| Name | OT2_rvisser_1 |
| Title | Variability in high-J CO lines as a proxy for variable accretion in embedded protostars |
| URL | http://archives.esac.esa.int/hsa/whsa-tap-server/data?retrieval_type=OBSERVATION&observation_id=1342241492&instrument_name=PACS&product_level=LEVEL0&compress=true |
| DOI | https://doi.org/10.5270/esa-o0rgh97 |
| Author | visser, r. |
| Description | Embedded protostars are underluminous compared to model predictions of constant mass accretion rates from the envelope to the young star. This luminosity problem can be explained by episodic accretion: most of the mass is accreted in short bursts, so that most of the protostars are observed in a quiescient, low-luminosity state. The timescale between such accretion bursts is on the order of 10^4--10^5 yr. Smaller brightness variations (factors of at most a few) are seen on shorter timescales (days to years) in the more evolved T Tauri phase. Similar small-scale, short-period variations likely occur in the earlier embedded phases, but they are difficult to observe because of the high extinction through the envelope at UV to IR wavelengths. We propose a novel way of studying variable accretion in the embedded phase by obtaining a second epoch of Herschel-PACS data on rotationally excited CO lines in a sample of 21 previously observed embedded protostars. The high-J CO lines (upwards of 10-9) originate in UV- and shock-heated gas in the inner virgul1000 AU of the envelope. The UV field and the shock strength are both tied strongly to the accretion rate, so variability in the high-J CO line fluxes can be used as a proxy for variability in the accretion rate. A second epoch of data on the CO 14-13, 16-15, 24-23 and 30-29 lines will reveal to what extent embedded protostars show variable mass accretion rates on timescales of up to a few years. |
| Publication | |
| Instrument | PACS_PacsLineSpec_point |
| Temporal Coverage | 2012-03-15T21:27:56Z/2013-04-20T20:37:36Z |
| Version | SPG v14.2.0 |
| Mission Description | Herschel was launched on 14 May 2009! It is the fourth cornerstone mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities. |
| Creator Contact | https://support.cosmos.esa.int/h®erschel/ |
| Date Published | 2013-10-20T20:11:07Z |
| Keywords | Herschel, HSC, submillimetre, far-infrared, HIFI, PACS, SPIRE |
| Publisher And Registrant | European Space Agency |
| Credit Guidelines | European Space Agency, visser et al., 2013, 'Variability in high-J CO lines as a proxy for variable accretion in embedded protostars', SPG v14.2.0, European Space Agency, https://doi.org/10.5270/esa-o0rgh97 |