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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').

19109 results found.

  1. GRB 250322A: third epoch of NOT optical observations
  2. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  3. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  4. GRB 250322A: further NOT optical observations
  5. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  6. GRB 250322A: Swift/UVOT Upper Limits
  7. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  8. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  9. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  10. GRB 250321B: Swift-XRT observations
  11. EP250321a: TNOT Observation of Optical Counterpart
  12. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  13. SVOM/sb25032302: SVOM detection of a long X-ray transient
  14. GRB 250322A: VLT optical observations
  15. GRB 250322A: VLT near-infrared observations
  16. FRB 250316A: DDOTI Continued Optical Observations
  17. GRB 250322A: NOT optical upper limits
  18. GRB 250322A: Enhanced Swift-XRT position
  19. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  20. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  21. EP250321a: Liverpool Telescope optical follow-up
  22. EP250321a: Mondy AZT-33IK Optical Observations
  23. GRB 250322A: Swift detection of a short burst
  24. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  25. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  26. EP250321A: COLIBRÍ Continuing Optical Observations
  27. EP250321a: WFST optical observations
  28. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  29. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  30. EP250321a: Xinglong 216 decaying optical observations
  31. GRB 250321A: Swift-XRT refined Analysis
  32. EP 250321A: Optical counterpart detection by LCO.
  33. EP250321a: Kinder optical follow-up observations
  34. GRB 250321A: Swift/UVOT Upper Limits
  35. GRB 250320B: SVOM/GRM observation of a long burst
  36. EP250321a: LCO optical counterpart detection
  37. EP250321A: COLIBRÍ Optical Observations
  38. EP250321a: REM optical/NIR afterglow detection
  39. EP250321a: BOOTES-5/JGT optical afterglow detection
  40. EP250321a: TRT optical counterpart detection
  41. EP250321a: Einstein Probe detection of an X-ray transient
  42. GRB 250321A: GOTO optical upper limits
  43. GRB 250314A: Keck/NIRC2 J-band upper limit
  44. EP250226a/GRB 250226A: KAIT optical observations
  45. GRB 250321A: Swift detection of a burst
  46. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  47. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  48. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  49. GRB 250313A: GRBAlpha detection
  50. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  51. GRB 250317B: OHP/T193 continued follow-up
  52. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  53. GRB 250317C: SVOM/GRM observation of a long burst
  54. GRB 250317B: Leavitt Observatory optical upper limit
  55. GRB 250309B/AT2025dws: further ATCA observations
  56. GRB 250317B: Mondy AZT-33IK Optical Observations
  57. GRB 250317C: AstroSat CZTI detection
  58. GRB 250317B: NOT optical observations suggest an optical plateau phase
  59. GRB 250317B: OHP/T193 optical observations
  60. GRB250312A: Swift/UVOT Upper Limits
  61. GRB 250317B: REM optical/NIR observations
  62. GRB 250316A: Swift/UVOT Upper Limits
  63. GRB 250314A: REM optical/NIR upper limits
  64. GRB 250316A: AbAO AS-32 Optical Upper Limit
  65. EP 250317B: Fading optical counterpart detection by LCO
  66. GRB 250316A: Swift-XRT afterglow detection
  67. GRB 250317B: LCO detection of the fading optical afterglow
  68. GRB250317B: SVOM/VT detection of an optical candidate from VHF data
  69. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  70. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  71. GRB 250317B: SVOM detection of a burst
  72. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  73. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  74. GRB 250314A: Swift/UVOT Upper Limits
  75. GRB 250312B: GRBAlpha detection
  76. GRB 250314A: Swift XRT Detection
  77. EP250315a: optical counterpart candidate detected by Gemini North
  78. EP250315a: Einstein Probe detection of an X-ray transient
  79. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  80. SVOM/MXT upper limit on GRB 250314A
  81. GRB 250314A: SVOM/VT upper limit
  82. GRB 250314A: NOT near-infrared candidate counterpart
  83. GRB 250313A: Swift-XRT observations
  84. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  85. Konus-Wind detection of GRB 250313A
  86. Konus-Wind detection of GRB 250308A
  87. GRB 250314A: SVOM detection of a burst
  88. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  89. EP250304a: Pan-STARRS r and i-band imaging and photometry
  90. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  91. Fermi GRB 250313A: Global MASTER-Net observations report
  92. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  93. GRB 250312A: Enhanced Swift-XRT position
  94. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  95. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  96. GRB 250312A: Swift detection of a burst
  97. GRB 241213A: VIRT Optical Upper Limit
  98. GRB 241228A: VIRT Optical Upper Limit
  99. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  100. GRB 230509B: 1.3m DFOT Optical observations

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