Optical Observations of the High Mass X-ray Binary MAXI J0709$-$159/LY CMa

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Main Authors: Shidatsu, Megumi, Kawai, Nobuyuki, Maehara, Hiroyuki, Goto, Emi, Urabe, Sota, Iwakiri, Wataru, Tsuboi, Yohko, Nemoto, Noboru, Nawa, Sakura, Sugizaki, Mutsumi, Nakajima, Motoki, Niwano, Masafumi, Hosokawa, Ryohei, Sakamoto, Marie, Matsuoka, Yoshiki
Format: Preprint
Published: 2025
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author Shidatsu, Megumi
Kawai, Nobuyuki
Maehara, Hiroyuki
Goto, Emi
Urabe, Sota
Iwakiri, Wataru
Tsuboi, Yohko
Nemoto, Noboru
Nawa, Sakura
Sugizaki, Mutsumi
Nakajima, Motoki
Niwano, Masafumi
Hosokawa, Ryohei
Sakamoto, Marie
Matsuoka, Yoshiki
author_facet Shidatsu, Megumi
Kawai, Nobuyuki
Maehara, Hiroyuki
Goto, Emi
Urabe, Sota
Iwakiri, Wataru
Tsuboi, Yohko
Nemoto, Noboru
Nawa, Sakura
Sugizaki, Mutsumi
Nakajima, Motoki
Niwano, Masafumi
Hosokawa, Ryohei
Sakamoto, Marie
Matsuoka, Yoshiki
contents We report on the optical spectroscopic monitoring of the X-ray transient MAXI J0709$-$159 (identified as the Be star LY CMa) performed for about 1.5 months after the X-ray detection with MAXI. The observed spectrum showed a double-peaked H$α$ line with a peak-to-peak separation of $\sim 230$ km s$^{-1}$, suggestive of the Be disk origin. We also detected a broad wing of the H$α$ line with a line-of-sight velocity of $\gtrsim 900$ km s$^{-1}$, which could be explained by the accretion disk of the compact object or a stellar wind from the Be star. Initially the H$α$ line showed an asymmetric profile with an enhanced blue peak, and then the blue peak decreased in $\sim$ 3 weeks to a similar strength to the red peak. We suggest that the evolution of the blue peak is associated with the X-ray activity and generated by the turbulence of the Be disk due to the passage of the compact object. We also investigated flux variation using the archival TESS data and found quasi-periodic variations with frequencies of $\sim 1$ and $\sim 2$ day$^{-1}$, which were likely caused by the pulsation of the B star. The overall variability properties on timescales of $\sim$ day were similar to those in Be X-ray binaries, rather than supergiant X-ray binaries.
format Preprint
id arxiv_https___arxiv_org_abs_2503_21118
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Optical Observations of the High Mass X-ray Binary MAXI J0709$-$159/LY CMa
Shidatsu, Megumi
Kawai, Nobuyuki
Maehara, Hiroyuki
Goto, Emi
Urabe, Sota
Iwakiri, Wataru
Tsuboi, Yohko
Nemoto, Noboru
Nawa, Sakura
Sugizaki, Mutsumi
Nakajima, Motoki
Niwano, Masafumi
Hosokawa, Ryohei
Sakamoto, Marie
Matsuoka, Yoshiki
High Energy Astrophysical Phenomena
Solar and Stellar Astrophysics
We report on the optical spectroscopic monitoring of the X-ray transient MAXI J0709$-$159 (identified as the Be star LY CMa) performed for about 1.5 months after the X-ray detection with MAXI. The observed spectrum showed a double-peaked H$α$ line with a peak-to-peak separation of $\sim 230$ km s$^{-1}$, suggestive of the Be disk origin. We also detected a broad wing of the H$α$ line with a line-of-sight velocity of $\gtrsim 900$ km s$^{-1}$, which could be explained by the accretion disk of the compact object or a stellar wind from the Be star. Initially the H$α$ line showed an asymmetric profile with an enhanced blue peak, and then the blue peak decreased in $\sim$ 3 weeks to a similar strength to the red peak. We suggest that the evolution of the blue peak is associated with the X-ray activity and generated by the turbulence of the Be disk due to the passage of the compact object. We also investigated flux variation using the archival TESS data and found quasi-periodic variations with frequencies of $\sim 1$ and $\sim 2$ day$^{-1}$, which were likely caused by the pulsation of the B star. The overall variability properties on timescales of $\sim$ day were similar to those in Be X-ray binaries, rather than supergiant X-ray binaries.
title Optical Observations of the High Mass X-ray Binary MAXI J0709$-$159/LY CMa
topic High Energy Astrophysical Phenomena
Solar and Stellar Astrophysics
url https://arxiv.org/abs/2503.21118