Optical follow-up of the neutron star-black hole mergers S200105ae and S200115j. (arXiv:2009.07210v1 [astro-ph.HE])

Optical follow-up of the neutron star-black hole mergers S200105ae and S200115j. (arXiv:2009.07210v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Anand_S/0/1/0/all/0/1">Shreya Anand</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Coughlin_M/0/1/0/all/0/1">Michael W. Coughlin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kasliwal_M/0/1/0/all/0/1">Mansi M. Kasliwal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bulla_M/0/1/0/all/0/1">Mattia Bulla</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ahumada_T/0/1/0/all/0/1">Tomás Ahumada</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Carracedo_A/0/1/0/all/0/1">Ana Sagués Carracedo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Almualla_M/0/1/0/all/0/1">Mouza Almualla</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Andreoni_I/0/1/0/all/0/1">Igor Andreoni</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stein_R/0/1/0/all/0/1">Robert Stein</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Foucart_F/0/1/0/all/0/1">Francois Foucart</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Singer_L/0/1/0/all/0/1">Leo P. Singer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sollerman_J/0/1/0/all/0/1">Jesper Sollerman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bellm_E/0/1/0/all/0/1">Eric C. Bellm</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bolin_B/0/1/0/all/0/1">Bryce Bolin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Caballero_Garcia_M/0/1/0/all/0/1">M. D. Caballero-García</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Castro_Tirado_A/0/1/0/all/0/1">Alberto J. Castro-Tirado</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cenko_S/0/1/0/all/0/1">S. Bradley Cenko</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+De_K/0/1/0/all/0/1">Kishalay De</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dekany_R/0/1/0/all/0/1">Richard G. Dekany</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Duev_D/0/1/0/all/0/1">Dmitry A. Duev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Feeney_M/0/1/0/all/0/1">Michael Feeney</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fremling_C/0/1/0/all/0/1">Christoffer Fremling</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Goldstein_D/0/1/0/all/0/1">Daniel A. Goldstein</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Golkhou_V/0/1/0/all/0/1">V. Zach Golkhou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Graham_M/0/1/0/all/0/1">Matthew J. Graham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Guessoum_N/0/1/0/all/0/1">Nidhal Guessoum</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hankins_M/0/1/0/all/0/1">Matthew J. Hankins</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hu_Y/0/1/0/all/0/1">Youdong Hu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kong_A/0/1/0/all/0/1">Albert K. H. Kong</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kool_E/0/1/0/all/0/1">Erik C. Kool</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kulkarni_S/0/1/0/all/0/1">S. R. Kulkarni</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kumar_H/0/1/0/all/0/1">Harsh Kumar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Laher_R/0/1/0/all/0/1">Russ R. Laher</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Masci_F/0/1/0/all/0/1">Frank J. Masci</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mroz_P/0/1/0/all/0/1">Przemek Mróz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nissanke_S/0/1/0/all/0/1">Samaya Nissanke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Porter_M/0/1/0/all/0/1">Michael Porter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reusch_S/0/1/0/all/0/1">Simeon Reusch</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Riddle_R/0/1/0/all/0/1">Reed Riddle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rosnet_P/0/1/0/all/0/1">Philippe Rosnet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rusholme_B/0/1/0/all/0/1">Ben Rusholme</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Serabyn_E/0/1/0/all/0/1">Eugene Serabyn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sanchez_Ramirez_R/0/1/0/all/0/1">R. Sánchez-Ramírez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rigault_M/0/1/0/all/0/1">Mickael Rigault</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shupe_D/0/1/0/all/0/1">David L. Shupe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Smith_R/0/1/0/all/0/1">Roger Smith</a>, et al. (3 additional authors not shown)

LIGO and Virgo’s third observing run (O3) revealed the first neutron
star-black hole (NSBH) merger candidates in gravitational waves. These events
are predicted to synthesize r-process elements creating optical/near-IR
“kilonova” (KN) emission. The joint gravitational-wave (GW) and electromagnetic
detection of an NSBH merger could be used to constrain the equation of state of
dense nuclear matter, and independently measure the local expansion rate of the
universe. Here, we present the optical follow-up and analysis of two of the
only three high-significance NSBH merger candidates detected to date, S200105ae
and S200115j, with the Zwicky Transient Facility (ZTF). ZTF observed
$sim$,48% of S200105ae and $sim$,22% of S200115j’s localization
probabilities, with observations sensitive to KNe brighter than $-$17.5,mag
fading at 0.5,mag/day in g- and r-bands; extensive searches and systematic
follow-up of candidates did not yield a viable counterpart. We present
state-of-the-art KN models tailored to NSBH systems that place constraints on
the ejecta properties of these NSBH mergers. We show that with depths of $rm
m_{rm AB}approx 22$ mag, attainable in meter-class, wide field-of-view survey
instruments, strong constraints on ejecta mass are possible, with the potential
to rule out low mass ratios, high BH spins, and large neutron star radii.

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