NinjaSat monitoring of Type I X-ray bursts from the clocked burster SRGA J144459.2–604207
Abstract The CubeSat X-ray observatory NinjaSat was launched on 2023 November 11 and has provided opportunities for agile and flexible monitoring of bright X-ray sources. On 2024 February 23, the NinjaSat team started long-term observation of the new X-ray source SRGA J144459.2–604207 as the first scientific target, which was discovered on 2024 February 21 and recognized as the sixth clocked X-ray burster. Our 25-day observation covered almost the entire decay of this outburst from two days after the peak at ${\sim}100\:$mCrab on February 23 until March 18 at a few mCrab level. The Gas Multiplier Counter on board NinjaSat successfully detected 12 Type I X-ray bursts with a typical burst duration of ${\sim}20\:$s, shorter than other clocked burster systems. As the persistent X-ray emission declined by a factor of five, X-ray bursts showed a notable change in its morphology: the rise time became shorter from $4.4(7)\:$s to $0.3(3)\:$s ($1\sigma$ errors), and the peak amplitude increased by $44\%$. The burst recurrence time $\Delta t_{\rm rec}$ also became longer, from 2 to $10\:$hr, following the relation of $\Delta t_{\rm rec} \propto F_{\rm per}^{-0.84}$, where $F_{\rm per}$ is the persistent X-ray flux, by applying a Markov chain Monte Carlo method. The short duration of bursts is explained by the He-enhanced composition of accretion matter and the relation between $\Delta t_{\rm {rec}}$ and $F_{\rm per}$ by a massive neutron star. This study demonstrated that CubeSat pointing observations can provide valuable astronomical X-ray data.
Authors
- Nobuya Nishimura (ORCID: https://orcid.org/0000-0002-0842-7856)
- Keisuke Uchiyama (ORCID: https://orcid.org/0000-0002-7752-9389)
- Hiroki Sato (ORCID: https://orcid.org/0000-0002-1364-2198)
- Tsubasa Tamba (ORCID: https://orcid.org/0000-0001-7631-4362)
- Keiichi Yamasaki
- Toru Tamagawa (ORCID: https://orcid.org/0000-0002-8801-6263)
- S Hayashi (ORCID: https://orcid.org/0000-0002-1830-4534)
- S. Iwata (ORCID: https://orcid.org/0009-0007-8444-3640)
- W. Iwakiri (ORCID: https://orcid.org/0000-0002-0207-9010)
- Akira Dohi
- Teruaki Enoto (ORCID: https://orcid.org/0000-0003-1244-3100)
- Yuanhui Zhou
- Ryosuke Hirai (ORCID: https://orcid.org/0000-0002-8032-8174)
- Arata Jujo
- Naoyuki OTA
- Yo Kato
- Chin‐Ping Hu (ORCID: https://orcid.org/0000-0001-8551-2002)
- H. Takahashi (ORCID: https://orcid.org/0000-0001-6314-5897)
- Masaki Numazawa (ORCID: https://orcid.org/0000-0002-4203-2647)
- T. Mihara (ORCID: https://orcid.org/0000-0002-6337-7943)
- Takuya Takahashi (ORCID: https://orcid.org/0009-0007-3706-746X)
- Yuto Yoshida (ORCID: https://orcid.org/0009-0005-3576-1859)
- Hirokazu Odaka
- S. Watanabe (ORCID: https://orcid.org/0009-0000-0855-046X)
- Kentaro Taniguchi
- A Aoyama (ORCID: https://orcid.org/0009-0008-3926-363X)
- Takao Kitaguchi
- Tomoshi Takeda (ORCID: https://orcid.org/0009-0008-5133-9131)
Institutions
- Hiroshima University (JP)
- Pioneer (United States) (US)
- Chiba University (JP)
- Tokyo University of Science (JP)
- Shibaura Institute of Technology (JP)
- Kyoto University (JP)
- Groupe Institut des Hautes Études Économiques et Sociales (MA)
- RIKEN (JP)
- ARC Centre of Excellence for Gravitational Wave Discovery (AU)
- Institute of Space and Astronautical Science (JP)
- National Astronomical Observatory of Japan (JP)
- RIKEN Nishina Center (JP)
- Monash University (AU)
- Tokyo Metropolitan University (JP)
- National Changhua University of Education (TW)
- The University of Tokyo (JP)
- The University of Osaka (JP)
Publication Details
- Journal
- Publications of the Astronomical Society of Japan
- Published
- 2025-05-14
- DOI
- https://doi.org/10.1093/pasj/psaf003
- Citations
- 10
- Primary Topic
- Astrophysical Phenomena and Observations
- Type
- article
- Field-Weighted Citation Impact
- 11.55
Funders
- Japan Society for the Promotion of Science
- RIKEN