Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The extreme mass ratio inspiral (EMRI), defined as a stellar-mass compact object inspiraling into a supermassive black hole (SMBH), has been widely argued to be a low-frequency gravitational-wave (GW) source. Providing accurate measurements of the black hole mass and spin of EMRIs is one of the primary interests for the Laser Interferometer Space Antenna (LISA). However, it is currently understood that there are no electromagnetic (EM) counterparts to EMRIs. Here we show a new formation channel of EMRIs with tidal disruption flares as EM counterparts. In this scenario, flares can be produced from the tidal stripping of the helium (He) envelope of a massive star by an SMBH. The remaining compact core of the massive star then evolves into an EMRI. We find that, under a certain initial eccentricity and semimajor axis, the GW frequency of the inspiral can enter the LISA band within 10 ∼ 20 yr, which makes the tidal disruption flare an EM precursor to an EMRI. Although the event rate is just <jats:inline-formula> <jats:tex-math> <?CDATA $2\times {10}^{-4}\,{\mathrm{Gpc}}^{-3}\,{\mathrm{yr}}^{-1}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>2</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi>Gpc</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi>yr</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlab55e2ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, this association not only improves the localization accuracy of LISA and helps us to find the host galaxy of EMRI, but it also serves as a new GW standard siren for cosmology.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Massive protostars generate strong radiation feedback, which may help set the mass that they achieve by the end of the accretion process. Studying such feedback is therefore crucial for understanding the formation of massive stars. We report the discovery of a photoionized bipolar outflow toward the massive protostar G45.47+0.05 using high-resolution observations at 1.3 mm with the Atacama Large Millimeter/Submillimeter Array (ALMA) and at 7 mm with the Karl G. Jansky Very Large Array (VLA). By modeling the free–free continuum, the ionized outflow is found to be a photoevaporation flow with an electron temperature of 10,000 K and an electron number density of ∼1.5 × 10<jats:sup>7</jats:sup> cm<jats:sup>−3</jats:sup> at the center, launched from a disk of radius of 110 au. H30<jats:italic>α</jats:italic> hydrogen recombination line emission shows strong maser amplification, with G45 being one of very few sources to show such millimeter recombination line masers. The mass of the driving source is estimated to be 30–50 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> based on the derived ionizing photon rate, or 30–40 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> based on the H30<jats:italic>α</jats:italic> kinematics. The kinematics of the photoevaporated material is dominated by rotation close to the disk plane, while accelerated to outflowing motion above the disk plane. The mass loss rate of the photoevaporation outflow is estimated to be ∼(2–3.5) × 10<jats:sup>−5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>. We also found hints of a possible jet embedded inside the wide-angle ionized outflow with nonthermal emissions. The possible coexistence of a jet and a massive photoevaporation outflow suggests that, in spite of the strong photoionization feedback, accretion is still ongoing.</jats:p>