Results from DROXO: IV. EXTraS discovery of an X-ray flare from the Class i protostar candidate ISO-Oph 85

Pizzocaro D, Stelzer B, Paladini R, Tiengo A, Lisini G, Novara G, Vianello G, Belfiore A, Marelli M, Salvetti D, Pillitteri I, Sciortino S, D'Agostino D, Haberl F, Watson M, Wilms J, Salvaterra R, De Luca A (2016)

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2016

Journal

Astronomy & Astrophysics EDP Sciences

Publisher: EDP Sciences

Book Volume: 587

Article Number: A36

DOI: 10.1051/0004-6361/201526562

Abstract

X-ray emission from young stellar objects (YSOs) is a key ingredient in understanding star formation. For the early, protostellar (Class I) phase, a very limited (and controversial) quantity of X-ray results is available to date. Within the EXTraS (Exploring the X-ray Transient and variable Sky) project, we have discovered transient X-ray emission from a source whose counterpart is ISO-Oph 85, a strongly embedded YSO in the ρ Ophiuchi star-forming region. We extract an X-ray light curve for the flaring state, and determine the spectral parameters for the flare from XMM-Newton/EPIC data with a method based upon quantile analysis. We combine photometry from infrared to millimeter wavelengths from the literature with mid-IR Spitzer and unpublished submm Herschel photometry that we analysed for this work, and we describe the resulting spectral energy distribution (SED) with a set of precomputed models. The X-ray flare of ISO-Oph 85 lasted ~2500 s and is consistent with a highly-absorbed one-component thermal model (N = 1.0 × 10 cm NH=1.0-0.5+1.2×1023cm-2 and kT= 1.15 keVkT=1.15-0.65+2.35 keV). The X-ray luminosity during the flare is log L [erg/s] = 31.1logLX [erg/s]=31.1-1.2+2.0; during quiescence we set an upper limit of log L [erg/s] < 29.5. We do not detect other flares from this source. The submillimeter fluxes suggest that the object is a Class I protostar. We caution, however, that the offset between the Herschel and optical/infrared position is larger than that for other YSOs in the region, leaving some doubt on this association. To the best of our knowledge, this is the first X-ray flare from a YSO that has been recognised as a candidate Class I protostar via the analysis of its complete SED, including the submm bands that are crucial for detecting the protostellar envelope. This work shows how the analysis of the whole SED is fundamental to the classification of YSOs, and how the X-ray source detection techniques we have developed can open a new era in time-resolved analysis of the X-ray emission from stars.

Authors with CRIS profile

Jörn Wilms Professur für Astronomie und Astrophysik

Involved external institutions

National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF) IT Italy (IT) California Institute of Technology (Caltech) US United States (USA) (US) National Institute for Nuclear Physics / Istituto Nazionale di Fisica Nucleare (INFN) IT Italy (IT) Istituto Universitario Di Studi Superiori Di Pavia IT Italy (IT) Stanford University US United States (USA) (US) Istituto di Matematica Applicata e Tecnologie Informatiche "Enrico Magenes" (IMATI) IT Italy (IT) Max-Planck-Institut für extraterrestrische Physik (MPE) / Max Planck Institute for Extraterrestrial Physics DE Germany (DE) University of Leicester GB United Kingdom (GB)

How to cite

APA:

Pizzocaro, D., Stelzer, B., Paladini, R., Tiengo, A., Lisini, G., Novara, G.,... De Luca, A. (2016). Results from DROXO: IV. EXTraS discovery of an X-ray flare from the Class i protostar candidate ISO-Oph 85. Astronomy & Astrophysics, 587. https://doi.org/10.1051/0004-6361/201526562

MLA:

Pizzocaro, D., et al. "Results from DROXO: IV. EXTraS discovery of an X-ray flare from the Class i protostar candidate ISO-Oph 85." Astronomy & Astrophysics 587 (2016).

BibTeX: Download