RA/DEC (2000)
20:15:05.100 -70:59:33.89
303.77125 -70.992747
Type
SN Ia
Redshift
0.0206
Discovery ReportClassification Report
Related AstroNotes: 2025-222
Reporting Group
BlackGEM
Discovering Data Source
BlackGEM
Discovery Date
2025-07-20 03:04:32.000
TNS AT
Y
Public
Y
Discovery Mag
18.82
Filter
BG-q-BlackGem
Reporter/s
P. Groot, H. Tranin, F. Stoppa, D. Pieterse, G. Ramsay, S. Faris, P. Vreeswijk, N. Blagorodnova, J. van Roestel, H. Wichern, S. Scaringi
NEDSIMBADDECaLSPanSTARRS-1SkyMapperVizieRWISEDSSADS

Spectra

 ▌SN_2025rtk - 2025-08-01 01:48:21 Lesedi / Mookodi (BlackGEM)z=
▌Show H at z=vexp= km/s
▌Show He at z=vexp= km/s
▌Show He II at z=vexp= km/s
▌Show C II at z=vexp= km/s
▌Show C III at z=vexp= km/s
▌Show C IV at z=vexp= km/s
▌Show N II at z=vexp= km/s
▌Show N III at z=vexp= km/s
▌Show N IV at z=vexp= km/s
▌Show N V at z=vexp= km/s
▌Show O at z=vexp= km/s
▌Show [O I] at z=vexp= km/s
▌Show O II at z=vexp= km/s
▌Show [O II] at z=vexp= km/s
▌Show [O III] at z=vexp= km/s
▌Show O V at z=vexp= km/s
▌Show O VI at z=vexp= km/s
▌Show Na at z=vexp= km/s
▌Show Mg at z=vexp= km/s
▌Show Mg II at z=vexp= km/s
▌Show Si II at z=vexp= km/s
▌Show S II at z=vexp= km/s
▌Show Ca II at z=vexp= km/s
▌Show [Ca II] at z=vexp= km/s
▌Show Fe II at z=vexp= km/s
▌Show Fe III at z=vexp= km/s
▌Show Å at z=vexp= km/s
▌Show Å at z=vexp= km/s
▌Show Å at z=vexp= km/s
▌Show Å at z=vexp= km/s
▌Show Tellurics 
▌Show Galaxy lines at z=
▌Show WR-WN at z=vexp= km/s
▌Show WR-WC/O at z=vexp= km/s
   Binning factor: (rounded to nearest integer >1)
Mouse hovers at WL: 0 (rest),0 (observed)

Light curves

 ▌GOTO-S_GOTO-3_L
 ▌ATLAS-CHL_ATLAS-04_cyan
 ▌BG2_BlackGEM-Cam2_BG-q
   
Pointer position (MJD, Mag, Abs.Mag): (0.00, 0.00, 0.00)
Spectra
 ID Obs-date (UT) Tel / Inst Exp-Time Observer/s Reducer/s Group Spectrum ascii file Spectrum fits file Spec. Type Assoc. Groups End prop. period Remarks
21683 2025-08-01 01:48:21 Lesedi / Mookodi Moses Mlangeni BlackGEM tns_2025rtk_2025-08-01_01-48-20.748_Lesedi_Mookodi_BlackGEM.txt Object
Light Curves
Filter Tel / Inst Obs-date range JD Range Photometry
L-GOTO GOTO-S_GOTO-3 2025-07-16 14:50:38 - 2025-07-19 15:04:16 2460873.118503 - 2460876.127964 2
Photometry
ID Obs-date JD Mag. / Flux Err Lim. Mag./Flux Units Filter Tel / Inst Exp-time Observer/s Remarks
503983 2025-07-19 15:04:16 2460876.127964 19.04 0.09 ABMag L-GOTO GOTO-S_GOTO-3 360
503982 2025-07-16 14:50:38 2460873.118503 19.6 ABMag L-GOTO GOTO-S_GOTO-3 180 [Last non detection]
cyan-ATLAS ATLAS-CHL_ATLAS-04 2025-07-20 06:27:33 - 2025-07-24 04:32:32 2460876.76913 - 2460880.68926 2
Photometry
ID Obs-date JD Mag. / Flux Err Lim. Mag./Flux Units Filter Tel / Inst Exp-time Observer/s Remarks
504807 2025-07-24 04:32:32 2460880.68926 17 0.044 19.15 ABMag cyan-ATLAS ATLAS-CHL_ATLAS-04 30 Robot
504806 2025-07-20 06:27:33 2460876.76913 19.45 ABMag cyan-ATLAS ATLAS-CHL_ATLAS-04 30 Robot [Last non detection]
BG-q-BlackGem BG2_BlackGEM-Cam2 2025-07-19 03:08:52 - 2025-07-20 03:04:32 2460875.6311574 - 2460876.6281481 2
Photometry
ID Obs-date JD Mag. / Flux Err Lim. Mag./Flux Units Filter Tel / Inst Exp-time Observer/s Remarks
503899 2025-07-20 03:04:32 2460876.6281481 18.82 0.07 20.95 ABMag BG-q-BlackGem BG2_BlackGEM-Cam2 60 robotic
503898 2025-07-19 03:08:52 2460875.6311574 21.11 ABMag BG-q-BlackGem BG2_BlackGEM-Cam2 60 robotic [Last non detection]
AT Reports
ID Time received (UT) Sender Reporter/s Reporting group Disc. Data Source RA DEC Discovery date (UT) Discovery Mag. Filter Related files AT Type Host name Internal name Assoc. Groups End prop. period Remarks ADS Bibcode Unreal Auto classification
263670 2025-07-25 11:07:12 ATLAS_Bot1 J. Tonry,L. Denneau,H. Weiland et al. ATLAS ATLAS 20:15:05.054 -70:59:33.71 2025-07-24 04:32:32.064 17 cyan-ATLAS PSN ATLAS25ifb ATLAS N
263276 2025-07-21 09:02:41 GOTO_bot G. Ramsay,K. Ackley,M. Dyer et al. GOTO GOTO 20:15:05.249 -70:59:33.29 2025-07-19 15:04:15.744 19.04 L-GOTO Other GOTO25fem GOTO N
263235 2025-07-21 06:45:03 BlackGEM_Bot1 P. Groot,H. Tranin,F. Stoppa et al. BlackGEM BlackGEM 20:15:05.100 -70:59:33.89 2025-07-20 03:04:32.000 18.82 BG-q-BlackGem 1 PSN BGEM J201505.09-705933.8 BlackGEM 2025TNSTR2799....1G N
Related files
File Comments Last Modified (UT) Modified By
tns_2025rtk_atrep_263235_BlackGEM.pdf Finding Chart 2025-07-21 06:45:05 BlackGEM_Bot1
Classification Reports
ID Time received (UT) Sender Classifier/s Group Classification Redshift Spectra Related files Assoc. Groups End prop. period Remarks ADS Bibcode
21683 2025-08-01 18:39:28 Moses Mlangeni Moses Mlangeni (UCT/SAAO), Orapoleng Mogawana (UCT/SAAO), Francois Campher (UCT/SAAO), Paul Groot (Radboud/UCT/SAAO), Fiorenzo Stoppa (Oxford), Erez Zimmerman (Weizmann), Hugo Tranin (Barcelona) BlackGEM SN Ia 0.0206 1 1 BlackGEM We obtained an optical spectrum of AT2025rtk on 2025-08-01 01:48:20.748 UTC using the Lesedi 1.0-m telescope at the South African Astronomical Observatory (SAAO) equipped with the Mookodi spectrograph. The data were reduced using standard procedures, and the resulting spectrum was analysed with both the NGSF and SNID classification tools. Both tools consistently classify the transient as a normal Type Ia supernova (SN Ia-norm). The spectrum shows the characteristic broad Si II λ6355 absorption feature near 6150 Å (rest frame) consistent with a normal SN Ia at an early phase. We adopt the host galaxy redshift of z = 0.020631 (from NED) for this classification. Our measured redshift from the SN spectrum (z ≈ 0.0225) is consistent within expected uncertainties due to SN ejecta velocities. 2025TNSCR3031....1M
Related files
File Comments Last Modified (UT) Modified By
tns_2025rtk_atrep_21683_BlackGEM.pdf 2025-08-01 18:39:29 Moses Mlangeni
Spectra
ID Obs-date (UT) Tel / Inst Exp-Time Observer/s Reducer/s Group Spectrum ascii file Spectrum fits file Spec. Type Assoc. Groups End prop. period Remarks
21683 2025-08-01 01:48:21 Lesedi / Mookodi Moses Mlangeni BlackGEM tns_2025rtk_2025-08-01_01-48-20.748_Lesedi_Mookodi_BlackGEM.txt Object

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