- vsnet-campaign-xray - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-campaign-xray 482]Re: SwiftJ1727.8-1613: superhumps?
by Taichi Kato 11 Dec '23

11 Dec '23

Re: SwiftJ1727.8-1613: superhumps? (Re: [vsnet-alert 27954] SwiftJ1727.8-1613: superhumps?, Sep. 23) Using the available data since then, the current preferred period is 0.14088(3) d (mean amplitude 0.07 mag, singly peaked). The period of 0.2116(1) d in [vsnet-alert 27954] was 1.5 times of this period.

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[vsnet-campaign-xray 481]SwiftJ1727.8-1613: superhumps?
by Taichi Kato 23 Sep '23

23 Sep '23

SwiftJ1727.8-1613: superhumps? This X-ray transient looks like to have started showing superhumps. An analysis of the data since Sep. 17 shows a signal at 0.2116(1) d (full amplitude 0.07 mag with multiple peaks in a period). Signals at P/2 or P/3 were weaker and the 0.2116-d period appears real. This signal apparently appeared in conjunction with the spectral/state transition (ATel #16247). Considering the case of ASASSN-18ey = MAXI J1820+070 (arXiv:2107.03681, Variable Star Bulletin 74), the current variation appears to be stage A superhumps. observers: Berto Monard, Itoh-san and Josch Hambsch

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[vsnet-campaign-xray 480]Re: SwiftJ1727.8-1613
by Taichi Kato 26 Aug '23

26 Aug '23

Re: SwiftJ1727.8-1613 Itoh-san reported time-resolved photometry (as TCP J17274332-1612188). Strong short-term variations comparable to V404 Cyg (more than 0.1 mag) were not detected.

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[vsnet-campaign-xray 479]MAXI J1807+132 outburst again
by Taichi Kato 13 Jul '23

13 Jul '23

MAXI J1807+132 outburst again (See ATel #16128) Combined magnitudes for ASAS-SN but clearly in outburst. YYYYMMDD(UT) mag observer 20230704.1507 <16.166g (ASAS-SN Sky Patrol Photom. DB (Hart+2023; Shappee+2014)) 20230704.7692 <15.957g (ASAS-SN Sky Patrol Photom. DB (Hart+2023; Shappee+2014)) 20230705.7997 16.703g (ASAS-SN Sky Patrol Photom. DB (Hart+2023; Shappee+2014)) 20230708.4306 16.754o (ATLAS Forced Photometry (Tonry+2018; Shingles+2021)) 20230708.4335 16.677o (ATLAS Forced Photometry (Tonry+2018; Shingles+2021)) 20230708.4648 16.659o (ATLAS Forced Photometry (Tonry+2018; Shingles+2021)) 20230708.4933 16.569o (ATLAS Forced Photometry (Tonry+2018; Shingles+2021)) 20230709.2188 16.106o (ATLAS Forced Photometry (Tonry+2018; Shingles+2021)) 20230709.2243 16.140o (ATLAS Forced Photometry (Tonry+2018; Shingles+2021)) 20230709.2322 16.256o (ATLAS Forced Photometry (Tonry+2018; Shingles+2021)) 20230709.4637 16.247g (ASAS-SN Sky Patrol Photom. DB (Hart+2023; Shappee+2014)) 20230711.2168 15.920g (ASAS-SN Sky Patrol Photom. DB (Hart+2023; Shappee+2014)) 20230711.2181 15.966g (ASAS-SN Sky Patrol Photom. DB (Hart+2023; Shappee+2014)) 20230711.8895 16.457c (ATLAS Forced Photometry (Tonry+2018; Shingles+2021)) 20230711.9218 16.472c (ATLAS Forced Photometry (Tonry+2018; Shingles+2021)) 20230711.9250 16.443c (ATLAS Forced Photometry (Tonry+2018; Shingles+2021)) 20230711.9453 16.444c (ATLAS Forced Photometry (Tonry+2018; Shingles+2021))

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[vsnet-campaign-xray 478]MAXI J1834-021 (ATel 15932)
by Taichi Kato 07 Mar '23

07 Mar '23

MAXI J1834-021 (ATel 15932) ATEL #15932 ATEL #15932 Title: MAXI J1834-021: Swift/XRT detection and localization Author: J. A. Kennea (PSU), K. L. Page (Leicester) and H. Negoro (Nihon U) Queries: jak51(a)psu.edu Posted: 6 Mar 2023; 21:54 UT Subjects:X-ray, Transient MAXI reported a new X-ray transient, MAXI J1834-021 (ATEL #15929), first seen around February 5th, 2023. On March 6th, 2023 Swift performed a target of opportunity observation, consisting of 7 pointings of 300s each with XRT in Photon Counting mode, in order to cover the MAXI error region. We find a single bright, uncatalogued point source inside the MAXI error region at the following coordinates: RA/Dec(J2000) = 279.0362, -2.2872, which is equivalent to: RA(J2000) =18h 36m 08.70s, Dec(J2000) = -02d 17m 13.9s, with an error radius 3.5 arc-seconds (90% confidence). This position does not much the position of any known X-ray transient, therefore we consider this the likely counterpart of MAXI J1834-021, and confirm that this is a new transient. The position is coincident with two stars in the Gaia EDR3 catalog, Gaia EDR3 4259671048608866560 and Gaia EDR3 4259671052930848384, with magnitudes G=15.84 and G=20.79 respectively. It$B!G(Bs not possible to rule out either counterpart based on the XRT position. The source is bright, with a pile-up corrected count rate of 4.4 +/- 0.6 count/s. The spectrum is well described by an absorbed power-law model, with N_H = 1.46 x 10^22 cm^-2, photon index = 2.2 +/- 1.0 and an observed flux of 2.2 +/- 0.9 x 10^-10 erg/s/cm^2 (0.3-10 keV). We encourage follow-up to identify this new transient.

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[vsnet-campaign-xray 477]Swift J1913.1+1946
by Taichi Kato 10 Oct '22

10 Oct '22

Swift J1913.1+1946 16.6-mag X-ray transient. ATEL #15650 ATEL #15650 Title: Swift J1913.1+1946 a new bright hard X-ray and optical transient Author: S. Dichiara (PSU), J. D. Gropp (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (U Tampa), F. E. Marshall (NASA/GSFC), A. Tohuvavohu (U Toronto) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team Queries: jak51(a)psu.edu Posted: 9 Oct 2022; 14:44 UT Subjects:Optical, X-ray, Transient At 2022-10-09 14:10:17 UT, the Swift Burst Alert Telescope (BAT) triggered and located the new transient Swift J1913.1+1946 (triggers=1126853 and 1126854). Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 288.263, +19.803 which is RA(J2000) = 19h 13m 03s Dec(J2000) = +19d 48' 09" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). After slewing, the source was still visible (leading to the second trigger). The XRT began observing the field at 14:13:30 UT, 143 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 288.2643, 19.7712 which is equivalent to: RA(J2000) = 19h 13m 3.43s Dec(J2000) = +19d 46' 16.3" with an uncertainty of 5.6 arcseconds (radius, 90% containment). This location is 1.9 arc minutes from the BAT onboard position, within the BAT error circle. UVOT took a finding chart exposure of 150 seconds with the White filter starting 179 seconds after the BAT trigger. There is a candidate counterpart in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 19:13:03.48 = 288.26452 DEC(J2000) = +19:46:24.6 = 19.77350 with a 90%-confidence error radius of about 0.61 arc sec. This position is 8.3 arc sec. from the center of the XRT error circle. The estimated magnitude is 16.63 with a 1-sigma error of about 0.14. No correction has been made for the large, but uncertain, extinction expected.

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