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自然界惊奇的发现作文英文回答：The natural world is full of astonishing discoveries that never cease to amaze me. From the depths of the ocean to the highest peaks of the mountains, there are countless wonders waiting to be explored. One of the most remarkable discoveries I have come across is the phenomenon of bioluminescence.Bioluminescence is the ability of certain organisms to produce light through a chemical reaction within their bodies. It is truly a magical sight to behold. I remember one summer night when I went to a beach that was known for its bioluminescent plankton. As I walked along the shore, every step I took left behind a trail of sparkling blue lights. It was like walking on stardust. The waves crashing onto the shore were also illuminated, creating a mesmerizing spectacle. It felt as if I had stepped into a scene from a fairytale.Another astonishing discovery I encountered was the migration of monarch butterflies. Every year, millions of monarch butterflies embark on an incredible journey from Canada and the United States to Mexico. They travel thousands of miles, navigating through obstacles and adverse weather conditions. Witnessing this phenomenon firsthand was a humbling experience. I remember standing in a field, surrounded by thousands of butterflies fluttering around me. It was as if I was in the midst of a living kaleidoscope. The air was filled with the delicatefluttering of wings, and the vibrant colors of the butterflies created a breathtaking display.中文回答：自然界充满了令人惊叹的发现，这些发现总是让我感到惊奇。
英文阅读材料自然mystery 非虚构The Natural Mystery: A Non-Fiction ExplorationThe natural world is a tapestry of intricate wonders, each thread woven together to create a captivating and enigmatic landscape. Among the many mysteries that captivate the human mind, the realm of non-fiction stands as a beacon, illuminating the extraordinary within the ordinary. This essay delves into the captivating world of natural mysteries, inviting the reader to embark on a journey of discovery and unravel the hidden secrets that lie beneath the surface of our natural environment.One of the most intriguing natural mysteries lies in the depths of the ocean. The vast expanse of the seas and the creatures that inhabit them have long captured the imagination of explorers and scientists alike. From the elusive giant squid to the enigmatic Mariana Trench, the ocean's depths hold a wealth of undiscovered wonders. The recent advancements in deep-sea exploration have shed light on the diversity and complexity of marine life, revealing species that defy our understanding and challenge our preconceptions about the limits of life.Another fascinating natural mystery lies in the realm of cryptozoology – the study of creatures whose existence has not been scientifically verified. From the legendary Bigfoot to the enigmatic Loch Ness Monster, these mysterious beings have captivated the public's imagination for centuries. While some may dismiss these creatures as mere myths, the persistent sightings and tantalizing evidence have sparked the curiosity of researchers and enthusiasts alike. The pursuit of these unknown creatures has led to the discovery of new species and the reevaluation of our understanding of the natural world.The natural world is also home to a myriad of unsolved phenomena that defy our current scientific understanding. The unexplained disappearances of entire civilizations, such as the Roanoke Colony in North America, have puzzled historians and archaeologists for generations. The mysterious crop circles that appear in fields around the world have also captured the public's attention, with theories ranging from extraterrestrial activity to complex hoaxes. These unsolved mysteries serve as a reminder that there is still much to be discovered and understood about the natural world and its hidden secrets.One of the most captivating natural mysteries is the phenomenon of bioluminescence – the production of light by living organisms. From the glowing plankton that illuminate the oceans to the fireflies thatdance in the night sky, bioluminescence is a mesmerizing display of the natural world's ability to create light. Scientists have long studied the mechanisms behind this phenomenon, uncovering the complex biochemical processes that allow certain organisms to produce their own light. However, the full extent of bioluminescence in nature and its evolutionary significance remains a subject of ongoing research and exploration.Another intriguing natural mystery is the migration patterns of various species, particularly birds and marine animals. The ability of these creatures to navigate vast distances, often across continents or oceans, has long fascinated scientists and naturalists. The complex mechanisms that guide these migratory journeys, from the use of celestial cues to the perception of magnetic fields, continue to be a subject of intense study and debate. Understanding these migration patterns is not only a scientific pursuit but also crucial for the conservation of these remarkable species.The natural world is also home to a wealth of unexplained geological phenomena, such as the mysterious fairy circles found in various regions around the world. These circular patterns of bare earth, devoid of vegetation, have been observed in several arid and semi-arid regions, and their origins have been the subject of much speculation. Theories range from the influence of termites and other soil organisms to the possibility of supernatural or extraterrestrialforces. As scientists continue to investigate these enigmatic formations, they may uncover insights into the complex interactions between living organisms and the Earth's surface.In addition to these natural mysteries, the field of paleontology has also yielded a wealth of intriguing discoveries. The unearthing of fossils and the study of ancient life forms have revealed a wealth of information about the history of our planet and the evolution of life. However, many questions remain unanswered, such as the causes of mass extinctions, the emergence of new species, and the evolution of complex life forms. The ongoing search for fossils and the continued study of these ancient remains promise to uncover even more mysteries about the past and the processes that have shaped the natural world as we know it.Throughout this exploration of natural mysteries, it becomes evident that the natural world is a tapestry of wonders, each thread representing a captivating and enigmatic phenomenon. From the depths of the ocean to the heights of the sky, the natural world continues to challenge our understanding and fuel our curiosity. As we delve deeper into these mysteries, we not only uncover new insights about the world around us but also gain a deeper appreciation for the complexity and beauty of the natural realm. The pursuit of these natural mysteries is not merely an academic exercisebut a journey of wonder and discovery that holds the potential to transform our understanding of the world we inhabit.。
拉米样凯亚超星系团的英语
本文将介绍拉米样凯亚超星系团(TheRamyakyaSupercluster)。
这个超星系团位于宇宙中心附近，由多个星系团和星系群组成。
它的名字来自于梵文中的“拉米亚”和“凯亚”，分别意为“光辉的”和“宝石的”。
该超星系团最大的星系团是弗兰克林星系团 (Franklin Cluster)，它包含了数千亿颗星星。
拉米样凯亚超星系团的总质量约为10^16个太阳质量，是宇宙中最大的超星系团之一。
该超星系团还包括了其他著名星系团，如珀尔曼星系团(Perelman Cluster)、阿波罗星系团 (Apollo Cluster)和达芬奇星系团 (Da Vinci Cluster)等。
这些星系团中的许多星系和星系群都已被仔细研究和观测。
除了包含大量星系和星系团外，拉米样凯亚超星系团还是一颗活跃的星系团。
它包含了许多射电星系和类星体，这些天体能够产生高能宇宙射线和强磁场。
此外，该超星系团中还存在大量暗物质，这些暗物质对宇宙的结构和演化起着重要作用。
总之，拉米样凯亚超星系团是一个重要的天文学研究目标，它能够帮助我们更好地了解宇宙的结构和演化。
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不久的将来是充满希望和冲突的时代人类仰望星辰，寻找智慧的生命和进步的希望去超太空星际探索我很冷静，很稳定I'm calm, steady.我睡得很好，8.2小时，没有噩梦I slept well. 8.2 hours. No bad dreams.我准备好了，I am ready to go.努力做好工作，Ready to do my job to the best of my abilities. 专注于重要的事情I am focused only on the essential,排除无关因素to the exclusion of all else.做正确的决定I will make only pragmatic decisions.不让自己分心I will not allow myself to be distracted.不去想那些I will not allow my mind to linger无关紧要的事情on that which is unimportant.不要依赖其他人或事I will not rely on anyone or anything.不会被煽动犯错误I will not be vulnerable to mistakes.静息脉搏47 ，提交吧Resting BPM, 47. Submit.你的心理评估Your psychological evaluation已通过has been approved.有必要提醒As a reminder,请进行安全和设备检查……please perform any safety and equipment checks... 我一直想成为一名宇航员I always wanted to become an astronaut...为了全人类的未来for the future of mankind and all.至少我总是这么安慰自己At least, that's what I always told myself. 从外表看I see myself from the outside.我表现得……Smile, present a side.像没事一样微笑It's a performance...但是眼睛总盯在with my eye on the exit.出舱的路上Always on the exit.别碰我Just don't touch me.保重，少校。
奥司他韦、扎那米韦和玛巴洛沙韦的不良事件信号挖掘与分析Δ蒋婷婷＊，张妮，苏辉，李艳平，刘耀 #（陆军军医大学大坪医院药剂科，重庆 400042）中图分类号 R969.3文献标志码 A 文章编号 1001-0408（2024）06-0739-05DOI 10.6039/j.issn.1001-0408.2024.06.18摘要目的挖掘3种抗甲型流感病毒药物（奥司他韦、扎那米韦、玛巴洛沙韦）的不良事件（ADE）信号，为临床安全用药提供参考。
方法收集美国FDA不良事件报告系统（FAERS）2004年第1季度至2022年第3季度上报的奥司他韦、扎那米韦、玛巴洛沙韦ADE数据，采用报告比值比（ROR）法进行数据挖掘，评估指定医疗事件（DME），利用《国际医学用语词典》（25.0版）药物ADE术语集中的系统器官分类（SOC）进行分类统计。
结果分别检索到奥司他韦、扎那米韦、玛巴洛沙韦ADE报告12636、1749、1283例，分别累及26、16、17个SOC。
奥司他韦与睡惊症、异常行为、幻觉、谵妄的关联性较强；扎那米韦涉及的异常行为、谵妄、语无伦次、意识状态改变信号强度突出；玛巴洛沙韦与缺血性结肠炎、出血性膀胱炎、多形性红斑、黑便的关联性较强。
3种药物的DME 均检出多形性红斑，且信号较强。
结论临床应用奥司他韦等3种药物时，除关注常见ADE外，还应加强关注药品说明书中未提及的ADE。
对于奥司他韦应警惕急性肾损伤、暴发性肝炎，定期监测患者的肝肾功能；对于扎那米韦应警惕与呼吸系统相关的ADE，包括急性呼吸窘迫综合征、呼吸衰竭，并密切关注患者的呼吸状况；对于玛巴洛沙韦应警惕多形性红斑、横纹肌溶解等ADE。
关键词抗甲型流感病毒药物；奥司他韦；扎那米韦；玛巴洛沙韦；信号挖掘；不良事件Signal mining and analysis of adverse events of oseltamivir， zanamivir and baloxavir marboxilJIANG Tingting，ZHANG Ni，SU Hui，LI Yanping，LIU Yao（Department of Pharmacy，Daping Hospital， Army Medical University， Chongqing 400042， China）ABSTRACT OBJECTIVE To provide reference for safe drug use in clinic by mining the adverse drug events （ADE）of 3kinds of anti-influenza A virus drugs （oseltamivir，zanamivir，baloxavir marboxil）.METHODS The ADE data of oseltamivir，zanamivir and baloxavir marboxil were collected from the FDA adverse event reporting system （FAERS） between the first quarter in 2004 and the third quarter in 2022，and mined by using reporting odds ratio （ROR）method. The designated medical events （DME）were estimated. The system organ class （SOC）in the Medical Dictionary for Regulatory Activities （MedDRA，version 25.0）was used for the classification and statistics of drug ADE terminology.RESULTS A total of 12636，1749and 1283ADE reports were retrieved for oseltamivir， zanamivir and baloxavir marboxil， involving 26，16 and 17 SOCs， respectively. Oseltamivir was strongly associated with sleep terror，abnormal behavior，hallucination and delirium. Zanamivir was implicated in abnormal behavior，delirium，incoherence，and altered state of consciousness with prominent signal intensity. Baloxavir marboxil was strongly associated with ischemic colitis，hemorrhagic cystitis，erythema multiforme and melaena. Erythema multiform was detected in the DME of three drugs with strong signals.CONCLUSIONS When clinically administering the three drugs，it is crucial to pay close attention to both common adverse reactions and those ADEs that are not explicitly mentioned in the drug instructions. For oseltamivir，clinicians should exercise caution due to the potential risk of acute kidney injury and fulminant hepatitis，necessitating regular monitoring of the patient’s liver and kidney function. When prescribing zanamivir， caution should be exercised due to ADEs related to the respiratory system，including acute respiratory distress syndrome and respiratory failure，necessitating close monitoring of the patient’s respiratory status. Similarly，for baloxavir marboxil，clinicians should be vigilant for potential ADEs such as erythema multiforme and rhabdomyolysis.KEYWORDS anti-influenza A virus drug； oseltamivir； zanamivir； baloxavir marboxil； signal mining； adverse drug event甲型流感病毒是流行性感冒的主要病原体之一，其传播速度快、传染性强，每年约7亿人感染，导致近60万人死亡，已成为人类面临的重大公共卫生问题[1]。
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济南2024年03版小学6年级下册英语第6单元测验卷[有答案]考试时间：80分钟（总分:100）A卷一、综合题(共计100题)1、填空题：The ______ (物种) diversity is crucial for a healthy ecosystem.2、填空题：The _____ (火烈鸟) is pink and stands on one leg.3、How many hours are there in a day?A. 12B. 24C. 36D. 48答案：B4、填空题：The ______ (阳光照射) plays a role in photosynthesis.5、填空题：I want to _______ (学会) playing the piano.6、What is 20 + 30?a. 40b. 50c. 60d. 70答案:b7、听力题：The Earth’s ______ is responsible for its magnetic f ield.8、What do you call a person who repairs computers?A. TechnicianB. EngineerC. BuilderD. Designer答案:A9、What is the capital of Russia?A. St. PetersburgB. MoscowC. KievD. Minsk答案: B10、听力题：We have a _____ (活动) for Earth Day.11、What is the name of the famous rock band known for hits like "Hey Jude"?A. The Rolling StonesB. The BeatlesC. QueenD. Pink Floyd答案：B12、填空题：I have a toy _____ that can dance.13、听力题：The capital of Senegal is __________.14、听力题：Saltwater is an example of a ______.15、填空题：We have a ______ (愉快的) celebration for achievements.16、填空题：The ancient Egyptians created beautiful _____ for their gods.17、What do we call the melting of snow and ice?A. PrecipitationB. EvaporationC. RunoffD. Thawing答案:D18、填空题：A __________ day is perfect for going to the zoo. (温暖的)19、听力题：A reaction that produces a gas and a solid is called a ______ reaction.20、填空题：The _______ (Peasants’ Revolt) occurred in England in 1381.21、填空题：The ______ (鲸鱼) is known for its size and beauty.22、听力题：The chemical symbol for technetium is ______.23、填空题：Birds can ______ (飞) in the sky.24、听力题：Space exploration began in the ______ century.25、填空题：My uncle is a __________ (音乐家).26、听力题：My dad likes to go on ____ (hiking) trips.27、填空题：________ (果醋) is made from fruit.28、填空题：I enjoy playing ________ (棋类) with my friends.29、听力题：A solution is a mixture where one substance ______ in another.30、What do we call the act of trying out new things?A. ExperimentingB. TestingC. SamplingD. All of the Above答案：D31、What is the term for a person who studies the oceans?A. OceanographerB. Marine BiologistC. GeologistD. Environmentalist答案:A32、What do you call a person who works with wood?A. CarpenterB. ElectricianC. PlumberD. Mason答案: A33、What is the capital of Italy?A. RomeB. VeniceC. FlorenceD. Milan答案: A. Rome34、What do we call the effect of the Earth's rotation on weather patterns?A. Coriolis EffectB. Trade WindsC. Jet StreamD. Ocean Currents35、听力题：The ________ (strategy) guides our actions.36、What is the main ingredient in salad?A. MeatB. VegetablesC. FruitsD. Grains答案：B37、What do we call a group of dolphins?A. SchoolB. PodC. FlockD. Colony答案:B. Pod38、听力题：A _______ is a large area of land that is covered with trees.39、听力题：In chemistry, we use ______ to represent elements.40、What is the color of milk?A. WhiteB. YellowC. BlueD. Green41、What is the main ingredient in a Caesar salad?A. LettuceB. SpinachC. KaleD. Arugula答案:A. Lettuce42、Which of these is a primary color?A. PurpleB. GreenC. BlueD. Orange答案:C43、What color is a ripe strawberry?A. BlueB. YellowC. RedD. Green答案:C44、What is the opposite of ‘easy’?A. SimpleB. DifficultC. HardD. Challenging45、听力题：The ______ helps us learn about social studies.46、选择题：What is 8 + 2?A. 10B. 11C. 12D. 1347、填空题：I enjoy making ______ (贺卡) for my friends on their birthdays. It’s a personal touch they appreciate.What do we call the time of year when it’s very cold?A. SpringB. SummerC. WinterD. Autumn49、听力题：The __________ is essential for protecting water sources.50、听力题：My ______ is an expert in technology.51、What is the name of the fairy tale character who had a magic mirror?A. CinderellaB. Snow WhiteC. RapunzelD. Belle52、听力题：The snowman has a ______ (carrot) nose.53、填空题：I love to have tea parties with my ________ (玩具名) and pretend we are all friends.54、填空题：The _____ (水果收成) happens in late summer.55、听力题：My brother likes to play _____ (basketball/football).56、听力题：She is good at ______. (dancing)57、填空题：A _____ (小马) can be very gentle around children.58、What is the capital city of El Salvador?A. San SalvadorB. Santa AnaC. San MiguelD. Sonsonate59、听力题：A __________ is a small furry animal that often lives in burrows.The Age of Exploration began in the _______ century.61、填空题：I want to help protect the _______ (环境). It’s important for future _______ (世代).62、听力题：A saturated solution contains the maximum amount of ______.63、听力题：The chemical formula for magnesium sulfate is ______.64、What do we call a young deer?A. FawnB. CalfC. KidD. Pony65、What is the main gas in the atmosphere?A. OxygenB. NitrogenC. Carbon DioxideD. Hydrogen答案：B66、填空题：The discovery of ________ led to significant advances in medicine.67、填空题：I enjoy doing puzzles and brain teasers to challenge my ________ (思维).68、填空题：The ______ (金鱼) swims in circles, looking for food.69、听力题：He plays _____ (football/basketball) on the team.70、填空题：A _____ (植物园) showcases different species.71、听力题：My uncle is very ________.72、填空题：I enjoy visiting the __________ with my family. (博物馆)My friend has a ___ (小宠物), which is a cute rabbit.74、What is the name of the famous scientist known for his work on gravity?A. Isaac NewtonB. Albert EinsteinC. Galileo GalileiD. Johannes Kepler答案: A75、填空题：A _____ is a piece of land that juts out into the sea.76、ts are ________ (药用) and help heal. 填空题：Some pla77、Which animal is known for its ability to change color?A. ChameleonB. ElephantC. GiraffeD. Zebra78、填空题：Understanding the role of plants in our environment is crucial for ______. (了解植物在环境中的作用对保护至关重要。
没有观察力的旅行者是没有翅膀的鸟英语作文In the vast world of travel, observation plays a pivotal role in enriching the experience. Without keen observation skills, a traveler is akin to a bird without wings -limited in their ability to truly explore and appreciate the wonders that surround them.When we embark on a journey, our senses become our most valuable companions. The sights, sounds, smells, tastes, and textures of each place tell its unique story. It is through careful observation that we can begin to unravel this narrative, delving into the heart of a destination and immersing ourselves in its culture.Observation allows us to notice the tiny details that might otherwise go unnoticed. The subtle nuances hidden within a bustling marketplace or the delicate brushstrokes of an ancient painting can offer insights into local customs and traditions. These seemingly inconspicuous observations are like puzzle pieces that come together to create a holisticunderstanding of a place.Moreover, observation invites curiosity and engagement with our surroundings. Instead of merely passing through a city or town as if on autopilot, an observant traveler takes the time to engage with locals, ask questions, and dig deeper beneath the surface. This leads to meaningful connections that can provide invaluable insights into the community's way of life.Interestingly, observation goes beyond visual perception.It involves actively listening to conversations and absorbing the intangible ambiance of a place. The cadence of language spoken by locals, their facial expressions as they interact with one another - these subtletiescontribute to our understanding of local cultures and help us forge connections on a human level.However, even though observation is an essential tool for enhancing our travel experiences, it requires conscious effort and practice. In today's fast-paced world filled with distractions like smartphones and social media, it iseasy to overlook opportunities for observation. We must consciously choose to be present in each moment during our travels - allowing ourselves the opportunity to fully immerse in new environments.In conclusion, being an observant traveler is like having a pair of wings that allow us to soar through new experiences and gain a deeper appreciation for the world around us. By sharpening our observation skills and cultivating a senseof mindfulness, we can uncover hidden facets of adestination and create meaningful connections along the way. So let us spread our wings and embark on journeys filledwith wonder, curiosity, and an unquenchable thirst for discovery.旅行世界浩瀚无垠，观察力在充实旅行体验中扮演着重要角色。
没有观察力的旅行者是没有翅膀的鸟英语作文As a traveler, observation is the key to unlocking the beauty and secrets of the world. Without a keen sense of observation, a traveler is like a bird without wings,unable to soar and explore the wonders of the world.Observation allows us to fully immerse ourselves in the experience of travel, to appreciate the small details and nuances that make each destination unique. It is through observation that we can truly understand and appreciate the culture, history, and natural beauty of the places we visit. Without it, our travels would be shallow and unfulfilling.When we observe, we notice the way the sunlight filters through the leaves of a jungle, the way the waves crash against the shore, the way people interact and go abouttheir daily lives. These observations enrich ourexperiences and allow us to form a deeper connection withthe places we visit.Observation also plays a crucial role in ensuring our safety and well-being while traveling. By being observant,we can identify potential dangers, navigate unfamiliar environments, and make informed decisions. Without this ability, we may find ourselves in precarious situations or miss out on important opportunities.In conclusion, observation is an essential skill for any traveler. It enables us to fully appreciate and understand the world around us, enhances our travel experiences, and ensures our safety. Without it, we are truly like birds without wings, unable to fully spread our wings and explore the world.作为一个旅行者，观察力是解锁世界美丽和秘密的关键。
The Traveler Without Observation: A BirdWithout WingsIn the vast canvas of life, travelers are akin to birds in flight, each with their unique journey and destination. However, a traveler who fails to observe their surroundings is like a bird without wings, unable to fully embrace the beauty and wonders of the world. Observation is the key to unlocking the secrets of any destination, whether it be the intricate details of a foreign culture or the subtle nuances of nature.Observing the world around us enriches our understanding and appreciation of it. It is through observation that we gain insights into the lives of others, understanding their customs, traditions, and values. It is through observation that we become aware of the intricate details of nature, from the beauty of a sunset to the intricate dance of insects. Observation opens our eyes to the world, making us more aware and appreciative of its wonders.For travelers, observation is not just a skill, it is a necessity. It is through observation that we can trulyimmerse ourselves in a new culture, understanding its people and places. It is through observation that we can appreciate the beauty of a destination, from the grandeur of its landmarks to the quiet charm of its streets. Without observation, a traveler would miss out on the rich tapestry of experiences that make traveling so enriching and rewarding.Moreover, observation helps us connect with the worldin a deeper and more meaningful way. It allows us to understand the stories behind places and people, to feel the pulse of a destination and to connect with it emotionally. Observation helps us create meaningful connections with the world, making our travels more enriching and fulfilling.In conclusion, observation is the wing that powers the traveler's journey. It is through observation that we can truly embrace the beauty and wonders of the world, understanding its people, places, and stories. Without observation, a traveler would be like a bird without wings, unable to fully explore and appreciate the vast canvas of life. Let us all embrace the power of observation and soarthrough the skies of life, experiencing the world in a deeper and more meaningful way.**没有观察的旅行者：没有翅膀的鸟**在生命的广阔画卷中，旅行者如同飞翔的鸟儿，每个人都有自己独特的旅程和目的地。
寻找地球以外的生命有什么意义英语作文Exploring the Significance of Searching for Extraterrestrial LifeThe search for extraterrestrial life has captivated the human imagination for centuries. As we gaze into the vast expanse of the cosmos, the possibility of discovering intelligent life beyond our planet has become an enduring fascination. This endeavor, often referred to as the search for extraterrestrial intelligence (SETI), holds immense significance that extends far beyond mere scientific curiosity.One of the primary motivations behind the search for extraterrestrial life is the profound implications it could have for our understanding of the universe and our place within it. The discovery of even the most primitive forms of life beyond Earth would revolutionize our perception of the cosmos, challenging the long-held belief that Earth is the sole bastion of life in the universe. Such a revelation would shatter the anthropocentric view that has dominated much of human thought and history, forcing us to reconsider our own significance and the uniqueness of our existence.Moreover, the search for extraterrestrial life holds the potential touncover valuable insights into the origins and evolution of life itself. By studying the conditions and mechanisms that give rise to life in other planetary systems, scientists could gain a deeper understanding of the fundamental processes that underlie the emergence and development of living organisms. This knowledge could have far-reaching implications for fields such as biology, astrobiology, and evolutionary science, potentially leading to breakthroughs in our comprehension of the origins of life on Earth.The search for extraterrestrial life also carries immense philosophical and existential significance. The discovery of intelligent life beyond our planet would force us to confront profound questions about the nature of consciousness, the universality of intelligence, and the possibility of shared values and experiences across vastly different civilizations. Such an encounter could challenge our most deeply held beliefs and assumptions about the human condition, our place in the cosmic order, and our relationship with the rest of the universe.Furthermore, the search for extraterrestrial life holds the potential to inspire and unite humanity in unprecedented ways. The pursuit of this grand scientific endeavor has the power to transcend political, cultural, and ideological boundaries, fostering a shared sense of wonder and a collective effort to explore the unknown. The discovery of extraterrestrial life, or even the mere possibility of its existence, could serve as a catalyst for global cooperation, as nations andindividuals come together to unravel the mysteries of the universe.Beyond the scientific and philosophical implications, the search for extraterrestrial life also holds profound implications for our own future as a species. The discovery of advanced civilizations beyond Earth could provide invaluable insights into the challenges and opportunities that may lie ahead for humanity. By studying the technological, social, and environmental trajectories of other intelligent species, we may gain crucial perspectives on the sustainable development of our own civilization, potentially guiding us towards a more harmonious and resilient future.Moreover, the search for extraterrestrial life could have significant practical applications, leading to advancements in fields such as communication technology, space exploration, and the development of new materials and energy sources. The technological innovations and scientific breakthroughs that arise from this endeavor could have far-reaching benefits for humanity, improving our quality of life and expanding the boundaries of human knowledge and capabilities.In conclusion, the search for extraterrestrial life holds immense significance that transcends the realm of scientific curiosity. It has the potential to revolutionize our understanding of the universe, challenge our most fundamental beliefs, inspire global cooperation, and guide us towards a more sustainable and resilient future. As wecontinue to explore the vast expanse of the cosmos, the search for extraterrestrial life remains a pursuit of profound importance, one that holds the power to transform our very conception of ourselves and our place in the grand tapestry of the universe.。
a r X i v :a s t r o -p h /9702053v 1 5 F eb 1997Discovery of a non-blazar gamma-ray transient near the Galactic plane:GRO J1838–04M.Tavani 1,R.Mukherjee 2,3,J.R.Mattox 4,J.Halpern 1D.J.Thompson 5,G.Kanbach 6,W.Hermsen 7,S.N.Zhang 8,R.S.Foster 91.Columbia Astrophysics Laboratory,Columbia University,New York,NY RA,NASA/GSFC,Code 610.3,Greenbelt,MD 20771.3.Physics Dept.,McGill University,3600University St.,Montreal,Que,H3A 2T8,Canada.4.Astronomy Dept.,Boston University,725Commonwealth Avenue,Boston,MA 02215.5.Code 661,NASA Goddard Space Flight Center,Greenbelt,MD 20771.6.MPE,Giessenbachstrasse,Garching bei Munchen,D-85748,Germany.7.SRON-Utrecht,Sorbonnelaan 2,3584CA Utrecht,The Netherlands.8.Universities Space Research Association,NASA/MSFC,Huntsville,AL,35812.9.Code 7210,Naval Research Laboratory,Washington,DC 20375.ReceivedABSTRACTWe report the discovery of a remarkable gamma-ray transient source near the Galactic plane,GRO J1838–04.This source was serendipitously discovered by EGRET in June1995with a peak intensity of∼(4±1)×10−6ph cm−2s−1 (for photon energies larger than100MeV)and a5.9σsignificance.At that time,GRO J1838–04was the second brightestγ-ray source in the sky.A subsequent EGRET pointing in late September1995detected the source ataflux smaller than its peak value by a factor of∼7.We determine that no radio-loud spectrally-flat blazar is within the error box of GRO J1838–04.We discuss the origin of theγ-ray transient source and show that interpretations in terms of AGNs or isolated pulsars are highly problematic.GRO J1838–04 provides strong evidence for the existence of a new class of variable gamma-ray sources.Subject headings:gamma-rays:observations;galaxies:active;stars:neutronSubmitted to the Astrophysical Journal Letters:December16,1996Accepted:February3,19971.IntroductionEGRET has discovered∼40unidentified gamma-ray sources concentrated near the Galactic plane(Thompson et al.1995,1996).The nature of these unidentifiedγ-ray sources is currently unknown.Of particular interest are time-variable EGRET sources with no obvious radio-loud blazar within their error boxes.Isolated pulsars similar to the Crab, Vela,and Geminga pulsars have an approximately constantγ-rayflux(e.g.,Ramanamurthy et al.1995)and cannot account for the existence of variable sources.We report here the discovery of a strongly variableγ-ray source,GRO J1838–04. This source was detected during an observation of afield which included the Galactic plane(Galactic longitude between l=17◦and l=32◦).Thisfield contains other EGRET sources studied by our group,2EG J1813–12and2EG J1828+01(Tavani et al.1997).Our search for time variableγ-ray sources near the Galactic plane is motivated by models of high-energy emission from Galactic sources(Tavani1995).However,the possible detection by EGRET of extragalactic objects near the Galactic plane cannot a priori be excluded. We consider here blazars as plausible candidates ofγ-ray emission(e.g.,Montigny et al. 1995,Hartman et al.1996,Mattox et al.1996,hereafter M96).pton GRO observations of GRO J1838–04The source GRO J1838–04was identified processing EGRET data of the CGRO viewing period(VP)423(June20-30,1995).The source is located near the Galactic plane in afield centered at Galactic coordinates l=27.31◦and b=+1.04◦with an elongated error box(99%confidence)of major axis∼1.4◦and minor axis∼0.8◦.The averageγ-rayflux above100MeV for the whole VP423isΦ=(3.3±0.7)·10−6ph cm−2s−1.The strongly time variable nature of theγ-ray emission from GRO J1838–04is evident from the EGRET light curve shown in Fig.1.As can be seen in Fig.1,EGRET pointed in the direction of GRO J1838–04about16times during a period of4years.Each exposure was typically1-2week long.The source was not detected by EGRET during all of the previous observations except during VP334.0and the combined VPs421and422withdetections above the3σlevel.Aχ2test for variability yields a probability of0.0011that all the EGRET observations of GRO J1838–04are consistent with a constantflux.What makes GRO J1838–04remarkable is the intensity level reached during theγ-rayflare,with a peakflux above100MeV of(4.0±1.1)·10−6ph cm−2s−1reached during the last3.5-day interval of VP423.Theγ-ray luminosity for isotropic emission corresponding to the peak flux is Lγ≃7.2×1034d2kpc erg s−1,where d kpc is the source distance in kpc.Fig1(b)shows the details of the VP423EGRET observations for three3.5-day intervals.This is among the most intenseγ-ray transients ever detected,with aγ-rayflux comparable with that of the Geminga pulsar and of AGNflare peak intensities as for3C279(z=0.538)(Kniffen et al.1993)and0528+134(z=2.07)(Mukherjee et al.1996).Theγ-rayflare in June1995 is evident in Fig.1(a),and theγ-rayflux substantially decreased before the next EGRET pointing at the source in late September1995.We notice that prior to June1995the source was detected only once with marginal significance(∼3.2σ)during the period July18-25 1994(VP334).Fig.1(b)clearly shows the rapid time variability within a3.5-day timescale interval.EGRET detected during VP423the rising part of aflare that presumably reached aγ-rayflux level even higher than the peakflux of∼4·10−6ph cm−2s−1.The EGRET spectrum above30MeV during the peak emission is consistent with a power-law photon spectrum of the form F(E)=k(E/E o)−αwith k=(3.2±0.6)×10−9ph cm−2s−1MeV−1,α=2.09±0.18and E o=288MeV.Analysis of COMPTEL data for VP423in the standard energy intervals0.75-1MeV, 1-3MeV,3-10MeV and10-30MeV did not show an excess in the maximum likelihood skymaps at the position of GRO J1838–04.The2σupper limit for the energy interval 10-30MeV is3.5×10−5ph cm−2s−1,and for the most sensitive interval of1-3MeV, 3.2×10−4ph cm−2s−1.These upper limits are roughly consistent with the extrapolation of the EGRET spectralfit for energies above100MeV,as shown in Fig.2.We also searched the COMPTEL maximum likelihood maps of CGRO phase1-4periods in the four standard energy intervals for excess emission at the position of GRO J1838–04.It is interesting to note that single source-like features appear during VP334.0(1-3MeV,3-10MeV)and during VP302.3(3-10MeV)with a significance between3.0and3.7σ.However,detections cannot be claimed,since in the standard COMPTEL maximum likelihood maps theunderlying Galactic diffuse emission has not yet been included as a background component.A sufficiently accurate model of the diffuse emission in the COMPTEL energy range is not yet available.A proper modelling of the background component most likely will reduce the detection significance for VP334.0and VP302.3.BATSE can detect hard X-ray emission from transient sources with a daily sensitivity of∼75mCrab(20-100keV)(Harmon et al.1993).We determined that no hard X-ray emission from the direction of GRO J1838–04was detected during the VP423interval. For the whole duration of VP423,the3σupper limit in the20-100keV energy band is ∼24mCrab.Fig.2shows the multi-instrument CGRO spectrum of GRO J1838–04during VP423.3.Search for counterpartsFig.3shows the radio sources in thefield of GRO J1838–04as determined bythe Galactic plane survey at20cm(Helfand et al.1992).The EGRET error box of GRO J1838–04is marked in Fig.3by the solid elliptical curve.We note the presence of several double-lobe sources(presumably extragalactic jet sources with jet axis pointing away from the line of sight),the radio pulsars PSR B1831–04and PSR B1834–04(Taylor, Manchester&Lyne1993),and the center-filled supernova remnant SNR27.8+0.6(Reich et al.1984).No spectrally-flat bright radio source with blazar characteristics is within the 99%confidence error box of GRO J1838–04.We observed the brightest radio source in the error box(27.920+0.977,source‘A’of Fig.3)at the Green Bank radio interferometer at 2.25and8.3GHz during the period December141995-January131996.We determined that this source has a constantflux(∼500mJy at2.2GHz)and a steep radio spectral indexαr≃−1.The inferred radioflux at5GHz is S5≃0.25Jy.Other radio sources within the error box are even fainter than27.920+0.977.These radio properties are quite different from those of blazars associated with high confidence with EGRET sources(Montigny et al.1995,Thompson et al.1995,M96).Typically brightγ-ray blazars are strong(S5>∼1Jy) and spectrallyflat(αr>∼−0.5)radio sources.PSR B1831–04and PSR B1834–04appear to be radio pulsars with no anomalous emission.Their estimated distances are2.3and4.6kpc,respectively(Taylor et al.1993). Their relatively small spindown luminosities(1032.5and1033.1erg s−1)are well below the γ-ray luminosity of GRO J1838–04put at their distances(even for100%efficiency of conversion of spindown power into gamma-ray emission and a10%γ-ray beaming factor).SNR27.8+0.6is estimated to be at a∼2kpc distance and of age35,000-55,000years (Reich et al.1984).No pulsar is known to be associated with the remnant which appears to be of a center-filled plerionic type from its radio extended and core emission.We determined that three X-ray sources in the ROSAT all-sky survey(RASS)database are within the99%confidence error box of GRO J1838–04.We list here the names specifying their coordinates(equinox J2000):RXSJ183745.2-044829,RXSJ183824.1-045034, RXSJ183747.4-035951.None of these is associated with the radio sources of Fig.3.For a typical countrate of0.025cts s−1and column density N H=1.23·1022cm−2,the X-ray energyflux is estimated to be5.3·10−12erg cm−2s−1(0.1-2.4keV band)for an assumed photon index of–2(Voges1996).The source RXSJ183745.2–044829is coincident(5arcsecs) with the bright F2star(m≃7)HD171954.The other two RASS sources have no known counterparts.We also checked that no IRAS sources are within the99%confidence error box of GRO J1838–04.4.DiscussionWe considerfirst the possibility that GRO J1838–04is an extragalactic source of the type detected by EGRET at high Galactic latitudes.Our motivation is that theγ-ray time variability andflux levels of GRO J1838–04are similar to those occasionally detected from AGNs.There are four blazars which EGRET has observed withγ-rayfluxes as large as GRO J1838–04(3C279,PKS1622-297,CTA26,&PKS0528+134).The solid angle subtended by the Galactic plane sky area within±2◦of Galactic latitude is∼0.4steradians. The probability offinding a brightγ-ray blazar is in this case∼4×0.4/4π≃0.1.However, we note that all bright blazars with a peakγ-rayflux larger than10−6ph cm−2s−1(E>100MeV)have an average5GHz radioflux in excess of1Jy(M96).From the lack of such a counterpart for GRO J1838–04,the probability that this source is a blazar is substantially smaller than this estimate.Indeed,if the same fraction f q of spectrally-steep AGNs with S5<∼0.25Jy were producingγ-rayflares as for radio-loud and spectrally-flat AGNs with S5>∼1Jy(f l∼0.1), EGRET would have revealed aγ-ray sky substantially different from the observed one.This can be quantified because of very strong evidence for a correlation between the peakγ-ray flux of blazars and the average5GHz radioflux(M96).EGRET has detected ten blazars with a peakγ-rayflux above10−6ph cm−2s−1at E>100MeV,and all of these sources have an average S5>1Jy.We deduce thatγ-ray blazars with S5∼0.25Jy(as source‘A’)are at least a factor of4(at90%confidence)less common than EGRET blazars with S5∼1Jy. Also,the great majority of blazars detected by EGRET and simultaneously monitored in the radio are spectrally-flat.Only two blazars out of a total of41sources have indices αr∼−0.7from non-simultaneous radio measurements(M96).Therefore,γ-ray blazars with steep indices(as source‘A’)are at least a factor of8(at90%confidence)less common than EGRET blazars withflat indices.The probability that GRO J1838–04can be identified with source‘A’as a blazar is less than0.003.Identification of a blazar with the weaker radio sources of Fig.3is even less likely.EGRET observations require f q<∼0.03f l.We note that at theγ-rayflux level near10−6ph cm−2s−1,there is no lack of sensitivity for EGRET observations near the Galactic plane.Thus,we conclude(99.7%confidence) that GRO J1838–04is not a brightγ-ray blazar of the kind usually detected by EGRET. We cannot exclude the possibility that a new type ofγ-ray AGN of unusual properties is the counterpart of GRO J1838–04.However,based onfive and one half years of EGRET observations of AGNs,it is highly improbable that afirst detection of such a newγ-ray AGN would occur near the Galactic center.Most likely,we are dealing with a Galactic phenomenon.In principle,both binary and isolated compact objects in the Galaxy might produce variableγ-ray emission.Mechanisms for binary systems include:(1)special accretion and radiation processes onto the surface of a neutron star or black hole,(2)variableshock-powered synchrotron emission from a relativistic pulsar wind termination shock in a binary system or supernova remnant(e.g.,Tavani&Arons,1997);(3)inverse Compton ‘glowing’of relativistic particle winds(e.g.,a pulsar wind)subject to cooling in time variable photon background baths(as close to periastron of a massive binary)(Tavani 1995);(4)particle acceleration and radiation in non-relativistic colliding winds of a massive binary.Isolated compact objects might produce gamma-rays because of:(5)(6)internal or quake-driven outburst activity from a neutron star.Model(1)can be relevant for a transient X-ray source showing sporadic accretion episodes.Among the brightest X-ray transients detected by BATSE above100mCrab,two sources show relativistic jet radio emission,GRS1915+105(Mirabel&Rodriguez1994),and GRO J1655–40(Hjellming& Rupen1995;see also Harmon et al.1995,Foster et al.1996).A gamma-rayflare can be produced by transient acceleration processes along the jet in a hypothetical source similar to GRS1915+105and GRO J1655-40.However,the lack of significant hard X-ray emission from the direction of GRO J1838–04as determined by BATSE argues against the existence of an object similar to known X-ray transients with jet emission.Both GRS1915+105and GRO J1655–40show hard X-ray outbursts of intensity one-two orders of magnitude larger than the BATSE upper limit for GRO J1838–04.Models(2-4)based on optically thin emission are in principle plausible,since they refer to a population of binaries which might exist in the Galactic plane and to physical processes known to occur in pulsar binaries (Tavani1995).We note that changes in the mass outflow or orbital parameters influencing the high-energy emission of Galactic binaries can take place within a few weeks/months. However,in the absence of a binary counterpart of GRO J1838–04,this interpretationis at the moment hypothetical.Model(5)requires the existence of aγ-ray pulsar with extreme time-variable magnetospheric emission.The low-power radiopulsars known in the GRO J1838–04field,PSR B1831–04and PSR B1834–04are not known for any anomalous emission or glitching activity.Their spindown luminosities are smaller by one-two orders of magnitude than the requiredγ-ray luminosity.Any new transientγ-ray pulsar at the distance d kpc is required from our observations to have a spindown luminosity larger than ∼7·1035d2kpc b(ε/0.1)−1erg s−1,whereεis the efficiency of spindown conversion intoγ-rays and b theγ-ray beaming factor.Model(6)requires outburst conditions and durations neverobserved before in compact stars.We notice that at the distance of2kpc,a compact object originating from SNR27.8+0.6and moving with a velocity of∼330km s−1for50,000years would reach an angular distance of∼0.5◦from the remnant’s center corresponding to the centroid of theγ-ray error box of GRO J1838–04.5.ConclusionsWe determined that GRO J1838–04is a strongly variableγ-ray source and that no blazar counterpart exists within its99%confidence error box.If GRO J1838–04is of extragalactic origin,then it shows a new manifestation of active galaxies.Any counterpart is shown here to have radio properties substantially different from those of blazars detected by EGRET.The lack of EGRET detections of low radio luminosity(and non-spectrally-flat) AGNs strongly constrains any extragalactic origin of GRO J1838–04.A Galactic origin of GRO J1838–04is not as yet supported by plausible counterparts.Additional radio,X-ray and optical observations of the GRO J1838–04error box are required to gain information on its counterpart.A search for binary systems and energetic pulsars in the GRO J1838–04 error box will be valuable in constraining the nature of the source.Our results suggest the existence of a new class ofγ-ray sources in addition to isolated pulsars and radio-loud blazars.A search for transientγ-ray sources near the Galactic plane by current and future high-energy missions is strongly encouraged.We thank D.Helfand for exchange of information on unpublished data of Galactic plane radio surveys and M.Ruderman for discussions.We are grateful to W.Voges for his analysis of RASS data.Research partially supported by the NASA CGRO Guest Investigator Program(grant NAG5-2729).Radio astronomy at the Naval Research Laboratory is supported by the Office of Naval Research.6.ReferencesFoster,R.S.,Waltman,E.B.,Tavani,M.,Harmon,B.A.&Zhang,S.N.,1996,ApJ,467, L81.Harmon,B.A.,et al.,1993in2nd Compton Observatory Symposium,AIP Conf.no.304,p.210.Harmon,B.A.,et al.,1995,Nature,374,703.Hartman,R.C.,et al.,1996,ApJ,461,698.Helfand,D.J.,et al.,1992,ApJS,80,211.Hjellming,R.M.&Rupen,M.P.,1995,Nature,375,464.Hunter,S.,et al.,1996,submitted to ApJ.Kniffen,D.,et al.,1993,ApJ,411,133.Mattox,J.R.,Schachter,J.,Molnar,L.,Hartman,R.C.,Patnaik,A.R.,1996,submitted to ApJ(M96).Mirabel,I.F.,&Rodriguez,L.F.,1994,Nature371,46.Montigny,C.V.,et al.,1995,ApJ,440,525.Mukherjee,R.et al.,1996,ApJ,470,831.Ramanamurthy,P.V.,et al.,1995,ApJ,450,791.Reich,W.,Furst,E.&Sofue,Y.,1984,A&A,133,L4.Ruderman,M.,1996,private communication.Tavani,M.,1995,in The Gamma-Ray Sky of SIGMA and GRO,eds.M.Signore,P.Salati,G.Vedrenne(Dordrecht:Kluwer),p.181.Tavani,M.&Arons,J.,1997,ApJ,in press.Tavani,M.,et al.,1997,to be submitted to ApJ.Taylor,J.H.,Manchester,R.N.&Lyne,A.,1993,ApJS,88,529. Thompson,D.J.,et al.,1995,ApJS,101,259.Thompson,D.J.,et al.,1996,ApJS,107(Nov.1996).Voges,W.,1996,private communication.Figure CaptionsFigure1(a)–Time history ofγ-rayflux detected by EGRET from thefield containing GRO J1838–04.TJD is the truncated Julian date(JD),TJD=JD–2,400,000.0.1σflux errors and2σupper limits are reported,the upper limits being shown as downward arrows. The time interval is from April1991through the end of September1995.EGRET data for VPs421and422have been combined.(b)Time history for the VPs421,422,423and429, spanning a time interval from June6until September27,1995.EGRET data for VP423 have been divided into three3.5-day intervals(1σflux error bars are shown).Figure2–Multi-instrument CGRO spectrum of GRO J1838–04during the period of maximumγ-ray emission(VP423,June20-30,1995);2σupper limits are marked as downward arrows.Figure3–Radio sources of the Galactic plane survey at20cm(Helfand et al.1992) with the99%confidence EGRET error box of GRO J1838–04marked by the solid ellipse.The diamond’s size is proportional to the radioflux at20cm:source A,738mJ; source B,264+99mJ;source C,23+27mJy;source D,83+377mJy;source E,69mJy; source F,68+41mJy.Crosses indicate the positions of the radiopulsars PSR B1831-04 and PSR B1834-04.The dashed line circle approximates the extension of the supernova remnant G27.8+0.6at2.6GHz(Reich et al.1984).Filled circles give the positions of the RASS sources.No spectrally-flat radio-loud AGN is detected within the error box of GRO J1838–04.Fig.1(a)Fig.1(b)CGRO combined spectrum of GRO J1838-04 (VP 423)Fig.2Fig.3。
