C. Trigilio, R. Norris, T. Franzen, A. Ingallinera, C. Agliozzo P. Leto, C. Buemi, E. Budding, B. Slee, G. Ramsay, G. Doyle, M. Thompson, J.C. Guirado, S. Keller, J.D. Bunton, J. Lazio, F. Leone, G. Hallinan, M. Johnston-Hollit, G. Hobbs, M. Mao

2 Stellar radio emission HR diagram for the 420 radio detected stars (Gudel, 2002) -L radio a small (10-12 Sun) fraction of L tot Radio probes astrophysical phenomena non detectable by other means: -B and its topology in flares stars, RS CVn -HII region in dust enshrouded sources - Winds-winds interactions. Important for: -Stellar evolution -Physical processes in a wider context.

3 Stellar radio emission The brightest stellar radio emission associated with: -Large mass-loss (large emitting surface): free-free from stellar winds (OB, WR) S ν ν α α= Solar-type, non-thermal phenomena (high T B ): gyrosynchrotron, related to a strong and (often) variable stellar B Variable Gyro-synchrotron (Active stars and stellar systems): quiescent periods -slowly varying flux density, up to several mjy active periods -series of strong outburst, up to 1Jy

4 Active binary systems Active periods can last several months Noto 6cm monitoring- 23 days/ up to 12 hrs coverage Both quiescent and active periods are Related to solar-type magnetic activity (observed also in other spectral ranges) Radio flares in large magnetic structures (loops); in binaries could be intersystem: Algol (Mutel et al., 2009)

5 Stellar radio emission Coherents events (usually observed in addition to gyrosynchrotron) Modelled as electron cyclotron maser emission (ECME) Astrophysical environments common ingredient strong B and energetic particles Active stars and stellar systems (Osten et al., 2004; Slee et al., ) Ultra Cool Dwarf (Hallinan et al., 2008) CPs stars (Trigilio et al., 2000; Trigilio et al., 2008, 2011) General Characteristics See Trigilio talk.. Polarization up to 100% Frequency structure Narrow bandwidth Short duration (time) Usually observed at low-freq < 2.5 GHz.

6 Active binary systems HR GHz GHz Δt 2-3 hrs ATCA Slee et al., 2008

7 -Both incoherent (gyro-syncrotron) and coherent emission Late M TVLM M9 RCP VLA, X,C simultaneous -2 epochs, 10 hrs each -folded with P= 1.96 hrs Stable magnetic structure? LCP Hallinan et al., 2006, Berger et al., 2009 McLean et al., 2011

8 The actual knowledge of stellar radio emission suffers of: -limited sensitivity: Stellar radio emission -selection bias: No radio star with radio luminosity similar to the quiescent Sun (L 6cm erg/sec Hz) detected yet. based on targeted observations aimed at addressing a specific astrophysical problem However, starting from some information on radio luminosity Flares stars (and late-m) Seaquist, 1993; Gudel 2002; Berger et al PMS Gudel, 2002 Active binary systems Moris and Mutel, 1988, Umana et al., 1993 OB-WR Seaquist, 1993; Bieging et al., 1989 CP Leone et al., 1992; Trigilio et al., 1994

9 We can build a stellar radio emission forecast Assumed distances are: 10pc flare stars, 100pc RS and PMS, 500pc CP, 1kpc OB and SG Schematic radio continuum spectrum of several classes of radio emitting stars

10 Stellar radio emission forecast With a limiting flux of 30 μjy: flare stars (q) detected up to 20pc, RS (q) up to 500pc PMS, CP and WR/OB at more than 1kpc

11 Stellar radio emission forecast Key question: How many stars, at sub-mjy level, we can expect to detect in one square degree of sky? Not obvious answer 1) the presence of stars belonging to classes thought to be radio emitter is a necessary but not sufficient condition to detect them. Need sufficient B and Nrel (non-therm) or mass-loss rate and UV field (therm) detection rate: OB 20%, CP 25%, 30-40% RS 2) Distance plays a role 3) Non-thermal radio emission is variable Can large field radio survey help? NVSS, too shallow and low angular resolution for stellar work FIRST, ATLAS, designed for extragalactic High Galactic Latitude

12 A deep radio survey with the ATCA The SCORPIO Project -same observing strategy as ATLAS -in a sky patch well suited for stellar work, i.e. low Galactic latitude Expected outcomes- Science - Enlarge the stellar radio emitting population, with no selection bias - Better comprehension of physics and plasma processes - Establish how common are coherent events among stellar sources.

13 The SCORPIO Project Expected outcomes- Planning the EMU project Results from SCORPIO will guide EMU in the following areas: - Dynamic range from sources complexity: issues related to complex, extended structure in the GP - Dynamic range from source variability: issues related to the presence of variability in most of non-therm sources - Source extractions: what is the most appropriate method for sources embedded in the diffuse emission in the GP

14 The selected field: requirements Close to the galactic Plane (GP) but not only in the GP: extended emission could be a severe issue A sufficient number of stars, good spread in classes of radio emitting object Few radio sources already detected in it: to be used as check Multi-λ observations available for comparative studies.

15 The selected field In the tail of SCORPIO

16 The selected field 2 x 2 deg 2 IC 4628 L=343.5 B=1.0 SCORPIO OB1 NGC 6231

17 The selected field 2 x 2 deg2 IC 4628 SCORPIO OB1 L=343.5 B=1.0 NGC 6231

18 Quering SIMBAD. The selected field Stars: WR, Delta Scu Algols, Var, Double Em Line

19 The selected field Part of sky patch has been surveyed by: Spitzer (Benjamin et al., 2003, Carey et al., 2009) HERSCHEL (Hi-GAL, Molinari et al., 2010) And will be observed in: CORNISH-S (PI: Hoare) MeerKAT GP survey (PI: Thompson)

20 The pilot experiment 0.5 x 2 deg 2, l=344, b=0.66 Observed in mosaic mode with ATCA 38 pointings, 8.8 arcmin spacing hexagonal grid Duty cycle=1min/pointing +cal total integration time/pointing 1hr Total observing time= 48hrs (4 days) C2515 6A Δν= GHz CABB: 2048 chs, 1 MHz each HPBW of the ATCA antennas centered on the pointing pos.

21 The pilot experiment: Searching for the best strategy RFI a nightmare! -help from mirflag but should used with some preacutions -Need to take care for SEDs of sources within the bandpass - Data flagging and calibration performed in MIRIAD - Map making: in its VERY VERY early phase. - MOSAIC: individual approach (MIRIAD)? or direct (CASA)?

22 The pilot experiment 1 pointing, 300 MHz (2 GHz) mfs rms 90 μjy -About 50 islands found by imsad (>5 rms) -no matchs with NED - 5 matchs with SIMBAD (search radius 10 )

23 The pilot experiment FOV 20 x 15 1 pointing, 300 MHz (2 GHz) mfs rms 90 μjy Evident side-lobes Need checks for calibrations errors And/or RFI effects left No selfcal

24 The pilot experiment Use of the large bandpass to get spectral information FOV 1 x 0.5 Sub-mosaic (7 pointing) CASA, mfs Bandpass in 3, 300 MHz sub-bands 1.5 GHz, rms=140μjy, B=11.5 x GHz, rms=140μjy, B=8.9 x GHz, rms=100μjy, B=6.7 x 3.7