Probing intermediate-mass black holes with optical emission lines from tidally disrupted white dwarfs

Drew Clausen, Michael Eracleous

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

We calculate the emission-line spectrum produced by the debris released when a white dwarf (WD) is tidally disrupted by an intermediate-mass black hole (IMBH; M ∼ 102-105 M) and we explore the possibility of using the emission lines to identify such events and constrain the properties of the IMBH. To this end, we adopt and adapt the techniques developed by Strubbe & Quataert to study the optical emission lines produced when a main-sequence star is tidally disrupted by a supermassive black hole (BH). WDs are tidally disrupted outside of the event horizon of a <105 M BH, which makes these tidal disruption events good signposts of IMBHs. We focus on the optical and UV emission lines produced when the accretion flare photoionizes the stream of debris that remains unbound during the disruption. We find that the spectrum is dominated by lines due to ions of C and O, the strongest of which are Civ λ1549 at early times and [Oiii] λ5007 at later times. Furthermore, we model the profile of the emission lines in the [O iii] λλ4959, 5007 doublet and find that it is highly asymmetric with velocity widths of up to ∼2500 km s -1, depending on the properties of the WD-IMBH system and the orientation of the observer. Finally, we compare the models with observations of X-ray flares and optical emission lines in the cores of globular clusters and propose how future observations can test if these features are due to a WD that has been tidally disrupted by an IMBH.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume726
Issue number1
DOIs
StatePublished - Jan 1 2011

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light emission
debris
flares
event horizon
main sequence stars
globular clusters
line spectra
emission spectra
profiles
accretion
ions
x rays
ion

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

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title = "Probing intermediate-mass black holes with optical emission lines from tidally disrupted white dwarfs",
abstract = "We calculate the emission-line spectrum produced by the debris released when a white dwarf (WD) is tidally disrupted by an intermediate-mass black hole (IMBH; M ∼ 102-105 M⊙) and we explore the possibility of using the emission lines to identify such events and constrain the properties of the IMBH. To this end, we adopt and adapt the techniques developed by Strubbe & Quataert to study the optical emission lines produced when a main-sequence star is tidally disrupted by a supermassive black hole (BH). WDs are tidally disrupted outside of the event horizon of a <105 M⊙ BH, which makes these tidal disruption events good signposts of IMBHs. We focus on the optical and UV emission lines produced when the accretion flare photoionizes the stream of debris that remains unbound during the disruption. We find that the spectrum is dominated by lines due to ions of C and O, the strongest of which are Civ λ1549 at early times and [Oiii] λ5007 at later times. Furthermore, we model the profile of the emission lines in the [O iii] λλ4959, 5007 doublet and find that it is highly asymmetric with velocity widths of up to ∼2500 km s -1, depending on the properties of the WD-IMBH system and the orientation of the observer. Finally, we compare the models with observations of X-ray flares and optical emission lines in the cores of globular clusters and propose how future observations can test if these features are due to a WD that has been tidally disrupted by an IMBH.",
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Probing intermediate-mass black holes with optical emission lines from tidally disrupted white dwarfs. / Clausen, Drew; Eracleous, Michael.

In: Astrophysical Journal, Vol. 726, No. 1, 01.01.2011.

Research output: Contribution to journalArticle

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