<p>Hercules X-1 has a consistent 35-day periodic light-curve in X-rays consisting of main high, short high and low states caused by a precessing tilted and twisted accretion disk. The MAXI instrument has recently measured the average 35-day X-ray light-curve with small errors. The current work utilizes the MAXI data and ray-tracing software to derive a better-constrained geometric model of the accretion disk than previous studies. A basic 3-D model based on previous work is iteratively expanded in complexity until it can satisfactorily replicate the 35-day light-curve. We summarize the disk models tested and confirm the requirement for a scattering corona and for a disk atmosphere which is different for the inner and outer disk. We are able to constrain the system inclination to <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11038_2025_9564_Article_IEq1.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="79" /> </InlineMediaObject> <EquationSource Format="TEX">$85.5\pm 0.3^{\circ }$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>85.5</mn> <mo>±</mo> <mn>0</mn> <mo>.</mo> <msup> <mn>3</mn> <mo>∘</mo> </msup> </mrow> </math></EquationSource> </InlineEquation>, much improved compared to previous estimates (<InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11038_2025_9564_Article_IEq2.gif" Format="GIF" Height="6" Rendition="HTML" Resolution="72" Type="Linedraw" Width="17" /> </InlineMediaObject> <EquationSource Format="TEX">$\sim$</EquationSource> <EquationSource Format="MATHML"><math> <mo>∼</mo> </math></EquationSource> </InlineEquation>82 to <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11038_2025_9564_Article_IEq3.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="25" /> </InlineMediaObject> <EquationSource Format="TEX">$88^\circ$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mn>88</mn> <mo>∘</mo> </msup> </math></EquationSource> </InlineEquation>). The constraint on inclination allows for more accurate determinations of the radius of the companion HZ Her (2.64 to 2.83<InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11038_2025_9564_Article_IEq4.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="44" /> </InlineMediaObject> <EquationSource Format="TEX">$\times 10^{11}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>×</mo> <msup> <mn>10</mn> <mn>11</mn> </msup> </mrow> </math></EquationSource> </InlineEquation> cm), mass of the HZ Her (2.34 to 2.45 <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11038_2025_9564_Article_IEq5.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="28" /> </InlineMediaObject> <EquationSource Format="TEX">$\hbox {M}_\odot$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>M</mtext> <mo>⊙</mo> </msub> </math></EquationSource> </InlineEquation>) and mass of the neutron star (1.52 to 1.69 <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11038_2025_9564_Article_IEq6.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="28" /> </InlineMediaObject> <EquationSource Format="TEX">$\hbox {M}_\odot$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>M</mtext> <mo>⊙</mo> </msub> </math></EquationSource> </InlineEquation>).</p>

The geometry of the Hercules X-1 accretion disk from X-rays

期刊论文
出版模式：

开放获取
发表日期：

2025年3月24日

查看全文

Denis Leahy,
Jake Mendelsohn

摘要

Hercules X-1 has a consistent 35-day periodic light-curve in X-rays consisting of main high, short high and low states caused by a precessing tilted and twisted accretion disk. The MAXI instrument has recently measured the average 35-day X-ray light-curve with small errors. The current work utilizes the MAXI data and ray-tracing software to derive a better-constrained geometric model of the accretion disk than previous studies. A basic 3-D model based on previous work is iteratively expanded in complexity until it can satisfactorily replicate the 35-day light-curve. We summarize the disk models tested and confirm the requirement for a scattering corona and for a disk atmosphere which is different for the inner and outer disk. We are able to constrain the system inclination to $85.5\pm 0.3^{\circ }$ $85.5 \pm 0 . 3^{\circ}$ , much improved compared to previous estimates ( $\sim$ $\sim$ 82 to $88^\circ$ $88^{\circ}$ ). The constraint on inclination allows for more accurate determinations of the radius of the companion HZ Her (2.64 to 2.83 $\times 10^{11}$ $\times 10^{11}$ cm), mass of the HZ Her (2.34 to 2.45 $\hbox {M}_\odot$ $M_{⊙}$ ) and mass of the neutron star (1.52 to 1.69 $\hbox {M}_\odot$ $M_{⊙}$ ).