Exocomet Circumstellar Fe I Absorption in the Beta Pictoris Gas Disk

Welsh, Barry Y.; Montgomery, Sharon L.

doi:10.1088/1538-3873/128/964/064201

Cited by 30 publications

(12 citation statements)

References 14 publications

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“…The column density changes significantly, first showing a stable value on the order of 2.5 × 10 12 cm −2 lasting about seven years, followed by a 3.5σ drop down to about 1.8 × 10 12 cm −2 , lasting at least four years. This drop of about 30% in the Fe I total column density was noted from the same HARPS observations by Welsh & Montgomery (2016). It seems that the column density began increasing again.…”

Section: Variation Of the Fe I Ground Levelsupporting

confidence: 73%

“…(b) The b-value was fixed at the median value from past measurements, because Owens.f was unable to converge on a realistic value. VM17 (1300 K), leads to infer that the dropping component is located at close distance (∼38 R ) to the star and varies from a yet unknown process, perhaps exocomets activity drop, as proposed by Welsh & Montgomery (2016) and studied in further detail in Sect. 4.…”

Section: Revisiting the Ground Level Variations With A 2 Components Mmentioning

confidence: 90%

“…Independently, Welsh & Montgomery (2016) found that the ground level Fe I absorption lines in the same β Pic HARPS spectra were experiencing a strong drop of equivalent width between 2011 and 2013. They proposed that the source of the Fe I experiencing the drop is the "D-family" of exocomets identified in Kiefer et al (2014).…”

Section: Introductionmentioning

confidence: 96%

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Fe I in the β Pictoris circumstellar gas disk

Kiefer

Vidal‐Madjar

Étangs

et al. 2019

A&A

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The young planetary system β Pictoris is surrounded by a debris disk of dust and gas. The gas source of this disk could be exocomets (or “falling and evaporating bodies”, FEBs), which produce refractory elements (Mg, Ca, Fe) through sublimation of dust grains at several tens of stellar radii. Nearly 1700 high resolution spectra of β Pictoris were obtained between 2003 and 2017 using the HARPS spectrograph. In Paper I, we showed that a high signal to noise ratio allows the detection of many weak Fe I lines in more than ten excited levels, and we derived the physical characteristics of the iron gas in the disk. The measured temperature of the gas (~1300 K) suggests that it is produced by evaporation of grains at about 0.3 au (38 R⋆) from the star. Here, we describe the yearly variations of the column densities of all Fe I components (from both ground and excited levels). The drop in the Fe I ground level column density after 2011 coincides with a drop in Fe I excited levels column density, as well as in the Ca II doublet and a ground level Ca I line at the same epoch. All drops are compatible with photoionisation-recombination equilibrium and β Pic like relative abundances, in a medium at 1300 K and at 0.3 au from β Pictoris. Interestingly, this warm medium does not correlate with the numerous exocomets in the circumstellar environnement of this young star.

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Section: Variation Of the Fe I Ground Levelsupporting

confidence: 73%

Section: Revisiting the Ground Level Variations With A 2 Components Mmentioning

confidence: 90%

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Fe I in the β Pictoris circumstellar gas disk

Kiefer

Vidal‐Madjar

Étangs

et al. 2019

A&A

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“…This column density corresponds to an equivalent width of 7.1 mÅ for the 3860 Å line, which is consistent with the equivalent width measured by Welsh & Montgomery (2016). The variations in column density detected by Welsh & Montgomery (2016) do not affect the scientific conclusions derived here and will be discussed in a forthcoming paper (Kiefer et al, in prep. ).…”

Section: Circumstellar Gas In the Ground Base Fe I Linessupporting

confidence: 89%

Fe I in the β Pictoris circumstellar gas disk

Vidal‐Madjar

Kiefer

Étangs

et al. 2017

A&A

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The young planetary system β Pictoris is surrounded by a circumstellar disk of dust and gas. Because both dust and gas have a lifetime shorter than the system age, they need to be replenished continuously. The gas composition is partly known, but its location and its origin are still a puzzle. The gas source could be the exocomets (or so-called falling and evaporating bodies, FEBs), which are observed as transient features in absorption lines of refractory elements (Mg, Ca, and Fe) when they transit in front of the star at several tens of stellar radii. Nearly 1700 high-resolution spectra of β Pictoris have been obtained from 2003 to 2015 using the HARPS spectrograph. In these spectra, the circumstellar disk is always detected as a stable component among the numerous variable absorption signatures of transiting exocomets. Summing all the 1700 spectra allowed us to reach a signal-to-noise ratio higher than 1000, which is an unprecedentedly high number for a β Pictoris spectrum. It revealed many weak Fe I absorption lines of the circumstellar gas in more than ten excited states. These weak lines bring new information on the physical properties of the neutral iron gas in the circumstellar disk. The population of the first excited levels follows a Boltzmann distribution with a slope consistent with a gas temperature of about 1300 K; this temperature corresponds to a distance to the star of ~38 RStar and implies a turbulence of ξ ~ 0.8 km s-1.

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“…Rappaport et al 2018) as well as the spectral signatures of evaporating small, icy bodies (e.g. Welsh & Montgomery 2016). Other authors have investigated the fate of EX-OCs as stars evolve and proposed potentially detectable signatures associated stellar remnants (e.g.…”

Section: Introductionmentioning

confidence: 99%

Probing Oort Clouds around Milky Way Stars with CMB Surveys

Baxter

Blake

Jain

2018

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Long-period comets observed in our solar system are believed to originate from the Oort cloud, which is estimated to extend from roughly a few thousand to 10 5 AU from the Sun. Despite many theoretical arguments for its existence, no direct observations of the cloud have been reported. Here, we explore the possibility of measuring Oort clouds around other stars through their emission at submillimeter wavelengths. Observations with the 545 and 857 GHz bands of the Planck satellite are well matched to the expected temperatures of Oort cloud bodies (on the order of 10 K). By correlating the Planck maps with catalogs of stars observed by the Gaia mission, we are able to constrain interesting regions of the exo-Oort cloud parameter space, placing limits on the total mass and the minimum size of grains in the cloud. We compare our measurements with known debris disk systems -in the case of Vega and Fomalhaut we find a significant excess that is in agreement with measurements from Herschel. We use the measurements around Fomalhaut to constrain a possible exo-Oort cloud of that system. We explore an observed excess around the brightest and nearest stars in our sample as arising from possible exo-Oort clouds or other extended sources of thermal emission. We argue that future CMB surveys and targeted observations with far-infrared and millimeter wavelength telescopes have the potential to detect exo-Oort clouds or other extended sources of thermal emission beyond ∼ 1000 AU from the parent stars.

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Exocomet Circumstellar Fe I Absorption in the Beta Pictoris Gas Disk

Cited by 30 publications

References 14 publications

Fe I in the β Pictoris circumstellar gas disk

Fe I in the β Pictoris circumstellar gas disk

Fe I in the β Pictoris circumstellar gas disk

Probing Oort Clouds around Milky Way Stars with CMB Surveys

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