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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"

32486 results found.

  1. IPN triangulation of GRB 250222A
  2. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  3. EP250302a: Mondy Continued Optical Observations
  4. EP250304a: VLT/X-shooter redshift z = 0.200
  5. EP250304a: Swift-XRT detection of a fading X-ray source
  6. EP250304a: TRT optical counterpart detection
  7. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  8. EP250304a: Global MASTER-Net observations report
  9. EP250302a: SVOM/VT optical observation
  10. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  11. EP250302a: SAO RAS optical observations
  12. EP250302a : GIT optical follow-up
  13. EP250302a: VLT/X-shooter redshift confirmation
  14. EP250225a: the candidate optical counterpart is an AGN
  15. EP250302a: Kinder optical follow-up observations
  16. EP250302a: Swift/UVOT detection
  17. EP250302a: NUTTelA-TAO Early Measurments
  18. EP250302a: optical observation from the INAF Asiago Observatory
  19. EP250302a: REM NIR upper limits
  20. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  21. EP250302a: Mondy Observations and Optical Light Curve
  22. EP250302a: VLT/MUSE optical redshift z = 1.131
  23. INTEGRAL: end of scientific operations
  24. EP250302A: VLT near-infrared observations
  25. EP250302A: VLT/X-shooter tentative redshift
  26. EP250302a: OHP/T193 optical and spectroscopic observations
  27. EP250302a: Global MASTER-Net observations report
  28. EP250302a: Xinglong F60B optical observation
  29. EP250302a: Swift-XRT observations of a fading X-ray source
  30. EP250302a: Einstein Probe detection of an X-ray transient
  31. EP250302a: SVOM/C-GFT optical observations
  32. GRB 250226A: GRANDMA Optical Observations
  33. EP250302a: Montarrenti Observatory optical detection
  34. Fermi GRB 250302A: Global MASTER-Net observations report
  35. EP250302a: FTW optical and NIR detection
  36. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  37. GRB 250225B: VLT near-infrared afterglow confirmation
  38. EP250228a: Optical observations with Kinder and Swift/UVOT
  39. Konus-Wind detection of GRB 250226A
  40. GRB 250225B: EIRSAT-1 GMOD Detection
  41. GRB 250226A: KAO Optical Upper Limit
  42. GRB 250226A: AbAO AS-32 Optical Upper Limit
  43. EP250227a: Global MASTER-Net observations report
  44. EP250223A: Upper limits from Fermi-GBM Observations
  45. EP250227a: TRT optical upper limit
  46. GRB 250225B: VLT/HAWKI near-infrared observations
  47. EP250227a: Optical upper limits with Kinder observations
  48. EP250227a: NOT optical observations
  49. EP250228a: updates on the EP observations
  50. GRB 250226A: Fermi GBM Observation
  51. EP250225a: EP-FXT follow-up observation
  52. EP250223a: J band upper limit by SYSU 80cm telescope
  53. EP250228a: Swift/XRT localisation
  54. EP250228a: Global MASTER-Net observations report
  55. GRB 250226A / EP250226a: LCO detection of the afterglow
  56. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  57. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  58. GRB 250225B: VLT/Xshooter imaging
  59. GRB 250205A / EP250205A: further radio observations with the VLA
  60. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  61. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  62. GRB 250225B: INTEGRAL SPI-ACS detection
  63. EP250225a: NOT optical candidate counterpart
  64. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  65. EP250226a / GRB 250226A: SVOM/VT optical observations
  66. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  67. EP250225a: TRT optical upper limits
  68. EP250226a/GRB 250226A: 1.6m Mephisto observations
  69. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  70. EP250226a/GRB 250226A: Kinder optical follow-up observations
  71. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  72. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  73. Fermi GRB 250226B: Global MASTER-Net observations report
  74. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  75. GRB 250225B: Fermi GBM Observation
  76. GRB 250221A: ATCA Detections and Upper Limits
  77. GRB 250225B: REM NIR upper limits
  78. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  79. Konus-Wind detection of GRB 250225B
  80. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  81. EP250223a: CrAO ZTSH optical observation
  82. GRB 250225B: VLT optical and near-infrared candidate counterpart
  83. GRB 250225B: VLT/FORS2 candidate optical afterglow
  84. GRB 250225B: SVOM/GRM observation of a long burst
  85. GRB 250226A: GECAM-B detection
  86. GRB 250221A: EP-FXT detection of the X-ray afterglow
  87. GRB 250214A: SVOM/GRM observation
  88. EP250226a/GRB 250226A: GSP detects optical counterpart
  89. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  90. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  91. EP250226a / GRB 250226A: TRT optical counterpart observation
  92. EP250226a: Global MASTER-Net observations report
  93. Swift GRB 250225B: Global MASTER-Net observations report
  94. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  95. Fermi GRB 250226A: Global MASTER-Net observations report
  96. EP250225a: Global MASTER-Net observations report
  97. EP250225a: GSP optical upper limit
  98. EP250223a: GMG Optical Observation
  99. Fermi GRB 250225A: Global MASTER-Net observations report
  100. EP250223a: GROWTH-India Telescope optical observations

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