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TOPIC: V1647 Orionis


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Title: Dynamics during outburst: VLTI observations of the young eruptive star V1647 Ori during its 2003-2006 outburst
Authors: L. Mosoni, N. Sipos, P. Abraham, A. Moor, A. Kospal, Th. Henning, A. Juhasz, M. Kun, Ch. Leinert, S.P. Quanz, Th. Ratzka, A.A. Schegerer, R. van Boekel, S. Wolf

Context: It is hypothesized that low-mass young stellar objects undergo eruptive phases during their early evolution. The outburst of V1647 Ori between 2003 and 2006 offered a rare opportunity to investigate such an accretion event.
Aims: By means of our interferometry observing campaign during this outburst, supplemented by other observations, we investigate the temporal evolution of the inner circumstellar structure of V1647 Ori We also study the role of the changing extinction in the brightening of the object and separate it from the accretional brightening.
Methods: We observed V1647 Ori with MIDI/VLTI at two epochs in this outburst. First, during the slowly fading plateau phase (2005 March) and second, just before the rapid fading of the object (2005 September), which ended the outburst. We used the radiative transfer code MC3D to fit the interferometry data and the spectral energy distributions from five different epochs at different stages of the outburst. The comparison of these models allowed us to trace structural changes in the system on AU-scales. We also considered qualitative alternatives for the interpretation of our data.
Results: We found that the disk and the envelope are similar to those of non-eruptive young stars and that the accretion rate varied during the outburst. We also found evidence for the increase of the inner radii of the circumstellar disk and envelope at the beginning of the outburst. Furthermore, the change of the interferometric visibilities indicates structural changes in the circumstellar material. We test a few scenarios to interpret these data. We also speculate that the changes are caused by the fading of the central source, which is not immediately followed by the fading of the outer regions. However, if the delay in the fading of the disk is responsible for the changes seen in the MIDI data, the effect should be confirmed by dynamical modelling.

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Title: Suzaku Observation of Strong Fluorescent Iron Line Emission from the Young Stellar Object V1647 Ori during Its New X-ray Outburst
Authors: Kenji Hamaguchi, Nicolas Grosso, Joel H. Kastner, David A. Weintraub, Michael Richmond

The Suzaku X-ray satellite observed the young stellar object V1647 Ori on 2008 October 8 during the new mass accretion outburst reported in August 2008. During the 87 ksec observation with a net exposure of 40 ks, V1647 Ori showed a high level of X-ray emission with a gradual decrease in flux by a factor of 5 and then displayed an abrupt flux increase by an order of magnitude. Such enhanced X-ray variability was also seen in XMM-Newton observations in 2004 and 2005 during the 2003-2005 outburst, but has rarely been observed for other young stellar objects. The spectrum clearly displays emission from Helium-like iron, which is a signature of hot plasma (kT ~5 keV). It also shows a fluorescent iron Kalpha line with a remarkably large equivalent width of ~600 eV. Such a large equivalent width suggests that a part of the incident X-ray emission that irradiates the circumstellar material and/or the stellar surface is hidden from our line of sight. XMM-Newton spectra during the 2003-2005 outburst did not show a strong fluorescent iron Kalpha line, so that the structure of the circumstellar gas very close to the stellar core that absorbs and re-emits X-ray emission from the central object may have changed in between 2005 and 2008. This phenomenon may be related to changes in the infrared morphology of McNeil's nebula between 2004 and 2008.

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X-raying the beating heart of a newborn star

The violent behaviour of a young Sun-like star spinning at high speed and spewing out super-hot plasma has been revealed thanks to the combined X-ray vision of three space telescopes, including ESA's XMM-Newton.
Along with data from NASA's Chandra and Japan's Suzaku, the findings shed new light on one of the most fundamental issues in astronomy: the birth of stars like our own Sun.

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Title: The Continuing Outburst of V1647~Orionis: Winter/Spring 2011 Observations
Authors: Colin Aspin

We present optical and near-IR observations of the young eruptive variable star V1647 Orionis which illuminates McNeil's Nebula. In late 2003, V1647 Ori was observed to brightened by around 5 mag to r'=17.7. In early 2006 the star faded back to its quiescent brightness of r'~23, however, in mid-2008 it brightened yet again by ~5 mag. Our new observations, taken in early 2011, show V1647 Ori to be in an elevated photometric state with an optical brightness similar to the value found at the start of the 2003 and 2008 outbursts. Optical images taken between 2008 and 2011 suggest that the star has remained in outburst from mid 2008 to the present. H-alpha and the far-red CaII triplet lines remain in emission with H-alpha possessing a significant P Cygni profile. A self-consistent study of the accretion luminosity and rate using data taken in 2004, 2007, 2008, and 2011, indicates that when bright, V1647 Ori has values of 162 Lsun and 42x10^-6 Msun/yr, respectively. Although of low significance, we support the premise that both the accretion luminosity and rate declined by a factor 2-3 during the 5 mag fading in 2007. We discuss these new observations in relation to previous published data and the classification schemes for young eruptive variables.

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Title: Multi-Wavelength Study of the 2008-2009 Outburst of V1647 Ori
Authors: D. Garcia-Alvarez (1,2), N.J. Wright (3), J.J. Drake (3), P. Abraham (4), B.G. Anandarao (5), V. Kashyap (3), A. Kospal (6), M. Kun (4), M. Marengo (7), A. Moor (4), S. Peneva (8), E. Semkov (8), V. Venkat (5), J. Sanz-Forcada (9) ((1) IAC, Tenerife, Spain, (2) GRANTECAN, La Palma, Spain, (3) Harvard-Smithsonian CfA, MA, USA, (4) Konkoly Observarory, Budapest, Hungary, (5) Astronomy and Astrophysics Division, PLR, Ahmedabad, India, (6) Leiden University, Leiden, The Netherlands, (7) Department of Physics and Astronomy, Iowa State University, IA, USA, (8) Institute of Astronomy and National Astronomical Observatory Bulgarian Academy of Sciences, Sofia, Bulgaria, (9) Centro de Astrobiologia, CSIC-INTA, Spain)

V1647 Ori is a young eruptive variable star, illuminating a reflection nebula (McNeil's Nebula). It underwent an outburst in 2003 before fading back to its pre-outburst brightness in 2006. In 2008, V1647 Ori underwent a new outburst. The observed properties of the 2003-2006 event are different in several respects from both the EXor and FUor type outbursts, and suggest that this star might represent a new class of eruptive young stars, younger and more deeply embedded than EXors, and exhibiting variations on shorter time scales than FUors. In outburst, the star lights up the otherwise invisible McNeil's nebular - a conical cloud likely accumulated from previous outbursts. We present follow-up photometric as well as optical and near-IR spectroscopy of the nebula obtained during the 2008-2009 outburst. We will also present results from contemporaneous X-ray observations. These multi-wavelength observations of V1647 Ori, obtained at this key early stage of the outburst, provide a snapshot of the "lighting up" of the nebula, probe its evolution through the event, and enable comparison with the 2003-2006 outburst.

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Title: V1647 Orionis: Optical Photometric and Spectroscopic Monitoring Through the 2003-2006 Outburst
Authors: Colin Aspin, Bo Reipurth

We present results from an optical imaging and spectroscopic monitoring campaign on the young, low-mass eruptive variable star V1647 Orionis. The star and associated nebulosity (McNeil's Nebula) were observed over the period February 2004 to February 2006 with observations commencing a few months after the original outburst event occurred. Using the Gemini North telescope, we obtained multi-band optical imaging photometry and medium-resolution long-slit spectroscopy of V1647 Ori on an approximately monthly interval. During this period, V1647 Ori remained at, or close to, peak brightness and then faded by 5 magnitudes to close to its pre-outburst brightness. This implies an outburst timescale of around 27 months. Spectral features seen in both emission and absorption varied considerably during the monitoring period. For example, the Halpha line changed significantly in both intensity and profile. We present and discuss the observed photometric and spectroscopic changes and consider how this eruptive event relates to the early formative stages of low-mass stars.

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Title: V1647 Orionis: Reinvigorated Accretion and the Re-Appearance of McNeil's Nebula
Authors: Colin Aspin, Bo Reipurth, Tracy L. Beck, Greg Aldering, Ryan L. Doering, Heidi B. Hammel, David K. Lynch, Margaret Meixner, Emmanuel Pecontal, Ray W. Russell, Michael L. Sitko, Rollin C. Thomas, Vivian U

In late 2003, the young eruptive variable star V1647 Orionis optically brightened by over 5 magnitudes, stayed bright for around 26 months, and then decline to its pre-outburst level. In August 2008 the star was reported to have unexpectedly brightened yet again and we herein present the first detailed observations of this new outburst. Photometrically, the star is now as bright as it ever was following the 2003 eruption. Spectroscopically, a pronounced P Cygni profile is again seen in Halpha with an absorption trough extending to -700 km/s. In the near-infrared, the spectrum now possesses very weak CO overtone bandhead absorption in contrast to the strong bandhead emission seen soon after the 2003 event. Water vapour absorption is also much stronger than previously seen. We discuss the current outburst below and relate it to the earlier event.

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A new star appeared in the constellation of Orion in late 2003 when the young pre-main sequence star V1647 Orionis went into outburst. The eruption and huge increase in brightness of the object resulted in the appearance of a reflection nebula called McNeils Nebula, named after the amateur astronomer, Jay McNeil, who discovered the object and alerted the world.
During the outburst the star and nebula remained bright for approximately 18 months before fading rapidly over a six month period. By early 2006 the star and its environment were very similar to their pre-burst stage. The event was monitored and observed with many ground- and space-based facilities and Gemini Observatory played a key role in monitoring the event during its eruptive and quiescent phases. A team led by Colin Aspin (IfA/University of Hawaii), Tracy Beck (STScI) and Bo Reipurth (IfA/University of Hawaii) spearheaded the monitoring campaign of this unique event.

V1647ori
Two images of V1647 Orionis and McNeils Nebula. The image on the left is an optical color composite taken about four years ago with GMOS-North on UT 2004 February 14. The image on the right is also an optical colour image taken about one year ago on UT 2007 February 22.

Position (J2000): RA 05h 46m 13.10s | Dec -00 06' 05.00"


The eruption of V1647 Orionis is most likely associated with a mass dumping of the inner regions of a heated circumstellar disk onto the young stellar photosphere. The spectacular flaring in brightness of the object is due to a significant increase in accretion luminosity and the clearing or destroying of surrounding dust by an energetic wind that made the star visible. These eruptions are thought to be repetitive and indicative of periods when a significant fraction of the final stars mass is accreted.

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