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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"

32485 results found.

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

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