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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').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

27320 results found.

  1. GRB 250328A: SVOM/C-GFT optical upper limit
  2. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  3. GRB 250329A: SVOM/VT optical counterpart confirmation
  4. GRB 250329A: SVOM detection of a burst
  5. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  6. GRB 250327B: J-band observations with WINTER
  7. GRB 250327B: LCO optical counterpart detection
  8. GRB 250328A: SVOM detection of a burst
  9. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  10. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  11. GRB 250327B: CrAO and SAO RAS Optical Observations
  12. GRB 250327b: Liverpool Telescope optical observations
  13. GRB 250322A: GRANDMA/TNOT optical upper limits
  14. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  15. GRB 250327A: SVOM/VT upper limits on the XRT position
  16. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  17. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  18. GRB 250327B: Las Cumbres optical counterpart detection
  19. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  20. GRB 250327B: 1.6m Mephisto optical observations
  21. GRB 250327A: Swift-XRT refined Analysis
  22. GRB 250327B: SVOM/VT optically bright counterpart
  23. GRB 250327B: SAO RAS optical candidate
  24. GRB 250327B: SVOM detection of a burst
  25. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  26. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  27. GRB 250327A: J-band observations with WINTER
  28. GRB 250327A: SVOM/VT optical candidate
  29. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  30. GRB 250327A: DDOTI Optical Observations
  31. GRB 250327A: COLIBRÍ optical upper limit
  32. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  33. IPN triangulation of GRB 250322B
  34. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  35. EP250321a: Mondy AZT-33IK Continued Optical Observations
  36. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  37. GRB 250322A: third epoch of NOT optical observations
  38. GRB 250322A: Swift-BAT refined analysis
  39. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  40. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  41. GRB 250322A: further NOT optical observations
  42. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  43. GRB 250322A: Swift/UVOT Upper Limits
  44. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  45. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  46. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  47. GRB 250321B: Swift-XRT observations
  48. GRB 250322A: Swift-XRT refined Analysis
  49. EP250321a: TNOT Observation of Optical Counterpart
  50. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  51. SVOM/sb25032302: SVOM detection of a long X-ray transient
  52. GRB 250322B: AstroSat CZTI detection of a bright long burst
  53. GRB 250322A: VLT optical observations
  54. GRB 250322A: VLT near-infrared observations
  55. FRB 250316A: DDOTI Continued Optical Observations
  56. GRB 250322A: NOT optical upper limits
  57. GRB 250322A: Enhanced Swift-XRT position
  58. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  59. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  60. EP250321a: Liverpool Telescope optical follow-up
  61. EP250321a: Mondy AZT-33IK Optical Observations
  62. GRB 250322A: Swift detection of a short burst
  63. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  64. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  65. EP250321A: COLIBRÍ Continuing Optical Observations
  66. EP250321a: WFST optical observations
  67. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  68. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  69. GRB 250320B: Fermi GBM Observation
  70. EP250321a: Xinglong 216 decaying optical observations
  71. GRB 250321A: Swift-BAT refined analysis
  72. GRB 250321A: Swift-XRT refined Analysis
  73. EP 250321A: Optical counterpart detection by LCO.
  74. EP250321a: Kinder optical follow-up observations
  75. GRB 250321A: Swift/UVOT Upper Limits
  76. GRB 250320B: SVOM/GRM observation of a long burst
  77. EP250321a: LCO optical counterpart detection
  78. EP250321a: Swift-XRT detection of an X-ray source
  79. EP250321A: COLIBRÍ Optical Observations
  80. GRB 250320B: AstroSat CZTI detection
  81. EP250321a: REM optical/NIR afterglow detection
  82. EP250321a: TRT optical counterpart detection
  83. Swift GRB 250321A: Global MASTER-Net observations report
  84. EP250321a: Einstein Probe detection of an X-ray transient
  85. GRB 250321A: GOTO optical upper limits
  86. GRB 250314A: Keck/NIRC2 J-band upper limit
  87. EP250226a/GRB 250226A: KAIT optical observations
  88. GRB 250321A: Fermi GBM Observation
  89. GRB 250321A: Swift detection of a burst
  90. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  91. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  92. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  93. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  94. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  95. GRB 250317D: EIRSAT-1 GMOD Detection
  96. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  97. GRB 250314A: ATCA radio upper limits
  98. GRB 250317B: OHP/T193 continued follow-up
  99. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  100. GRB 250317C: SVOM/GRM observation of a long burst

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