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Mid-Infrared Variability of Protostars in IC 1396A

Morales-Calderón, M. and Stauffer, J. R. and Rebull, L. M. and Whitney, B. A. and Barrado y Navascués, D. and Ardila, D. R. and Song, I. and Brooke, T. Y. and Hartmann, L. and Calvet, N. (2009) Mid-Infrared Variability of Protostars in IC 1396A. Astrophysical Journal, 702 (2). pp. 1507-1529. ISSN 0004-637X.

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We have used Spitzer/Infrared Array Camera (IRAC) to conduct a photometric monitoring program of the IC1396A dark globule in order to study the mid-IR (3.6-8 μm) variability of the heavily embedded young stellar objects (YSOs) present in that area. We obtained light curves covering a 14 day timespan with a twice daily cadence for 69 YSOs, and continuous light curves with approximately 12 s cadence over 7 hr for 38 YSOs. Typical accuracies for our relative photometry were 1%-2% for the long timespan data and a few millimagnitude, corresponding to less than 0.5%, for the 7 hr continuous "staring-mode" data. More than half of the YSOs showed detectable variability, with amplitudes from ~0.05 mag to ~0.2 mag. About 30% of the YSOs showed quasi-sinusoidal light-curve shapes with apparent periods from 5 to 12 days and light-curve amplitudes approximately independent of wavelength over the IRAC bandpasses. We have constructed models which simulate the time-dependent spectral energy distributions of Class I and II YSOs in order to attempt to explain these light curves. Based on these models, the apparently periodic light curves are best explained by YSO models where one or two high-latitude photospheric spots heat the inner wall of the circumstellar disk, and where we view the disk at fairly large inclination angle. Disk inhomogeneities, such as increasing the height where the accretion funnel flows to the stellar hot spot, enhances the light-curve modulations. The other YSOs in our sample show a range of light-curve shapes, some of which are probably due to varying accretion rate or disk shadowing events. One star, IC1396A-47, shows a 3.5 hr periodic light curve; this object may be a PMS Delta Scuti star.

Item Type:Article
Related URLs:
URLURL TypeDescription
Stauffer, J. R.0000-0003-3595-7382
Rebull, L. M.0000-0001-6381-515X
Song, I.0000-0002-5815-7372
Hartmann, L.0000-0003-1430-8519
Calvet, N.0000-0002-3950-5386
Additional Information:© 2009 American Astronomical Society. Print publication: Issue 2 (2009 September 10); received 2008 October 30l; accepted for publication 2009 July 21; published 2009 August 21. This work is based [in part] on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This research has been funded by the NASA grant JPL101185-07.E.7991.020.6, and the Spanish grants MEC/ESP 2007-65475-C02-02, MEC/Consolider- CSD2006-0070, and CAM/PRICIT-S-0505/ESP/0361. M.M.C. acknowledges the support by a predoctoral “Calvo Rode´es” fellowship by INTA. Facilities: Spitzer (IRAC)
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
INTA (Instituto Nacional de Técnica Aeroespacial)UNSPECIFIED
Subject Keywords:infrared: stars; stars: pre-main sequence; stars: variables: other
Issue or Number:2
Record Number:CaltechAUTHORS:20090917-113626613
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Official Citation:Mid-Infrared Variability of Protostars in IC 1396A M. Morales-Calderón, J. R. Stauffer, L. Rebull, B. A. Whitney, D. Barrado y Navascués, D. R. Ardila, I. Song, T. Y. Brooke, L. Hartmann, and N. Calvet 2009 ApJ 702 1507-1529 doi: 10.1088/0004-637X/702/2/1507
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15909
Deposited By: Jason Perez
Deposited On:02 Oct 2009 21:35
Last Modified:03 Oct 2019 01:04

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