------------------------------------------------------------------------------ The Astronomer's Telegram                   http://www.astronomerstelegram.org ------------------------------------------------------------------------------ Posted: Within the last 24 hours ============================================================================== ATEL #16582     ATEL #16582 Title: EP-FXT observation of the optical transient AT2024fkm: no X-ray signal detected Author: C. K. Li (IHEP, CAS), H. Y. Liu (NAOC, CAS), S. M. Jia , Y. Chen, W. W. Cui, H. Feng, J. Guan, D. W. Han, W. Li, C. Z. Liu, F. J. Lu, L. M. Song, J. Wang, J. J. Xu, J. Zhang, S. N. Zhang, H. S. Zhao, X. F. Zhao (IHEP, CAS), D. Y. Li, Z. X. Ling, Y. Liu, Z. Z. Lv, H. Sun, Q. Y. Wu, W. Yuan (NAOC, CAS), K. Nandra, A. Rau, P. Friedrich, N. Meidinger, V. Burwitz (MPE), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (UoL) and B. Cordier (CEA), Y. Z. Fan, X. F. Wu (PMO, CAS), X. F. Wang (THU), J. R. Mao (YNAO, CAS) on behalf of the Einstein Probe team Queries: ep_ta@bao.ac.cn Posted: 11 Apr 2024; 15:02 UT Subjects:X-ray, Supernovae Following the detection of the rapidly fading optical transient AT2024fkm (Brennan et al., AstroNote 2024-92; Smartt et al., AstroNote 2024-93; Karambelkar et al., AstroNote 2024-94), we performed an X-ray observation of AT2024fkm with the Follow-up X-ray Telescope (FXT) on board Einstein Probe (EP). The observation began on 2024-04-07 13:40:01 UT, about 5 days after the first detection of AT2024fkm, with a total exposure time of about 20 ks. No X-ray source was detected associated with AT2024fkm. We set an upper limit to the X-ray flux as 6.2E-15 erg/s/cm^2 (90% C.L.) in the 0.5-2keV band, assuming an absorbed power-law spectral shape with a photon index of 2 and the Galactic absorption N_H of 1.16E20cm^-2 in the source direction. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE, and CNES, aimed at enhancing our understanding of transient phenomena across the electromagnetic spectrum. ------------------------------------------------------------------------------ Password Certification: Yuan Liu (liuyuan@bao.ac.cn) https://www.astronomerstelegram.org/?read=16582 ============================================================================== ATEL #16583     ATEL #16583 Title: SOAR spectroscopic classification of ASASSN-24ck (AT 2024fjh) as a nova in the LMC Author: E. Aydi, J. Strader, I. Molina, R. Kyer, L. Chomiuk, R. Urquhart (MSU), K. C. Dage (Wayne State University), K. V. Sokolovsky (U. Illinois UC), K. Z. Stanek, C. S. Kochanek (OSU), B. J. Shappee (U. Hawaii) Queries: aydielia@msu.edu Posted: 11 Apr 2024; 15:02 UT Subjects:Optical, Cataclysmic Variable, Nova, Transient, Variables We report on optical spectroscopic follow-up of the optical transient ASASSN-24ck (AT 2024fjh), which was discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN; Shappee et al. 2014, ApJ, 788, 48; Kochanek et al. 2017PASP, 129, 4502) on 2024-04-01.1UT at g = 11.48 in the direction of the Large Magellanic Cloud. On 2024-04-06.4 we obtained low- and medium-resolution spectra of ASASSN-24ck using the Goodman spectrograph (Clemens et al. 2004, SPIE, 5492, 331) on the 4.1m SOAR telescope. The spectra show broad, double-peaked emission lines of Balmer, He I, N II, N III, and O I. The FWZI of Halpha is around 10,000 km/s. The spectra are that of a very fast classical nova after visible peak. The high velocities are consistent with the rapid evolution of the optical light curve, which showed a decline by 2 magnitudes from peak in just 4 days (t2 = 4 days). Follow up observations are encouraged. The ASAS-SN sky patrol light curve can be found here: https://asas-sn.osu.edu/sky-patrol/coordinate/c6a888f7-7635-4d75-b166-60e5100c2597 This ATel is based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministerio da Ciencia, Tecnologia, Inovacoes e Comunicacoes do Brasil (MCTIC/LNA), the U.S. National Science Foundation's National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU). ------------------------------------------------------------------------------